WO2009124900A1

WO2009124900A1 - Radiometric sensor device for non-contact temperature measurement and method for radiometric, non-contact temperature monitoring of a detection area

Info

Publication number: WO2009124900A1
Application number: PCT/EP2009/054070
Authority: WO
Inventors: Juergen Hasch; Christian Waldschmidt; Michael Thiel
Original assignee: Robert Bosch Gmbh
Priority date: 2008-04-09
Filing date: 2009-04-06
Publication date: 2009-10-15
Also published as: EP2265915A1; DE102008001067A1

Abstract

The invention relates to a radiometric sensor device for non-contact temperature measurement in a detection area (5), comprising: an antenna (2) for receiving radio and/or microwave radiation (R) and for issuing a microwave signal (S1), and means (3, 4, 8) for recording and evaluating the microwave signal (S1) and for issuing an output signal (S2). According to the invention, the means for recording and evaluating the microwave signal (S1) determine discrete reference values (Tbi) that follow sequentially from the microwave signal (S1) and determine from temporal changes in the discrete reference values (Tbi) whether a relevant temperature change has taken place in the detection area (5). To this end, the means preferably comprise: a radiometer device (3) for recording the microwave signal (S1) and for issuing an analog band signal (B), and a determining device (4) for recording and evaluating the band signal and for determining the discrete reference values (Tbi) and a temporal temperature behavior in the detection area (5). A corresponding method is also provided.

Description

Description title

Radiometric sensor device for non-contact temperature measurement and method for radiometric, non-contact temperature monitoring of a detection range

State of the art

Sensor devices for non-contact temperature measurement are used for different tasks, in particular for fire protection or for the detection of persons.

In car alarm systems or interior vehicle monitoring, ultrasound, radar, infrared sensors or video cameras are used. In

Building alarm systems are in particular used for infrared sensors or double radar measuring devices. As a protection sensor for electrical tools, eg. B. as a saw stop to avoid injury to the user in particular capacitive methods are known; In this case, the saw is often destroyed when triggering the protection sensor. When motor vehicle pedestrian protection in particular radar, ultrasonic or infrared sensors are used.

Furthermore, it is known for comfort adjustments in the vehicle, z. B. a comfort entry-Go adjustment, proximity sensors to use as capacitive sensors or radar sensors.

Radar and ultrasound, video camera and capacitive measurements allow distance and differential velocity measurements. Beruh- In contrast, temperature-free temperature measurements are generally carried out radiometrically, ie by measuring the irradiance.

In this case, infrared sensors allow temperature measurements by detecting the heat radiation in the IR range, although the electromagnetic radiation of the temperature radiator in this wavelength range can be easily shielded.

Besides photonic temperature measurements by infrared sensors, radiometric millimeter-wave measurements are also known, in particular for the detection of mines, for surface analysis and in astronomy. In this case, the temperature radiation of the observed body is recorded in the long-wave range of the spectrum, in particular the millimeter wavelength range or the megahertz frequency range, whereby in general a noise signal is determined. Unlike the photonic infrared measurements by photodiodes or similar sensors, the recording of the radio radiation takes place as a frequency measurement via antennas or dipole antennas. This results in a signal that does not drop as much as it does in a photonic measurement, even for higher frequencies.

Radiometric temperature measurements have some advantages over infrared temperature sensors. Thus, the radiation can be detected from deeper areas of the viewed object or the detection area. A shielding of the radio wave radiation is usually possible only by metal surfaces, but not by clothing or other thinner objects.

These millimeter radiometers are generally of a discrete design and must be laboriously calibrated, since absolute noise temperature measurement is required. In this case, a switch in the receiving part is generally required for the calibration. US 2005/0053118 A1 describes a system and a method for the non-contact measurement of the temperature of an object using microwave radiometry, which can be used in particular for monitoring buildings. In this case, comparative measurements are carried out in which the radio-wave radiation of the object is recorded alternately in a transmission mode and subsequently blocked in a blocking mode, with the recording of a comparison object taking place in the blocking mode as comparison value. From this comparison, a calibration can thus be carried out for determining the temperature of the object under consideration.

