Servo Motor Basics & Working Principle
Servo motor basics
What is a servo motor? Servo motor is the motor which controls mechanical components operation in servo system. Servo motor can convert voltage signal to torque and speed, then to drive the control object. The control speed and position accuracy is very high. In auto control system, servo motor can response rapidly as executing component, convert the receiving electrical signal to angular displacement or angular velocity output of motor axis. The main feature is, when signal voltage is zero and no self-rotation, rotation speed will descend at even speed along with the torque increasing. Servo motor has 2 types, DC servo motor and AC servo motor.
Servo motor working principle
How does a sevo motor work? Servo motor mainly depends on pulse for fixing position, when it receives 1 pulse, then rotates for 1 pulse relative angle to realize displacement. Servo motor has function to send out pulse, therefore, servo motor would send out relative quantity pulse when rotating a certain angle. Then, it acts in cooperation with servo motor received pulse, or called closed loop. In the case, system knows the pulse quantity sent to servo motor, and the pulse received in return, then can control the motor operation accurately, and realize accurate position fixing, up to 0.001mm. The rotor inside servo motor is permanent magnet, U/V/W 3 phase electricity controlled by driver forms electromagnetic field, rotor rotates under action of magnetic field, simultaneously the coder inside motor gives signal back to driver, driver compares the feedback value and target value, adjust rotating angle of rotor.
Servo motor selection
- Calculate load inertia. Refer to inertia matching, take ATO servo motor as example, inertia matching of some products can reach up to 50 times. But actually the smaller the better, it is better for accuracy and response speed. If load inertia and motor inertia not matching each other, then the system response would be very poor.
- Obversion of Load torque on motor axis and calculation of acceleration and deceleration torque.
- Requirement of accuracy. Used for selecting coder accuracy of servo motor, as servo motor accuracy depends on rotating coder (starting from coaxial) accuracy.
- Speed range. Low speed normally less than 2000RPM, large torque motor less than 1000RPM, high speed could reach up to 5000RPM, DC servo motor can reach up to 10000-20000 RPM. The rated speed of ATO AC servo motors are 1000RPM~3000RPM.
- Control method. Mostly are position control, diversified and intelligent control method. Position, rotating speed and torque control method.