publication number DE102010027647 (A1)
Release date: 2011-01-20
Inventor: STEPHEN Groitzsch [DE]; SCHORN Matthias [DE]; DANIEL FISCHER [DE]; STÖLZLE STEFAN [DE] + (Groitzsch, STEPHAN; SCHORN, MATTHIAS; FISCHER, DANIEL; STÖLZLE, STEFAN)
Applicant: CONTINENTAL ENGINEERING SERVICES GMBH [DE]; CONTINENTAL TEVES AG & CO. OHG [DE] + (CONTINENTAL ENGINEERING SERVICES GMBH; CONTINENTAL TEVES AG & CO . OHG)
Classification:
International: B60W40/06; G01L5/18; G01N19/02
European: B60W40/06B; G01N21/47F
Application number: 20,100,719 DE201010027647
Priority number (s): DE201010027647 20,100,719; DE200910033745 20,090,717
The EPA is not responsible for the accuracy of data originating from other authorities than the EPO, and thus particularly liable not for the completeness, timeliness or fitness for a particular purpose. Information, please refer to the respective patent authorities.
translate this text description of DE 102010027647 (A1)
[0001] The present invention relates to a sensor arrangement according to the preamble of claim 1 and a method according to the preamble of claim 11
[0002] Modern electronic driver assistance and vehicle dynamics systems are often dependent on access to information on the adhesion coefficient between road and tire, or at least to make assumptions. By way of example, a driver assistance system is called to prevent accidents. In such a System, it is very important to know the adhesion coefficient and included in the calculation of warning and action points in time. If the adhesion coefficient assumed to be too low, the system would warn or intervene too early, and patronize this way the driver. Appropriately designed systems would be accepted by drivers is difficult. If the adhesion coefficient assumed to be high, and warns the system uses too late, for example, that a collision may not be prevented.
[0003] In addition to the above example, there are several other driver assistance and vehicle dynamics systems, the system behavior by an information on the adhesion coefficient could be improved. Furthermore, the driver can be informed about a bad road-tire contact to adapt their driving style accordingly can.
[0004] The following approaches are currently used in electronic brake systems, in order to give the coefficient of adhesion as well as determination:
- Adoption of a fixed value for the adhesion coefficient
- Indirect determination of the coefficient of adhesion by means of mathematical methods from others in the vehicle (directly) measured sizes . In estimating the coefficient of adhesion, for example, non-linear state estimator or Kalman filters are used.
[0005] The former approach by adopting a firm adhesion coefficient is used in some systems to applications, including driver assistance systems to avoid accidents. Is generally accepted as such in the calculations of the warning and / or intervention time points an ideal adhesion between tire and road surface. This can lead to warning on low-adhesion to late / intervention is - a collision can not be prevented.
[0006] The procedure is referred to as the second example, dynamic control systems application. In this case, is performed on the basis of directly measured vessel sizes to estimate the unused adhesion. Unless dynamic driving situations, can be relatively good results. If the vehicle is in a driving situation, but with only small accelerations, so these approaches not necessarily lead to the desired success, since the adhesion coefficient is exploited in this case considerably smaller than the real one.
[0007] The present invention, the task has been to propose a sensor array and a method by which a relatively precise determination of a coefficient information of the road surface is made possible, especially in uniform driving conditions of the motor vehicle.
[0008] This object is achieved by the sensor arrangement according to claim 1 and by the method according to claim 11
[0009] In the information-preferably a friction coefficient of adhesion is understood.
[0010] It is preferred that the electronic evaluation circuit is designed so that the intensity values or dependent variables that upon detection of the reflected or scattered radiation by the at least one radiation emitter unit and / or one or more additional sensor units be provided in a classified Klassifikatoreinheit, with the coefficient of friction Klassifikatoreinheit information, as friction or Reibwerttyp or Reibwertintervall, calculated and in particular at least provides a quality information that an information contains over the validity and / or reliability of the information friction.
[0011] The Klassifikatoreinheit the electronic evaluation circuit is conveniently designed so that they moved into a frequency analysis of the radiation detection output signals of the at least one radiation-emitting unit and / or one or more additional sensor units performs and especially after the frequency analysis, an energy distribution pattern defined on one or more frequency ranges and / or related to energy levels in defined frequency bands detects and / or recorded and the energy distribution pattern in the light of reference criteria and / or distribution patterns, the reference energy Friction information maps.
[0012] In the radiation detection output signals, preferably the output signals of at least one radiation-emitting unit and / or one or understood the more additional sensor units dependent covered by the reflected or scattered radiation or this code or the corresponding detected intensity of this radiation code. The radiation detection output signals are particularly digital signals or sequences of values.
