Anti-sway Control Research Articles

Positioning anti-sway control method for tower crane based on improved MFAC

A model-free adaptive control (MFAC) based on partial format is proposed for the complex modeling and uncertain model parameters of the tower crane (TC) in this paper. Firstly, considering the complexity of the TC nonlinear system, the data model of the TC is obtained through the partial format dynamic linearization method. Then, a model-free adaptive controller is designed for the TC, incorporating the change rate of the tracking error and its derivative into the objective function to address the inefficiency of traditional model-free controllers in controlling TCs. The convergence and stability of the proposed controller are also proved. To further improve the dynamic performance of the system, a tracking differentiator (TD) is introduced after the input signal. Finally, MATLAB simulation and experiments are conducted to verify that the proposed method can achieve precise trolley positioning while suppressing the load swing angle.

Modeling and anti-sway control method for vertical lift-up/lay-down process of slender-beam payload

The existing crane control methods mainly aim at suppressing the oscillation of the payloads during the transportation process. However, during the vertical lift-up/lay-down process of the slender-beam payload (SBP), such as the installation of the wind turbine towers, rocket assembly, and pipeline laying, one end of the SBP is lifted up and the other end is in contact with the ground. In this situation, the external disturbance may cause the SBP to sway around the contact point. In this paper, a nonlinear three-dimensional dynamic model for the vertical lift-up/lay-down process of the SBP is established. On this basis, a control method for suppressing oscillation during the lift-up/lay-down process of the SBP is proposed by adopting the non-singular terminal sliding mode control (NTSMC). The stability of the NTSMC is proved based on the Lyapunov method. Simulations and experiments are carried out to verify the effectiveness of the proposed method.

Anti-Swaying Control Strategy of Ship-Mounted 3-RCU Parallel Platform Based on Dynamic Gravity Compensation

It is essential to ensure stability during marine transportation or the installation of high center of gravity loads. The heavy loads increase gravity disturbance, affecting the steady-state-error control of the multiple degrees of freedom (DOFs) motion compensation platform. In this paper, we propose a proportional derivative (PD) controller with dynamic gravity compensation (PDGC) for a 3-RCU (revolute–cylindrical–universal) parallel platform to improve the control effect of marine motion compensation for high center of gravity loads. We introduce an evaluation parameter of load stability and a weighting coefficient of anti-swaying control to tune the controller performance. The controller can set its control target between the two, keeping the load contact surface level and allowing the load center of gravity with the least movement. By deriving the Jacobian matrix, the gravity disturbance in the joint space is calculated and is compensated in the controller. First, we verify the control superiority of this controller over the PD controller under sinusoidal excitation in simulation and validate the effectiveness of the proposed anti-swing strategy. Then, the experiments are conducted with random excitation. The root mean square (RMS) value of the load’s residual angle with the proposed controller is reduced to 32.2% and 17.6% in two directions, respectively, compared with the PD controller under class 4 sea state excitation. The proposed method is effective for the anti-swaying control of ship-mounted 3-RCU parallel platforms.

The examination of operator performance when controlling a shipboard crane anti-sway control system within a virtual-reality simulator

Anti-sway control systems are valuable tools for cranes to prevent unexpected payload sway and undesired motion. However, for shipboard cranes, where the operator moves with the ship, anti-sway control systems can result in significant relative motion between the payload and operator, particularly in rough seas while attempting to align the payload with an ocean-frame target. Therefore, an important question to ask is, do operators actually find anti-sway systems intuitive, or do they feel they have to “fight” the system to achieve their desired performance? To address the question, this paper presents a human factors study designed to evaluate the effectiveness of a shipboard crane anti-sway system with an operator-in-the-loop. Participants completed a series of tests in a virtual-reality simulator, in which they attempted to align the payload of a nine degree-of-freedom shipboard knuckle boom crane with targets in both the ocean/world coordinate frame and ship deck coordinate frame, using an anti-sway system that provided complete motion compensation in both coordinate frames. The study found that there was a statistically significant improvement in the participant’s ability to track a desired payload target with the use of the anti-sway system of up to 49.1%. In addition, as the participant had no knowledge of how the anti-sway system operated, or even if it was active, the results indicate anti-sway control systems can be intuitive for operators to use.

