Adaptive motion control of wheeled mobile robot with unknown slippage

Abstract

As a major representative nonholonomic system, wheeled mobile robot (WMR) is often used to travel across off-road environments that could be unstructured environments. Slippage often occurs when WMR moves in slopes or uneven terrain, and the slippage generates large accumulated position errors in the vehicle, compared with conventional wheeled mobile robots. An estimation of the wheel slip ratio is essential to improve the accuracy of locomotion control. In this paper, we propose an improved adaptive controller to allow WMR to track the desired trajectory under unknown longitudinal slip, where the stabilisation of the closed-loop tracking system is guaranteed by the Lyapunov theory. All system states use neural network online weight tuning algorithms, which ensure small tracking errors and no loss of stability in robot motion with bounded input signals. We demonstrate superior tracking results using the proposed control method in various Matlab simulations.

Neural network-based adaptive tracking control for a nonholonomic wheeled mobile robot with unknown wheel slips, model uncertainties, and unknown bounded disturbances

“…• In addition, the work in [5] employed slip ratios that heavily depended on a gyro-sensor and odometry for designing the kinematic control law, whereas our work did not.…”

“…• In this work, we have proposed one adaptive tracking controller based on the sliding mode control technique with only one control closed loop, whereas the work in [5] utilized backstepping techniques (backstepping from kinematics into dynamics) with two control closed loops where the outer one is the kinematic control closed loop and the inner one is the dynamic control closed loop.…”

“…• Furthermore, the work in [5] only dealt with longitudinal slips of each driving wheel, but the lateral slip was not considered, while our proposed controller has managed to compensate both longitudinal and lateral slips.…”

“…Particularly, with the purpose of compensating the undesired effect of wheel slips, an adaptive tracking * Correspondence: nvtinh@ioit.ac.vn controller was derived through a radial basis function neural network [5]. However, this work only dealt with longitudinal slips of each driving wheel; lateral slip was not considered.…”

Neural Network-based Adaptive Sliding Mode Control Method for Tracking of a Nonholonomic Wheeled Mobile Robot with Unknown Wheel Slips, Model Uncertainties, and Unknown Bounded External Disturbances

“…In particular, an adaptive tracking control method by means of neural networks was proposed in [6] in order to overcome the harmful effect of the wheel slips. By employing gyro-sensors and encoders, the slip ratios were calculated in [7], [8].…”