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UAV navigation system design

In Electronic Infomation Category: U | on September 20,2011

Abstract: During the mission unmanned aircraft autonomy for navigation and CD4072BF3A datasheet and precision of high demand, the paper design based on synthetic aperture radar (SAR) supporting the INS / Star attitude combination of navigation and CD4072BF3A price and positioning system, and CD4072BF3A suppliers and navigation for the SAR image and the output of non-continuous multi-sensor integrated navigation system measures the output of the asynchronous nature of the establishment of a revised measure to solve intermittent combination of multi-sensor navigation Kalman filter model asynchronous focus for kind of navigation or positioning problems have some significance.

0 Introduction

unmanned aircraft and manned aircraft, it has small size, low cost, easy to use, low requirements of the operational environment, the battlefield survival ability, etc., much of the world army ages. Unmanned aircraft for its accuracy, efficient and flexible surveillance, interference, fraud, search, and fire conditions in the informal and other combat operations, plays a prominent role, and led to endless military academic, equipment and technology related issues.

high-altitude long-endurance UAV altitude conducive to observing the stars, for which, considering the inertia / SAR combinations, based on a combination of inertial navigation and star, can provide highly accurate SAR imaging attitude information to improve the SAR image quality.

In this paper, high-altitude long-endurance unmanned aerial vehicle navigation imaging precision requirements during the application background, carried out based on the SAR-assisted inertial navigation / star navigation, in combination with the work of non-continuous nature of the SAR, design of the SAR / INS / Star navigation positioning scheme is proposed asynchronous asynchronous multi-sensor output centralized Kalman filter algorithm can effectively improve the navigation and positioning system of autonomy and precision.

1 Kalman Filter Design

set displacement s, the aircraft position coordinates of X (s), for different values ??of displacement, have a X (s) the corresponding value when the sample displacement continuous change, get the location coordinates of the sequence {X (s), X (s +1) ... ...}, the aircraft position prediction sequence {X (s +1), X (s +2) ... ...}, the sequence is noise-driven system first-order recursive model, the x-axis equation of state is derived as follows:

measurement equation is as follows:

Zx (s) for the s plane coordinates x axis displacement measurements.

H for the measured parameters, it is by the measurement system and measurement methods to determine, not with the displacement of a constant, because a single model, taken as 1, V (s) for the measurement noise.

mean square estimation error for the Px (s +1) = E [Xx (s +1) - Xx (s)] 2 , mean square estimation error in minimum criteria, by mathematical deduction, automatic control of the aircraft can be derived Kalman filter formula, as follows:

pre-estimation equation:

calculate Kalman gain, too:

mean squared prediction error equation:

Similarly, we can derive y, z axis of the equation of state, the equation of state of the aircraft position is as follows:

Kalman filter is based on forecast increases are amended to filter recursive, its the nature, easily achieved through computer simulation, which can be completed on the aircraft position prediction, pre-estimated equation:

the same time, radar and ground station measurements to compare, adjust the aircraft because of mechanical vibrations and other causes of displacement error, the filter model:

Figure 1 block diagram of Kalman filter model of the system

2 SAR assisted the INS / Star Navigation Systems

SAR image navigation although a higher positioning accuracy and autonomy, but its only part-time work of imaging and precision of the system require a higher level of attitude, but based on star sensor Star navigation system with high accuracy attitude determination, therefore, the use of INS / Star gesture combinations, while sub-periods to access SAR image navigation signals, the system can ensure high positioning accuracy and attitude determination accuracy. Considering only the sub-time SAR image navigation work in the actual application process requires access to the main task of SAR images based navigation system, the paper design shown in Figure 2 based on the SAR-assisted inertial navigation / star attitude combined navigation system.

the inertial navigation system and satellite positioning, geographic information systems, portfolio composition mileage instrument navigation systems, both inertial navigation autonomy, real-time but also has high-precision satellite positioning system, error no accumulation, etc., to effectively overcome the inertial navigation system, cumulative error and drift error and increase system accuracy and reliability. Combination of navigation and positioning system with an optical multi-gyro, gyroscope and accelerometer constitute strapdown inertial navigation, to match the geographic information, satellite positioning information, odometer information, supplemented by information-based inertial navigation, Kalman filtering of information technology to get the best of the best integrated navigation and positioning parameters.

