Design and Analysis of a Tendon-driven Snake-arm Robot Based on Spherical Magnet

The tendon-driven snake-arm robot can achieve multiple degrees of freedom (DOF) bending motion with a compact structure, which enables the robot to be widely applied in confined environments. However, if a conventional tendon-driven snake-arm robot is subject to a lateral force on the distal end, it will experience passive compliance. In this paper, a 2-DOF rolling joint is proposed based on the opposite-pole attraction of spherical magnets, which has a relatively simple structure than traditional joints. By serial connecting the 2-DOF rolling joints, a novel snake-arm robot is designed utilizing a tendon-driven approach. The kinematic model and workspace of the snake-arm robot are obtained, and the bending motion is validated. Based on the kinematic model, it is theoretically proved that the proposed robot can avoid passive compliance. In addition, this feature is verified through load experiments on the developed prototype.

Passive Air Leakage Detection Mechanism for a Vacuum Suction Actuator

Recently, research on vacuum actuators for holding and transporting objects has been actively conducted. In particular, many vacuum actuators are used to hold and transport several objects at once. However, there is a possibility that a problem of reducing vacuum efficiency may occur when several vacuum actuators are used simultaneously in the process of transporting multiple objects. The first factor is that, due to the diversity of the object’s shape, the vacuum pad of some actuators may not touch the object, so that gripping may not occur. Second, some actuators’ vacuum pad touches the object, but the pad is not completely blocked, resulting in air leakage. This paper used a spring mechanism to solve this problem and developed a vacuum gripping actuator that can block airflow into the actuator that is not used for vacuum efficiency when driving the system before the system is driven. Due to the spring inside the actuator that can play the role of passive compliance, the length can be adjusted, so even if the distance to the object is not constant, it can hold and transport several objects. Furthermore, the pretension of the spring makes it possible to block air inflow initially. We have also developed a brake system using pneumatic and tendon to hold the actuators to maintain each actuator’s length when holding and moving objects. We unified the driving method for operating both systems for simplicity by receiving pneumatic pressure from a pneumatic compressor.

Learning Optimal Fin-Ray Finger Design for Soft Grasping

The development of soft hands is an important progress to empower robotic grasping with passive compliance while greatly decreasing the complexity of control. Despite the advances during the past decades, it is still not clear how to design optimal hands or fingers given the task requirements. In this paper, we propose a framework to learn the optimal design parameter for a fin-ray finger in order to achieve stable grasping. First, the pseudo-kinematics of the soft finger is learned in simulation. Second, the task constraints are encoded as a combination of desired grasping force and the empirical grasping quality function in terms of winding number. Finally, the effectiveness of the proposed approach is validated with experiments in simulation and using real-world examples as well.