Payload Swing Research Articles

A time optimal trajectory planning method for offshore cranes with ship roll motions

With the fast development of the economy, marine activities are increasing. Due to the advantages of offshore cranes, they are widely used in marine production as effective transportation tools. As a matter of fact, the offshore crane works on the ship known as a typical noninnertial system, which is affected by the ship movement. To tackle this problem, we propose a time optimal trajectory planning method for the considered offshore crane. Specifically, to tackle the couplings between state variables, we show that the offshore crane system is differentially flat with the payload coordinates as the flat outputs. Based on this fact, the planning problems for the jib motion and the rope length are further converted into the planning problems for flat outputs. Then, in order to ensure the trackability of the planned trajectory and improve the safety, we consider a series of physical constraints including the jib luffing motion velocity and acceleration constraints, the rope length varying velocity and acceleration constraints, and the payload swing angle and angular velocity constraints, and then a time optimization problem is further formulated. By utilizing a bisection-based method, the optimal payload transportation time is obtained as well as the corresponding time optimal trajectories. As far as we know, it is the first time optimal trajectory planning method designed for offshore cranes to achieve the fast and accurate payload transportation as well as the payload swing elimination in earth-fixed frame. At last, the effectiveness of the proposed method is verified by simulation tests.

Multibody system dynamic analysis and payload swing control of tower crane

A new payload swing control method considering the vibration of tower crane is proposed in this study. The coupling between the structural vibration and the payload swing is neglected in existing studies on tower crane swing suppression. Changes of sling length are considered as disturbances. They cause the existing methods of swing suppression method ineffectual in the actual working situation. In contrast, the structural vibration of the tower crane is taken into account in this study. At the same time, the sling length is regarded as a control variable to reduce the payload swing. A new swing suppression algorithm is proposed in conjunction with phase plane analysis method. In addition, a systematical tower crane multibody system dynamic analysis platform with changing of sling length is established to verify the effectiveness of the algorithm. The traditional finite element method is used to model the tower body and boom of tower crane while the Arbitrary Lagrange Euler Absolute Nodal Coordinate Formulation (ALE-ANCF) cable element is applied for modeling the sling. This two parts are connected with sliding joint obtaining the tower crane multibody system model. Numerical examples show that the proposed method can reduce the swing amplitude the payload effectively when considering the coupling between the structural vibration and the payload swing.

ANALYSIS ON ANTI-OVERTURNING STABILITY OF A TRUCK CRANE BASED ON ZERO MOMENT POINT THEORY

Truck crane stability has been a hot research issue. It is a conventional method used to calculate the moments equilibrium when analyzing stability. However, errors can occur because of the lack of dynamic simulation in conventional methods. Hence, to minimize errors, this study utilized the zero moment point (ZMP) theory to calculate the maximum lifting capacity of the truck crane considering the dynamic load, and proposed an anti-overturning detection method based on the theory. First, the model of the truck crane was established and the solution formula of ZMP was obtained. From the Lagrange equation, the dynamic model of payload oscillations was analyzed during crane operations. Second, the ZMP theory was used to analyze the stability of the truck crane and derive the maximum payload. Next, the experiment was conducted to measure the pressure of the four outriggers and their center of pressure (CoP) during hoisting, luffing, and slewing operations were calculated. Compared to stable movement, the CoP would vibrate irregularly, consequently reducing the lifting capacity of unstable motion. Finally, the anti-overturning detection method is proposed based on ZMP and CoP. Results demonstrate that the reduction of lifting capacity is caused by the dynamic load. The payload swing has a larger effect on the maximum lifting capacity than hoisting, luffing, and slewing motions. The maximum payload can decrease with the increase of the swing angle. The proposed method provides a correct judgment on the stability of the truck crane, which can accurately predict the overturning state of the crane and reduce the risk in the operation. Keywords: truck crane, overturning, zero moment point, center of pressure, stability

