Kinematics of rigid mechanisms

Abstract

In this chapter two main topics have been treated. First, the definition and description of kinematic pairs have been explained. We saw that there are kinematic pairs, called lower pairs, which have the feature of being describable independently of their configuration. These pairs are the most important ones in practice. Bond graph interpretations have been given.

Second, all the possible rigid mechanism have been analyzed and explained. It has been shown that, in general, the actuation space does not correspond with the configuration space. A typical example is a human arm: this has few degrees of freedom but a lot of muscles. These muscles could be modeled as extra actuated pairs. The resulting describing mechanism would then correspond to a closed chain mechanism. We have seen that such mechanisms can have internal forces. For a human arm these forces correspond to the contemporary contraction of opposite muscles like the biceps and triceps.