Ac Servo Motor Driver Circuit Diagram

The “servo” is both the servomotor and servo amplifier. ▫ Servo Amplifier: A device. CNC Controller. (Speed Control). General Motion. (Torque Control). Typical Power Circuit (Simplified Diagram).

Servo motors are made for precise control of angular or linear position, Velocity and acceleration. These servo motors are called as Rotary actuator or linear actuator. Servos may contain sensor for position feed back and signal input for position control. Servo motors are available in different size and voltage ratings. All servo motors are works in the same way but depends on the size and specifications output volume varies.
Here sub micro size servo motor is taken as a target device and we developed servo motor driver circuit for that motor. Servo motors are widely used in different types of applications and suitable for movement or rotation based mechatronic needs.

Circuit Diagram

Construction & working

Every servo motors will have three terminals, one for positive supply, another for ground supply and other one for position control signal input.

This circuit is designed to give PWM (Pulse Width Modulation) signal output by using this different duty cycle PWM pulse, we can control the servo motor rotation and position.

This illustration given to understand the servo rotation based on PWM signal. Consider the signal with 20ms period and width of HIGH pulse duration 1ms (min) and 2ms (max), depends on the HIGH pulse signal time duration servo motor rotation gets change.

Here the timer IC 555 employed as a astable multivibrator and it produce pulse at output with two different pulse duration, we know the output pulse time in 555 is depends on the timing Resistor and timing Capacitor.

High pulse time TH = 0.693*(RA + RB)*C

Low pulse time TL = 0.693*RB*C

NOTE:- Here RA is R1 Resistor and RB is either R2 or R3 depends on the button (SW) pressed, its for this circuit only.

When the switch SW1 close, the 555 timer IC produce long duration High pulse and servo rotates in right direction. When the switch SW2 close, the 555 timer IC produce short duration High pulse and servo rotates in left direction.

Note:- Depends on the output pulse duty cycle, servo motor rotation direction and speed gets change.

Servo Motor are also called Control motors. They are used in feedback control systems as output actuators and does not use for continuous energy conversion. The principle of the Servomotor is similar to that of the other electromagnetic motor, but the construction and the operation are different. Their power rating varies from a fraction of a watt to a few hundred watts.

The rotor inertia of the motors is low and have a high speed of response. The rotor of the Motor has the long length and smaller diameter. They operate at very low speed and sometimes even at the zero speed.The servo motor is widely used in radar and computers, robot, machine tool, tracking and guidance systems, processing controlling, etc.

Applications of the Servo Motor

The power rating of the servo motor may vary from the fraction of watts to few hundreds of watts. The rotor of servo motor have low inertia strength, and therefore they have a high speed of inertia. The Applications of the Servomotor are as follows:-

• They are used in Radar system and process controller.
• Servomotors are used in computers and robotics.
• They are also used in machine tools.
• Tracking and guidance systems.

Classification of Servo Motor

They are classified as AC and DC Servo Motor. The AC servomotor is further divided into two types.

• Three Phase AC Servo Motor

DC Servo Motor

DC Servo Motors are separately excited DC motor or permanent magnet DC motors. The figure (a) shows the connection of Separately Excited DC Servo motor and the figure (b) shows the armature MMF and the excitation field MMF in quadrature in a DC machine.

This provides a fast torque response because torque and flux are decoupled. Therefore, a small change in the armature voltage or current brings a significant shift in the position or speed of the rotor. Most of the high power servo motors are mainly DC.

The Torque-Speed Characteristics of the Motor is shown below.

As from the above characteristics, it is seen that the slope is negative. Thus, a negative slope provides viscous damping for the servo drive system.

AC Servo Motor

The AC Servo Motors are divided into two types 2 and 3 Phase AC servomotor. Most of the AC servomotor are of the two-phase squirrel cage induction motor type. They are used for low power applications. The three phase squirrel cage induction motor is now utilised for the applications where high power system is required.