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An active suspension system controls a spring constant and an attenuater in real time using a power supply. Generally, the hydraulic pressures are used for transmitting the power. Therefore, a highly reliable and inexpensive control system has been required for a commercial use. This has been achieved by developing a mechanical fluid servo valve which comprises a simple combination of a solenoid valve and a spool valve. The technical problem of the valve vibrations has been solved through the numerical analyses, the fluid flow visualization tests and the vehicle tests.

This paper describes the investigation into the contact pressure and incidental deformation on the contact surface of the piston skirt which comes in contact with the cylinder bore in operation. Focused on the single piston static tests in the first place, relationship between the contact pressure on said skirt and the strains developed inside the skirt, and the relationship between the deformation of skirt face and the strains inside the skirt were studied. Then, the dynamic contact pressure onto the skirt in operation and the amount of deformation were calculated based on the relationships mentioned above using the factor of dynamic strains measured on an engine in operation. The deformation of skirt calculated using said dynamic strains was verified by the direct measurement of the skirt deformation. It was demonstrated that the thrust side of a piston skirt was largely deformed due to enlarged contact pressure caused by the piston slap subsequent to firing top dead center.

This paper reports that estimation accuracy of suspension stroke velocity is increased by considering the damping force delay characteristics to an observer. Thereby ride comfort is improved, using the simple and low-cost semi active suspension systems that use only three vertical acceleration sensors.

This paper reports the results of a study into a preview control that uses the displacement of the road surface in front of the vehicle to improve for front and rear actuator responsiveness delays, as well as delays due to calculation, communication, and the like. This study also examined the effect of a preview control using the eActive3 electric active suspension system, which is capable of controlling the roll, pitch, and warp modes of vehicle motion.

In this paper, we discuss vehicle directional stability and introduce advanced stability control (ASTC) to stabilize the vehicle during severe cornering. Vehicle behavior in a transient steering condition during severe cornering was analyzed by computer simulation. It was found that applying an external yaw moment makes the vehicle more stable. The effect of controlling the brake force response is also evaluated by simulation to determine the brake actuator response criteria. The actual vehicle test was performed with a pylon slalom using a hydraulic brake actuator. It is verified that the ASTC stabilizes the vehicle for transient steering maneuvers.

It is well known that the self-aligning torque decreases before lateral force is saturated. Focusing on this self-aligning torque change, an estimation method has been developed to detect the friction condition between steered wheels and road surface before the lateral force reaches the friction limit. The lateral grip margin (LGM) is defined based on the self-aligning torque change, which is obtained using the EPS torque and motor current information. The LGM is theoretically analyzed based on the tire model and experimentally verified through the full-scale vehicle test. Moreover, the estimated LGM is applied for the chassis control systems to improve the vehicle dynamics performance.

A new variable displacement pump has been developed. This pump can variably change its discharged flow rate in accordance with the revolution changes of an automotive engine from idling engine speed to 6000rpm. It can quickly discharge oil necessary for controlling the autmotive active suspension system. This pump is of a swash plate, axial piston type which controls optimal fluid flow in time by using a pressure sensing control valve. Further, in order to improve the quietness in the vehicle system, the pulsation of the pump pressure was reduced and this pump's utility was realized for automobile use. This is a report on how the pump was introduced for commercial automobile use.

Drive train components (transmission, differential gears, etc.) can be made smaller and lighter if the excessive torque exerted on them can be reduced during the quick start of a vehicle. An orifice put in the hydraulic clutch piping path is an effective method. However, increased oil viscosity at low temperatures (0°C or below) makes the “pedal feel” worse. In order to increase the orifice diameter for better “pedal feel”, a shape memory alloy spring, for operation at low temperatures, was developed by adding cobalt to the nickel-titanium alloy. Consequently, a Variable-Orifice valve, using the shape memory alloy spring, is practical.

As a process that enables the high-speed and continuous forming of lengthy materials with a constant cross-sectional configuration, roll forming offers much higher productivity than the stamping process. However, in case a change must be made to the shape of the cross section, the material must normally be stamped or joined with a part containing a separate shape. This affects productivity, increases the number of pieces, and degrades the material's appearance. This report describes the roll-forming technology that we developed, in which the cross section of the material can be changed gradually. This method adopts a system which uses a movable and rotatable roll-stand that enables high-speed, continuous roll-forming processes.

Rear steering system can improve vehicle stability using active control of the rear wheel angles. For designing the rear steering system, environmental conditions, performance deterioration due to aging and component variation as a result of manufacturing tolerance under mass production must be taken into consideration. We have applied two-degree-of-freedom (2DOF) feedback control with feedforward control for the motor servo control so that the rear steering actuator can track the target rear steering angle accurately and stably. The control system is designed based upon a nominal mathematical model and its variation range. As a result, the rear steering actuator can be controlled with excellent performance and high reliability. This paper describes the mathematical model construction in the frequency domain and a robust motor servo controller design based on 2DOF feedback control with feedforward control.

Sport Utility Vehicles (SUV) and light duty trucks have gained in popularity for the last several years and the demand for more car-like behavior has increased, accordingly. Two areas for potential improvement are vehicle stability and maneuverability while parking. 4WS (4 wheel steering system) is known as an effective solution to stability and low speed maneuverability. In this paper, we identify a new systematic design method of two degree of freedom vehicle state feedback control algorithm that can improve vehicle stability, and show its control effects for a SUV with trailer towing. Low speed maneuvering is improved when the rear tires are steered in negative phase relative to the front tires. However with a large rear steer angle at low speed, the vehicle's rear overhang tracks a wider swing-out path than a 2WS vehicle. For this concern, we propose a new swing-out reduction control algorithm.