However, the calibration of the measurement signal by comparison measurements according to US 2005/0053118 A1 is relatively expensive, so that the use of radiometric measurements is limited.

Furthermore, active measurements in the radar wavelength range are known, but in general restrictions on narrow ISM bands are required, which limit the performance of the radar system and require lengthy and costly approval procedures. Furthermore, classical radar sensors emitting radar radiation due to electrosmog are not unproblematic.

Disclosure of the invention

According to the invention, a passive detection system or monitoring system is sought with measurement of the temperature-dependent radio radiation and / or microwave radiation, in particular of millimeter or microwaves. In this case, millimeter waves can advantageously be detected by means of an antenna or radiometrically, since such radiometric antennas can be produced in large quantities compared to microwave sensors with lower costs. The invention is based on the idea of carrying out a radiometric measurement of the temperature radiation in the radio wave range and / or microwave range, in particular in the millimeter wavelength range, by taking successive measured values or discrete reference values formed from measurements and considering the differential changes. In principle, the received wavelength range can only be in the microwave range or even only in the radio wave range, or extend over both wavelength ranges. In the following, the signal output by the antenna is always referred to as microwave signal in all cases.

Thus, according to the invention, changes in the measured thermal noise power are detected. The noise power depends on the temperature of the considered material surfaces and the material properties. A rapid change in the measured noise power can thus be assigned according to the invention to the occurrence of new objects in the detection range of the sensor or very rapid temperature changes. By detecting changes in the noise temperature, no elaborate calibration procedures in the reception branch are required according to the invention.

The discrete reference values can be formed in particular by integration over predetermined time intervals. This is advantageously done after an analog-to-digital conversion. Thus, by temporal integration of the measurement signal or a signal formed from the measurement signal reference values are formed and examined for relevant temporal changes. The result is a differential measurement that can be assigned to the respective events.

In this case, the temporal change of successive reference values can be compared with a predetermined threshold value, and if exceeded of the threshold value to a significant change and below the threshold value to a non-relevant change are detected.

Since, according to the invention, a passive method is carried out without electromagnetic waves emitted by a transmitter, no EMC problem arises.

According to the invention, an antenna with a suitable antenna diagram can be selected in order to enable a spot measurement of a relevant detection area. Furthermore, according to the invention no switch in the receiving branch for the calibration is required. Thus, the sensitivity of the sensor device according to the invention is increased.

According to the invention, in particular vehicle alarm systems, building alarm systems or monitoring sensors or motion detectors can be formed. Furthermore, protection sensors can be created to prevent accidents by z. As a user or a body part of a user in a hazardous area, eg. B. in front of the saw blade of a circular saw, is detected. According to the invention, people or body parts with clothing or protective clothing, for. As a thicker glove, are detected by measuring the noise power of the radio waves.

Furthermore, vehicle pedestrian protection measurements, an environmental sensor system and a proximity sensor for comfort adjustments on vehicles can be made possible according to the invention.

Brief description of the drawings

Fig. 1 shows a block diagram of a radiometric see sensor device according to the invention;

2 shows a flow chart of a method according to the invention. Embodiment of the invention

A radiometric sensor device 1 has an antenna or dipole antenna 2 for receiving radio waves and / or microwaves R and outputting a microwave signal S1, a radiometer 3 for receiving the microwave signal S1 and outputting a baseband signal B, a detection device 4 for recording the Baseband signal B and detection and a control device 8 for outputting control signals S2.

The radiometric sensor device 1 is used in accordance with the embodiment shown in FIG. 1 for monitoring a detection region 5 in the environment of the sensor device 1, for example, in FIG. B. on a building. 6

The antenna 2 is designed as an arbitrarily designed directional antenna, z. B. dipole or patch antenna, and receives incident radio waves R from the detection area 5 on. Optionally, apertures can be used to limit their detection angle 7.

