Analytic Adjustment and Calibration of Inertial Navigation Systems Inertial Gage Unit

Аuthors

Tiuvin A. V.

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

Abstract

The research purpose is to examine the approaches to implementation of analytic adjustment and calibration procedures of accelerometer and gyroscope blocks which are included in a strapdown inertial navigation system’s inertial measurement units, and also to prove the efficiency of the presented analytic adjustment and calibration procedures and algorithms.
Procedures for analytical adjustment and calibration of groups of sensors are performed during predefined sequences of standard actuations (rotations to certain angles), applied to groups of sensors in the IMU basic coordinate system, and with the recording of the subsequent sensor’s output signals. The algorithm identifies the orientation of measurement axis and finds the estimates of some of the instrumental errors, that remain constant during the procedure, such as sensors bias (zero signal shift), scaling errors and output nonlinearity.
This article describes the analytic adjustment and calibration algorithm, which provides bias, scale coefficients, axis direction cosines and output nonlinearity coefficients of the sensor measurements. It is shown that the adjustment and calibration accuracy depends on the number of measurements and on instrument spindle center line mounting angle above the horizon, α. With up to 24 measurements, the optimal range of instrument spindle center line mounting angle is from 40⁰ to 55⁰, in accordance with developed adjustment. It is also noted that the accuracy of adjustment and calibration significantly depends on sensor measuring axis orientation in the basic instrument coordinate system. The calculations have shown that by using an optical dividing head with accelerometer zero signal variation not exceeding 2*10^-5g and α = 40⁰, within 24 measurements, the limiting errors (with probability 95%) from all perturbing factors are the following: the bias error is 0.89*10^-5g, the scaling factor error is 0.0020%, the adjustment error is 5.4 seconds of arc. For the gyroscope block with gyroscope bias variation not exceeding 0.04 degree/hour and α = 39⁰, within 24 measurements, the limiting errors (with probability 95%) from all the perturbing factors are the following: the bias error is 0.0038 degree/hour, the scaling factor error is 0.025%, the adjustment error is 26 arc seconds.
These analytical adjustment and calibration algorithms may be used during production or operation of accelerometer and gyroscope blocks or in data acquisition systems or complexes built upon them, e.g. strapdown inertial navigation systems. These algorithms provide a possibility to improve resultant accuracy of navigation equipment and to lower the technological requirements for block production, as in this case, the complexity level of some of the requirements on the accuracy of the sensor’s construction may be considerably reduced. Beside this, such devices may even be produced with standard available equipment.
This data demonstrates the high efficiency of analytical adjustment and calibration procedures on simplified tests, using available standard equipment, for periodic inspection of functionally redundant inertial measurement units during their operation.

Keywords:

strapdown inertial navigation system, inertial measurement unit, adjustment, calibration,procedure, modeling

References

1. Tyuvin A.V., Dmitrochenko L.A., Sposob kalibrovki i yustirovki bloka izmeritelei vektornoi velichiny (Method ofcalibration and adjustment unit meters ofvector quantity), Inventor’s Certificate , MKI GN01p 21/00, no.795181.
2. Tyuvin A.V.Sistemy orientatsii letatel’nykh apparatov i ikh element", Sbornik statei, Moscow, MAI, 1981, pp.5-8.
3. Tyuvin A.V., Staroverov A.Ch. Sistemy orientatsii, navigatsii i navedeniya letatel’nykh apparatov i ikh element, Sbornik statei, Moscow, MAI, 1982, pp.20-24.
4. Tyuvin A.V. Voprosy povysheniya tochnosti giroskopicheskikh i navigatsionnykh ustroistv, Sbornik stateiv, Moscow, MAI, 1989, pp.4-8.
5. Faddeev D.K., Faddeeva V.N. Vychislitel’nye metody lineinoi algebry (Computational methods of linear algebra), Moscow, Fizmatgiz, 1963, 220 p.

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