Development of acceleration sensor and acceleration evaluation system for super-low-range frequencies

This paper describes the development process for acceleration sensors used on automobiles and an acceleration evaluation system designed specifically for acceleration at super-low-range frequencies. The features of the newly developed sensor are as follows. I) Original piezo-bi morph design based on a disc-center-fixed structure achieves pyroeffect cancelling and stabiliza tion of sensor characteristics and enables the detection of the acceleratio n of 0.0009 G at the super-low-range-frequency of 0.03 Hz. 2) The addition of a self-diagnostic function utilizing the characteristics of piezoceramic s enables constant monitoring of sensor failure. The frequency range of acc eleration for accurate vehicle motion control is considered to be from DC t o about 50 Hz. However, the measurement of acceleration in the super-low-ra nge frequency near DC has been difficult because of mechanical and electric al noise interruption. This has delayed the development of the acceleration sensor for automotive use. We have succeeded in the development of an acce leration evaluation system for super-low-range frequencies from 0.015 Hz to 2 Hz with detection of the acceleration range from 0.0002 G (0.2 gal) to I G, as well as the development of a piezoelectric-type acceleration sensor for automotive use.