Macroscopic drive chain efficiency modeling using state machines

In this paper, we propose a new approach to model irreversibility in robotic drive chains. Actually, some types of gears such as worm gears have an efficiency which varies according to the power flow direction. The irreversibility appears when the efficiency tends to zero in one direction only, usually, from the load to the motor. The proposed methodology consists of using a state machine to describe the functional state of drive chain. For each state, an efficiency coefficient that characterizes the power loss is defined. This technique gives conclusive results during experimental validation and allows reproducing a reliable robot simulator. This simulator is set up for the purpose of position control of a medical positioning robot.