Input shaping with an adaptive scheme for swing control of an underactuated tower crane under payload hoisting and mass variations

An underactuated tower crane exhibits a significant payload sway especially under three simultaneous motions involving trolley displacement, jib rotation and payload hoisting. This paper proposes an input shaper with an adaptive scheme for payload swing control of a tower crane under those effects together with varying cable lengths for payload hoisting and various payload masses. The control approach has an advantage in its capability to adapt and update the Zero Vibration Derivative shaper parameters in real-time according to the changes in the system parameters. This is achieved by using a non-linear input–output mapping of the parameters developed using the neural network. To test the effectiveness of the proposed controller, experiments are carried out on a laboratory tower crane under several challenging conditions involving payload lowering and lifting operations, variation in speeds of motion, and using different payload masses up to ± 50% variations from an original mass. Experimental results show that the proposed shaper is robust towards the parameter uncertainties with low overall and residual payload sways under all testing conditions. Its superiority is confirmed by improvements of at least 49% and 76% in the payload lifting operation while 38% and 68% in the payload lowering operation for the overall and residual sways respectively over a robust Extra Insensitive shaper designed using an average operating frequency. In addition, the performance of the proposed controller is not affected by the variations in the payload masses and motion speeds.

Energy-based nonlinear adaptive control for collaborative transportation systems

As an ideal method for heavy or large payload delivery, collaborative aerial transportation with multiple unmanned aerial vehicles (UAVs) increases the load capacity. However, during the transportation process, collaborative transportation systems are always subject to environmental disturbances and system uncertainties, which poses a great challenge to safe and efficient payload transportation. Existing works without payload angle information in control inputs cannot exhibit satisfactory antiswing performance. To handle the aforementioned issues, this paper proposes a novel control strategy for rapid UAV positioning and payload swing elimination. Specifically, the dynamic model of the collaborative transportation system is described based on a redundant dynamic expression. Then, an artificially constructed UAV-payload unified signal is introduced to enhance the state coupling between the UAV positions and payload swing angles. Based on the newly defined signal, the energy storage function is constructed and the adaptive control law is derived. Additionally, the detailed Lyapunov analysis is provided to prove the system stability and convergence. It is worth noting that the difficulty of the stability analysis is greatly reduced with the help of the established redundant dynamic description. To validate the performance of the proposed control strategy, experimental studies have been carried out in different scenarios. Hardware experimental results show that the proposed method can effectively suppress load swing while ensuring rapid UAV positioning, even with external disturbances.

The Crane Operator's Trick and other Shenanigans with a Pendulum.

The dynamics of a swinging payload suspended from a stationary crane, an unwanted phenomenon on a construction site, can be described as a simple pendulum. However, an experienced crane operator can deliver a swinging payload and have it stop dead on target in a finite amount of time by carefully modulating the speed of the trolley. Generally, a series of precisely timed stop and go movements of the trolley are implemented to damp out the kinetic energy of the simple harmonic oscillator. Here, this mysterious crane operator's trick will be revealed and ultimately generalized to capture the case where the load is initially swinging. Finally, this modus operandi is applied to a torsion balance used to measure G, the universal gravitational constant responsible for the swinging of the crane's payload in the first place.

Online Trajectory Planning Method for Double-Pendulum Quadrotor Transportation Systems

This study investigates the trajectory planning problem for double-pendulum quadrotor transportation systems. The goal is to restrain the hook swing and payload swing while achieving precise positioning. An online trajectory planning method with two capabilities—precise positioning and swing suppression—is proposed. The stability and convergence of the system are proved using the Lyapunov principle and the LaSalle’s invariance theory. Simulation results show that the proposed method has excellent control performance.

