DE3222263A1 - Distance warning system for motor vehicles - Google Patents

Abstract

A distance warning system for motor vehicles in road traffic, comprising a radar system and an analysis computer and the known methods for distance measuring and for evaluating the measurement results as a technical basis. In addition, the system tracks in a separate operating mode only the echo signals originating from vehicles moving in the forward area. The purpose of this selection is to eliminate false alarms in complex traffic situations (such as occur mainly in busy city traffic and on country roads with many curves). This can be optionally combined with the conventional monitoring mode (for simple straight-ahead driving or for long-distance rapid traffic). If necessary, switching between the two operating modes is automatic as a function of the respective driving situation, which is primarily the result of one's own speed, the steering angle and the status of the flashers. The warning system can be used without external prerequisites and is autonomous to this extent. On the other hand, it can also be operated as a part of a spacing control system.

Description

description

The invention relates to a distance warning system for motor vehicles according to the preamble of claim 1.

Such warning systems, with the purpose of rear-end collisions in road traffic through timely warning of the driver or, moreover, through automatic It is known and partly to avoid reducing one's own speed in the experimental stage for several years.

The technical basis of these systems is essentially a radar system with transmitter and receiver that works according to the reflection principle and with help an electronic evaluation system to measure the distance or the relative speed to the location objects, i.e. to possible obstacles on the roadway.

In principle, both a pulse radar and a Si continuous wave radar are used for this suitable.

A pulse radar creates a dense series of short, discrete wave packets emitted and, if reflected, received, the echo signals in detail (with the time difference between their arrival) directly the distance information result, while the relative speed based on the change in distance in time can be calculated.

(See "Spectrum of Science", 6/80, pages 24-34) With one continuous radiating BE-CW radar can determine the distance with the help of a suitable frequency modulation, e.g. sawtooth-shaped.

The relative speed to the located objects can be determined here can be derived directly from the Doppler frequency shift.

(See e.g. DT 25 14 868 Al, DT 24 60 826 Al) Both methods have advantages and disadvantages, they are currently in various practical designs tested. However, both methods have one significant shortcoming in common, which is caused by all known test results are confirmed: Neither can you drive in the direction of travel with the Doppler effect nor with any electronic evaluation from a Echo signal sequence alone can be safely distinguished from a dangerous one Obstacle or e.g. originates from the stationary traffic scene; and from this fundamental Deficiency results in the relatively high false alarm rate of self-sufficient distance warning systems According to the state of the art.

Non-self-sufficient warning systems solve this problem simply by the fact that they use special aids located outside the monitoring vehicle, i.e. already require - e.g. special reflectors on vehicles in front, possibly with subsequent modulation of the radar waves etc. Their disadvantage is generally there depending on an external technical facility with the various Consequential disadvantages.

A special version of a non-self-sufficient warning system without false alarms is based on, for example, not the traffic in front but the traffic behind to monitor and with the help of the Doppler effect the approaching or Vehicles that are driving too closely (i.e. threatening) from other traffic and from the to distinguish resting environment.

(See US 3 786 507) In this case, the functionality of the System depends on the readiness of the following driver, the warning signal if necessary to be observed, and on the other hand it protects in the direction of travel - indirectly - only then, if a car with the same system drives ahead or stops facing straight ahead, even in an accident.

Autonomous distance warning systems, on the other hand, have the advantage of the occupants to protect the monitored vehicle directly, regardless of external Aids and thus also independent of the general implementation status of the respective Systems.

Reducing the false positive rate of these systems is a goal that has already been sought in a variety of ways. As it is with the known means However, in principle it is impossible to generate false positives with complete monitoring of the To exclude the advance space completely, each of these attempts can only consist of limit the surveillance area in a certain way in order to reduce false alarms to obtain.

Above all, the field of action of the radar lobe is restricted, once in the localization depth (at approx. 120m) and also in the radiation angle (at approx. 20).

The radiation angle can be influenced by antenna size and Frequency. A special type of bundling is created by superimposing two similar Radar lobes and achieved by a suitable evaluation of the echo signals.

(P. DT 2 327 186) By shortening the monitored space more distant obstacles, however, only recorded later; and the bundling of the radar waves emitted results in the restriction that vehicles ahead - especially in curves - temporarily got out of the surveillance area, although the distance to them may be too small.

This applies to a greater extent to a combination of these two restrictions, namely for a shortening of the evaluated measuring distance depending on the steering angle, with the purpose of reducing false alarms from oncoming traffic or guard rails in curves.

(See "Spectrum of Science", 6/80, page 28) A Attempt to curve the surveillance space - while reducing the false alarm rate - largely to get is that the radar system is synchronized with the steering movements is pivoted in the direction of the road.

Apart from the different technical complexity of the two processes, However, there are driving situations in which both are equally - and undiminished - lead to a false alarm, especially when there is heavy oncoming traffic: e.g. in the entrance of curves (as long as the wheels are straight ahead) and in the middle of changing lanes (where the Also guide the wheels temporarily straight ahead).

