Nonlinear Control For Single-Pendulum And Double-Pendulum Overhead Cranes

Overhead cranes have been widely applied in factories,construction sites,harbors,wharfs,etc.,for payload transportation.The main objective of overhead crane systems is fast,precise positioning,and to prompt payload-swing mitigating.Overhead crane systems,which have fewer number of independent control inputs(control forces imposed on the trolley)than the number of to-be-dominated degrees of freedom(trolley positions,payload-swing angles),are underactuated systems.Due to the omission of partial actuators,underactuated systems have some advantages such as low cost,simple structure,low power consumption,and so on.However,the system state variables are highly,nonlinearly coupled,which makes it challenging to design the crane controllers.Up to now,the overhead crane is normally operated by manual,which is inefficiency and insecurity.In this case,the antiswing positioning performance of overhead crane systems depends entirely upon operational experience of the workers.Therefore,it is of great practical significance and engineering value to design crane controllers.Although a series of control methods have been proposed for underactuated overhead crane systems,from the view of actual applications,the existing control methods have the following drawbacks:1)most of exisiting control methods neglect trajectory planning part.It should be pointed out that,the motion planning method for double-pendulum overhead crane systems is still blank till now;2)Currently trajectory tracking control methods cannot guarantee the bounds of the tracking error,and cannot be applied to the cases of unknown system parameters;3)To guarantee the convergence of the system states,existing control methods assume the initial payload-swing as 0;4)If the traveling distance changes,the existing trajectory planning methods need to offline recalculate the trajectory parameters.Therefore,a trajectory cannot be used for different traveling distances;5)Currently regulation control methods cannot ensure the smooth start of the trolley,and are not applied to 3-dimensional overhead crane systems,double-pendulum overhead crane systems,and overhead crane systems with payload hoisting/lowering;6)The case of external payload disturbances for overhead crane systems with payload hoisting/lowering is not fully considered.In this case,the payload will not be vertically stabilized,but be finally regulated with the cable forming an angle with the vertical direction;7)Existing control methods can merely provide at most asymptotic stability,which is insufficient for high precision transportation tasks;8)Most existing control methods require full state feedback.However,it is difficult to measure the payload-swing in many occasions.To solve the aforementioned problems and to improve the control performance of trolley positioning and payload sway suppressing,we carry on a further research for overhead crane systems.The main contributions of this thesis are given as follows.1)A novel online motion planning method for double-pendulum overhead cranes.The hook-swing and the payload-swing are closely related with the trolley acceleration motion.By analyzing the coupling behavior among the trolley displacement,the hook-swing,and the payload-swing,an online motion planning control method is proposed for double-pendulum overhead cranes.The planned trajectory can be implemented online without the need of advanced or offline planning.Some simulation results are presented to validate the control performance of the proposed control method.2)Trajectory tracking control methods for overhead cranes.To deal with the problems of the existing trajectory tracking control methods,two control methods are proposed.First,an adaptive tracking controller is developed for double-pendulum overhead cranes subject to parametric uncertainties and external disturbances.The proposed adaptive tracking control method guarantees that the trolley tracking error is always within a prior set of boundary conditions and converges to zero rapidly,achieving precise trolley positioning,quick hook and payload-swing eliminating.Moreover,it is robust with respect to system parametric uncertainties and external disturbances.Then,by converting the error tracking overhead crane dynamics to the objective system,we obtain the error tracking control law for arbitrary initial payload-swing angles.It does not require that the initial payload-swing angle remains zero,whereas this requirement is usually assumed in conventional methods.Owing to the same attenuation behavior,the desired error trajectory for the trolley for each traveling distance is not needed to be reset,which is easy to implement in practical applications.Simulations and experimental results are illustrated to validate the superior performance of the proposed error tracking control method.3)Regulation control methods for overhead cranes.To solve the limitations and drawbacks of the currently regulation methods,two nonlinear controllers are designed.The first method is free of cable length with a simple structure.Therefore,it is robust with respect to uncertain/different cable lengths.Besides,the coupling behavior between the trolley movement and the payload-swing is enhanced by fabricating two composite signals,and thus improves the transient performance.Simulations and experimental results are conducted to show the superior performance and strong robustness of the proposed control method.The second method is proposed for double-pendulum overhead crane systems.By incorporating a smooth hyperbolic tangent function into the control law,the proposed controller guarantees soft start of the trolley.The proposed control method is model free with a simple structure.By comparing it with other existing control methods,its superior control performance and strong robustness are verified.4)Control methods for overhead cranes with payload hoisting/lowering.In practice,vertical payload motion is always involved in overhead cranes.In this case,the cable length turns from a constant to a variable,which may induce large-amplitude load swing and make it more challenging to develop an appropriate controller.Without any linearization and approximation of the crane dynamics,a partially saturated adaptive learning controller and an energy-based fuzzy controller are designed.The first control strategy considers the effects of the unknown or uncertain system parameters.By introducing hyperbolic tangent functions into the control methods,the proposed controllers can guarantee soft trolley start even in the case of high initial velocities of trolley and cable.To decrease the convergence time in the case of the overhead crane parameters already experienced by the system,the learning component is added to the proposed partially saturated adaptive controller.The case of external payload disturbances is fully considered by the second control strategy.We build the model and suggest an energy-based fuzzy control method for underactuated overhead cranes with load transferring,lowering and persistent external disturbances.To estimate the persistent external disturbances,a fuzzy disturbance observer is constructed.Numerical simulation results are included to examine the effectiveness and robustness of the aforementioned two control methods.5)Sliding mode control methods with unmodeled dynamics and external disturbances.An enhanced coupling PD with sliding mode control method and a finite-time trajectory tracking control method without payload-swing feeback are proposed for double-pendulum overhead crane systems and 2-dimensional overhead crane systems,respectively.The first method has a simple structure like the PD method,and strong robustness with respect to uncertain model,different systems parameters,and various external disturbances of the SMC method.This method stabilizes the double-pendulum overhead crane system without requiring any knowledge of the system parameters.Moreover,the internal coupling nature is enhanced by introducing a composite signal.Unlike most existing crane control methods,the second controller needs no payload-swing feedback and is proposed in the framework of observer-based control design.To estimate unavailable payload-swing and uncertain dynamics,two terminal sliding mode observers are designed,respectively.The proposed controller guarantees finite-time tracking results even in the presence of uncertain dynamics and no payload-swing feedback.Simulation results demonstrate that the abovementioned two methods can achieve satisfactory control performance.