A new method is presented in this paper for the kinematic analysis and synthesis of Epicyclic Gear Mechanisms （EGM） for automatic transmissions. The EGM is decomposed into several basic EGMs. To perform the overall speed ratio analysis of an EGM

the basic speed ratios are derived from the kinematic equations and the other speed ratios are derived from the basic speed ratios and the speed ratio relations. To perform the gear ratios synthesis

the exact solution of gear ratios is obtained from the kinematic equation and the geometric constraint of each basic EGM. The advantage of this method is that the kinematic synthesis of EGMs can be solved without the need of optimization manipulation. Based on this

a program is developed in VB language to analyze and synthesize the EGMs kinematically

which has a perfect man

m

achine interface and could be manipulated easily. All kinds of help are shown in order that user can input correct data.