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DYC Torque Vectoring reduces the understeering characteristics during cornering without affecting vehicle stability. As a result, a higher cornering limit is achieved

The Chassis technology before the 1980s had been progressed as a technology of mechanical engineering field of that time. After the mid-eighties invention and practical application of four-wheel-steering system (4WS), especially the vehicle dynamics performance field out of Chassis technology became a main stream of research and development for control technology. From then on, research and development of vehicle dynamics performance has been carried out as a collaborated technology of mechanical engineering and control engineering. This paper focuses on the future tasks and direction of Chassis control technologies that mainly control cornering performance including 4WS, with three generations of Chassis control system development. The first generation is the initial stage of Chassis control technology, which started in the mid-1980s, with the development of 4WS. The second generation started with the development of control by wire technology in the 1990s. The third generation is currently developing cooperative control technology and intelligent vehicle control technologies employing external sensors.

Following to the experimental validation of the side-slip estimation by model observer, the experimental study on the effects of the side-slip control by direct yaw moment on stabilizing vehicle motion which is impaired due to nonlinear tire characteristics is carried out. A double lane change test as well as a single lane change test with braking is conducted in order to prove the effect of the control on stabilizing the vehicle motion during severe maneuvering. It is proved that the side-slip control by DYC has a higher ability to stabilize the vehicle motion compared with 4WS because the vehicle losses its stability due to deterioration of rear tire characteristics, however, 4WS has to use the deteriorated rear tire to control the vehicle motion. The side-slip control is also proved to be superior to the yaw rate control to compensate for loss of stability due to nonlinear tire characteristics.

This paper describes the controller design scheme for the hydraulic system in Direct Yaw Moment Control (DYC) System for a front-engine front drive vehicle. Regardless of the hydraulic system's characteristics changes over a wide range of operational conditions, the hydraulic system is required to achieve the desirable speed of response and stability. This paper, therefore, proposes a two-degree-of-freedom hydraulic control system consisting of reduced-order controllers to satisfy these requirements. From the results of proving ground tests, it is confirmed that the proposed control system satisfies the requirements imposed on the hydraulic system for a DYC system.

In this paper, the authors propose a side-slip model following direct yaw moment control (DYC) by sliding control. In order to calculate the control yaw moment and estimate the vehicle side-slip, an onboard nonlinear tire model is used. Both computer simulation and experiments with a real vehicle equipped with the control system yield results showing the efficacy of the control system in improving active safety.

Studies were made on the effects of braking force distribution, on a vehicle's lateral and longitudinal directions. The studies were made on distribution on non-linear regions, under combined high lateral acceleration and deceleration conditions, using the value of the yaw moment versus the side slip angle. Consequently, a method for obtaining optimum braking force distribution was found. Controlling the lateral distribution of the braking force on the front wheels was found to be effective for the improvement of vehicle stability, while that on the rear wheels was found to be effective for extending the limit of vehicle motion. Therefore, controlling the lateral distribution of the braking force on both the front and rear wheels achieves the two effects mentioned above. Simulation tests were carried out to confirm these effects in terms of turning performance and controllability to avoiding obstacles in emergency situations. (A) For the covering abstract see IRRD 864807.

SUMMARY This paper deals with a study to theoretically formulate an effective method of improving vehicle performance, particularly, its characteristics in the nonlinear region, and to verify the feasibility of the proposed method by calculations and examinations. In order to analyze vehicle characteristics in the nonlinear region, a new method of analysis was developed for determining yaw moment and side force of the vehicle with a parameter of the side slip angle at the center of gravity when its center of gravity point was fixed. The study with this new method found that direct yaw moment control by proper distribution of traction and braking forces on the right and left tires could provide a very effective means of stabilizing vehicle characteristics, specifically for acceleration and deceleration, and enlarging the limit of vehicle maneuverability.

Honda has developed the SH-AWD (Super Handling-Al 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.