Technical report on Optimization-Based Bearing-Only Visual Homing with Applications to a 2-D Unicycle Model

We consider the problem of bearing-based visual homing: Given a mobile robot which can measure bearing directions with respect to known landmarks, the goal is to guide the robot toward a desired "home" location. We propose a control law based on the gradient field of a Lyapunov function, and give sufficient conditions for global convergence. We show that the well-known Average Landmark Vector method (for which no convergence proof was known) can be obtained as a particular case of our framework. We then derive a sliding mode control law for a unicycle model which follows this gradient field. Both controllers do not depend on range information. Finally, we also show how our framework can be used to characterize the sensitivity of a home location with respect to noise in the specified bearings. This is an extended version of the conference paper [1].Comment: This is an extender version of R. Tron and K. Daniilidis, "An optimization approach to bearing-only visual homing with applications to a 2-D unicycle model," in IEEE International Conference on Robotics and Automation, 2014, containing additional proof

Preliminary variation on multiview geometry for vision-guided laser surgery.

International audienceThis paper proposes to use the multiview geometry to control an orientable laser beam for surgery. Two methods are proposed based on the analogy between a scanning laser beam and a camera: the first method uses one camera and the laser scanner as a virtual camera to form a virtual stereoscopic system while the second method uses two cameras to form a virtual trifocal system. Using the associated epipolar or trifocal geometry, two control laws are derived without any matrix inversion nor estimation of the 3D scene. It is shown that the more geometry is used, the simpler the control gets. These control laws show, as expected, exponential convergence in simulation validation

Weakly Calibrated Stereoscopic Visual Servoing for Laser Steering: Application to Phonomicrosurgery.

International audienceThis paper deals with the study of a weakly calibrated multiview visual servoing control law for microrobotic laser phonomicrosurgery of the vocal folds. It consists of the development of an endoluminal surgery system for laserablation and resection of cancerous tissues. More specifically, this paper focuses on the part concerning the control of the laser spot displacement during surgical interventions. To perform this, a visual control law based on trifocal geometry is designed using two cameras and a laser source (virtual camera). The method is validated on a realistic testbench and the straight point-to-point trajectories are demonstrated

Stereo vision-based algorithm for control of nonholonomic mobile robot

Requirements for an effective and reliable material transport system within advanced manufacturing environment can be fulfilled by using intelligent mobile robots to perform material handling and transportation tasks. In order to re-duce the degree of ambiguity occurring in a dynamic manufacturing environment, mobile robots are equipped with a stereo vision system that can reliably estimate distance to manufacturing entities. In this paper, a new stereo vision-based algorithm for control of nonholonomic mobile robot is proposed. The main control algorithm, based on an error in image parameters (IBVS - Image based visual servoing), is used for positioning of a mobile robot in the de-sired location. For estimation of the error in image parameters, point features are extracted from the current and target camera view via feature detection and description algorithm. A comparison of these algorithms is made on a set of images obtained in laboratory model of the manufacturing environment by using Basler acA1920-25uc cameras. Based on the results of comparison, KAZE feature detection and description algorithm is proven to be best suited for this specific case. In order to verify the stereo visual control system, simulation and real-world experiments are per-formed. Two experiments are conducted on a mobile robot RAICO (Robot with Artificial Intelligence based COgni-tion) in a laboratory model of the manufacturing environment. Experimental results show the effectiveness of the pro-posed stereo visual control system and its applicability in reaching the desired location with minimal accuracy error

Robust control for a wheeled mobile robot to track a predefined trajectory in the presence of unknown wheel slips

In this paper, a robust controller for a nonholonomic wheeled mobile robot (WMR) is proposed for tracking a predefined trajectory in the presence of unknown wheel slips, bounded external disturbances, and model uncertainties. The whole control system consists of two closed loops. Specifically, the outer one is employed to control the kinematics, and the inner one is used to control the dynamics. The output of kinematic controller is adopted as the input of the inner (dynamic) closed loop. Furthermore, two robust techniques were utilized to assure the robustness. In particular, one is used in the kinematic controller to compensate the harmful effects of the unknown wheel slips, and the other is used in the dynamic controller to overcome the model uncertainties and bounded external disturbances. Thanks to this proposed controller, a desired tracking performance in which tracking errors converge asymptotically to zero is obtained. According to Lyapunov theory and LaSalle extension, the desired tracking performance is guaranteed to be achieved. The results of computer simulation have shown the validity and efficiency of the proposed controller