STUDY OF PROPORTIONAL CONTROL PROCESS OF INDUSTRIAL ROBOT SERVO DRIVE

This study is devoted to the development of a mathematical model and selection of a controller for a robot servo drive. Servos are widely used in welding and assembly robots to regulate the parameters of motion of the robot output link. The servo drive includes a DC motor with a reducer, feedback sensors to control the rotation angle, as well as a power supply and a converter. In the process of laser welding, the following are usually controlled: radiation power, focal length of the optical system, as well as the scanning speed, which is associated with the rotation frequency of the motor shaft. The main element of the servo drive, a DC motor, the mathematical model of which is based on the equations of electrical and mechanical equilibrium, is selected as the object of regulation. The angular velocity of the motor shaft is selected as the regulated output parameter. The task of the study is to ensure regulation of the angular position of the motor output link - the reducer shaft. The required quality indicators of the process are selected for the process of laser welding of metals with a thickness of 0.1 to 10 mm: the regulation time is no more than 1 second, the type of the resulting process is monotonous, without oscillations. Automatic control of the servo drive is based on the principle of subordinate control, in which the control loops of the torque, rotation speed and angular displacement of the motor shaft are sequentially switched on. Various principles can be used as a regulator in servo drives: proportional, integral, differential control. All of them have their advantages and disadvantages. In this paper, a study of a proportional regulator is carried out, the selection of coefficients and an assessment of their influence on the shape and quality of the transient process are performed. To solve the problem, a structural diagram is compiled and the transfer functions of the DC motor, position, speed and torque regulators, as well as the transfer functions of the feedback sensors are determined. The Matlab mathematical modeling environment is selected for the study. To assess the stability and quality of the transient process, the corresponding dependencies are obtained, the selection of regulator coefficients is made experimentally. By combining the regulator transfer coefficients, the authors achieved monotony of the transient process and the required response time. The study was conducted in two stages: at the first stage, external disturbance was not taken into account, at the second stage, an external effect equivalent to the torque of resistance was used, which simulates voltage surges on the motor windings. The proportional controller does not eliminate the static error, but by selecting the coefficients, quite acceptable results can be achieved