PLC-based DC servo system for industrial robot joints

Abstract: Leveraging the high reliability, ease of programming and maintenance, and small size of Programmable Logic Controllers (PLCs), this paper describes the development of a PLC-based DC servo system for industrial robot joints. This system is applied to a circulating reversible speed control system to control the forward and reverse rotation of the motor, thereby achieving servo control of the robot joints. Its advantage lies in the fact that changing the motor's forward and reverse rotation does not require altering the wiring structure, making the servo control of the industrial robot joints simpler, more reliable, and more stable.

Keywords: PLC; reversible circulating speed control; industrial robot joint; DC servo system

1 Introduction

With the development of modern science and technology, PLCs have been widely used in industrial control microcomputers.

Currently, industrial robot joints are mainly controlled by AC servo systems. This study applies the mature, easy-to-program, highly reliable, and compact SIEMENS S-200 programmable controller to a controllable circulating current reversible system to develop a DC servo system for robot joints, which is used for servo control of industrial robot joints.

2. DC Servo System for Industrial Robot Joints

The joints of industrial robots are driven by DC servo motors. The forward and reverse rotation of the motors is controlled by a circulating reversible speed regulation system to achieve servo control of the joints of industrial robots.

2.1 Control System Structure

The system uses a SIEMEN S7-200 PLC, plus a D/A digital-to-analog converter module, to convert the PLC digital signal into an analog signal. This analog signal is then driven by the BT-I variable current speed control system (which mainly consists of a speed regulator ASR, a current regulator ACR, a circulating current regulator ARR, a positive trigger GTD, a negative trigger GTS, and a current feedback TCV) to drive the DC motor and make the robot joints move according to the control requirements.

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