Ultrasonic proximity switch

Abstract

Provided is an ultrasonic proximity switch. Apparatus and methods for identifying an actuator by a sensor by applying sound to the actuator are shown and described. The device is particularly used in security applications. The sensor and the actuator can move relative to each other, and the sensor comprises a sound wave transmitter, a sound wave receiver and a calculation unit. The sound wave transmitter is configured to transmit sound waves in the direction of the actuator. The sound wave receiver is further configured to receive the sound wave reflected from the actuator and to convert it into an analog signal. And the calculation unit converts the analog signal into a digital signal, and realizes the identification of the actuator by balancing the digital signal with a reference signal.

Description

Technical Field

[0001] The invention relates to a device for detecting an actuator by means of a sensor according to the preamble of claim 1 and to a method for detecting an actuator by means of ultrasound according to claim 18 . Background Art

[0002] Ultrasonic sensors are currently used, for example, for distance measurement. Ultrasonic waves are emitted by a transmitting source, hit an obstacle, and are reflected back in the form of ultrasonic echoes in the direction of the sensor, where they are received by at least one receiver. The distance between the sensor and the obstacle is determined using the time measured between the transmission and reception of the ultrasonic wave. The information provided by the ultrasonic sensor is therefore limited to whether an object is present and at what distance the object is from the ultrasonic sensor. In order to improve the measurement quality, the ultrasonic sensor can have multiple transmitting sources and multiple receivers.

[0003] In security applications, ultrasonic sensors are rarely or even not used today. One disadvantage of ultrasonic sensors is that they rely on reflected sound waves or echoes, which are sensitive to external influences such as temperature. Another disadvantage is the increased system complexity for detecting small three-dimensional structures.

[0004] Chinese patent application CN114758367 discloses a fingerprint recognition device, which is arranged under a pressure plate. The recognition device includes an ultrasonic unit, a piezoelectric layer, a first electrode located above the piezoelectric layer, and a second electrode located below the piezoelectric layer. The ultrasonic unit is used to send ultrasonic signals to the finger and receive ultrasonic recognition signals sent back from the finger. There is a silicon substrate with a thickness of about 50μm under the ultrasonic unit, and the silicon substrate has a switch unit for generating ultrasonic signals and processing ultrasonic detection signals. A piezoelectric layer with a thickness between 4 microns and 20 microns is applied to the silicon substrate, which produces a resonant frequency between 8MHz and 26MHz. Advantageously, a connecting layer is provided between the ultrasonic unit and the pressure plate.

[0005] When fingerprint recognition is performed, the circuit unit generates an excitation signal, thereby causing the piezoelectric layer to vibrate. The ultrasonic signal generated thereby is transmitted to the finger and reflected. Based on the inverse piezoelectric effect, a potential difference is generated between the first electrode 112 and the second electrode 113 to obtain a corresponding electrical signal. The electrical signal is processed to obtain the fingerprint pattern of the finger.

[0006] GB2529484 discloses an analysis device having an input for receiving ultrasonic data related to a contact surface between a first and a second element in frictional contact and an output for outputting data related to at least one contact stress in the first element or a contact load applied to the first element. In a processing section, the ultrasonic data are processed to determine ultrasonic runtime data and output data are derived. The propagation direction of the ultrasonic wave has a maximum component perpendicular to the contact surface. The processing for determining the ultrasonic runtime data and the determination of the ultrasonic wave flight time are performed independently of a phase shift, which depends on the contact conditions at the contact surface. Summary of the invention

[0007] One object of the present invention is therefore to provide a device for detecting actuators by means of sound waves which is cost-effective both in production and in use and is robust with respect to the sensitivity of the sound wave sensor to external influences and changes in the actuator to be detected.

[0008] This object is achieved by means of a device for identifying an actuator by applying sound waves to the actuator via a sensor, having the features of patent claim 1.

[0009] The device is used in particular as an ultrasonic proximity switch in safety applications. The sensor is movable relative to the actuator and comprises at least one sound wave transmitter, at least one sound wave receiver and at least one computing unit. The sound wave transmitter is arranged to transmit sound waves in the direction of the actuator. The sound wave receiver is designed to receive the sound waves reflected by the actuator and convert them into analog signals. The computing unit converts the analog signal into a digital signal and realizes the recognition of the actuator by balancing it with a reference signal.

