Analysis of the cause of inaccurate positioning during the adjustment of the stepper motor - News - Global IC Trade Starts Here Free

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During the tuning process, it is found that the stepping motor positioning error is generally caused by the following reasons:

1. When the direction is changed, the pulse is lost. The performance is accurate in any direction, but the deviation is accumulated as soon as the direction is changed, and the more the number is biased more;

2, the initial speed is too high, the acceleration is too large, causing sometimes lost steps;

3. In the case of using the timing belt, the software compensates too much or too little;

4, the motor power is not enough;

5. The controller is disturbed and causes a malfunction;

6. The driver is caused by interference;

7, software defects;

The analysis of the above problems is as follows:

1) The general stepper driver has certain requirements for direction and pulse signal. For example, the direction signal is determined a few microseconds before the arrival of the first pulse rising edge or falling edge (different driver requirements), otherwise it will be The angle at which a pulse operates is opposite to the actual required steering. Finally, the fault phenomenon appears to be more and more biased, and the smaller the subdivision is, the more obvious the solution is. The solution mainly uses software to change the logic or delay of the pulse.

2) Due to the characteristics of the stepping motor, the initial speed cannot be too high. Especially when the load inertia is large, it is recommended that the initial speed be below 1r/s, so that the impact is small, and the same acceleration is too large. The rush causes the positioning to be inaccurate; there should be a certain pause time between the forward and reverse rotation of the motor, and if not, the overshoot will be caused by the reverse acceleration being too large.

3) Adjust the value of the compensated parameter according to the actual situation. (Because the elastic belt has a large elastic deformation, it needs to be compensated when changing the direction).

4) Properly increase the motor current and increase the driver voltage (note the optional driver) to select a motor with a higher torque.

5) The disturbance of the system causes the controller or the driver to malfunction. We can only find a way to find the source of interference, reduce its interference ability (such as shielding, increase the separation distance, etc.), cut off the propagation path, and improve its anti-interference ability. Common measures:

1 Replace the ordinary wire with a double-shield shielded wire. The signal wire in the system is separated from the high-current or large-voltage-changing wire to reduce the electromagnetic interference capability.

2 Use the power filter to filter out the interference wave from the power grid. Under the condition of permission, the power supply filter is added to the input end of each large power equipment to reduce the interference between the equipments in the system.

3 It is better to use the optical isolation device for signal transmission between the devices. Under the condition of permission, the pulse and direction signals are preferably transmitted by differential mode plus photoelectric isolation. Inductive load (such as electromagnetic relay, solenoid valve) plus RC absorption or fast bleeder circuit, inductive load can produce 10 ~ 100 times the peak voltage at the beginning, if the operating frequency is above 20KHZ.

6) The software does some fault-tolerant processing, and the interference is eliminated.