With the development of artificial intelligence technology,industrial robots are widely used in complex parts contour processing,precision handling and other fields.The machining trajectory and motion trajectory of industrial robots are becoming more and more complex.However,the complex trajectory mostly uses straight line or arc to approach the target curve,and the tangential discontinuity between line segments connecting corner leads to the mutation of acceleration curves,which affects the motion stability of the robot.At the same time,there are modeling errors and external disturbances in the actual motion control process of the robot,which leads to the robot control system based on dynamic model is difficult to accurately track the planned trajectory,then the system exists the problems of low motion accuracy and unstable motion.Based on this,Delta parallel robot is selected as the study subject in this paper,and studies the smooth trajectory planning and precise tracking control method.The main research contents of the article are following:(1)Kutzbach Grubler formula is applied to calculate and analyze the degree of freedom of the Delta robot.The forward and inverse kinematics equations of the robot are solved and the dynamic model is established.(2)To tackle the problem of acceleration curve mutation caused by tangential discontinuity of complex trajectory line segments of their connecting corner,then causing impact and vibration of the system,the linear interpolation algorithm with parabolic transition is used for coarse interpolation in Cartesian space,and the coarse interpolation points are mapped to joint space through robot kinematics.Based on the mapping of coarse interpolation points into the joint space,a quintic uniform B-spline curve in the joint space is applied to the second trajectory planning,and high order continuous smooth trajectories are obtained,the acceleration value is reduced by 10.3%at most.(3)An improved adaptive backstepping fractional order non-singular terminal sliding mode control method is proposed to solve the problem of unstable motion of robot motion control system caused by modeling error and external disturbance.Firstly,the design process of the backstepping controller is combined with the design process of the fractional order sliding mode controller by introducing the fractional calculus operator,so that the energy transfer of the fractional order sliding surface is slow in the switching process and the chattering is suppressed.Simultaneously,in order to solve the the problem of uncertainties such as external disturbances,upper bound of the unmodeled error and disturbances of the robot motion system is estimated by using adaptive law,which can effectively improve the system motion stability.Finally,a co-simulation model based on ADAMS-MATLAB/Simulink is built to further verify the motion control system capability.Simulation results indicated that the improved trajectory planning algorithm reduces the chattering and shock phenomenon.The trajectory tracking control performance of each joint of the parallel robot is effectively improved,and its root mean square error is within2.0×10-4rad.The effectiveness of designed control algorithms are demonstrated.(4)By designing the hardware and software of the robot prototype,Delta parallel robot platform based on Ether CAT communication mode is built.Engineering tests of the improved smooth trajectory planning and precise tracking control method are applied to the robot experimental platform,and the algorithms performance is further verified. |