Structural Mechanical Limitations of Dynamics of Servo Drives

The influence of structural mechanical resonance frequencies of servo motors on control loop dynamics is analyzed. The mechanical resonances caused by the mechanics of the motor or the linkage of the built-in position measuring device to the motor are low damped. A generalized mathematical model for the mechanics of servo motors is derived and verified on various motors and for different linkage principles of the position measuring device. The achievable bandwidth in the speed control loop, taking into account the current control loop bandwidth of IGBT-based and wide-bandgap-based inverters, is theoretically analyzed and practically verified.