Figure 2 based on the SAR assisted INS / Star Navigation Systems

can be seen from Figure 1: SAR-assisted navigation system according to task by the need for flexible access to the SAR image navigation, inertial navigation / navigation part of the star attitude and ground radar tracking system, three base stations parts, a combination laser gyro strapdown inertial navigation main feature is the use of a laser gyro technology, compared with the gyroscope, the laser gyro pulse output without analog-digital conversion, the strapdown inertial navigation system the ideal components, and constitute Jie inertial navigation system inertial sensor is connected directly with the carrier, eliminating the need for complex mechanical platform, and thus more mechanical inertial navigation system is small, light weight, high reliability; addition laser gyro strapdown inertial navigation portfolio also has anti-jamming ability, short startup time and other technical characteristics to meet the flight and the aircraft quickly in the context of strong electromagnetic interference pinpoint the actual demand for precision navigation, environmental adaptability, reliability and so could well satisfy the requirements. Navigation radar tracking system via the wireless module to send the output to the unmanned aircraft, the navigation signal and output signal constitutes a feedback signal. System is the integrated use of laser gyro strapdown inertial navigation, optical distance measuring angle, satellite positioning, wireless communications, digital maps and geographic information processing, a number of base stations, radar tracking technology, the use of integrated navigation systems and autonomous fast calibration method.

3 implementations

first aircraft location and orientation by combination of ring laser gyro navigation system to achieve absolute position, direction and dynamic to keep the benchmark to establish, in conjunction with the radar system ground station positioning error of the results to eliminate the specific implementation process described as follows:

(1) the absolute position and orientation of the baseline: the aircraft is shutdown, the combination of positioning and navigation system to find the North, the initial alignment, the laser gyro, accelerometers were used to measure the Earths rotation angular velocity vector and gravity vector direction, according to the latitude region, to determine true north. Position of the baseline is to use satellite positioning systems, digital maps or geographic information to get.

(2) position and orientation maintaining benchmark dynamic: combination of positioning and navigation system to find the North, the initial alignment is complete, enter the location and orientation navigation state. In the course of flight, real-time measurement of laser gyro inertial space vehicle attitude in order to calculate the inertial coordinate system and local level transformation between geographic coordinate system, the dynamic direction of the base to maintain. At the same time, the use of information to achieve mileage instrument navigation, the aircrafts position changes.

(3) ground station real-time positioning and navigation: the ground set up multiple base stations, base station is responsible for real-time location of aircraft and location information through a wireless module and speed information to the aircraft.

(4) error elimination: SAR-assisted navigation system output and the output of the formation of ground-based radar positioning positioning error and speed error, the positioning error as the inertial navigation system input, forming a closed loop system for error elimination. Error elimination process to solve the most critical problem is the existence of multi-sensor navigation system information output SAR and Star of sync problems, this focus on the use of asynchronous Kalman filter to handle different frequency information are synchronized.

4 Conclusion

aircraft navigation is mainly the combination of location and orientation to complete navigation system, navigation system, real-time closed-loop output position and attitude information for the aircraft to provide precise direction and position coordinates of reference, while real-time information based on attitude to predict aircraft flight. Laser gyro navigation system consists of strapdown inertial navigation, satellite positioning system receiver, navigation computer, odometer, altimeter and radar systems, base station components. SAR image navigation with positioning accuracy, autonomy, and the stars star sensor attitude determination accuracy navigation system, thus ensuring the autonomy of unmanned aircraft flight.

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