Thanks ESjaavik. Linux/EMC sounds like a good alternative RT system, but I still do not understand why backlash is a problem when using linear encoders.
I still think DOS has a future with the PC104 range of products.
As for my DOS system I don’t try to ‘calm down’ the PID loop but the parameters are set to maintain stability.
Inputs to the loop are two +/- 10 volt analogue signals, 1 from the motor tacho, the speed input ,and 1 from the computer, the position input.
Feedforward is not implemented but the system ‘looks ahead’ (to avoid SUDDEN setpoint changes) and the speed is adjusted depending on the angle of the next move. If the next move angle is 180 deg. then full speed is maintained, a 90 deg move requires the machine to ramp down to zero before implementing the next move thus avoiding any overshoot.
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mike potter |