The working principle of DC servo motor is basically the same as that of ordinary DC motor. Electromagnetic torque is generated by the action of armature air flow and air gap flux to make the servo motor rotate. The armature control method is usually used to change the speed by changing the voltage while keeping the excitation voltage unchanged. The smaller the voltage, the lower the speed. When the voltage is zero, stop rotating. Because when the voltage is zero, the current is also zero, so the motor will not produce electromagnetic torque, neither will there be rotation phenomenon.
Dc servo motor is widely used in numerical control system, but DC servo motor also has some disadvantages: its brush and commutator are easy to wear; The maximum speed limit of the motor, the application environment limit; The structure is complicated, the manufacture is difficult and the cost is high.
Two-servo driver
1. Concept
The servo driver, also known as the servo amplifier or amplifier, is a device that outputs the pulse signal or analog signal input from the controller to the motor after internal calculation and amplification.
2. Structure and principle
The servo driver is composed of servo control unit, power drive unit and communication interface unit. The servo control unit includes position controller, speed controller, torque controller and current controller.
The servo driver can be divided into two modules, the power board and the control board, which are relatively independent in function. The power board is the strong current part, which includes two units, one is the power drive unit IPM used to drive the motor, and the other is the switching power supply unit to provide digital and analog power for the entire system. The control board is the weak current part, the control core of the motor and the operating carrier of the core control algorithm of servo drive technology. The control board outputs PWM/PFM signal through the corresponding algorithm, which is used as the drive signal of the drive circuit to change the output power of the inverter, so as to achieve the purpose of controlling the AC servo motor.