[0010] The computing unit has a reference signal stored in a memory, which is usually associated with an actuator. The sensor is arranged to emit sound waves and to receive the reflected sound waves. By balancing the reflected sound waves with the reference signal already stored in the computing unit, the computing unit can determine whether these sound waves are reflected by the actuator associated with the reference signal. The device can identify and, if necessary, recognize the actuator to which the sound waves are applied by means of the sensor and the signal received by the sensor. The device can determine whether the actuator is in a certain position relative to the sensor. For this purpose, the actuator can be located not only adjacent to the sensor but also at a certain distance from the sensor. When used in safety applications, the cooperation between the sensor and the actuator has a safety-related function. Successful identification of the actuator enables the sensor to determine, by means of the computing unit, whether the taught actuator is in the set position, which can be equivalent to a guarantee of the safety of the installation. For example, the closed state of a door or window can be observed with the help of the device. The actuator can be arranged in the door or window, while the sensor can be placed in the frame, or vice versa. Positive recognition by the actuator only occurs when the door or window is completely closed and the distance between the door or window and the frame is minimal, which in turn is equivalent to the closed state of the door or window.

[0011] The reference signal contains information for identifying the actuator. The requirement for the reference signal is that it must be able to be balanced with the measured signal. The reference signal can be stored in any form in the computing unit, whereby the type or form of the reference signal has no limiting effect on the subject matter of the invention. It is conceivable that the reference signal is in the form of a time function, a table or a diagram, which in this case involves a non-exhaustive list of data reconstruction possibilities. At least the correlation between time and amplitude must be contained in the reference signal.

[0012] The stored reference signal or one or more copies thereof can be adapted to changing environmental conditions. To this end, the copies of the reference signal can be updated at predefined time intervals or according to other criteria for the identified, recognized and applied actuators.

[0013] When rebalancing the reflected sound waves, the original reference signal as well as the updated reference signal will then be employed.

[0014] Preferably, the actuator has a three-dimensional pattern, by which the sound waves are reflected and changed. This makes it possible to realize different actuators with similar structures, wherein the actuators are distinguished from each other only by the three-dimensional pattern. At the same time, the three-dimensional pattern helps to more reliably determine the actuator, in that the first three-dimensional pattern is significantly different from the three-dimensional patterns of other actuators, which further increases the reliability and tamper-proofness of the identification of the actuator.

[0015] The sensor preferably comprises two computing units, each of which has access to a reference signal. In principle, the computing units can independently carry out the conversion to the digital signal, or only one analog-to-digital converter can also be provided. The use of two computing units can serve as a check in that further steps are only carried out if both computing units show the same result regarding the agreement of the measured signal with the reference signal. The conversion by the two computing units can also be carried out independently of one another in different ways, for example using technically different analog-to-digital converters (A / D converters), integrated in a microcontroller (MCU) or externally as a dedicated module. The difference can also be achieved using the sampling frequency. This increases the safety of the conversion function to the digital signal during operation.

[0016] The sound waves emitted by the sensor reach the three-dimensional pattern via the leading section and, after being reflected at the pattern, travel the same path in the opposite direction. The leading section between the sensor and the pattern has a minimum length coordinated with the sensor. The lower limit of the leading section is used to ensure that after the sound wave is emitted by the sensor, a certain time passes until the reflected wave is received by the receiver. The duration also has a lower limit, which must not be lowered when the transmitter and the receiver are composed of the same components. In this embodiment, the membrane used to generate the sound wave is also used to receive the reflected wave. The minimum time is defined here by the duration required for the membrane to return to a static state after excitation.

[0017] The actuator preferably has a contact surface for the sensor, wherein the three-dimensional pattern is arranged in the actuator and is arranged at a distance from the contact surface. The pattern (code) is at least at a distance corresponding to the leading section from the contact surface. The actuator can be designed to establish contact with the sensor. This contact should preferably be carried out via the contact surface of the actuator. This makes it possible to guide the sound waves from the sensor into the actuator and return from the actuator to the sensor. The ultrasonic transducer of the sensor contacts the actuator on the provided contact surface. The pattern of the actuator is then located downstream of the leading section inside the actuator - that is, relative to the contact surface or at a distance from the contact surface. By arranging the three-dimensional pattern opposite to the contact surface, the distance between the pattern and the contact surface is selected to be as large as possible.

