The Determination of Minimum Pre-Load Torque for Antibacklash Gears in a Positional Servomechanism

A method is described for estimating the minimum pre-load torque required to obtain a satisfactory step response from a position control system incorporating spring-loaded antibacklash gears. The use of minimum pre-load torque reduces friction and wear on the gear teeth. The equations of motion are derived for a geared motor and load when the gear teeth are in contact and when they pass through the backlash zone. The motor and load are then considered as part of a closed-loop system whose response to a step input is obtained from a computer simulation. Optimum values of pre-load torque are selected and, based on these, a set of formulas is obtained. This set of formulas enables the minimum pre-load torque to be calculated for the above type of system, given the motor/load inertia ratio, the system bandwidth, and the backlash angle.