Kasey Matejcek wrote: > No home made > With optical pickup > > Well, have you checked the quality of the signals, especially when the spindle drive is running the motor? There may be some kind of interference that is upsetting the encoder/counter circuit.
Probably examining the encoder velocity pin with Halscope will reveal if there are artifacts. If the spindle speed appears to jump rapidly, that is not physically possible. But, don't worry about apparent multiple counting, as the servo thread only samples position every one ms, assuming the servo thread is at the nominal rate. So, if you are running at 8 revs/second (480 RPM) then you would get 8 * 500 counts/second = 4000 counts/second, or 4 counts/servo period. These would appear to happen all at once, but the total position is just read once per ms. If the encoder velocity is free of any abnormal spikes, then you need to step through the PID control with Halscope, and see what pid.x.output is doing. If it is swinging wildly, then it needs more damping. The motor and spindle inertia will give it significant lag, and that lag makes a control loop hard to balance. What is happening is the PID senses the speed is too low and commands more output. the motor slowly speeds up the inertia of the spindle, and by the time it reaches desired speed, the system is accelerating, and it overshoots. D helps this by backing off when it sees the error decreasing. I can be counterproductive, as it places too much emphasis on past history, making the lag dominant. Jon ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
