The UAV Devboard is back in stock at SparkFun, with a new design.The reason for the design change is that Analog Devices no longer makes the gyro that we were using on the previous board, so we have switched the design to the LISY300AL. Paul Bizard and I have thoroughly tested the new board on fixed-wing aircraft, the LISY300ALs work just great with DCM.We have modified all of our existing firmware to be able to run on either board, and will make sure that all future firmware will also work on either board. If you have written firmware for the UAV dev board, you will only have to make a few minor changes to run it on the new one. The two board designs are nearly identical. The only differences are:1. The new board uses LISY300AL gyros instead of the ADXRS401, and the 6g range instead of the 1.5g range for the accelerometers. This will allow you to provide aerobatic control without saturating the sensors.2. The gyros, the accelerometers, and the A/D reference voltage are all tied to the 3.3 volt regulated supply. This will totally eliminate drift of gyros and accelerometers due to supply voltage changes.Each firmware project now has both a "green" version for the previous board and a "red" version for the new board.
You are correct, heli applications might well need the more expensive gyros, but there is no way to tell without specific data. It might be that my board will work ok in a heli if you take care to mount it to reduce vibration. Or maybe not. If anyone wants to give it a try and decides to use my board to stabilize a heli, I will help them.
If I were to offer a board for specifically for heli applications, I would probably start from scratch on a new design for helis that would include more servo channels, and probably would use the dsPIC30F6015, and possibly a 3 axis magnetometer.
But I am finding that just supporting the board that I have, which really targets just fixed-wing aircraft, is taking more time than I thought, so I have put a heli board design on the back burner for now.
Brian's board looks like just the thing for heli applications, I am really impressed. Plus, he has ported DCM to it, and it has a magnetometer. I expect he is going to get some great performance out of it. Top flight stuff.
If I understand correctly the more expensive boards only differ in the gyros. As noted in this thread, heli applications might need the more expensive gyros. If they are no longer available, you might consider offering them up for heli apps. I have to make a decision between Bill's board and Brian's. Brian's seems more appropriate for heli application with 3 servo swash and throttle control (plus other sensors), but not yet available. Sure would be nice to get some specific data on these two boards on a heli.
That $150 price drop is astounding! I have mixed feelings--happy for Bill and the many new customers who will now get to use this great board at this price, and a slight feeling of regret for buying two of the older boards at price that could have bought four of the new ones.
I have done some more testing this week, I am still satisfied with the choice of sensors, though I caution that anyone who wants to use the new board in high-vibration applications (such as helis), should test them first.
One of the improvements we made to the board is to run the sensors and the A/D reference all off the same regulated 3.3 volt supply. That completely eliminates drift due to power supply variations. So the firmware no longer has to make a correction for supply voltage drift.
I have revised all of my firmware so that it will run on either my old board (the green one), or my new board (the red one), and tested it out. As soon as the new boards come out, I will release the new firmware. Each file will come with two projects in it, a "green" one and a "red" one.
SparkFun has told me that the new board may be out before the end of May, but we will see. I will certainly make an announcement as soon as I know.
SparkFun is now taking back orders for the board. I notice that the price is still listed as $299, but I am pretty sure that will come down as soon as they are ready to sell the new boards. My guess is the price will change when they put up the picture of the new board, but I do not know what the new price will be.
I'm eagerly awaiting your next devboard release! Have you gotten to do any more testing this week? Are you still satisfied with the choice of new sensors? How is the early June ETA looking at this point, for the board to be available for purchase from sparkfun?
The IDG-650 and ISZ-650 look good on paper, but the only way to know for sure is to test them. I think it is certainly worth trying them out.
I think that 2000 deg/sec is overkill. That is 5 revolutions per second.
There is a price to be paid in going to a range that is too high, you lose resolution unless the A/D has a lot of bits, and you are more susceptible to noise and drift. You should use a range that is just high enough to cover the requirements of your mission.
I'm hoping to hear good things about the IDG500. Combine that with an ISZ 500 (or any other gyro out there, really) and you won't need vertical boards any more.
First, I agree with you, Tom, about the vibration issue with the LISY300. I stipulate that the LISY300 is vulnerable to vibration at 4 kHz. As you say, enough vibration at that frequency will rattle the LISY300 hard enough so that there is nothing you can do. So, I do not recommend that anyone use my new board in high-vibration applications, at least not without testing it first. You are right, the new Analog Devices gyros with a 15 kHz resonant frequency should be less vulnerable to the vibration that a helicopter generates. If I ever get around to designing a board for helicopters, I will probably use the Analog Devices gyros.
That said, I think there are things that you can do to mitigate the vibration issue for the LISY300. I mount my board in my planes with velcro. In addition to making it easier to install and remove, it does provide quite a bit of isolation from shock and vibration. Though velcro might not be strong enough for helicopter applications, it could work for fixed-wing aircraft with internal combustion engines. It works perfectly well in fixed-wing electrics.
Also, at first I definitely did see a shock issue with the LISY300s on my prototype board. Whenever I flicked the board, the DCM algorithm jumped. However, that problem completely went away when I raised the sampling rate. So it is not entirely clear to me that any problem anyone has ever had with the LISY300 is a vibration issue. They may simply have not used a high enough sampling rate. I think that with vibration, it is a question of degree. I think that if there is moderate vibration problem, you can improve the situation with a higher sampling rate to prevent aliasing of the response to vibration. If there is a large problem, there is nothing that you can do.
