GB2491043A - Ultrasound measurement system and method of detecting an obstacle by means of ultrasound - Google Patents

Ultrasound measurement system and method of detecting an obstacle by means of ultrasound Download PDF

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Publication number
GB2491043A
GB2491043A GB1208883.7A GB201208883A GB2491043A GB 2491043 A GB2491043 A GB 2491043A GB 201208883 A GB201208883 A GB 201208883A GB 2491043 A GB2491043 A GB 2491043A
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GB
United Kingdom
Prior art keywords
ultrasound
measurement
current
input
sensor
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Granted
Application number
GB1208883.7A
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GB2491043B (en
GB201208883D0 (en
Inventor
Micha Kalbhenn
Nico Bannow
Tobias Kirchner
Thomas Treptow
Simon Hufnagel
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Robert Bosch GmbH
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Robert Bosch GmbH
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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/523—Details of pulse systems
    • G01S7/526—Receivers
    • G01S7/527—Extracting wanted echo signals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/523—Details of pulse systems
    • G01S7/526—Receivers
    • G01S7/527—Extracting wanted echo signals
    • G01S7/5276—Extracting wanted echo signals using analogue techniques
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
    • G01S15/04—Systems determining presence of a target
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
    • B60R21/01—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents
    • B60R21/013—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents including means for detecting collisions, impending collisions or roll-over
    • B60R21/0134—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents including means for detecting collisions, impending collisions or roll-over responsive to imminent contact with an obstacle, e.g. using radar systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/93—Sonar systems specially adapted for specific applications for anti-collision purposes
    • G01S15/931—Sonar systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/523—Details of pulse systems
    • G01S7/526—Receivers
    • G01S7/529—Gain of receiver varied automatically during pulse-recurrence period
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/534—Details of non-pulse systems
    • G01S7/5345—Gain control of receivers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2420/00—Indexing codes relating to the type of sensors based on the principle of their operation
    • B60W2420/54—Audio sensitive means, e.g. ultrasound
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52004—Means for monitoring or calibrating
    • G01S7/52006—Means for monitoring or calibrating with provision for compensating the effects of temperature

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Mechanical Engineering (AREA)
  • Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Abstract

An ultrasound measurement system for detecting an obstacle is disclosed. At least one ultrasound sensor generates a measurement signal upon reception of an ultrasound pulse which is reflected from the obstacle. The system includes a measurement stage, which provides a virtual earth at one input, the input of the measurement stage being connected to the output of the ultrasound sensor; and an evaluation unit, which is designed to generate the measurement signal on the basis of an evaluation of the current flowing into the measurement stage. The measurement stage may include an operational amplifier, the first input of which forms the input of the measurement stage; the second input is connected to earth. A pair of anti-parallel diodes may be included between the input of the measurement stage and earth. The system may generate a defined ultrasound emission, and may be designed to generate active attenuation of the ultrasound sensor. Such a system may be used in a vehicle assistance system.

