Payload Sway Research Articles

Dynamic Modelling and Feed-forward Control of an Overhead Crane

The article presents: modelling, simulation, and controller design of a laboratory overhead crane system. A nonlinear model was developed using Lagrange equation and linearization process is performed for the purpose of analysis and controller design. Accuracy of the linear model is assessed by comparing simulation results of nonlinear and linear dynamic equations. A feed-forward control based on a low-pass filter was designed based on the crane dynamics. The controller performance is discussed in terms of trolley position response and payload sway reduction. The proposed control approach is able to suppress the payload sway, but at the expense of a slight delay in the trolley motion

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.

Comparative analysis on the performance of different types of input‐ and command‐shaping controllers in minimizing payload residual vibration of an overhead crane with an inclined supporting track

AbstractReducing the effects of external disturbance on overhead crane systems is crucial, as they can impair the controller performance and cause excessive vibrations or oscillations of the payloads. One such external disturbance is the inclination of the supporting track of the crane trolley, which causes the system dynamics model to change. An open‐loop control strategy is widely utilized to control the payload sway motion and generally does not require any alterations in the physical structure of a system or the installation of sensors and/or actuators. Input and command shaping are two common open‐loop control techniques applied to control overhead cranes. In this paper, the effect of moving an overhead crane system along an inclined supporting track is investigated. In addition, the ability of different types of input‐ and command‐shaping control schemes to suppress the residual vibrations due to trolley track inclination is demonstrated. Two types of input‐shaping controllers, which are double‐step, zero vibration, and one command waveform (WF) shaper based on a trigonometric function, are used and tested. A linear equation of motion of the overhead crane resting on an inclined surface is developed to simulate the overhead crane and payload motion. The effectiveness of the different types of open‐loop controllers to suppress residual vibrations is verified by both simulation and experimental results. In addition, a new WF command shaper is proposed and designed to overcome track inclination while eliminating payload residual vibration. A comprehensive comparative analysis, both numerically and experimentally, is performed on the new proposed shaper to measure its effectiveness in handling inclination when compared to other types of open‐loop controllers. The new shaper outperforms other controllers in eliminating payload residual vibration for a wider range of inclination angles.

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.

Observer-based Control Design for Overhead Crane Systems

This paper proposes an observer-based control design with Disturbance Feedback Control (DFC) for overhead crane systems. DFC is a technique to improve the disturbance rejection capabilities of existing control loops. The crane system is modelled with 3D dynamics and linearized. Payload sway angles are estimated by a Kalman Filter. A state feedback controller for setpoint tracking and a DFC for disturbance rejection are designed using Linear Matrix Inequalities. Both simulation and experimental results show that the observer-based control with DFC can estimate the sway angle and is able to attenuate disturbance inputs better than the conventional observer-based control. The proposed design can thus achieve practical angle sensor-less control with a retro-fit modification of an existing control.

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.

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.

Development of payload sway suppression control technology simulated repowering for the crane

Development of payload sway suppression control technology simulated repowering for the crane

Fine tuning of a PID controller with inlet derivative filter using Pareto solution for gantry crane systems

Gantry cranes are widely used in transporting heavy loads in construction projects and critical industries such as petrochemical industry and nuclear power stations. Their mission should be accomplished with as high accuracy for the trolley positioning, and minimum values of sway oscillation angles as possible. So, the control strategies aim to achieve high productivity (through transporting the trolley with good precision) while considering safety precautions (through eliminating sway oscillations). One of the linear closed loop control methods is using PD and PID controllers. This research provides a non-linear mathematical model for single-pendulum gantry crane with two stable control schemes that depend on PID and PD controllers equipped with inlet derivative filter for every scheme. The two control schemes utilize a PID controller for positioning the trolley and a PD controller for eliminating undesired sway angles of the payload. In the second scheme, the input voltage control signal is always saturated to be positive to preserve the direction of rotation of the driving DC motor. The controllers include up to five gains and two inlet derivative filter coefficients which are tuned using Multi-Objective Genetic Algorithm (NSGA-II) with four different fitness functions and one weighted function to choose a suitable solution from other Pareto solutions. The simulation results are presented to show the superiority of the second scheme precision in trolley transporting with minimum payload sway oscillations.

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.

Adaptive Neural Network Tracking Control for Double-Pendulum Tower Crane Systems With Nonideal Inputs

A novel adaptive neural network tracking control method is systematically investigated for a unique double-pendulum tower crane system model in this article. Several critical and practical application-oriented control issues, including robustness, tracking error limitation, double-pendulum effects, and input dead zone nonlinearity, are considered simultaneously, which have never been well addressed in the existing literature. Technically, neural networks are employed to approximate the functions with uncertain/unknown dynamics and nonideal inputs. Several barrier Lyapunov functions are proposed that can circumvent the violation of tracking error limitations in the proposed control method. Importantly, based on the designed adaptive neural network tracking control method, the jib and trolley can track their desired trajectories very fast, and the hook and payload sway can be completely eliminated. The Lyapunov stability theory and Babalat’s lemma are utilized to theoretically prove the convergence and stability of the proposed control system. Finally, well-designed simulation studies are carried out to verify the excellent performance and strong robustness of the control method. This article should be the first work considering a double-pendulum tower crane system with guaranteed convergence and performance without any linearization for the original nonlinear dynamic model.

