Design and Simulation of a Mechanical Hand

A variety of mechanical hand designs have been developed in the past few decades. The majority of the designs were made with the sole purpose of imitating the human hand and its capabilities; however, none of these designs have been equipped with all the motions and sensory capabilities of the human hand. The primary goal of this thesis project was to design a robotic hand with the required amount of degrees-of-freedom and necessary constraints to achieve all the motions of the human hand. Demonstration of the American Sign Language (ASL) alphabet, using a virtual design and controls platform, was used as a means of proving the dexterity of the designed hand. The objectives of the thesis were accomplished using a combination of computerized 3-D modeling, kinematic modeling, and LabView programming. A mechanical hand model was designed using SolidWorks. Actuation methods were incorporated into the design based on the structure of the connecting tendons in the human hand. To analyze the motions of the mechanical hand model, finger assemblies were manufactured at two different scales (full and ¼ size) using rapid prototyping. These finger assemblies were used to study the developed forces within the joints prone to failure when subjected to actuation and spring forces. A free body diagram and an Ansys model were created to quantify the force and stress concentrations at the contact point of the pin joint in the distal interphalangeal joint, a location of failure in the rapid prototype assembly. A complete kinematic model was then developed for the mechanical hand using the Denavit-Hartenberg principle to map all the joints of the hand and finger tips in a universal frame of reference. A program was developed using LabView and Matlab software tools to incorporate the developed kinematic model of the designed hand and plot the 3-D locations of all joints in the universal frame of reference for each letter of the ASL alphabet. The program was then interfaced with the SolidWorks hand assembly to virtually control the motions of the designed assembly and to optimize the hand motions. In summary, a mechanical human hand model and interacting software platform were developed to simulate the dexterity of a designed human hand and to implement virtual controls, based on kinematic modeling, to achieve the optimum motion patterns needed to demonstrate the ASL alphabet. The designed hand was capable of performing all the static gestures of the ASL alphabet