Research On Scale Parameter Optimization And Control Method Of High-speed Parallel Manipulators

This paper closely combines the needs of industrial robots in the fields of food,medicine,electronic packaging and sorting,studied on the scale optimization design and control method for a high-speed parallel manipulator(Cross-IV manipulator)with three translations and one rotation designed by Tianjin University,It mainly expands the research from three aspects: kinematics and rigid body dynamics modeling,scale parameter optimization and motion control method;based on kinematics and rigid body dynamics model,it studies scale parameter optimization and high-speed and high-precision grasping control method of C4 manipulator,and verifies the control strategy on the experimental prototype.The achievements of this paper are as follows:Firstly,in the aspect of kinematics and rigid body dynamics modeling,the kinematics model of C4 manipulator is built by vector method,and the complete rigid body dynamics model of C4 manipulator is built based on virtual work principle.A method of converting the mass of driven arm to the two ends of the active arm and the moving platform according to three distribution coefficients of gravity,inertia force and inertia moment is proposed,and the scale parameters of the manipulator are studied.Five influence factors,such as trajectory parameters,affect the accuracy of simplified method.Taking the absolute value of moment difference between four branched chains of complete and simplified model of manipulator as the objective function of optimization,the accuracy of rigid body dynamics modeling using combined distribution coefficient method is compared with that using other methods,it also provides theoretical basis for subsequent manipulator scale synthesis and dynamic feedforward control method.Secondly,based on the established kinematics and rigid body dynamics model of the C4 manipulator and the indirect Jacobian matrix determinant,the general intra-chain and inter-chain pressure angles of the C4 manipulator as well as the singularity of the mechanism are analyzed.It is found that the general inter-chain pressure angles of the C4 manipulator have limitations in describing the motion of the manipulator,without considering the adjacent branched chains and the rest.Based on the motion/force transfer characteristics of branched chains,considering the motion transfer of four adjacent branched chains,a complete set of pressure angle indices between chains of C4 manipulator is constructed,and the singular state of the manipulator is described in physical sense.Then the performance indices of scale optimization are constructed,and the objective function of optimization is constructed based on the proposed pressure angle indices and the global characteristics of Jacobian matrix condition number.Finally,kinematics multi-objective optimization is realized by combining scale constraint and pressure angle constraint,and dynamics optimization is realized based on two kinds of dynamic performance indicators.Sensitivity of kinematics and dynamics performance indicators and workspace position of manipulator under a set of parameters is analyzed,and dynamic performance indicators of kinematics optimization results are compared with dynamic optimization results,and finally mechanical optimization results are obtained.The optimal scale parameters of the manipulator are given,and reasonable suggestions are put forward for the actual operation of the manipulator.Finally,in the aspect of motion control of C4 manipulator at high speed,firstly,the servo control system of the manipulator is modeled,and the PID parameters are tuned based on genetic algorithm.On the basis of simplified rigid body dynamics model,the kinematics closed-loop control and the torque feed-forward control model are built with Simulink,and then the simulation is carried out based on dynamic response characteristics and joint angle accuracy;secondly,the pure software control is used.The TwinCAT system is developed to carry out dynamic control experiments to verify the dynamic characteristics of the manipulator after introducing a moment feed-forward channel at high speed.It is of great significance to improve the tracking accuracy of the manipulator joints and the positioning accuracy of the end.