The present study suggests an enhanced coupling non-linear control approach for both cart positioning and load swing elimination control of underactuated bridge cranes. The significant feature of the ...proposed method is its superior control performance as well as its strong robustness over different/uncertain cable lengths that are the major factor influencing load swing. Owing to the underactuated nature, the load swing can merely be damped out by the cart motion. Inspired by this inherent mechanism and also motivated by the desire to achieve an improved control performance, we enhance the coupling behaviour between the cart movement and the load swing by introducing a new composite signal, and on this basis, propose a non-linear control law. Lyapunov-based mathematical analysis is implemented to support the theoretical derivations. To verify its control performance, both numerical simulation and hardware experiment results are included to illustrate that the proposed method can achieve superior control results and admit strong robustness with respect to different/uncertain cable lengths and external disturbances.
A bridge crane is a complicated nonlinear underactuated mechatronic system, for which high-speed positioning and anti-swing control is the kernel objective. Existing methods for varying cable length ...cranes require either linearizations or approximations, when performing analysis, and they usually assume small load swing; moreover, the ranges of the tracking errors cannot be guaranteed during the overall process. Motivated by these facts, we present a new tracking scheme for cranes with load horizontal transportation and lowering control, which achieves simultaneous load swing suppression and elimination. To the best of our knowledge, the proposed method yields the first feedback closed-loop control result not needing linearization or approximation operations to the original nonlinear crane dynamics with cable length variation, while relaxing the common assumption imposed on load swing associated with existing methods. It can also guarantee that the tracking errors are always within a priori set bounds and converge to zero rapidly. Lyapunov-like analysis is implemented to support the theoretical derivations. We carry out hardware experiments to illustrate the superior control performance of the new method.
Anti-swing control of bridge cranes has been widely studied to improve the efficiency of industrial transportation. However, in practice, the performance of bridge crane control methods is reduced by ...external disturbances and internal uncertainties. Therefore, an enhanced coupled nonlinear control strategy based on feedforward compensation has been proposed in this study. Appropriate composite signals were introduced to enhance the coupling between the system states and improve the transient performance of the controller. The design of the composite signal takes into account the characteristics of crane model. The unknown disturbance was then treated as a state variable, and the crane dynamic model was transformed accordingly. Finally, the state of the model was estimated by the extended state observer, and the disturbance estimate was compensated to improve the robustness of the control system. The stability of the controller was verified through a rigorous mathematical analysis. The simulation and experimental results verified the effectiveness of the proposed method.
In the assembly workshops of some heavy special equipment, the bridge cranes for payload lifting often needs to be located frequently. However, the locating position is often determined by the ...operator, which is random and results in significant payload oscillation and difficulties in trolley positioning. Furthermore, in practice, the bridge crane always exhibits more complicated double-pendulum dynamics compared with single-pendulum crane. To solve these problems, this paper establishes the double-pendulum model of bridge crane. Derived from the proportional-derivative (PD) control, the single closed-loop is designed based on the hook oscillation during acceleration and transporting; when locating, the double closed-loop is presented by utilizing the position and the hook oscillation. Combining the two control methods, a single and double closed-loop compound anti-sway control (SDCAC) method for the bridge crane is proposed. On this basis, to improve the performance of the SDCAC system, the sequential quadratic optimization (SQP) method is adopted to optimize PD parameters. Besides, a novel bumpless transfer control method is proposed to realize the smooth transition between the two control modes. Finally, the simulations and experiments are conducted. The results demonstrate the effectiveness of the proposed method.
Acceleration and deceleration in overhead cranes may induce undesirable load swinging, which is unsafe for the surrounding human operators. In this paper, it is shown that such oscillatory behavior ...depends on the length of the rope and thus a gain-scheduling control law is proposed to reduce such an effect. Specifically, to take into account the technological limits in the controller implementation, a fixed-order controller is tuned, by also enforcing robustness and performance constraints. The proposed strategy is experimentally tested on a real bridge crane and compared to a time-invariant solution.
A conventional quasi-static load method causes small stress amplitude and less stress change times when calculating the stress change of crane structures, leading to inaccurate prediction results of ...the structural fatigue life of the crane. Thus, by investigating the dynamic impact of the crane in the lifting process, the dynamic model of the lifting process was constructed in this study to explore the load variation of a crane structure. A fatigue life prediction method considering the lifting impact effect is proposed to analyze the fatigue life of structures. The calculation results indicate that the lifting impact process increases the number of stress cycles in structures, which has a negative impact on the structural fatigue life. Therefore, determining the dynamic response relationship between the lifting impact effect and the fatigue life of a crane structure can help improve the safety of this structure.
Operating a bridge crane under large amplitude cargo sways is problematic and dangerous from both an efficiency and a safety standpoint. The situation deteriorates further when the payload develops a ...double-pendulum (DP) effect. The dynamic behavior of bridge crane systems susceptible to the DP effect is studied in the context of persistent multiplicative disturbances in this paper. A modified sliding mode observer (SMO) with uncertainty compensation is proposed to predict the unavailable states of the system. Simple implementation, noise resiliency, bounded-time convergence, and the absence of complex or inaccessible coordinate transformation are the notable features of the proposed SMO. A composite SMO-based modified super-twisting control technique is designed to achieve the goal of rapid and precise trolley placement and speedy cargo swing suppression. It has been proved that the suggested hybrid control method maintains the system's asymptotic stability by using a strict quadratic Lyapunov function. The proposed control system's efficacy has been demonstrated via rigorous simulation experiments.
For the control problem of bridge cranes, it is challenging to realize fast transportation and efficient swing suppression simultaneously. Motivated by this observation, in this paper, we aim to ...propose a nonlinear controller achieving these objectives by constructing a desired Lyapunov function. In particular, a constructive Lyapunov function is introduced in a segmented manner. Based on that, a nonlinear control method rendering the dissipation inequality with respect to the constructed Lyapunov function is proposed straightforwardly, which achieves precise trolley positioning along with efficient payload swing elimination. The corresponding stability and convergence analysis is guaranteed by Lyapunov techniques and LaSalle’s invariance principle. Simulation and experimental results are provided to demonstrate the effectiveness and feasibility of the proposed method.