[0013] The Klassifikatoreinheit the electronic evaluation circuit is conveniently designed so that a function of the variance and / or standard deviation, in particular by means of a fuzzy logic weighted, the radiation detection output signals of the at least one radiation-emitting unit and / or one or more additional sensor units determine the quality of the information.
[0014] The Klassifikatoreinheit the electronic evaluation circuit is preferably designed so that they help determine the quality information more parameters to check the plausibility of the friction coefficient information, such as, or at least one of the following parameters, a temperature information and / or a rain sensor information and / or a time / date taken into account.
[0015] It is preferred that the sensor array has a plurality of radiation emitter units which are defined to each other by a Distance away, based on a parallel with the road surface, are arranged in the vehicle with this radiation emitter units are all directed primarily to a common point or a common destination of the road surface.
[0016] Alternatively, preferably, the sensor arrangement of a plurality of radiation emitting units in a common cluster integrated unit, said radiation emitter units are each directed to different points of the road surface.
[0017] It is preferred that one or more radiation emitting units, each comprising one or a laser element which emits radiation, and particularly to a photovoltaic cell, which reflected and / or scattered radiation detected.
[0018] It is desirable that the photovoltaic cell is formed as a photodiode, and in particular the one or more radiation emitting units or any radiation emitter unit as Vertical Cavity Surface Emitting Laser, "Vertical Cavity Surface Emitting Laser" designed with integrated photodiode.
[0019] Alternatively, preferably includes one or more of the radiation emitter units on and one laser element that emits radiation both sensed or detected, in particular by superimposing the laser given by the radiation emitter unit comprises preferably at no additional sensor element.
[0020] The sensor arrangement is preferably such that they additionally reflected from the road surface radiation in at least one speed, especially the vehicle longitudinal speed of the motor vehicle is determined relative to the road surface and / or the distance of the vehicle chassis to the road surface determined, preferably this same radiation emitter unit and the same electronic evaluation circuit used. Most preferably, the sensor system is both designed to detect a vehicle speed and the distance of the vehicle chassis to the road surface, wherein each switch between these observations.
[0021] The electronic evaluation circuit is preferred to determine the friction coefficient information and / or quality information to a central electronic control unit, in particular a motor vehicle control system or motor vehicle braking system, combined.
[0022] The input side Klassifikatoreinheit comprises preferably a low pass.
[0023] The sensor arrangement preferably detected the reflected and the scattered radiation substantially in separate units, particularly in radiation emitter units and additional sensor units that are added to this in relation to a road surface parallel to each other or spaced apart.
[0024] The Klassifikatoreinheit is conveniently designed so that they are essentially the radiation detection output signals of the units, which record mostly the reflected radiation, and particularly preferably from the same unit or the same units, which emit the radiation emitted / or arranged in close proximity to the emitting unit / s, and the units, which cover mainly the scattered radiation and are arranged preferably in a defined distance from the emitting unit and the units emit, processed separately, at least pre-processed separately, after which the coefficient of friction together information and / or the quality of information is determined.
[0025] The at least one radiation emitter unit is preferably a laser, which monochromatic, continuous, infrared laser light emitted.
[0026] The present invention preferably an exemplary sensor assembly and an exemplary method by which to get a better estimate of the coefficient of adhesion, so make that even in non-dynamic driving situations, a reliable and robust classification of adhesion between the road and tires leaves. That procedure can be used to determine the adhesion between tire and road surface and to estimate a Kraftschlussbeiwertklasse based on the reflection and absorption properties of the condition of the road surface in conjunction with an intermediate medium be applied (eg water). To obtain a higher robustness can already existing estimation and / or methods of measurement by said input information to be added.
[0027] As specific embodiment, the sensor arrangement is preferably configured and at least one radiation emitter unit is arranged and oriented to the road surface is scanned in front of the vehicle, so as to obtain a prediction for the coming adhesion coefficient. In this way it can be more responsive to changes in adhesion.
[0028] Suitably, the at least one radiation emitter unit both emitter and receiver or sensor. In this Case is due to the relative motion between the emitter and the road surface in the beam direction, a frequency shift of the reflected light, which is also called "Doppler effect". This measuring method is characterized in that the laser emitter is used simultaneously as a measuring cell and interfere there photons emitted and received ("self-mixing"). For example, by means of frequency analysis is determined from the interference signal, the frequency difference between emitted and reflected photons. From the amplitude of the spectrum frequencies present a statement can be derived on the reflectivity of the background. Such "self-mixing" laser system, for example, a vertical-cavity surface-laser.
[0029] The advantages of the proposed procedure and an example of the exemplary sensor assembly over other optical methods include:
- The used IR light is not visible to people and thus can not interfere with other traffic.
- Transmitted and reflected photons are in a precise phase relationship to each other (coherent laser light), so other sources, even with the same frequency, are not covered by the cell.
- The described technology is now available in a highly integrated, allowing for cost implementation and easy integration into the vehicle.
