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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. [ABSTRACT FROM AUTHOR]

Roll stability loss of heavy vehicle is a severe road safety problem and modern intelligent heavy vehicle (IHV) raises new requirement for advanced roll stability control technology. Two novel roll stability control frameworks, namely active steering-active anti-roll (AS-AAR) interactive control and worst-case optimized robust control, which have potential application to guaranteeing roll stability of IHV are proposed and investigated in this paper. The first control framework is implemented based on Nash dynamic game theory in which AS-AAR shared control is investigated as a dynamic difference game so that its two players, namely AS and AAR system, can interact with each other to provide satisfactory control performance. This interactive control scheme can be applied to vehicle automated driving scenario to improve vehicle tracking performance and roll stability. Based on zero-sum game theory, the second worst-case optimized robust control scheme is also developed to guarantee vehicle roll stability. This control method provides a suitable design framework to guarantee roll stability in scenario of vehicle-to-driver handover for IHV in which the steering input from human driver is regarded as uncertain disturbance. Simulation results show that both control frameworks can effectively improve roll stability as well as lateral stability while ensuing satisfied tracking performance. [ABSTRACT FROM AUTHOR]

As a significant active safety technology towards fully autonomous driving, driver-automation co-piloting provides a new thinking for enhancing vehicle active safety and relieving driver's workload. However, the preview pattern divergence between driver and steering assistance system (SAS) may give rise to serious steering conflicts, which reduces driver's faith in SAS, cause him/her to turn off it, and even result in fatal traffic accidents. Focusing on mimicking the driver's steering behaviour, this paper proposes a human-like steering assistance scheme by adaptively varying the preview time and assistance gain of the SAS controller. Driver's preview behaviour of the road curvature is numerically identified using simulator tests along a multi-curves road, based on which a nominal preview-scheduled driver model is established. Based on the nominal driver model, a co-piloting system featuring human-like preview behaviour and a time-varying assistance penalty is proposed to formulate the steering torque-overlay dynamics of both agents in path-tracking. Next, a linear parameter varying (LPV)/H∞ controller satisfying pole placement is integrated to ensure the robustness and stability within the entire parameter space. This enables the steering assistance scheme to have a scheduled preview pattern like a human driver. Results of driving simulator experiment indicate that the proposed steering assistance scheme is able to mitigate driver-SAS conflicts and improve driver's path-tracking performance. [ABSTRACT FROM AUTHOR]

Abstract: 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 driver''s 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. [Copyright &y& Elsevier]

Steering reaction torque is one important piece of information for drivers since it has significant influence on the maneuverability of the vehicle. Even with today's advanced simulation technology, however, it is very difficult to simulate factors such as accurate steering feeling. The purpose of this study is to develop a steering Hardware-in-the-Loop (HIL) simulator that can quantitatively evaluate steering systems. The validity of this HIL simulator has been ascertained by comparing the simulation results with those obtained during actual vehicle testing. A qualitative evaluation of the influences to reflect results on the design of the system performance is also reported. [ABSTRACT FROM AUTHOR]

It was reported that Steer-By-Wire (SBW) system, which eliminates driver interference, could introduce the active front steering control easier than that with a conventional steering system. But there have been few reports on studies about reactive torque control strategy for the steering wheel. This research on reactive torque control strategy was carried out in order to improve the driver usability and maneouvrability of SBW system. It was found that the relation between what drivers feel by reactive torque when turning the steering wheel and what they feel from vehicle behaviour could be improved by means of applying newly developed reactive torque that incorporates vehicle dynamics by means of applying newly developed reactive torque reactive that incorporates vehicle dynamics parameter. [ABSTRACT FROM AUTHOR]