We have been running a gimbal motor (T-Motor GB54-1) at 120 RPM using gimbal motor mode on a 24V board (supply voltage of 19V). It works well. For a new build, we switched to the 48V board and use a 24V supply voltage, and with the same settings as before, we are getting lots of ERROR_MODULATION_MAGNITUDE when attempting to go into closed loop control. Sometimes it works, then the next time it doesn’t, sometimes rerunning the calibration sequence helps, sometimes not. I urgently need to get this working and I’m not sure what further steps to take to debug the errors.
Here are the settings we use:
config: brake_resistance: 0 # no brake resistor is installed enable_ascii_protocol_on_usb: 1 enable_uart: 0 dc_bus_undervoltage_trip_level: 8 dc_bus_overvoltage_trip_level: 26 axis1: config: startup_motor_calibration: 0 startup_encoder_index_search: 1 startup_encoder_offset_calibration: 1 startup_closed_loop_control: 0 startup_sensorless_control: 0 motor: config: pre_calibrated: 1 pole_pairs: 7 resistance_calib_max_voltage: 6 # volts motor_type: 2 # gimbal current_lim: 8 # V (in gimbal mode, currents are actually voltages) calibration_current: 4 # V (in gimbal mode, currents are actually voltages) encoder: config: mode: 0 pre_calibrated: 1 cpr: 2048 use_index: 1 bandwidth: 250 controller: config: control_mode: 2 # velocity control pos_gain: 100 vel_limit: 8192 vel_gain: 5.0e-4 vel_int_gain: 8.0e-3 vel_deriv_gain: 3.0e-2 vel_filter_fc: 3000 vel_setpoint: 0
current_lim are set well below half of the bus voltage, as recommended by the troubleshooting page. With these settings the motor starts on the first try (entering closed loop control after finishing the calibration sequence) about 56% of the time. We tried increasing
calibration_current to 6 volts, and it started every time, but this may be a fluke. Either way, after idling the motor and then trying to start it again, we get ERROR_MODULATION_MAGNITUDE on the second or third run each time. Note that once the motor starts up without an error, it seems to run fine.
As I said, these settings have been working 100% of the time on our 24V board for months, so this is quite mysterious. Please let me know how to proceed! I am fine with applying a firmware fix if there is one.