Debug steps for motion controller to control servo motor

Update:16-12-2020
Summary:

The motion controller is to control the operation of th […]

The motion controller is to control the operation of the motor: for example, the motor is driven by the stroke switch to control the AC contactor to realize the motor drags the object to run up to the specified position and then run down, or use the time relay to control the motor forward and reverse or rotate for a while Stop for a while and then transfer for a while and then stop.
The motion controller usually uses two instruction methods to control the servo motor: digital pulse and analog signal. The digital pulse mode is similar to the control mode of the stepper motor. The motion controller sends a pulse command signal of "pulse/direction" or "CW/CCW" type to the servo drive; the servo drive works in position control mode, and the position closed loop is controlled by the servo The drive is complete. Most Japanese servo and domestic servo products adopt this mode. The advantage is that the system is easy to debug and not easy to produce interference, but the disadvantage is that the response of the servo system is slightly slow.

General debugging steps for motion controller to control servo motor with analog signal

1. Initialization parameters
Before wiring, initialize the parameters.
On the controller: select the control mode; clear the PID parameters; turn off the default enable signal when the controller is powered on; save this state to ensure that the controller is in this state when it is powered on again.
On the servo drive: set the control mode; set the enable to be controlled externally; set the gear ratio of the encoder signal output; set the proportional relationship between the control signal and the motor speed. Generally speaking, it is recommended to make the larger design speed in servo work correspond to the control voltage of 9V. For example, the speed command gain parameter Pr50 of Panasonic MINASA4 series servo drives is used to set the motor speed corresponding to the 1V command voltage (the factory value is 500). If you only plan to make the motor work under 1000 revolutions, then set this parameter to 111 .

2. Wiring
Power off the controller and connect the signal line between the controller and the servo. The following connections are necessary: ​​the analog output line of the controller, the enable signal line, and the encoder signal line of the servo output. After rechecking the wiring for no errors, power on the motor and controller. At this time, the motor should not move, and it can be easily rotated with external force. If not, check the setting and wiring of the enable signal. Rotate the motor with external force and check whether the controller can correctly detect the change of the motor position, otherwise check the wiring and setting of the encoder signal.

3. Try direction
For a closed-loop control system, if the direction of the feedback signal is not correct, the consequences must be catastrophic. Turn on the enable signal of the servo through the controller. At this time, the servo motor should rotate at a lower speed, which is called "zero drift". Generally, there will be instructions or parameters to suppress zero drift on the controller. Use this command or parameter to see if the motor speed and direction can be controlled by this command (parameter). If it cannot be controlled, check the analog wiring and the parameter settings of the control mode. Confirm that a positive number is given, the motor rotates forward, and the encoder count increases; when a negative number is given, the motor rotates reversely, and the encoder count decreases. If the motor is loaded with a limited stroke, do not use this method. Do not give too much voltage to the test, it is recommended to be below 1V. If the directions are inconsistent, you can modify the parameters on the controller or motor to make them consistent.

4. Suppress zero drift
In the closed-loop control process, the existence of zero drift will have a certain influence on the control effect, and it is better to suppress it. Use the parameters of the controller or servo to suppress zero drift, and carefully adjust to make the motor speed approach zero. Since the zero drift itself has a certain degree of randomness, it is not necessary to require the motor speed to be absolutely zero.

5. Establish closed-loop control
Let go of the servo enable signal through the controller again, and input a smaller proportional gain on the controller. As for how large it is, it can only be based on feeling. If you are not at ease, input the larger the controller can allow. Small value. Turn on the enable signal of the controller and servo. At this time, the motor should be able to roughly act according to the motion command.
6. Adjust closed loop parameters
Fine-tuning the control parameters to ensure that the motor moves in accordance with the instructions of the controller is a work that must be done. This part of the work is more of experience and can only be omitted here.

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