SYSTEM FOR AVOIDING COLLISION OF VEHICLES IN LOW VISIBILITY CONDITIONS

Abstract: the present invention concerns a system for avoiding collision of vehicles in low visibility conditions. This system comprises essentially: a passive detection system installed on board a vehicle (10) and based on smart infrared sensors (1 and 1'), detecting even minimum temperature gradients (less than 0.1 DEG C) within the field of view of said sensors; and an active system, co-operating with said passive system, based on a plurality of transmitters (2, 2', 2",... ; 2bis, 2'bis, 2"bis,... ) and receivers (3, 3', 3",...; 3bis, 3'bis, 3"bis,...) also operating in the infrared spectrum and installed on the sides of the road, for example on the guard-rails, in the locations normally used for reflectors. This invention can be classified in the technical field of signalling for traffic monitoring systems and in the application field of road safety in low visibility condition or in presence of dangerous obstacles.

Description: Description System for avoiding collision of vehicles in low visibility conditions Technical Field The present invention concerns a system for preventing the collision of vehicles of any type in low visibility conditions. The invention can be classified in the technical field of signalling for traffic monitoring systems and in the application field of road safety in low visibility conditions or in presence of dangerous obstacles. Background Art In the present state of the art, the problem of low visibility, mainly caused by thick fog, has been the subject of several proposals of solution, more or less effective according to the technology chosen. In particular, the solutions proposed till now can be classified in two major groups: 1. one group including systems installed on board the vehicles; and 2. another group including external monitoring systems able to alarm or even to automatically guide vehicles on the road, which has recently lead to a proposal for automation on moving guided platforms, which displace the vehicles on a highway on conveyer belts. The first group, that provides assisted driving by means of systems on board, can be divided in two subgroups, one of which is based on active technologies and the other is based on passive technologies. The subgroup based on passive technologies makes use of infrared vision, i.e., thermal viewers providing a better visibility in difficult conditions, such as not very thick fog, thanks to the better penetration of the infrared radiation compared to the one of visible spectrum. These devices have a low effectiveness/cost ratio, due to the very high cost of the thermal imaging viewers, that can provide an high resolution image, but have the same price of a small-medium car. The subgroup based on active technologies includes essentially the electro- optical technologies, which are systems emitting short laser pulses in the infrared spectrum that act as an optical radar, in which the signal generated and back- scattered from the target is detected by a sensor that measures its shape and time of arrival, and then measures the speed and distance of the target. These technologies are used in two ways: (a) active techniques with laser pulses in the near infrared, that do not allow long detection distances in case of very thick fog, and also suffer from jamming of the radar when the vehicle equipped with this apparatus crosses other vehicles equipped with the same alarm active system; (b) techniques based on the use of small radar systems installed on board the vehicle. These radar systems emit a pulse usually at a very high frequency (about 60-90 GHz), that hits the obstacles and is detected as a back-scattered signal, and therefore detects the presence of an obstacle and measures its distance. The disadvantages of such a solution are both the difficulty of installing equipment with high performance and low cost, and the fact that such an instrument, if installed on every vehicle, would create a saturation of the zone crossed by the vehicles generating electromagnetic signals of very high density, mainly the vehicles driving in the same line and in the opposite direction with respect to the vehicle considered. These vehicles would not only create problems of incompatibility, but also cause a heavy jamming of the detector and the receiver installed on board the vehicle considered, giving rise to discrimination problems between real and false alarms. Disclosure of Invention The invention described here is able to overcome the typical limitations of the techniques described above and consists essentially in a co-operative road- vehicle system for the detection of obstacles, that can be installed at a low cost and with a very high efficiency on the sides of a motorway. This system includes a very simple passive infrared sensor with a few sensing elements (about one hundred), lower in size by three orders of magnitude than the thermo-cameras as to the number of pixels, that at present, thanks to the technology of microbolometers operating at room temperature, has an affordable cost and can therefore be suitable for every kind of vehicles, especially for cars. This sensor does not provide an image (which might distract the driver attention); it provides an alarm indicating the presence of an obstacle on the road. This is possible because this sensor performs a differential measurement of the temperature on the road sides (which in case of a motorway are clearly distinguishable, thanks to the metallic guard-rails that obviously have a lower temperature compared to the temperature of any possible obstacle) and the thermal distribution on the road delimited by the borders. The presence of a possible obstacle