The SERF atomic spin magnetometer, which can be used to measure the residual weak magnetic field in the magnetic shield due to its ultrahigh sensitivity, is elaborated in this paper. The method of using the SERF atomic spin magnetometer to measure the residual weak magnetic field in the magnetic shield was presented. The compensating coils, which were placed inside the magnetic shield, produced the uniform magnetic fields along the x, y and z directions, and they were reverse direction with the residual weak magnetic fields; via the cross modulation method, the residual weak magnetic fields could be counteracted. At this time, the magnetic fields producing by the compensating coils were equal to the residual weak magnetic fields in the magnetic shield. The experimental results showed that the residual weak magnetic fields were approximate 0.5 nT, 1.0 nT and 7.0 nT along the x, y and z directions, respectively; and the maximum measurement errors were approximate 0.0169, 0.0377, and 0.5071 along the x, y and z directions, respectively. Finally, the reasons of measurement error were analyzed.
Present-day large mobile objects such as the ships are equipped with a large number of different devices and systems
whose mutual angular position must be known to a high degree of accuracy. Owing to static and dynamic deformations
of the object, the angular position of peripheral apparatus such as optical systems, radar antennas , etc. may differ
essentially from that of central devices. For removing the effects of angular deformation, suitable measurement methods
should be studied. The problem of evaluation for angular deformation measurement particularly is becoming urgent for
large-sized vehicles such as big ships, spacecrafts, etc. Fiber Bragg Grating (FBG) sensors can be used to measure many
different parameters including strain, temperature, pressure, displacement, electrical field etc. With the major advantages
which is attributed to wavelength-encoded information given by the Bragg grating, deformation measurement system
based on FBG is briefly introduced. As strain measured by FBG sensor can be obtained, an angular deformation
measurement method using strain information is proposed. Strain response modality model is deduced based on finite
element method (FEM). Based on strain response modality model, experiment strain modality analysis is done and strain
response calculation model can be set up. Then transformation between strain information and angle deformation is
deduced, and the results comparison between using strain response analysis method and using ANSYS analysis method
for simple ship deck structure under different loads is made. The simulation results show that angular deformation
measurement method using strain response analysis is suitable to meet the measurement requirement.
Global Positioning System (GPS) can provide precise positioning information to an unlimited number of users anywhere on the earth. However, the defect cannot be neglected, because there exists one blind district when the aerocraft flying through some altitude space. During the short time in the blind district, all radio signals can't be attained including the GPS signals. An integrated GPS/SINS (Strapdown Inertial Navigation System) Navigation system is presented in this paper. The SINS based on numerical computing platform has many advantages such as high reliability, small bulk and low cost ect. The integration of GPS and SINS, therefore, provides a navigation system that has superior performance in comparison with either a GPS or a SINS stand-alone system. This paper presents a new model-less algorithm that can perform the self-following of the aerocraft under all conditions. For improving the precision of the hybrid GPS/SINS navigation system, fusing data from a SINS and GPS hardware utilizes wavelet multi-resolution analysis (WMRA) and Radial Basis Function (RBF) Artificial Neural Networks (ANN). The WMRA is used to compare the SINS and GPS position outputs at different resolution levels. These differences represent, in general, the SINS errors, which are used to correct for the SINS outputs during GPS outages. The RBF-ANN model is then trained to predict the SINS position errors in real time and provide accurate positioning of the moving aerocraft. The simulations show that good results in SINS/GPS positioning accuracy can be obtained by applying the WMRA and RBF-ANN methods.
Optical fiber sensors can be used to measure many different parameters including strain, temperature, pressure, displacement, electrical field, refractive index, rotation, position and vibrations. Among a variety of fiber sensors, fiber Bragg grating (FBG) has numerous advantages over other optical fiber sensors. One of the major advantages of this type of sensors is attributed to wavelength-encoded information given by the Bragg grating. Since the wavelength is an absolute parameter, signal from FBG may be processed such that its information remains immune to power fluctuations along the optical path. This inherent characteristic makes the FBG sensors very attractive for application in harsh environment, and on-site measurements. But FBG sensors can measure temperature and strain simultaneously; it is necessary to decouple measurement information. In the present paper, A distributed fiber Bragg grating sensors measurement system that measures global deformations of large surface online-based FBG sensors is introduced. Short overview of the measurement principle and the signal processing realized and fusion method as well as the application of the sensor in the field of large surface will be presented. A new fusion method based on the federal Kalman filter to decouple information of the temperature and strain is proposed. The algorithm of optimum estimation fusion for distributed FBG systems based on the model of deformation of beam is studied. Simulation results and experimental results show algorithm of fusion and decoupling is an efficient method for improving performance of distributed FBG sensors system.