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This paper deals with the steering system with conventional round steering-wheel from the view point of Steer-by-Wire system design. Steering gear ratio and control force characteristics are selected as interface variables of the steering system. The concept of ideal steering gear ratio which is derived on the basis of mapping of steering wheel angle and vehicle path angle is proposed to determine steering gear ratio. Simulator experiments are conducted to investigate the effects of interface variables on system and driver’s control performance. Validity of proposed ideal steering gear ratio would be confirmed. Candidates for objective task performance measure to define desirable control force characteristics would be determined from the test results.

The recent development of electronics has led to increased research efforts to put the active control technique to practical use in various fields of automotive technology. This report tries to identify the goals likely to be achieved by the active control technology and the subjects of study involved in research activities for this end. As a promising approach to the solution of these subjects, the report discusses the problem areas of the existing evaluation method for vehicle handling performance and then proposes feasible ideas in this field. Finally the report gives a few examples of the research methods we have successfully applied to the development of a four wheel steering system.

The rear wheel control technique for the Honda Steer Angle Dependent four wheel steering system (Honda 4WS) is based on a combination of two methods, of which one controls the rear wheel steer angle without delay by using only the steering wheel angle for control input, and the other controls the rear wheel steer angle as a nonlinear function of the steering wheel angle. These methods have been adopted to efficiently reduce a delay in lateral acceleration response during maneuvers in straight road driving by generating lateral force at the rear wheels as quickly as possible, and, in addition, to offer a higher yaw responsiveness when making sharp turns. This report tries to demonstrate the effects of these two control methods from the viewpoint of dynamics and then, based on a quantitative analysis with mathematical models, it compares these and other control methods with respect to their effects on steering responses.

This paper discusses the desired steer angle characteristics of rear wheels in the new concept of four wheel steering system in which the rear wheels are controlled as a function of the steering wheel angle in a manner that the rear wheels are steered in the same direction as the front wheels when the steering wheel angle is kept within a small range while the rear wheels are steered in the opposite direction to the front in the case the steering wheel angle is steered over a larger range. This paper also indicates the basic principle of the four wheel steering system and lists items for consideration in determining the function, and then presents a variety of effects the new steering system produces on operating performances based upon a series of proving ground tests.

At past ESV conferences, we have reported on a series of studies on how the driver's control performance is affected by vehicle steering response. These studies showed that a four-wheel steering system can reduce the delay in lateral acceleration response to steering action, which may result in better control performance of the driver. The present report examines the handling performance of an experimental vehicle fitted with a four-wheel steering system under a wider range of operating conditions. The studies were conducted using mathematical models and simulation of the driver-vehicle system, plus road tests. The findings indicate that the four-wheel steering system may provide better vehicle handling performance than a conventional two-wheel steering system. A vehicle incorporating this steering system may exhibit improved accident avoidance capabilities.

This report describes an experimental facility that allows a motor vehicle large lateral motion by the use of wide drums for the study of the man-vehicle system. The equipment has been used to study the control performance of many drivers, from unskillful to expert, against a motor vehicle's lateral motion, and results of the study are also reported. Experiments simulating lateral gust disturbance during high-speed driving have suggested that expert drivers differ very much from unskillful drivers in the following points: Expert drivers use a strategy to obtain proper information on external disturbance for programmed control of the vehicle by allowing the vehicle lateral displacement within the lane width just after the external disturbance has been applied to it, and they are capable of selecting the information, most suitable for control according to the situation, out of the many cues on the motion of the vehicle