The antenna 2 is for receiving radio waves R or microwaves R, advantageously in the microwave to millimeter range with an arbitrarily selected bandwidth, from z. B. 1 MHz to 10 GHz, designed from the detection area 5. The antenna 2 outputs the microwave signal S1 as a noise signal to the radiometer 3, which converts the microwave signal S1 in a conventional manner into a baseband signal B, which indicates the amplitude of the noise power of the microwave signal S1. The baseband signal B is output to the detection means 4.

The radiometer 3 may optionally also generate an intermediate frequency signal (IF signal); However, this is basically not necessary according to the invention and depends on the available bandwidths.

The determination device 4 is shown in FIG. 1 with its elements 4.0 to 4.9 explained in more detail. The determination device 4 optionally has a modeling device 4.0 for generating the IF signal IF and a bandpass filter 4.1 which receives the signal IF and outputs a band-pass filtered IF signal B1. Subsequently, an RF amplifier 4.2 is provided, which either according to the dotted line directly receives the output from the radiometer 3 baseband signal B or output from the bandpass filter 4.1 band-pass filtered IF signal B1 and amplified, z. The signal B2 is applied to a device 4.3 which multiplies the signal B2 by itself and generates the rectified signal B3 as an equivalent DC voltage signal; The device 4.3 can be, for example, a diode rectifier or frequency mixer. The signal B3 is low-pass filtered in a subsequent device 4.4 and supplied as a signal B4 an analog-to-digital converter 4.5, which outputs a digital signal B5 to a digital integrator 4.6, as a low-pass integration over a predetermined period of time or time difference Δt performs.

In the digital integrator 4.6, the voltage U _OBJ recorded as the digital signal B5 is integrated over the predetermined time difference Δt. This is based on the following consideration:

A temperature T _{OBJ of} the detection range 5 (or temperature averaged over the detection range 5) is proportional to the voltage U _OBJ , which results as a value of the voltage U _OBJ corresponding to the signal B5 over time, ie

where Δt = t1 - tθ.

According to the invention, the time output by the integrator 4.6 can directly Liehe integral are used as uncalibrated temperature or temperature reference value Tb and stored in a first memory 4.7. When using the same time intervals .DELTA.t for the successive measurements in principle, the division with .DELTA.t can be omitted and can be compared directly the integrals.

This results in a sequence of discrete reference values Tb, where i = 1, 2, 3,... A comparison device 4.8 determines a differential temperature from two consecutive values Tb,, Tb, + i and compares this difference value with a reference value N x ΔTs where ΔTs is the minimum temperature increase detectable with the system and can be determined experimentally or theoretically estimated. N gives this a safety factor in the range of z. B. 1, 2 to 2.

In the comparison device 4.8, the comparison ΔTb, = Tb ₁₊ I -Tb ₁ , <N • ΔTs is thus formed.

If the difference ΔTb, which corresponds to or is proportional to the temperature change in the detection range 5 for two consecutive measurements, is smaller than the reference value N • ΔTs, a 0 is stored in a second memory 4.9 as the determined temperature change ΔTi; If the difference ΔTb is greater than or equal to N • ΔTs, the measured differential temperature ΔTb is stored in the second memory 4.9.

Thus, in the second memory 4.9 consecutive difference values are stored, which correspond to the measured differential temperatures in the detection area 5. The second memory 4.9 is read by a control device 8, which subsequently performs a rating. Thus, due to the difference formation and the consideration according to the invention of not carrying out any calibration or normalization of these values, it is possible to directly deduce changes from the sequence of the difference values ΔTb. In this case, the determination device 4 with its elements 4.0 to 4.9 and the control device 8 can be realized in terms of hardware, for. B. as a fixed wiring, or purely software-based, so that the detection device 4 and the controller 8 can also be implemented with a program can.

