Linear encoder based low frequency inertial sensor

Christophe Collette,Sylvain Hellegouarch,Kurt Artoos,Pierre Lambert,Lionel Fueyo Roza,Y Bellouard

doi:10.1051/matecconf/20153206001

Christophe Collette, Sylvain Hellegouarch + Show 4 more

Open Access

https://doi.org/10.1051/matecconf/20153206001

Copy DOI

Abstract

For many applications, there is an increasing demand for low cost, high-resolution inertial sensors, which are capable of operating in harsh environments. Recently, a prototype of small optical inertial sensor has been built, using a Michelson interferometer. A resolution of 3 pm/√Hz has been obtained above 4 Hz using only low cost components. Compared to most state-of-the-art devices, this prototype did not contain any coil, which offers several important advantages, including a low thermal noise in the suspension and a full compatibility with magnetic environments (like particle collider). On the other hand, the Michelson is known to be tricky to tune, especially when one attempts to miniaturize the sensor. In this paper, we will propose a novel concept of inertial sensor, based on a linear encoder. Compared to the Michelson, the encoder is much more easy to mount, and the calibration more stable. The price to pay is a reduced resolution. In order to overcome this limitation, we amplify mechanically the relative motion between the support and the inertial mass. First results obtained with the new sensor will be discussed, and compared with the Michelson inertial sensor.

Highlights

Inertial sensors have been used for more than a century mainly to answer the needs of seismology, the science which studies the propagation of waves through the Earth
In the field of security, miniature autonomous optical inertial sensors have been tested for the detection of detonation arising from nuclear tests conducted by countries engaged in nuclear proliferation [11,12,13]
In order to measure the relative displacement between the inertial mass and the support, we have developed a sensor based on a Michelson interferometer, adapted to enable the measurement of both quadratures of the signals as in [7,29]

Summary

Introduction

Inertial sensors have been used for more than a century mainly to answer the needs of seismology, the science which studies the propagation of waves through the Earth. It has been obtained in two steps. We have recorded the signal without disturbing the interferometer, and used the parameters from the first step to express the photodiode signals as sensor noise in displacement units It results in a resolution of 3 pm/√Hz above 1 Hz, and 20 pm/√Hz above 0.3 Hz [30]. Besides this performance, a possible weakness of NOSE may be that the calibration of the interferometer fluctuate over time, due to misalignment of the optical components. We will investigate the possibility to replace the Michelson interferometer by an linear encoder

Linear encoder test bench

Inertial mechanical amplifier

First concept

Second concept

Conclusions