- 1. Research Items and Research Flow
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In 1997, principal user services that should be developed by AHS were picked out based on user and social needs. Requirements sought from user services were then set, and a logic architecture was designed for designing the AHS system.
Fig. 1 shows the research flow.
Fig. 1
- 2. Setting Principal User Services
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To maintain the universality of user services, 19 principal user services related to safety, efficiency, and environment were established for each vehicle moving direction, namely longitudinal, lateral, and at intersections. Table 1 shows the 9 principal user services related to improving safety.
| Action |
Principal user services |
Service definition (summary) |
Lateral
movements |
Maintaining safe headway |
To maintain distances with the preceding
vehicle to avoid front end collisions |
Preventing collisions
with obstacles |
To prevent collision with stationary obstacles on
cars, and fallen objects |
Longitudinal
movements |
Keeping lanes(straight ahead) |
To maintain lanes on straight roads
the path of the vehicle such as pedestrians, parked |
| Keeping lanes(curves) |
To maintain lanes on curved roads |
| Safe lane changes |
To avoid collisions with other vehicles
when changing lanes |
| Intersections |
Preventing crossing collisions
at intersections |
To prevent crossing collisions at intersections |
| Preventing right turn collisions |
To prevent collisions when making right turns |
| Preventing left turn collisions |
|
Preventing collisions with
crossing pedestrians |
To prevent collisions with pedestrians crossing streets
To prevent collisions when making left turns |
Preventing collisions at
railroad crossings |
To prevent collisions with trains at railroad crossings |
- 3. Setting Principal Requirements
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We set the requirements expected of principal user services such as operational environment, function, and performance. Especially for requirements on performance, they have been quantified using mathematical models on vehicular movements. Below is one of the examples of requirements.
Fig. 2 shows the image of "lane keeping (curve)" service. This service requirement warns the driver to reduce the speed of the vehicle from 50 km/h to 25 km/h 50 m prior to entering a curve with a radius of approximately 50 m on a snowy road surface.
Fig. 2
- 4. Designing the Logical Architecture
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According to the steps shown in Fig. 3, we designed the logical architecture. We have organized the function elements demanded of the principal user services and classified them into the three types of recognition, decisions, and motion. Furthermore, using these function elements, we designed the system's basic structure called system models. Implementing logical design centered on system action definitions and function composition in order to realize principal user services that can appropriately be applied to all.
Fig. 3
- 5. Future Tasks and Research for 1998
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In fiscal 1997, in quantifying requirements, we conducted quantification under the condition that accident rates are expected to be high. But for fiscal 1998, we plan to further detail quantification based on even more detailed accident analysis.
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