Actuator mechanism reduction radius optimization for precise positioning in automatic production

The purpose of the paper is to show an optimization method of the mechanism of precise positioning of a module (an actuator for automatic production). The design of the module (feed nut assembly) allows to change mechanism parameters including the drive radius in a wide range. Finding the best value of the reduction radius in terms of speed, i.e. reducing the acceleration and braking time, increasing the speed of steady motion and reducing the pause time improves the performance and efficiency of the system as a whole. This task is a priority for development engineers both in designing new equipment and upgrading. L.S. Pontryagin’s maximum principle is used for optimization. Firstly, a telescopic mechanism with a feed nut assembly is calculated and the motor is selected. Then, the mechanism is studied in order to optimize the feed nut assembly parameters in terms of obtaining the maximum efficiency (up to 90%), the minimum acceleration and braking time (selection of the drive reduction radius). It is possible to vary the type of transmission (rolling, sliding, roller-screw), pitch, thread angle and a number of other characteristics. When choosing an electric motor, machines with high overload characteristics - direct current with magnetic excitation, induction with a short-circuited valve rotor - are more preferable. Calculations are performed for a large group of modules of automatic machine-building production taking into account various combinations of actuator parameters including load capacity, operating modes, loading, losses in the motor, and a number of others. The study results are as follows: the optimal gear ratio in the mechanisms depends on the processing mode of the given movement, the type of the movement speed graph is determined by the given restrictions of phase coordinates and the value of the specific movement. It is also determined that in the case when the load changes in a wide range the radius should be chosen according to the nominal value of the load, whereas the installation between the motor and the reducer screw has little effect on the optimal value of the reduction radius. The procedure is recommended to be used at the design stage when searching for an optimal transmission device in the electric drive system of precise positioning of automatic production.

actuating module, feed nut assembly, speed, maximum principle, optimal reduction radius, positioning