Visual Servo-Collision Avoidance Hybrid Task by Considering Detection and Localization of Contact for a Soft Manipulator

Due to the features of soft material, such as softness, deformability, and adaptability to constrained surroundings, soft manipulators can collide with external objects to some extent. To take the best advantage of this merit, this article presents a method of visual servo considering collisions with obstacles for a soft manipulator. First of all, a collision detection algorithm is proposed using shape feedbacks obtained by a sensor network, on the basis of the assumption that the manipulator can be considered as a combination of a static segment and a dynamic segment. Then, a contact localization algorithm is proposed to pinpoint the position where the collision occurs by minimizing the differences between the theoretical and actual shapes. An obstacle get-away algorithm, which is achieved by driving the calculated contact point to a desired position, is presented to avoid the obstacle. Along with the visual servo, a controller taking the obstacle avoidance into account is proposed to perform the hybrid task, with its stability validated via Lyaponov criterion. Finally, simulations and physical experiments are carried out to evaluate the algorithms. It is shown that the pixel error can converge to zero and the distance from the obstacle with respect to the contact point increases obviously in a short time.