Industrial control technology requires understanding the basic steps of servo motor debugging. Motion controllers typically use two command methods to control servo motors:
1. Digital Pulse
This method is similar to the control method of stepper motors. The motion controller sends pulse command signals of the type "pulse / direction" or " CW/CCW " to the servo driver; the servo driver operates in position control mode, and the position closed loop is completed by the servo driver. Most Japanese and domestic servo products adopt this mode. Its advantages are simple system debugging and less susceptibility to interference, but its disadvantage is that the servo system response is slightly slower.
2. Analog signal
In this mode, the motion control system sends an analog voltage command of +/-10V to the servo drive , while simultaneously receiving position feedback signals from position detection elements such as motor encoders or linear encoders. The servo drive operates in speed control mode, and the position closed loop is completed by the motion controller. Most servo products in Europe and America adopt this operating mode. Its advantage is fast servo response, but its disadvantages include sensitivity to field interference and slightly more complex debugging.
The following are the general debugging steps for a motion controller to control a Fuji servo motor using analog signals:
Initialize parameters: Before wiring, initialize the parameters. On the control card: Select the control mode, clear the PID parameters, and ensure the enable signal is off by default when the control card is powered on. Save this state to ensure the control card is in this state when powered on again. On the Fuji servo motor: Set the control mode, enable external control, encoder signal output gear ratio, and the ratio between the control signal and the motor speed. Generally, it is recommended to use a control voltage of 9V corresponding to the maximum design speed of the Fuji servo motor .
Wiring: Power off the control card and connect the signal cables between the control card and the Fuji servo motor. The following cables are mandatory: the analog output cable of the control card, the enable signal cable, and the encoder signal cable output from the Fuji servo motor. After verifying that the wiring is correct, power on the servo motor and the control card. At this point, the motor should not move and can be easily rotated with external force. If this is not the case, check the enable signal settings and wiring. Rotate the motor with external force to check if the control card can correctly detect changes in motor position. Otherwise, check the encoder signal wiring and settings.
Test Direction: For a closed-loop control system, if the direction of the feedback signal is incorrect, the consequences will be disastrous. Enable the Fuji servo motor via the control card. The servo should rotate at a low speed; this is the so-called zero drift. Control cards usually have instructions and parameters to suppress zero drift. Use these instructions or parameters to see if the servo motor's speed and direction can be controlled by them. If not, check the analog wiring and control mode parameter settings. Confirm that a positive value causes the servo motor to rotate forward and the encoder count to increase; a negative value causes the motor to rotate backward and the encoder count to decrease. If the motor is under load and has limited travel, do not use this method. Do not apply excessive voltage during testing; it is recommended to keep it below 1V. If the directions are inconsistent, modify the parameters on the control card or the Fuji servo motor to make them consistent.
Suppressing zero drift: In closed-loop servo control, the presence of zero drift can affect the control effect. It is best to suppress it. Carefully adjust the zero drift suppression parameters using the control card or Fuji servo, and use the motor speed close to zero. Since zero drift itself has a certain degree of randomness, it is not necessary to require the servo motor speed to be absolutely zero.
Establish closed-loop servo control: Re-enable the Fuji servo motor enable signal through the control card, and input a small proportional gain on the control card. As for how small is considered small, you can only rely on your intuition. If you are really unsure, input the minimum value that the control card can allow. Turn on the enable signals of the control card and the servo motor. At this point, the phone should be able to roughly perform actions according to the motion commands.
Adjusting closed-loop parameters: Fine-tuning the control parameters to ensure that the Fuji servo motor moves according to the control card's instructions is a necessary task, and this part relies more on experience, so it can only be omitted.