- The fact that transmission and measurement unit are integrated in one component, reduces costs and increases accuracy.
- The power radiated by the laser can be as low in this technology that occurred with a direct exposure to the human eye (eg, mechanics) no damage.
- The small diameter of the focused laser beam requires only small "exit window", which read itself, the system easy to protect against contamination.
- Due to the low-cost, miniaturized design of the VCSEL can be integrated in a single component multiple lasers, allowing multiple and / or redundant measurement directions can be detected.
[0030] preferred over a suitable geometric arrangement several lasers, the back scattering and reflection are recorded in different angles of incidence. This allows a back-scattering profile as a function of the angle of incidence can be generated, which is characteristic of the nature of any road surface. While it is expected, for example, on rough surfaces a nearly homogeneous reflection profile (similar backscatter at all angles), shown with smooth surfaces blunt pointed impact angles less backscatter than (ideally mirror backscatter or reflection with only normal incidence of laser beam on track ).
[0031] Based on the different rates of backscattering among the angles of incidence, is measured under such a provision is liable to the prevailing combination of reflexivity / roughness of the surface and is possible on the road be located intermediate medium. With this information, an inference to be drawn on the predominant use of conventional air in tire traction between tire and road surface.
[0032] For more options / preferred method steps for signal evaluation are:
- frequency analysis of the amplitude signal: It is expected that different surfaces have different reflection patterns, which are reflected in the spectrum.
- standard deviation of the amplitude signal: it is to Expect that different surfaces have different standard deviations.
- the use of filters with specific frequency response: It is expected that the friction characteristic information is available in a specific frequency range that is specifically extracted from the amplitude signal.
- The distance signal from a sensor provides information about the roughness of the road. Rough road surfaces have different coefficients of friction, and this could be an indication of loose snow or gravel.
- The amplitude signal can also be used relative: If from another system to the current friction Reibwertschätzung known, and the amplitude signal has a jump may by way of a quick Reibwertsprung be closed.
[0033] It is desirable that the sensor assembly at least one CV-sensor (closing velocity sensor) for detecting road surface has. In a CV-sensor, particularly a sensor is understood to be otherwise mounted for measuring the distance between vehicles in a vehicle used is.
[0034] Other preferred embodiments will become apparent from the following description of embodiments with reference to figures.
[0035] It shows in a schematic representation of exemplary
[0036] 1, a sensor system with three laser sensors, laser 1 - 3, as the radiation emitter units
[0037] 2, a sensor array comprising a cluster unit or a laser sensor clusters,
[0038] 3 signal processing and process flow diagram for Reibwertklassifizierung with an optical sensor,
[0039] 4 classification of different road surfaces with a CV sensor (closing velocity sensor), and
[0040 ] 5 is an exemplary waveform of the Reibwertklassifizierung with an exemplary sensor arrangement in accordance with such a CV-sensor.
[0041] According to example, all laser beams or laser beams of laser 1 - played three meet at a point on the ground as in Figure 1, to obtain the backscatter profile on exactly this point. In an alternative exemplary Embodiment uses a laser sensor cluster (housing) with several laser emitters and sensors, in which the different laser beams are emitted from (approximately) a point illustrated by means of 2, due to the different angle is not, however, impinge at a point on the road. Assuming that the road surface is homogeneous, such effects can be neglected.
[0042] The signal evaluation of a system for Reibwertschätzung is illustrated by way of example 3, where members of the functional blocks Plausibility check and classificatory Intensity of Klassifikatoreinheit the electronic evaluation circuit or part of this circuit. First, there is a plausibility check. In this case, ensure that only measurement values are used where the roadway is actually measured. Does the sensor, for example the speed, then check that the measured speed is in the same range as the speed, for example, measured by wheel speed sensors. For example, the sensor detects the distance, then check that the measured distance in the range of typical sensor-distance road lies.
[0043] In the second step of the plausibility signal, the road situation and thus indirectly classified the coefficient of friction. The main feature is the amplitude dargstellt dar. in Figure 4, amplitude ranges can be assigned to different road conditions. This assignment can take shape through a fuzzy logic module. Each amplitude range is assigned a coefficient of friction, the weighted share in the transition is.
[0044] The description of the effect were measured initially given in 4 road surfaces. The dots each represent the mean and error bars indicate the standard deviation of a measurement, with measurements 1 - represent 4 and 13 x 20 Minauten longer trips. There is a clear distinction of the various roadways seen.
[0045] 5 shows the waveform of the signal or the output of the CV sensor. Also here is a clear and also to detect very fast detection of the different substrates. Especially in the upper diagram itself may be a multiple [mu]-jump can be detected, with the asphalt, only about 5 feet long.
laser-based method for Reibwertklassifikation in vehicles
Technical and scientific translations
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