Such situations, combined with relatively narrow lanes, occur most often on country roads and in city traffic; and considering the negative, downright dangerous effect of every false alarm is for everyone so far known self-sufficient distance warning systems to be expected that their scope of application long-range express traffic will remain limited. For complex road traffic (where the highest accident frequency exists) still exists according to the state of the art no stand-alone solution.

The object of the invention is to provide an autarkic distance warning system to design that for both simple and complex road traffic is suitable, especially in critical traffic situations without false alarms is working.

This task is based on conventional, generic Devices solved by the characterizing features of claim 1.

The system-related, necessary for switching off the command alarm There is a limitation of the monitoring framework here - depending on the situation - in the consequent restriction to the monitoring of the distance to vehicles moving ahead, i.e. by consistently refraining from signaling other objects. (The conventional methods give general warnings, i.e. regardless of the respective Situation, also in front of oncoming traffic and standing obstacles, albeit in general too late, since the relative safety distance plus is the standard distance criterion a surcharge is selected - relative: i.e. in relation to a locating object moved ahead with its own braking distance.) The invention is based on the assumption that the free Space in width, in particular the road layout itself and this in particular at a lower speed, it is relatively easy to optically record and control can be (and must be recorded anyway) while the subjective assessment the distance or even the relative speed to vehicles in front - even with full attention - can only be very imprecise.

At higher speeds, e.g. greater than 80 km / h, especially on the wider lanes provided for this purpose, as well as, on the other hand, in slow traffic in columns, In congestion and traffic jams, however, it is useful and advantageous to stand Include obstacles in the surveillance framework of the distance radar and the motorist thus to support.

The advantage achieved with the invention is -according to the task - mainly in that rear-end collisions where they occur most frequently, namely in dense city traffic and on busy country roads can, the introduction and dissemination of the warning system without false alarms impaired - and without the advantages of conventional methods for their special area of application must be given up.

The distance monitoring of vehicles moving ahead according to claim 1 can if necessary also for itself - in a technically simplified, more cost-effective version - will be realized. In contrast, the bimodal version of the system requires apart from the two operating modes themselves, a clear regulation of their interplay, the respective operating status must always be clearly and easily recognizable.

According to the invention, these subtasks are identified by the characterizing Features of claims 2 to 4 solved.

A useful embodiment for the optical function display the warning system according to claim 2 consists in the (known) combination of the familiar Colors green, yellow, red with the assigned meaning: Green, i.e. the lane is free. " Yellow, i.e. critical distance has been reached: Do not accelerate! "Red, i.e. 'tAbstsud is too small: reduce speed! "The operating mode for selective monitoring vehicles in front are simply shown with an additional display, e.g. by means of a white light. The green display appears in this Operating mode only if a vehicle has been located at a sufficient distance drives ahead. If e.g.

this vehicle suddenly stops (outside the warning area), like this green goes out and the neutral function display remains for orientation.

The content of the actual 5wiarn messages yellow and red is the same in both operating modes.

According to the objective of supporting the driver without his To reduce responsibility, the two operating modes should not only be automatic, but also - and then with higher priority - can be switched manually (claim 3).

If the automatic switching of the operating modes is activated, then it is sufficient according to the invention, certain objective changes in the driving situation to the monitoring mode to adapt to the new situation. The driving situation itself can, in principle, consist of a few however, sufficient primary data can be derived for this, especially from the sizes Own speed, steering angle and indicator position.

Which change of these sizes under which condition is appropriate to which monitoring mode should lead can be determined in an advantageous embodiment Realize to claim 4 according to the following switching rules: A. Switching to the monitoring mode for complex road traffic, - if the steering angle is one stored as a parameter Exceeds the value (e.g. when maneuvering, turning or in tight bends) or - when the direction indicator is switched on (e.g. when turning, when overtaking or change lane).

B. Switching to the monitoring mode for simple straight-ahead driving or for high-speed traffic, - if the own speed is lower or exceeds an upper limit value stored as a parameter, during the The direction indicator is switched off (e.g. when approaching an intersection or after a traffic jam on the motorway), or - if the direction indicator jumps back to the rest position, while the airspeed (increased) is than the upper limit value (e.g. after entering the motorway or after a Changing lanes in high-speed traffic).

It should be noted that the switchover only occurs when the individual Limit values are applied, not also in the case of changes in the opposite direction.

The parameters in question can be specified in the following order of magnitude are: - Critical steering angle: 10-15 ° to the longitudinal axis, which corresponds to about one Third of the maximum wheel deflection on each side, - lower / upper speed limit: 20 or 80 km / h.

Fig. 1 shows the block diagram of a distance warning system according to Invention, in a bimodal form. It seeks to outline each Roughly map functional units and the data flow.

