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Vehicle stability after releasing the accelerator during limit cornering (from now on “Tuck-in”) is the behavior that the turning radius of a vehicle gets smaller after releasing the accelerator. This paper presents that the main factors of yaw moment variation by releasing the accelerator are the change of lateral forces due to longitudinal transfer of normal loads, lateral shift of vehicle center of gravity due to vehicle roll and tire lateral deflection, and the change of lateral forces due to deceleration. It also shows that roll stiffness distribution and longitudinal acceleration have an influence through the formulation of turning radius ratio.

The recent growth of available computational resources has enabled the automotive industry to utilize unsteady Computational Fluid Dynamics (CFD) for their product development on a regular basis. Over the past years, it has been confirmed that unsteady CFD can accurately simulate the transient flow field around complex geometries. Concerning the aerodynamic properties of road vehicles, the detailed analysis of the transient flow field can help to improve the driving stability. Until now, however, there haven’t been many investigations that successfully identified a specific transient phenomenon from a simulated flow field corresponding to driving stability. This is because the unsteady flow field around a vehicle consists of various time and length scales and is therefore too complex to be analyzed with the same strategies as for steady state results.

Several methods have been studied by using adaptive control in order to tune parameters of the cruise control automatically. But theoretical analysis has not been done by the reason of severe non-linearity. In this paper, a vehicle dynamics model is made with theoretical analysis, and two adaptive control methods to assist the conventional PID controller are proposed.

Vehicles equipped with in-wheel motors are being studied and developed as a type of electric vehicle. Since these motors are attached to the suspension, a large vertical suspension reaction force is generated during driving. Based on this mechanism, this paper describes the development of a method for independently controlling roll and pitch as well as yaw using driving force distribution control at each wheel. It also details the theoretical calculation of a method for decoupling the dynamic motions. Finally, it describes the application of these 3D dynamic motion control methods to a test vehicle and the confirmation of the performance improvement.

The authors, et al. have succeeded in the practical application of the abradable flame spray coating, used in aircraft engines for the prevention of air leakage and the improvement of efficiency, to automobile turbochargers for the first time in the world. Two layers consisting of a bond coated layer and an abradable layer used to be coated by separate spray nozzles under the conventional technique. In this paper, equations of relations between various flame spray coating conditions and the quality of coated film, which were derived from measured results, will be described. Flame spray coating conditions, that allow the double layer coating by the same spray nozzle, have been determined for each layer. Temperatures and speeds of the flame were measured by means of two-color type high-speed cameras, and equations of their relations with the flame spray coating conditions are derived from the measured result.

Toyota Hybrid System (THS), that combines a gasoline engine and an electric motor was installed in the Prius, which was introduced in 1997 as the world's first mass-produced hybrid passenger car, and was vastly improved in 2003. The new Prius gained a status of highly innovative and practical vehicle. In 2005, combined with a V6 engine, THS had a further evolution as a Hybrid System for SUV, which was installed in the RX400h and Highlander Hybrid to be introduced into the world. This report will explain “new THS” which achieved both V8 engine power performance and compact class fuel economy, while securing the most stringent emission standard, SULEV.

A new method to measure in-cylinder flame propagation and mixture distribution has been developed. The distribution is derived from analyzing the temporal history of flame spectra of CH* and C2*, which are detected by a spark plug type sensor with multi-optical fibers. The validity of this method was confirmed by verifying that the measurement results corresponded with the results of high speed flame visualization and laser induced fluorescence (LIF) measurement. This method was also applied to analysis of cyclic combustion fluctuation on start-up in a direct injection spark ignition (DISI) engine, and its applicability was confirmed.

TOYOTA has adopted the Active Hydropneumatic Suspension and the Active Four Wheel Steering(Active 4WS) for the 1991 SOARER. The SOARER'S Active Suspension. is based on CELICA'S Active Suspension for the 1989 mode1(1)(2)(3)(4)(5)(6)(7). Because the Suspension has no coil springs,improvements in both ride and handling performance are obtained. The Active 4WS controls the rear steering angle by using yaw rate feedback contro1,and this is the world's first system in massproduction car. TOYOTA has integrated the ABS and TRC to these systems in the SOARER. We have succeeded in improving the total vehicle dynamics performance,and have obtained higher maneuver-ability and controllability with a total integrated system. The following describes the effects of integrated control.

In the field of automotive gasoline engines, new products aiming at greater fuel economy and cleaner exhaust gases are under development with the aim of preventing environmental destruction. Severe ignition environments such as lean combustion, stronger charge motion, and large quantities of EGR require ever greater combustion stability. In an effort to meet these requirements, an iridium plug has been developed that achieves high ignitability and long service life through reduction of its diameter, using a highly wear-resistant iridium alloy as the center electrode.(1)(2) Recently, direct injection engines have attracted attention. In stratified combustion, a feature of the direct injection engine, the introduction of rich air-fuel mixtures in the vicinity of the plug ignition region tends to cause carbon fouling. This necessitates plug carbon fouling resistance.

A description is made of new control methods to improve response of wheel slip regulation. These methods enabled a new Traction Control (TRC) system based on throttle control rather than brake pressure to be developed. Major points are as follows: (1) Use of fuel injection cut-off to minimize delay (2) Additional adaptive throttle control logic By these means, a response nearly equal to that with brake pressure control is achieved at lower cost and with a considerable weight saving. Furthermore, the system, by suppressing noise and vibration, enhances the driver's control ability.

We have developed a new vehicle dynamics control system that is based on a new concept and uses a new hydraulic modulator. The new algorithm, which reflects the concept and hydraulic modulator, can control a vehicle not only in emergency but also in normal driving situation. This results in excellent vehicle controllability.