According to the invention 8 statements about the temperature changes can be made in the control device, such. B. the emergence of a fire or passing through a person 10 through the detection area 5 and the detection angle 7 (solid angle). If the detection area 5 a safety area at a machine to be handled, z. B. represents a hazardous area in front of the saw blade of a circular saw, also a sufficiently rapid increase in the temperature can be detected as entering or going into the danger zone. Sufficiently fast temperature changes can thus be assigned to a respective event, whereupon the control device 8 outputs a control signal S2, the z. B. a warning signal upon detection of a fire or the entry of the detection area 5, or a switching signal z. B. can be for a circular saw.

By means of the differential measuring principle according to the invention, drift effects of the circuit according to the invention as well as temporally slow changes in the room temperature within the detection range, as they are, for example, are shown in FIG. B. when turning on and off of radiators or by changes in the day temperature eratur, not recorded. However, rapid temperature changes or sufficiently large temperature differences within the defined integration time Δt can be detected.

In this case, Δt as well as the other values N and ΔTs are adapted to the respective needs of the application.

In FIG. 1, the person 10 enters the detection area 5 when the person enters and when the person 10 emerges from the detection area 5, changes in the averaged temperature T of the detection area 5 are respectively detected if the values Δt, N and ΔTs are selected accordingly.

In order to be able to carry out integration times Δt = 50 to 200 ms as economically as possible, the integration according to the invention is advantageously implemented digitally. In order to keep the sampling frequency of the analog-to-digital converter 4.5 low, an NF low-pass filter 4.4 is advantageously provided after the diode modulator 4.1, the z. B. a suitable cutoff frequency, z. B. 1 KHz to 20 KHz, and thus higher-frequency noise components removed from the rectified baseband signal. This is based on the idea according to the invention that such higher frequencies are not relevant for the detection according to the invention and the subsequent digitization or analog-to-digital conversion with the low-pass filtering is made simpler. The cutoff frequency TP can in this case also in the a-kustischen range of z. B. 20 KHz.

2, after a start in step StO, the microwave radiation R is subsequently recorded in step St1 and output to the radiometer 3 as microwave signal S1 or noise signal. In step St2, optionally the baseband is converted into an IF band or IF signal ZF transformed. In step St3, this IF signal is band-pass filtered and passed as signal B1. In step St4 to Stδ, the subsequent evaluation of the original bandpass signal B or of the modulated IF signal B1 takes place, the analog signal being amplified in step St4, and then the analog noise signal being converted into the equivalent direct voltage signal B3 in step St5. In step 6, the DC voltage signal B3 is low-pass filtered to the signal B4, in step St7, the analog-to-digital conversion of the analog signal B4 and output of B5, which is subsequently integrated in step Stδ, whereby the discrete reference values Tbi are generated. In step St9, the reference value determined by the temporal integration is compared with the comparison value and the determination as to whether the difference is smaller than N × ΔTs or not, whereupon statements in accordance with the averaged temperature change can take place in step StI 0 and if necessary subsequently the control signal S2 is output.

Claims

claims

1. A radiometric sensor device for non-contact temperature measurement in a detection area (5), comprising: an antenna (2) for receiving radio and / or microwave radiation (R) and outputting a microwave signal (S1), means (3, 4, 8 ) for receiving and evaluating the microwave signal (S1) and output of an output signal (S2), characterized in that the means (3, 4, 8) for receiving and evaluating the microwave signal (S1) from the microwave signal (S1) successive discrete reference values (Tb ₁ ) determine and from temporal changes of the discrete reference values (Tb,) determine whether a relevant temperature change has occurred in the detection area (5).

2. Radiometric sensor device according to claim 1, characterized in that the means (3, 4, 8) for receiving and evaluating the Mikrowellensig- signal (S1) comprise: a radiometer device (3) for receiving the microwave signal (S1) and output an analog band signal (B), and a detection means (4) for receiving and processing the band signal (B) and for determining the successive discrete reference values (Tb,) from the band signal (B) or from the band signal

Band signal (B) detected signals (B1, B2, B3, B4, B5), and a control device (8) for evaluating the determined by the detection means discrete reference values (Tb ₁ ) and the output of the output signal (S2).

