This is the third part of four-part series paper, where the control dynamics built on transtibial mathematical model is explained. The trajectory development and control dynamics equations with respect to obstacles detected is explained with popular algorithms employed in robotics and self-driving vehicles but . In this paper, it is mathematically and practically proved that Lagrangian of the kinetic and potential energy of artificial leg can never be equal to zero and is always equal to non-conservative forces and thus, any model based on the assumption of conservative forces is fully invalid practically. I have left r&d, so will not correct update or complete papers. The earlier version of two parts, which was able to get saved from computer crash is uploaded.