Subject:
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Re: "Servo" Driver for NQC
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 30 Jan 2002 21:46:53 GMT
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Viewed:
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784 times
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The ON/OFF bang-bang control you are trying has some problems that
proportional control does not. While it is true that if the update rate is
high enough, or the controlled plant damped enough, that switching a drive
ON and OFF can simulate proportional control and give you variable speeds, I
don't think that the RCX is up to the task.
I really think you should try using the different motor settings on the RCX
to control your speed. You may have to introduce some drag in the drive
train to make it work well. One easy way to do this is introduce a fixed
friction gear (the white ones where the gear teeth can move even if the hub
if fixed).
If you don't need "servo" control, but instead just want to minimize jerk at
the beginning and end of each move there is a simpler way to achieve this.
When you start your moves, use low motor power levels. If you need lot's of
power, start low and ramp it up over time.
When you approach the end of a move, ramp down the power level. When you
get to the end you can apply the brakes. By that time you should have
slowed down a bit.
One last idea. Instead of turning the motor off, have you tried reversing
direction? I'm pretty sure that the motors can react more torque when they
are braking than they can at low power settings.
Hope this helps
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Message is in Reply To:
 | | Re: "Servo" Driver for NQC
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| Rebel Transcanner wrote: > (...) I take it you are really doing on...float...on...float cycles with your motor instead of using "off", which actually performs active braking (on/off cycles are almost guaranteed to give serious mechanical jitters). (...) (23 years ago, 29-Jan-02, to lugnet.robotics)
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