Universal Design of Four-Wheel Independent Steering System

第一个财政年度(2004)的一个主要研究课题是四轮独立转向汽车转向和牵引力/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。上行侧为主动转向车辆的普通控制器。参考轮胎负荷的最小极大准则，在下游侧对转向角和纵向轮胎力进行优化。证明了该问题归结为一个凸优化问题，并结合二进制搜索和黄金分割法进行了有效的求解。在MATLAB/SIMULINK环境下，利用CarSim软件进行了数值仿真。2005年，我们专注于轮胎力优化的实时实现，因为分配器必须处理一系列静态优化问题，才能使系统与相当简单的反馈控制器同步。结果表明，原有的算法不足以满足在MATLAB/Simulink环境下可用的实时研讨会的要求。因此，我们发展了一个渐近收敛到精确解的近似算法。对于我们基于CarSim的驾驶模拟器来说，新算法已经足够快了。对包括双车道改变在内的实验对象进行了实时仿真，结果证实了它们对行驶性能的贡献。

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.