Kinematic design


Linkages are among the most classical and typical constructs in general mechanical engineering. In precision engineering, oftentimes flexures are applied, which are covered in Chapter 3. Nonetheless, in many important cases, linkage type transmissions are useful, while also the kinematic concepts that were developed for linkages bear direct relevance for flexure mechanisms. Therefore, this chapter will treat some basics of kinematics and linkage synthesis.
This chapter will treat basic kinematic concepts like degrees of freedom, mobility, static determinacy, kinematic determinacy, exact constraintness, instantaneous center of rotation, singularity, mechanical and geometrical advantage, transmission angles and their relationships. Normally, singularities are to be avoided but situations will be discussed where profitable use is made of them. Similarly, while exactly constrained designs have important advantages, there can be good reasons to consciously deviate from this paradigm. Methods for kinematic analysis and synthesis will be explained, from classical ones such as Grübler-Kutzbach-Chebychev to modern ones like Freedom and Constraint Topology.
Special attention is directed to elements to constrain degrees of freedom, ranging from joints or kinematic pairs, typically used to allow certain motions, to kinematic couplings that are typically used for repeatable positioning. In the latter case, unilateral constraints are used which leads to the need for an extra constraint or so-called nesting force. Methods for the determination of suitable configurations will be provided.


Design principles