@Brian
Regarding the Invensens gyros, it is my understanding that Paul Bizard had some problems with those. Paul bought the 5 DoF IMU from SparkFun with the IDG-300 X-Y gyros. I convinced him he needed a third gyro for our DCM algorithm, so he bought a LISY300 later on. He built a copy of my UAV DevBoard. He never got it working to his complete satisfaction. There appeared to be a huge amount of drift from the IDG-300. He was able to do a direct comparison between the LISY300 and the IDG-300, the LISY300 was drift-free by comparison.
I have not ever tried the IDG-300, so I do not know. As I am sure you know, as you move up to higher range gyros, the issue of drift becomes aggravated.
I assume that you have tested the Invensens for drift, in which case I am sure that everyone would be interested in what you found.
Finally, I like your idea for providing some shock and vibration isolation in the mounting of your board.
Comments
You are correct, heli applications might well need the more expensive gyros, but there is no way to tell without specific data. It might be that my board will work ok in a heli if you take care to mount it to reduce vibration. Or maybe not. If anyone wants to give it a try and decides to use my board to stabilize a heli, I will help them.
If I were to offer a board for specifically for heli applications, I would probably start from scratch on a new design for helis that would include more servo channels, and probably would use the dsPIC30F6015, and possibly a 3 axis magnetometer.
But I am finding that just supporting the board that I have, which really targets just fixed-wing aircraft, is taking more time than I thought, so I have put a heli board design on the back burner for now.
Brian's board looks like just the thing for heli applications, I am really impressed. Plus, he has ported DCM to it, and it has a magnetometer. I expect he is going to get some great performance out of it. Top flight stuff.
Best
John
If it makes you feel any better, I bought 2 of the green boards myself. ;-)
Bill
I have done some more testing this week, I am still satisfied with the choice of sensors, though I caution that anyone who wants to use the new board in high-vibration applications (such as helis), should test them first.
One of the improvements we made to the board is to run the sensors and the A/D reference all off the same regulated 3.3 volt supply. That completely eliminates drift due to power supply variations. So the firmware no longer has to make a correction for supply voltage drift.
I have revised all of my firmware so that it will run on either my old board (the green one), or my new board (the red one), and tested it out. As soon as the new boards come out, I will release the new firmware. Each file will come with two projects in it, a "green" one and a "red" one.
SparkFun has told me that the new board may be out before the end of May, but we will see. I will certainly make an announcement as soon as I know.
SparkFun is now taking back orders for the board. I notice that the price is still listed as $299, but I am pretty sure that will come down as soon as they are ready to sell the new boards. My guess is the price will change when they put up the picture of the new board, but I do not know what the new price will be.
I'm eagerly awaiting your next devboard release! Have you gotten to do any more testing this week? Are you still satisfied with the choice of new sensors? How is the early June ETA looking at this point, for the board to be available for purchase from sparkfun?
The IDG-650 and ISZ-650 look good on paper, but the only way to know for sure is to test them. I think it is certainly worth trying them out.
I think that 2000 deg/sec is overkill. That is 5 revolutions per second.
There is a price to be paid in going to a range that is too high, you lose resolution unless the A/D has a lot of bits, and you are more susceptible to noise and drift. You should use a range that is just high enough to cover the requirements of your mission.
I am very impressed with your board, I must say it is very sophisticated and complete. Good luck with it.
Bill
First, I agree with you, Tom, about the vibration issue with the LISY300. I stipulate that the LISY300 is vulnerable to vibration at 4 kHz. As you say, enough vibration at that frequency will rattle the LISY300 hard enough so that there is nothing you can do. So, I do not recommend that anyone use my new board in high-vibration applications, at least not without testing it first. You are right, the new Analog Devices gyros with a 15 kHz resonant frequency should be less vulnerable to the vibration that a helicopter generates. If I ever get around to designing a board for helicopters, I will probably use the Analog Devices gyros.
That said, I think there are things that you can do to mitigate the vibration issue for the LISY300. I mount my board in my planes with velcro. In addition to making it easier to install and remove, it does provide quite a bit of isolation from shock and vibration. Though velcro might not be strong enough for helicopter applications, it could work for fixed-wing aircraft with internal combustion engines. It works perfectly well in fixed-wing electrics.
Also, at first I definitely did see a shock issue with the LISY300s on my prototype board. Whenever I flicked the board, the DCM algorithm jumped. However, that problem completely went away when I raised the sampling rate. So it is not entirely clear to me that any problem anyone has ever had with the LISY300 is a vibration issue. They may simply have not used a high enough sampling rate. I think that with vibration, it is a question of degree. I think that if there is moderate vibration problem, you can improve the situation with a higher sampling rate to prevent aliasing of the response to vibration. If there is a large problem, there is nothing that you can do.
@Brian
Regarding the Invensens gyros, it is my understanding that Paul Bizard had some problems with those. Paul bought the 5 DoF IMU from SparkFun with the IDG-300 X-Y gyros. I convinced him he needed a third gyro for our DCM algorithm, so he bought a LISY300 later on. He built a copy of my UAV DevBoard. He never got it working to his complete satisfaction. There appeared to be a huge amount of drift from the IDG-300. He was able to do a direct comparison between the LISY300 and the IDG-300, the LISY300 was drift-free by comparison.
I have not ever tried the IDG-300, so I do not know. As I am sure you know, as you move up to higher range gyros, the issue of drift becomes aggravated.
I assume that you have tested the Invensens for drift, in which case I am sure that everyone would be interested in what you found.
Finally, I like your idea for providing some shock and vibration isolation in the mounting of your board.
Best regards,
Bill Premerlani
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