Hybrid System Analysis and Control of a Soft Robotic Gripper with Embedded Proprioceptive Sensing for Enhanced Gripping Performance

Compared with conventional robots made of motors, rotational joints, and rigid linkages, soft robots are composed of compliant materials and structures. A remarkable feature of soft robots is that they can deform both actively and passively to conform to various shapes of objects to be gripped. From the kinematic point of view, soft robots can generate complex motions with high degrees of freedom (DoFs) at a small cost (in terms of the number of actuators or control inputs) by utilizing their inherent property of compliance. Considering the necessity of interactions between robots and environments, this feature is highly advantageous as robots can easily change their physical configurations depending on the surroundings and situations whether intentionally or unintentionally. Furthermore, the structural compliance allows for interactions with the environments in a passive and adaptive manner so that the safety for both the robots and the surroundings including humans can be guaranteed, which encouraged researchers to incorporate compliant mechanisms into various applications. Object manipulation is one of the most widely explored areas, and the first step of manipulation is to grip an object. To successfully grip the target object in this case, the robotic system has to adapt its shape to the object only with a limited number of active DoFs (i.e., actuators). There has been an approach to address this problem using under-actuated robotic hands that can easily conform various objects with different shapes. In this case, most studies have focused on analyzing the static models of robots to figure out the generated forces and the geometries for determining the best design parameters for given tasks. A mechanically programmable design with mechanical selectors incorporated in an under-actuated robotic hand has also been proposed to extend the grasping capabilities. However, the rigid link-joint structure inevitably constrains the motion of the robots and limits the reachable target regions in these approaches. Some researchers have partially adopted elastic elements into the structure to address the above limitation, in which the physical constraints can be averaged out at the desired configuration. However, soft robotic hands that are fully (or mostly) composed of elastic materials have a much higher capability of handling various objects, thanks to their unconstrained deformation with an infinite number of DoFs. Although various types of soft robotic hands or fingers have been developed, an analysis on the extended grasping capability has not been investigated enough yet. The difficulty comes from the complex configuration M. Park, B. Jeong, Prof. Y.-L. Park Department of Mechanical Engineering Institute of Advanced Machines and Design (IAMD) Seoul National University 1 Gwanak-ro, Gwanak-Gu, Seoul, Republic of Korea E-mail: ylpark@snu.ac.kr M. Park, B. Jeong, Prof. Y.-L. Park Institute of Engineering Research Seoul National University 1 Gwanak-ro, Gwanak-gu, Seoul, Republic of Korea