The characteristics and maintenance techniques of servo drives

The characteristics of servo drives
1. The servo driver software program mainly includes the main program, interrupt service program, and data exchange program.
2. The main program of the servo driver is mainly used to complete system initialization, LO interface control signals, and the setting of registers in various control modules within the DSP.
3. After all the initialization work of the servo drive is completed, the main program enters a waiting state and waits for the occurrence of interrupts, in order to adjust the current loop and speed loop.
4. Servo driver initialization mainly includes initialization of the DsP core, setting of current and speed loop cycles, PWM initialization, four M startup, ADc initialization and startup, QEP initialization, initial position initialization of vector and permanent magnet synchronous motor rotor, multiple servo motor phase current sampling, calculation of phase current zero offset, current and speed P adjustment initialization, etc.
5. PWM timing interrupt programs are sometimes used to sample and calibrate the current ia and ib of the A and B phases of the Hall current sensor, as well as calculate the rotor magnetic field orientation angle based on the principle of magnetic field orientation control. After that, PWM signals are generated to control the position and speed loops.
6. The power driven protection interrupt program is mainly used to detect the fault output of intelligent power modules.
7. The zero pulse capture interrupt program of the photoelectric encoder can accurately capture the feedback zero pulse of the encoder, thereby obtaining the correction value of the vector transformation orientation angle of the AC permanent magnet synchronous motor.
8. The data exchange program mainly includes communication programs with the upper computer, EEPRoM parameter reading, digital display programs, etc. The storage controller keyboard value for parameters.

Servo driver maintenance
1. When the oscilloscope checked the current monitoring output terminal of the driver, it was found that it was all noise and could not be read.
Fault cause: The current monitoring output terminal is not isolated from the AC power supply (transformer).
Solution: You can use a DC voltmeter to detect and observe.
2. The motor runs faster in one direction than in another.
Cause of malfunction: The phase of the brushless motor is incorrect.
Processing method: Detect or check the correct phase.
Cause of malfunction: When not used for testing, the test/deviation switch is set to the testing position.
Solution: Set the test/deviation switch to the deviation position.
Cause of malfunction: The position of the deviation potentiometer is incorrect.
Solution: Reset.
3. Motor stall.
Cause of malfunction: The polarity of the speed feedback is incorrect.
Handling method:
a. If possible, turn the position feedback polarity switch to another position. (Some drives can)
b. If using a speedometer, swap the TACH+and TACH - on the drive and connect them.
c. If using an encoder, swap and connect ENC A and ENC B on the drive.
d. If in HALL speed mode, swap HALL-1 and HALL-3 on the drive, and then swap and connect Motor-A and Motor-B.
Cause of malfunction: During encoder speed feedback, the encoder power supply lost power.
Solution: Check and connect the 5V encoder power supply. Ensure that the power supply can provide sufficient current. If using an external power source, ensure that the voltage is connected to the driver signal ground.
4. The LED light is green, but the motor does not move.
Cause of malfunction: One or more motors in different directions are prohibited from operating.
Solution: Check the+INHIBIT and - INHIBIT ports.
Cause of malfunction: The command signal is not grounded to the driver signal.

5. After powering on, the LED light of the driver does not light up.
Cause of malfunction: The power supply voltage is too low, lower than the minimum voltage requirement.
Solution: Check and increase the power supply voltage.
6. When the motor rotates, the LED light flashes.
Fault cause: HALL phase error.
Solution: Check if the motor phase setting switch (60/120) is correct. Most brushless motors have a 120 phase difference.
Cause of malfunction: HALL sensor malfunction
Solution: When the motor rotates, check the voltage of Hall A, Hall B, and Hall C. The voltage value should be between 5VDC and 0.
Processing method: Connect the command signal ground to the driver signal ground.

Source: Internet