Communications: directive radio wave systems and devices (e.g. – Return signal controls external device – Radar mounted on and controls land vehicle
Patent
1996-12-06
1998-07-28
Sotomayor, John B.
Communications: directive radio wave systems and devices (e.g.,
Return signal controls external device
Radar mounted on and controls land vehicle
342107, 342146, G01S 1393, G01S 1360
Patent
active
057867879
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for determining the course of another vehicle in relation to one's own vehicle by measuring the position of the other vehicle in relation to one's own vehicle by a transmitter/receiver system, such as a radar system, including the following steps being carried out:
a) the position of the other vehicle is determined by position measurements,
b) on the basis of position measurements carried out in accordance with step a), the side location of the other vehicle and one's own vehicle is determined at a position where the other vehicle is level with one's own vehicle, by moving the front vehicle backwards in time and/or moving the rear vehicle forwards in time,
c) the side location at the position determined in accordance with step b) is compared with the side location of one's own vehicle, and
d) the difference in the side locations in accordance with step c) between one's own vehicle and the other vehicle is used as a measure of the discrepancy between the course of the other vehicle and the course of one's own vehicle.
BACKGROUND OF THE INVENTION
In order to increase road safety, intensive work is being carried out towards finding systems which improve safety. In this connection, it has been proposed, among other things, to use radar technology in cars, so-called car radar. In a cruise control system, the car radar can help the driver to keep a sufficient distance from the vehicle in front, can warn of vehicles approaching from behind, and, in a further perspective, can form part of a more general collision-prevention system. One problem in this connection is that of determining the course of the cars in front. Straight sections ahead can be monitored relatively easily. The problems become greater when a vehicle in front is going into and following a bend. The system should be able to follow the vehicle regardless of the curvature of the road. A method of the type mentioned in the first paragraph of the description is already known from the U.S. Pat. No. 5,249,157.
For use in cruise control systems, it is important that the system also functions when the distance in relation to the vehicle in front remains constant, i.e. when the closing speed=0, and in situations with short increasing distances. The method according to the cited U.S. Pat. No. 5,249,157 crucially makes use of prediction of the "intercept time" as determined by the ratio between the distance separating the vehicles and the closing speed. A disadvantage of this known method is that the "intercept time" cannot be determined when the closing speed is zero, which is a common situation with cruise control systems.
A study of the road network shows that, over large parts of their length, the majority of roads can be approximated with great accuracy to straight and circular segments. Bends which do not have circular segments are considered awkward to negotiate, since the driver's handling of the steering wheel has to be corrected through the bend, and they are therefore uncommon. A circular bend segment can be defined in a known manner as having a constant center of curvature and a constant radius of curvature. By contrast, other parts of the road, including straight segments, cannot be defined in this way.
The curvature of a bend is a measure of the rate at which the tangent vector changes direction. The curvature is therefore expressed by second derivatives (accelerations), where transversal accelerations (angular accelerations and magnitudes derived therefrom) are especially important. Angular accelerations determined from angle measurements are generally very noisy signals. This is especially the case if radar sensors are used. In the method according to the U.S. patent referred to above, the angular acceleration is determined in accordance with the above as a second derivative. Consequently, advantageous methods for course determination should function on curving roads, and yet not use angular accelerations, and, taking into consideration non-circular road sections, including
REFERENCES:
patent: 5249157 (1993-09-01), Taylor
patent: 5321407 (1994-06-01), Kikuchi et al.
patent: 5343206 (1994-08-01), Ansaldi et al.
patent: 5375336 (1994-12-01), Nakamura
patent: 5534870 (1996-07-01), Avignon et al.
Struik, Differential Geometry, Addison-Wesley 1950, p. 201.
Eriksson Lars
Tullsson Bert-Eric
Celsiustech Electronics AB
Sotomayor John B.
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