Communications: directive radio wave systems and devices (e.g. – Return signal controls external device – Radar mounted on and controls land vehicle
Patent
1990-06-29
1991-09-03
Barron, Jr., Gilberto
Communications: directive radio wave systems and devices (e.g.,
Return signal controls external device
Radar mounted on and controls land vehicle
342129, 342146, 342176, 367111, 367909, 340904, G01S 1393, G01S 1348
Patent
active
050458566
DESCRIPTION:
BRIEF SUMMARY
To drive a vehicle in the fog with scarce visibility, it is not sufficient that only the presence of obstacle or free way before the vehicle be indicated or displayed, not even if such indication is completed with information as to the minimum distance between the obstacles and the vehicle. It is necessary to know their location with as much detail as possible, so as to take proper decisions in respect of the maneuvers to perform, particularly in proximity to right hand or left hand curves or when a preceding too slow vehicle is to be overtaken.
It is an object of this invention to supply the driver of the vehicle with such additional information. This object is achieved by detailedly displaying the whole geometry of the plan space in front of the vehicle by means of a bidimensional illuminated dial consisting for instance of a matrix or array of luminous spots or cells arranged in rows and columns that simulate the plan space in front of the vehicle and to give a symbolic representation of any obstacle by emitting for instance red or green light when an obstacle is present or it is not present, respectively, in front of the vehicle. Such a dial could be arranged in the dashboard of the vehicle; it could also be of the so-called head-up display kind in which a luminous image of the dial is projected onto the windscreen so as to enable the driver to look at it while he attempts to look at the road.
In other words, the problem s to measure the coordinates of an obstacle. We shall use polar coordinates. Referring to FIG. 3, under the term distance (between the vehicle and the obstacle) the length of the radial vector R=OH is meant and, under the term declination, the angle Z formed between the radial vector R and the vertical axis y is meant.
The length of R can be derived from the measure of the time t required by an electromagnetic radiation to propagate from the antenna located in 0 to the obstacle H and to return back to 0 upon reflection from the obstacle H. Assuming that the propagation velocity is c, we get
If an obstacle placed at a distance R and at an angle Z is to be revealed, we may use n microwave slightly divergent beams irradiated by small stationary antennas, so as to enable to explore 2n-1 area sectors, as shown for instance in FIG. 2, where n=3. In FIG. 2, five angular sectors can be distinguished for an approximate evaluation of angle Z: in fact, it can be observed in FIG. 2 that if an obstacle is located for instance in the center line of sector B, it will be detected only by the beam B; if it is located at an intermediate position, for instance, in overlap sector A+B, it will be deflected both by beam A and by beam B.
Even if this operation way, that can be defined as an "amplitude discrimination", appears to be analogous to a monopulse radar operation way as already adopted in automatic tracking systems, in effect it is quite different. In fact, such already used systems are effective when there is one only target to be detected, but they become less efficient when the targets to be detected are more than one, especially when such targets are equidistant from the radar and are clustered.
It is therefore an object of this invention to detect and indicate any and each obstacle existing in front of a vehicle, with a satisfactory accuracy for most practical obstacle patterns.
The most difficult obstacle patterns to be accurately detected and indicated are those having multiple obstacles, all aligned at the same distance R from the antennas; also in this circumstance it is the aim of this invention to supply sufficient information for safely driving the vehicle, only with the exception of some very particular cases, that, anyway, do not reduce the overall safety offered by this system.
The principles upon which this invention is based are as follows. Let us suppose, for simplicity sake, n=3, as in FIG. 2: the three beams belong to the three antennas A, B and C, that can operate both as transmitting and as receiving antennas and are connected, therefore, to respective transmitters and receiver
REFERENCES:
patent: 3659293 (1972-04-01), Gupta
patent: 3855594 (1974-12-01), Botcherby
patent: 4349823 (1982-09-01), Tagami et al.
patent: 4467313 (1984-08-01), Yoshino et al.
patent: 4674073 (1987-06-01), Naruse
Mayhan et al., "A Two-Frequency Radar for Vehicle Automatic Lateral Control"; IEEE Trans. on Vehicular Tech., vol. VT-31; No. 1, Feb. 82, pp. 32-39.
Merlo, "Automotive Radar for the Prevention of Collisions"; IEEE Trans. on IECI; vol. IECI-11, No. 1, Feb. 64.
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