Modelling and characteristics of a fluid-driven bi-directional motor for an angular position-control system

Abstract

A water-driven spindle was developed for use in ultra-precision machine tools. Features of this spindle are: (a) it utilizes water flow power to spin the spindle rotor and (b) it utilizes the water pressure to support the rotor. Bend flow channels are formed in the cross-sections of the spindle rotor so that the power of the water flow can be converted into driving power for spinning the rotor. This paper proposes a spindle structure similar to that of the water-driven spindle. A feature of the proposed spindle is that it can be driven in either rotational direction by switching the supply ports. By virtue of the feature of the proposed spindle, angular position control will become achievable by designing an appropriate control system. Prior to developing the angular position-controllable spindle, a testing device, named the fluid-driven bi-directional motor, was developed. This paper deals with the modelling of the motor that will be needed for designing the angular position control system. The derived mathematical model is then evaluated by comparison with the experimental results. It is then verified that the derived mathematical model is capable of representing the static as well as dynamic characteristics of the motor.