Research On Loading Control Of Pneumatic 3-UPU Parallel Robot Based On Active Disturbance Rejection

With the rapid development of robotics engineering,the technological level of robots has become an important indicator of the national high-tech level and industrial automation level.Among the widely used types of robots,the 3-translational robot is a type of parallel robot with low degrees of freedom.It is highly favored for its simple structure,easy assembly,and low cost.At the same time,it also has high rigidity and load-bearing capacity,making it have good application value and broad application prospects in industrial production applications.In practical work,the control difficulty of the pneumatic 3-UPU parallel robot is relatively high,mainly due to the strong nonlinearity of its driving system and the uncertainty of the load,making it difficult to achieve accurate force control.In addition,the robot system is also affected by external interference,which can also affect the control accuracy of the robot.Therefore,how to solve the problems of robot load uncertainty and external interference has become a research hotspot in the control of pneumatic 3-UPU parallel robots.This article uses the precise control of nonlinear actuators as a means to design a three-dimensional force loading device for a pneumatic 3-UPU parallel robot based on active disturbance rejection,which is used to apply time-varying multi-dimensional loads to the target.The device has fast response,high accuracy,and strong adaptability to various disturbance effects.First,according to the vector superposition principle and Newton Raphson method,the kinematics characteristics of the loading device are analyzed,and the kinematics inverse solution of the robot is solved.Based on the screw theory,the static mapping between the three-dimensional output force of the moving platform and the driving force of the cylinder is derived.Secondly,under certain assumptions,the second order mathematical model of the pneumatic 3-UPU parallel mechanism based on proportional flow valve and metal clearance seal cylinder is established by using the valve port flow equation and the mathematical analysis of the pressure model in the cylinder.During the modeling process,a relatively accurate reference model was provided for the control algorithm.Once again,based on the basic idea of active disturbance rejection control,an active disturbance rejection control algorithm was gradually designed for the established drive system model,and the controlled object model was incorporated into the controller.By comparing and simulating with traditional PID,the effectiveness of the designed controller was verified.At the same time,a series of comparative simulation experiments were designed to analyze the superiority of the designed control algorithm,which is completely unknown to the controlled object model.Finally,the active disturbance rejection control algorithm was applied to the actual control of a 3-UPU parallel robot,achieving dynamic loading force control of the robot.Experiments show that the controller has good robustness to various unknown disturbances existing in the nonlinear system,the steady-state control accuracy is less than 2N,and the tracking mean square deviation of dynamic sine wave(0.2Hz)is less than 10.5N.