Torque Reduction Control for an Electro- Pneumatic Hybrid Vertical Positioning System

This paper deals with torque reduction control for an electro-pneumatic hybrid vertical positioning system composed of a servomotor a pneumatic and a mechanical driving sub-system. The servomotor, coupled with a ball screw connected to the load by nut, enables to position a load vertically. The servomotor with small capacity, as well as energy saving, is required for cost down. To realize its small capacity, it is important to reduce the torque of the servomotor in moving the load. In a pneumatic system, a pressure controller generates control signals for the supplied pressure equivalent to the gravitational force of the mass of the load so as to support and move the load smoothly. The torque reduction for the small capacity servomotor needs adequate control pressure supplied to a cylinder. In the present study, a mathematical model of this system has been developed by comparing calculation data with experimental results. The controller designed by this model has succeeded in the torque reduction of the servomotor.