WO2008043419A1 - Method for sensing a physical quantity and device therefor - Google Patents

Abstract

The invention relates to a method for sensing a physical quantity, in particular a distance, with the following steps: - Sending of at least one transmitted signal (ul) with a predefinable first signal shape over a first transmission path (110), the transmission function of which depends on the physical quantity to be measured, wherein a first reception signal (ul') is received upon the output of the first transmission path (110), - Sending of at least one first reference signal (u2) with a predefinable reference signal shape over a reference transmission path (120), wherein the reference transmission path preferably has a known transmission function, and wherein a reference reception signal (u2'') is received upon an output of the reference transmission path (120), - Analysis of the first reception signal (ul') and/or the first reference signal (u2) and/or the reference reception signal (u2''), in order to deduce the physical quantity.

Description

Title: Method of detecting a physical quantity and device therefor

Besehreibung

The invention relates to a method for detecting a physical quantity, in particular a distance and a device therefor.

The method according to the invention comprises the following steps:

Transmitting at least one first transmission signal having a predeterminable first signal form over a first transmission path whose transmission function depends on the physical quantity to be detected, a first reception signal being obtained at an output of the first transmission path,

- Sending at least a first reference signal with a predetermined reference waveform via a reference transmission path, wherein the

Reference transmission path preferably has a known transfer function and wherein a reference reception signal is obtained at an output of the reference transmission path,

- Analyzing the first received signal and / or the first reference signal and / or the

Reference receive signal to conclude the physical quantity.

The inventive use of at least one first transmission signal and at least one first reference signal advantageously allows a flexible analysis of the received Signals, in particular a differential analysis, which allows the compensation of interference.

For analysis, the first received signal is advantageously compared with the reference received signal.

The first transmission signal and the reference signal advantageously each have non-zero frequency components, and the time functions of the signals are chosen such that they add up to a DC signal over at least a predefinable time range. This makes a particularly simple evaluation possible, e.g. a compensation of an amplitude of one of the signals or a phase relationship of the signals may comprise each other, with the aim of obtaining a DC signal as the sum of both signals. The control variables which describe the change of the amplitude or phase position advantageously simultaneously contain information about the first transmission path, e.g. via the attenuation of the first transmission signal or a delay of the first transmission signal due to transit time effects of the first transmission signal in the first transmission path.

Advantageously, the first transmission signal and the reference signal may be e.g. each be a sinusoidal or rectangular signal, wherein the first transmission signal has a predetermined phase shift, in particular 180 degrees, to the reference signal. A phase difference, if any, caused by the first transmission path between the received signals, which is different from 180 degrees, contains information about the signal path / the transit time of the transmission signal.

According to the invention, the analysis advantageously comprises the following steps:

Adding or multiplying the first received signal with the reference received signal to obtain a received signal, Evaluating predeterminable time ranges of the received signal in order to conclude an attenuation and / or phase shift of the transmitted signal through the first transmission path,

- inferring the physical variable from the attenuation and / or phase shift.

The evaluation of predefinable time ranges advantageously comprises integrating the received signal over a plurality of predefinable time ranges or adding the received signal over a plurality of predefinable time ranges. Time periods in the sense of this invention may be periodic durations or parts thereof in the case of periodic signals; In general, arbitrary time ranges can also be used for the evaluation of which it is assumed that corresponding received signals contain information of interest.

In a further embodiment of the method according to the invention, different time ranges of the received signal are preferably evaluated in order to infer the attenuation and / or phase shift of the transmitted signal through the first transmission link.

For example, in the case of rectangular transmission or reference signals, in particular that time range of the received signals or of the received signal is of interest for obtaining phase information in which the signals represent a change of state, i. e.g. from high to low or inverse thereto, while information about differences in the amplitude of received signals can also be obtained in other time ranges.

Although the method according to the invention can also be carried out with capacitive or acoustic signals or transmission paths, it is preferred to use a first transmission signal (ul) in the form of an optical signal. The Reference signal can also be optical or a purely electrical signal.

In the context of the analysis according to the invention of the first received signal or of the received signal, it is advantageous to deduce a distance from a transmitter of the first transmitted signal to an obstacle.

An analysis of statistical properties of the received signal and / or the physical variable, in particular a distance, has proven to be particularly advantageous. If a distance from the transmitter to an obstacle determined by means of the method according to the invention has special statistical properties, this may, for example, indicate the presence of an aerosol, such as e.g. Fog or spray are closed in the first transmission path, because the water droplets of the fog statistically affect the transfer function of the first transmission path and thus also a distance determined therefrom.

