| Parallel configuration positioning platform has many advantages,such as multiple degree of freedom,strong load capacity,high stiffness,small volume and no accumulative errors.Now it has been very popular in the field of robot.However,because the parallel platform is a nonlinear system,the forward kinematics solution has the problem of multiple solutions,and there are coupling force interference between each drive rod and internal disturbance of the motor,which will increase the motion error of each drive rod and reduce the positioning accuracy of the positioning platform.In order to meet the positioning accuracy requirements of the positioning platform,the research on the forward kinematics solution and nonlinear control provides a theoretical basis for the development of the positioning platform.Firstly,the parallel configuration of the positioning platform was analyzed,and the kinematics model of the positioning platform was established through the transformation of space coordinates,the inverse equation of kinematics was obtained,and the forward solution optimization model was proposed based on the uniqueness of the inverse solution of kinematics,which would turn the positive solution into an optimization problem.The conventional MFO algorithm was improved by the light intensity attraction characteristic and Levy Flight to change the position updating mechanism of moths,so as to improved the optimization performance of the algorithm.The improved algorithm and Newton iterative method were used to solve the forward kinematics solution of the positioning platform.The simulation results showed that the forward solution accuracy obtained by using the forward solution optimization model can meet the positioning accuracy requirements of the positioning platform in this paper.Secondly,the selection of key hardware and the design of software system framework were completed according to the design requirements of parallel platform.The overall control strategy of the positioning platform was introduced.Considering the complexity and stability of the control system of the positioning platform,the high precision control of the positioning platform was realized by using the decentralized control method and improving the control precision of each electric cylinder.On this basis,the mathematical modeling of each driving electric cylinder was carried out,the mathematical model of the motor driven servo system was given,and the design of current loop and speed loop was completed.Thirdly,considering the control mode of decentralized control and the strong coupling characteristics of the positioning platform itself,it may be disturbed by uncertainty in the process of movement.The sliding mode variable structure control with insignificant interference was used to design the single electric cylinder motion controller.For positioning platform in the process of movement by the interference of the uncertainty of the sliding mode control was SMFO algorithm to optimize the reaching law parameters,to improve the robustness and anti-interference ability of the controller,the adaptive sliding mode controller was put forward,and the simulation results showed that:in this paper,the designed controller could improve the control precision of the electric cylinder when affected by external interference.Finally,the self-adjusting sliding mode controller and the positioning platform were used for motion simulation experiments.The simulation results showed that the control error of the parallel platform's electric cylinder was less than 10-3mm,which can meet the design requirements of the controller.In conclusion,the forward solution optimization model and the self-adjusting sliding mode controller designed in this paper could meet the design accuracy requirements of the positioning platform. |
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