Description

Description Title
Ultrasound measurement system and method of detecting an obstacle by means of ultrasound
Prior art
This invention concerns an ultrasound measurement system and a method of detecting an obstacle by means of ultrasound. The method also.concerns a driver assistance system with such an ultrasound measurement system.
From the prior art, ultrasound sensors in whIch a membrane is made to oscillate using a piezo layer are known. In Fig. 1, a piezo element (the piezo layer) of an ultrasound sensor 10 is shown, said piezo element having essentially the electrical equivalent circuit diagram shown in Fig. 1.
The equivalent circuit diagram comprises the series circuit 15, which consists of a coil Ll, a capacitor Cl and a resistor Ri, and to which a capacitor 02', which depends greatly on the ambient temperature, is connected in parallel (not drawn individually). To guarantee a constant resonant frequency of this oscillating circuit, a further capacitor 02' 1 is connected in parallel to the ultrasound sensor 10 (not drawn individually). It has the reverse temperature coefficient of the capacitor 02' . Therefore, the total capacitance of the sensor 10 is finally approximately equal. The two capacitors 02' and C2'' connected in parallel form a (drawn) parallel capacitor C?.
The capacitor 02'', which is connected in parallel to the ultrasound sensor 10 and is required for compensation of the temperature, is expensive and large.
The received ultrasound signal is usually measured by evaluating the voltage at the ultrasound sensor 10. A disadvantage is that after the ultrasound sensor 10 is activated in the context of emitting the ultrasound pulse, the parallel capacitor 02 is usually charged.
The direct voltage at the parallel capacitor 02 is superimposed on the signal to be finally measured at the sensor 10. In Fig. 2, the voltage course U of the voltage signal SU1 at the ultrasound sensor 10, depending on the time t, is shown for a period tl during and after activation of the ultrasound sensor 10.
Consequently, as shown in Fig. 3, the amplifier 30, which is connected to the ultrasound sensor 10, must have one or more high pass filters 20, which filter the direct voltage portion caused by the parallel capacitor 02. This is expensive, and it delays the time until a valid measurement signal is present at the ultrasound sensor 10. The ultrasound sensor 10 is connected to earth 40.
In Fig. 4, the voltage course U of the activation signal S[J and of the amplified voltage signal SU3 at the ultrasound sensor 10, after passing through the high pass filter 20, depending on the time t, is shown for the time tl. As can be seen in Fig. 4, a usable voltage signal S02 is not present at the ultrasound sensor 10 until after a short time ôt has passed after activation with an activation signal SU.
A further problem is that the measurement of the voltage SU2 at the sensor 10 is usually relative to earth 40.
Therefore, it is impossible to determine, on the basis of the current flow into the parallel capacitor C2, how large the current in the coil Ll is. This current is specially important for evaluation, both for simple capture of the ultrasound pulse echo and for the active attenuation of the piezo layer.
The coil current corresponds to the speed of the sensor membrane, and is thus also the source of the signal to be captured when the ultrasound pulse echo is received.
Unfortunately part of the current SIl which the measurement signal generates flows through the capacitor 02 which is connected in parallel for temperature compensation, and the capacitor 02' of the equivalent circuit diagram, and is therefore not available for evaluation.
The parallel capacitor 02 has a value of about 2 to 10 nF, corresponding to an alternating current resistance of about 400 Q. The input of the measurement amplifier 30 has comparatively very high resistance, for which reason the greater part of the measurement signal 311 remains in the sensor 10, and/or is short-circuited by the parallel capacitor 02.
Fig. 5 shows the distribution of the measurement currents SIl and 512 when the voltage is measured at the sensor 10.
Fig. 6 shows the course I of the current 311 through the parallel capacitor 02, compared with that of the current 312 which flows in the amplifier stage of the amplifier 30, depending on the time t for a time t2 > ti. The current 311 through the parallel capacitor C2 is significantly greater than the effective current 312 in the measurement amplifier 30.
Disclosure of the invention
An ultrasound measurement system for detecting an obstacle by means of at least one ultrasound sensor to generate a measurement signal from an ultrasound pulse which is reflected from the obstacle and received by the ultrasound sensor is created. The ultrasound measurement system includes a measurement stage, which provides a virtual earth at one input, the input of the measurement stage being connected to the output of the ultrasound sensor. The ultrasound measurement system according to the invention also includes an evaluation unit, which is designed to generate the measurement signal on the basis of an evaluation of the current flowing into the measurement stage.
According to the invention, a method, which is carried out by means of an ultrasound measurement system according to the invention, of detecting an obstacle by means of ultrasound is also provided, at least one ultrasound pulse being generated and emitted, and at least one measurement signal being generated from at least one ultrasound pulse which the obstacle reflects and the ultrasound sensor receives. The measurement signal is generated by evaluating the current which flows into the measurement stage while the input of the ultrasound sensor, is connected to earth.
