Abstract-In this paper the problem of contmlling the motion of a nonholonomic vehicle along a decired trajectory using observations from an overhead camera is considered. The control problem is formulated in the image plane. We show that the system in the image plane is differentially Rat and use this property to generate effective control strategies using only visual feedback. Simulation results illustrate the methodology and show robustness to errors in the camera calibration parameters. Visual servoing, i.e. the use of feedback from a camera or a network of cameras, has been used increasingly in the last few years for the development of control algorithms such as motion control for mobile robots [7], robot manipulation tasks [Ill and remote surveillance tasks [131. an overhead camera that may be mounted on a UAV. We exploit the well-known property of dierential &mess for nonholonomic car-like robots [lo]. Roughly speaking, any system is differentially flat if one can find a set of outputs (which is equal in number to the set of inputs) such that all the states of the system and all the inputs for the system can be expressed in terms of these outputs and their higher derivatives. In other words, all the states and inputs of the system can be expressed in terms of the flat outputs without integration. In our system, the inputs are the usual angular and linear velocities for the robot but the feedback is provided via the positions of a reference point on the car seen in the image of an overhead camera. We show that the system is differentially flat with the flat outputs being the image coordinates of the reference point. We show tbat the visual-servoing problem can be easily solved using this framework and provide simulation results to illustrate our methodology. We briefly describe the visual servoing problem and the paradigm of differential flatness in Section U. We establish in Section III that the system dynamics, when transferred to the image plane, possesses the property of differential flatness. Thus, a controller can be designed in the flat space using methods from linear systems theory and then mapped back into the real world. These ideas are demonstrated in Section IV. Some results from simulation both for systems with and without parametric uncertainties are presented in Section V. Finally, Section VI discusses the advantages and limitations of our approach and our
We have presented the background and the problem formulation in the image space REF with some preliminary results in simulation.
Visual servoing of a UGV from a UAV using differential flatness
Proceedings 2003 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2003) (Cat. No.03CH37453)
Proceedings 2003 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2003) (Cat. No.03CH37453)
Computer Science