School of Energy Systems Engineering, Chung-Ang University, Seoul 06974, Korea.
Department of Electrical Engineering, Hanyang University, Seoul 04764, Korea.
Sensors (Basel). 2018 Dec 11;18(12):4384. doi: 10.3390/s18124384.
The development of sensor technology enabled the use of composite sensors to measure the torque and angle of steering wheels at gradually decreasing costs while maintaining the required safety. The electric power steering (EPS) is vital to the safety of the car, therefore it is not worth sacrificing safety to save cost and the SWA control with angle sensor gradually becomes the mainstream. Existing methods to control steering wheel angle (SWA) for EPS consider the self-aligning torque as a disturbance that should be rejected. However, this torque is useful to return the SWA from an outward to the center position. Hence, we propose a nonlinear control of SWA using the self-aligning torque for EPS in the lateral control system of autonomous vehicles. The proposed method consists of a high-gain disturbance observer and a backstepping controller, where the former aims to estimate the self-aligning torque, and an auxiliary state variable prevents using the derivative of the measured signal. The nonlinear controller is designed via backstepping to bound the SWA tracking error. The self-aligning torque provides damping that can improve the controller tracking when following the same direction of the input torque on the steering wheel control. In this case, the control input can be reduced by the damping effect of the self-aligning torque. The performance of the proposed method is validated through EPS hardware-in-the-loop simulation.
传感器技术的发展使得可以使用复合传感器来测量方向盘的扭矩和角度，成本逐渐降低，同时保持所需的安全性。电动助力转向 (EPS) 对汽车的安全性至关重要，因此，为了节省成本而牺牲安全性是不值得的，带有角度传感器的 SWA 控制逐渐成为主流。现有的 EPS 方向盘转角 (SWA) 控制方法将自定心扭矩视为应消除的干扰。然而，该扭矩有助于将 SWA 从向外位置返回到中心位置。因此，我们针对自动驾驶汽车横向控制系统中的 EPS 提出了一种利用自定心扭矩的 SWA 非线性控制方法。所提出的方法由高增益干扰观测器和反推控制器组成，前者旨在估计自定心扭矩，辅助状态变量防止使用测量信号的导数。非线性控制器通过反推设计以限制 SWA 跟踪误差。自定心扭矩提供了阻尼，可以在方向盘控制上沿着与输入扭矩相同的方向进行跟踪时改善控制器的跟踪性能。在这种情况下，自定心扭矩的阻尼作用可以减少控制输入。通过 EPS 硬件在环仿真验证了所提出方法的性能。
