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Research On Robust Sliding Mode Control Of Uncertain Hybrid Mechanism

Posted on:2021-04-19Degree:DoctorType:Dissertation
Country:ChinaCandidate:W YuanFull Text:PDF
GTID:1368330623479254Subject:Control theory and control engineering
Abstract/Summary:PDF Full Text Request
The technical level of industrial robots and high-end manufacturing equipment is an important indicator of a country’s equipment manufacturing level.Driven by Industry 4.0 and Made in China 2025,China’s demand for industrial robots and high-end manufacturing equipment is increasingly urgent,and at the same time,it has put forward higher requirements for its functions and control performance.The hybrid mechanism combines the advantages of serial mechanism and parallel mechanism,and has become an important direction for the development of equipment innovation.At present,there are still some difficulties in the high performance control of the hybrid mechanism.The hybrid mechanism is a nonlinear system of MIMO and strong coupling.There are some uncertainties such as modeling errors,load variations,friction,unmodeled dynamics and external disturbances,the upper bound of which is unknown.Moreover,there are mismatched disturbances which are not in the same channel as the control voltage of the drive motor.Therefore,this dissertation takes the hybrid mechanism as the research object,and research robust sliding mode control method to seek for high performance control strategy,which lays the theoretical foundation for the engineering application of the mechanism in the electrophoretic coating conveyor equipment.The main work completed by the dissertation is as follows:(1)A robust sliding mode control method combined with a nonlinear disturbance observer is proposed.In view of the uncertainty in the hybrid mechanism,a sliding mode controller is designed to ensure the tracking performance of the system.For the chattering problem of the sliding mode control caused by excessive switching gain,a nonlinear disturbance observer with no limits of slowly changing uncertainties is designed to estimate the uncertainty in the system and actively compensate,so that the sliding mode controller only needs to select a smaller switching gain,which improves the robustness of the system and weakens the chattering problem.The simulation results show that the proposed method is superior to the sliding mode control method without nonlinear disturbance observer in trajectory tracking accuracy and control input smoothness.(2)An adaptive global robust sliding mode control method is proposed with no upper bounds of uncertainties.The above-mentioned robust sliding mode control method combined with nonlinear disturbance observer does not take the dynamic performance of the reaching phase into consideration.Thus,a finite time integral sliding mode controller is designed to eliminate the reaching phase of the sliding mode control,which realizes the robustness in the whole process of response for the hybrid mechanism.For the practical application,the accurate upper bounds of uncertainties of the hybrid mechanism cannot be obtained,so the adaptive rules are designed to dynamically adjust the sliding mode switching gain to avoid a prior requirement for the upper bounds of uncertainties,which further weakens the chattering problem of sliding mode control.In terms of over adaptation of the sliding mode switching gain,a nonlinear disturbance observer is introduced to compensate the uncertainties of the hybrid mechanism,which improves the robustness and tracking performance of the system.The simulation results show that the proposed method has good tracking performance compared with the robust sliding mode control method combined with the nonlinear disturbance observer.(3)An anti-mismatched disturbances robust sliding mode control method is proposed.The above control method solves the problem of matched disturbances of uncertain hybrid mechanism,however,it does not take the dynamic characteristics of the drive motor into consideration.If It is considered,the order of the hybrid mechanism system will be increased,and the uncertainties of the system will not meet the matching conditions.For the mismatched disturbances existing in the hybrid mechanism,a composite control strategy combining Backstepping control,sliding mode control,disturbance observer,and adaptive control is adopted to design the inverse sliding mode controller,and a disturbance observer is introduced to the design of the virtual control law to estimate and compensate the unmatched disturbances in the system.Based on this,an adaptive law is designed to dynamically adjust the switching gain to further improve the robustness of the uncertain hybrid mechanism system.Based on the Lyapunov stability theorem,the stability of the system and the progressive convergence of the tracking error of the hybrid mechanism are proved theoretically.The simulation results show that the proposed method still has good tracking performance when there is mismatched disturbance in the hybrid mechanism.(4)Based on the prototype system of the hybrid mechanism for automobile electro-coating conveying,an experimental study is conducted on the control method proposed in this dissertation.Compared with the robust sliding mode control method combined with nonlinear disturbance observer and the adaptive global robust sliding mode control method,the proposed anti-mismatched disturbance robust sliding mode control method has better overall performanceThe research in this dissertation has laid the foundation for the study on the control theory of the hybrid mechanism and the practical application of hybrid mechanism in the automobile electro-coating conveying equipment.
Keywords/Search Tags:hybrid mechanism, uncertainty, mismatched disturbance, nonlinear disturbance observer, robust sliding mode control
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