Research On Dynamics Modeling And Attitude Stability For Floating Unmanned Platform

Following the increasing emphasis on marine resources and maritime rights, there is a sharp rise trend of territorial disputes between countries. To safeguard the sovereignty and rights of our territorial sea, the development of naval equipment shows great significance. With unmanned war becomes an important trend of wars, marine unmanned combat system gets wide attention in recent years, and many countries have stepped up research efforts. Considering the advantages of surface and underwater unmanned combat systems, we propose a concept of a multipurpose floating unmanned platform, using for alert reconnaissance, which has small size, compact structure, easy assembly and transport. Due to the difference of structure, working environment and mission requirements between the platform and other conventional platforms mounted in vehicles, ships and other large motion carriers, it is need to consider the particularity of water application environment and small size carrier platform and the resulting dynamics coupling. Research on modeling and attitude control for the unmanned platforms, which has important significance in development and application of marine unmanned combat systems and such floating platforms.In this thesis, taking a floating unmanned platform as the study object, the dynamics of the platform and the theoretical and technical problems in attitude stabilization have been studied. The dynamic coupling caused by the load, carrier and the environment of the platform, and the mathematical model and attitude control method have been mainly studied.In order to obtain the motion characteristics of the hybrid multi-body floating platform composed by floating unit and carrier platform to guide the structural parameters design, the dynamic model of floating platform has been established based on the3-D linear potential flow theory and multi-body dynamics. The wholly dynamic model of the floating platform with several possible structures is established, and the motion response of the carrier platform has been analyzed. To reduce the hydrodynamic impact on the platform structure, and to guide floating unit arrangement,3-D frequency domain potential flow theory and GREEN function method have been applied for solving the hydrodynamic coefficients of floating unit arrays arranged in different ways. The law of hydrodynamic effects and floating unit location is obtained.Considering the characteristic of the floating unmanned platform, the improved serial-parallel attitude stabilization platform mechanical structure based on less DOF parallel mechanism has been designed, and the corresponding mathematical model is established. Parallel stable platform derived inverse kinematics equations was derived. The velocity mapping of the system was established, and the system jacobian matrix was derived. Based on Lagrange method, the dynamic model of the parallel stabilized platform was established. Considering the inertia parameters of each component separately, analysis and comparison of the effect of inertia of various parameters on the dynamic model have been done, which provide basic for simplifying the dynamic equation. To investigate the impact in the platform caused by joint clearance, the improved Hertz contact theory and non-linear spring-damper model has been introduced to calculate the contact force, and the dynamic model considering joint clearance has been established, and then verified by numerical calculation and experimental method.Unmanned platform mathematical model considering the non-holonomic constraint has been established, which provides a way to improve the control performance of such floating platform. Compared with the existing model, the proposed model takes into account the coupling between the load and the base of the system, and makes quantitative process to unmodeled dynamics, and thus closer to the actual situation. The virtual mechanism method and the D-H method have been used for dividing platform attitude angle transformation matrix and making it unified with the parallel stabilized platform. Based on Lagrange method, the non-holonomic controlled platform dynamic model has been established, and gives equivalent formula of restoring moment and flow field coupling term.According to the strong coupling, control difficulty of parallel mechanism, the control strategy unmanned platforms were studied. Workspace compound robust control strategy which is also available for other system is designed for the holonomic unmanned platform. Multi-DOF disturbance observer is applied for compensating system coupling, parameter perturbations and disturbance. Based on backstepping method, sliding mode controller is designed to suppress unobservable disturbance and tracking. When study on non-holonomic unmanned platform, Partial Feedback Linearization method is used for mathematical model transformation based on improved compound robust control strategy. The nonholonomic constraints unmanned platforms control strategy is designed. The simulation results show the robustness and accuracy of the above controllers.According to the system requirements, the hardware and software in a prototype of the platform has been designed, also the ground simulation experiment system. A device for simulating ground motion simulation was built. to carry out ground dynamic simulation experiments. The simulation experiments have been carried out in laboratory. The compound controllers were experimental researched, the robustness and control accuracy has been tested, and the effectiveness of the models and methods has been verified.