A simple method to calculate mobility with Jacobian

Although many mobility formulae have been set in the last 150 years, unfortunately, some of them are not fit for many classical mechanisms and some are indigestible. This paper gives a simple method to calculate the mobility of all kinds of parallel mechanisms only with Jacobian matrixes. It can analyze composition of degrees-of-freedom and output speeds of moving platform in passing. Furthermore, this method can be used to determine the existence of inactive joints and equivalent serial chain of complicated parallel chain.