Search Results

In recent decades, research and development in the field of autonomous vehicles have rapidly increased throughout the world, and autonomous driving technologies have begun to be applied to mass production vehicles. Especially recently, even affordable mass production vehicles have begun to be equipped with some autonomous driving systems such as a Lane Keeping Assist (LKA) system. In general, mass-produced LKA systems use a lane detection camera as a means of keeping the lane. One of the common limitations of camera-based LKA systems is that the lane keeping performance significantly decreases when the camera cannot detect lane markings for various reasons such as snow coverage or blurred lane markings. To overcome this limitation, we have developed Global Navigation Satellite System (GNSS)-based LKA systems, which are not affected by the surrounding environment such as weather and the condition of lane markings.

A fuel control method to reduce the harmful exhaust gas from SI engines is proposed. As is well known, both the amplitude and the frequency of the limit cycle in a conventional air-fuel ratio control system are determined uniquely by parameters in the system. And this limits our making full use of the oxygen storage effect of TWC. A simple model of TWC reaction revealed the relationship between maximum conversion efficiency and both the amplitude and the frequency in a air fuel control system. It also revealed that TWC conversion efficiency attained to maximum levels when both the amplitude and the frequency of the limit cycle are selected so as to make full use of the oxygen storage effect of TWC. In order to achieve this, it is necessary to vary both the amplitude and the frequency arbitrarily.

In this paper, we suggest a novel algorithm to distinguish semi-steady states from various steering patterns and to estimate the stability factor. The algorithm also estimates each stability factor in left and right turns because there could be a case where they differ based on uneven tire wear and so on. The stability factor, which is the turning characteristic of a vehicle, has been treated as constant for most vehicle control systems. However, in fact, it may change in some situations, for example when a vehicle is overloaded. So there is a chance that a driver may be aware of an unusual sensation when vehicle control is designed based on a constant stability factor. We have succeeded in developing an algorithm to estimate the stability factor accurately enough to be able to compensate for it and have confirmed the effectiveness of the algorithm by simulation and vehicle testing as well.

This paper presents a new motor current control strategy for Electric Power Steering (EPS) to reduce current fluctuation. Such current fluctuation may cause undesirable steering torque ripple and acoustic noise, if an inexpensive microprocessor is used. Using a DC-motor, current fluctuation associated with change in the battery voltage, etc., may occur. We have developed a new current control strategy which effectively alleviates current fluctuations of the motor without using higher performance microprocessors. The new controller is based on the estimation of disturbance voltage and compensation for this disturbance voltage. We have bench-tested the performance of this control strategy and confirmed that current fluctuation is reduced below that using conventional PI controller. The PI gain for the proposed controller is the same as that for the conventional controller.

Experimental investigations of fuel breakup very close to nozzle of practical high-pressure swirl injector, which is used in gasoline direct injection (GDI) engine, were carried out. In GDI engines, fuel is directly injected into cylinder therefore the spray characteristics and mixture formation are of primary importance. In this research, visualizations of primary spray formation process were demonstrated using a high-speed video camera (maximum speed: 1Mfps) with a long-distance microscope. Initial state and development of the spray were discussed under the different injection pressure condition. During the injection period, the length and thickness of the liquid sheet, which is produced from the nozzle exit, were measured using Ar-ion laser sheet and high-speed camera. Primary spray structure and behavior of liquid sheet, especially surface wave of liquid sheet, at nozzle exit were discussed using obtained images.

Vehicular collision avoidance radar systems using millimeter-wave have been developed in recent years. Because of their simple structures, a microstrip antenna or a lens antenna is often used as the radar antenna. However, the antenna efficiencies of these antennas are low, in general. Therefore, the types of antenna that have small antenna aperture are difficult to obtain high antenna gains. In addition, it is difficult to radiate many beams at narrow beam intervals with a lens antenna. We developed an offset paraboloidal reflector antenna (the OP antenna) for the vehicular collision avoidance radar. This antenna consists of one pyramidal horn antenna and one offset paraboloidal reflector. They pyramidal horn and the radio frequency unit (the RF unit) of the radar are fixed in the radar head. To scan the beam, only the reflector is rotated. Using a reflector-rotating mechanism, the OP antenna can radiate many beams toward different directions.

