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• A dynamic model of an underwater soft-link manipulator with vortex flows is derived. • Dynamic interaction between the soft-body structure and water flow is described. • A non-smooth piecewise smoother is presented to reduce coupled vibrations. • Experimental validation is provided for dynamic model and control method. While significant work has been directed at dynamics and control of underwater soft-body manipulators, less success has been achieved with interaction between soft structures and fluid flow. The complicated behavior of the interaction may corrupt operational efficiency and safety of underwater manipulators. The equations of the motion of underwater soft-link manipulators are reported in this article. The interaction among the water flow, the lateral vibrations and vortex-induced vibrations of the soft link has been described thoroughly in the analytical model. Furthermore, a novel control method is proposed to suppress coupled vibrations induced by the interaction. Comparing with previous control methods, the proposed method can provide more robustness to variations in the design frequency. Numerous experimental data obtained from a soft-body link implanted in water validated the behavior of the dynamic model and the effectiveness of the vibration-control method. The theoretical findings may also be acceptable for other types of soft-body structures immersed in the fluid. [ABSTRACT FROM AUTHOR]

Highlights • Model of dual planar cranes carrying a distributed-mass beam is derived. • A new method is developed for estimating the natural frequency of dual planar cranes. • MEI input shaper is presented for limiting oscillations of dual cranes. • Experiments validate dynamic behaviour and the effectiveness of MEI shaper. Abstract Unwanted oscillations caused by the operator-commanded motions lower the capable operating speeds and degrade the safety of dual cranes moving distributed-mass payloads. Mounting numbers of works have been devoted to the dynamics and control of dual cranes. However, few studies have been dedicated to the accurate estimation of natural frequency, which is a critical factor for controlling the dual cranes. This paper develops a new method to predict the natural frequency of dual planar cranes with different cable lengths. Furthermore, a modified extra-insensitive (MEI) input shaper is proposed to suppress the oscillations of the payload swing and pitch in the dual cranes. The MEI shaper has good robustness to large changes in the frequency, and has good performance in the jerk limitation. Simulated and experimental investigations are performed on small-scale dual cranes transporting a slender beam to validate the system dynamic behavior and the effectiveness of the MEI shaper. [ABSTRACT FROM AUTHOR]

Highlights • A new dynamic model is developed for a flexible single-link manipulator. • The model includes an infinite number of uncoupled Duffing oscillators. • Two methods are presented for controlling the vibrations of Duffing oscillators. • Experiments validate Duffing model and the effectiveness of control methods. Abstract Unwanted vibrations caused by the commanded motions lower the positioning accuracy and degrade the control performance of flexible link manipulators. Much work has been devoted to the dynamics and control of flexible link manipulators. However, there are few studies dedicated to the flexible link manipulators having Duffing oscillator dynamics. This paper develops a new model for a flexible single-link manipulator by assuming large mechanical impedance in the drives or large inertia of the motor hub and by considering the flexibility of the single-link manipulator. The derived model includes an infinite number of uncoupled Duffing oscillators by ignoring the modal coupling effects. Two new methods are presented for controlling the vibrations of the flexible manipulator governed by Duffing oscillators. One is designed for the single-mode Duffing oscillator, and the other is for the multi-mode Duffing oscillators. A comparison of these two methods is made using the results of numerical simulations and experimental measurements. Experimental investigations are also performed on a flexible single-link manipulator to validate the dynamic behavior of Duffing oscillators and the effectiveness of the new control methods. [ABSTRACT FROM AUTHOR]

• Planar dynamic model of an underwater soft-link manipulator is derived. • Equations for estimating frequency and mode shape are proposed. • A control method is presented to control coupled vibrations. • Experiments validate effectiveness of dynamic model and control method. Underwater soft-link manipulators can be applied in offshore and marine industries. However, the soft-body link may interact with the fluid flow in this type of coupled liquid-link system. Both frequencies and mode shapes of the coupled system differ from those of uncoupled link vibrations and water flow due to the liquid-link interaction. Therefore, the dynamic model of underwater soft-body manipulators that account for liquid-link interaction is required to comprehend and control. Although significant work has been focused on the underwater manipulator and the soft manipulator, no significant dynamic modeling, control study, and experimental validation have been directed at the liquid-link interaction in underwater soft-body manipulators. A dynamic model of underwater soft-link manipulators undergoing planar motions is presented in this article. The analyses of frequencies and mode shapes for the liquid-link interaction are also described. Meanwhile, a control method is designed to mitigate coupled vibrations in underwater soft-link manipulators. Simulated and experimental results validate the utility of the dynamic model and control method. [ABSTRACT FROM AUTHOR]

Operating cranes is challenging because payloads experience large and dangerous oscillations, especially when the system is suffering from wind disturbances and the large-size payload is modeled as a distributed-mass model. The payload oscillations induced by both intentional motions commanded by the human operator and by the external wind disturbances make the dynamics more complicated. This paper presents a novel combined control architecture to limit oscillations of the distributed-mass payload caused by both human-operator commands and wind disturbances. While a smoothed command suppressed operator-induced oscillations, a wind-rejection command eliminated the payload swing resulting from the wind gusts. Through simulations, a large range of system parameters and motions are analyzed to investigate the dynamic behavior of bridge cranes with distributed-mass beams and wind disturbances by using the new control scheme. Experimental results obtained from a small-scale bridge crane validate the simulated dynamic behavior and the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Motion-induced oscillations of crane payloads seriously degrade their effectiveness and safety. Significant progress has been achieved with reducing payload oscillations on a single-pendulum crane with a point-mass payload attached to the end of the cable. However, large payloads and the actual configuration of the hoisting mechanism may transform the crane to a double-pendulum system with a distributed-mass payload. The manipulation task can be more challenging because of the complicated dynamics. The dynamics of bridge cranes transporting distributed-mass beams are derived. A command-smoothing scheme is presented to suppress the complex payload oscillations. Simulations of a large range of motions are used to analyze the dynamic behavior of the cranes and the robustness of the method. Experimental results obtained from a small-scale double-pendulum bridge crane transporting a distributed-mass beam validate the simulated dynamic behavior and the effectiveness of the method. [ABSTRACT FROM AUTHOR]

• Model of tower cranes carrying slender payloads is derived. • Equation for estimating the twisting frequency is presented. • A discontinuous piecewise smoother is proposed for controlling swing and twisting. • Experiments validate dynamic behaviour and the control effectiveness. 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. [ABSTRACT FROM AUTHOR]