Control of an Air Spring Type Anti-Vibration Apparatus Using Differential Signal of Relative Position

Abstract

An air-spring type active anti-vibration apparatus has been widely used in the field of precision positioning. In order to avoid the deformation of main body supported by air springs and to compensate the incline of this body due to the mounted positioning unit, the pressure feedback having the positive feedback of differential of relative position signal was already proposed. This feedback has also the elimination function of air spring stiffness. Then, this paper first addresses the issue of low natural frequency of transmissibility. In detail, the frequency response shaping for transmissibility is clarified in case with and without the cancellation of air spring according to the magnitude of position servo stiffness. Next, the minimum output noise level for the positioning sensor is derived on the condition that the proposed positive feedback dose not influence on the deformation of supported body. As a result, the noise level less than 380 mV is derived under the constraint on the driving force 1 N.