[0018] In a preferred embodiment of the device, the actuator is arranged relative to the sensor in such a way that the acoustic transmitter of the sensor is aligned with the pattern of the actuator when the actuator and the sensor are in contact or when the sensor and the actuator are at the minimum required distance from each other. The sensor is used to identify the actuator and its three-dimensional pattern. In certain applications, it is sufficient to identify the actuator only when the sensor and the actuator are in contact or when the distance between the sensor and the actuator is minimal. This reduces the window in which the actuator can be identified by the sensor and thus leads to a higher safety threshold when the device is used in safety applications. The actuator can only be successfully identified when the sensor and the actuator are at the smallest possible distance.

[0019] In another preferred embodiment, the sound wave transmitter and the sound wave receiver must be adjacent to the contact surface of the actuator in order to identify the actuator. In other words, the sensor must be in contact with the actuator in order to successfully identify the actuator. In this application, this feature can ensure that the door closes seamlessly. As soon as the door opens a small gap and thus, for example, the safety of the facility is no longer guaranteed, this can be detected by the sensor.

[0020] The sound wave receiver preferably receives the reflected sound waves in their entirety. Receiving in their entirety means that the sound wave receiver receives the reflected sound waves locally at one location and converts them into a single signal. As a result, the device can be operated with only one sensor, which simplifies production, reduces space requirements and reduces costs.

[0021] The calculation unit has the task of creating a balance between the received signal and the reference signal. The processing speed of the calculation unit for creating this balance is fastest when the calculation unit has as direct access to the reference signal as possible. Preferably, the reference signal is stored in the calculation unit. This enables the calculation unit to have the most direct access to the reference signal. The fast processing speed of the calculation unit is particularly important in security applications.

[0022] The pattern of the actuator ideally has a three-dimensional structure. The advantage of a three-dimensional structure is that sound waves undergo significant changes when reflected, which makes it easier to infer the actuator from the reflected sound waves. At the same time, the three-dimensional structure offers more modification possibilities to create different three-dimensional patterns.

[0023] In another preferred embodiment, the pattern comprises two surfaces facing the contact surface of the actuator, which are at different distances from the contact surface. The division of the pattern into two surfaces, each at different distances from the contact surface, results in a three-dimensional structure. At the same time, this division into two surfaces with different distances from the contact surface results in a simple construction with a large number of variation possibilities by varying the distance of one or both surfaces.

[0024] As mentioned above, the reflected sound waves are preferably received and evaluated in their entirety, these sound waves being reflected by both faces of the pattern. Evaluating the sound waves in their entirety also has advantages in the pattern design. Therefore, the difference in the distance between the two faces and the contact face can be very small. Preferably, the difference in the distance between the two faces is less than 1 mm, preferably less than 0.5 mm, more preferably less than 0.3 mm, but greater than 0.01 mm, and preferably greater than 0.05 mm.

[0025] Advantageously, the calculation unit identifies the pattern of the actuator by balancing with a reference signal.The calculation unit is responsible for creating a balance between the measured signal and the reference signal.

[0026] The computing unit is responsible for identifying the actuator. Preferably, the computing unit generates a binary signal based on the identification of the actuator. This binary signal allows a decision to be made, for example, whether the actuator is located at the transmitter / receiver. This can be very important for safety-related applications, since a decision is thereby made by the device that describes a clear state of the device. For example, such a state can be a closed safety door.

[0027] In a further preferred embodiment, the computing unit generates a shutdown signal if the actuator is not successfully identified. The generation of the shutdown signal is often very important in safety applications. The identification of the actuator constitutes the basic state for ensuring safety. As long as the actuator is identified, the safety of the system is guaranteed. The desire to detect dangerous situations as quickly as possible and to transmit them to the control unit can be met by generating the shutdown signal as quickly as possible. The generation of the shutdown signal by the computing unit results in a very fast reaction to any changes in the association between transmitter and actuator.

