The analytical models of a wheeled mobile robot (WMR) are often derived based on the assumption that the surface on which it manoeuvres is free from any irregularities. However, the wheels of a WMR are likely to encounter small but unavoidable obstacles. The interaction between stationary obstacles and the wheels of the mobile robot can adversely affect the stability of the payload as well as the robot's handling control. The limited understanding of the mechanism of wheelobstacle interaction and its implication on the overall dynamics of a WMR has hindered the development of control tools that may be used to limit the adverse effects of traversing surface irregularities. In this paper, vectorial mechanics approach is used to model the dynamics of wheeled mobile robots (WMRs) travelling over localised surface irregularities. This model is employed in conjunction with temporal trajectory functions to compute the traction force requirements of WMRs traversing obstacles of specified profiles. The obstacles are in the form of sinusoidal humps which are decomposed into positive and negative sinusoidal ramps. It is shown that a compromise can be obtained between the minimum times requirement for obstacle traversing, the traction force requirements, and the geometrical properties of the obstacles. The traction force can become negative which implies the need to switch to a braking action. This switch between the traction mode and braking mode of the actuators can be prevented if an optimal time for the obstacle traversing is selected a-priori. It is also shown that the relationship between the traction or breaking force magnitude and the manoeuvre time is non-linear and that the traction force requirements are much greater at small manoeuvre times than at big manoeuvre times. In addition, it is shown that the grade of an obstacle, which depend on its length and height, affect the traction requirements.
Predicting the traction force requirements of wheeled mobile robots traversing obstacles
2008
10 Seiten, 10 Quellen
Aufsatz (Konferenz)
Englisch
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