Today the news services are remembering Alan Shepard’s flight in the Freedom 7 capsule fifty years ago, on May 5, 1961. He was the first American to fly in space and a true American hero. This seems a fitting day to share my own small personal recollection of him.
When I was in sixth grade I was fitted with a large, uncomfortable back brace that I had to wear 24 hours a day. That was the current treatment for scoliosis in 1967. It was physically uncomfortable and limited my activities, but far more burdensome to a young middle school student were the unwelcome stares and notoriety at school. My mom and dad knew I was having a hard time, but what could they do? As a parent now I can imagine how they felt.
Dad worked at NASA, and one day he was telling some of his colleagues about his concern for his son. One of those colleagues was Alan Shepard, and when he heard the story he wanted to do more than just sympathize. “Would it help if I came to visit him at school?” Dad thought that was a great idea, so they picked a day and made the arrangements. The two of them took off work one morning, drove to my school (about an hour from the Center) and visited me in my sixth grade math class. All the kids were so eager to meet a famous astronaut they practically leaped out of their seats. He shook hands, signed autographs, and answered questions from the class for about fifteen minutes. Then they left and drove back to work. I was an instant celebrity.
I never met him again after that day, but I will always be grateful. Alan Shepard was not only an American hero, he was a good and decent human being.
Thursday, May 5, 2011
Saturday, October 2, 2010
Robot Redux
After many months of inactivity, Alan and I have restarted the robot project. If you recall, we wanted to build a robot that would balance on two wheels and could be controlled by a remote. Last time we succeeded in building a robot that could travel about horizontally on three wheels (actually two wheels and a caster). But it didn't have enough power to do a wheelie. In our attempts to increase the power by increasing the voltage of the battery pack I think we managed to burn out one of the motors. It began to lose power so that the robot could not drive straight. Since one goal of the project was to see how cheaply we could build such a robot, the motors we used in Rev 1 were very cheap. This time around we decided to rebuild the original design with better motors. Below is a picture of the new Rev 2. Notice how small the motors are! They are actually more powerful than the last ones. I put a quarter on top of the right motor to give you a sense of scale:
And here is a picture of the internals showing all the breadboard wiring. In this picture, the robot is plugged into my PC via the USB port. That's how we download new software and upload performance data:
Here's a close-up of some of the breadboard wiring:
Here's a video of Rev 2 showing it being successfully driven around our kitchen right after we finished building it. We initially set the power level at only 25% of full throttle to make sure we didn't burn anything out right away, so the vehicle can move faster than this, but not a lot faster:
Even though we bought more powerful motors, this version is still nowhere near powerful enough to do a wheelie. Not even close. My goal for this round is to experiment with the balancing logic, even if the vehicle has to be manually helped to an upright position.
The big issue is still whether we can balance at all using this design. Because we were going for a cheap design, the current vehicle has no encoders to determine wheel movement and no gyro to determine rotation rate. The only sensor is an inexpensive 3 axis accelerometer (the MMA7260Q). This is a configuration that conventional wisdom says cannot be made to balance successfully. We will probably succeed only in proving the conventional wisdom, but I want to give it a go, anyway.
After these photos were taken, last week Alan wired up the accelerometer to the Arduino microprocessor board. Unfortunately, I forgot to add a line in the software to set the ADC circuit to the right mode so I burned out that part of the microprocessor. The rest of it still works, but it cannot do any analog-to-digital conversions. So I couldn't start work on the balancing software. I ordered a replacement chip which arrived this week. It's going to be a bit of a pain for Alan, because he will have to practically disassemble the thing to replace the CPU. Hopefully this weekend we can do the repair and we'll be back in business.
And here is a picture of the internals showing all the breadboard wiring. In this picture, the robot is plugged into my PC via the USB port. That's how we download new software and upload performance data:
Here's a close-up of some of the breadboard wiring:
Here's a video of Rev 2 showing it being successfully driven around our kitchen right after we finished building it. We initially set the power level at only 25% of full throttle to make sure we didn't burn anything out right away, so the vehicle can move faster than this, but not a lot faster:
Even though we bought more powerful motors, this version is still nowhere near powerful enough to do a wheelie. Not even close. My goal for this round is to experiment with the balancing logic, even if the vehicle has to be manually helped to an upright position.
The big issue is still whether we can balance at all using this design. Because we were going for a cheap design, the current vehicle has no encoders to determine wheel movement and no gyro to determine rotation rate. The only sensor is an inexpensive 3 axis accelerometer (the MMA7260Q). This is a configuration that conventional wisdom says cannot be made to balance successfully. We will probably succeed only in proving the conventional wisdom, but I want to give it a go, anyway.
After these photos were taken, last week Alan wired up the accelerometer to the Arduino microprocessor board. Unfortunately, I forgot to add a line in the software to set the ADC circuit to the right mode so I burned out that part of the microprocessor. The rest of it still works, but it cannot do any analog-to-digital conversions. So I couldn't start work on the balancing software. I ordered a replacement chip which arrived this week. It's going to be a bit of a pain for Alan, because he will have to practically disassemble the thing to replace the CPU. Hopefully this weekend we can do the repair and we'll be back in business.
Thursday, September 10, 2009
Post Mortem - Robot Rev 1
It's been a long time since I posted our progress on the self-balancing robot project. As you may have guessed, that's because it's been a long time since we worked on it. Our first attempt didn't go all that well, and we both got busy with other projects. Recently Alan and I have been wanting to jump back in and try again. This report will describe what we learned from our first attempt.
As you may recall, last time I reported that the robot was able to roll around and respond to commands from the remote control. We had two problems, however. The first was that one wheel started turning immediately after we switched on the power. It would continue to turn for a couple of seconds until the Arduino microprocessor finished booting. Our proposed fix worked well. We installed a couple of pull down resistors to hold the control line low until the computer began driving the signal low. (They were hard to add, though, because the finished breadboard wiring was very messy. That's another area we want to improve next time.)
There was still a question about how the motors were drawing any current when the USB was connected to the Arduino but the battery wasn't. After some discussions on the Arduino message board, it was decided that indeed there would be some voltage on the VIN pin if you applied power to the 5V pin. So that mystery was solved. With all of that, we now had a dandy little remote control car.
However, we were a long way from a self balancing robot. The second problem was more fundamental. The motors clearly didn't have enough speed and/or torque for the robot to do a "wheelie". If it couldn't raise itself up on two wheels to start with, there was no way it was going to balance on two wheels. We tried increasing the voltage by switching to 8 AAA batteries instead of 6 AAs. But it was nowhere near enough. On top of that, after we had made a number of attempts to fix the problem the motors began to turn even more slowly. One wheel, in particular, was turning very slowly. We checked the voltage across the motor leads and that wasn't the problem. Clearly the motor itself was failing. So the bottom line is we are going to need new, more powerful motors. The ripple effect of that change will result in several more design changes. For instance, more powerful motors will draw more current than the current H-bridge can handle. They also may not fit in the same location on the chassis. At that point we realized we were going to need a Rev 2 on the whole design.
It's not all bad news, however. Here are the things that went well:
Here is the robot all assembled. Do you like the racing stripes? We were experimenting with AAs versus AAAs, so we had rubber bands holding the battery packs on:
This is a closer shot of the front end showing the roller that serves as the front wheel (there's one on each side) as well as the IR remote control receiver and an LED to indicate system status:
And here is a closer shot of the back end. It shows the power switch as well as the USB port used to program the Arduino. The small black button is a reset button. We never needed it because the software worked great:
As you may recall, last time I reported that the robot was able to roll around and respond to commands from the remote control. We had two problems, however. The first was that one wheel started turning immediately after we switched on the power. It would continue to turn for a couple of seconds until the Arduino microprocessor finished booting. Our proposed fix worked well. We installed a couple of pull down resistors to hold the control line low until the computer began driving the signal low. (They were hard to add, though, because the finished breadboard wiring was very messy. That's another area we want to improve next time.)
There was still a question about how the motors were drawing any current when the USB was connected to the Arduino but the battery wasn't. After some discussions on the Arduino message board, it was decided that indeed there would be some voltage on the VIN pin if you applied power to the 5V pin. So that mystery was solved. With all of that, we now had a dandy little remote control car.