At least part of the first transmission path preferably runs in the free space, in particular in the surroundings of a motor vehicle, and from the statistical properties of determined distance values, it is possible to detect the presence of aerosols, such as e.g. Mist be closed in the open space. A system for carrying out the method according to the invention can therefore be compared to conventional ultrasonic distance sensors and the like, e.g. be integrated in a bumper of the motor vehicle.

Advantageously, on-board systems of the motor vehicle, in particular lighting systems and / or driving safety systems, can also be activated or operated as a function of the statistical properties of determined distance values. Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the figures of the drawing. All described or illustrated features, alone or in any combination form the subject matter of the invention, regardless of their summary in the claims or their dependency and regardless of their formulation or representation in the description or in the drawing. In the drawing shows:

FIG. 1 shows a block diagram of a first embodiment of the device according to the invention,

FIG. 2 shows a detailed view of the device from FIG. 1,

FIG. 3 shows a time characteristic of a received signal obtained according to the invention,

Figure 4 shows a first scenario in which the inventive method is used, and

Figure 5 shows another scenario in which the inventive method is used.

FIG. 1 shows an embodiment of the apparatus according to the invention for detecting a physical quantity which is used in the manner described below for measuring the distance between a transmitter 180 (FIG. 4) and an obstacle (FIGS. 4, 5).

The device 100 has a first transmission path 110, via which a first transmission signal ul is transmitted. At the output of the first transmission path 110 is accordingly, a first received signal ul 'obtained. The transmission signal ul is presently an optical signal.

The apparatus 100 further has a reference transmission path 120 shown in dashed lines in FIG. 1, via which a reference signal u2 or u2 'is transmitted. Accordingly, a reference reception signal u2 "is obtained at the output of the reference transmission path 120.

In the reference branch of the device 100, additionally preferably actively formed filter means 140 are provided which can influence an amplitude and / or phase position of the signal u2 with respect to the transmission signal u1.

Preferably, the transmission signal ul and the reference signal u2 has a rectangular waveform, and the signals ul, u2 'have a phase shift of 180 degrees, so that they would complement each other at equal amplitudes to a DC signal.

However, the first transmission signal ul is influenced in the first transmission path 110 as a function of the physical quantity to be detected, in particular with regard to its amplitude and / or its phase position relative to the reference signal u2 or u2 '.

For example, the transmission path 110 can run in the free space, for example between a transmitter 180 (FIG. 4) and an obstacle 200, so that the first transmission signal ul is emitted by the transmitter 180 and a signal correspondingly reflected at the obstacle 200 is transmitted as the first reception signal ul '. (Figure 1) is obtained at the output of the transmission path 110. Due to the distance between the transmitter 180 and the obstacle 200 results inter alia, an attenuation of the first received signal ul 'and a phase shift to the reference received signal u2'', for example, a shorter, known signal path, cf. passes through the reference transmission path 120.

The addition of the received signals ul ', u2 "in the adder 131 according to FIG. 2 therefore leads to a received signal u3, which has, for example, the time profile depicted in FIG.

In the time ranges Tl, T2, T3, T4 clear pulses can be seen, resulting from runtime effects of the transmission signal ul in the first transmission path and the associated phase shift. The phase shift is proportional to the distance between the transmitter 180 and the obstacle 200.

The receive signal u3 is evaluated in addition to a suitable gain by the amplifier 132 preferably only in the time ranges Tl, T2, T3, T4 to obtain information about the phase difference. The evaluation can preferably be carried out by integrating or adding a plurality of pulses from successive time ranges T1, T2, T3, T4. The correspondingly obtained integrated signal is according to investigations by the Applicant in an evaluation of e.g. a few tens of pulses - despite relatively small phase differences due to the high speed of light - by conventional CMOS evaluation circuits, cf. the elements 133, 134, evaluable.

That is, the inventive method allows the evaluation of light transit times of the first transmission signal ul with less complex circuits and at a precision, the distance measurement in the range between about a few centimeters and about several tens of meters.

Analogous to the evaluation of the phase information, the evaluation of the amplitudes of the received signals ul ', u2'' or of the received signal u3 formed therefrom, for example, only in predefinable time ranges T5, T6, T7, T8. The received signal ul ', because of its larger signal path from the transmitter 180 to the obstacle 200, is subject to greater attenuation, which is the deviation of the received signal u3 from a reference amplitude (dashed time axis t in FIG. 3) and those in the time ranges T5, T6 , T7, T8, for example, by means of integration over several time ranges T5, T6, T7, T8 is evaluated.

In the evaluation, the filter 140 (FIG. 1) can be adapted such that the signal u2 "and the signal ul 'complement each other again to form a DC signal despite different signal paths. The filter parameters corresponding thereto contain information about the transfer function of the first transmission path 110 and thus e.g. about the distance to an obstacle 200.

