Design, Comparison, and Evaluation of Controllers for Direct Current Servomotors

Design, Comparison, and Evaluation of Controllers for Direct Current Servomotors

Claudio Urrea (Universidad de Santiago de Chile, Chile) and Luis Valenzuela (Universidad de Santiago de Chile, Chile)
Copyright: © 2019 |Pages: 20
DOI: 10.4018/978-1-5225-5709-8.ch019


The results and comparison of controller performance based on fuzzy logic and neural networks with the purpose of improving the performance of PID controllers currently used in servomotors is presented. The performance comparisons will be made with no load and with load (consisting of a robotic type rotational link). The results show that as the number of links in a robot increases, the precision of the movements desired from it decreases, affecting the tasks that require a high degree of precision, so the design of controllers like those presented in this chapter is required. This work is the basis for implementing improvements in the performance of DC servomotor control systems in general.
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Structure Of A Dc Servomotor

This section describes how a DC servomotor operates, regardless of whether it is of the analog or digital type. A servomotor is composed mainly of three elements: a DC motor; a position sensor to measure the rotational displacement; and an electronic amplifier or servo amplifier consisting of a set of microprocessors and power electronics that is in charge of coupling and conditioning to the motor the impedance and low power voltage signal coming from a digital system (Reyes, 2011).

Figure 1 shows a schematic representation of a servomotor. Physically, it is composed of a DC motor; a gear train to reduce the speed and increase the torque on the axle; a potentiometer connected with the output axle to know the position; and a control circuit that converts a PWM signal into voltage, comparing it with the feedback position and then amplifying it to activate an H bridge to produce a turn at a given speed (Urrea & Kern, 2014).

Figure 1.

Schematic representation of a servomotor

Source: Urrea & Kern, 2014

Modeling An Unloaded Servomotor

The DC motor is a power actuator device that provides energy to a load. The DC motor converts electric energy (DC) into mechanical rotational energy. A large part of the torque generated in the motor's rotor (included) is available for moving external loads. Due to characteristics such as high torque, speed controllability over a wide range, portability, well behaved couple-speed characteristics, and adaptability to diverse methods, DC motors are used in general in numerous control applications, including robotic manipulators, belt transport mechanisms, disc units, and machine tools (Dorf & Bishop, 2005). Figure 2 shows a diagram of a DC motor.

Figure 2.

Schematic representation of a DC motor

Source: Urrea and Kern, 2014

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