However, we were a long way from a self balancing robot. The second problem was more fundamental. The motors clearly didn't have enough speed and/or torque for the robot to do a "wheelie". If it couldn't raise itself up on two wheels to start with, there was no way it was going to balance on two wheels. We tried increasing the voltage by switching to 8 AAA batteries instead of 6 AAs. But it was nowhere near enough. On top of that, after we had made a number of attempts to fix the problem the motors began to turn even more slowly. One wheel, in particular, was turning very slowly. We checked the voltage across the motor leads and that wasn't the problem. Clearly the motor itself was failing. So the bottom line is we are going to need new, more powerful motors. The ripple effect of that change will result in several more design changes. For instance, more powerful motors will draw more current than the current H-bridge can handle. They also may not fit in the same location on the chassis. At that point we realized we were going to need a Rev 2 on the whole design.
It's not all bad news, however. Here are the things that went well:
- Using the DVD remote control worked great!
- Programming the Arduino was easy and fun.
- The motor control circuit worked well once we added the extra pull down resistors.
- The overall physical design worked well, including the idea of using a plastic project box as the chassis.
Here is the robot all assembled. Do you like the racing stripes? We were experimenting with AAs versus AAAs, so we had rubber bands holding the battery packs on:
This is a closer shot of the front end showing the roller that serves as the front wheel (there's one on each side) as well as the IR remote control receiver and an LED to indicate system status:
And here is a closer shot of the back end. It shows the power switch as well as the USB port used to program the Arduino. The small black button is a reset button. We never needed it because the software worked great:
Saturday, July 18, 2009
Remembering Apollo
I was raised on the space program. On my sixth birthday in 1962 my family moved from Fort Worth to Houston so my father could take a job at NASA. He was an aeronautical engineer at General Dynamics in Fort Worth when it was announced that NASA was building a new space center in Houston. He applied immediately, but it was some months before he landed a job there. At that time the Mercury program was in full swing, but Dad was hired to work on Apollo. President Kennedy had already committed the nation to go to the moon.
It took hundreds of thousands of people to make Apollo 11 possible. I am proud of my father’s role, but it is humbling to realize how many others were involved. He worked initially on the aerodynamic design of the launch escape system. That’s the small rocket that sits atop the capsule, ready to lift it quickly to safety if anything goes wrong with the booster. We still have a wind tunnel model which was used to test one of the early designs. Later he worked on the reentry aerodynamics. Coming back from the moon, the Apollo command module would reenter the Earth’s atmosphere at 25,000 mph, much faster than any previous spacecraft. This was an aerodynamic challenge of the first order. On top of that, Apollo was the first capsule designed to be a solid lifting body, so the astronauts could fly it down to the designated target area. With this ability the Apollo missions routinely landed within sight of the recovery ship.
I remember being a space junkie even before we left Fort Worth. At that time, every mission received full TV coverage from launch to splashdown. I was always glued to the tube. I watched the coverage of John Glenn’s first orbital flight, and I remember, even at five years old, the anxiety about whether his heat shield was loose during reentry. Later I followed every achievement of the Gemini program as NASA worked out the techniques that would be needed for Apollo: longer flights, larger crews, spacewalks, rendezvous and docking. Other boys collected baseball cards and memorized game stats. I became a walking encyclopedia of space trivia. I could tell you the height of the Saturn V rocket, the thrust of each stage, and every detail of the mission profile. I knew the names of most of the astronauts and could tell you which missions they had flown on. I had posters of rockets on my bedroom wall. A packet of publicity photos from NASA was one of my most treasured possessions.
The night of July 20, 1969 our whole family gathered around the TV to watch as the Eagle touched down on the moon. What an exciting time it was to be alive. Something like a quarter of the entire world population was watching with us at that same moment. The sense of wonder, pride and history was palpable. After the landing, it was to be several hours before the astronauts exited the vehicle. I remember we went outside and stood in the backyard, staring up at the moon. How strange to think that two men were there on the surface at that moment. I remember marveling at the thought that something could be in plain view, and yet so far away as to be invisible. It was hard to imagine just how far away they were.
When the moon walk started we were again glued to the television. We sat in the darkened living room of our home: my parents, my sister, my grandfather and me. I sat on the floor near the TV with my grandfather behind me on the couch. When the first ghostly images began to be transmitted we strained to make out what we were seeing. There was no doubt, though, about what was happening the moment Neil Armstrong stepped off the landing pad and onto the lunar surface. His words are burned in my memory. “I’m going to step off the LEM now. That’s one small step for a man, one giant leap for mankind.” The words seemed so appropriate.
However great the novelty and wonder of that moment was for me, I cannot fathom what it must have been like for my grandfather. Born in the Oklahoma Territory in 1892, he often told us stories of the first time he ever saw an automobile and the first time he heard about the Wright brothers at Kitty Hawk. In his lifetime mankind had gone from the first halting steps at heavier-than-air flying machines to massive rockets propelling three people to the moon, a quarter of a million miles away. As we watched the astronauts exploring the surface, every few minutes a title graphic would be displayed on the screen saying “Man on the Moon”. And every time it came on the screen my grandfather would read it out loud, in a tone of voice that spoke volumes. It was as if he couldn’t quite believe he wasn’t dreaming.
My grandfather died in 1979 and my father died in 1995. I have gazed up at the moon thousands of times in the past 40 years, and on none of those occasions was any human presence there to wonder at. Will there ever be again? Surely it will happen again someday, but my grandfather will not be here to see it, nor my father, nor perhaps will I. And now as I think back to that magical night 40 years ago it is as much with sadness as with wonder. The promise of that moment seems yet unfulfilled. I am still a space junkie. I still await eagerly each new development in the conquest of space, but I am chastened by the slow pace at which the future becomes the present. It is in this context that the accomplishments of my father’s generation seem even more extraordinary. Congratulations, Dad, to you and all your colleagues for a feat that only in hindsight, perhaps, we can fully appreciate.
It took hundreds of thousands of people to make Apollo 11 possible. I am proud of my father’s role, but it is humbling to realize how many others were involved. He worked initially on the aerodynamic design of the launch escape system. That’s the small rocket that sits atop the capsule, ready to lift it quickly to safety if anything goes wrong with the booster. We still have a wind tunnel model which was used to test one of the early designs. Later he worked on the reentry aerodynamics. Coming back from the moon, the Apollo command module would reenter the Earth’s atmosphere at 25,000 mph, much faster than any previous spacecraft. This was an aerodynamic challenge of the first order. On top of that, Apollo was the first capsule designed to be a solid lifting body, so the astronauts could fly it down to the designated target area. With this ability the Apollo missions routinely landed within sight of the recovery ship.
I remember being a space junkie even before we left Fort Worth. At that time, every mission received full TV coverage from launch to splashdown. I was always glued to the tube. I watched the coverage of John Glenn’s first orbital flight, and I remember, even at five years old, the anxiety about whether his heat shield was loose during reentry. Later I followed every achievement of the Gemini program as NASA worked out the techniques that would be needed for Apollo: longer flights, larger crews, spacewalks, rendezvous and docking. Other boys collected baseball cards and memorized game stats. I became a walking encyclopedia of space trivia. I could tell you the height of the Saturn V rocket, the thrust of each stage, and every detail of the mission profile. I knew the names of most of the astronauts and could tell you which missions they had flown on. I had posters of rockets on my bedroom wall. A packet of publicity photos from NASA was one of my most treasured possessions.
The night of July 20, 1969 our whole family gathered around the TV to watch as the Eagle touched down on the moon. What an exciting time it was to be alive. Something like a quarter of the entire world population was watching with us at that same moment. The sense of wonder, pride and history was palpable. After the landing, it was to be several hours before the astronauts exited the vehicle. I remember we went outside and stood in the backyard, staring up at the moon. How strange to think that two men were there on the surface at that moment. I remember marveling at the thought that something could be in plain view, and yet so far away as to be invisible. It was hard to imagine just how far away they were.
When the moon walk started we were again glued to the television. We sat in the darkened living room of our home: my parents, my sister, my grandfather and me. I sat on the floor near the TV with my grandfather behind me on the couch. When the first ghostly images began to be transmitted we strained to make out what we were seeing. There was no doubt, though, about what was happening the moment Neil Armstrong stepped off the landing pad and onto the lunar surface. His words are burned in my memory. “I’m going to step off the LEM now. That’s one small step for a man, one giant leap for mankind.” The words seemed so appropriate.