on the road is therefore detected by the thermal radiation emitted by a warmer object on the road. This mechanism offers the advantage of a very high ability to discriminate the objects detected by the sensor. In particular, the vehicles going ahead are easily distinguishable because of the high temperatures of their exhaust pipes. The sensor therefore detects some signals which differ from the signals emitted by the other cold zones of the road. The present system includes not only the sensor installed on the vehicle, but also small infrared emitters installed on the guard-rails, exactly in the same locations were now reflectors are placed. These emitters are essentially elements warmed up at a very low cost, directly powered by the electrical power line (for instance, AC 220V, 50 Hz). These emitters can be detected directly and synchronously by the sensor installed on board a vehicle. For this purpose, two little receivers, of the same type as the sensor above described, are installed on the vehicle, inside the headlights of the vehicle itself. These receivers, designed in an appropriate way, are the focalising antenna of the vehicle in the infrared spectrum. The invention described here makes it possible to detect electromagnetic sources that are easily recognisable by the on board receivers and that have a signal intensity many times higher than the intensity of the background signal. This happens because such sources are detected in the infrared in a modulated way, even if the emission of the single emitters is relatively small (less than a few watts). Moreover, the present invention provides a system network operating along the whole road. For this purpose, receivers are also installed on each transmitting site, each receiver controlling several (for instance, three) corresponding transmitters placed on the other side of the road, and detecting if necessary the presence of each obstacle between every single receiver and the corresponding transmitter. This detection of obstacles on the road is shown by a sound and light signalling, receivable by all vehicles present in the action range of the signal, even those that have no infrared alarm system mounted on board. The drivers of those vehicles can in this way slow down and avoid collision. The system described here is completely new, compared to those made available by the present state of the art, since it comprises: • an on-board system having a very low degree of complexity but a very high level of specialisation (there are few sensors, about one hundred, compared to the more than one hundred thousand in a thermal imager, with consequent decrease in terms of cost, and increase in terms of sensibility, since the sensors of the invention described here automatically work as detectors of a difference of temperature, and therefore have a higher discriminating capability compared to a diffused and not well defined image, that can also be obtained in the infrared even in case of fog); • a road system co-operating with the on-board system mentioned above, which is a decisive element for the very high capability of detecting obstacles and for the very low possibility of false alarm; this road system operates with a structure of transmitters and receivers distributed along the entire network, that have an independent ability to detect the presence of obstacles and therefore to emit a local alarm signal. The result is a remarkable driving ability, as that nowadays made available in airports, but with the advantage of using transmitters that, since they operate in the infrared and not in the visible spectrum, have a greater penetration in the fog, and can also be modulated and therefore regulated, with a consequent high advantage in terms of signal/noise ratio compared to signals of continuous type. The invention is now described referring to the figures enclosed, in order to illustrate the configuration preferred at present by the inventor. Nevertheless the invention may also be realised in different ways, without modifying the basic concepts. List of figures: Fig. 1 shows two intelligent sensors 1 and 1' and telemeter 20 installed on a vehicle 10, of which only the frontal part is represented. This figure also shows the transmitters 2, 2', 2",... and the receivers 3, 3', 3",... installed on the left side of the road 12 and the corresponding transmitters 2b, s , 2'bis, 2"bis,... and the receivers 3bi S , 3'bis, 3"bi s ,... installed on the right side of the road. The same figure also shows an obstacle 11 that may be present on the road. Fig. 2 shows in particular the front part of vehicle 10 and the locations where the two intelligent sensors 1 and 1' and the telemeter 20 are installed. Fig. 3 is a block diagram that shows the processing of two signals Ii and It', received respectively by sensor 1 and sensor 1', from the moment of their reception to the moment when an alarm signal is emitted in the event of obstacles present on the road. Fig. 4 is a block diagram that shows the processing of the infrared signals emitted by the transmitters 2, 2', 2",...; 2 D j s , 2'bi S , 2"b ls installed on the two roadside guard- rails and of the infrared signals emitted naturally by any other object which may be present in the ambient. It is to be borne in mind that the invention described here can work, but at lower level of performance, by only using the equipment installed on the vehicle, in absence of transmitters 2, 2', 2",...; 2bi S , 2'bis, 2' .- and receivers 3, 3', 3",...; 3bis, 3'bis, 3" b is,... installed on the road sides. The mode of working of the present invention is clearly described in the characterising part of claim 1. The dependent claims show other useful characteristics of the invention.

