This paper describes the development process for acceleration sensors used on automobiles and acceleration evaluation system especially for the acceleration in super low range frequency.
Acceleration sensor is indispensable not only for good vehicle motion control system, for example, active suspension control system, antiskid control system and four wheel steering control system, but also for safety system like air bag control system. This work focused on the development process of acceleration sensor which applied piezo ceramics.
Features of newly developed sensor are as follows.
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1)
Achievement of self-diagnostic function to detect sensor failure utilizing the characteristics of piezo ceramics
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2)
Addition of piezo ceramic to cancel the pyro-effect achieved stabilization of sensor characteristics and enabled to detect acceleration of 0.0025G in super low range frequency of 0.05Hz.
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3)
Incorporates impedance conversion, filtering and temperature characteristics compensation circuitry.
Frequency range of acceleration for good vehicle motion control is considered to be from DC to about 50Hz.
But the measurement of acceleration in thus super low range frequency near DC had been difficult because of its mechanical and electrical noise interruption.
This had delayed the development of acceleration sensor for automotive use.
We succeeded in the development of acceleration measurement system for super low range frequency from 0.01Hz to 2Hz with detecting acceleration range from 0.0002 (0.2 gal) G to 1G as well as the development of piezo type acceleration sensor for automotive use.