Automatic parameter selection ZVD shaping algorithm for crane vibration suppression based on particle swarm optimisation

Abstract This work introduces the foundation of a new class of input shaping algorithm, designed based on the particle swarm optimisation. This algorithm is utilised to control the residual vibrations in the crane system. The motivation is the development of simple algorithms and architecture for controlling the motion in under-actuated nonlinear systems with minimal modelling effort. By recording the payload swing signal of the crane only once, the approach can automatically calculate the optimisation amplitude and time locations of the impulses required by a common zero-vibration-derivative (ZVD) technique. In this work, we use this algorithm to design a ZVD shaper for controlling the motion of an under-actuated nonlinear crane model system. We validate the approach using experiments. If this algorithm is implanted into the embedded system and applied to the actual crane, which will solve the problem of the traditional ZVD parameter adjustment and improve the vibration suppression effect of the ZVD Algorithm.

Nonlinear vibration suppression control of underactuated shipboard rotary cranes with spherical pendulum and persistent ship roll disturbances

Shipboard rotary cranes are widespread used in industrial fields to carry out large-scale cargoes under marine environment, which are a class of representative nonlinear systems. For crane systems, there exist unactuated state variables (e.g., payload swing angles), which hence make them typically underactuated systems, whose degrees of freedom (DOFs) are more than the number of control inputs. Besides, due to the complexity disturbances of the marine environment, there are always inaccuracies in the three-dimensional (3D) dynamics model of shipboard rotary cranes, such as ocean waves, wind waves, ocean currents and so on, which make the control methods hard to achieve the perfect control effect. Most of the existing methods are built on the basis of simplified linear model, which often require precise model parameters or velocity signals. In order to solve the control problems caused by the above uncertainties, this paper proposes two nonlinear anti-swing control methods. First, considering the uncertain parameters, an adaptive controller is designed, which can achieve the control effect of suppressing swing when the model has unknown parameters. Second, considering the unmeasurable velocity signals, an output feedback controller is designed, which can achieve the control effect to suppress the swing angle with no need of velocity signals. On the basis of the above two control methods, we design corresponding different energy storage functions including kinetic energy and potential energy, respectively. Specifically, this paper has achieved an excellent effect of restraining swing without any linear approximation of the dynamic model. Lyapunov theorem and LaSalle invariance principle are utilized to further prove the asymptotic stability of the closed-loop system. Finally, experiments are implemented to further demonstrate the effectiveness of the proposed control methods.

A New Payload Swing Angle Sensing Device and Its Accuracy.

Measuring the swing angle of a crane load is a relatively well-known but unsatisfactorily solved problem in technical practice. This measurement is necessary for the automatic stabilization of load swing without human intervention. This article describes a technically simple and new approach to solving this problem. The focus of this work is to determine the accuracy of the measuring device. The focus of this work remains on the design, the principle of operation of the equipment, and the determination of accuracy. The basic idea is to apply the strain gauge on an elastic, easily deformable component that is part of the device. One part of the elastic component is fixedly connected to the frame; the other part is connected to the crane rope by means of pulleys close to the rope. In this way, the bending of the elastic component in proportion to the swing angle of the payload is ensured.

Anti‐swing control and trajectory planning of quadrotor suspended payload system with variable length cable

AbstractDifferent from the quadrotor suspended payload system with fixed length cable, the system with variable length cable can load and unload cargoes more efficiently under many conditions. This paper presents a method of modeling, control, and trajectory planning for a quadrotor suspended payload system with variable length cable. In order to effectively reduce the swing of the slung payload under the quadrotor, a coupled dynamic model and an integral backstepping control scheme for the system are designed, and a basic trajectory planning is carried out. The presented coupled dynamic model is composed of two parts, one is the dynamic equation of the quadrotor with payload pull, and the other is the dynamic model of the payload pendulum angles with variable length cable related with quadrotor flight acceleration. Meanwhile, the interaction forces between them are calculated. Based on the coupled dynamic model of the system, a cascade control scheme with trajectory planning is designed. The attitude and position control loop of the system adopt the integral backstepping algorithm to solve the reliable flight of quadrotor with slung payload. At the same time, the flight trajectories are generated by trajectory planning as the reference input of the control system, which can further reduce the payload swing. Simulation results show that the proposed scheme can realize stable and reliable flight of the quadrotor and limit the pendulum angles within the desired range to reduce the payload swing.

