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In order to reduce the over-dependence of low-cost underwater vehicles on cables, and considering that it is difficult to transmit radio signals underwater, proposeding a design scheme of vehicle combining unmanned ship with underwater vehicles on the basis of the ROS platform (robot operating system).The work shows that under the condition of reasonable utilization of ROS compatibility, advantages of USV (unmanned surface vessel) and ROV (remote operating vehicle) can be complemented greatly. The USV shares part of the functions of the underwater working module, while providing auxiliary means for inertial navigation devices, it maintains better endurance and maneuverability. ROV which focuses on underwater operation has practical functions and low volume, thus saving production costs. This system has navigation performance, intelligent level, remote control ability and expansion ability, which can provide reference for the design of some low cost underwater vehicles in a way.

In view of the fact that the problem of precise modeling difficulty exists in gyro-stabilized platform due to nonlinear factors, a kind of method based on NARX(nonlinear autoregressive with exogenous) neural network model identification is proposed. At first, this paper illustrates the feasibility of utilizing NARX neural network identification model through simulation. Meanwhile, the paper compares and analyzes the impacts of different drive signals on the model precision. Then, in the light of the existing problem that noise affects model precision in output. It uses wavelet de-noising to preprocess output. Finally, post-optimized NARX neural network is adopted to set up the precise model of gyro-stabilized platform by simulation experiments. The simulation result shows that the method is feasible. When the swept-frequency signal is selected and used as the drive signal, the identification precision is the best. After wavelet de-noising, the identification precision can be increased by about 42 times maximally. The identification precision of the method improves about 7 to 23 times and it has a wide range of application in comparison with traditional identification methods.

This study concerns the divergence problem of Kalman filter (KF) in the strapdown inertial navigation system (SINS) initial alignment. Fading Kalman filter (FKF) and fixed point smoother (FPS) are investigated in this work, and an improved alignment algorithm is proposed. FKF ensures the fast convergence of filter, and the accuracy loss of FKF is compensated by FPS. A performance comparison between traditional KF alignment algorithm and the proposed algorithm demonstrates that the proposed algorithm performs better in terms of rapidity, convergence and accuracy.

In order to ensure that a satellite navigation receiver is able to work under the navigation warfare environment, a design for dual system anti-jamming satellite navigation receiver is proposed. Space-time anti-jamming technology is analyzed, which takes linearly constrained minimum variance (LCMV) as the optimal criterion, weighted by power inversion, enhanced anti-jamming capability of the receiver. Digital beam forming technology with a stronger anti-jamming performance is realized by feedback of satellite orientation information from baseband. Simulations show that traditional space-time interference suppression technology can realize 70dB anti-jamming capability for an interference, and by introduction of the beam forming technology, the anti-jamming capability for an interference can achieved 85dB.

In order to solve problems that deal with rhumb lines solution based on different reference ellipsoids in maritime navigation, the rhumb lines basic equations were established. After the symbolical formula of meridian arcs inverse solution being introduced, rhumb lines forward and inverse expressions which are non-iterative were derived. Finally, numerical examples were given to testify the accuracy of the forward and inverse expansions derived in this paper. Theory analysis and numerical results show that these new formulas have compact and symbolical form, and the precision of the inverse formulas is up to , which can satisfy practical utilization.

The cascade compensation algorithm for no damp strapdown inertial navigation system (SINS) is designed based on control model and error characteristic of SINS level-loop. According to stability and frequency characteristic analysis for SINS level-loop, a compensation network, which is chosen to alter either the roots location or the frequency response of the system, is cascaded with the SINS level-loop to damp the oscillatory or accumulated errors. The network parameters are attained by designing the frequency characteristic using frequency domain performance indexes, which are transformed from the expected time domain indexes. The algorithm implementation of the compensator is competed by solving the first-order differential equations set, which is derived from Laplace transform of the compensation network using intermediate variables. Results of digital simulation and test on sea proved that the system attitude accuracy improved 1 order and the system position accuracy improved 1 time when the compensation network was cascaded into SINS.

Shipboard landing of aircraft needs to acquire the real-time and precise relative position between shipboard and aircraft. If the technique of relative navigation based on differential carrier phase is used to solve the problem, the key point is fixing the ambiguity real-time and reliably. In general, wide lane carrier is used to solve the problem. At single epoch, the observable equations of double frequency wide lane carrier are ill-condition, so the code observable equations are needed to add in. Since the poor precision of the code pseudorange information, the ambiguity solved by it can’t reach the performance requirements in shipboard landing. A fitting method by selection of parameter weights is researched based on wide lane algorithm. The method estimates the two kinds of wide lane float ambiguities at first; then solves the individual ambiguity separately. It avoids the problems of poor precision from code equations. The calculation of experiment data shows that the algorithm can solve ambiguity reliably at single epoch and improve accuracy of relative position to centimeter level, which satisfies the requirements for shipboard landing of aircraft.

