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Honda has developed the SH-AWD(Super Handling-All Wheel Drive) system (Ref. 1), the world's first 4WD system capable of continuously and variably distributing torque to all four wheels of the vehicle. The use of this system enables torque to be employed in the control of the yawing moment and the application of control to equalize the load ratio between all the wheels of the vehicle. This results in higher turning stability and increased turning limit performance. These forms of control require a highly responsive actuator capable of controlling torque with a high degree of accuracy. A direct electromagnetic clutch in which solenoid attraction acts directly on the clutch was newly developed to satisfy the function described above. Detection of the solenoid air gap is required to enable high-accuracy control of solenoid attraction. A search-coil-type -sensor based on a new concept was developed and employed to enable detection of the solenoid gap.

A change of vehicle handling characteristics due to increase of lateral acceleration as well as effects of the steering gain adaptation of VGS to that was analyzed by quasi-steady-state analysis to find out a basic strategy for the adaptive gain scheduling in the VGS. A study using a simple fixed base type of simulator showed the upper and lower limit of the appropriate gain of the steering system. A computer simulation study on lane-change response of the driver-vehicle-system gave us a view that there exists a suitable gain setting for the VGS from a view point of driver-vehicle-system stability.

Using stabilizing yaw-moment diagrams, the authors analyzed three methods of active chassis control for their effect and effective ranges during cornering maneuvers. The following results were obtained: controlling the transverse distribution of driving and braking forces cancels the changes in a vehicle's dynamic characteristics caused by acceleration and deceleration. Controlling the distribution of roll stiffness is only effective in ranges with high lateral acceleration, and the effect varies depending on the longitudinal weight distribution. Controlling the rear wheel steering angle is most effective in a range with a small side slip angle, but this effect decreases with an increase in the angle, especially during deceleration.

This paper describes the development of a vehicle with four-wheel steering in which the rear wheels can be controlled electronically in addition to the conventional front-wheel steering system. In the method for steering the rear wheels, the side-slip angle at the vehicle's center of gravity is maintained at zero, which improves the basic dynamic properties of the vehicle. This approach allows greater maneuverability at low speed by means of counter-phase rear steering and improved stability at high speed through same-phase rear steering. However, the use of counter-phase rear steering to improve maneuverability gives rise to problems in regard to practicality. In addition, continuously controlled four-wheel steering, using counter-phase at low speed and same-phase at high speed, leads to many other problems regarding practicality because of the strong apparent understeer characteristics.