Soft curvature sensors for measuring the rotational angles of mechanical fingers

The design, fabrication, and testing of soft sensors that measure elastomer curvature and mechanical finger bending are described in this study. The base of the soft sensors is polydimethylsiloxane (PDMS), which is a translucent elastomer. The main body of the soft sensors consists of three layers of silicone rubber plate, and the sensing element is a microchannel filled with gallium-indium-tin (Ga-In-Sn) alloy, which is embedded in the elastomer. First, the working principle of soft sensors is investigated, and their structure is designed. Second, the relationship between curvature and resistance is determined. Third, several sensors with different specifications are built in accordance with the structural design. Experiments show that the sensors exhibit high accuracy when the curvature changes within a certain range. Lastly, the soft sensors are applied to the measurement of mechanical finger bending. Experiments show that soft curvature sensors can effectively reflect mechanical finger bending and can be used to measure the bending of mechanical fingers with high sensitivity within a certain working range.

The Development of a Two-finger Dexterous Bionic Hand with Three Grasping Patterns-NWAFU Hand

Bionic inspiration from human thumb and index finger was the drive to design a high-performance two-finger dexterous hand.The size of each phalanx and the motion range of each joint in the human thumb and index finger were summarized,and the features of three grasping patterns were described in detail.Subsequently,a two-finger dexterous bionic hand with 6 Degrees of Freedom(DoFs)was developed.Both the mechanical thumb and index finger were made up of three rigid phalanx links and three mechanical rotation joints.Some grasp-release tests validated that the bionic hand can perform three grasping patterns:power grasp,precision pinch and lateral pinch.The grasping success rates were high under the following cases:(1)when power grasping was used to grasp a ring with external diameter 20 mm-140 mm,a cylinder with mass<500 g,or objects with cylinder,sphere or ellipsoid shape;(2)when the precision pinch was used to grasp thin or small objects;(3)when the lateral pinch was used to grasp low length-to-width ratio of objects.The work provided a method for developing two-fimger bionic hand with three grasping patterns,and further revealed the linkage between the difference in fimger structure and size and the hand manipulation dexterity.

A 3D-printed Robot Hand with Three Linkage-driven Underactuated Fingers

In this study, we improved an underactuated finger mechanism by using Solidworks to simulate the grasp operation of a finger in some different situations. In addition, a robot palm is designed for the three-finger robot hand with the designed underactuated fingers. A Solidworks simulation was used to verify the rationality of the design. Some parts of the hand were modified to fit for 3D printing, and a prototype of the hand was produced by 3D printing, which could reduce the cost of the production process, as well as provide design flexibility and other advantages. Finally, some grasping experiments were made with the prototype. The results showed that the robot could grasp objects with different sizes, and further verified the rationality of the design and feasibility of fabricating the robot hand using 3D printing.

Development of Novel Hybrid Hand Formed by a Parallel Wrist and Three Soft-flexible Fingers

A prototype of a novel hybrid hand is developed by combing a parallel wrist with three flexible fingers.Its dynamics model is established,its grabbed forces are measured,and its grabbing performances are analyzed.First,Jacobian and Hessian matrices of the moving platform in the parallel wrist are derived,the kinematics formulas for solving the general velocity and the general acceleration of the moving platform are derived.Second its dynamics model is established for solving the dynamic actuation forces,the dynamic constrained forces of the developed hybrid hand.Third,its simulation mechanism is constructed in Matlab,and the theoretical solutions of the kinematics and the dynamics of the developed hybrid hand are verified to be correct using its simulation mechanism.Finally,when objects with different mass are grabbed by prototype of hybrid hand in different poses,the grabbed forces are measured,and the grabbing performances are discovered and analyzed to verify its merits.