| As far as the crane system is concerned,its main control purpose is to transport the cargo swing as small as possible to the target position,that is,to realize the positioning of the trolley and the anti-swing control of the load.Owing to the advantages of strong load capacity,convenient operation and energy saving,underactuated bridge crane has been widely used in various fields of national economic production.However,the under-actuated characteristics of such systems make their internal dynamics more complex and often accompanied by non-holonomic constraints,so the study of control problems of such systems is meaningful and challenging.At present,most of the under-actuated bridge crane positioning and anti-swing control algorithms can only ensure that the system is gradually stable or uniformly ultimately bounded stable.With the improvement of production efficiency requirements,it is necessary to study a more efficient anti-swing control strategy for under-actuated bridge crane positioning.In order to improve the efficiency of crane transportation,the control strategies of limited time and fixed time tracking for underactuated bridge crane are put forward respectively,and the control objectives of fast positioning and load anti-swing are realized.The main work of this thesis includes:(1)、 aiming at the problem of limited-time positioning and anti-swing control of underactuated bridge crane,a finite-time tracking control strategy is proposed to ensure that the swing amplitude of the load is reduced as much as possible and the transportation efficiency of the crane is effectively improved.Firstly,the dynamic model of under-actuated crane is equivalent to cascade form,which reduces the difficulty of controller design.Secondly,based on the cascade system after conversion,virtual control law and real control input are constructed by combining back-stepping method and fractional-order dynamic surface control method,and then the final control input moment is designed.Finally,the finite-time stability theory is applied to the control of the under-actuated crane.The stability of the system is proved theoretically,and the convergence time of the system and the convergence set of tracking error are given.(2)、 aiming at the fixed-time positioning and anti-swing control of underactuated bridge crane,a fixed-time tracking control strategy is proposed to ensure that the crane can track the desired trajectory and reach the target position in a fixed time.Compared with the finite-time stability,the fixed-time stability makes the response time of the system independent of its initial state,so it is more reliable in practical application.Based on the converted cascade system,combined with backstepping method and dynamic surface technology with non-linear filter,the virtual control law and real control input are designed.Finally,the control input moment of the dynamic system is constructed,so that the system can be guaranteed to be stable in fixed time.Finally,the stability of the system is theoretically proved by the fixed-time stability theory,and the convergence time of the system and the convergence set of tracking error are given.Finally,by comparing the proposed control strategy with the existing control strategy,the simulation results verify the effectiveness and superiority of the proposed control algorithm.This thesis summarizes the content of this study and looks forward to the next step. |
