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Similar to the end effectors for traditional rigid robots, those for soft robots are essential as the interacting media between the robots and their environments. Inspired by the forelegs of climbing animals, a passively adaptive soft gripper (ASG), with six claws and a compliant mechanism, is developed for grasping objects and attaching to rough surfaces. The design method, grasp adaptability, form closure, and force equilibrium of the ASG are presented and analyzed in this paper. Due to the compliance at each claw root, the ASG possesses a high passive adaption to various objects. With sharp hooks, a form closure may be achieved easily when the ASG grasps rough objects with structured or unstructured shapes. The ASG grasping an object constitutes an under-actuated system, the solution to which is difficult to obtain. The Monte Carlo method is suggested to achieve effective solutions for such systems, and the in-hull rate is proposed to evaluate the difficulty of finding solution. Tests and experiments with the ASG grasping various objects have verified the adaptability and reliability of the ASG. The analytic and experimental results show that the novel ASG may be used as a universal gripper for soft manipulators and a prospective attaching device for biped climbing soft robots.

A variety of soft robots with prospective applications has been developed in recent years. As a key component of a soft robot, the soft actuator plays a critical role and hence must be designed carefully according to application requirements. The soft body may deform in undesired directions if no restraint is endued, due to the isotropy of the pure soft material. For some soft robots such as an inchworm-like biped climbing robot, the actuation direction must be constrained with the appropriate structure design of the soft actuator. This study proposes a pneumatic soft actuator (PSA) to achieve pure in-plane bending motion with anisotropic soft and rigid restraints. The in-plane bending pneumatic soft actuator (2D-PSA) is developed with a composite structure where a metal hinge belt is embedded into the soft material. The design method, material choice, and fabrication process are presented in detail in this paper. Tests are conducted to measure the actuating performance of 2D-PSA in terms of the relationship between the bending angle or force and the input air pressure. Dynamic response is also measured with a laser tracker. Furthermore, a comparative experiment is carried out between the presented 2D-PSA and a general PSA, with results verifying the effectiveness of the presented 2D-PSA. A robot consisting of two serially-connected 2D-PSAs and three pneumatic suckers, which can climb on a flat surface mimicking a snake’s locomotion, is developed as an application demo of the presented 2D-PSA. Its locomotion capability presents the in-plane performance and mobility of 2D-PSA.

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