Abstract
A continuous finite-time robust control method for the trajectory tracking control of a nonholonomic wheeled mobile robot (NWMR) is presented in this paper. The proposed approach is composed of conventional sliding-mode control (SMC) in the internal loop and modified switched second-order sliding-mode (S-SOSM) control in the external loop. Sliding-mode controller is equivalently represented as stabilization of the nominal system without uncertainties. An S-SOSM control algorithm is employed to counteract the impact of state-dependent unmodeled dynamics and time-varying external disturbances, and the unexpected chattering has been attenuated significantly. Particularly, state-space partitioning is constructed to obtain the bounds of uncertainty terms and accomplish different control objectives under different requirements. Simulation and experiment results are used to demonstrate the effectiveness and applicability of the proposed approach.
Highlights
In the past few decades, the design of a robust control of nonholonomic wheeled mobile robot (NWMR) has been a difficult task due to the nonlinearities, nonholonomic constraints, and uncertainties in the system [1]
Unlike most of the methods mentioned above, state-space partitioning [33, 34] is embedded into the switched second-order sliding-mode (SSOSM) controllers, such that the trajectories can be driven onto the desire trajectory in finite time and do not require the knowledge of the bounds of the uncertainties
Motivated by the idea [21, 33, 34], we further propose a combination of an integral sliding-mode controller and an SSOSM controller
Summary
In the past few decades, the design of a robust control of nonholonomic wheeled mobile robot (NWMR) has been a difficult task due to the nonlinearities, nonholonomic constraints, and uncertainties in the system [1]. Conventional sliding-mode controllers feature an obvious drawback where control torque is discontinuous and Complexity oscillates at a high frequency, which cannot be tolerated in some practical applications To avoid this phenomenon, some methods have been proposed, such as equivalent control, boundary layer method [22], and intelligent SMC [23]. Unlike most of the methods mentioned above, state-space partitioning [33, 34] is embedded into the switched second-order sliding-mode (SSOSM) controllers, such that the trajectories can be driven onto the desire trajectory in finite time and do not require the knowledge of the bounds of the uncertainties.
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