Adaptive Control for a Quadrotor Transporting a Cable-Suspended Payload With Unknown Mass in the Presence of Rotor Downwash

This paper investigates the control problem for a quadrotor with a cable-suspended payload (QCSP). A new adaptive control strategy is designed to control the velocity of a volumetric payload with unknown mass in the presence of rotor downwash. The asymptotic stability of the resulting closed-loop system is analysed via the Lyapunov method. Furthermore, a novel structure is designed to suspend the payload on the quadrotor by a cable, and a gyroscope is installed on this structure to measure the payload's swing angle. The designed controller's performance is demonstrated by simulations implemented in a Simulink/SimMechanics environment. The effectiveness of the proposed control scheme is validated in real experiments.

Precision-positioning adaptive controller for swing elimination in three-dimensional overhead cranes with distributed mass beams

As a type of dispensable transport tool, overhead cranes are extensively applied in large industrial sites to transport containers and goods due to their extraordinary convenience and efficiency. However, various transport requirements and working environments may cause some adverse effects for overhead crane control. In particular, in some transport tasks, distributed-mass beams (DMB) are required to be transported smoothly to a specific position. Hence, most existing controllers designed for crane systems with point-mass payload (PMP) cannot meet the control requirements. For example, controllers designed for crane systems with PMP do not consider the moment of inertia of DMB, thus, the residual payload swing caused by the moment of inertia cannot be completely suppressed, which may cause safety risks. Additionally, due to various working environments, inaccurate estimation of frictions can result in errors in positioning. To solve the above issues, this paper conducts the dynamic analysis of three-dimensional (3-D) overhead crane systems with DMB and designs an improved adaptive controller which can provide favorable control for state variables. In particular, the proposed update laws can compensate for the uncertainties of crane systems. Based on a tracking trajectory, the trolley and guide rail can both reach the preset position, and the swing angles are also well eliminated throughout the transport process. The stability of the control system is proven theoretically, and the performance of the proposed controller is verified by comparative experiments.

Nonlinear antiswing control for offshore boom cranes subject to ship roll and heave disturbances

This paper studies the automatic control problem of offshore boom cranes, which often work in harsh sea conditions. First, some novel composite signals are elaborately designed, which consist of both payload swing information and boom/rope positioning error. By utilizing the composite signals as feedback, the constructed nonlinear controller manages to react more efficiently to the uncertainties/disturbances, and hence achieves better overall control performance and stronger robustness. Particularly, the control gains are updated in real time according to the system dynamic response, so as to further improve the efficiency of the designed controller. Through rigorous mathematical deductions, it is proved that the system state variables converge to the desired values asymptotically. The conducted experiments show that the proposed method can accurately position the payload, while simultaneously suppressing its swing motion.

Jib Vibration and Payload Swing of Tower Cranes in the Case of Trolley Motion

Jib Vibration and Payload Swing of Tower Cranes in the Case of Trolley Motion

A segmented energy‐based nonlinear tracking control method for quadrotor transport system

AbstractThe safety of the quadrotor transport system (QTS) is always threatened by the suspension load swing under the fuselage during flight. At the same time, the QTS is affected by uncertainties such as changes in desired position and cable length. Trajectory planning is often neglected during the development of the controller. Moreover, there are some shortcomings in the most control methods such as the maximum speed, acceleration, payload swing, and transportation efficiency of the system that cannot be theoretically guaranteed. Therefore, a nonlinear tracking control method is proposed using the segmented energy, which can make the quadrotor move to the target position quickly and smoothly, meanwhile, suppress the heavy swing of the payload. Furthermore, it is proved that the method proposed in this paper can achieve the asymptotic stability of the system equilibrium point and converge to the expected value by Lyapunov theorem and LaSalle's invariance principle. Simulation results show that the control method achieves good control performance and strong robustness against system parameter uncertainty.

