Abstract
In recent years, with the emergency of high precision inertial sensors (accelerometers and gyros), gravity compensation has become a major source influencing the navigation accuracy in inertial navigation systems (INS), especially for high-precision INS. This paper presents preliminary results concerning the effect of gravity disturbance on INS. Meanwhile, this paper proposes a novel gravity compensation method for high-precision INS, which estimates the gravity disturbance on the track using the extreme learning machine (ELM) method based on measured gravity data on the geoid and processes the gravity disturbance to the height where INS has an upward continuation, then compensates the obtained gravity disturbance into the error equations of INS to restrain the INS error propagation. The estimation accuracy of the gravity disturbance data is verified by numerical tests. The root mean square error (RMSE) of the ELM estimation method can be improved by 23% and 44% compared with the bilinear interpolation method in plain and mountain areas, respectively. To further validate the proposed gravity compensation method, field experiments with an experimental vehicle were carried out in two regions. Test 1 was carried out in a plain area and Test 2 in a mountain area. The field experiment results also prove that the proposed gravity compensation method can significantly improve the positioning accuracy. During the 2-h field experiments, the positioning accuracy can be improved by 13% and 29% respectively, in Tests 1 and 2, when the navigation scheme is compensated by the proposed gravity compensation method.
Highlights
Precise navigation is an essential factor of modern carriers
The root mean square error (RMSE) of the extreme learning machine (ELM) estimation method improved by 23% and 44% compared with the bilinear interpolation in the plain and mountain area, respectively
A novel gravity compensation method for high-precision inertial navigation systems (INS) is proposed, which uses the ELM-based estimation method to obtain the optimal gravity disturbance on the track based on measured gravity data on the geoid, processes gravity disturbance on the geoid to the height where INS has an upward continuation
Summary
Precise navigation is an essential factor of modern carriers. Nowadays, most modern vehicles and aircraft depend on the Global Positioning System (GPS) for position update as they navigate. The traditional method obtains the gravity disturbance on the trajectory using a gravitational gradiometer that senses the gradient of the potential field [5] This case depends on augmenting the INS with a sensitive instrument that has a long history of technology development, but very little operational experience. The paper is organized as follows: in Section 2, the error analysis of the INS solution incorporated with gravity disturbance is proposed; in Section 3, a brief review of the artificial neural network (ANN) is introduced; in Section 4, the theory and framework of the ELM-based gravity disturbance compensation method are proposed; in Section 5, the numerical tests are designed to prove the accuracy and superiority of ELM-based gravity disturbance estimation method; in Section 6, field experiments in a city area and a mountain area are presented.
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