High precision locking control based on fiber optic gyro and photoelectric encoder for rotational inertial navigation system

Liu

et al. 2023

Applied Sciences

An optimized scheme can improve the navigation accuracy of RINS without changing the inertial devices. In the multi-position stop scheme, the IMU remains stationary for most of the time, which makes motor control easier. However, the installation errors and the scale factor errors of FOG can cause platform misalignment after a certain angle of rotation around the horizontal axis, resulting in a velocity error. Continuous rotation can suppress time-varying errors better, which is of particular importance for FOG, but it can also increase the sawtooth error of the navigation output, and the error in the direction of rotation cannot be offset. To integrate the advantages of both rotation schemes, we propose an improved rotational modulation scheme for tri-axis RINS. In this scheme, the inner gimbal rotates in a two-position and four-order manner, while the middle and outer gimbals rotate continuously in the order of forward-reverse-reverse-forward. Simulation and navigation test results demonstrate that this improved rotational modulation scheme can effectively improve navigation accuracy by 50% and 25% compared with continuous rotation around the azimuth axis and a 16-position scheme with the same inertial devices, which is of great importance for RINS with FOG.

Section: Introductionmentioning

confidence: 99%

An Improved Rotational Modulation Scheme for Tri-Axis Rotational Inertial Navigation System (RINS) with Fiber Optic Gyro (FOG)

Liu

et al. 2023

Applied Sciences

“…In the process, the design is focused on the servo control loop and the initial alignment because they directly determine the performance of the rotational INS. The servo control loop needs to process the analogue signal with a digital circuit and a conversion component and to keep the platform rotation continuous with the azimuth axis and levelly stabilized at the same time [12][13][14][15][16][17]. As the key technology of the INS, the initial alignment aims to calculate the misalignment angles between the platform frame (p-frame) and the local geographic frame (t-frame), and then to level the platform and align the p-frame with the t-frame, or to obtain a coordinate transformation matrix describing transforming the body frame (b-frame) to the t-frame [18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Metrology and Measurement Systems

Guo

Zhang

et al. 2019

Self Cite

Rotation modulation can significantly improve the navigation accuracies of an inertial navigation system (INS) and a strap-down configuration dominating in this type of INS. However, this style of construction is not a good scheme since it has no servo loop to counteract a vehicle manoeuvre. This paper proposes a rotary upgrading method for a rotational INS based on an inertially stabilized platform. The servo control loop is reconstructed on a four-gimbal platform, and it has the functions of providing both a level stability relative to the navigation frame and an azimuth rotation at a speed of 1.2 • /s. With the platform's rotation, the observability and the convergence speed of the estimation for the initial alignment can be improved, as well as the biases of the gyroscopes and accelerometers be modulated into zero-mean periodic values. An open-loop initial alignment method is designed, and its detailed algorithms are delivered. The experiment result shows that the newly designed rotational INS has reached an accuracy of 0.38 n mile/h (CEP, circular error probable). The feasibility and engineering applicability of the designed scheme have been validated.

“…A calibration method for gyro scale factor errors and installation errors using the outputs of the gyro and encoder is proposed (Chen et al, 2016), a data processing method is also proposed to improve calibration accuracy, and experimental results show that using the proposed methods the navigation accuracy of the system is improved. Another calibration method directly using the outputs of gyro and encoder is also proposed (Zhang Q et al, 2016), the proposed method can calibrate the accelerometer scale factor errors to a high accuracy and relax the orthogonality requirement of rotation axes at the same time. In this paper, a self-calibration method calibrating the non-orthogonal angles of gimbals using the outputs of the gyro and encoder directly is reported and the main factors affecting the accuracy of calculation are the scale factor errors of gyros and the locking accuracy of the gimbals, whose effects will be talked about in the subsection.…”

Section: Introductionmentioning

confidence: 99%

A self-calibration method for non-orthogonal angles of gimbals in rotational inertial navigation system based on fiber optic gyro

Liu

Transactions of the Institute of Measurement and Control

et al. 2017

Self Cite

Rotating modulation technique is a mature method that has been widely used in the rotational inertial navigation system (RINS). Tri-axis RINS has three gimbals, and the Inertial Measurement Unit can rotate along three directions to modulate the inertial devices’ errors, so that the navigation accuracy of the system can be greatly improved. However, the outputs of attitudes are easily affected by the non-orthogonal angles of gimbals, which should be accurately calibrated and compensated. In this paper, the effects of the non-orthogonal angles on the attitudes are discussed detailed and simulations based on Matlab are conducted to verify that firstly; then, a self-calibration method based on the outputs of the fiber optic gyroscope and photoelectric encoder is proposed. Experimental results in a real tri-axis RINS show that the attitude outputs accuracy are improved from 150” to less than 10”, which verify the practicability of the calibration method proposed in this paper.