Vision-based control of a flying robot without linear velocity measurements

In this paper, image-based visual servo (IBVS) control of the quadrotor unmanned aerial vehicle (UAV) is considered. The main purpose of this paper is to use flow of image features as the velocity cue to compensate the low quality of linear velocity information obtained from accelerometers. Image features are selected from a combination of suitable perspective image moments without requiring geometric model of the observed target. Using respectively a linear and a nonlinear observer, two output feedback controllers are proposed. The main advantage of these approaches is that they are robust with respect to unknown depth information of the image. Stability analyses show that the states of the system are bounded and the error signals converge to zero during the positioning task. Simulation results are presented to illustrate the effectiveness of the proposed approaches.