Algorithms for cable-suspended payload sway damping by vertical motion of the pivot base

The solution of a case study problem of suspended payload sway damping by moving a pivot base in vertical direction is presented. Unlike for the classical problem of anti-sway control for moving the base in the horizontal direction, implemented e.g. in cranes, a direct solution by using control feedback theory for linear systems is not possible. Once the model is linearized, it becomes uncontrollable. Thus, a derivation of a nonlinear controller is needed to solve the task. In this context, two solutions are proposed. The first solution is based on imposing harmonic motion of the base with double frequency of the payload natural frequency. Synchronization of the base and the payload deflection angle is done either by proportional time-delay controller or by proportional-derivative delay free controller. Secondly, the Lyapunov’s second method is directly applied to derive a nonlinear controller. For both cases, balancing the dissipated energy, rules for determining equivalent damping are explicitly derived. After discussing and solving the corresponding implementation aspects, both simulation and experimental validations are performed. The experimental validation is performed on a simplified problem, where only horizontal motion is possible. The simulation based validation is performed on a nonlinear two dimensional model of a quadcopter carrying a suspended payload.

A generalized approach to anti-sway control for shipboard cranes

Payload sway for shipboard cranes represents a significant safety concern for deck personnel. In this paper, a generalized trajectory modification strategy is presented that can be applied to a variety of different types of shipboard crane to allow the payload to maintain its desired position with respect to the ship deck in the presence of six degree of freedom (DOF) ship motion, and therefore appear stationary to deck personnel. Initially developed for a five DOF shipboard gantry crane, both a de facto proportional-integral-derivative (PID) controller and a sliding mode controller (SMC) are shown in simulation to be successful at tracking the modified trajectory. The PID controller shows a 64% reduction in the root-mean-square-error (RMSE) between the desired and actual payload positions with the addition of the trajectory modifier, and the SMC shows a 74% reduction. The ship is actuated with six degrees of freedom in the simulations; however, the trajectory modification anti-sway control system only requires the measurement of the ship’s roll and pitch angles.The trajectory modifier is then applied to a six-DOF shipboard knuckle boom crane, with a dynamic model developed to include the mass and inertia of the actuators. The PID controller only shows a 38% reduction in RMSE and struggles to successfully track the trajectory due to the highly nonlinear dynamics of the knuckle boom crane. The SMC controller shows an 82% reduction in RMSE and appears capable of maintaining the desired payload position with the addition of the trajectory modifier.To further extend the dynamic model of the knuckle boom crane, first-order transfer functions are applied to govern the response of each actuator. A state-of-the-art sliding mode controller is developed to provide stable control of the system, and shows an 84% reduction in RMSE with the addition of the trajectory modifier. The results therefore indicate that trajectory modification is highly effective at dampening payload sway for shipboard cranes, provided a suitable controller can be developed to allow the crane to accurately track the modified trajectory.

Observer-Based Nonlinear Control for Tower Cranes Suffering From Uncertain Friction and Actuator Constraints With Experimental Verification

Tower cranes are a class of important and useful tools for the transportation of large cargoes, especially in high building construction. Moreover, the combination of jibs' rotational movements and trolleys' translational movements can fulfill three-dimensional payload transportation in a huge outdoor workspace. However, complicated dynamics and different unfavorable environmental conditions in practice make the effective control of tower cranes very challenging. In this article, based on the original dynamic models without any linearization manipulations, we present a new output feedback control method to accomplish rapid jib and trolley positioning and payload sway suppression. In particular, the velocity signals are accurately obtained by an elaborately designed observer, instead of numerical differentiation manipulations to the measurable output variables (which may distort the original velocities to some extent). Based on the velocity estimates, the suggested controller can also handle uncertain friction. Additionally, the actuator constraints are fully considered during controller design, i.e., the calculated control inputs are both within the permitted ranges, thereby avoiding actuator saturation and degrading the control performance. For the entire closed-loop system, including the proposed controller, the state observer, and tower cranes, the asymptotic stability is strictly proven by Lyapunov-based techniques. Finally, some comparative and robustness verifications are implemented by hardware experiments.

Efficient control of a 3D overhead crane with simultaneous payload hoisting and wind disturbance: design, simulation and experiment

This paper proposes a new control scheme for a 3-dimensional (3D) overhead crane having simultaneous payload hoisting and persistent wind disturbance. Control of the 3D crane system under those effects is highly challenging as it results in a high unwanted payload sway and inaccurate payload positioning. The proposed control structure which combines a new adaptive command shaping technique designed based on output signals and an integral sliding mode (ISM) control provides a precise crane positioning and low payload sway. The two independent controllers are designed such that they can practically be combined and implemented without affecting the overall stability of the closed-loop system. To test the effectiveness of the proposed method, simulations and experiments on a laboratory overhead crane are carried out under various conditions with different payload masses, various cable lengths, payload hoisting and external wind disturbance. Under all operating conditions, by comparing with an ISM control, the combined controller gives smoother and more satisfactory transient responses with two to four-fold reductions in the overall payload sway. In addition, the controller provides substantial reductions in the overall chattering of the control signal and sliding manifold which resulted in smoother control signals and system responses.