[0028] Ideally, the sound wave transmitter and the sound wave receiver are arranged at the same position, in particular they use the same membrane to transmit and receive the sound waves. Therefore, the output point of the sound wave coincides with the receiving point of the reflected sound wave. Usually, the reflected sound wave is received from the direction of the sound wave emission. By arranging the transmitter and the receiver at the same position, the sensor can have a more compact structure. If the transmitter and the receiver use the same membrane, it is also possible to use an element such as a transducer including a transmitter and a receiver. Using the same membrane for the transmitter and the receiver results in lower manufacturing costs for the sensor and the entire device. Preferably, a piezoelectric ultrasonic transducer is used, which can be used as both a transmitter and a receiver.

[0029] Preferably, the sound wave transmitter generates sound waves with a frequency between 300kHz and 20MHz. Only sound waves fall within this range. Using this frequency range does not cause an undesirable burden on the environment.

[0030] The actuator is preferably made of plastic. Preferably, a plastic with a low and temperature-constant sound velocity is used, such as POM (polyoxymethylene). Preferably, a plastic is used in which the sound propagation of the material is less than 2500 m / s and the influence of temperature changes is less than 2 m / s per degree Celsius. Plastic offers the advantage that it facilitates the production of complex shapes and structures, such as may occur, for example, in the pattern of the actuator. At the same time, plastic has the desired property of reflecting sound waves very well, so that they can be received and evaluated in their entirety.

[0031] Another aspect of the invention relates to a method for identifying an actuator by means of sound waves. The sound waves are emitted by a sound wave transmitter and received by a sound wave receiver. The method comprises: sending a sound wave to the pattern of the actuator and receiving the sound wave reflected by the pattern of the actuator by the sound wave receiver. The received sound wave is converted into an electrical signal. Furthermore, in the method according to the invention, the signal is balanced with a reference signal stored therein by a computing unit, and a binary signal is generated by the computing unit as a result of the balance, and the identification of the actuator is determined based on the binary signal. Balancing the measured signal with the reference signal allows the consistency of the two signals to be determined. If the consistency shows a predefined similarity, the actuator to which the sound is applied is positively identified as the taught reference actuator. Thus, for example, it can be determined whether the taught (reference) actuator is adjacent to the sensor. Advantageously, the reflected sound wave is received in its entirety by the sound wave receiver. This means that a single sound wave receiver receives the reflected sound wave and generates a single measurement signal based on the reflected and received sound wave. This allows the structure of the sensor to be designed as simply as possible, because the sensor only needs to have one sound wave transmitter and one sound wave receiver.

[0032] Preferably, in a first step, a reference signal is generated by teaching the actuator. Teaching the actuator describes carrying out a reference measurement. For this purpose, the actuator is placed at the desired position and sound waves are applied by a sensor. A receiver in the sensor receives the reflected sound waves and forms a signal based on the measured sound waves, which forms the reference signal. The reference signal can thus be understood as an image of the actuator being taught.

[0033] The method is preferably used in safety applications, in which a warning signal or a safety release is generated in the event of unsuccessful identification of the actuator. The method can be used to check whether the actuator is in the position provided for this purpose and whether it is a taught actuator suitable for use in safety applications. The state of a door or window can be reliably monitored using this method, and a warning or shutdown signal can be generated immediately during the opening process. An advantage in this respect is also the high sensitivity of the method according to the invention. If, for example, the actuator deviates only slightly from the original state, i.e. in the range between 0.1 mm and 1 mm, the reflected sound waves can quickly deviate from the reference signal. The high sensitivity of the method results in low tolerances for the device being checked, which in turn leads to a precise check or check of the device to be monitored.

[0034] Advantageously, the actuator has a contact surface and the sound wave transmitter is located on the contact surface for identifying the actuator. When the sound wave transmitter is located on the contact surface of the actuator, the sound waves propagate only in the housing of the actuator. Therefore, there are no interfering influences of the environment on the sound waves and their measurement, such as, for example, caused by different distances between the actuator and the sensor or the state of the air between the actuator and the sensor. Providing the contact surface allows interference-free measurement as long as the contact between the sensor and the actuator is intact.

[0035] Preferably, the sonicator emits sound waves which are oriented perpendicularly to the contact surface. This allows the volume of the actuator to be used most effectively, which in turn allows for better differentiation of reflected sound waves.

