Tips for dealing with resonance
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Microstep operation
The smaller the microstep, the smaller the resonance problems. Due to the smaller step angle the overshoot angle is also reduced and the system has less pronounced resonance points. From experience, the 1/8 microstep already brings a relatively low resonance with it whereas there is hardly any improvement beyond 1/32 microstep. If no current compensation is provided or integrated in the microstep drive, a torque reduction of the motor occurs which can show up as a disadvantage in some applications.
Reducing the phase current
The higher the torque reserve, the higher the resonance excitation. Accordingly the resonance excitation is strongest during no-load operation and, therefore, brings the greatest resonance problems during testing. For this reason tests should preferably be carried out in the application because frictional torques are usually present here and hence the complete system is damped. In addition to the tendency to oscillate, however, the phase current reduction also minimizes the stiffness and must be taken into account in the positioning accuracy if no current compensation is integrated in the drive.
Changing the step frequency
The basic resonance of the stepper motors during no-load operation is full step at approx. 70-100 Hz and appears again more or less strongly at multiples or harmonics of the basic resonance. It is easiest to avoid the established resonance frequency if the process allows by choosing a frequency that is somewhat higher or lower (if necessary, through the interconnection of a gear or by changing the reduction gear ratio). Small deviations from the critical step frequencies already show good results.
Increasing the friction
The friction generally has a damping effect on the system and the overshoot angles become smaller. However, the reserve torque is reduced by this and the efficiency deteriorates.
Affixing a damper
The dampers offered by Nanotec reduce the overshoot angles and absorb the vibrational energy. The resonant frequencies are greatly reduced because the speed difference between the oscillating rotor and the external mass is reduced as well. Also the high running noise is greatly reduced by affixing a damper.
Changing the ramp gradient
At relatively low motor acceleration, it is possible to reach the points of resonance again during the run up time that make the system unstable once more. By contrast, a steep ramp has few sampling points the torque reserve is reduced by the high acceleration and the system has a more damping action.
Reducing the tendency to oscillate
In addition to the reduction of the tendency to oscillate with microstep, the danger of vibration declines with decreasing supply voltage due to the lower speed of the increase in current.
