Servo Motor Closed Loop Control System

A closed loop motion control system consists of a motor amplifier motion controller and feedback sensor.

Servo motor closed loop control system.

A motion control system is a collection of components put together in such a way that creates movement to a specific position velocity or acceleration. Servo motors are part of a closed loop system and are comprised of several parts namely a control circuit servo motor shaft potentiometer drive gears amplifier and either an encoder or resolver. A desired or reference angle is received 0 t and compared to the current angle of the servo horn as measured by a potentiometer or t. This method is commonly used in servo systems.

A linear servo is a motor that creates motion in a linear fashion typically through driving a lead screw that extends and retracts a tube or shaft and has feedback to make a closed loop system. A servo motor is a self contained electrical device that rotate parts of a machine with high efficiency and with great precision. Stepper motor systems using closed loop control represent a small percentage of stepper motor applications but if loss of position could be catastrophic to the application yet the system requires high torque at low speed relatively simple architecture and relatively low cost compared to a true servo motor system a closed loop stepper might be the most appropriate solution. Servo drives also called amplifiers in the motion control industry take a command signal for position velocity or current and adjust the voltage and current applied to the servomotor based on closed loop feedback in fact a servo drive is just one element of a motion control system which includes a servo motor the drive controller and some type of feedback element.

The feedback is typically from either a potentiometer or an encoder. A servo motor depicted in figure 1 is an example of a closed loop control system. This assembly may in turn form part of another servomechanism. A servomotor is a specific type of motor that is combined with a rotary encoder or a potentiometer to form a servomechanism.

The term is open loop vs closed loop watch and discover. Servo motors also move on receipt of a command signal from their controller. In contrast to the open loop operation of stepper motor systems servo motors are closed loop systems with built in encoders that continuously communicate back to the controller which makes any needed adjustments to ensure the target position is reached. The difference between these signals 0e t is then used by a control system c s to control a plant g s.

A potentiometer provides a simple analog signal to indicate position while an encoder provides position and usually speed feedback which by the use of a pid controller allow more precise control of position. The encoder detects the rotation angle of a feed screw ball screw and provides it as feedback of the machine workpiece or table travel. Typically an encoder or other detector is attached behind the motor. It is faster and has better positioning precision than an open loop.