Abstract
Wheeled mobile robots (WMRs) in real complex environments such as on extraterrestrial planets are confronted with uncertain external disturbances and strong coupling of wheel-ground interactions while tracking commanded trajectories. Methods based on sliding mode control (SMC) are popular approaches for these situations. Traditional SMC has some potential problems, such as slow convergence, poor robustness, and excessive output chattering. In this paper, a kinematic-based feed-forward control model is designed for WMRs with longitudinal slippage and applied to the closed-loop control system for active compensation of time-varying slip rates. And a new adaptive SMC method is proposed to guide a WMR in trajectory tracking missions based on the kinematic model of a general WMR. This method combines the adaptive control method and a fast double-power reaching law with the SMC method. A complete control loop with active slip compensation and adaptive SMC is thus established. Simulation results show that the proposed method can greatly suppress chattering and improve the robustness of trajectory tracking. The feasibility of the proposed method in the real world is demonstrated by experiments with a skid-steered WMR on the loose-soil terrain.
Highlights
Wheeled mobile robots (WMRs) have been widely utilized for exploration tasks on both earth and extraterrestrial bodies
We focus on the common trajectory tracking problem and propose a new adaptive sliding mode control (SMC) method with a fast double-power reaching rate
To demonstrate the improvement to the performance of trajectory tracking by implementing the active slip compensation and the adaptive SMC, we performed a series of experiments with a WMR on loose soil
Summary
Wheeled mobile robots (WMRs) have been widely utilized for exploration tasks on both earth and extraterrestrial bodies. Kinematic models are relatively concise and easy to establish They are often utilized with different control laws [6, 7] for real-time applications. Wang et al [14] proposed an adaptive second-order SMC approach for the trajectory tracking of a skid-steered WMR to overcome external disturbances and parametric uncertainty. These methods have demonstrated that adaptive methods can improve the robustness of the control systems. We focus on the common trajectory tracking problem and propose a new adaptive SMC method with a fast double-power reaching rate.
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