positioning system

840 would like to make an inertial positioning system. Does anyone from the teams that have made one have any tips/advice?

*Originally posted by srjjs *
**840 would like to make an inertial positioning system. Does anyone from the teams that have made one have any tips/advice? **

I assume you’re talking about next year or something to work on in the off season, right?

Your question is pretty broad - do you have more specific questions? You’ll probably need an external microprocessor on a custom circuit board. Have you thought about which one you want to use? Have you checked out sensors that you’d like to use?

Yes, this is something for our team to work on in the off season, as we are not going to nationals.
I am just looking for some general stuff, like how much it will cost, how long it will take, what kind of stuff to use, etc.
A step-by-step guide would take away most of the challenge.

The hard part with an INS is the actual programming. Building 190’s INS didn’t take very long, but getting it to communicate with the RC, getting it calibrated, filtering out noise, and general troubleshooting has been a major challenge. Our programming team spent the entire build season working on it, and has been working with a second INS and the EduRobot since the build season ended, and as I type this, they are probably busy in the pits at Seattle still perfecting it.

The other thing you need to know is that the gyros in the kit are not fast enough to work in a real world situation (I think they only track up to 110 degrees/sec), so we had to buy some 300 degree/sec gyros out of our additional electronics budget. Also, noise control is a big issue. With the noise we are getting, in a worst case scenerio, our INS can think it has reached escape velocity in 15 seconds while the robot is standing still (although it usually averages out to provide reasonable results during our autonoous mode, when we really need it). Don’t forget that you need to do a double integral to determine position, so any noise in acceleration or yaw rate would be cubed.

I’d encourage you to go ahead and try it. It is always to to see FIRST teams pushing the envelope.

What did you use instead of the gyro in the kit? I bought the evaluation version of the Analog Devices ADXRS150 gyro. Its mounted on a very small PCB that is the same size as a regular 20 pin DIP IC. The part number is ADXRS150EB. The standard max velocity is 150 degrees per second, but the rate can be increased by adding a resistor up to 300 degrees per second. It also includes an onboard low-pass filter for some noise rejection. I was just wondering if anyone has used it.

And all these components fit under the electronics cost limit?