Using a Low-Cost Onboard Camera for Sliding Mode Control of a Mobile Robot in Slippery Environments

Robot motion on sliding mode This paper reports on a simple sliding mode controller that is based on a low-cost camera and being developed for application to a compact, mobile snow-removal robot. We adopt a sliding mode controller for the lightweight, tracked robot to be used under slippery conditions. Assuming the snow-removal task can be carried out by following straight paths, this paper focuses on the path control problem by using a low-cost camera and a simple marker placed on the work site. The transient motion control during the converging state to the line paths is discussed in particular. In our snow-removal application, robustness against disturbances due to snow pressure or track slips is important. In addition, rotation should not be excessive during the transient response so that the robot does not lose sight of the marker. The sliding mode controller is a useful solution, filling these requirements. The problem of robustness in the face of track slip is analyzed theoretically, based on a model with parameter error and input disturbance. The expected tracking accuracy is evaluated in terms of the disturbance values and feedback gains. Experiments are carried out on a slippery surface of polystyrene beads. Robustness against disturbance is tested on an inclined surface.