A small. low-cost piezoresistive acceleration sensor suitable for automotive applications such as advanced breaking control and suspension control systems has been developed. A piezoresistive semiconductor sensor has such advantages as high output linearity, long-term output repeatability and DC response a piezoelectric sensor doesn't feature. One drawback. however, is that piezoresistive characteristics are quite temperature sensitive: Such that temperature dependence of DC offset and span have to be compensated with a certain electrical circuit. With 1 mV/Vs/G, the low sensitivity of the acceleration sensor [Vs:bridge voltage. G:gravitational acceleration], the temperature shift of DC offset represented in terms of the sensitivity, becomes relatively high.

Recently, development of vehicle control system targeting Full Driving Automation (autonomous driving level 5) has advanced. Some applications of autonomous driving systems like the Lane Keeping Assist system (LKA) and Auto Lane Change system (ALC) (autonomous driving level 1-3) have been put on the market. However, the conventional system using information from front camera, it is difficult to operate in some situations. For example the road that no line, large curvature and number of lane increases or decreases. We propose an autonomous driving system using high accuracy vehicle position estimation technology and a high definition map. An LKA system calculates the target steering wheel angle based on both vehicle position information from the Global Navigation Satellite System (GNSS) and the target lane of high the definition map, according to the method of front gaze driver model. Then, the system controls steering the wheel angle by Electric Power Steering (EPS).

A robust cruise control system using a disturbance observer is proposed. A control design method based on the two-degree-of-freedom (2-DOF) control including a disturbance observer is introduced. The proposed controller provides that: (1) input command responses are not affected by driving condition, such as vehicle speed, and road gradient (2) input command response and disturbance suppression performance can be designed independently (3) choice of an appropriate parameter value in the disturbance observer depending on the throttle opening gives a proper trade-off between the robust performance and the robust stability over a wide driving range. Simulation and experimental results show that the proposed system is robust against both parameter variations and disturbances.

An SOI type pressure sensor has been developed which can measure pressure at high temperature environments above 150°C. SOI stands for Silicon On Insulator. A single-crystalline silicon layer is located on an insulating layer formed on a silicon substrate. The piezoresistors of the SOI type pressure sensor are made from the single-crystalline silicon layer which is isolated from the silicon substrate by the insulating layer. There is no leakage current from the piezoresistors. The SOI structure is made by the laser-recrystallization-method. The properties of the SOI type pressure senor are as good as conventional semiconductor pressure sensors.

A new automotive Mini Disc (MD) changer mechanism has been developed which fits a 1 DIN size chassis. This mechanism, mainly consisting of a disc change mechanism and an anti-vibration mechanism employing a floating disc drive unit system, offers a high vibration resistance, quick disc change capability and a size small enough to set a unit in an instrumental panel (I/P).

In this paper, an application of variable structure systems (VSS)(1) to electromagnetic-clutch (EMC) control for starting vehicles is studied. Using a conventional open-loop controller, there is the case that changes in EMC dynamics lead to undesirable vehicle vibration though it may be rare. First, to overcome the above problem, we developed a control strategy based on VSS. The VSS control is robust with respect to changes in EMC dynamics. Second, we discussed the chattering problem of this controller in application to actual vehicle control. Finally, we confirmed the validity of the proposed control strategy and the appropriateness of the conditions for reduced chattering derived by simulation. The validity of this control strategy was also confirmed experimentally.