Energy coupled–dissipation control for 3-dimensional overhead cranes

Handling loads with small swings is difficult for a 3-dimensional overhead crane due to its hard nonlinearity. Moreover, the nonlinear dynamics increases the complexity of the required feedback, thus making the closed-loop system sensitive to a variation in the cable length that negatively influences the damping feature. To address these problems, a significant storage function characterized by the desired damping is constructed based on passivity. Consequently, a nonlinear controller is delivered by enforcing the coupled–dissipation inequality, thus drastically increasing the damping of the closed-loop system. In particular, new coupled–dissipation signals are fabricated to augment the coupling between the trolley movement and the payload sway. Due to its very simple structure that excludes the cable length, the proposed controller is robust to unknown cable lengths and easy to implement. In the frame of the Lyapunov theory, LaSalle’s invariance principle is applied to illustrate the corresponding stability. The effectiveness of the proposed control on improving the system performance is verified through simulation results.

Partially saturated coupling-based control for underactuated overhead cranes with experimental verification

This paper presents a partially saturated coupling-based controller for underactuated overhead cranes. A new storage function characterized with a desired inertia matrix and potential energy function is constructed, which is especially quadratic in a composite state vector, and subsequently, a nonlinear controller is designed by enforcing the coupled-dissipation inequality. Particularly, a composite signal is fabricated to augment the internal coupling between the trolley movement and the payload sway, thus drastically increasing the damping of the control system. The proposed controller is simple and very robust to different/uncertain cable lengths. Besides, the hyperbolic tangent function is adopted so that the proposed controller guarantees a soft trolley motion. In the frame of the Lyapunov theory, LaSalle’s invariance principle is applied to illustrate the asymptotical stability. Simulation and experimental results are presented to verify the effectiveness of the control system.

Experimental verification of a hybrid control scheme with chaotic whale optimization algorithm for nonlinear gantry crane: A comparative study

This paper proposes an experimental verification of a hybrid partial feedback linearization (PFL) and deadbeat (DB) control scheme as in Hamdy et al. (2018) with chaotic whale optimization algorithm (CWOA) for a nonlinear gantry crane (GC) system. The PFL linearizes the nonlinear model to end up with a linear closed-loop system. The DB controller is utilized for the desirable accelerated response without any oscillation or undesirable effects on the internal dynamics stability. The CWOA is used to tune the controller parameters. A sliding-mode observer (SMO) is utilized to estimate the unmeasured states. Using this hybrid scheme, a better payload sway elimination can be obtained. Finally, the experimental results are presented to illustrate the efficiency and the effectiveness of the proposed scheme with a comparative study.

Determination of Reaction Forces of a Deck Crane in Wave Motion Using Screw Theory

In this paper, we present a method for calculating reaction forces for a crane mounted on a ship moving in waves. The method is used to calculate the reaction forces between the crane base and the vessel deck. This includes the case where the crane is mounted on the platform that keeps the base of the crane horizontal when the vessel is moving in roll and pitch. The wave motion of the ship is modeled with force response amplitude operators (RAOs) based on the JONSWAP wave spectrum. The combined equations of motion for a vessel and a crane are derived using Kane’s equations of motion, where velocities and angular velocities are formulated in terms of twists, and the associated partial velocities and partial angular velocities are given as lines in Plücker coordinates. The unknown reaction forces are represented as wrenches and are determined using screw transformations. The method is used to study the effect of the roll and pitch compensation platform in numerical simulations. The efficiency of the platform is evaluated in terms of the magnitude of reaction forces and crane payload sway angles.

Proportional–integral-derivative controller with inlet derivative filter fine-tuning of a double-pendulum gantry crane system by a multi-objective genetic algorithm

ABSTRACTOverhead cranes are widely used in industry to move extremely heavy and bulky loads through the overhead space in a facility instead of through aisles or on the floor. Unfortunately, the natural sway of a crane's payload is a huge safety problem which needs more research by control engineers, as the sway of the payload affects both the safety and productivity of a factory. This article introduces an optimized mathematical model of a double-pendulum overhead crane with control schemes: scheme 1 uses three proportional -integral-derivative (PID) controllers with inlet derivative filters; scheme 2 uses one PID controller for accurate trolley positioning and two anti-swing proportional -derivative controllers to eliminate hooks and payload sway, all with inlet derivative filters. The controllers include up to nine gains which are tuned using the multi-objective non-dominated sorting genetic algorithm-II with five fitness functions and weighted function to choose a suitable solution from Pareto solutions.