The subclaims show preferred embodiments of the invention.
By the use according to the invention of the measurement stage, which provides a virtual earth, low-resistance current measurement is carried out to generate the measurement signal, instead of measuring the voltage which the ultrasound sensor generates. Because of this, the greatest part of the signal which the ultrasound sensor generates acts on the ultrasound measurement system. This improves the signal-to-noise ratio significantly, in particular up to a factor of 200. Since in the case of the ultrasound measurement system according to the invention there is no high pass filter before the input of the measurement stage, this ultrasound measurement system reacts very quickly to current changes and can be implemented more easily.
In a specially advantageous embodiment of the invention, the measurement stage includes an operational amplifier, the first input of which forms the input of the measurement stage, and the second input of which is connected to earth.
Implementation of the measurement stage according to the * invention using an operational amplifier with a virtual earth is specially simple and inexpensive.
The ultrasound sensor according to a further development of * the invention also includes a piezo element, which in particular is connected in parallel to a capacitor with the reverse temperature coefficient of the piezo element.
Preferably, the ultrasound sensor, which generates the measurement signal, is activated by means of an activation source to emit an ultrasound pulse.
By use of the measurement stage according to the invention, which provides a virtual earth, low-resistance operation of the ultrasound sensor is made possible for activation and measurement. For this reason, the effect of the alternating current resistance of the capacitor, which is connected in parallel to the piezo element, is reduced, and the measurement circuit becomes almost independent of this capacitor, which is connected in parallel.
Additionally, the resonant frequency of the ultrasound sensor remains largely independent of temperature.
Temperature compensation by means of the expensive capacitor, which is connected in parallel to the piezo element, can be omitted. In this case, the parallel capacitor consists merely of the capacitor of the equivalent circuit diagram of the piezo element, said capacitor being connected in parallel to the series circuit of a coil, a capacitor and a resistor. The result according to the invention is identical resonant frequencies of the ultrasound sensor on excitation and measurement.
In the measurement process according to the invention, the ultrasound sensor is short-circuited, in particular by the activation *source at the input. The current through the sensor passes through the virtual earth of the measurement stage, and thus causes a control reaction at the output of the operational amplifier when an operational amplifier is used to generate the virtual earth.
During the excitation of the ultrasound sensor by means of the activation signal which the activation source generates, it can happen that the virtual earth is incapable of compensating for the comparatively high currents. Preferably, therefore, between the input of the measurement stage and earth, i.e. between virtual and "true" earth, a pair of antiparallel diodes is connected.
During the excitation, the measurement current flowing through the sensor can become too great for the virtual earth. This can happen, in particular, if an operational amplifier is used to generate the virtual earth. The operational amplifier which generates the virtual earth then goes into limitation. The earth point changes so that current flow occurs in the antiparallel diodes.
The current which the sensor excites thus flows essentially from the activation source, which in particular has a voltage source, through the ultrasound sensor and through the diodes. Thus the greater part of the activation voltage is available for excitation, since at the diodes only a small voltage falls. The cause of the high current during excitation is not the coil but the charge reversal of the parallel capacitor.
When the excitation is overt the current flow falls sharply. The voltage source now has a level of zero volts.
Because of the virtual earth, the sensor is now short-circuited. Every current flow is diverted through the virtual earth. In this way, at the output of the operational amplifier, which forms the measurement stage, a voltage value which generates a current which is precisely opposite to the sensor current is set up.
The antiparallel diodes via which the charge reversal currents of the parallel capacitor flowed during excitation have no effect on the measurement circuit. Because they are connected between true earth and virtual earth, no current flows through the diodes during the measutement.
The measurement signal at the output of the ultrasound sensor is available without delay relative to the activation signal.
In a specially advantageous embodiment of the ultrasound measurement system according to the invention, the evaluation unit is designed to measure a measurement current flowing through a coil of the equivalent circuit diagram of the piezo element (or ultrasound sensor), in particular during the activation of the ultrasound sensor which generates the measurement signal.
The current which flows through the coil can be measured during the activation of the ultrasound sensor, since the charge reversal currents which flow through the parallel capacitor are comparatively short, in particular if the latter includes no capacitor which is provided for * temperature compensation.