Claims: CLAIMS 1. A system for preventing collision of any type of vehicle (10), be it aerial, terrestrial or naval, in conditions of low visibility, said system comprising essentially a primary passive system of detection installed on said vehicle (10) and based on intelligent sensors also called "smart sensors" (1 and 1') operating in the infrared spectrum, characterised in that said intelligent sensors (1 and 1') are able to receive and detect the natural electromagnetic radiation emitted by any obstacle (11), since said intelligent sensors can perceive even minimum temperature gradients (less than 0.1°C) produced by a variation of the electromagnetic emissions in their space distribution. 2. The system claimed in claim 1, characterised in that said system can actuate, only in case of a pre-alarm caused by the detection of an obstacle (11), an active telemeter (20) that sends electromagnetic pulses (radar or electro- optical) able to measure the distance between said vehicle (10) and said obstacle (11). 3. The system claimed in claim 1 or in claim 2, characterised by the fact of using, to support the alarm functions performed by said primary passive system, also a secondary active system of optical type, co-operating with said primary passive system, that enlightens the route of said vehicle (10), detecting and signalling any kind of obstacle (1 1) that may be located on the road. 4. The system claimed in claim 1, said system comprising, in addition to said primary passive detection system installed on board said vehicle (10), also an active system, co-operating with said primary passive system, based on a plurality of transmitters (2, 2', 2",... ; 2 b i s , 2' b i 8 , 2" b , s ,...) and receivers (3, 3', 3",... ; 3bis, 3'bis, 3"bi s ,...) also operating in the infrared spectrum and installed on the roadsides, for instance in the locations used at present for the reflectors, said active system providing support to said primary passive system installed on board the vehicle; characterised in that said active system emits, by means of said transmitters (2, 2', 2",... ; 2bis, 2'bis, 2"bj s ,...), infrared signals that are received by said sensors (1 and 1'), thus supplying the driver with information that define the edges of the road, and by said receivers (3, 3', 3",...; 3bis, 3'bis, 3"bis,...) thus supplying an acoustic and/or visible alarm in case any obstacle (11) is present between said receivers and the corresponding transmitters installed on the opposite side of the road. 5. The system claimed in claim 4, characterised in that said sensors (1 and 1'), in case they perceive an alarm, can activate an active telemeter (20), of radar type or of laser range finder type, which is installed on said vehicle (10), to obtain a confirmation of the received alarm and also to obtain a measurement of the distance between the obstacle detected (11) and the vehicle (10). 6. The system claimed in claim 4 or in claim 5, characterised in that said system can be either totally passive, as claimed in claim 4, or integrated with an active telemeter measurement supplied by said telemeter (20), as claimed in claim 5, but in the latter case said active telemeter measurement is performed in a very short time, of the order of magnitude of some milliseconds, in case an alarm from said sensors (1 and 1') has been perceived, practically eliminating the risk of jamming for said sensors (1 and 1') owing to electromagnetic radiation coming from said active telemeter (20).

Inventors: CORSI CARLO, CORSI, CARLO
Applicants: CONSORZIO C R E O CENTRO RICER, CORSI CARLO, CONSORZIO C.R.E.O. - CENTRO RICERCHE ELETTRO OTTICHE, CORSI, CARLO
Application year: 1999
Main classification: G08G1
IPC codes: G08G1