Dc Servomotor Essay

CHAPTER 2
MODELLING OF DC SERVOMOTOR FOR POSITION CONTROL
2.1. INTRODUCTION
An electric motor is an electromechanical device that converts electrical energy to mechanical energy. This mechanical energy is used for rotating a pump impeller, fan or blower, driving a compressor, lifting materials etc. DC motors are especially used in applications that require high starting torque or smooth acceleration over a wide speed range.
A dc servo motor which is usually a dc motor of low power rating is used as an actuator to drive a load. A dc servo motor has a high ratio of starting torque to inertia and hence they make a faster dynamic response. The speed torque characteristic of this motor is flat over a broad range, as the armature reaction is negligible. Wound field dc motors can be controlled by either controlling the armature voltage or controlling the field current.
In larger systems where a powerful motor is required that shows an increasing price of the system in such case servomotor is advantageous. A dc servomotor used for control applications in robotic manipulators, tape transport mechanism, disk drives, machine tools, servo-valve actuators etc. requires precise positioning as well as speed control. In order to achieve

This model utilizes differential equations for the electrical system, mechanical system and the interconnection between them. As reference we consider armature controlled dc servomotor as shown in Figure 2.1. A simple mathematical relationship between the shaft angular position ‘θ’ and voltage input ‘V_a’ to the dc motor may be derived from physical laws. DC servomotor can be considered as SISO system. Therefore, complications related to multi-input system are discarded. In dc servomotors the current in the field coil and the armature winding are independent. So, these motors have excellent speed and position