Integrated Design And Motion Control Of A 6-RSS High-speed Parallel Robot

In this thesis,based on the development requirements of domestic high-speed parallel robots in pharmaceutical,food,electronics and other industries,a high-speed parallel robot that can achieve six degrees of freedom in space is taken as the research object.In order to lay an important theoretical and technical foundation for the autonomous design and performance improvement of this kind of robot,detailed research is carried out on the ontology structure design,parameter integrated optimization design,trajectory planning and optimization,servo system identification and motion control based on adaptive fuzzy controller.The following creative achievements have been made:(1)Mechanism design and parameter integration optimization designAccording to the freedom formula of space mechanism,a kind of kinematic branch chain composed of"rotating motor+ball hinge+ball hinge+spring"is designed,and a 6-RSS(R-rotation pair,S-ball pair)high-speed parallel robot is designed by using the branch chain structure.The high speed parallel robot can achieve six degrees of freedom in space,and has the characteristics of complex structure,high stiffness and high precision.For the current optimization design problem of this type robot that only considers kinematics,an evaluation index system that can fully reflect the system kinematics,rigid body dynamics and coupling characteristics,and static stiffness global performance is established,and the integrated design method of dimensional parameters-section parameters-driving parameters is proposed.(2)Trajectory planning and motion smoothness optimization designAccording to the motion characteristics of 6-RSS high-speed parallel robot,the trajectory planning is carried out from joint space and operation space respectively.Through simulation comparison,when the robot terminal moving platform contains translation and rotation motion,the trajectory planning in operation space is more suitable for this type robot.To ensure the robot motion smoothness,a trajectory optimization method in operation space is proposed based on the high-order B-spline curves motion law,and an evaluation system is established to achieve the joint motion smoothness and minimize the deformation error of terminal trajectory.Firstly,the influence of mixed motion coefficients on the smoothness of robot motion is discussed,and a group of final mixed motion coefficients is established.Secondly,the smoothness index is established by the minimum average cumulative effect of joint jerk,and the method could improve the motion smoothness by reducing joint jerk.Thirdly,in order to solve the deformation problem of horizontal motion trajectory during smoothness optimization,the minimum deformation index is established according to the relationship between control vertex of B-spline curve and key points of trajectory.Finally,considering the above two aspects,the comprehensive evaluation index is established,and the designed method is verified by simulation and experiment.(3)Servo system identification and motion control researchIn order to improve the control accuracy of 6-RSS high speed parallel robot,the servo parameter identification and motion control method are studied respectively.Firstly,an adaptive recursive least squares(ARLS)algorithm based on ridge regression theory is proposed based on the established robot servo system identification model.Secondly,ridge regression theory and U-curve method are introduced into the identification process,regularization parameters and mean filtering are selected to improve the identification accuracy.According to the identification results of the servo system,the other control parameters of the three-ring servo motor are set up and the simulation model of robot position control is established.Thirdly,PID control and feedforward control are introduced to reduce the joint position following error.Finally,in order to further improve the dynamic response capability and control accuracy of the robot,a fuzzy controller is established based on non-uniform Gaussian membership function and Mamdani fuzzy reasoning algorithm,and an adaptive fuzzy PID+feedforward control method is proposed.Simulation results show that the proposed method can reduce the robot joint following error and improve the control accuracy of the robot end-effector.Based on the design theory and method proposed in this paper,an engineering prototype of 6-RSS high-speed parallel robot is successfully developed.Experimental results of the prototype show that the robot can achieve a range of motion of 600×115(mm),with high speed(120 ppm beat)and high acceleration(150 m/s~2),as well as a load capacity of 1kg.At the same time,the robot controller was combined with Simulink program to build a control test platform,and verified that the designed control method can reduce the joint position following error by 30.5%,and the terminal trajectory error can be reduced by 53.4%at most,so as to effectively improve the robot motion stability and control accuracy.The above research results enrich and develop the theoretical basis of high-speed parallel robot,expand the application range of this kind of robot,promote the application of related technologies in practical engineering,and have important theoretical significance and engineering application value.