Too much or too little friction can cause problems in a motion control system, making it harder for servo drives to do their jobs.
High friction motors pose a control problem for machines, as the current required to overcome the stiction element of the motor may then exceed the desired command and result in position overshoot.
Low friction motors are typically designed with little to no cogging or magnetic detent, and require very low voltage levels to initiate motion. This can make things tricky for systems with an analog input to the servo drive, as even the slightest divergence from zero could create motion. Low friction motors will also typically have a low level of inertia.
Issues
- Hunting occurs when the target position is over-shot repeatedly by small increments due to stiction
- Excessive current output results when the system commands unnecessary holding torque when the motor settles a small distance from the target
- Systems with ultra-low friction may exhibit oscillation problems because of a lack of self damping
ADVANCED Motion Controls' Capabilities
- Servo drives can be tuned and filtered to respond to specific machine characteristics
- The "Integrator Decay" feature in DriveWare® is meant for high stiction applications and prevents the integrator from commanding a high current when trying to resolve small error signals
