Design And Kinematical Characteristics Research Of Three-degree-of-freedom Spherical Wrist Directly Driven By Hydraulic System

The wrist unit is an indispensable part of the overall mechanism of the robot.The mechanical performance of the wrist unit directly affects the performance and operational capability of the robot end effector.Aiming at the problems that mainstream electric-driven wrists rely heavily on high-precision reducers and long-time work load motor heating serious,as well as the demand for explosion-proof full-hydraulic manipulators in coal mines.This article designs a new type of three-degree-of-freedom spherical wrist based on hydraulic drive technology,and then makes a series of researches based on this wrist.First of all,according to the design requirements,a new type of wrist structure scheme and drive scheme based on hydraulic drive are formulated,and the formulated structure scheme is theoretically analyzed and calculated,and the parameters of the components involved in the wrist are designed according to the calculation results.On this basis,the parameters of the hydraulic actuator are calculated and designed.In addition,in order to make the whole wrist device compact and meet the design requirements,it is necessary to consider the layout of the sensors,and then the conceptual design of the wrist will be completed.Secondly,according to the mechanical structure and driving scheme of the designed wrist,conduct theoretical analysis of the wrist,establish the forward/inverse kinematics model of the wrist and conduct simulation research and analysis.The kinematics simulation results show that the strategy of driving the wrist pitch/side swing joint by the oil cylinder and the strategy of driving the wrist rotation joint by hydraulic motor+ball-cage constant velocity joint are correct and feasible.The dynamic simulation results show that the designed wrist drive scheme is reasonable.At last,aiming at the problem of insufficient accuracy in the(35)K_p rule library when theK_p parameters were corrected online,which was currently widely used in traditional fuzzy PID control algorithms,analyzed the(35)K_p rule library and identified which rules were unreasonable,then adjusted and improved them,and completed the optimization of the(35)K_p rule library,and a new control strategy was designed—improved fuzzy PID.With the help of multi-domain collaborative simulation technology,hope to prove the superiority of the improved method and improve the control performance of the system.The results indicate that the new(35)K_p rule library is more flexible and accurate in online correction ofK_p parameters than the traditional(35)K_p rule library.Because it overcomes the problem of existing(35)K_p rule library,the servo tracking precision and anti-interference capability of the improved fuzzy PID controller are improved significantly.It provides a key part of the controller for the realizing high-precision position and attitude servo control of the wrist.Based on the electro-hydraulic co-simulation technology of Recurdyn-simulink-AMESim,a virtual platform of the wrist's electro-hydraulic co-simulation is established,and then the joint simulation and analysis of wrist's single-joint actions and wrist's multi-joint coordinated actions are carried out with the help of the simulation platform.The simulation results show that the improved fuzzy PID control still has excellent servo control ability and servo tracking accuracy in the wrist pose servo control,which can realize the wrist pose servo control with higher accuracy.