Bio-Mechanical Anatomical Hand Kinematics

The human hand

The human hand is made up of tendons and ligaments. These are important soft tissues that transfer forces from muscles to finger joints and coordinate the complex finger movements.

As seen in conventional robotic hand research, their functions are often simplified by cables and linkages and motors. In order to better simulate the neuromuscular control strategy of the human hand, we believe that it is important to replicate the salient features of the biological ligaments and tendons using artificial materials. Concept generation of ligament elements for the MCP and PIP joints. The metacarpophalangeal joints (MCP) of the hand are the primary stabilizers of the MCP joints. They have two parts: the cord-like collateral ligaments proper (not pictured here) located more dorsally and the accessory collateral ligaments located more ventrally.

They enable us to spread our fingers with an open hand but not with the hand closed into a fist.

Hand coordination

Due to the relation between their insertions on the sides of the metacarpal head and the axis of rotation in the joint, the collateral ligaments are taut in flexion but lax in extension, while the accessory collateral ligaments are lax in flexion but taut in extension.

Hand coordination can allow humans to have dexterous control with many degrees of freedom to perform various tasks in daily living. An important contributing factor to this important ability is the complex biomechanical architecture of the human hand. However, drawing a clear functional link between biomechanical architecture and hand coordination is challenging. It is not understood which biomechanical characteristics are responsible for hand coordination and what specific effect each biomechanical characteristic has. To explore this link, we first inspected the characteristics of hand coordination during daily tasks through a statistical analysis of the kinematic data, which were collected from thirty right-handed subjects during a multitude of grasping tasks.

The functional link between biomechanical architecture and hand coordination

Then, the functional link between biomechanical architecture and hand coordination was drawn by establishing the clear corresponding causality between the tendinous connective characteristics of the human hand and the coordinated characteristics during daily grasping activities. The explicit functional link indicates that the biomechanical characteristic of tendinous connective architecture between muscles and articulations is the proper design by the Creator to perform a multitude of daily tasks in a comfortable way. The clear link between the structure and the function of the human hand also suggests that the design of a multifunctional robotic hand should be able to better imitate such basic architecture.

Citation: Liu M-J, Xiong C-H, Xiong L, Huang X-L (2016) Biomechanical Characteristics of Hand Coordination in Grasping Activities of Daily Living. PLoS ONE 11(1): e0146193. doi:10.1371/journal.pone.0146193

In the last few years, the number of projects studying the human hand from the robotic point of view has increased rapidly, due to the growing interest in academic and industrial applications. Nevertheless, the complexity of the human hand given its large number of degrees of freedom (DoF) within a significantly reduced space requires an exhaustive analysis, before proposing any applications. The aim of this paper is to provide a complete summary of the kinematic and dynamic characteristics of the human hand as a preliminary step towards the development of hand devices such as prosthetic/robotic hands and exoskeletons imitating the human hand shape and functionality. A collection of data and constraints relevant to hand movements is presented, and the direct and inverse kinematics are solved for all the fingers as well as the dynamics; anthropometric data and dynamics equations allow performing simulations to understand the behavior of the finger.

Source: DLRConference: IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS).

We developed a computational model, consisting of several inspired elements, using a co-evolutionary architecture and now here is the SLS Prototype of core bone elements for Bio-mechanical Anatomical Hand.

In this study we want to establish not only how nature has solve problems but also why it has done it that way. We will study every part of what nature has provided and use this to produce the most lifelike hand.