3. Radiometric sensor device according to claim 2, characterized in that the detection device (4) comprises: an integrator (4.6) for time integrating or summing the band signal or a signal (B5) formed from the band signal (B) and outputting the successive discrete reference values (Tb ₁ ), and comparing means (4.8) for comparing successive reference values (Tb ₁ ).

4. Radiometric sensor device according to claim 3, characterized in that the comparison device (4.8) the change or difference of successive reference values (Tb ₁ ) with a

Threshold (N • ΔTs) compares.

5. Radiometric sensor device according to claim 4, characterized in that in the case that the determined difference value (ΔTb ,,) of two successive discrete reference values (Tb ,, Tb, + i) is smaller than the threshold value (N • ΔTs), is detected to a constant temperature, and in the event that the determined difference value exceeds the threshold value (N • ΔTs), a relevant temperature change is detected.

6. Radiometric sensor device according to claim 5, characterized in that the last discrete reference value (Tb,) is stored in each case in a first memory (4.7) and retrieved by the comparison device (4.8), and at a detected relevant temperature change, the differential temperature (ΔTb, ) is stored in a second memory (4.9).

7. Radiometric sensor device according to one of claims 3 to 6, characterized in that in the detection device (4) an analog-to-digital converter (4.5) for converting the band signal (B) or an analog signal (B4) generated from the band signal (B), and the digital signal (B5) output from the analog-to-digital converter (4.5) is output to the integrator (4.6).

8. Radiometric sensor device according to claim 7, characterized in that the determining device (4) has an analog low-pass filter (4.4) for removing noise components, which outputs a signal (B4) to the integrator (4.6).

9. Radiometric sensor device according to one of the preceding claims, characterized in that the control device (4) on detection of a rapid change in temperature output signal (S2) outputs a control signal (S2).

10. Radiometric sensor device according to claim 9, characterized in that the control signal (S2) is a warning or shutdown signal.

11. Radiometric sensor device according to one of the preceding claims, characterized in that the antenna (2) is a directional antenna and / or diaphragm devices for limiting their detection angle (7) for the microwave radiation (R).

12. Radiometric sensor device according to one of the preceding claims, characterized in that the antenna (2) is designed to receive microwave radiation (R) in the millimeter wavelength range.

13. A method for radiometric, non-contact temperature monitoring of a detection area (5), comprising at least the following steps:

Recording radio and / or microwave radiation (R) from the detection area (5) and output of an analog microwave signal (S1) (St1),

Determining successive discrete reference values (Tb ₁ ) from the microwave signal (S1) or a signal generated from the microwave signal (B, B1, B2, B3, B4, B5) (St7),

Determining temporal changes of the discrete reference values (Tb,), determining from the temporal changes of the discrete reference values (Tb,), whether a relevant temperature change has occurred in the detection area (5), and outputting an output signal (S2) in dependence on the determined time changes ,

14. The method according to claim 13, characterized by the other

Step: generating a band signal (B) from the microwave signal (S1)

(St2)., Wherein the temporal changes of the discrete reference values (Tb ₁ ) are determined from the band signal (B) or further signals (B1, B2, B3, B4, B5) generated from the band signal.

A method according to claim 14, characterized in that the successive discrete reference values (Tb ₁ ) are formed by time-integrating or summing the band signal (B) or a signal (B5) formed from the band signal (B), and changes or differences of successive reference values (Tb,) are compared with a threshold value (N • ΔTs).

16. The method according to claim 15, characterized in that in the case that the determined difference value (ΔTb ,,) of two consecutive discrete reference values (Tb ₁ , Tb, + i) is smaller than the threshold value (N • ΔTs), on a constant temperature is detected, and in the event that the determined difference value exceeds the threshold value (N • ΔTs), a relevant temperature change is detected.