Motor Drive Circuits

Abstract

Figure 4.1a shows a block diagram which illustrates a typical closed-loop computerized motor control circuit; a computer provides a signal for the motor controller, which generates an appropriate motor control voltage (or current) to the drive motor according to output coordinates which are derived from a control algorithm. In this closed-loop circuit, a tachogenerator (TG) is used to obtain a fast feedback (first derivative feedback), which enhances the stability and dynamic quality. The encoder E is used to deliver position feedback to a computer in order to provide automatic motion control according to a given control algorithm. A motor torque transmission with a coaxial clutch CC eliminates mechanical problems which can occur in real devices due to inaccurate coaxial alignment between the motor output axes and a gear box axis G, which basically is used to obtain a required speed and torque for a given load L. The basic kinematic concept of the coaxial clutch CC is illustrated in 3D as shown in Fig. 4.1b. According to the drawing, a master disc (1) has a diametrical slot to join a rectangular bar (2) to a middle disc (3), which also has a second orthogonal bar (4) on the other side which joins a corresponding slot (5) to a third slave disc (6), which is connected to a gear axis.