Coupler curves are the close curves that can be smooth

have a point of inflection

or contain one or two cuspidor points

or contain a BALL point.Since design on a locus generation mechanism generally expresses as nonlinear equation groups on mechanism dimensions

people cannot but adopt numerically iterative methods to solute.In order to reduce difficulties on solution

a no-iterative design method is studied on coupler curve with bi-cuspidor points of crank-rocker mechanism.It can directly design a crank-rocker mechanism with bi-cuspidor points on locus when the limited displacement of a point on the link is known

thus avoiding a series of problems of optimizing design method.