Ground Robot (GBOT) Object Tracker with PID Contro

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liam.nv
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Ground Robot (GBOT) Object Tracker with PID Contro

Post by liam.nv » Thu Mar 04, 2010 10:25 pm

Hello,

This is the GBOT with a PID controller using the ZX-40A microcontroller from http://www.zbasic.net. ZX-40A is based on the ATMEGA644 AVR chip. Inputs include 2 IR range sensors (GP2D12). Outputs include 2 PWM signals to the Pololu motor driver (VNH2SP30).

The GBOT maintains a setpoint distance of 10-inches from a target and maintains that distance, no matter what. The control system was originally coded with P-control only and resulted in excessive overshoot and oscillations. So then I added PID control. See video to observe P-control vs. PID control.

http://www.youtube.com/watch?v=uTh2DBWAbPs

Had trouble with IR sensor noise. Issue mitigated with hardware and software. Hardware... added low ESR 1,000uF capacitors on VIN and VOUT of the LM2940T voltage regulator. Software includes an 8th order butterworth filter to clean IR sensor position and velocity. I did have issues with a fire, probably caused by a short or the motor driver. Not sure yet. Since isolating the regulator with the filters and after adding a large heatsink to the voltage regulator, no more fires. See picture below of "incident".

http://www.zbasic.net/forum/download-329.html

Anyone have experience or information on GP2D12 IR sensor distance variabiability? I have the noise reduced to 0.025" amplitude. Can this be reduced further? Thanks.

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