A radar system RA emits electromagnetic waves with a transmitter or pulse-shaped cell packets and receives those reflected by the objects to be tracked Echo signals with a receiver.

The information contained in the reflection (distance or change in distance in time) is processed with an analog-to-digital converter in digital Porm implemented and as input data El to the downstream microcomputer MC passed.

The microcomputer MC, consisting of an egg processor MP1-3, a Memory SP and input / output ports EA, processes the incoming data under Consideration of further input data E2-E6 and saved parameters with a corresponding program and thus continuously monitors the anteroom of Vehicle and its driving situation.

If this monitoring determines that the safety distance has been reached or fallen below, the microcomputer provides the corresponding output data A1-A4 to the alarm transmitter AG or to the functional unit for speed regulation VR, in each case after converting the signals into analog form.

The measured value converter MU prepares the input data E2-E6 with the Meaning: E2 = mode of operating mode selection (manual / automatic) E3 = weather conditions E4 = vehicle speed E5 = steering angle E6 = indicator position The warning message with the output data A1-A3 is graded, namely in the form: A1 = visual A2 = acoustic (limited) A3 = tactile (limited) The MP microprocessor is functional divided into a control section XP1 and the evaluation sections MP2 and MP3. The control part s1 contains i.a.

the device for evaluating the driving situation and the switching logic for the corresponding use of the two evaluation parts.

The part MP2 processes the input data according to the conventional distance Monitoring of all moving and stationary obstacles - and suppressed, as far as this is possible possible, false warnings by means of special program routines.

When activating the evaluation part MP3 (for complex road traffic, i.e. in the operating mode for selective monitoring) further possible sources for False alarms switched off with programmatic means, namely all those monitoring results that (compared to your own speed) can only come from stationary or oncoming traffic, so that the purpose the distance monitoring to vehicles moving ahead can be correctly fulfilled.

Fig. 2 shows a schematic representation of two vehicles F1 and F2 in situations (a) to (e) each with a different relative speed = = v2 - v1, where v1> 0 is the speed of the monitoring vehicle F1 is: a) F2 moves away in the direction of travel (na> E), b) F2 moves at the same speed ahead (dv = O), c) F2 moves ahead more slowly (#v <0 and # v + v1> 0), d) F2 stands in front of F1 (# v + v1 = 0), e) F2 meets Pl (tv + v1 <0).

Situation (a) leads to a reduction in the risk of collision and therefore does not give a warning message from the system. The other situations can, however lead to a collision and therefore result (if the calculated Safety distance) a warning message.

In the conventional monitoring mode, this applies to cases (b) to (e), in the selective monitoring mode of the system only for (b) and (c), namely then, if #v = 0, i.e. v1 = v2, or #v <0 and # v + v1> 0, i.e. v1> v2> 0, was determined. Selection criterion for tracking of location objects is here the condition v2> 0.

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Claims (4)

Distance warning system for electric vehicles Patent claims 1. Distance warning system for motor vehicles - with a radar system for measuring distance and relative speed of locating objects in the direction of travel of the monitored vehicle (as impulse or FM continuous wave radar, with the associated transmitting and receiving devices), - with an electronic evaluation system to determine the alarm status from the Echo signals taking into account other measured variables (e.g. Vehicle speed, steering angle, weather conditions) as well as specified, stored parameters (as a microcomputer with the associated process peripherals, e.g. amplifiers, potential traps, signal converters analog / digital and vice versa, as well as other required assemblies and switching elements), - with an alarm device, if the calculated safety distance to an obstacle is not reached is activated and the driver of the monitoring vehicle optically and / or acoustically or tactile (by means of vibrations via the accelerator pedal) warns - optionally with additional ones Warning devices (e.g. for following traffic) or regulating devices (e.g. for automatic speed adjustment), characterized in that that the system has special facilities for evaluating the echo signals and the own movement state, which a situation-dependent monitoring of Enable advance space, namely a) an electronically controlled filter device, which only allows such echo signal data to lead to a distance warning or regulation, those of vehicles in front at the same or lower speed (greater than zero), and optionally b) a bistable switching device, which automatically switches to one of two types of monitoring when the situation changes can switch, namely either to the selective monitoring identified in a) (for complex road traffic) or conventional distance monitoring all moving and stationary obstacles (for simple straight-ahead driving as well as for the extensive express traffic). 2. Distance warning system according to claim 1, characterized in that the driver of the monitored vehicle, functional status and monitoring result of the system at least by means of clear, easily distinguishable colored lights are displayed. 3. Distance warning system according to claim 1, characterized in that a switching device for manual selection when both operating modes are combined the 3 operating mode on the one hand and for automatic selection on the other is. 4. Distance warning system according to claim 1 and 3, characterized in that that the automatic switching of the operating modes is controlled by changes in the situation will result at least from changes in the machine-recorded values of the airspeed, Have the steering angle and indicator position derived.