Design Of Control System Of PLC Based On 3DOF Mechanical Arm

Robot is a category of highly flexible and automatic mechanical system that may engage in various jobs in place of human beings. Over the past decades, the development of robots has been increasingly optimized. Covering a wide range of fields, robots are widely used. They may be seen in different fields regardless of aerospace development, moon rovers, deep-sea detectors, exploitation of offshore petroleum, robotic arms of space shuttle, micro-machines for operations or monitor signs monitor. Their military purposes are changing, ranging from machines for bomb disposal and landmine eradication to unmanned aerial vehicles and chariots. Someone has even predicted wars will be possibly wars among robots like star wars in the future. Some innovations have appeared in industries, agriculture, genetic and biology industries, medicine, cultural industry, telecommunication and energy development due to emergence of numerous robots. As one of important fields for development of new technologies over the past few years, it is a comprehensive high technology integrating various emerging electronic and mechanical technologies. As important parts of robots, mechanical arms are automatic mechanical devices that are used most widely in practices in the field of robot technology. With the constant development of control theories and technologies, many different control strategies have been developed based on trajectory planning and tracking for a variety of mechanical arms which belong to a category of robots. In controlling mechanical arms, PLC is frequently used, so it is of great significance for the development of robots by examining control programs of mechanical arms.In order that mechanical arms may determine motions and fulfill predetermined tasks, it is necessary to explore their solutions to the inverse kinematics problems to determine the value of all variables input into joints. Firstly, an introduction was made to robot kinetics. By establishing kinetics equations and solving inverse kinetics equations, simpler analytical methods for determining angles of joints were found out. Motion trajectories of 3DOF mechanical arms were simulated according to powerful functions of MATLAB in computation and drawing, so as to validate if the forward kinetics models and the solutions to the inverse kinetics problems were correct. The solutions to inverse kinetic problems were used for precise positioning and motion planning at the ends of mechanical arms. The simulation results intuitively reflected position of joints at different moments, coordinates at each interpolation point and angles of joints, so a trajectory plan was made for the robots. Based on these data, Omron series CP1H-X40DR-A PLC was selected and CJ1W-NC113 position control module was used. According to the requirements for the module, parameters such as number of pulses, time of acceleration/deceleration and speed as calculated before were set between every two joints. Meanwhile, the I/O addresses were assigned. Subsequently, trajectories controlled by a step motor at the ends of three-rod mechanical arms were determined by programming.