Cooperative Anti-swing Control Of Underactuated Dual Rotary Crane Systems

Cranes,as a kind of large-scale industrial engineering machines,play an indelible role in the field of modern engineering,and have made great contributions to infrastructure construction of our country.Owing to the strong load capacity,cooperative dual rotary crane(DRC)systems are widely used in important construction occasions,such as roads,railways,urbanization,and so on.However,at present,the dynamic analysis and control problems of DRC systems have not received enough attention.Compared with single crane systems,DRC systems contain more state variables,geometric constraints,and complex coupling relationships;meanwhile,their nonlinear and underactuated characteristics further increase the control difficulty.Faced with the requirements of precise positioning and swing elimination,it is difficult to guarantee the efficiency and safety by only depending on manual operations.Therefore,it is very challenging to realize the control objectives of boom positioning,payload anti-swing,and other practical requirements by only utilizing the driving force applied to boom pitching motions.In order to solve the above problems and realize high-performance control,DRC systems are analyzed in depth in this thesis,and three effective control methods are further provided.The major contributions are summarized as follows.1)An output feedback control method with consideration for actuator constraints.By deeply analyzing system characteristics,an accurate dynamic model is established based on Lagrange’s method,without assuming that the payload swing angles are small enough.Furthermore,an output feedback control method is proposed to handle the issue of velocity signal unavailability.In this thesis,a virtual system is constructed to dynamically generate auxiliary signals,which can replace velocities as feedback signals.In addition,since actuators’ output signals always have upper bounds in practice;hence,a saturation function is introduced into the controller,and the control inputs can be limited within the given ranges by adjusting control gains conveniently.Furthermore,through the mathematical analysis based on Lyapunov techniques and La Salle’s invariance principle,the closed-loop system is asymptotically stable at the equilibrium point.Finally,several groups of experiments are completed on the self-built experimental platform,which prove the satisfactory control performance and robustness of the designed control method.2)An adaptive control method embedded with an integral term considering restraining boom motion overshoots.In order to handle the issue of steady-state errors caused by inaccurate compensations of frictions and gravity torque,an adaptive control method embedded with an integral term is proposed.Specifically,to balance the gravity torque in the vertical direction,an adaptive method is used to estimate system parameters(including payload mass,etc.).At the same time,an integral term is introduced into the controller,which improves the positioning accuracy and is beneficial to the practical requirements of accurate operations.Due to safety requirements and limitations of actual mechanical structure,the boom movement space is limited;therefore,the constraint terms are constructed to restrain overshoots of boom motions and limit movement ranges of two booms.Through the rigorous theoretical analysis,it is proven that the constraint terms can limit two booms within the given ranges.In this thesis,Lyapunov techniques and La Salle’s invariance principle are used to complete stability and convergence analysis.On the basis of theoretical analysis,three groups of experimental results are given,which further verify the effectiveness and robustness of the presented control method.3)An adaptive sliding mode tracking control method in the presence of parametric uncertainties.The control methods based on exact model knowledge are generally sensitive to unknown system parameters/structures,which are difficult to guarantee satisfactory control performance when encountering inevitable parameter uncertainties.Therefore,based on the original complex nonlinear dynamics,in this thesis,an adaptive sliding mode tracking control method is proposed to overcome the challenge of parameter uncertainties,which can effectively track the preset trajectories and restrain payload swing angles.Specifically,by constructing a virtual reference trajectory,the proposed trajectory tracking control method makes the motion process smoother,which is beneficial to suppress payload swing angles.Through the strict theoretical analysis based on Lyapunov techniques and Barbalat’s lemma,it is proven that the control method can not only eliminate the tracking errors of state variables within finite time,but also make payload swing angles asymptotically converge to the equilibrium point,which further ensures the work efficiency and safety together.Furthermore,the corresponding experimental results are given to validate the tracking results,anti-swing performance,and anti-disturbance ability of the proposed method.