Vibration dampers for stepper motors

Stepper motors are used in many electomechanical systems for accurate positioning and precise motion. The dynamic torque characteristics of stepper motor are one of the important factors when selecting a motor to fit the dynamic design requirements. Many other factors influence the dynamic characteristics of a stepper motor's performance. External inertia, driver type, phase current, external viscous load ,control strategy, and resonance at certain speeds make spacifing the stepper motor in the design a difficult task. The stepper motor usually has a resonancs speed where the operating speed coincides with the motor's natural frequency, thus causing the dynamic torque to drop dramatically. An expensive shaft damping scheme for dealing with resonance speed is an attractive option. The damper\absorber systems described in this thesis are a dual cantilever beam-mass system (The same concept was used by Lexmark but with diffrent configurations), a self-tuned system (modification of the beam-mass system), a change of intertia concept, and a friction damper. The dampers can be cost efficient, easy to install on the motor, and easy to manufacture. The dampers/absorbers/ designed for a specific speed range gave 70%-90% improvement over the case where no damper/absorber was used. This thesis discusses the design methodology of the dampers/absorbers used and presents an over view of operation. The dampers/absorbers performance and damper/absorber charactristics are included along with mathematical models, recommendation, and failure modes.