[0036] The optional features can be implemented in any combination as long as they are not mutually exclusive. In particular, where preferred ranges are specified, other preferred ranges can be obtained by combining the minimum and maximum values ​​within these ranges. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The invention is explained in detail below with reference to the accompanying drawings in the form of schematic diagrams. In a schematic view not to scale:

[0038] Figure 1 A cross-sectional view of a device according to the invention with a sensor is shown, the device comprising an acoustic wave sensor and an acoustic wave receiver and an actuator;

[0039] Figure 2 A side view of the actuator is shown;

[0040] Figure 3 six graphs showing comparison of measurement signals of six actuators with a reference signal; and

[0041] Figure 4 A diagram showing the correlation curves for different actuators is shown. DETAILED DESCRIPTION

[0042] In the following, the same reference numerals represent identical or functionally identical elements (in different figures). Additional primes may be used to distinguish elements that are similar or functionally identical or functionally similar in another embodiment.

[0043] exist Figure 1 1 shows a view of a device 11 which consists of two separate components. The first component is a sensor 13. The sensor 13 comprises an acoustic transmitter 17 and an acoustic receiver 19 which are connected to an analog front end 21. Two channels 23, 25 lead outward from the analog front end 21. The channels 23, 25 each have a computing unit 24, 26. The acoustic transmitter 17 (also referred to as transmitter for short) and the acoustic receiver 19 (also referred to as receiver for short) are arranged at approximately the same position on the front side of the sensor 13. The transmitter and the receiver can also be the same device, wherein in this case the difference between the transmitter and the receiver lies only in the function of transmitting and receiving acoustic waves. Preferably, a piezoelectric sensor is used as the acoustic transducer which operates at a frequency between 300 kHz and 20 MHz.

[0044] The second component is constituted by the actuator 27. Figure 1In the embodiment, the actuator 27 is in contact with the transmitter 17 and the receiver 19. The side of the actuator 27 that touches the transmitter 17 and the receiver 19 is the contact surface 29 of the actuator. A pattern 31 is provided in the actuator 27 at a side opposite to the contact surface 29 and spaced from the side. Figure 1 In the example shown in , the pattern 31 is formed by steps. Thus, the pattern 31 has two faces 33, 33', which face the contact surface 29 and are parallel to each other and to the contact surface. The difference between these two faces 33, 33' is their distance from the contact surface 29. This difference can be between 0.05 mm and 3 mm, preferably between 0.1 mm and 2 mm, and particularly preferably between 0.5 mm and 1.5 mm.

[0045] The transmitter 17 is provided for emitting a sound wave 35 in the direction of the actuator 27. If the actuator 27 is in contact with the transmitter 17, the sound wave 35 emitted by the transmitter propagates in the actuator up to the pattern 31. The pattern 31 of the actuator limits the propagation of the sound wave in the actuator. The sound wave 35 strikes the pattern 31 and is reflected by it. The reflected sound wave 35 again travels the same path in the opposite direction and reaches the receiver 19. The receiver 19 has a membrane, which is vibrated by the reflected sound wave. The vibration of the membrane of the receiver is recorded as an analog signal. In the analog receiving circuit (front end) 21, the analog signal can be further processed, for example by amplifying or filtering it. After processing in the front end 21, the analog signal is transmitted to the respective computing units 24, 26 in the two evaluation channels 23, 25.

[0046] The two computing units 24, 26 each have a memory in which a reference signal is stored. After receiving the electrical signal from the receiver, each computing unit 24, 26 compares it with the stored reference signal and determines the similarity or degree of agreement between the two signals. If the agreement exceeds a certain degree or value, this means that the previously taught actuator 27 is adjacent to the sensor.

[0047] The reference signal can be generated in different ways. One possibility is to perform a reference measurement to generate the reference signal before the device is put into operation. For this purpose, the actuator 27 is guided to the sensor so that the transmitter 17 and the receiver 19 of the sensor are located on the contact surface 29 of the actuator. The application of sound waves to the actuator 27 realizes the following signal in the receiver 19, which is transmitted to the calculation units 24, 26 and is stored by them as a reference signal after optional signal processing. Thus, the actuator 27 is read by the sensor 13 using this reference measurement.

