Dynamic Sliding Mode Control With Adaptive Extended State Observer Of Hybrid Mechanism For Automobile Coating Conveying

In recent years,the automobile manufacturing industry has been developed rapidly.However,some problems exist in automobile white body coating conveying equipment,such as low flexibility level and weak carrying capacity.To this end,we have developed a hybrid mechanism for automobile coating conveying(HMACC),which is mainly composed of two groups of parallel mechanisms connected symmetrically on both sides.In order to realize the high performance trajectory tracking dynamic control of HMACC,it is necessary to solve the uncertainty problems in HMACC,such as modeling error,friction and external disturbance.Sliding mode control(SMC)has the advantages of being insensitive to uncertainty.At present,the following difficulties exist in dynamic SMC of HMACC:(1)Due to the upper bound of the uncertainty information in practice system is not constant and unknown,the switching gains of SMC are overestimated to ensure the robustness of the system with uncertainties,which will cause large chattering;(2)The SMC has been combined with nonlinear disturbance observer,but it needs to meet the restriction condition that the first derivative of the observed uncertainties should approximately zero,and the inverse dynamics model needs to be implanted during observer design,which will bring difficulty in observer design.To this end,a sliding variable based adaptive switching gain sliding mode control(SVASMC)is designed at first.Secondly,by introducing an extended state observer and designing an adaptive law to adjust the bandwidth gain of the observer in real time,furthermore,a dynamic sliding mode control with adaptive extended state observer(DSMC-AESO)is proposed,which only needs the bounded first derivative of uncertainties and could avoid the overestimated observer bandwidth gains.The main tasks completed in this paper are as follows:(1)The kinematics and dynamics analysis of HMACC are completed.According to the position and structure characteristics of HMACC,the kinematics analysis is carried out,and the Jacobi matrix of HMACC is obtained by deriving the inverse kinematics solution.The dynamic analysis and modeling of HMACC is carried out by the Lagrange method.The correctness of the model is verified by MATLAB.(2)A SVASMC method for HMACC is proposed.Due to the upper bound of the uncertainty information in practice system is not constant and unknown,the switching gains of SMC are overestimated to ensure the robustness of the system with uncertainties,which will cause large chattering.A SVASMC method is designed,which can adaptively adjust the sliding mode control switching gain without the certain knowledge of the upper bound information of the uncertainty,so as to guarantee the robustness of HMACC and reduce the chattering.The stability of SVASMC is proved theoretically.Compared with the conventional reaching law sliding mode control,the MATLAB simulation experiment results show the effectiveness of the SVASMC method.(3)A DSMC-AESO method for HMACC is further proposed.The SMC has been combined with nonlinear disturbance observer,but it needs to meet the restriction condition that the first derivative of the observed uncertainties should approximately zero,and the inverse dynamics model needs to be implanted during observer design,which will bring difficulty in observer design.To this end,by introducing an extended state observer and designing an adaptive law to adjust the bandwidth gain of the observer in real time according to the system error,furthermore,a DSMC-AESO method is proposed which only needs the bounded first derivative of uncertainties and could avoid the overestimated observer bandwidth gains.It could estimate and compensate the system uncertainties in real time,and reduce the burden of SMC facing the system uncertainty,and further weaken the chattering,so as to improve the robustness of the control system of HMACC.The stability of DSMC-AESO control system is proved theoretically.Compared with the adaptive sliding mode control with extended state observer(ASMC-ESO)and SVASMC,the MATLAB simulation experiment results show the effectiveness of the DSMC-AESO method.(4)An experimental platform for DSMC-AESO control system of HMACC is constructed.The comparison experiments among DSMC-AESO,ASMC-ESO and SVASMC are completed on the prototype experimental platform,the prototype experimental results further show the superiority of the DSMC-AESO method.