Model-Free Visually Servoed Deformation Control of Elastic Objects by Robot Manipulators

A dynamic and uncalibrated method to visually servo-control elastic deformations by fully-constrained robotic grippers

“…In our early study [14], we noted that n = 3 has a restricted number of reachable configurations (singularities tend to arise in this situation). In contrast with our previous estimator [15], the stability (convergence) of our new online algorithm can be proved with Lyapunovlike theory; we must remark that this method requires slow motion of the manipulator and proper filtering of the visually measured flow signals.…”

“…3 shows the 6-DOF (n = 6) robot manipulator that we use to conduct the experimental study. This mechanical system has an open architecture servo-controller that allows to set the joint velocity in real-time (see [15] for details). The manipulator's gripper rigidly grasps a 2 × 12 × 25 mm soft foam sheet; we place artificial markers on the surface of this object.…”

“…The coordinates of this smooth function can represent, e.g. visual displacements, angles, curvatures, line features, etcetera (see [15]). By time-differentiating this function we obtaiṅ…”

“…To the best of our knowledge, this paper reports for the first time the simultaneous control of 4 independent deformation DOF by a single manipulator. In [15], we also report the control of 4-DOF, but jointly performed by two manipulators. The control of deformation via rotations results instrumental to our method.…”

“…By incorporating the gripper's attitude and several visual measurements, our method can independently control elastic deformations with the 6-DOF motion of the manipulator-something we can not achieve with existing controllers including our previous formulations [14], [15]. The uncalibrated method that we present does not require identification of the deformation and camera models.…”