Mach-DSP User’s Manual
Document Number: MACH-DSP-9021
Page 91
www.ScannerMAX.com
Revisiting Damping and Position-Proportional gain improves performance
The screen shot below is almost identical to the screen shot above. It uses exactly the
same Servo gain and Error Integral gain. However, here we see that we were able to
achieve critical damping with far less Low Frequency Damping, High Frequency
Damping, and Position-proportional gain. Here we see that we have achieved a step
time of only 250 microseconds, which is a 40% improvement over the step times
achieved in the previous two screen shots.
Also note that the position waveform now appears perfectly symmetrical in terms of time
needed to accelerate and decelerate. Comparing this to the screen shot above, the pink
trace shows that the position signal reached the half-way mark at around 125
microseconds, which is half of the 250 microseconds needed to achieve the full step.
The main lesson is that just because a step is critically damped does not mean that the
servo is optimally tuned. Indeed, it is possible to achieve critical damping with High
Frequency Damping and Low Frequency Damping adjusted to levels far greater than
are necessary.
Tuning must be done carefully to achieve the optimal performance possible with
ScannerMAX scanners and the Mach-DSP servo driver.
