Dynamic Sliding Mode Control Of The Hybrid Conveying Mechanism For Automobile Electro-coating Based On Novel Reaching Law

To remedy the defects of the existing automobile electro-coating conveying systems with cantilever beam structure,our research group developed a hybrid conveying mechanism for automobile electro-coating conveying.The conveying mechanism is taken as the research object and this paper focuses on its high performance control.The hybrid mechanism is a complex system with nonlinearity,strong coupling and multivariable.Compared with kinematic control,the dynamic control considers dynamics and coupling of mechanisms.Therefore,dynamic control can theoretically obtain better control performance.Conventional dynamic control methods,such as PD control and calculation torque control,highly depend on the accurate dynamic model of the mechanism.However,since the structure of the hybrid mechanism is complex,it is difficult to establish the accurate dynamic model of the mechanism in the actual modeling process.Therefore,the control performance of the conventional dynamic control methods is not satisfied.Due to sliding mode control has advantages of fast response speed,easy to be realized,and is insensitive to system parameter variations and external disturbances,it is expected further to improve the control performance of the conveying mechanism.Sliding mode control is a discontinuous control algorithm.However,due to the switching in the control algorithm,sliding mode control has the serious chattering problem,which decreases the control performance of the mechanism.To solve the chattering problem of sliding mode control,a novel reaching law is proposed in this paper,which can change the reaching speed in real time according to the system state distance from the equilibrium point.When the system state point is far away from the sliding mode,the reaching speed is increased.When the system state point is close to the sliding mode,the reaching speed can be reduced.On basis of the reaching law above,dynamic sliding mode controller is designed to improve the controller performance of the conveying mechanism.The controller effectively weakens the chattering of the sliding mode control,and at the same time ensures the adjusting speed,tracking accuracy and robustness,and the high performance control of the conveying mechanism can be achieved.First of all,this paper introduces the development of existing automotive electrophoretic coating equipment.Besides,the development process,application background,modeling methods and control methods of hybrid mechanisms are summarized.Then,the methods of solving the chattering problem of sliding mode control are introduced in detail.Secondly,by kinematic analysis of the conveying mechanism,the forward and inverse kinematic equations ofthe mechanism are obtained.Then,the Jacobian matrix of the mechanism is calculated and the kinematic equations are verified by MATLAB simulation.Thirdly,the dynamic model of the conveying mechanism is established by Lagrange method,and the correctness of the dynamic model verified by MATLAB simulation.Fourthly,in order to suppress the chattering of sliding mode control and improve the regulation speed,tracking accuracy and robustness of the system,a novel reaching law based dynamic sliding mode controller based on the dynamic model of the conveying mechanism is designed.The stability of the proposed control algorithm is proved theoretically.The proposed novel reaching law based dynamic sliding mode control is compared with the exponential reaching law sliding mode control by MTALAB simulation.The results show that the proposed novel reaching law based dynamic sliding mode control can reduce the chattering of the control system,and further improve the adjusting speed,tracking accuracy and robustness of the system.Therefore,it can help realize the high performance control of the conveying mechanism.Finally,the experimental platform of the novel reaching law based dynamic sliding mode control system is constructed by designing its soft and hardware platform.Based on the experimental platform,the motion control experiment of the conveying mechanism is completed.The experimental results further verify the feasibility and effectiveness of the proposed novel reaching law based dynamic sliding mode control algorithm.