Instead of rectangular signals ul, u2, it is also possible to use sinusoidal signals or other preferably periodic signals which complement each other in a regulated state to form a direct signal.

The method and system according to the invention can advantageously be used in motor vehicles for optical distance measurement.

For example, in the case of an evaluation of statistical properties of a plurality of sequentially determined distance values, it is also possible to deduce the presence of an aerosol such as fog in the transmission path 110, because the water droplets statistically influence the transmission function of the transmission path 110. A corresponding scenario is shown in Figure 5, in which a transmitter 180, the optical transmission signal ul (Figure 1) to a Fog bank 300 sends out and receives a correspondingly reflected signal ul '.

The presence of fog or its density, etc. recognized according to the invention can be used to control on-board systems of the motor vehicle such as e.g. a lighting system or a driving safety system are used.

Claims

claims Method for detecting a physical quantity, in particular a distance, comprising the following steps: - Sending at least a first transmission signal (ul) with a predetermined first waveform over a first transmission path (110) whose transfer function depends on the physical quantity to be detected, wherein a first received signal (ul ') at an output of the first transmission path (110) becomes, - transmitting at least one first reference signal (u2) with a predefinable reference waveform over a reference transmission path (120), the reference transmission path preferably having a known transfer function and a reference receive signal (u2 '') being obtained at an output of the reference transfer path (120), - Analyzing the first received signal (ul ') and / or the first reference signal (u2) and / or the reference received signal (u2' ') to close to the physical size. 2. The method according to claim 1, characterized in that for analysis, the first received signal (ul ') with the reference received signal (u2' ') is compared. 3. The method according to any one of the preceding claims, characterized in that the first transmit signal (ul) and the reference signal (u2) each have non-zero frequency components, and that the time functions of the signals (ul, u2) at least over a predetermined time range to add a DC signal. 4. The method according to claim 3, characterized in that the first transmit signal (ul) and the reference signal (u2) is in each case a sinusoidal or rectangular signal, and that the first transmit signal (ul) a predetermined phase shift, in particular 180 degrees, to the reference signal (u2). 5. The method according to any one of the preceding claims, characterized in that the analysis comprises the following steps: Adding or multiplying the first received signal (ul ') with the reference received signal (u2' ') to obtain a received signal (u3), Evaluating predefinable time ranges of the received signal (u3) in order to conclude an attenuation and / or phase shift of the transmitted signal (ul) through the first transmission path (110), - inferring the physical variable from the attenuation and / or phase shift. 6. The method according to claim 5, characterized in that the evaluation of predeterminable time ranges comprises the integration of the received signal (u3) over a plurality of predefinable time ranges or the adding of the received signal (u3) over a plurality of predeterminable time ranges. 7. The method according to any one of claims 6 or 7, characterized in that in each case different time ranges (Tl, T2, T3, T4, T5, T6, T7, T8) of the received signal (u3) are evaluated to the attenuation and / or Phase shift of the transmission signal (ul) through the first transmission path (110) to close. 8. The method according to any one of the preceding claims, characterized in that the first transmission signal (ul) is an optical signal. 9. The method according to any one of the preceding claims, characterized in that in the context of the analysis at a distance from a transmitter (180) of the first transmission signal (ul) to an obstacle (200, 300) is closed. 10. The method according to any one of the preceding claims, characterized in that statistical properties of the received signal (u3) and / or the physical size, in particular a distance, are evaluated. 11. The method according to claim 10, characterized in that at least part of the first transmission path (110) in the free space, in particular in the environment of a motor vehicle runs, and that from statistical properties of determined distance values on the presence of aerosols such. Mist in the open space is closed. 12. The method according to claim 11, characterized in that on-board systems of the motor vehicle, in particular lighting systems and / or driving safety systems depending on the statistical properties of determined distance values are driven or operated. 13. Device (100) for detecting a physical quantity, in particular a distance, with a transmitter (180) for transmitting at least one first transmission signal (ul) having a predeterminable first signal form via a first transmission path (110) whose transmission function depends on the physical quantity to be detected, a receiver for receiving a first received signal (ul ') at an output of the first transmission path (110), - A reference transmitter for transmitting at least a first reference signal (u2) with a predetermined reference waveform via a reference transmission path (120), wherein the reference transmission path preferably has a known transfer function, a receiver for receiving a first reference reception signal (u2 '') is obtained at an output of the reference transmission path (120), and having a - Evaluation unit (130) for analyzing the first received signal (ul ') and / or the first reference signal (u2) and / or the Reference receive signal (u2 '') to approximate the physical quantity. 14. Device (100) according to claim 13, characterized in that the device is designed for carrying out the method according to one of claims 1 to 12.