Quote:
Originally Posted by Ether
@ CD control gurus:
Assuming it is desired to synchronize position (both the steady-state position and while the actuators are moving), what control method(s) would you recommend
a) if the driver is issuing a position command, and
b) if the driver is issuing a speed command
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I wouldn't claim to be a guru (far from it), but I can share our experience last year. We wrote a 'drive straight' algorithm for tank drive. I believe we drove the left side only at a requested rate. The left side set the right side power to the same as the current side was using. It then compared positions and put in a proportionally slower speed to the amount of error on the leading side. It seemed to work-- it went as straight as we could calibrate the distance on the encoders. At a set point though I would think each on an independent pid would work well.. our drive straight did poorly when we tried to stop at a distance... in retrospect, thinking through it in light of this conversation, I think once we were within some distance of a position point, we should have released the master/slave relationship and let each one arrive at the correct distance to their own devices.
Year before we tried to drive 2 mechanisms completely in sync on PIDs (had very low tolerance for getting out of sync. But the code was climbing the robot and the pid could not react quickly enough if force on one side increased. In the end they fused the right/left together mechanically and it was much easier to code. So when in doubt, a hardware fix may be the best option.
Looking forward to hearing what the gurus suggest.