Research On Synchronization Control Strategy Of Multi-DOF Industrial Robot

Due to the rapid development of manufacturing industry,the requirement of the controlling accuracy of industrial robots becomes increasingly strict.The highly accurate motion of the industrial robots with multiple degrees of freedom not only requires the precise movement position of each joint,but also requires the synchronism of the movement of all joints.The control unit of each joint in traditional industrial robots is relatively independent,and it does not receive the information from other joints.Consequently,the error generated by a joint can only be corrected by the control unit of the joint itself.However,it is clear that the overall performance of the multi-joint system is related to all joints.Thereby,in addition to applying the effective method to guarantee the position control of a single joint,the thesis also introduces synchronous control in the industrial robots with multiple degrees of freedom.The combination of the two control methods is able to achieve the precise control of the system by realizing the synchronous operation of all joints and improving the system performance regarding the synchronous control.Thus,the research regarding the synchronous control is of great significance to the industrial robots with multiple degrees of freedom.The research object in this thesis is industrial robots with multiple degrees of freedom.The thesis firstly analyzes and studies the position control of a single-joint system and the development of the synchronous control of multi-joint systems.By reviewing diverse domestic and foreign literature,the project determines the research methodologies.Then,the research conducts kinetic analysis on industrial robots.The thesis employs Lagrangian mechanics to establish mechanical models for the robots,based on which it demonstrates their fundamental characteristics.Next,considering that the precision of single-joint position control of an industrial robot system is still unsatisfactory,the thesis optimizes the position control schemes of the joints in industrial robots.By combining the fractional calculus with the sliding mode control strategies,the thesis proposes the fractional sliding mode control scheme.In the course of controller design,the research considers both fractional reaching law and fractional sliding mode control theories to identify the application features of the fractional calculus in sliding mode control.Therefore,the thesis successfully achieves the precise position control of a single joint,and it is verified by simulation software.The experimental results indicate that the introduction of fractional order reaching law can smooth the movement trajectory and diminish the chattering of the system.The fractional sliding mode control law can effectively improve the control accuracy.Therefore,the fractional sliding mode controller,which combines the advantages of both,greatly improves the performance of single-joint position control.Finally,based on the achievements in the control scheme of a single joint,the thesis introduces the cross-coupling synchronous control and determines the position error,synchronism error and coupling error,and the synchronization controller is designed.The results of the comparison verify that the aforementioned control strategy is able to enhance the tracking speed and precision of the joints,and the controller using the strategy reflects great effectiveness.Furthermore,the simulation results show that,compared with the traditional methods,the proposed method can effectively reduce the adjustment time of joint angular displacement.Also,the root mean square error(RMSE)of joint synchronization error and position error decrease considerably.Thus,it is clear that synchronization performance of industrial robot control system with multiple degrees of freedom is enhanced significantly.