Development of a mathematical model for vane-type air motors with arbitrary N vanes

The paper presents a mathematical model for vane-type air motors with arbitrary number of vanes. The paper starts from the working principles of the air motor and modeling approach. Then the mechanical geometry structure of air motors is analyzed in order to derive a generic mathematical description of the air motor. A complete dynamic process of the air motor system is derived based on the mechanical structure, orifice and other physics theory. The simulation results are presented with a typical set of air motor parameters. Due to the nature of the motor structure, the chamber volume changes are discontinuous which leads to discontinuous chamber pressure variations. The characteristics of the discontinuity present difficulties for applying advanced control theory to air motor control. Therefore, further approximations are carried out and the comparison of dynamic responses between the original model and the approximated model indicated that the approximation is accurate enough to be acceptable for control strategy development.