Research On Some Key Technologies About Application Of Geomagnetic Field In Space

The geomagnetism has evolved over hundreds of years through the development of different technologies for its application. It can be regarded as one of the oldest geophysical science. The development of geomagnetism enabled seafaring and paved the way for the age of exploration, causing tremendous impacts on trades, wars and cultural exchanges. The problems of the application of geomagnetic field are focused in this dissertation, including the magneto-elastic buckling analysis of Electrodynamic Tethers(EDT), the guidance and control of a cruise missile flying along a geomagnetic isoline and the algorithms for geomagnetic navigation. The main work and contributions can be summarized as follows:1. The nonlinear dynamics analysis methods for the tether element of EDT in a magnetic field are studied. Due to strongly nonlinear dynamics of EDT and complicated multi-fields coupling problems, the president dynamic models lack consideration to the effect of the space magnetic field on the behaviour of EDT, which bring problems of investigating buckling mechanism of the tether structure. To solve such problems, bifurcation characteristic of the tether element is studied in a uniform magnetic field based on the conducting elastic rod model. The trivial straight but twisted rod is described by a fixed point of a four-dimensional Hamiltonian system. Localised solutions are given by homoclinic orbits to this fixed point and the spatial complexity of localised rod configurations is explored by means of shooting and parameter continuation methods that exploit the reversibility of the system of equations. Where these collide as parameters are varied, solutions exhibit delocalisation-relocalisation behaviour. The results predict buckling instabilities and post-buckling behaviour of rods under combined mechanical and magnetic loads, which is relevant for EDT and potentially for conducting nanowires in future electromechanical devices.2. Motivated by stability problems of EDT, the magneto-elastic buckling bifurcation of EDT is studied. Both static and dynamic stability are considered. The Kirchhoff equations are used in modeling the EDT in stationkeeping phase. The International Geomagnetic Reference Field(IGRF) model is employed as the geomagentic model. The bifurcation happens when the magnetic field reaches a critical value. The results show the critical value decreases as the angular velocity increases. The results are relevant for parameter designs of EDT.3. A new guidance method for cruise missiles that makes use of geomagnetic isolines is presented. The isolines are extracted by using bilinear interpolation in the geomagnetic contour map. Path tracking is implemented in the geomagnetic map and takes into account the dynamics of the missile and its constraints. For this, the dynamic equations for the missile during its cruise phase are established. Using an inverse dynamics guidance law to implement the simulation experiments, the simulation results show that missile flight along a geomagnetic isoline is theoretically feasible. As the path made up of isoline points is determined, the missile can follow the isoline with a path tracking controller.4. The application of different nonlinear filtering techniques for geomagnetic navigation is studied, including extended Kalman filter(EKF), unscented Kalman filter(UKF), particle filter(PF) and extended particle Kalman filter(EKPF). The research evaluates the four methods for navigation of missile during its cruise phase. The measurement equations are obtained by using a surface spline method with the real regional geomagnetic data. Simulation results show all the filters have good performance in areas with abundant geomagnetic information. Among the four filters, UKF tops in the convergence rate and precision with a fairly low tuning sensitivity to the flight path. As the UKF effect is influenced by unscented conversion parameters, a method of parameters optimization using genetic algorithm is presented. The method′s feasibility is further demonstrated by robustness analysis of optimal parameters.5. Some improvements of the feature extraction for geomagnetic matching are made. The geomagnetic entropy is extracted from the total intensity of the geomagnetic field. Entropy′s performance for navigation is tested with real geomagnetic data. The matching progress is divided into two phrases: rough matching and precise matching. In the rough matching, a sub-region which includes the real position is obtained by using the total intensity of the geomagnetic field as the matching feature. The entropy is applied to precise matching in the sub-region in order to get the final result. Simulations show that the navigation effect is significantly improved with the entropy as an assistant feature. The combined match probability is much higher than the results derived from those using only total intensity as the matching feature. This is especially true when the flight vehicle passes through the area without abundant magnetic information.As has been shown, the application of geomagnetic field in sapce is a complicated problem which involves geophysics, nonlinear dynamics, flight dynamics and many other aspects. It is an active and promising research area in aeronautics and space field. Consequently, the studies in this dissertation are helpful to the technology development of the application of geomagnetic field in our country.