When the equipment (motor and driver) is not damaged, the stalled motor torque is insufficient. When the stepper motor is fixed, the main factors affecting the torque are speed and current. The characteristic of stepper motor is speed The higher the torque, the smaller the current, and the smaller the current.
The stepping motor can only be controlled by digital signals. When the pulse is provided to the driver, the number of pulses issued by the control system is too short in a short time, that is, the pulse frequency is too high, which will cause the stepping motor to stall. To solve this problem, you must use acceleration and deceleration. That is to say, when the stepping motor starts, it needs to give a gradually increasing pulse frequency, and the pulse frequency during deceleration needs to be gradually reduced. This is what we often call the "acceleration and deceleration" method.
The stepper motor speed is changed according to the change of the input pulse signal. In theory, by giving the driver a pulse, the stepper motor rotates by a step angle (a subdivision step angle when subdividing). In fact, if the pulse signal changes too quickly, due to the internal back-EMF damping effect of the stepper motor, the magnetic reaction between the rotor and the stator will not follow the change of the power-on signal, which will cause stalled and lost steps. Therefore, when the stepping motor is started at a high speed, it is necessary to adopt the method of increasing the pulse frequency and also to have a speed-down process when it is stopped to ensure the precise positioning control of the stepper motor. The principle of acceleration and deceleration is the same. Here is an example of acceleration:
The acceleration process is composed of the basic frequency (lower than the maximum frequency of the direct start of the stepper motor) and the jump frequency (the frequency that gradually accelerates) to form an acceleration curve (the opposite of the deceleration process). Jump frequency refers to the frequency that the stepper motor gradually increases on the basic frequency. This frequency cannot be too large, otherwise it will cause stalled and lost steps. The acceleration / deceleration curve is generally an exponential curve or an adjusted exponential curve. Of course, a straight line or a sine curve can also be used. PLC ，都能够实现加减速控制。 Acceleration and deceleration control can be achieved by using single-chip microcomputer or PLC . For different loads and different speeds, you need to choose the appropriate base frequency and transition frequency to achieve the best control effect. Exponential curve. In software programming, first calculate the time constant and store it in the computer memory. 300ms 以上。 Generally, the acceleration and deceleration time of the stepping motor is 300ms or more. If you use too short acceleration and deceleration time, it is difficult for most stepper motors to achieve high speed rotation of the stepper motor.
Sudden stop of a motor is not necessarily a stall. The motor has the highest speed, as does a stepper motor. When the speed exceeds the maximum speed of the stepper motor, the stepper motor suddenly stops.
The magnitude of the current will affect the torque. The larger the current, the greater the torque, but the greater the motor heat, so the current is generally adjusted to the minimum current when the torque is sufficient. If the motor generates a lot of heat in this case, you need to replace the motor with a large torque.