Fuzzy Adaptive Estimation Uncertainty Sliding Mode Control Of Parallel Sandblasting And Derusting Mechanism Considering Friction Mutation

With the rapid development of bridge construction technology,the requirements of bridge steel box girder derusting process for derusting equipment are more and more high.In view of the existing gantry series derusting equipment structure is large and difficult to transport,as well as the wall-climbing derusting equipment bearing capacity is poor and can not deal with the complex surface.Aiming at the problems of large structure of existing gantry type series derusting equipment,difficult transportation,poor bearing capacity of wall climbing derusting equipment and unable to deal with complex surface,a parallel robot for sandblasting and derusting of steel box girder based on 6-DOF parallel structure is independently developed by our research group,which is composed of parallel operating mechanism,lifting mechanism and mobile platform,It has the advantages of high stiffness,strong bearing capacity and good mobility.Among them,the6-DOF parallel manipulator is a kind of complex nonlinear system with multi input and multi output.In order to realize the high performance motion control of the 6-DOF parallel manipulator,this paper focuses on solving the problem of uncertainty and friction mutation.(1)Modeling error,external disturbance,friction and other uncertainties exist in the 6-DOF parallel manipulators.These uncertainties directly affect the control effect of the 6-DOF parallel manipulators.Therefore,an adaptive uncertainty estimation sliding mode control(AEUSMC)method is firstly designed in this paper;(2)The end-effector of the 6-DOF parallel manipulator is driven by six electric cylinders to complete the movement.During the movement of the end-effector,the six electric cylinders frequently reciprocate.When the speed of the electric cylinder passes zero,the friction force changes suddenly,which causes the trajectory distortion of the electric cylinder and affects the control performance of the system.Due to the adaptive gain of the proposed AEUSMC method is constant,it is difficult to solve the problem of friction mutation when the speed of the electric cylinder passes zero.Therefore,this paper further designs a fuzzy adaptive estimation uncertainty sliding mode control(FAEUSMC)method considering friction mutation,which can dynamically adjust the adaptive gain when the friction mutation occurs.The main work of this paper are as follows:(1)The kinematics and dynamics of a 6-DOF parallel manipulator for sandblasting and derusting were analyzed.The inverse kinematics model is established,and the Jacobian matrix is derived,and the kinematics simulation analysis is carried out;Lagrange method is used to establish the standard dynamic model of 6-DOF parallel manipulator in joint space and the dynamic model with uncertainty.The correctness of the modeling is verified by MATLAB simulation.(2)An AEUSMC method is proposed.Aiming at the uncertainty problem of 6-DOF parallel manipulators,the robustness of sliding mode control is used to improve the control performance.However,in the design of sliding mode control for switching by symbolic function,the uncertain upper bound of the system is needed to select the switching gain.However,in practical engineering,because the upper bound is unknown,the switching gain is often overestimated,leading to large chattering in sliding mode control.In order to solve the above problems,an AEUSMC method was designed to estimate the uncertainty of the 6-DOF parallel manipulator.On the basis of improving the robustness of the control system,the switching term of sliding mode control is improved to an adaptive term based on sliding mode variable to suppress chattering;The theoretical analysis of stability is completed and the MATLAB simulation experiment is carried out.The results show the effectiveness of the proposed AEUSMC method.(3)Furthermore,a FAEUSMC method considering friction mutation is proposed.In view of the fact that the adaptive gain of the above methods is constant,it is difficult to solve the problem of friction mutation when the speed of the electric cylinder passes zero.Based on the AEUSMC method,a fuzzy rule is introduced to dynamically adjust the adaptive constant gain,and then a FAEUSMC method considering friction mutation is designed,To improve the adaptive ability of the control system to the friction mutation,so as to effectively reduce the trajectory distortion of the electric cylinder,and further improve the control performance;Matlab simulation experiments are completed,and the results show the effectiveness of the proposed FAEUSMC method considering friction mutation.(4)Based on the distributed computer control system of " Advantech 610 L IPC + Omron CK3 M motion controller",the experimental platform of FAEUSMC considering friction mutation system is constructed for parallel operation mechanism of sandblasting and derusting,and the hardware design and software development are completed.On this basis,the motion control experiment is completed.The experimental results further verify the effectiveness of the proposed FAEUSMC method considering friction mutation.