Double-step Acceleration Input Shaping Anti-sway Control Based on Phase Plane Trajectory Planning

Double-step Acceleration Input Shaping Anti-sway Control Based on Phase Plane Trajectory Planning

Dynamic analysis and robust control of ship-mounted crane with multi-cable anti-swing system

In this study, a novel fuzzy sliding mode anti-sway controller (FSMASC) is proposed by combining the in-plane angle and the out-plane angle with the fuzzy sliding mode technology, with the aim of addressing the existing problems facing simple control algorithms, low control accuracy of ship-mounted crane by the mechanical anti-sway method. Moreover, an improved reaching law adaptive sliding mode cooperative controller (ASMCC-IRL) is developed by integrating the cooperative motion between the anti-sway cables with the adaptive sliding mode technology, with the aim of addressing the ineffective cooperative motion between the anti-sway cable in the multi-cable system. First, a model of the ship-mounted crane and a dynamic model of the multi-cable system are built by employing the design prototype of the 45-ton ship-mounted crane on the 27,000-ton multi-purpose ship of COSCO Shipping Group. Subsequently, the FSMASC is proposed to suppress the swing of the load, and the ASMCC-IRL is developed to control the cooperative motion between anti-sway cables. Lastly, the control effectiveness of the FSMASC and the ASMCC-IRL is verified through simulation experiments. As indicated by the simulation results, compared with the scenario without the anti-sway control, the in-plane angle and out-plane angle of the FSMASC decrease by over 75%. Compared with the augmented PD controller (APDC), the error control performance of the ASMCC-IRL is enhanced by over 77.5%, and the convergence speed increases by over 50%.

Barrier function-based adaptive antisway control for underactuated overhead cranes

Barrier function-based adaptive antisway control for underactuated overhead cranes

Research on Swing Model and Fuzzy Anti Swing Control Technology of Bridge Crane

A bridge crane is often used in a complex environment and is often subject to the interference of all loads. Some uncertain factors often have an inevitable impact on its swing. So the force situation of the bridge crane during a working cycle is analyzed, and a three-dimensional dynamic mathematical model of the bridge crane is built. Through the simulation analysis of the model under the action of a driving force and wind load, the change law of the swing angle of the bridge crane is studied. Then, the fuzzy control theory is used to determine the control parameter in the anti-sway control process. The position, swing angle deviation, and deviation rate of the bridge crane are taken as the input, and the parameter correction is obtained after the fuzzification by using the center of gravity method. The anti-sway fuzzy control system of the bridge crane is designed and simulated. The research results show that the swing model of the crane is reasonable and the fuzzy PID anti-sway controller can not only improve the adaptability of the control system, but also overcome the large overshoot, quickly restrain the swing, and effectively realize the anti-sway function of the bridge crane.

Anti-sway control of variable rope length container crane based on phase plane trajectory planning

An overhead crane system is a complex time-varying system if it includes simultaneous hoisting and moving operations. To address the problem that time-varying systems usually have no exact analytical solution, an anti-swing method based on linear approximation of the phase plane trajectory is proposed. Specifically, the phase plane trajectory of the swing angle is first analyzed and it is found that the double-step acceleration method with unequal acceleration amplitude and acceleration time has a combination of limit loops in the phase plane trajectory of the swing angle when the rope length varies, so the average rope length of each section is used to approximate the natural oscillation frequency. Next, the input shaping technique is used to shape the input signal into the desired output signal so that the load swing angle can follow the planned trajectory. The desired acceleration amplitude and switching time are then derived based on the geometric relationship between the swing angle in the phase plane and the specific physical constraints. Finally, the feasibility of the proposed method is verified by numerical simulations.

Flatness-Based Backstepping Antisway Control of Underactuated Crane Systems under Wind Disturbance

A control method that combines trajectory planning and backstepping is proposed for the antisway problem of underactuated overhead cranes under wind disturbance. First, a set of flat outputs is proposed so that the crane system dynamics can be represented by each order of flat outputs. Sufficient relevant constraints are given to ensure that the trolley can arrive at the desired position in a limited time under variable rope lengths, and that the swing angle can be suppressed when the payload is lifted or lowered during operation. The planned trajectory is obtained by solving for the optimal parameters of the flat output. Next, to reduce the deviation caused by wind disturbance on the actual control of the trajectory, a tracking controller is designed. Because the system output space and flat output space are differentiable homeomorphisms, the backstepping controller constructed based on the flat output can indirectly control the system output, which makes the backstepping method applicable to underactuated cranes. The simulation results show that the proposed method is effective and has strong robustness.