However great the novelty and wonder of that moment was for me, I cannot fathom what it must have been like for my grandfather. Born in the Oklahoma Territory in 1892, he often told us stories of the first time he ever saw an automobile and the first time he heard about the Wright brothers at Kitty Hawk. In his lifetime mankind had gone from the first halting steps at heavier-than-air flying machines to massive rockets propelling three people to the moon, a quarter of a million miles away. As we watched the astronauts exploring the surface, every few minutes a title graphic would be displayed on the screen saying “Man on the Moon”. And every time it came on the screen my grandfather would read it out loud, in a tone of voice that spoke volumes. It was as if he couldn’t quite believe he wasn’t dreaming.
My grandfather died in 1979 and my father died in 1995. I have gazed up at the moon thousands of times in the past 40 years, and on none of those occasions was any human presence there to wonder at. Will there ever be again? Surely it will happen again someday, but my grandfather will not be here to see it, nor my father, nor perhaps will I. And now as I think back to that magical night 40 years ago it is as much with sadness as with wonder. The promise of that moment seems yet unfulfilled. I am still a space junkie. I still await eagerly each new development in the conquest of space, but I am chastened by the slow pace at which the future becomes the present. It is in this context that the accomplishments of my father’s generation seem even more extraordinary. Congratulations, Dad, to you and all your colleagues for a feat that only in hindsight, perhaps, we can fully appreciate.
Friday, March 13, 2009
The robot is rolling (literally)
Last weekend Alan finished assembly of the self-balancing robot, Rev 1. This first version isn't supposed to balance on two wheels yet, just roll around on three wheels. It works! Well, sort of. We have some debugging to do, and some design changes are in the offing. I still have no pictures to post, for which I apologize. Alan has the camera and I haven't had a chance to upload them.
It was pretty exciting when we first powered it up. Alan plugged the Arduino into the USB cable so we could download the software, and immediately one of the two wheels started turning! It didn't stop until the control program was finished downloading and booted up.
Now, mind you, I was pretty shocked because we hadn't connected the batteries yet, and the motors are supposed to be getting their drive current from the batteries. Somehow they were getting 5V power from the USB via the Arduino. I was concerned because the Arduino can only source 40mA from each pin and if we were drawing too much current it might be damaged. We discovered, though, that if we go ahead and unplug the USB and run from the batteries, the wheel still turns a couple of seconds, but then everything seems to work after it boots. We can use the IR remote control to drive it around on the floor. Pretty cool!
So now I have several questions to investigate:
1. How can the motor draw power from the USB through the Arduino?
2. Why is it only one motor that turns at power up?
3. How can I fix it?
Here's the circuit diagram (click for a larger version):
The H-bridge is actually an SN754410 although the diagram says L293E.
I think we can probably keep the wheels from turning at power on by adding pull down resisters to the enable lines on the H-bridge. I'm guessing the enable pin voltage is basically drifting until the Arduino drives it low in the setup routine. But I really don't understand how the power is getting to the motor. I hope to get some help from the Arduino user forum.
Aside from the mystery of the spinning wheel we have one major design issue. The motors I selected have plenty of torque, but not nearly enough speed, for the robot to lift itself to a vertical position. We are looking at ways we can address this short of simply buying different motors. The first thing we want to try is to get a little more speed out of the existing motors by upping the voltage. We intend to replace the six AA NiMH batteries with eight AAA NiMH batteries. This also makes the robot lighter. Eight cells will give us a nominal 9.6V, which after the 1.4V drop in the H-bridge becomes 8.2V. This is substantially higher than the net 5.8V we have now. The motors are supposedly rated at 12V, although I'm pretty sure they would overheat quickly if driven continuously at this voltage. But it will only take a fraction of a second for it to raise itself to vertical.
We'll try the pull down resisters this weekend, but we're waiting for parts to convert from AA to AAA batteries.
It was pretty exciting when we first powered it up. Alan plugged the Arduino into the USB cable so we could download the software, and immediately one of the two wheels started turning! It didn't stop until the control program was finished downloading and booted up.
Now, mind you, I was pretty shocked because we hadn't connected the batteries yet, and the motors are supposed to be getting their drive current from the batteries. Somehow they were getting 5V power from the USB via the Arduino. I was concerned because the Arduino can only source 40mA from each pin and if we were drawing too much current it might be damaged. We discovered, though, that if we go ahead and unplug the USB and run from the batteries, the wheel still turns a couple of seconds, but then everything seems to work after it boots. We can use the IR remote control to drive it around on the floor. Pretty cool!
So now I have several questions to investigate:
1. How can the motor draw power from the USB through the Arduino?
2. Why is it only one motor that turns at power up?
3. How can I fix it?
Here's the circuit diagram (click for a larger version):
The H-bridge is actually an SN754410 although the diagram says L293E.
I think we can probably keep the wheels from turning at power on by adding pull down resisters to the enable lines on the H-bridge. I'm guessing the enable pin voltage is basically drifting until the Arduino drives it low in the setup routine. But I really don't understand how the power is getting to the motor. I hope to get some help from the Arduino user forum.
Aside from the mystery of the spinning wheel we have one major design issue. The motors I selected have plenty of torque, but not nearly enough speed, for the robot to lift itself to a vertical position. We are looking at ways we can address this short of simply buying different motors. The first thing we want to try is to get a little more speed out of the existing motors by upping the voltage. We intend to replace the six AA NiMH batteries with eight AAA NiMH batteries. This also makes the robot lighter. Eight cells will give us a nominal 9.6V, which after the 1.4V drop in the H-bridge becomes 8.2V. This is substantially higher than the net 5.8V we have now. The motors are supposedly rated at 12V, although I'm pretty sure they would overheat quickly if driven continuously at this voltage. But it will only take a fraction of a second for it to raise itself to vertical.
We'll try the pull down resisters this weekend, but we're waiting for parts to convert from AA to AAA batteries.
Saturday, March 7, 2009
Assembling the self-balancing robot
Well, Alan and I both got tired of waiting for me to finish the modeling and simulation I wanted to do, so I threw caution to the winds and ordered all the parts to build my draft design of the self-balancing robot. There is still the chance that the motors may not have sufficient speed or torque, or may have too much backlash to work well. Also, I went ahead and ordered the cheapest accelerometer available at Sparkfun, (the MMA7260) reasoning that we’d have a go at making it work first. We can always switch to a different sensor or add additional sensors if we have to.
So now Alan is spending this weekend assembling the robot. I have written Rev 1 of the software, and soon we will be putting them together for our first trial runs. For Rev 1, we are not going to try to balance. We have put a small caster on the front of the box so it can drive around as a typical three wheel vehicle. Once we debug the motor control and get a feel for the speed and torque we have available, I will be back trying to develop the balancing control software.
In the meantime I have been testing the accelerometer and, true to everyone’s comments, the measurements are alarmingly noisy. Of course the signal can be filtered, but that introduces delay in the measurements. Whether we can get this to work or not will depend, I think, in large measure on how rapidly the main control loop has to run to keep the robot well balanced. The MMA7260 has a refresh frequency on the X and Y axes of 350 Hz. So you get a new reading about every 3 milliseconds. If we can afford to make corrections to the motor inputs only every 30 ms, say, then we can take the average of the last 10 readings to smooth out the acceleration data. If this turns out to be too slow, the robot will be unsteady and we’ll see lots of random jittering back and forth. On the other hand, noisy acceleration data will cause jittering, too. So we must find the best tradeoff. But I note with some unease that there is still significant noise in the data even after averaging over 10 readings. And, of course, the more heavily the signal is filtered the more delay it creates before the control algorithm will see the beginning of an excursion. This can cause oscillation or even a loss of control. I’ll try to post some specific data at some point so you can see what I’m talking about.
Alan and I have had a number of discussions about whether we needed wheel encoders so we can get feedback on the distance traveled by the robot. We are going to build it first without encoders. This, too, is heresy among self-balancing robot builders (uh, I mean builders of self-balancing robots). Partly the standard wisdom arises from how people conceptualize the inverted pendulum problem. The natural way to think about it is that I measure how far the pendulum has departed from vertical, then I move the base that far to get it back under the center of gravity. But of course, for balancing, you get all the position feedback you need from the pendulum itself. However, the more fundamental reason people assume you need encoders is that the accelerometers can’t tell you whether you’re moving, only whether you’re accelerating. There is no way to correct the inevitable error you get from computing velocity by integrating acceleration. So when the robot is commanded to stand still it has no way to be sure it really is, and when it is commanded to move at a certain speed it has no way to determine that either.
