Eliminate resonant frequencies

First position the mover to be tuned in a straight section of track. The straight sections are much easier to tune than the curved sections. Eliminate resonance in the straight section, then test for resonance in the curve and adjust the filters as necessary. The TcTuningAssist can greatly help in selecting filters and filter settings for movers that can flex slightly. For very inflexible flex movers (steel wheels, steel rails) very little oscillation occurs and a low pass filter with a filter frequency of > 500Hz can be used.

Eliminate resonant frequencies 1:

Eliminate resonant frequencies 2:

Start the Scope of the Axis, Enable the Axis and monitor the oscillations. Depending on the load these Oscillations can be extremely loud > 80dB. Increase/decrease the filters as necessary until the mover settles nicely without significant oscillations.

First Enabling and moving:

 

Step 1

For the filter the main concern is not the operation of the mover while moving it’s the small resonance at a frequency > 100 Hz that continues while the mover is stopped that must be eliminated. Here the oscillation is at 146Hz. It can be seen that 100ms after the set velocity is zero the control loops switch from moving parameters to standstill parameters and while the amplitude of the oscillation slightly decreases the frequency remains the unchanged.

Step 2

Through trial and error it may be possible to eliminate the resonance by setting the filters low or setting the filters high.

This has an oscillation of about 4mm/s

Eliminate resonant frequencies 3:

Eliminate resonant frequencies 4:

Step 3

Step 4

The system will now be tested with lower bandwidth to see if it performs better.

Here the velocity ripple is very low 2mm/s when at standstill.

Now it will be attempted to reduce the LowPassFilter Frequency with the original Bandwidth.

Eliminate resonant frequencies 5:

Eliminate resonant frequencies 6:

Step 5

Step 6

With this configuration there is a lot of oscillation.

It is clear that regardless of the bandwidth, setting the low pass filter lower makes the oscillations in this system worse.

For this system a LowPassFilter setting of 320Hz and bandwidth 250Hz will be selected. This is because while the results are marginally better with a low bandwidth, higher settings are always preferred when possible. A higher bandwidth allows a faster the reaction.

Eliminate resonant frequencies 7:

Eliminate resonant frequencies 8:

The mover behaves much more poorly than the straight sections. This is to be expected, the physics of motion change when rotating vs travelling in a straight line. The important part is that there are no high frequency oscillations in the curves, if the mover oscillates in the curves, the filters must be re-adjusted so that the mover does not oscillate in the curve.

The use of the TcTuningAssist can determine the filter settings much more precisely than trial and error.