Pay load Stabilization for Offshore Cranes: A Unified Controller Based on Flatness

Crane-based handling operations represent a vital part of today's maritime sector. To guarantee both safe and efficient payload handling with ship cranes, payload oscillations induced by the sea swell have to be damped. Approaches for payload stabilization usually consider either vertical position control (Active Heave Compensation, AHC) or sway reduction (Anti Sway Control, ASC). In this paper, a unified control scheme for spatial payload stabilization is proposed, utilizing the differential flatness of the crane system. The presented framework inverts the nonlinear payload dynamics by means of the flat mapping, thus facilitating controller design. Furthermore, the approach provides a systematic way to include the sea disturbance in the controller. Redundancy of the considered knuckle boom crane is exploited to track secondary control objectives. A related cost function weighting the crane's manipulability is derived and used in an optimization-based target selector. The controller design is evaluated in simulation for varying sea disturbances. The results suggest good AHC and ASC capabilities, where the payload's position error is reduced up to 60% for light to medium sea states.

Position-Commanding Anti-Sway Controller for 2-D Overhead Cranes Under Velocity and Acceleration Constraints

This paper proposes an anti-sway controller for two-dimensional overhead cranes. The controller is of the position-commanding type, i.e., it sends position commands to the position-controlled trolley, and it uses the sensor information of the payload sway angle. The position commands are determined so that the trolley tracks the desired position signal sent from an upper-level controller and also so that the payload sway is damped. The sway damping is realized by a leaky integral controller, which employs a high-pass filtered time integral of the sway angle. In addition, arbitrary limits can be imposed on the first and second derivatives of the position command, and thus it is applicable to cases where the desired position signal from the upper-level controller is nonsmooth or discontinuous. Due to these features, the controller is expected to be useful in both human-operated and autonomous systems. The controller was validated with a laboratory setup. This paper also presents an algorithm that can be attached to the proposed controller to prevent the overshoot, which can take place when the desired position signal is discontinuous.

Event-triggered global sliding mode controller design for anti-sway control of offshore container cranes

This paper proposes an event-triggered global sliding mode based anti-sway control for offshore container cranes. Its main objective is to guarantee the robust tracking performance of containers transferred by cranes installed on cargo ships, while saving the transmission resources. To this end, a suitable sliding manifold is formulated with the desired motion properties. A global sliding mode control is then synthesized to maintain stability of the system and ensure robustness against disturbances such as sea waves and wind induced movements. Finally, the event-triggered strategy is considered in the implementation phase to generate the sampling instant at which the control signal is updated, thereby minimizing communication resources and execution time. Using the Lyapunov's stability theory, it is proven that the controlled system reaches the manifold and equilibrium point from any initial state. We also prove that the proposed approach is free from the Zeno solution, i.e., a phenomenon when the infinite triggering instants exist in a limited time range. Eliminating the reaching phase of traditional sliding mode control, overcoming the effect of the disturbances during the entire dynamics, optimizing resources at the implementation phase, and removing the Zeno phenomenon are among the main advantages of the proposed control approach.

Heave and horizontal displacement and anti-sway control of payload during ship-to-ship load transfer with an offshore crane on very rough sea conditions

Ship-to-ship load transfer with offshore cranes is challenging in rough sea conditions because of the difficulty in compensating for the increased position-velocity-acceleration errors and the restriction of the unloading area.This study proposes an efficient solution by integrating the combined vertical, horizontal, and anti-swing control system, experimentally validated mathematical hydraulic system and ship motions on irregular waves, the dynamic model of the crane, and an innovative control strategy. Particle Swarm Optimization-Proportional-Integrative-Derivate (PSO-PID) Trajectory Route Control System ensures safe unloading by advancing in the desired vertical position and speed route. The operation's horizontal positioning is realized even for very rough sea conditions with the support of the PID-controlled main and elbow boom. An extra added telescopic boom is used for anti-swing control with Particle Swarm Optimization Proportional-Derivative-Second Derivative (PSO-PDD2) control system.Simulations with different sea conditions were made and analyzed to verify the study's system model's effectiveness. The simulation results revealed that the system model is a valid and successful solution.

Haptics-based force balance controller for tower crane payload sway controls

Anti-sway control is an important issue affecting the safety and efficiency of tower crane operation, but the role of the human operator in this control loop is largely unknown. This paper proposes and designs a force-feedback based control method for anti-sway control. The system connects the tips of two haptic devices by a 3D printed pole and uses it to provide the balance status of the payload. The sway error is represented by the position and rotation changes of the pole. Meanwhile, the operator can use this haptic controller to adjust the payload pose by applying the counterbalance force to the pole. A human-subject experiment (n = 34) was performed to test the comparative benefits of the proposed method. The results show that the proposed haptics-based force balance control method outperformed the automatic method in both performance and subjective evaluations. The findings inspire the design of new human-in-the-loop approaches for heavy machine stability controls.

