Research On Anti-Swing Control For Crane Systems With Complicated Swing Effects

Cranes play important roles in transportation;with the gradual development of the manufacturing industry modernization,crane operation modes are changing to intelligence and automation.During payload transportation,it is quite important to present advanced positioning control approaches,especially anti-swing control strategies,since payload swing directly affects safety and efficiency.As for safety,if payloads oscillate severely due to inertia,then there would be higher risk of accidents,such as collisions.As for efficiency,operators often adjust their operations according to payload swing;in other words,the operators will continue to complete transportation tasks only after payloads have been anti-swayed naturally and safety risks have been eliminated,which will badly degrade efficiency.Hence,in the field of crane control,it is of great practical significance to carry out research on anti-swing control strategies.For decades,scholars all over the world have carried out in-depth research on anti-swing control strategies for various kinds of cranes,and obtained many achievements.However,there are still some difficult unresolved problems left.On one hand,payload swing makes crane systems possess underactuated characteristics,which increases the difficulties of analysis and control.On the other hand,cranes are also affected by many practical factors,such as specific hardware structures,environment,etc.,and hence,in many situations,there exist complicated swing effects,making the control issues more challenging.To be specific,some situations that may involve complicated swing effects include:(1)When considering rope length variation,payload swing becomes more complicated due to simultaneous transportation and lifting.(2)When transporting steel coils,profiles,containers,and other large-scaled goods,the relative swing between the hook and payload cannot be ignored;that is,there exist double-pendulum effects.(3)When the environment is complicated and changeable,e.g.,out of doors,at the harbour,on board,etc.,persistent external disturbances can easily affect payload swing.(4)When considering 3D(three dimensional)working space,stimulated by bridge movement and jib rotation,payloads will also swing in 3D working space.In view of the above situations involving complicated swing effects,many unresolved practical problems still exist as follows:(1)For existing planning methods,it is still difficult to optimize specific performance indices,such as efficiency and energy consumption.(2)Most existing feedback regulation control methods require exact model information.It is still difficult to suppress complicated swing effects in the presence of unknown uncertainties.(3)There are many practical problems,such as actuator saturation,unavailable velocities,differentiating noises,etc.In order to solve the above problems,this thesis puts forward a series of antiswing control methods for various kinds of cranes,in the presence of complicated swing effects.The main contributions are summarized as follows:(1)Overhead crane trajectory planning in the presence of payload hoisting or double-pendulum effects.Two optimal planning methods are proposed by using coupling relationships between actuated and unactuated state variables.First,the thesis improves the efficiency by simultaneously planning time-optimal trajectories for horizontal transportation and vertical lifting.The proposed trajectories can suppress payload swing by satisfying preset conditions.Then,the thesis generates an energy-optimal anti-swing trajectory for trolley motion in the presence of double-pendulum effects.The proposed trajectory can suppress double-pendulum swing,and can also reduce energy consumption.Simulation and experimental results are given to verify the effectiveness of the proposed method.(2)Ship-mounted crane control in the presence of double-pendulum effects and persistent sea wave-induced disturbances.In this thesis,the nonlinear doublependulum ship-mounted crane system dynamics is obtained,based on which,two anti-swing control methods are proposed.The first one accelerates the swing suppression process by using angular feedback.Also,rope length variation is constrained within the given range,so as to ensure safety.Then,this thesis proposes an amplitude-saturated output feedback method,by considering actuator saturation and unknown gravity compensation.This method does not involve any velocity signals,and generates amplitude-saturated control inputs,which avoids actuators from falling into saturation.(3)Overhead crane control in the presence of double-pendulum effects and unknown uncertainties.This thesis proposes an active disturbance rejection controller.The uncertainties are described by a lumped disturbance term,and a state observer is constructed.Then,on the basis of the state variable estimation,an adaptive law is designed to online estimate the unknown disturbance term.The proposed method can achieve effective trajectory tracking.Also,it is rigorously proven that the tracking error is bounded and can be reduced through gain tuning.Corresponding verification results are given.(4)Tower crane control under 3D working space.This thesis presents two control methods for tower cranes.The first method is designed for fixed-ropelength tower crane systems.An integral term is elaborately constructed,which can effectively eliminate the steady state error and improve positioning accuracy,although the friction compensation is inaccurate.In addition,an auxiliary term is designed to constrain the trolley displacement,so as to prevent accidents.Next,an adaptive output feedback control method is proposed for varying-rope-length tower crane systems.A new adaptive law is designed to identify unknown gravity online.Also,a virtual spring-mass system is introduced to generate virtual velocity signals,which are involved in the proposed controller instead of using real velocities.Hence,the proposed method is suitable for the situations with unmeasurable velocities,and can also avoid inducing differential noises.A series of hardware experiments are carried out.