Hi Batuhan,
There are 2 main parameters that need to be adjusted in voltage control mode to improve the step response:
m.current_ctl_bw and m.voltage_ramp.
Set them to default values and increase m.current_ctl_bw until the static operation becomes unstable (rotor disturbances or whistling sound at low rpm).
Afterwards, increase the m.voltage_ramp until dynamic operation becomes unstable. Just run the motor up to 60-80 % setpoint and then send negative setpoint (-20% for example). If the motor is braking slowly making a sound like a dying animal or you are observing RUNAWAY DETECTED message in the log, the operation is unstable. Decrease the voltage ramp. Usually it’s value is not higher than 30 V/sec.