With the increasing use of electronic control systems to improve vehicle dynamics, there is an ever growing need to transfer control information among electronic control units(ECUs). To meet this need, a protocol was proposed for high-speed multiplex in the previous SAE paper 910463. Based on the paper, a prototype IC for high-speed multiplexing control was developed. First, a further analysis was made of the information which is transferred among ECUs. As a result, it was found that the information has certain distinctive characteristics. These characteristics are so distinctive that it may be relevant to devise a new protocol for communication. Based on the analysis, a new form of token passing method was implemented. By using this method, it is easy to calculate transmission latency time. So this method is suitable for a real time control application like vehicle dynamics control.

A control law for integrating 4WS and 4WD systems is presented. It is based upon a non-linear vehicle model in which the lateral force acting on the tires changes according to the tire slip angle, slip ratio and the load. The purpose of the system is to make the actual yaw rate follow the desired yaw rate. A two-degree-of-freedom control structure has been devised and variable transformation is used to linearize the non-linear model so that H∞ control theory can be applied to design the feedback compensator. A new control theory is used to calculate optimum command values for the 4WS and 4WD actuators. Moreover, adaptive logic is added to reduce the desired yaw rate as the tires approach the limits of adhesion. Simulations and experiments prove the system greatly improves stability during cornering.

To reduse crosswind sensitivity, the yaw moment should be decreased under both transient and steady conditions. The transient condition is when a vehicle comes out immediately from a tunnel into a crosswind while the steady condition is when driving straight along the coastline. After studying the pressure distribution and the flow pattern around the body, we have reached the ideal air flow at the front-side corner that reduces the yaw moment under both conditions. And we have devised an entirely new method to achieve this better air flow. The method uses an internal flow generated by a pressure difference in the flow feeld to create a jet effect and by using only a duct for internal flow to control the outside air flow. It is done without any change to the exterior styling, except at the flow exit. We call it “Aero Slit”. This “Aero Slit” is effective only under crosswind conditions, and does not increase aerodynamic drag when a crosswind is not blowing.

This paper provides an overview of the automotive technology and its future trends mainly focussing on Japan. The future automotive technology will basically be on the projection of current technology, although it is expected more progress to be made in advanced and precision control systems. The application of electronics and development of new materials will play a very important role in this area.

We have developed a vehicle test system called the Vehicle Dynamics Simulator (VDS). The system measures the handling characteristics in a transient state in the laboratory. The automobile suspensions are moved as on a road with the machine providing relative motion by force transducer platform beneath each tire. The detailed measurements of transitive motions and forces given to the wheel clarify the kinematics and compliance characteristics contributed to the good handling performance and stability. This paper presents the system introduction and the results of analyzing the suspensions characteristics by the new analytical technique for breaking down into a variety of compliance components in a transient state.

Vehicle rollovers are one of the more severe crash modes in the US - accounting for 32% of all passenger vehicle occupant fatalities annually. One design enhancement to help prevent rollovers is Electronic Stability Control (ESC) which can reduce loss of control and thus has great promise to enhance vehicle safety. The objectives of this research were (1) to estimate the effectiveness of ESC in reducing the number of rollover crashes and (2) to identify cases in which ESC did not prevent the rollover to potentially advance additional ESC development. All passenger vehicles and light trucks and vans that experienced a rollover from 2006 to 2015 in the National Automotive Sampling System Crashworthiness Database System (NASS/CDS) were analyzed. Each rollover was assigned a crash scenario based on the crash type, pre-crash maneuver, and pre-crash events.

Vehicle body movements that occur during cornering have a strong influence on the evaluation of ride and handling. As a first step, we analyze subjective comments from trained drivers and find that the sense of vision played a major part in cornering feel. As a result of quantitative evaluations, we hypothesize that smaller time lag between roll angle and pitch angle made cornering feel better. We perform a human sensitivity evaluation, which confirmed this hypothesis. Given this result, we derive analytical equations for the roll center kinematics and the damping characteristics, in order to find a theoretical condition for the time lag of 0sec (giving a good cornering feel). We verify this by experiment.

We adopted the active hydropneumatic suspension and the dual-mode 4WS system for the 1989 Toyota CELICA. The active control suspension system detects the vehicle state with various sensors to control the oil pressure in the hydraulic cylinder with the linear pressure control valve; controlling attitude, ride comfort, stability & controllability and three-level vehicle height. The 4WS system continuously changes the steering angle ratio between the front and rear wheel according to the vehicle speed, decreasing the minimum turning radius at a low speed by 0.5 m and improving the controllability at a medium speed and the stability at a high speed. In addition, we further improved the performance of each system by integrally controlling the active control suspension system and the 4WS system. Thus, we succeeded in improving the total performance of vehicle dynamics by adding ABS to these systems to control the vertical, lateral and longitudinal accelerations.

The authors have developed an intelligent four-wheel drive system (I-4WD) designed to distribute the driving force to the front and rear wheels at the optimum ratio according to the running condition of the vehicle. The I-4WD consists of a center differential which distributes 30 percent of the driving force to front wheels and 70 percent to rear wheels (30:70), a hydraulic multi-disk clutch, an electronic control unit and a hydraulic control circuit. The driving force distribution can be steplessly varied from 30:70 up to the rigid state by controlling the hydraulic pressure on the clutch. The main control algorithm is based on the“yaw velocity model following control.” This composition has allowed us to accurately balance the cornering performance and stability without spoiling the critical limit predictability which is that the driver knows in advance the critical limit of vehicle dynamics.