This paper is concerned with a scan laser radar sensor used to measure distance. It s a basic component of a vehicle distance warning system or an intelligent cruise control system. An intelligent cruise control system requires not only the distance to the object, but also the ability to detect movement of the preceding vehicle and the existence of any other nearby obstacle. However conventional radar sensor mainly fixed beam technology and measure only distance. Therefore, it s insufficient for the application to an intelligent cruise control system. Our newly developed scan laser radar transmits an extreme narrow beam and scans both transmission direction and reception direction simultaneously at a high measurement time rate. This scan laser radar can measure the lateral position of objects with high accuracy and good reconstruction level.

In vehicle distance warning systems using fixed beam laser radar false alarms often occur on curved roads. To solve these problems, we attempted to detect the target vehicle correctly by using a scanning laser radar on curved roads. This scanning laser radar has the advantage that it is able to measure the distance and direction of obstacles on roads. In this paper, we explain the following three items. The first is the configuration of the experimental system which we developed. The second is the method of target vehicle detection by using reflectors located along roads. The third is the performance of this experimental system.

This paper proposes a vehicle state detection method for improving the stability of vehicles equipped with electric power steering (EPS) and electronic stability control (ESC) systems. ESC is an effective vehicle stability control system that operates within a vehicle's stability limitations. Generally ESC uses a vehicle state signal such as yaw rate. To enhance the ESC function so that it can alleviate understeer, a process that is capable of detecting understeer is required. This concept motivated us to develop a vehicle state detection algorithm based on estimated self-aligning torque using EPS. It is well known that maximum self-aligning torque occurs before maximum cornering force is reached. We have confirmed that the proposed algorithm can detect understeer earlier than conventional means based on vehicle yaw rate.

Compact cassette type tape players for car stereo are among the most popular of car audio equipment. To eliminate manual tape change at the end of each playing, a multi-function cassette player for vehicle use which can replace the cassette automatically has been made for trial. With some original mechanical functions and with two micro computers in the control system, the cassette player is made up into a very small unit. As audio equipment for vehicle use, this player offers a new concept.

A Vehicle Vibration Control System by Active Control has been developed. The experimental results using a 4-cylinder gasoline engine installed in a car showed that at the position of the driver's seat, the acceleration of the vibration was reduced by 16 dB. This system operates stably and at low cost because of having a feedforward system, so many applications can be expected in the near future as methods for vehicle vibration reduction.

A piezoresistive semiconductor pressure sensor that can be measure high pressure upto 3.5 Mpa within ±1% error of FS (Full Scale) has been developed; it is suitable for use in automotive electronic control systems such as suspension, transmission, anti-skid brakes and air conditioners. This pressure sensor has a silicon diaphragm in which piezoresistive elements are diffused and form a wheatstone bridge circuit to newly developed to achieve high accuracy. High resisting pressure of more than 10 MPa (300% of rated pressure) and high sensitivity of more than 100mV/V supply ·3.5 MPa were achieved by the optimum designe of diaphragm shape.

This paper proposes a new Electric Power Steering (EPS) control strategy that enables improvement to steering-wheel returnability. Using a conventional EPS controller, frictional loss torque in the steering mechanism reduces steering-wheel returnability, which drivers occasionally perceive as unpleasant. This phenomena occurs in any EPS system regardless of motor type or mounting location. To improve steering-wheel returnability for EPS-equipped vehicles, we developed a new control strategy based on estimation of alignment torque generated by tires and road surfaces. This proposed control strategy requires no supplemental sensors like steering-wheel angle or motor-angle sensors. We experimented with this proposed control algorithm using a test vehicle and confirmed that it enables improved steering wheel returnability and also better on-center feeling.

In JAPAN some ICCs (Intelligent Cruise Control systems) with recognition systems using Laser Radar have been produced since 1995. However these recognition systems have some improvement challenges; 1) Improvement of detectability for less reflective objects, 2) Improvement of identification performance of a vehicle to be tracked in the same lane (a target vehicle), 3) Improvement of detection performance under bad weather condition. We are developing a New Recognition System using sensitive Laser Radar with APD (Avalanche Photo Diode) as a solution for these challenges. In this paper, we will describe our experimental system using sensitive Laser Radar, especially, algorithm for target vehicle recognition and its performance.