The oscillation of the stepper motor and brushless step is a widespread phenomenon, affects the normal operation of the application system, so as far as possible avoid to use.
1, the oscillation
stepper motor oscillation occurs mainly in: step motor working in the low frequency area; Stepper motor work in resonance zone;
1）Low frequency oscillation:
when brushless stepper motor in the low frequency region, as a result of the excitation pulse interval is longer, stepper motor performance for a single step.
when the incentive in the beginning, the rotor speed under the action of electromagnetic force. When you arrive at equilibrium. Magnetic drive torque to zero, but the rotor has a relatively high rotation speed. Because of inertia, rushing rotor balance. At this point, the electromagnetic force to produce negative transfer, and under the action of negative torque, rotor to zero and began to gradually along the opposite direction. When the rotor inversion of balance. Electromagnetic force and generate positive torque, forcing the rotor rotating along the forward direction. It continue to form rotor oscillation around the equilibrium point. Because of the influence of mechanical friction and electromagnetic damping the oscillation of damping oscillation and stability in the equilibrium state.
2）Low frequency resonance:
when brushless pulse frequency of step-motor to the stepper motor natural oscillation frequency of the oscillation frequency divider or frequency doubling, volatility, and in severe cases caused by the steps.
when brushless stepper motor working in high frequency region, due to the reversing cycle is short, the rotor was too late to recoil. At the same time. Winding current didn't rise to the stable value of, and the rotor didn't get enough energy, therefore no oscillation in the upper area.
2, out-of-step
stepper motor step for two reasons:
1)Rotor speed slower than the speed of a rotating magnetic field, or in the reversing speed slow.
when the stepper motor starts, if the pulse frequency is higher, the speed of the rotor can't keep up with the rotating magnetic field, because the motor cannot get enough energy, therefore lead to out of step. As a result, the stepper motor can start frequency. When more than the starting frequency, is bound to produce less out of step. Note: the initial frequency is not a fixed value. Increase the torque of the motor, reduce the load moment of inertia, and decrease the step Angle can increase the stepper motor startup frequency.
2）The average speed of the rotor is greater than the speed of a rotating magnetic field. This occurs mainly when braking and suddenly the reversing, rotor get too much energy, lead to serious overshoot, lead to out of step.
mechanical damping method is relatively simple, which increases the damper on the motor shaft, and various electronic damping rules:
1)Multiphase incentive methods
electromagnetic damping, multiphase incentive attenuation or eliminate oscillation, such as double three and six reactors of the models of the motor.
2）Frequency conversion transformation methods
brushless stepper motor under high frequency and low frequency with different energy. At low frequency, the current in the winding up for a long time, and the rotor of energy is very big, therefore likely oscillation, and vice versa. Therefore, can be designed with lower voltage with lower frequency circuits, thus reducing low-frequency winding current, and can effectively eliminate the oscillation.
3）Subdivision step
the stable current brushless stepper motor winding is divided into several levels, one step at a time current is added, the step frequency is also relatively increase, step by step process smoothly.
