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2 International Journal of Applied Mechanics and Engineering

2 2004

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Recursive backstepping stabilization of a wheeled mobile robot

Mnif F., Al-Yahmadi A. S.

International Journal of Applied Mechanics and Engineering

2004

Vol. 9, no 4

725-738

This research is aimed at the development of a dynamic control to enhance the performance of the existing dynamic controllers for mobile robots. System dynamics of the car-like robot with nonholonomic constraints is employed. A backstepping approach for the design of discontinuous state feedback controller is used for the design of the controller. It is shown that the origin of the closed loop system can be made stable in the sense of Lyapunov. The control design is made on the basis of a suitable Lyapunov function candidate. The effectiveness of the proposed approach is tested through simulation on a car-like vehicle mobile robot.

A wear model for rough surfaces based on the ultimate-stress asperity concept

Abdo J. A., Al-Yahmadi A. S.

International Journal of Applied Mechanics and Engineering

2004

Vol. 9, no spec.

11-19

This work presents the extension of the elastic-plastic contact model to provide theoretical means of estimating the wear due to the mechanical interaction of rough surfaces. In this regard the ultimate-stress asperity concept is introduced. The introduction of ultimate-stress asperity concept leads to the theoretical treatment of wear due to mechanical interaction of asperities. The ultimate-stress asperity concept is introduced to define the level of interference beyond which failure is expected. Two mathematical formulations are presented to provide theoretical estimates of the wear volume. In the first approach it is assumed that a portion of the interference volume is separated from the asperity while in the second approach the entire asperity peak above a certain plane parallel to the mean plane is assumed to be separated from the asperity. Inclusions of the material wear in the calculations of normal and tangential contact forces indicates that elastic and plastic effects play nearly equal roles. It is shown that the wear volume increases by increasing the normal and tangential loads.