Analysis of Human Joint Forces in Standing Posture

Using the software Anybody Modeling System, a human static-standing musculoskeletal model based on inverse dynamics is presented, which are defined as segments, muscles and joints as dements. Simulation is based on data obtained from experiments using motion capture system VICADN and force plate AMTI. In the model AnyBody Modeling System is introduced to help solve the redundancy problem and obtain results of muscle activities, muscle forces and joint forces. From the model, hip and knee joint forces could be analyzed under normal standing posture. Also, activities of the musculus rectus femoris and several other muscles of the lower limbs can be obtained. From the results it could be concluded that stresses at joints are much stronger than theoretical reasoning because of the functions of relevant soft tissues such as muscles, tendons and so on. Results show that joint forces from the simulations are in good conformation with previous experimental researches. And this complicated model would be of use for better understanding human body functions.

Constraint Force Analysis of Metamorphic Joints Based on the Augmented Assur Groups

In order to obtain a simple way for the force analysis of metamorphic mechanisms, the systematic method to unify the force analysis approach of metamorphic mechanisms as that of conventional planar mechanisms is proposed. A force analysis method of metamorphic mechanisms is developed by transforming the augmented Assur groups into Assur groups, so that the force analysis problem of metamorphic mechanisms is converted into the force analysis problems of conventional planar mechanisms. The constraint force change rules and values of metamorphic joints are obtained by the proposed method, and the constraint force analysis equations of revolute metamorphic joints in augmented Assur group RRRR and prismatic metamorphic joints in augmented Assur group RRPR are deduced. The constraint force analysis is illustrated by the constrained spring force design of paper folding metamorphic mechanism, and its metamorphic working process is controlled by the spring force and geometric constraints of metamorphic joints. The results of spring force show that developped design method and approach are feasible and practical. By transforming augmented Assur groups into Assur groups, a new method for the constraint force analysis of metamorphic joints is proposed firstly to provide the basis for dynamic analysis of metamorphic mechanism.

Static Force-Based Modeling and Parameter Estimation for a Deformable Link Composed of Passive Spherical Joints With Preload Forces

To balance the contradiction between higher flexibility and heavier load bearing capacity,we present a novel deformable manipulator which is composed of active rigid joints and deformable links.The deformable link is composed of passive spherical joints with preload forces between socket-ball surfaces.To estimate the load bearing capacity of a deformable link,we present a static force-based model of spherical joint with preload force and analyze the static force propagation in the deformable link.This yields an important result that the load bearing capacity of a spherical joint only depends on its radius,preload force,and static friction coefficient.We further develop a parameter estimation method to estimate the product of preload force and static friction coefficient.The experimental results validate our model.80.4%of percentage errors on the maximum payload mass prediction are below 15%.