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    How to prevent stepper motor losing step?

    Stepper motor is an open-loop control motor which transforms electric pulse signal into angular displacement or linear displacement. In the case of no step losses, the motor speed and stop position depend on the pulse signal frequency and the pulse count instead of the variation of the load. When the stepper motor receives a pulse signal, the motor will rotate a fixed angle (step angle) according to the setting direction. The motor angular displacement and motor speed can be controlled by controlling the pulse number and pulse frequency, so as to achieve the accurate open loop control. However, there are some errors occuring between the actual angle stepper motor rotates and the theoretical step distance. There are some certain errors from one step to any other step, but the step number of each cycle of the stepper motor is the same. In the case of no step loss, the step error is not accumulated for a long time.
    How to prevent step loss with stepper motor as the above mentioned? First of all, we need to know why stepper motor losses step?

    1. The rotor acceleration is slower than the rotating magnetic field of the stepper motor. In other words, when the rotor is slower than the commutation speed, the motor will loss step. The reason is that the input of the motor power is insufficient and the torque generated cannot keep up with the rotor speed of the stator magnetic field, resulting the step loss.
    2. The average speed of the rotor is higher than the average rotating speed of the stator magnetic field. The stator takes longer time to energize excitation, which is more than the time required for the stepper motor. The rotor gains too much energy in the stepping process, resulting in the torque generated by the motor is too large and motor stepping. 
    3. The load inertia of stepper motor is large.
    4. The stepper motor produces the resonance.

    Actually, the reason for the stepper motor losing step is essentially the improper choice of stepper motor driver. Only by choosing the right and appropriate stepper motor driver can the stepper motor exert its precise control advantages. Selecting the right stepper motor driver requires a driver greater than or equal to the current according to the current of the motor. If a low vibration or high accuracy is required, a subdivided drive can be used. For large torque motor, high voltage type actuator is used as far as possible to obtain good high speed performance. At the same time for the driver, many people directly use the switching mode power supply as the drive power supply. However, it is generally better not to use switching power supply, especially for the high torque stepper motor, unless switching power supply is more than twice as much as the required power. When the motor works, it is a large inductance load, the power supply will form instantaneous high pressure. The switching power supply overload performance is not good and it will protect the shutdown. And its precise voltage stabilization performance is not needed. Sometimes it may cause the switching power supply and the drive damage. For the driving power of the stepping motor, the DC power supply can be replaced by the conventional toroidal or R transformer.
    The production of the stepper motor resonance is that the pulse frequency of the motor is equal to the natural frequency of the stepper motor, and the frequency is related to the subdivision of the driver. When we use stepper motor, the subdivision ability of the actuator is very important. The smaller the resonance range is, the better is. The large load interia is caused by the overload of stepper motor. Aimed at this situation, we should avoid the motor overload in the use.

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