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Originally Posted by billbo911
Simply comparing the controller's position to the robot's arm, or which ever axis your controlling, and using the difference to drive a motor will work. Yes, there are some obvious drawbacks, but as for speed limiting, that can simply be done in the position comparing function.
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There are many factors that play into the success you will have with position feedback control like: mass being moved, friction in the system, moment of inertia, system speed etc. If you find that your system oscillates, then you will want to replace your simple comparative function with a PID function which will allow tuning of your axis control. Otherwise, it may not be necessary.
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If I understand this method, one sets the PWM motor control based on a percentage of the maximum difference. I.e. If the maximum range of motion on an axis is 180 degrees, when the difference between the mimic control and the robot arm is 180 one sets the motor speed to full, 100%, speed. As it moves into position the motor set point is reduced. When the difference is only 90 degrees, the motor speed would now be only 50% of max speed. If Frictional losses and moments of inertia are favorable, this method may not create oscillations around the setpoint.
APS