Backlash size identification for servomechanisms with gear transmission devices

Backlash refers to the spaces between the gear teeth in a transmission device for the purpose of lubrication and accommodating thermal expansion of the gears. This space gets wider with time due to wear on machine components, leading to tracking errors on the load side as well as vibration within the system. If the backlash size can be identified by known information, it can not only be used as an index of a maintenance strategy, but also used in a control scheme to compensate for the effects of the backlash. As a result, this paper proposes an approach for identifying the backlash size using actuator-side information only. In the proposed approach, the timing of a backlash event is determined by a Hilbert-Huang Transform-based method to find the instant in time wherein the actuator side and the load side disengage, while the inertia and friction are identified by a 2-step method. Backlash size can be estimated by integrating the velocity difference between the actuator side and the load side. Experimental results verify the effectiveness of the proposed backlash size estimation method.