My solution to this problem is partly electrical and partly anthropic, if you will. One piece of data we do have is the average current being supplied to the two motors in the forward and backward directions. To some approximation, you expect that if the robot is sitting still on a level surface the average power in each direction will be equal. Of course, there are natural physical irregularities so that is not exactly correct. But I believe we can add a bias term to that balance and treat it as a tuning parameter. We can adjust it to correct for (almost all of?) the drift. That’s the electrical part. The other part is based on the idea that this is not actually an autonomous vehicle. It is just a fancy remote control car. So the human in the loop will be controlling the position and speed to their satisfaction. Of course, this approach does have another downside: the robot will not be able to maintain position on a slope by itself. It will slowly roll downhill. But I think this will seem like a very natural behavior to the human operator, and of course they will compensate.
The only real question, which we’ll find out by building the thing, is how well the drift can be corrected with a constant bias, that is, how stable the bias is. Just in case, though, I bought some optical encoders and eventually I expect we’ll get around to fooling with them – if not on this vehicle, then on the next.
We’ll have another report, with pictures, when Alan finishes construction. I can’t wait!
So now Alan is spending this weekend assembling the robot. I have written Rev 1 of the software, and soon we will be putting them together for our first trial runs. For Rev 1, we are not going to try to balance. We have put a small caster on the front of the box so it can drive around as a typical three wheel vehicle. Once we debug the motor control and get a feel for the speed and torque we have available, I will be back trying to develop the balancing control software.
In the meantime I have been testing the accelerometer and, true to everyone’s comments, the measurements are alarmingly noisy. Of course the signal can be filtered, but that introduces delay in the measurements. Whether we can get this to work or not will depend, I think, in large measure on how rapidly the main control loop has to run to keep the robot well balanced. The MMA7260 has a refresh frequency on the X and Y axes of 350 Hz. So you get a new reading about every 3 milliseconds. If we can afford to make corrections to the motor inputs only every 30 ms, say, then we can take the average of the last 10 readings to smooth out the acceleration data. If this turns out to be too slow, the robot will be unsteady and we’ll see lots of random jittering back and forth. On the other hand, noisy acceleration data will cause jittering, too. So we must find the best tradeoff. But I note with some unease that there is still significant noise in the data even after averaging over 10 readings. And, of course, the more heavily the signal is filtered the more delay it creates before the control algorithm will see the beginning of an excursion. This can cause oscillation or even a loss of control. I’ll try to post some specific data at some point so you can see what I’m talking about.
Alan and I have had a number of discussions about whether we needed wheel encoders so we can get feedback on the distance traveled by the robot. We are going to build it first without encoders. This, too, is heresy among self-balancing robot builders (uh, I mean builders of self-balancing robots). Partly the standard wisdom arises from how people conceptualize the inverted pendulum problem. The natural way to think about it is that I measure how far the pendulum has departed from vertical, then I move the base that far to get it back under the center of gravity. But of course, for balancing, you get all the position feedback you need from the pendulum itself. However, the more fundamental reason people assume you need encoders is that the accelerometers can’t tell you whether you’re moving, only whether you’re accelerating. There is no way to correct the inevitable error you get from computing velocity by integrating acceleration. So when the robot is commanded to stand still it has no way to be sure it really is, and when it is commanded to move at a certain speed it has no way to determine that either.
My solution to this problem is partly electrical and partly anthropic, if you will. One piece of data we do have is the average current being supplied to the two motors in the forward and backward directions. To some approximation, you expect that if the robot is sitting still on a level surface the average power in each direction will be equal. Of course, there are natural physical irregularities so that is not exactly correct. But I believe we can add a bias term to that balance and treat it as a tuning parameter. We can adjust it to correct for (almost all of?) the drift. That’s the electrical part. The other part is based on the idea that this is not actually an autonomous vehicle. It is just a fancy remote control car. So the human in the loop will be controlling the position and speed to their satisfaction. Of course, this approach does have another downside: the robot will not be able to maintain position on a slope by itself. It will slowly roll downhill. But I think this will seem like a very natural behavior to the human operator, and of course they will compensate.
The only real question, which we’ll find out by building the thing, is how well the drift can be corrected with a constant bias, that is, how stable the bias is. Just in case, though, I bought some optical encoders and eventually I expect we’ll get around to fooling with them – if not on this vehicle, then on the next.
We’ll have another report, with pictures, when Alan finishes construction. I can’t wait!
Sunday, February 15, 2009
IR Receiver Circuit
The IR receiver from Mouser Electronics arrived this week. It came amazingly quickly. I ordered it late Saturday night. It shipped on Monday and was delivered on Tuesday. The chip we are using is the Vishay TSOP4840, which is only $1.10 quantity one at Mouser. Alan built the test circuit to connect the IR receiver to the Arduino microcontroller board using a breadboard:
Here's a closeup of the IR receiver and the remote control.
Here is the schematic for the test circuit:
The Sony remote control modulates the IR carrier wave at 40 kHz. (Other manufacturers use other frequencies. 38 kHz is common.) This carrier wave is turned on and off to create a stream of pulses that carry the data. The SIRC protocol uses pulse width modulation. A command begins with a start bit that is 2400 µs wide. It is followed by twelve data bits, separated by 600 µs gaps. A logical one bit is represented by a 1200 µs pulse and a logical zero is represented by a 600 µs pulse. The TSOP4840 demodulates the IR carrier wave and presents a logical signal on the output pin that is low when the IR carrier is present and high when it is absent (i.e., active low). The output is connected to a digital I/O pin on the Arduino. D2 is chosen because it is one of two pins that can generate hardware interrupts when the value changes. Thus it is only necessary for the software to time the intervals between the interrupts to decode the signal. I set to work on the software and we got the whole thing working without too much trouble.
It’s amazing how sensitive the receiver is. You can be across the room and point the remote at the opposite wall and it will still pick up the reflected signal. This will work great for the robot. You will have to be standing behind it, but the direction and distance are not critical.
The nice thing about using a standard IR remote control is how many different buttons it has. Once you’ve got the software in place to decode the commands you can define as many commands for the robot as you would like. We expect to have at least seven: stand up, lie down, go forward, go back, turn left, turn right and stop. One interesting issue is that the remote control repeats the command every 45 ms for as long as you hold down the button. It turns out to be essentially impossible to tap a button quickly enough to send only one command. Two or three is more typical. The robot control software will have to determine when a command was doubled or tripled through an auto-repeat and compensate.
Next up is to go back and finish the physics model and the simulation. I set it aside last week when I got stuck, but I’ve asked my brother-in-law, whose degree is in physics, to help me. So it’s back to school for me this week!
Here's a closeup of the IR receiver and the remote control.
Here is the schematic for the test circuit:
The Sony remote control modulates the IR carrier wave at 40 kHz. (Other manufacturers use other frequencies. 38 kHz is common.) This carrier wave is turned on and off to create a stream of pulses that carry the data. The SIRC protocol uses pulse width modulation. A command begins with a start bit that is 2400 µs wide. It is followed by twelve data bits, separated by 600 µs gaps. A logical one bit is represented by a 1200 µs pulse and a logical zero is represented by a 600 µs pulse. The TSOP4840 demodulates the IR carrier wave and presents a logical signal on the output pin that is low when the IR carrier is present and high when it is absent (i.e., active low). The output is connected to a digital I/O pin on the Arduino. D2 is chosen because it is one of two pins that can generate hardware interrupts when the value changes. Thus it is only necessary for the software to time the intervals between the interrupts to decode the signal. I set to work on the software and we got the whole thing working without too much trouble.It’s amazing how sensitive the receiver is. You can be across the room and point the remote at the opposite wall and it will still pick up the reflected signal. This will work great for the robot. You will have to be standing behind it, but the direction and distance are not critical.
The nice thing about using a standard IR remote control is how many different buttons it has. Once you’ve got the software in place to decode the commands you can define as many commands for the robot as you would like. We expect to have at least seven: stand up, lie down, go forward, go back, turn left, turn right and stop. One interesting issue is that the remote control repeats the command every 45 ms for as long as you hold down the button. It turns out to be essentially impossible to tap a button quickly enough to send only one command. Two or three is more typical. The robot control software will have to determine when a command was doubled or tripled through an auto-repeat and compensate.
Next up is to go back and finish the physics model and the simulation. I set it aside last week when I got stuck, but I’ve asked my brother-in-law, whose degree is in physics, to help me. So it’s back to school for me this week!
