Marco A. Arteaga–Pérez

3D Visual Servoing Control for Robot Manipulators Without Parametric Identification

Visual servoing control of robot manipulators represents a natural option in unstructured environments and it is specially attractive when the task to achieve can be expressed directly in image coordinates. In the present work a control law is developed for trajectory tracking of three degrees of freedom robot manipulators. The main characteristic of the proposed algorithm is that it does not need any dynamic model of the system and image coordinates are employed directly for feedback, while an observer is designed for velocity estimation. To carry out 3D movements no stereoscopic vision is used. Rather, a simpler configuration employing two fixed cameras is proposed which makes unnecessary their calibration and helps avoid occlusions for most of the robots workspace. The developed theory was successfully tested in an industrial manipulator.

Observer design for the synchronization of bilateral delayed teleoperators

Abstract Bilateral teleoperators are widely used in several applications such as surgical robots and underwater vehicles. However, due to the long distance between the local and remote manipulators, time delay arises over the communication channel, so that neither exact tracking position nor perfect transparency can be achieved. In free movement, most control approaches are meant to guarantee consensus or to synchronize the local and the remote robots by inducing periodic position trajectories. In constrained motion, the human operator can only have some telepresence feeling but not perfect transparency. Furthermore, most algorithms are designed assuming that joint velocities are available, while sometimes this is not the case and it is desirable to estimate joint velocities through an observer. In this work, a novel teleoperation controller–observer scheme is introduced that does not make use of velocity measurements and, more importantly, does not require the exact knowledge of the dynamical model. This scheme has the following properties: (a) in free motion and without a human operator, the local and the remote manipulators tend either to a periodic trajectory or to a particular position, thus achieving either synchronization or position consensus; (b) when a human operator moves the local robot, the remote manipulator tracks the commanded position with the corresponding delay; (c) in constrained motion, the human operator has some feeling of telepresence. Experimental results are provided to validate the proposed algorithm.