Abstract
Global Navigation Satellite System (GNSS) and Inertial Navigation System (INS) are the most commonly used navigation systems. They both have unique advantages and disadvantages. GNSS is capable of generating precise navigation solutions while enough satellites are in view. However, the GNSS signals are sensitive to the environment. While the signals is attenuated, the GNSS receiver will fail to provide reliable navigation solutions. INS is an advanced navigation system built based on Newton's law. Due to the random noises contained in the Inertial Measurement Unit (IMU), the INS navigation solutions errors diverge over time. Therefore, effective integration of the two common systems can obtain better navigation results than any individual system. In this paper, for enhancing the GNSS/INS tightly integration system with low cost, multiple receivers were employed in the tight integration. Pseudo-range and Pseudo-range rates from the multiple receivers were employed to compose the measurement vector of the integration filter. In order to reduce the computation load, a measurement difference method was proposed. The state vector dimension could be reduced with the measurement difference scheme. Both simulation and field test were carried out for evaluating the performance of the proposed method. Since it was hard to obtain GNSS raw measurements from commercial receivers, self-developed DSP+FPGA (Digital Signal Processor, DSP; Field Programmable Gate Array, FPGA) based GNSS receivers were employed in the field test. The statistical analysis of the results showed that the positioning errors decreased with the receiver's amount increasing. In addition, a measurement difference method was proposed to reduce the state vector dimension for saving the computation load with the identical navigation solutions accuracy.
Highlights
With the autonomous and unmanned systems development, reliable position and location information are becoming increasingly important and crucial [1]–[3]
The contribution of this paper was summarized as: (1) this paper proposed a low-cost method for enhancing the performance of the tight integration method; (2) a difference method was proposed in the multiple receivers based tight integration for reducing the state vector dimension, which could reduce the computation load brought by the multiple receivers
MEASUREMENT DIFFERENCE MODEL As aforementioned in Section 2.2, with more receivers included in the tight integration system, clock bias and drift are included in the state vector
Summary
With the autonomous and unmanned systems development, reliable position and location information are becoming increasingly important and crucial [1]–[3]. Position and velocity information from GNSS and SINS are directly employed as the measurement vector in the integration filter [6], [11]–[15]. In this paper, a tight integration method utilizing multiple receivers was proposed for enhancing the positioning accuracy. MULTIPLE RECEIVERS/MEMS-IMU TIGHT INTEGRATION MODEL Fig. 1 gives the structure of the multiple receivers based GNSS/INS tight integration system (MR-TI). In this method, these receivers and the INS provide pseudo range and pseudorange rates to the integration filter. The compensated INS navigation solutions are output as the ultimate MR-TI information In this method, each receiver’s raw measurements are directly conveyed to the integration filter. Where, βri is related to the clock drift [23], [24]
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