A 2D unknown contour recovery method immune to system non-linear effects

Abstract

A method to recover general 2D a priori unknown contours using a kind of special optic sensor is described. Contour recovery is an important task for exploratory operations in unknown environments as well as for more practical applications such as grinding or deburring. It is not an easy task since the recovered contour (generally obtained using encoder data) is severely distorted due to errors in the kinematic model of the robot and to the non-linearities of its actuators. Some mathematical models have been presented to partially compensate for those effects, but they require a deep knowledge of both the robot and sensor models which are difficult to obtain accurately, and normally imply an adaptive non-linear control to estimate some of the unknown parameters of the model. Our approach, in despite of its simplicity, is intrinsically immune to non-linearities, which allows us to eliminate most of the distortions added to the sensor data. A simple algorithm to follow unknown planar contours is presented and used to test the performance of this approach in comparison to the one using encoder data. Experimental results and practical problems are also discussed.