Universal Design of Four-Wheel Independent Steering System

2004年度的主要研究课题是四轮独立转向车辆的转向和牵引力/制动力分配的综合控制的理论研究。研究了一个由两级组成的串级控制系统。上游侧为主动转向车辆的普通控制器。转向角和纵向轮胎力在下游侧参考轮胎工作负荷的最小最大标准进行优化。我们已经证实，该问题是减少到一个凸优化，并有效地解决了二分搜索和黄金分割法相结合。在MATLAB/Simulink环境下，利用CarSim进行了数值仿真。在2005年，我们集中在轮胎力优化的实时实施，因为分配器必须处理一系列静态优化问题，使系统可以与相当简单的反馈控制器同步。原来的算法是不够有效的实时车间，我们可以在MATLAB/Simulink环境中。因此，我们开发了一个近似算法，渐近收敛到精确解。新算法对于我们基于CarSim的驾驶模拟器来说足够快。对包括双车道变换在内的实验对象进行了实时模拟，结果证实了它们对驾驶性能的贡献。

A major study subject for the first fiscal year (2004) was a theoretical investigation on integrated control of steering and traction/braking force distribution of the four-wheel independent steering vehicle. We studied a cascade control system that consists of two levels. The upstream side is an ordinary controller for active steering vehicle. The steering angles and longitudinal tire forces are optimized at the downstream side in reference to the minimax criterion of the tire workload. We have confirmed that the problem is reduced to a convex optimization and solved efficiently with a combination of binary search and the golden section method. The numerical simulation was performed with the CarSim in the MATLAB/Simulink environment. In 2005, we concentrated on a real-time implementation of the tire force optimization, because the distributor must process a sequence of static optimization problems so that the system can synchronize with the rather simple feedback controller. It turned out that the original algorithm was not efficient enough for the Real-time Workshop that were available to us in the MATLAB/Simulink environment. Therefore, we developed an approximate algorithm that asymptotically converges to the exact solution. The new algorithm is faster enough for our CarSim-based driving simulator. Real-time simulations with experimental subjects including double lane changes were carried out and the results confirmed their contribution to the driveabilities.