Robust observer-based anti-swing control of 2D-crane systems with load hoisting-lowering

A new model-free robust control scheme for payload swing angle attenuation of two-dimensional crane systems with varying rope length is introduced in this work. The proposed controller consists of a proportional derivative controller, a disturbance observer, and a compensation term that includes a coupling function. A proper design of the coupling function allows attenuating the magnitude of the swing angle, while the disturbance observer permits reducing the effect of internal and external disturbances. Then, a rigorous stability analysis demonstrates that the proposed controller allows the system to follow a desired translational motion and hoisting/lowering the load with small payload oscillations despite the adverse effects caused by internal and external disturbances. In the proposed scheme, a stage devoted to the design of the reference signal is also encompassed. The new methodology is compared to a robust controller and an adaptive scheme. Exhaustive numerical simulations demonstrate that the new controller’s performance outperforms the other control techniques, despite the presence of endogenous and exogenous disturbances.

Study of anti-swing control of ship cranes based on time delay feedback

2 tons 3 meters ship crane as the research object, establish the complete mathematical model of ship crane, and design the time-delay feedback control algorithm to eliminate payload swing on the basis of the built mathematical model. First, a high-precision potentiometer is used to measure the in-plane and out-of-plane oscillation of the payload. Measuring devices for the rotary angle and variation amplitude angle are created, and the anti-swing control hardware system is built by the sensing unit and the High-Speed Data Acquisition hardware system. Secondly, the control software on the VB platform is developed using the time-delay feedback algorithm. Experimentally study the effect of time-delayed feedback controller on payload swing elimination, and use induction method to get the optimal control parameters of the time-delayed feedback control algorithm. At last, the AMEsim-ADAMS co-simulation platform was built to evaluate the payload sway of the ship crane under simulated working conditions. The results show that: the hardware and software systems for anti-swing control built-in the paper can give the real-time and the exact payload swing angles. The method of adding time-delay feedback control signal to the slewing operation signal can achieve better anti-swing effects than the others. At the same time, the delayed feedback control algorithm still has a nice control effect in the case of virtual ship deck motion.

Analytical analysis and oscillation control of payload twisting dynamics in a tower crane carrying a slender payload

Tower cranes suspending slender payloads are widely used in the construction site. Both the payload swing and twisting degrade the efficient and safe operation. However, the twisting dynamics is more complicated than the swing dynamics. Although numerical analysis of the twisting dynamics has been reported, little attention has been directed at the analytical analysis of the twisting dynamics. A new dynamic model including swing and twisting has been derived in this article. The analytical analysis of the twisting dynamics from the new model has been described. The closed-form solution for estimating frequencies of the payload twisting have been presented. In addition, a new control method is proposed for suppressing swing and twisting in tower cranes transporting slender payloads. The control method has good robustness to variation in working conditions and system parameters, and good performance in rise time. Numerous simulations and experiments demonstrated the key dynamic behavior of the payload twisting and effectiveness of the control method.

Dynamic Modeling and Analysis of the Telescopic Sleeve Antiswing Device for Shipboard Cranes

In order to explore the dynamic characteristics of the telescopic sleeve antiswing device for shipboard cranes under coupling excitation, a three-dimensional dynamic model of the ship crane telescopic sleeve antiswing device is established in this study, and the accuracy of the model is verified through experiments. By dynamic analysis, the influence of sleeve extension and contraction, damper parameters, and ship excitation on the payload swing is found; meanwhile, the influence of payload swing on ship stability is discovered. At the same time, the simulation results show that the three-dimensional dynamic model can accurately simulate the swing reduction characteristics of the antiswing device. The in-plane and out-plane angles of the swing are reduced by 70% and 90%. The research results have great significance to further explore the antiswing mechanism and structural design of the mechanical antiswing device.