Design of a Variable Stiffness Soft Dexterous Gripper

Abstract

This article presents the design of a variable stiffness, soft, three-fingered dexterous gripper. The gripper uses two designs of McKibben muscles. Extensor muscles that increase in length when pressurized are used to form the fingers of the gripper. Contractor muscles that decrease in length when pressurized are then used to apply forces to the fingers through tendons, which cause flexion and extension of the fingers. The two types of muscles are arranged to act antagonistically and this means that by raising the pressure in all of the pneumatic muscles, the stiffness of the system can be increased without a resulting change in finger position. The article presents the design of the gripper, some basic kinematics to describe its function, and then experimental results demonstrating the ability to adjust the bending stiffness of the gripper's fingers. It has been demonstrated that the fingers' bending stiffness can be increased by more than 150%. The article concludes by demonstrating that the fingers can be closed loop position controlled and are able to track step and sinusoidal inputs.

Soft Robotic Grippers

“…Yang et al connected two passive fingers to a bladder containing chambers that collapse due to negative pressure, generating the opening of the gripper. Al Abeach et al employed elongating and contracting McKibben muscles in an antagonistic configuration, achieving a force of 10N at 400 kPa. The use of multifilament McKibben actuators (measured contraction force of 70 N) as muscles, allowed Faudzi et al to develop a robotic hand mimicking the anatomy of the human one, combining the actuators with ligaments and a rigid skeleton.…”

Agricultural Robotics: The Future of Robotic Agriculture

“…In general, grasping and manipulation applications in Agri-Food require robustness to the unforeseen, while maintaining their ability to actuate with precision. One way to achieve this is through variablestiffness actuators [45], which incorporate elastic structures, much like humans.…”

Soft Robotics: A Review of Recent Developments of Pneumatic Soft Actuators

“…Also, integration of various new technologies has helped push the boundaries of soft robotics. Many of soft robotics projects ultimately attempted to make soft robotics more controllable, more predictable, more robust, and more manufacturable through innovation and study [151][152][153][154]. In addition to various attempts, there is still much to learn and explore in the field of soft robotics, particularly in regards to flexible power supplies, flexible drive components [147], and onboard controllers, which represent the next obstacles to the commercialization of soft robotics [10,21].…”