Sunday, February 8, 2009
Bubbling to the Surface
It is time to confess a new obsession. Like most obsessions it begins by contagion. I caught this one from my son Alan. We are going to build a robot. Well, not exactly. We want to build a remote-controlled self-balancing two-wheeled vehicle. Think Segway, only very small. And hyphenated. It's not an original idea, of course. Besides Segway, lots of amateurs have built such things. To the extent that we have a new twist on the concept, I am interested in seeing how cheaply we can do this. I think we might be able to do it for under $100. Most such projects seem to be at least $200-300. Cheap also means small (smaller motors cost less) so ours will be smaller than the others.
I am not a hardware guy. I'm like the punchline of the old programmer joke: How many programmers does it take to change a light bulb? None. "Hey, man, that's hardware!" Fortunately for our collaboration, Alan is much more of a hands-on kind of guy. In fact, I think we make a great team. I can't wait to take a crack at the control algorithm and he's itching to do all the soldering and wiring and assembly.
Here's how we got into this. For several months Alan has been surfing websites for DIY electronics projects. For Christmas he asked for an Arduino, an inexpensive microcontroller board based on an open source hardware design. Until Alan asked for this I never knew such things existed. Then I started doing a little investigation, and the obsession began. It is such a great time to get involved in DIY electronics. I had no idea there were so many sophisticated components available so cheaply, like three axis accelerometers in an IC chip that costs only $10 or $20 dollars. And the programming reminds me of the old days programming for my first home computer: an Apple II. Low level coding on an 8 bit micro and direct manipulation of the hardware. Wonderful! (That's geek nostalgia, friend.)
I see this effort as a sequence of sub-projects:
1. Do a preliminary hardware design
2. Develop a physics model for simulating the vehicle
3. Use the simulation to develop and test the control algorithm
4. Develop an IR remote control decoder to control the vehicle
5. Build rev 1 of the vehicle as a three-wheeled scooter
6. Debug and tune the balancing on two wheels
I've already roughed out the hardware design with an eye toward selecting and pricing components online. The only piece I haven't figured out yet is how to cheaply measure distance traveled. The obvious answer is an optical wheel encoder, which you can buy as a kit for DIY robotics. But if we're going to keep the hardware budget under $100, we'll probably need to do something cheap and homebrew.
Most folks who have built one of these things uses both a gyro and an accelerometer. The gyro gives a stable rate signal that you can integrate to get angular position, but it is subject to a lot of drift. The accelerometer gives a very noisy signal, but it can be filtered and used to correct the gyro drift. Again, to save money I'd like to try to make our vehicle work with just an accelerometer. I want to use the simulation to see how much noise I can tolerate, and get a sense for the bandwidth and resolution I need on the accelerometer. This past week I've been working on the physics model. Boy, my freshman physics is rusty! I suppose since it's been nearly 35 years that's not too surprising. I've been beating my head against it for days.
At the same time I've been reading up on IR remote controls. We want to use a Sony remote from our DVD player to control the vehicle. You can buy an IR receiver for $1 or $2 but I'll need to study up the SIRC protocol and program the Arduino to decode the signal. Last night I ordered the part and started looking into the programming.
Well, that's where we are so far. I have in mind to post sporadic progress reports here as we move forward. If we ever get it working I'll post a few video clips, too. Now that I've posted this entry the pressure is on to actually do something!
I am not a hardware guy. I'm like the punchline of the old programmer joke: How many programmers does it take to change a light bulb? None. "Hey, man, that's hardware!" Fortunately for our collaboration, Alan is much more of a hands-on kind of guy. In fact, I think we make a great team. I can't wait to take a crack at the control algorithm and he's itching to do all the soldering and wiring and assembly.
Here's how we got into this. For several months Alan has been surfing websites for DIY electronics projects. For Christmas he asked for an Arduino, an inexpensive microcontroller board based on an open source hardware design. Until Alan asked for this I never knew such things existed. Then I started doing a little investigation, and the obsession began. It is such a great time to get involved in DIY electronics. I had no idea there were so many sophisticated components available so cheaply, like three axis accelerometers in an IC chip that costs only $10 or $20 dollars. And the programming reminds me of the old days programming for my first home computer: an Apple II. Low level coding on an 8 bit micro and direct manipulation of the hardware. Wonderful! (That's geek nostalgia, friend.)
I see this effort as a sequence of sub-projects:
1. Do a preliminary hardware design
2. Develop a physics model for simulating the vehicle
3. Use the simulation to develop and test the control algorithm
4. Develop an IR remote control decoder to control the vehicle
5. Build rev 1 of the vehicle as a three-wheeled scooter
6. Debug and tune the balancing on two wheels
I've already roughed out the hardware design with an eye toward selecting and pricing components online. The only piece I haven't figured out yet is how to cheaply measure distance traveled. The obvious answer is an optical wheel encoder, which you can buy as a kit for DIY robotics. But if we're going to keep the hardware budget under $100, we'll probably need to do something cheap and homebrew.
Most folks who have built one of these things uses both a gyro and an accelerometer. The gyro gives a stable rate signal that you can integrate to get angular position, but it is subject to a lot of drift. The accelerometer gives a very noisy signal, but it can be filtered and used to correct the gyro drift. Again, to save money I'd like to try to make our vehicle work with just an accelerometer. I want to use the simulation to see how much noise I can tolerate, and get a sense for the bandwidth and resolution I need on the accelerometer. This past week I've been working on the physics model. Boy, my freshman physics is rusty! I suppose since it's been nearly 35 years that's not too surprising. I've been beating my head against it for days.
At the same time I've been reading up on IR remote controls. We want to use a Sony remote from our DVD player to control the vehicle. You can buy an IR receiver for $1 or $2 but I'll need to study up the SIRC protocol and program the Arduino to decode the signal. Last night I ordered the part and started looking into the programming.
Well, that's where we are so far. I have in mind to post sporadic progress reports here as we move forward. If we ever get it working I'll post a few video clips, too. Now that I've posted this entry the pressure is on to actually do something!
Saturday, January 17, 2009
Word of the Day - Snarge
Lately the airwaves have been filled with news about the US Airways pilot who made the miraculous emergency landing on the Hudson river after hitting a flock of geese. We've all been amazed by the stories and pictures. It's been educational, too. Many people didn't realize that a few birds can bring down a big jet. That angle of the story leads to today's word of the day:
Snarge - what remains of a bird after it strikes a plane.
Birds are actually a significant hazard in aviation and crashes of this sort occur regularly. So regularly that there is a lab at the Smithsonian Institution for identifying the bird species from whatever goo and feathers is left. This information helps experts understand how to improve the safety of airplanes and airports. And who heads the Feather Identification Lab at the Smithsonian? Her name is Carla Dove! Gotta love that.
Snarge - what remains of a bird after it strikes a plane.
Birds are actually a significant hazard in aviation and crashes of this sort occur regularly. So regularly that there is a lab at the Smithsonian Institution for identifying the bird species from whatever goo and feathers is left. This information helps experts understand how to improve the safety of airplanes and airports. And who heads the Feather Identification Lab at the Smithsonian? Her name is Carla Dove! Gotta love that.
Monday, December 22, 2008
Glow in the Dark Toys
Back when I was in college the only thing you were likely to find in a dorm room that glowed in the dark was a black light poster. Or a doobie. Now here's a guy named Andrew Seltzman who graduated this year from Georgia Tech and what's he got in his dorm room? A fusion reactor! Yes, that's right. He built a fusion reactor in his dorm room. Here's a picture of the deuterium ion injector parts all laid out on his bed:
And here's the assembled machine:
He tried a couple of test runs with no fuel just to prove it was generating a plasma. But before he actually fired up the fusion reaction he moved it to a lab in the nuclear engineering building. Here's a picture of the deuterium plasma of the reactor in actual operation, generating neutrons:
This type of device is called a fusor and it is simple enough that several dozen very accomplished amateurs have been able to build one. Andrew Seltzman actually built his first fusor in high school. His new one is pretty sophisticated. It has a liquid cooled grid electrode and an ion injector. My hat is off to him and I hope he has a brilliant career as a physicist.
By the way, you'll never guess who invented the fusor. His name was Philo T. Farnsworth. You've probably never of him but I'm sure you've heard of something else he invented: television. Fusors are used as neutron generators but are hopelessly inefficient for power generation. The amount of power they consume is way more than they could ever generate. However, the fusor has a cousin that I've written about before that is more promising: the Polywell. I'm fascinated by this line of research and I hope it pans out. In the meantime, the pictures are pretty cool!
