Abstract
A wide application of sliding mode variable structure control as a nonlinear robust control method, has been witnessed in anti-swing positioning control of bridge crane system. Aiming at the problem that the sliding mode variable structure control system of bridge crane is not robust in approaching process, a new Global-Equivalent Sliding Mode Controller (GESMC) based on bridge crane system is proposed. This controller can realize the anti-sway positioning control of the bridge crane system under the condition of uncertain model parameters and external disturbance. The proposed controller, different from the traditional sliding mode control, excels in improving system robustness through keeping the system states in the sliding surface during the whole response process. Specifically, it initiates with the design of a global sliding surface, which can eliminate the sliding mode approach process of the system and achieve global robustness in the system. Afterwards, a new switching function combined with the equivalent sliding mode control method is incorporated to effectively reduce the chattering generated when the system reaches the sliding mode manifold. Its asymptotic stability is proven without a priori knowledge on the bounds of unknown disturbances by using the Lyapunov stability theory. Lastly, the simulation conducted verifies the effectiveness and robustness of the GESMC proposed in this paper and meanwhile demonstrates a comparatively favorable performance for the GESMC in reducing chattering.
Highlights
Bridge-type cranes act an indispensable role in modern logistics such as ports, warehouses, construction sites and so on
Sliding mode variable structure control is a nonlinear closed-loop control method with strong robustness, which has been extensively used in bridge crane systems in recent years, such as Conventional Sliding Mode Control (CSMC) [10],[11], Hierarchical Sliding Mode Control (HSMC)[12,13,14], Terminal Sliding Mode Control[15,16,17], decoupled Sliding Mode Control[18],[19], adaptive Sliding
This paper intends to design a controller with the following equation (8) by dividing both sides of Formula global robustness which is applicable to the nonlinear system, (2) by ml: so that the bridge crane system can reduce the value of swing angle θ as much as possible while ensuring the rapid reach of x and l at the target values
Summary
Bridge-type cranes act an indispensable role in modern logistics such as ports, warehouses, construction sites and so on. The proposed controller can effectively shorten the approach time of the system states to the sliding mode surface by designing the nonlinear time-varying sliding mode surface, it still cannot solve the defect of weak anti-disturbance ability in the approach process of the system. It can only ensure the local robust control of the system during the control process. A new sliding mode controller with global convergence effect is introduced for two-dimensional bridge crane to overcome the local robustness defect of traditional sliding mode controller.
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