Experimental Evaluation of the Mechanical Efficiency of One-Degree of Freedom Mechanisms by a Low-cost Test Bench

A method to experimentally estimate the mechanical efficiency of one degree of freedom mechanisms actuated with DC motors has been developed and is outlined here. Global efficiency of an electromechanical system is introduced as the ratio between the output mechanical energy provided by the mechanism and the electrical energy supplied to the motor during given load cycles. Global electrical and global mechanical efficiency are the factors of the global efficiency relative to the motor performance and the kinematic chain performance respectively. The method requires the use of a cheap test bench which must measure the signals of voltage and current supplied to the DC motor as well as the instantaneous position of the motor shaft. The method has been applied to estimate the global mechanical efficiency of two prosthetic mechanisms and some preliminary results are reported here.