And here's the assembled machine:
He tried a couple of test runs with no fuel just to prove it was generating a plasma. But before he actually fired up the fusion reaction he moved it to a lab in the nuclear engineering building. Here's a picture of the deuterium plasma of the reactor in actual operation, generating neutrons:
This type of device is called a fusor and it is simple enough that several dozen very accomplished amateurs have been able to build one. Andrew Seltzman actually built his first fusor in high school. His new one is pretty sophisticated. It has a liquid cooled grid electrode and an ion injector. My hat is off to him and I hope he has a brilliant career as a physicist.
By the way, you'll never guess who invented the fusor. His name was Philo T. Farnsworth. You've probably never of him but I'm sure you've heard of something else he invented: television. Fusors are used as neutron generators but are hopelessly inefficient for power generation. The amount of power they consume is way more than they could ever generate. However, the fusor has a cousin that I've written about before that is more promising: the Polywell. I'm fascinated by this line of research and I hope it pans out. In the meantime, the pictures are pretty cool!
Tuesday, November 25, 2008
Back to the Hill Country
This past weekend my lovely bride and I enjoyed another getaway to the Texas Hill Country for a belated celebration of our 30th wedding anniversary. It was a great trip. We toured the only commercial olive grove in Texas. They do samplings of their olive oil just like a winery. We toured a couple of wineries, too, and had dinner at one in their excellent Italian restaurant.
While we were there we stayed at a wonderful B&B in the Canyon Lake area called Biscuit Hill Bed & Breakfast. The food was delicious and the owners were very friendly and hospitable. Most of the weekend was cloudy, but on the last day we were treated to beautiful blue skies that showcased the natural beauty of the area. Here's a picture of the B&B and another picture of the view from our private second story deck:
Canyon Lake was formed by damming the Guadalupe River in central Texas. The rocky limestone terrain ensures that the water is a beautiful blue color, unlike the muddy, sediment-filled lakes of East Texas. You can see the lake in the distance in the picture above. A closer shot is shown below, along with a shot of the earthen dam:
Behind the dam is a spillway and a small hydroelectric plant:
Just across the bank from the spillway I took this picture of a small tree clinging to the last leaves of fall, brilliantly lit by the midday sun. The yellow leaves were positively luminous. I wish my cheap digital camera did the scene justice:
The water from the spillway feeds the lower Guadalupe River. It is known around Texas as a beautiful place for tubing, white-water rafting, and fly fishing. Here is the view just downstream:
It was a great weekend to get away and enjoy a change of pace. I am so blessed to have such a wonderful wife, and doubly blessed because she has put up with me for the past thirty years. Even better, she shows no signs of kicking me out anytime soon!
While we were there we stayed at a wonderful B&B in the Canyon Lake area called Biscuit Hill Bed & Breakfast. The food was delicious and the owners were very friendly and hospitable. Most of the weekend was cloudy, but on the last day we were treated to beautiful blue skies that showcased the natural beauty of the area. Here's a picture of the B&B and another picture of the view from our private second story deck:
Canyon Lake was formed by damming the Guadalupe River in central Texas. The rocky limestone terrain ensures that the water is a beautiful blue color, unlike the muddy, sediment-filled lakes of East Texas. You can see the lake in the distance in the picture above. A closer shot is shown below, along with a shot of the earthen dam:
Behind the dam is a spillway and a small hydroelectric plant:
Just across the bank from the spillway I took this picture of a small tree clinging to the last leaves of fall, brilliantly lit by the midday sun. The yellow leaves were positively luminous. I wish my cheap digital camera did the scene justice:
The water from the spillway feeds the lower Guadalupe River. It is known around Texas as a beautiful place for tubing, white-water rafting, and fly fishing. Here is the view just downstream:
It was a great weekend to get away and enjoy a change of pace. I am so blessed to have such a wonderful wife, and doubly blessed because she has put up with me for the past thirty years. Even better, she shows no signs of kicking me out anytime soon!
Friday, October 24, 2008
If Armadillos Could Fly
Well, they can!!
I would like to join with space enthusiasts everywhere to give my most enthusiastic congratulations to Armadillo Aerospace for winning Level 1 of the Northrop Grumman Lunar Lander Challenge today. To win Level 1, you have to launch a rocket from one pad, fly to 50 meters altitude, hover for 90 seconds, and land at another pad 100 meters away. Then you have to make a similar flight with the same vehicle back to the first pad. Sound simple? It's not! It's taken them several years to win, and no one else has even come close. Level 2 is harder still. You have to stay airborne for 180 seconds on each flight, and the second landing pad has boulders and craters just like the lunar surface. Armadillo will try to win Level 2 tomorrow.
Over the past few years I have often referred to Armadillo as the poster boys of amateur rocketry. I always meant that in the best possible way. Founded by John Carmack, creator of Doom and other famous video games, they started building rockets in a garage on the weekends eight years ago. Starting with ungainly little spider-like vehicles, look at what they have achieved! They have built engines for NASA and the Air Force. This year they won the contract to provide the rocket engines for the Rocket Racing League's airplane fleet. And not only did they win the NGLLC today, but Armadillo and Rocket Racing League announced they will form a joint venture with the state of New Mexico to build and fly passenger-carrying suborbital rocket vehicles over the next couple of years. Armadillo will be building the hardware.
So Armadillo Aerospace is all grown up now. They are poster boys no more. To John Carmack & co. I say: You guys are top flight professionals in my book from now on! Congratulations on your Rocket Racer contract, on your new joint venture announced today, and again on your level 1 win. Here’s hoping for a level 2 win tomorrow!
Sunday, September 28, 2008
Falcon 1 in Orbit!
They finally did it! Falcon 1 is in orbit. As Elon Musk said to his employees, "The fourth time's a charm." Launch was at 4:16 pm PDT and second stage cut off occurred ten minutes later. The picture perfect launch and flight to orbit was webcast live. SpaceX has now become the first company to design, build and launch a privately funded space vehicle into orbit. According to Musk, in the past that's been a "country thing" and only a few countries in the world have achieved it. Now a private company has. Congratulations!
Sunday, September 21, 2008
Back in the 21st Century
We finally got our electrical power restored yesterday afternoon. That's just slightly over a week living a lifestyle from the last century. Evenings were impacted the most. It was incredibly interesting to see how the family dynamic changed. We would sit around by candlelight talking or reading. I started teaching my younger son guitar lessons. Everyone went to bed early. It made me realize how much less stimulation people received a hundred years ago. For the twenty-first century family it was boring! No phone, no TV, no computer, no Internet, no X-Box, no stereo, and no iPod (because you can't recharge it). Even with a dozen candles burning, the light was so dim I would start to fall asleep at 8:30 pm. It was an experience we will remember for a long time. I know there are hundreds of thousands of Houstonians still in the middle of that experience. Three cheers for the hardworking linemen who are restoring power to two million people, one circuit at a time.
BTW, on Saturday, before the power came back on, we decided to pick up a few MREs with our FEMA ice. Our stock of salvaged food in our ice chest was just about gone, and we had never tried them before. Actually, we had never even seen an MRE before and we were all curious to try it out. The food is better than I would have expected, although naturally some things are better than others. The little chemical device to heat the food is ingenious. I can see how the soldiers would get very, very tired of it, though. In college we had very good dorm food, too, but about the third time through the two week menu rotation it started to get pretty old. Three more cheers for our hardy soldiers, for whom bad food is the least of their hardships.
BTW, on Saturday, before the power came back on, we decided to pick up a few MREs with our FEMA ice. Our stock of salvaged food in our ice chest was just about gone, and we had never tried them before. Actually, we had never even seen an MRE before and we were all curious to try it out. The food is better than I would have expected, although naturally some things are better than others. The little chemical device to heat the food is ingenious. I can see how the soldiers would get very, very tired of it, though. In college we had very good dorm food, too, but about the third time through the two week menu rotation it started to get pretty old. Three more cheers for our hardy soldiers, for whom bad food is the least of their hardships.
