Cross-Coupling Coefficient Estimation of a Nano-gAccelerometer by Continuous Rotation Modulation on a Tilted Rate Table

Abstract

Nano-g accelerometers are widely used in the space exploration and measurement of the earth's gravitational field. It is essential to precisely evaluate error effects at high orders such as cross-coupling for applications in a dynamic environment. Nevertheless, it remains challenging to meet the precision requirements using conventional calibration measures. In this paper, we propose a method to separate the cross-coupling coefficients of a linear single-axis accelerometer by mounting it on a steadily rotating rate table that is tilted at a fixed deviation angle with respect to the horizontal plane. The gravity component is periodically modulated along the input axis per revolution. Simultaneously, a series of centripetal acceleration is applied along the cross axis in sequence while adjusting the rotation frequency of the rate table by steps. Thus, the cross-coupling coefficient can be separated by its dependence both on the modulated gravity acceleration and the centripetal acceleration. In comparison with the static multipoint angular rotation test on a tilted dividing head, the proposed dynamic modulation method demonstrates improved robustness against corruption from bias drift, with an improved uncertainty. This method to separate the cross-coupling coefficient is suitable for testing high-resolution accelerometers, without requiring high bias stability or sensitive response sustaining at ultra-low frequency. INDEX TERMNano-g accelerometer, cross-coupling coefficient, rotation modulation, static multipoint, parameter identification, model equation. I. INTRODUCTIONAccelerometers with a resolution in the order of magnitude of ng/√Hz (where g ≈ 9.8 m/s 2 denotes the earth's gravity) are important for the exploration of the temporal and spatial variation of gravitational field, providing information on the substance density distribution of our planet 1,2 . The applications range from Earth's crust movement, through resource exploration to gravity-aided navigation 3,4 . In many application scenarios like moving-base gravity measurements, accelerometers are required to resolve acceleration of nano-g or sub nano-g in airborne or shipborne environments with relatively large dynamic noises 5,6 . This requirement is demanding since the severe mechanical vibration of the moving vehicle can easily lead to corrupting effects through non-ideal responses of accelerometers. For example, the principle of the commercial airborne gravity gradiometer is based on measuring the differences between matched pairs of rotating accelerometers. In such a gradiometer, second-order coefficients of a few μg/g 2

Dynamic Calibration of Triaxial Accelerometers With Simple Setup

“…This means that, with the parameters changing as in (9), the corresponding variation of v z (t) would be:…”

“…In general, more sophisticated calibration approaches are able to estimate more complex accelerometer models. Complex models consider, for instance, nonorthogonal sensing axes [5], [7], or nonlinear components of the sensor response [6], [9]. However, for most commercially-available triaxial MEMS accelerometers, a six-parameter model, considering independent values for the three components (along the sensing axes) of offset and gain, is normally more than sufficient to fully exploit the accuracy potential of the sensor.…”

“…Consequently, these procedures need to carry out many data acquisitions, one for each time the sensor is positioned and held fixed on a new orientation. Conversely, in dynamic calibrations, the acceleration samples are acquired continuously, while the sensor is undergoing a controlled motion [2], [6], [9], [13], [14]. Consequently, dynamic calibrations typically need a single data sequence, which makes the acquisition process simpler, compared to static procedures.…”

“…The accuracy of dynamic calibration approaches strongly depends on how much and how accurate the available prior knowledge is, about the motion imposed to the sensor. Calibration approaches employing high-precision mechanical setups can reach high levels of accuracy, as they rely on a very accurate knowledge of the sensor motion [2], [9], [11], [14]. However, such setups are typically cumbersome and very expensive, therefore they are typically adopted for topgrade accelerometers, like those used in seismic or navigation applications.…”

A Highly Stable and Sensitive MEMS-Based Gravimeter for Long-Term Earth Tides Observations

“…The MEMS gravity sensor was calibrated by the tilt method [33], [34] using a biaxial dividing head with a precision of ±1 arcsecond. As shown in Fig.…”