Synchronous Coordination Control Of A Novel Hybrid Mechanism For Automobile Electro-coating Conveying Based On Contour Error

In the modern automobile manufacturing industry,coating is the key technology,and the conveyor works throughout the whole process of the automobile coating production line.The performance of conveyor has a great impact on the white car body surface treatment.The advanced automobile electro-coating conveyers,such as Rodip and VarioShuttle,cannot bear heavy load because of the cantilever beam structures,which lead to the low flexibility of multi-vehicle mixed production.In order to make up the disadvantages of the above conveyors supported by National Natural Science Foundation of China(Grant No.51375210),a novel hybrid mechanism for automobile electro-coating conveying is developed.The novel conveying mechanism has multi active joints and symmetrical mechanical structure on both sides,and there are couplings among the active joints,so the synchronization coordination among the active joints will have an impact on the overall performance of the conveying mechanism.Therefore,the conventional kinematic control strategies and dynamic control strategies are directly from serial mechanism control strategies.When these control strategies are used directly on the conveying mechanism,the structural characteristics of multiple kinematic chains are neglected.Synchronization among the kinematic chains is not taken into consideration,thus it is necessary to improve the synchronous coordination among the active joints so that the conveying mechanism is stationary and reliable in variety of working environment.Thus an active joint synchronous coordination controller(AJ-SC)is presented to realize the coordination motion of conveying mechanism.However,the AJ-SC reduces the tracking error of the active joint,but the decrease of the tracking error does not necessarily lead to the decrease of the contour error,so that is difficult to guarantee the trajectory tracking precision of the end-effector.The contour error is the most important index of kinematic control precision and the other errors in the control system are ultimately reflected as contour errors in hybrid mechanism control system with multiple kinematic chains.Therefore,a method for estimating the contour error of the end-effector is proposed and a contour error synchronization coordination controller(CE-SC)is designed which can reduce the tracking error and synchronization error of each active joint and improve the accuracy of the trajectory tracking at the end of the conveying mechanism.The first part of this paper mainly summarizes the research status of contour error control.The second part is mainly based on the conveying mechanism prototype for kinematics and dynamics analysis,and the results of kinematics and dynamics analysis are simulated by MATLAB respectively.The simulation results show the correctness of kinematics and dynamicsanalysis.At the same time,in order to meet the requirements of prototype experiment and coating process,the desired trajectory of prototype is given.And the working space of the prototype is analyzed,and its working space is given.The third part is mainly to solve the problem of synchronous coordination between the kinematic chains and the contour error of the end-effector.Then,the active joint synchronization error defined by the deviation of the adjacent active joint tracking error is proposed and an active joint synchronous coordination(AJ-SC)controller based on the defined active joint synchronization error is designed according to the structural characteristics and the kinematic characteristics of the conveying mechanism.In order to further improve the tracking accuracy of the trajectory at the end of the mechanism,a synchronous coordination controller is designed according to contour error(CE-SC)which is based on the tracking of the trajectory of the mechanism.And a synchronous coordination controller based on contour error(CE-SC)is designed,and compared with the AJ-SC by MATLAB simulation.And the MATLAB simulation results show that the CE-SC has higher tracking accuracy compared with the AJ-SC by MATLAB simulation.Finally,an experimental platform is constructed for the conveying mechanism prototype and complete the prototype control experiment is completed based on the platform.The experimental results further validate the effectiveness of the CE-SC.