Planar parallel manipulators: Structure based selection from the viewpoint of workspace

It is known that serial manipulators generate greater workspace. Recent trend is tot use planar parallel manipulators where heavy loads are to be handled. There are a large number of planar parallel structures available with the same number of links and degree of freedom (d.o.f.). However, there is no quantitative measure to estimate the parallelism present in a chain. Mathematical measures are proposed to estimate parallelism that exists in a chain. since it influences the rigidity and workspace. Also, formulae are suggested to get insight of the workspace generated, i.e., well conditioned or not.