Thursday, September 18, 2008
Two Bags of Ice
Two bags of ice: that's what we get every day at the local FEMA POD (point of distribution) in our affluent Houston suburb. Yes, we're still without power in our area, along with thousands of other people. CenterPoint Energy has 2.3 million customers in the Houston area. After Ike moved through on Saturday 2.1 million of them had no power. As of this morning (Thursday) 1.3 million of us still don't have power. So we're in good company here. Besides no power, our phones are out too. Fortunately, though, the water and natural gas services were never interrupted in our area. So with a little ice we can keep our food from spoiling and cook it on the gas stove. We're in pretty good shape, considering what so many others are enduring. Our area saw sustained winds of only about 65 mph, with gusts up to 90 mph. There were lots of downed trees and fences in the area, but the only damage to our property was losing a couple of large limbs from the pecan tree in our back yard. I'm even back at work. Our office building reopened Tuesday, and that's where I'm posting this message.
The first few days it was pretty hard to find the basic necessities, which in post-Ike Houston consist of ice, bottled water, gasoline and food (pretty much in that order). The lines were hours long anywhere a store was open that had any of these things in stock. So the FEMA POD that showed up on Tuesday was welcome. But more than that, it was something of a milestone in my 52 years of life. When my wife told me after work that our sons had collected two free bags of ice from FEMA, I laughed out loud. As far as I can recall, that's the first government assistance I've ever received in nearly 35 years as a taxpayer. Oh, I benefit from basic services like police, fire, roads, courts and defense. But in terms of targeted assistance, those two $1.79 bags of ice were a first. I started to wonder how many days it would take to get back all the tax money I've paid over the years, but then I realized I pay much more than $3.58 a day in federal taxes. So the net benefit is still negative. Of course, in 13 years I'm gonna be on Medicare. Then all you sorry Gen-Xers will be paying through the nose!!
The first few days it was pretty hard to find the basic necessities, which in post-Ike Houston consist of ice, bottled water, gasoline and food (pretty much in that order). The lines were hours long anywhere a store was open that had any of these things in stock. So the FEMA POD that showed up on Tuesday was welcome. But more than that, it was something of a milestone in my 52 years of life. When my wife told me after work that our sons had collected two free bags of ice from FEMA, I laughed out loud. As far as I can recall, that's the first government assistance I've ever received in nearly 35 years as a taxpayer. Oh, I benefit from basic services like police, fire, roads, courts and defense. But in terms of targeted assistance, those two $1.79 bags of ice were a first. I started to wonder how many days it would take to get back all the tax money I've paid over the years, but then I realized I pay much more than $3.58 a day in federal taxes. So the net benefit is still negative. Of course, in 13 years I'm gonna be on Medicare. Then all you sorry Gen-Xers will be paying through the nose!!
Friday, September 12, 2008
Hurricane Preparations
A viewer named Bill in Santa Fe, TX sent this picture to KTRK, the local ABC affiliate. He called it Hurricane Car Safety. Yes, all the old hands around here know just how to get ready for a hurricane.
The heavy storm bands are just starting to come ashore in Galveston. We're getting gusts up to 40 and the power is beginning to blink on and off. This is probably my last post for the night.
I was going to title this post "Preparation H" but I chickened out...
Ike Takes Aim
Here in Houston we have Hurricane Ike bearing down on us and it looks like Friday night could be a pretty wild ride. When I was younger I used to secretly hope each year that a hurricane would hit us just for the excitement. Now that I’m a sober, settled, middle-aged father and home owner I’m just praying the whole thing fizzles. At this point it doesn't look like that's going to happen. I’ll try to give you a report this weekend if the power comes back on quickly.
[Update Sept 12, 10:45 am]
It's still 16-18 hours before landfall. It's just a breezy day so far here in our neighborhood on the west side of Houston, about 60 miles inland. Our preparations are complete and we're glued to the tube watching the continuous local coverage. The storm has hardly strengthened overnight, which is good news, but the size of this thing makes it really scary. The storm surge began in the early morning hours and many coastal neighborhoods are already flooded. Long time residents are amazed that the flooding is already so bad this long before landfall, before even a drop of rain has fallen. The houses we are seeing right now on TV as the helicopters fly overhead will probably not even be there tomorrow if Ike hits where it is predicted.
[Update Sept 12, 10:45 am]
It's still 16-18 hours before landfall. It's just a breezy day so far here in our neighborhood on the west side of Houston, about 60 miles inland. Our preparations are complete and we're glued to the tube watching the continuous local coverage. The storm has hardly strengthened overnight, which is good news, but the size of this thing makes it really scary. The storm surge began in the early morning hours and many coastal neighborhoods are already flooded. Long time residents are amazed that the flooding is already so bad this long before landfall, before even a drop of rain has fallen. The houses we are seeing right now on TV as the helicopters fly overhead will probably not even be there tomorrow if Ike hits where it is predicted.
Saturday, August 9, 2008
SpaceX Blame Game
On August 6, Elon Musk released an explanation for last week's Falcon 1 launch failure. Evidently, the two stages did separate, but they reimpacted seconds later. When the second stage engine fired it damaged both stages, sending them tumbling to their destruction.
This flight of the Falcon 1 was the first flight test of the new Merlin 1C engine. The previous version of the engine was ablatively cooled, meaning that the rocket nozzle is lined with a material that slowly burns away, thus protecting the metal nozzle. The new version is regeneratively cooled, which means that the kerosene fuel circulates through channels in the nozzle to cool it before it gets injected into the engine. With regenerative cooling, when the fuel flow is cut off there is more residual fuel in the engine, so it takes longer for the thrust to drop off to zero. Evidently, SpaceX engineers did not take this into account by lengthening the time between engine cutoff and stage separation. The small amount of remaining thrust enabled the first stage to catch up with the second stage again instead of being out of the way when it ignited. You can see the whole thing in the video posted by SpaceX.
I mentioned last week that the various newspace bloggers and industry pundits have been engaged in an orgy of speculation and criticism. The new information from Musk didn't really quiet the crowd. It just shifted the focus to a discussion of whether this problem could have been foreseen and avoided. At some level that's no doubt true. Before the release of the video, some commentators had leapt immediately to the correct explanation, knowing nothing more than that there had been a "stage separation failure" and that this was the first flight with a regeneratively cooled engine. Much has been made, as well, about the fact that SpaceX has experienced three consecutive failures.
Why did they fail? There has a lot of loose criticism of SpaceX implying they are are a bunch of amateurs. That's not consistent with what I've heard about their organization and I think it is very unfair. I don't mean to say that every mistake they have made is unavoidable. But I also think there's another reason why one would expect them to have more failures than the established aerospace companies. Their whole strategy is to find ways to simplify and automate the process of designing, building, testing and launching rockets. They are being innovative and taking risks by seeing which parts can be cheaper, which processes you can do without, which jobs you can automate, etc. If you're really going to find the floor on costs you have to go a little too low and then selectively restore some extra checks and redundancies as needed to get acceptable reliability. New, privately held, self funded companies can afford to take these kinds of risks more than established organizations.
Entrepeneurship drives progress in unique ways, and we are fortunate that we still have an entrepeneurial culture in this country. Most fail, but some succeed, and they do it by exceeding what earlier suppliers were able to achieve. If Musk is wrong, and there are no economies to be found in the way rockets are currently designed, built, tested and launched then he will fail. He might fail anyway if he makes too many mistakes. But I think his basic premise is sound and I suspect he will, in the end, succeed.
This flight of the Falcon 1 was the first flight test of the new Merlin 1C engine. The previous version of the engine was ablatively cooled, meaning that the rocket nozzle is lined with a material that slowly burns away, thus protecting the metal nozzle. The new version is regeneratively cooled, which means that the kerosene fuel circulates through channels in the nozzle to cool it before it gets injected into the engine. With regenerative cooling, when the fuel flow is cut off there is more residual fuel in the engine, so it takes longer for the thrust to drop off to zero. Evidently, SpaceX engineers did not take this into account by lengthening the time between engine cutoff and stage separation. The small amount of remaining thrust enabled the first stage to catch up with the second stage again instead of being out of the way when it ignited. You can see the whole thing in the video posted by SpaceX.
I mentioned last week that the various newspace bloggers and industry pundits have been engaged in an orgy of speculation and criticism. The new information from Musk didn't really quiet the crowd. It just shifted the focus to a discussion of whether this problem could have been foreseen and avoided. At some level that's no doubt true. Before the release of the video, some commentators had leapt immediately to the correct explanation, knowing nothing more than that there had been a "stage separation failure" and that this was the first flight with a regeneratively cooled engine. Much has been made, as well, about the fact that SpaceX has experienced three consecutive failures.
