Reasons And Solutions For Inaccurate Positioning Of Stepper Motors

- Jul 20, 2018-

Reasons and solutions for inaccurate positioning of stepper motors

Why does stepper motor  position inaccurate? In response to such questions, this paper summarizes the reasons for the inaccurate positioning of stepping motors and proposes corresponding solutions.

One. When the direction is changed, the pulse is lost and the lead to inaccurate position.

When the direction is changed, the pulse is lost, which is consistent in any direction, but the deviation is accumulated as soon as the direction is changed, and the more the number is biased more;

Solution: The general stepper driver has certain requirements for direction and pulse signal, such as: the direction signal is on the rising or falling edge of the first pulse (different driver requirements are different)the first few microseconds are determined, otherwise there will be a pulse running at the opposite angle to the actual required steering. Finally, the fault phenomenon is more and more biased, and the smaller the subdivision, the more obvious, the solution is to use software to change the logic or delay of the pulse.

Two, the initial speed is too high, the acceleration is too large, causing sometimes lost

Solution: Due to the characteristics of the stepper 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 acceleration is too large.

The impact on the system is also large, and it is easy to overshoot.

Three, the environmental interference caused by the controller or the driver's malfunction caused the positioning is inaccurate

Solution: Increase the motor current appropriately and increase the drive voltage (note the optional drive) to select a motor with a higher torque.

The interference of the system causes the controller or the driver to malfunction. We can only find a way to find the source of the interference, reduce its interference ability (such as shielding, increase the separation distance, etc.), cut off the transmission route, and improve self-interference resistance, common measures as following:

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. In an inductive load (such as

Electromagnetic relays and solenoid valves) are equipped with RC absorption or rapid bleeder circuits at both ends. The inductive load can generate 10~100 times of peak voltage at the beginning, if the operating frequency is above 20KHZ.

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