Ln a specially advantageous embodiment of the invention, the ultrasound system is designed to generate a defined ultrasound emission by evaluating the measurement current which flows through the coil of the equivalent circuit diagram of the piezo element (or ultrasound sensor) during the activation of the ultrasound sensor which generates the measurement signal.
By measuring the current through the coil during excitation, the currently generated sound pressure can be deduced. This makes it possible to generate a defined sound emission with multiple sensors with tolerances.
Additionally or alternatively, the ultrasound measurement system according to the invention can be designed to generate active attenuation of the ultrasound sensor, in particular by counter-activation, by evaluating the measurement current flowing through the coil of the equivalent circuit diagram of the ultrasound sensor during or after the activation of the ultrasound sensor which generates the measurement signal, in particular during a reverberationtime of the ultrasound sensor.
Here, for active attenuation of the ultrasound sensor, the property of the ultrasound measurement system according to the invention, that it generates only a small phase rotation during the measurement, is exploited. In this case, the activation signal to be generated for active attenuation can be derived specially easily from the measurement signal or measurement current, since the phase rotation which the measurement generates is non-existent or inconsiderable. The measurement according to the invention is also faster because of the omission of one or more high pass filters at the input, so that generation of the activation signal for active attenuation is simplified.
Advantageously, the input of the measurement stage is connected via a second resistor to the output of the ultrasound sensor. In particular, the first input of the operational amplifier which forms the measurement stage is connected via a third resistor to the output of the operational amplifier.
According to the invention, a driver assistance system with an ultrasound measurement system according to the invention is given. The driver of such a vehicle can then be warned early if an obstacle is detected. In particular, the driver assistance system according to the invention can be designed to intervene ii) the vehicle dynamics if an obstacle is detected. In this way, the danger of the vehicle colliding, in particular during parking, is significantly reduced.
Brief description of the drawings
Below, embodiments of the invention are described in detail, with reference to the accompanying drawings.
Fig. 1 is the equivalent circuit diagram of a piezo element of an ultrasound sensor according to the
prior art,
Fig. 2 is the time-dependent voltage course at the ultrasound sensor from Fig. 1, which is fitted in an ultrasound measurement system according to the priot art, Fig. 3 is the circuit diagram of the measurement circuit of the ultrasound sensor according to the prior art, Fig. 4 is the time-dependent voltage course of an activation signal and the measurement signal for
the ultrasound sensor according to the prior art,
Fig. 5 shows the current flow in the circuit diagram of Fig. 3, Fig. 6 is the time-dependent course of the current through the capacitor which is connected in parallel to the piezo element, compared with the current in the measurement amplifier for the
ultrasound sensor, according to the prior art,
Fig. 7 is the circuit diagram of the measurement circuit of the ultrasound sensor according to a first embodiment of the invention, Fig. S is the time-dependent voltage course of an activation signal for the ultrasound sensor according to the first embodiment of the invention, Fig. 9 is the time-dependent course of the current through a coil of the equivalent circuit diagram of the piezo element during and after the activation for the ultrasound sensor according to the first embodiment of the invention, Fig. 10 is the tine-dependent course of the current through the aritiparallel diodes for the ultrasound sensor according to the first embodiment of the invention,.
Fig. 11 is the time-dependent course of the current through the coil of the equivalent circuit diagram of the piezo element during and after activation, compared, with the current which flows into the rileasurement stage, according to the first embodiment of the invention, and Fig. 12 is the time-dependent voltage course of the activation signal and measurement signal at the output of the measurement stage according to the first embodiment of the invention.
Embodiments of the invention In Fig. 7, the circuit diagram of the measurement circuit of the ultrasound sensor according to a first embodiment of the invention is shown.
The ultrasound measurement system according to the invention and the first embodiment of the invention includes an amplifier 30, which as a measurement stage according to the invention includes an operational amplifier 35, which provides a virtual earth at its first input 36. The operational amplifier 35 is connected at its first input 36 via a second resistor RB to the output 37 of the ultrasound sensor 10. Also, between the first input 36 and the output 39 of the operational amplifier 35, a third resistor R6 is connected. The second input of the operational amplifier is at earth 40.
In the measurement process, the sensor 10 is short-circuited at the input by the activation source V2, which in particular includes an H bridge. The current through the sensor 10 must pass through the virtual earth 36, and thus causes a control reaction at the output 39 of the operational amplifier 35.