Why did they fail? There has a lot of loose criticism of SpaceX implying they are are a bunch of amateurs. That's not consistent with what I've heard about their organization and I think it is very unfair. I don't mean to say that every mistake they have made is unavoidable. But I also think there's another reason why one would expect them to have more failures than the established aerospace companies. Their whole strategy is to find ways to simplify and automate the process of designing, building, testing and launching rockets. They are being innovative and taking risks by seeing which parts can be cheaper, which processes you can do without, which jobs you can automate, etc. If you're really going to find the floor on costs you have to go a little too low and then selectively restore some extra checks and redundancies as needed to get acceptable reliability. New, privately held, self funded companies can afford to take these kinds of risks more than established organizations.
Entrepeneurship drives progress in unique ways, and we are fortunate that we still have an entrepeneurial culture in this country. Most fail, but some succeed, and they do it by exceeding what earlier suppliers were able to achieve. If Musk is wrong, and there are no economies to be found in the way rockets are currently designed, built, tested and launched then he will fail. He might fail anyway if he makes too many mistakes. But I think his basic premise is sound and I suspect he will, in the end, succeed.
Sunday, August 3, 2008
SpaceX Falcon 1 Failure
Alas! Flight 3 of the SpaceX Falcon 1 vehicle ended with the loss of the vehicle. The flight seemed to be going well until shortly before stage separation. This is the moment when the first stage shuts down and is jettisoned, then the second stage begins firing. The live video stream from the rocket was cut off about 2:11 into the flight. A few seconds later the SpaceX announcer said there had been an anomaly. In a statement to his employees and the general public a short while later, Elon Musk said there had been a stage separation failure. We have no other information at this time, although speculation has been rampant in the blogosphere.
When something like this happens the blogosphere is always full of naysayers. I can't resist a few comments of my own. First, it is true this is a serious failure for the company. This flight didn't get as far as the last one, which doesn't look good. We have yet to learn how their customers will react to the failure. It is definitely a significant setback. Musk says he has brought in new investors and his cash position is very strong. He thinks he can weather the crisis. I still wouldn't bet against him.
Many of the naysayers appear to be part of the traditional aerospace industry and it seems almost as if they are hoping SpaceX will fail. They seem to be motivated by a desire to prove that no one can improve on their own track record. They would like to think that it is always going to take billions of dollars and an army of thousands to develop new spacecraft. But look at what SpaceX has already accomplished. With a total workforce of 525 people and no more than about $250 million expended so far, they have developed one small launch vehicle (Falcon 1), are well along in development of a medium lift vehicle (Falcon 9) and are working on a spacecraft that will dock with the International Space Station (Dragon). All that would have cost the Europeans about $5 billion!! Even Lockheed-Martin or Boeing would have spent far more. SpaceX can afford to lose several more Falcon 1 vehicles as they perfect their systems and still be way ahead of what anyone else has done in terms of cost efficiency. I really think the big boys better be looking in their rearview mirrors!
When something like this happens the blogosphere is always full of naysayers. I can't resist a few comments of my own. First, it is true this is a serious failure for the company. This flight didn't get as far as the last one, which doesn't look good. We have yet to learn how their customers will react to the failure. It is definitely a significant setback. Musk says he has brought in new investors and his cash position is very strong. He thinks he can weather the crisis. I still wouldn't bet against him.
Many of the naysayers appear to be part of the traditional aerospace industry and it seems almost as if they are hoping SpaceX will fail. They seem to be motivated by a desire to prove that no one can improve on their own track record. They would like to think that it is always going to take billions of dollars and an army of thousands to develop new spacecraft. But look at what SpaceX has already accomplished. With a total workforce of 525 people and no more than about $250 million expended so far, they have developed one small launch vehicle (Falcon 1), are well along in development of a medium lift vehicle (Falcon 9) and are working on a spacecraft that will dock with the International Space Station (Dragon). All that would have cost the Europeans about $5 billion!! Even Lockheed-Martin or Boeing would have spent far more. SpaceX can afford to lose several more Falcon 1 vehicles as they perfect their systems and still be way ahead of what anyone else has done in terms of cost efficiency. I really think the big boys better be looking in their rearview mirrors!
Saturday, August 2, 2008
Go SpaceX!
This is a big week for the newspace company SpaceX (Space Exploration Technologies). Today they announced the first nine-engine test firing of their new Falcon 9 booster. A video of the test firing is posted on their website.
Even more significant, perhaps, is the opening of the launch window for Flight 3 of their smaller Falcon 1 rocket. (The launch of Flight 2 is pictured at right.) Sometime between now and August 5 I'm hoping to watch a live webcast of their first successful launch into orbit. The first test launch of the Falcon 1 ended after 30 seconds of flight when a fire caused the first stage engine to fail. The second flight nearly made orbit, but sloshing fuel in the second stage tanks caused a premature engine cut-off. Flight 3 is not billed as a test flight, but an operational flight. They are launching an experimental DOD payload, along with two smaller payloads for NASA and one for the Malaysian space agency. I think they have an excellent chance for success, based on the progress made in the past two launches. I can't wait!
SpaceX is a new company founded by Internet mogul Elon Musk with the money he made from selling PayPal. It is one of a new breed of space enterprises often referred to as "newspace". These new companies, mostly self-funded, are aiming to create a new era of private commercial space travel by bringing down the cost of getting into space. The genius of newspace is to leverage the market economy and entrepeneurial spirit of this country to vastly accelerate the pace of innovation in this industry. Dozens of companies are trying dozens of different approaches. Most will fail, but some may succeed. Musk's approach is more conventional than most. He aims to beat the majors (Boeing, Lockheed-Martin) at their own game by producing conventional boosters that compete directly against existing ones, but undercutting their price. He is betting over $100 million of his own money on it.
How can a new company produce rockets cheaper than the big boys? I think there are several key elements of Musk's strategy:
Even more significant, perhaps, is the opening of the launch window for Flight 3 of their smaller Falcon 1 rocket. (The launch of Flight 2 is pictured at right.) Sometime between now and August 5 I'm hoping to watch a live webcast of their first successful launch into orbit. The first test launch of the Falcon 1 ended after 30 seconds of flight when a fire caused the first stage engine to fail. The second flight nearly made orbit, but sloshing fuel in the second stage tanks caused a premature engine cut-off. Flight 3 is not billed as a test flight, but an operational flight. They are launching an experimental DOD payload, along with two smaller payloads for NASA and one for the Malaysian space agency. I think they have an excellent chance for success, based on the progress made in the past two launches. I can't wait!
SpaceX is a new company founded by Internet mogul Elon Musk with the money he made from selling PayPal. It is one of a new breed of space enterprises often referred to as "newspace". These new companies, mostly self-funded, are aiming to create a new era of private commercial space travel by bringing down the cost of getting into space. The genius of newspace is to leverage the market economy and entrepeneurial spirit of this country to vastly accelerate the pace of innovation in this industry. Dozens of companies are trying dozens of different approaches. Most will fail, but some may succeed. Musk's approach is more conventional than most. He aims to beat the majors (Boeing, Lockheed-Martin) at their own game by producing conventional boosters that compete directly against existing ones, but undercutting their price. He is betting over $100 million of his own money on it.
How can a new company produce rockets cheaper than the big boys? I think there are several key elements of Musk's strategy:
- Hire the best and the brightest engineers away from the majors.
- Run a lean operation with a flat structure and a spirit of innovation that empowers these engineers to produce the best products possible with the least overhead.
- Start with a clean-sheet design while still leveraging the accumulated experience of the past fifty years.
- Optimize the design for lowest price instead of highest performance.
- Leverage automation whereever possible to reduce labor costs in the design, manufacture, testing, and operation of the vehicle.
So far SpaceX is doing rather well financially. They haven't put a single payload into orbit (yet!), but they have at least a dozen missions on their launch manifest. They won a COTS (Commercial Orbital Transportation Services) contract from NASA worth $278 million that is helping to bankroll their development work, and have so far made all their milestones. The big question, I think, is not whether they will get to orbit successfully, but whether over the long haul they can deliver on their promise of significantly lower launch costs than the majors. Right now, I wouldn't bet against them. Go SpaceX!
[Afternoon update] SpaceX has announced the opening of a five hour launch window at 6:00 pm CDT (4:00 PDT and 7:00 EDT). Webcast will begin 30 minutes before launch.
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