| Vehicle driving simulators are widely used in the development of new vehicles, training drivers and other all kinds of scientific research. With the deepening and extension of its application, the requirements of simulator performance are higher and higher. The vehicle dynamics model and six degrees of freedom(6-DOF) motion platform are the two most important parts. At present, in the simulator development process, dynamics modeling and motion platform design are nearly independent, so some problems appear subsequently such as matching debugging difficulty, high risk, and lack of theoretical guidance. To solve these problems, the co-simulation system of vehicle dynamics and6-DOF platform based on Vortex is first established in this dissertation, the dynamics model,6-DOF model, kinematics inverse calculation algorithm and Washout filtering algorithm are integrated into this system, and the method of co-simulation visualization is applied by system analysis and research with Vortex multi-body dynamics software as the tool. The research ideas and methods can be applied in the development of various types of simulator, based on different dynamics software, and have universal significance.The application fields of vehicle driving simulators are introduced, and the research status both at home and abroad are comprehensive reviewed, including the dynamics simulation model and6-DOF motion platform.The co-simulation system constitutes and basic principle of vehicle driving simulators are described in the dissertation, including the function of every component of the system, the principle of system implementation, the principle of vehicle dynamics simulation subsystem and the6-DOF motion platform, its control algorithm simulation subsystem. The aims and functions of the co-simulation are summarized.The road stimulation transfer process and vehicle dynamics response process are analyzed, through the establishment of vertical vibration and longitudinal vibration differential equations of auto twin screw four degrees of freedom. According to some related parameters of a car(AUDI), the suspension nonlinear model is established and its optimization is conducted because of abnormal acceleration shock during driving. The optimal damping ratio based on ride performance and stability is calculated and the curves of the ratio changing with vehicle vibration acceleration, speed and road irregularities are obtained, the thresholds of them are ascertained. Because of difficulty in getting the road irregularities coefficient in real time, a method is given that the generalized ground resistance coefficient(GGRC) is constructed with vehicle dynamics parameters, and the threshold of GGRC is determined by vehicle simulation in flat road and sine road in order to instead of road irregularities coefficient. An optimization method of suspension nonlinear stiffness is proposed that the stiffness must be small enough to buffer the shock in a interval of spring scale as a reference of vehicle static balance state. The optimized suspension model is tested in Vortex.The system structure of6-DOF motion platform is introduced and its kinematics and dynamics are analyzed. The relationship equations of cylinder expansion speed, acceleration with platform position and orientation are established, and further simulated for several typical motions of platform. The modeling process of6-DOF motion platform based on Vortex is given. For the original position and orientation of platform, a new analytic method is proposed. The response characteristics of hinged point driving in platform model are simulated and analyzed.The Washout filtering algorithm is introduced, the traditional Washout filtering algorithm and the kinematics inverse calculation are realized in MATLAB/SIMULINK, and then simulated for two typical vehicle motions. From virtual driving, Washout filtering algorithm, kinematics inverse calculation to Washout motion simulation of6-DOF platform model are all completed in Vortex, and the whole off-line simulation is analyzed through drawing curves of related parameters. The differences between off-line simulation and real-time simulation and their roles are illustrated. The important application of Washout motion simulation in platform hydraulic components parameters designing is discussed further, and a designing method based on statistical simulation results is proposed, including the system maximum pressure, maximum flow and servo valve flow, and further, the designing expressions are also given. |
