Causes and solutions to the problem of motion control deviation
Release Time：2019-12-17 11:35:59
Deflection is one of the common problems faced by equipment manufacturers who use stepping or servo motors in the process of equipment installation, debugging and use. The deviation may be caused by improper mechanical assembly, mismatching of control system and driver signal, electromagnetic interference in equipment, mutual interference of equipment in workshop or improper handling of ground wire during equipment installation.
From many application cases, the most common deviation reasons and countermeasures are extracted and sorted out to help the debugging personnel of the equipment manufacturers quickly locate the problems, take various appropriate measures to improve the anti-interference of the equipment, and ensure the normal operation of the equipment for the correct grounding.
Q: do reciprocating motion, more and more (less) forward
Possible cause ①: wrong pulse equivalent
Solution: before leaving the machine, draw a square of the largest possible size with the machine, then measure the actual size with a ruler, compare the ratio between the actual size and the setting size of the control card, and then add it to the control card operation. After repeated three times, a more accurate value will be obtained.
Possible cause ②: the trigger edge of the pulse instruction conflicts with the level conversion sequence of the direction instruction
Solution: the control card (PLC) software engineer will advance the direction signal. or the driver Application Technician changes the pulse edge counting method.
Q: during the movement, the motor shakes at the fixed point. After passing this point, it can operate normally, but it takes a short distance
Possible cause: mechanical assembly problem
Solution: 1. Check whether the mechanical structure is blocked due to the large friction resistance or the non parallel slide rail. 2. The torque of stepping motor is not enough. Due to the requirement of speed increase or load increase of the end customer, the motor that could meet the requirement is not enough in high-speed torque, thus the phenomenon of high-speed section locked rotor occurs. The solution can be to set a larger output current through the driver or to increase the supply voltage within the allowable voltage range of the driver, or to replace the motor with a larger torque.
Q: the motor does not move back and forth in place and the offset is fixed
Possible cause: belt clearance
Solution: if the motion control card has the function of belt reverse clearance compensation, it can be used; or tighten the belt.
Q: the cutting and drawing tracks are not coincident
Possible causes ①: excessive inertia
Solution: increase the y-axis deceleration ratio, and use the Notch function to improve the rigidity of the servo driver to solve the problem.
Possible cause ②: the coincidence of knife and nozzle is not adjusted properly
Solution: modify the cutter and nozzle position compensation parameters.
Q: draw a circle into an ellipse
Possible cause: the two axes of XY axis platform are not vertical
Solution: adjust the perpendicularity of x-axis and Y-axis of gantry to solve the problem.
Q: the deviation occurs irregularly during operation. The deviation is accidental and the deviation is uncertain
Possible causes ①: Motor deviation caused by interference
Solution: if the interference occurs frequently, the oscilloscope can be used to monitor the pulse frequency to determine the time of the interference and then determine the interference source. Removing or keeping the pulse signal away from the interference source can solve part of the interference. If the interference occurs accidentally, or it is difficult to determine the location of the interference source or the electrical cabinet is fixed and hard to move, the following measures can be considered to solve the problem:
① driver grounding,
② replace the twisted shield wire with the pulse wire,
③ 103 ceramic capacitor filter (pulse frequency is less than 54khz) is connected in parallel at the positive and negative ends of the pulse,
④ pulse signal sleeve magnetic ring,
⑤ add filter at the front of driver and controller power supply.
Possible cause ②: narrow pulse in pulse train
Solution: find out the cause of this problem of the controller, whether it is the problem of pulse interface or the problem of software algorithm.
Possible cause ③: loose mechanical structure
Solution: for key parts and structural screws with large force, elastic pad must be used, and screw or jackscrew should be coated with screw glue. The motor shaft and coupling shall be connected with keyway as far as possible.
Possible cause ④: filter capacitance is too large
Solution: when the filter capacitor is added, the pulse frequency needs to be calculated and the maximum passing pulse frequency must be ensured to meet the requirements.
Possible cause ⑤: the maximum pulse frequency of PLC or motion control card is not high enough
Solution: if the maximum pulse frequency of the upper computer is limited, in order to ensure the speed, the driver subdivision can be properly reduced to ensure the motor speed.