During the excitation of the sensor 10, the virtual earth 36 is incapable of compensating for the comparatively high currents. As a remedy, between the virtual earth 36 and true'T earth 40, a pair of antiparailel diodes Dl, D2 is connected.
In Fig. 8, the voltage course U of an activation voltage SU for the ultrasound sensor according to the first embodiment of the invention, depending on the time t, is shown for a time t3 > t2.
The sensor 10 is excited at its input by the voltage source V2 with the signal SU shown in Fig. 8.
In Fig. 9, the current course I of the current S13 which flows for the ultrasound sensor 10 through a coil Li of the equivalent circuit diagram of the piezo element according to the first embodiment of invention, depending on the time t, is shown during and after the activation for the period t3. The current 313 through the coil Li is caused by the activation voltage SQ with which the ultrasound sensor 10 is excited at the input by the voltage source V2.
In Fig. 10, the current course I of the current 514, 514' which flows through the antiparallel diodes Dl, 02 according to the first embodiment of the invention, depending on the time t, is shown for the period t3.
During the activation, the current 512 which flows through the sensor 10 is too great for the virtual earth, and therefore the operational amplifier 35, which generates the virtual earth, goes into limitation. The earth point 36 iS changes so that current flow 514, 314' occurs in the antiparailel diodes Di, D2.
The current which the sensor 10 excites thus flows essentially from the voltage source V2 through the sensor 10 and the diodes Di, D2. Thus, for example, 0.7 \1 less is available for excitation. This is comparatively little in view of the very high voltage SQ during excitation, which for example has an amplitude of about 20 V. The cause of the high current during excitation is not the coil Li but the charge reversal of the parallel capacitor 02.
When the excitation is over, the current flow falls sharply. The voltage source V2 has now reached a level of zero volts. Because of the virtual earth 36, the sensor is now short-circuited. Every current flow is diverted through the virtual earth 36. In this way, at the output of the operational amplifier 35, a voltage value Ui which together with the third resistor R6 generates a current which is precisely opposite to the sensor current S12 is set up.
This voltage value Ui is used as the measurement signal, or is optionally amplified via further amplification stages which are implemented as voltage amplifiers, to generate the measurement signal t33.
In Fig. 11, the current course I of the current 513 which flows through the coil Ll of the equivalent circuit diagram of the piezo element during and after activation, compared with the current S12 which flows into the measurement stage, i.e. is discharged to the virtual earth, according to the first embodiment of the invention, depending on the time t, is shown for the period t3.
Fig. 11 shows the current S13 through the coil Li and the current 512 through the second resistor R3, by which the operational amplifier 35 is connected to the ultrasound sensor 10. From Fig. 11, it can be seen that almost the whole coil current 513 flows into the measurement circuit 35.
The diodes Dl, 02, via which the charge reversal currents of the parallel capacitor 02 flowed during excitation, have no effect on the measurement. Because they are connected between true earth 40 and virtual earth 36, no current flows through the diodes Dl, D2 during the measurement.
In Fig. 12, the voltage course U of the activation signal SU and the amplified measurement signal 503 at the output 03 of the amplifier 30 for the ultrasound sensor 10, according to the first embodiment of the invention, depending on the time t, is shown for the time t3.
In Fig. 12, it can be seen that the measurement signal (output signal) 303 is available without delay. It is even possible to measure the current 313 through the coil Li during the activation, sincethe charge reversal currents which flow through the parallel capacitor C2 flow for a comparatively short time. By measuring the coil current 313 during excitation, the currently generated sound pressure can be deduced. This makes it possible to generate a defined sound emission with multiple sensors with tolerances.
The parallel capacitor C2 is ineffective during activation and measurement, and makes itself noticeable only by the currents 314, 314' in the diodes Dl, D2 during activation.
Temperature compensation can be omitted. It is also now possible to change the parameters of the piezo layer without this having great effects on the measurement circuit.
Further amplification stages can still be implemented as voltage amplifiers.
In addition to this written disclosure, reference is hereby made to what is shown in Figs. 1 to 12, for further
disclosure of the invention.
GB1208883.7A 2011-05-19 2012-05-18 Ultrasound measurement system and method of detecting an obstacle by means of ultrasound Expired - Fee Related GB2491043B (en)

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CN (1) CN102788981B (en)
DE (1) DE102011076117B4 (en)
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GB (1) GB2491043B (en)
IT (1) ITMI20120789A1 (en)

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DE102017203136A1 (en) * 2017-02-27 2018-08-30 Robert Bosch Gmbh Sensor device with a sensor for performing an environment detection by means of sound waves

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FR2975503A1 (en) 2012-11-23
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KR20120129810A (en) 2012-11-28

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