A passive radar system composed of Global Navigation Satellite System (GNSS) satellites and receiver on the ground is introduced. The system detects the target by measuring the Doppler frequency of reflected signal. A Doppler compensation algorithm based on navigation satellite signal divided is presented. The algorithm compensates the Doppler twice by FFT processing with divided signal. It measures the Doppler precisely and extends the Doppler measurement range. The simulation shows that the algorithm is able to acquire desired processing gain and makes it possible to detect the weak signal from target.

For its synergistic relationship, the integrated GPS/INS navigation system has been adopted in many navigation systems. The azimuth rotating Gimbaled Inertial Navigation system (ARGINS) can modulate the gyro drift and accelerometer bias by rotating the platform about the azimuth axis and so improve the observability properties of errors and the navigation accuracy. In this paper, the dynamic error model and the measurement model of loosely integrated ARGINS/GPS system for kalman filter are derived first,then the simulation is carried out for integrated ARGINS/GPS system, which adopts the position and velocity as its measurement variables. The simulation result shows that the ARGINS/GPS system can improve the evaluation precision and the quickness of horizontal misalignment angles of platform, compared with the integrated system of northpointing GINS and GPS.

The GPS system is capable of one-way communication (OWC) if the reserved bits of navigation message are utilized. Excluding the potential communication protocol overheads, a single frequency with one satellite transmits data at 0.5B/s; with the dual frequency transmission by using L1C and L2C frequencies, the parallel transmission of multiple satellites and the data compression, the transmission rate can be increased to 8B/s. The one-way communication of GPS is covert due to the covertness of communication channels, the occasionality of one-way communication and the disorderly distribution of information. The encryption techniques can make it difficult to discriminate communication events and decrypt communication content. The GPS one-way communication has the advantages of global coverage, day-and-night and all-weather operation, as well as low cost, thus it can meet the needs for special purposes, such as civilian emergency broadcast communication, military submarine command system and command of intelligence collection.

There are two main techniques to disable GPS user receivers from performing navigation fix, either causing interference on transmission route segment or using directional signal radiation on satelliet segment. This paper introduces a new Denial of Service (DoS) technique of GPS receivers that operates on the user segment, which is based on hidden messages from the user segment. The paper focuses on the analysis of the feasibility and covertness of using a large number of reserved bits in GPS L1C Nav navigation message to carry and transmit hidden messages, as well as of the feasibility of using expanded data types of GPS L2C CNav navigation messages to transmit hidden messages. Based on the reserved bits in GPS L1C Nav, two formats of hidden messages are designed, with mainframe and superframe as basic carrying units for transmission. Besides, the paper presents four approximate representations of DoS target areas, and probes into the position matching in DoS of GPS receivers. The research in this paper shows that it is feasible to realize DoS of GPS receivers based on hidden messages and hidden messages are provided with high convertness by transmission channels.

GPS is widely used by civil aviation, financial institutions and transport sector and other civilian sectors, as well as for military purposes, thus the research on GPS spoof is of considerable merits. This paper analyzes the roots of forgeability and dupability of civil GPS signal; then, according to the characteristics of GPS civil signal, four forgery patterns of GPS spoofing signals are presented, which are navigation message forgery pattern, C/A code modulation forgery pattern, secondary carrier modulation forgery pattern and combination pattern; furthermore, two subpatterns of GPS navigation message forgery pattern, including GPS satellite signal fail forgery subpattern and GPS satellite fixing parameters forgery subpattern, are put forward with their detailed forgery techniques.

Aiming at the authentication of civilian signals broadcasted by currently orbiting GPS satellites, this paper proposes a new technique, which carries GPS authentication information by the messages hidden in the navigation message and, without affecting the position fixing of GPS receivers in use all over the world, appends the capability of authenticity verification to current civilian GPS signals. Hidden messages are transmitted to receivers through reserved bits in the Nav navigation message or newly-added CNav message types. The civilian GPS signal authentication information is obtained by using the Hash function to convert the navigation message and (or) C/A code into Hash code and then digitally signing the Hash code with public key encryption algorithm. This paper also analyzes the feasibility, covertness and channel capacity of the hidden message transmission, puts forward several design samples of navigation message formats and explores the issues of the use patterns of hidden messages and the number of public/private key pairs.

To improve real-time performance of narrow band interference(NBI) suppression in Loran-C system, algorithm of accumulation and average is presented based on the analysis of the structure of Loran-C pulses. After that, effects of synchronous carrier wave interference(CWI) and the interference whose frequency is integral multiple of 0.5kHz upper or lower than that of Loran-C signal are simulated and analyzed. The simulation results show that the presented algorithm can suppress the CWI mentioned above effectively. Moreover, the mean square error of the algorithm does not change with signal to interference ratio(SIR), and is always on the level of 10-6. And then, the validity of the algorithm is proved by the experiment.