Stepping motors are often used for precise positioning, so it is very important to ensure that the motor does not lose its step. The stepper motor can control the position and speed of the motor open-loop according to the pulse number and pulse frequency, and it is more and more widely used in the field of automation control.

However, since the stepper motor is not a closed-loop control, the selection or improper use of the stepper motor will easily cause the stepper motor to lose steps, that is, the stepper motor does not reach the position it should reach according to the instructions. So, what is the reason for stepper motor out of step? What countermeasures can be taken to avoid losing steps? There are many reasons for the stepping motor out of step. In the actual application process, it is necessary to adopt the elimination method to analyze one by one to find out the real cause of the stepping out. Generally, the reasons for the stepping motor out of step are as follows:

1. The working torque of the stepper motor itself is not enough, and it does not have enough ability to drive the load;

Since the dynamic output torque of the stepper motor decreases with the increase of the continuous operating frequency, any operating frequency higher than this frequency will cause out-of-step. You can calculate the torque of the load: refer to the frequency diagram of the stepper motor to see if the stepper motor has enough torque to drive the load at the corresponding speed. You can change to a stepper motor with a large torque at the corresponding working speed for comparative testing.

There are three solutions to this problem: a. Properly increase the drive current within the rated current range to increase the electromagnetic torque generated by the stepping motor; b. When the torque in the high frequency range is insufficient, properly increase the drive circuit c. Replacing a stepping motor with a large torque can also reduce the torque that the stepping motor needs to overcome. The method is to appropriately reduce the operating frequency of the motor to increase the output torque of the motor.

2. The stepping motor starts out of step

Due to the inertia of the stepper motor itself and the load it carries, when the acceleration time is too short, steps will be lost. If the deceleration process of the stepper motor is not enough, it will lose the step.

For this reason, you can set a reasonable acceleration time to make the motor rise steadily from a low speed to the required speed; in addition, it is generally recommended that the moment of inertia of the load should not be greater than 10 times the moment of inertia of the stepper motor, otherwise the acceleration and deceleration process will be longer.

3. The power supply power of the stepping motor is not enough to cause the input power of the stepping motor to be insufficient and cause out of step;

  When the stepper motor starts, the current will reach about 1.6 times of the rated current. If the power of the power supply is not enough, the effective current in the motor will be too low, so that the load cannot be driven. Therefore, it is recommended to leave more than 30% of the power supply in general.

4. The drive voltage of the stepper motor is not enough or the set drive current is too low;

  When the stepper motor needs to start quickly or run at high speed, the driving voltage required is relatively high, and the set value of the working current must be large enough, otherwise it is easy to cause the motor to lose its step.

5. The driver or controller is interfered by other signals;

  Change another type of driver for comparison to determine whether the signal is interfered. Or try to see if there is any change in motor B when controlling the movement of motor A, so as to judge whether the controller is interfered by the signal.

6. The resonance of the stepping motor system causes the load capacity of the stepping motor to drop, which leads to the motor out of step;

  When the stepper motor is in continuous operation, if the frequency of the control pulse is equal to the natural frequency of the stepper motor, resonance will occur. When the resonance phenomenon occurs, the stepper motor and its system have obvious noise and vibration. If the relevant phenomenon will obviously reduce or disappear when the speed increases or decreases to a certain range, it can basically be judged that it is a resonance problem. Since the resonance phenomenon of the stepper motor comes from its basic structure, it cannot be completely eliminated. In addition, resonance is also related to load conditions. Generally, the resonance can be reduced by driving the motor in half-step or micro-step mode; or choose a driving frequency higher than the resonance frequency to drive the motor to avoid resonance. Or choose a stepper motor with appropriate parameters; improve the performance of the driver or use physical methods such as shock absorbers to reduce vibration.

7. The signals of the driver and the controller do not match;

If the signals from thestepper motor driver and controller do not match, the offset in position will increase fairly evenly over time. You can change the signal identification method of the driver or controller, so that the two match and match.

8. The backlash of the synchronous wheel or the gearbox or the backlash error of back and forth is not compensated in the program or the compensation value is wrong; due to the accuracy of the synchronous wheel or the gearbox, there will be a certain error accumulation, so it needs to be corrected in the control program Make reasonable compensation.

9. There is a problem with the control program itself; it is not uncommon for the control program to cause out of sync, and it is necessary to check whether there is a problem with the control program.

In recent years, closed-loop stepper motors have become popular. It is also a solution to achieve complete control of stepper motors through closed-loop control, but the cost will be higher. Now some stepping motor driver chips can output the stepping motor out of step signal according to the abnormal change of the stepping motor's instantaneous current.