步进电机tepper_motor.pdf

2/13/2012 STEPPER MOTOR Stepper motors are motors that convert digital information to mechanical motion. Stepper motors rotate in distinct angular increments (steps) in response to the application of digital pulses to an electrical drive. Three types: • Permanent Magnet (PM) • Variable Reluctance (VR) • Hybrid Attractive: • Simplicity in construction • Position control without feedback component • Low maintenance Disadvantages: • Resonance effect and long settling time • Heat (consume current regardless of load condition) • Slower than servo (DC) systems James A. Mynderse ME588 – Stepper Motors 1 PERMANENT MAGNET (PM) STEPPER Equilibrium position depends on phase of excitation. • Rotor and stator each have magnetic fields. • Miss alignment between stator and rotor causes torque, which will bring rotor into alignment with stator. • If excitation held constant, the rotor will not move. • If external torque is applied to rotor, it will move. As the rotor moves, field miss alignment will again generate restoring torque. This effect acts like a (nonlinear) spring. The magnetic field will generate holding torque even if the field coils are not excited – detent torque. James A. Mynderse ME588 – Stepper Motors 2 1 2/13/2012 PERMANENT MAGNET (PM) STEPPER Stepping Sequence N N N N N N S N