Shirou Nakano

Fault-tolerant automobile steering based on diversity of steer-by-wire, braking and acceleration

Steer-by-wire (SBW) systems, which have no mechanical linkage between the steering wheel and front wheels, are expected to improve vehicle safety through better steering capability. SBW system failures, however, can cause hazardous driving situations. This paper introduces fault-tolerant architecture based on diversified steering mechanisms consisting of SBW backed up with steering by braking and acceleration during SBW failures. These backup steering functions are chosen according to drivers intention of deceleration and acceleration. A loss of SBW function during front-obstacle avoidance on a straight highway is investigated by driving simulator experiments. The results show that the driver can maneuver the vehicle by the steering wheel during the SBW failures. Both cost and volume increase by excessive redundancy within SBW is avoided by the diversified design, thus facilitating SBW application on new-generation vehicles.

Resistance torque control for steer-by-wire system to improve human–machine interface

A steer-by-wire system, which has no mechanical constraints between steering wheel and front wheel, is expected to improve steering performance. The mechanical resistance torque is not transmitted from the front wheel to the steering wheel, and it is essential to simulate the torque around the steering wheel for better human-machine interface. Previous studies investigated resistance torque control originating from vehicle behaviour variables such as yaw rate and lateral acceleration. However, other variables such as steering wheel angle and front wheel actuation force are also good candidate sources to generate resistance torque. In this paper, first, four general guidelines are introduced to evaluate three types of resistance torques, i.e., the steering wheel angle origin, the steering force origin and the vehicle behaviour origin. First two guidelines are for ‘driver-made’ phase to make a turn, while the third guideline is for ‘vehicle-made’ phase to return to straight driving and the fourth one is the applicability guideline. Satisfaction of these guidelines by each of the three resistance torques is examined by the actual vehicle experiment. A necessity of combining these three types of resistance torques is indicated as a future subject.

Performance-improved simulator for the quantification of steering feel and vehicle maneuvering

Since the early eighties, significant progresses in terms of stability and safety have been observed in passenger cars. Nevertheless, driver impression of current vehicle is not always positive. The sense of unity with the vehicle is important for the driver to feel fun while driving. Enthusiastic drivers prefer cars of the good old days not only because of styling or scarcity reasons, but for the pleasant feeling at accelerating, steering and braking. They enjoy driving vehicles with straightforward commands in contrast to modern ones with their excellent dynamic and safety performance but partly decoupled commands.

Torque Feedback Control for the Hand-Wheel Actuator of SBW Based on Active Disturbance Rejection Controller

The nonlinear friction, parameter perturbation and other inner or external disturbances existing in the hand-wheel actuator (HWA) of steer-by-wire system (SBW), have a bad effect on the torque feedback control of SBW. In this paper, a new torque feedback controller based on the active disturbance rejection control theory (ADRC) is proposed for the torque feedback control of the HWA of SBW. The ADRC controller includes three components: Tracking Differentiator (TD), Extended State Observer (ESO) and Nonlinear State Feedback (NLSF). It can estimate the inner and external disturbances including the nonlinear friction disturbance and compensate them in real time. The simulation results show that ADRC controller has better performance than PID controller in the robustness to the nonlinear friction disturbance.