Machine vision system errors for unmanned aerial vehicle navigation

The use of laser scanners as machine vision systems in Unmanned Aerial Vehicle (UAV) navigation offers a wide range of advantages, when compared with camera-based systems. As one advantage, the measurement of real physical distances can be mentioned, which results in a reduction of measurement times and thereby fast image processing of the UAV surrounding medium. In previous work, a novel laser scanner namely Technical Vision System (TVS) was presented, which implements a continuous laser scan for determination of 3D coordinates of any object under observation. Also previous work has shown the advantage, when using high-quality instead of low-quality DC motors as actuators for positioning the laser ray in the TVS field-of-view. However, the static friction in the ball bearings of the motor shaft leads to a residual error not zero for the angular error in steady state. Present paper introduces a new approach of estimating this residual error by use of a friction model. Thereby, the friction model is described and used for simulation of the residual angular error when controlling the DC motor in open-loop configuration and validated by experimentation results.