Upgrading for overhead crane anti-sway method using variable frequency drive

The paper discusses about upgrading the overhead crane anti-sway method base on the induction motor torque control from rotor resistance starter to variable frequency drives (VFDs). The upgrading included two phases. The phase 1 is to identify the performance of the overhead crane operation on anti-sway method base on the induction motor torque control using rotor resistance starter (old existing motor starter). The phase 2 is to identify the performance of the overhead crane operation on anti-sway method base on the induction motor torque control that use a variable of frequency drive (new upgrading motor starter). The primary equations connecting tractive force and load sway angle, which the motor torque control law is based on is designed for 0% load wobble at the end of the journey. The words accelerating and braking have been written. Outcomes of modelling the behaviour of a trolley-load of two masses for the normal overhead crane load ratios, a system is described weight to the length of the rope, which supports the hypothesis concerning the feasibility of direct load anti-sway control ON and OFF for regulation of motor for overhead cranes.

Anti-Sway Control on a Harbor Crane System Using a Command Smoothing Iterative Method

The requests for relatively large-sized mobile harbor cranes are increasing. Typically, harbor cranes are self-traveling but do not require any additional civil works to improve the bearing strength of foundation soil. This work describes a novel method able to reduce the sway of a suspended load during the slewing motion of a Harbor Crane. The proposed method is based on an iterative calculation of the sway angle, and the corresponding applied velocity profiles as input to the crane motors. The 'command smoothing' method is used to reduce the sway: additional damping is introduced into the system to control the sway. The multiple-input and multiple-output (MIMO) mechanical system is modeled by a set of non-linear differential equations in which the mathematical model is divided into two subsystems: the first for actuated outputs and the second for underactuated outputs. After defining the stability of the proposed solution and the kinematics of the hydraulic actuators on the boom, a detailed mathematical model is developed, taking into account the non-linear components of the forces, such as centrifugal and Coriolis forces, on the system. Simulation results show that the proposed anti-sway method can dampen the suspended load's oscillations during the harbor crane's slewing movement.

분석적 계층화 기법을 활용한 환자이승로봇 흔들림 제어기의 최적 제어 파라메터 선정 방법

In this study, a method of deriving the optimal control parameters in the design of an anti-sway controller for a patient transfer robot is proposed. Patient transfer robots are used in medical facilities to move patients who cannot move on their own. However, the sway that occurs in the process of moving a patient on a patient transfer robot not only threatens the patient’s safety, but also creates anxiety. To control such sways, this study proposes the analytic hierarchy process as a method for designing a controller that satisfies a given control specification and at the same time designing an optimal controller for various control gains. Simulation results demonstrate a control performance that satisfies the control specifications.

Self-tuning anti-sway control for shipboard cranes providing combined world and deck-frame compensation

This paper presents a novel self-tuning anti-sway control system for shipboard cranes that provides full, six degree-of-freedom (DOF) motion compensation with respect to both the world (ocean) coordinate frame and the ship deck coordinate frame. The system can either manually or automatically switch between compensation modes during operation, and is capable of providing anti-sway action while tracking a time-varying operator input. Rather than requiring the operator to provide individual joint control, the entire system can track a simple three-axes Cartesian input from the operator, while simultaneously providing full anti-sway compensation in either coordinate frame.High-fidelity simulation case studies were performed with a nine-DOF shipboard knuckle boom crane, which included double pendulum dynamics between the hook and payload, in the presence of full six-DOF ship motion at sea-state six. The self-tuning anti-sway system showed at least a 92.70% reduction in payload tracking error when the corresponding compensation mode (either deck or world-frame) was activated, a significant reduction in undesired payload motion. Wind disturbances were added to the simulation using the Dryden wind model, where the system showed a maximum decrease in performance of only 0.73%; additional tests were run with self-tuning disabled, which resulted in a decrease in performance of up to 101%, indicating self-tuning is highly effective at minimizing the effect of wind disturbances.

Anti-Sway Control for Overhead Cranes Following Target Position Commands from Operators under Velocity and Acceleration Constraints

Anti-Sway Control for Overhead Cranes Following Target Position Commands from Operators under Velocity and Acceleration Constraints