Development and speed control of water driven stage

Abstract

Water driven stage is developed as a linear stage of the ultra-precision machine tool, especially, that is intentionally designed for the machining of small parts in size, such as optical mirrors and lenses. The water driven stage is mainly composed of a body of the stage and a table. The table is supported by water hydrostatic bearings and is driven by water hydraulic cylinder. Speed of the stage, determining the feed rate of the diamond turning, can be controlled by the flow rate into the water hydraulic cylinder. The paper deals with speed control of the stage. Mathematical models of the water driven stage and the proportional flow control valve are derived in order to design feedback control system. Performances of the designed feedback control system are verified via experiments and simulations. It is then verified that the steady state error is less than 0.5%. Step responses of the control system with a step input of the external load acting on the table are also tested, showing validity of the designed control system.

Keywords

• water driven stage
• feedback control
• water hydraulics
• ultra-precision machine tools
• water hydrostatic bearings
• modelling