Adjusting The Resonance Suppressing Filters - Renesas RX24T Reference Manual

Reference Guide for a 2-Axis Robot Arm with 2-Phase Stepping
Motors Incorporating Resolvers

3.1.2 Adjusting the Resonance Suppressing Filters

Since this demo system has a gearless structure in which the arms and motors are directly connected to
each other, mechanical resonance will tend to occur, so tuning of the resonance suppressing filters will be
necessary. The resonance suppressing filters for both the 42-mm square board and 85-mm square board
are adjusted by the following procedure with the 42-mm square motor and 85-mm square motor connected
to the respective arms.
1. Drive the motor by sending a desired position reference from the RMW, measure the frequency
characteristics between the speed instruction at that time and the actual speed by using an FFT analyzer,
and identify the resonance frequency (see Figure 3-1). If a resonance peak and an antiresonance peak
are present, record the frequency of each peak. If multiple resonance points are visible, record the
resonance frequencies in the same manner. Note that if you do not have an FFT analyzer when an
appropriate position reference value is given, monitor the feedback value of the position signal in the
microcontroller by using a D/A converter or an optional external sensor (e.g., vibration sensor) and
estimate the resonance frequency from the resonance waveform (see Figure 3-2).
2. Use software to change the arguments of R_MTR_SRFOC_SetTorqFilterParam, which is called from the
init_torq_filter function in r_app_main.c within the project of the sample software for motor driving, to suit
the resonance frequency and execute rebuilding.
3. Connect the emulator to each board and write the rebuilt software.
4. Connect the RMW and give a desired position reference again to confirm that the resonance
characteristics have been improved. If not, return to step 1 and revise the filter.
Gain characteristic
Phase characteristic
Figure 3-1 Confirmation of Resonance Frequency by FFT Analyzer
R01AN5644EJ0100 Rev.1.00
Jan 22, 2021
-90 degrees
RX24T, RX72M,
RAA3064002GFP/RAA3064003GFP
Resonance frequency
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