[0048] Figure 2A possible design of an actuator 27 suitable for the device according to the invention is shown in FIG. According to the exemplary embodiment shown, the actuator comprises a housing 28 in which a three-dimensional pattern 33, 33' is integrated. However, it is also possible in principle to produce the actuator from a solid material in which the three-dimensional pattern is embedded. In this case, the housing of the actuator is designed as a cylinder with a stepped bottom surface 33, 33', wherein the cylinder can be designed as a hollow or solid cylinder.

[0049] One side of the actuator serves as the contact surface 29. The side opposite to the contact surface 29 serves as the pattern 31. The distance between the contact surface 29 and the pattern 31 is divided into two sections, namely the so-called leading section 39 and the variable section 40. The leading section 39 is adjacent to the contact surface 29 and has the same length for all actuators 27. The variable section 40 forms a section from the leading section 39 to the pattern 31. The leading section 39 is the smallest dimension of the distance between the contact surface 29 and the pattern 31.

[0050] It is possible to produce a plurality of actuators 27 which have respectively different distances between the pattern surface 33 and the contact surface 29 and which correspondingly respectively generate different reflections of the sound waves 35 , which in turn lead to different signals.

[0051] The sound wave 35 is received in its entirety by the receiver and transmitted as an analog signal. The analog signal can be processed in the analog front end 21 to simplify the comparison between the signals. The amplitude of the signal is plotted against the measuring time, thereby forming a time function of the signal. The identification of the actuator 27 is carried out with the help of the created function of the balanced signal. The balancing is usually carried out here by comparing the measured signal 41 with a reference signal 43. The reference signal can be generated in different ways.

[0052] A first method for generating the reference signal 43 is to calculate an average value, for which each data point in the measurement sequence is averaged over a plurality of measurement sequences. In this case, the choice of the measurement for calculating the average value can remain variable, so that when the measurement is performed, the measured values ​​obtained are continuously incorporated into the calculation of the average value. The format of the measured signal 41 and the reference signal 43 must be consistent so that the two signals can be compared. To ensure this, the signals can be subjected to digital signal processing. The reference signal 43 can then be compared with the measured signal 41, for example, by means of correlation or cross-correlation. By means of the cross-correlation, a number is calculated which shows the offset between the two signal functions. If this number approaches zero, there is a consistency of the actuator. In order to generate a binary output, a limit value can be specified for the result of the cross-correlation, below which the actuator is identified as correct. An alternative method for the cross-correlation is to use the mean square error method, in which a sum of mean squared differences is formed. The smaller the sum, the more similar the compared functions or signal profiles are to each other. In order to identify the actuator 27, a limit value must be defined here for the sum of squared differences. If the result is below this limit value, there is a similarity and the actuator is identified as positive. Typically, both the reference and measured signals are normalized before balancing is performed.

[0053] An alternative to the first method described above for creating a balance with a reference signal is to use artificial intelligence. Here, in order to identify the actuator, training data is read into the neural network. These training data must first be generated. For this purpose, the number of all different actuators 27 is produced, which are read by the sensor 13 and whose signals are stored in a database. The measurement of the read actuator 27 by the sensor 13 can be carried out under different boundary conditions, so that, for example, the contact surface 29 between the sensor 13 and the actuator 27 and the influence of the contact can be included in the training data. The data is divided into a plurality of categories, wherein the number of categories is equal to the number of different actuators plus one. The additional category is such a category in which each signal that does not belong to an actuator category in the actuator category is assigned. Therefore, each signal received by the sensor is assigned to a category. The calculation unit 24 is responsible for associating the received signal 41 with the corresponding category. The calculation unit 24 uses an artificial neural network or other AI method trained with the training data and developed a classification mechanism for this purpose. Associating the received signal 41 with the corresponding category belongs to balancing the received signal 41 with the reference signal 43.

[0054] exist Figure 3 and Figure 4 A diagram for forming the above correlation and identifying the actuator 27 is shown in FIG. Figure 3, six diagrams are shown in which the measured signal 41 of a specific actuator is plotted together with a reference signal 43. The reference signal 43 is represented here by a thick line, while the measured signal 41 is formed by a thin line in each case. In this example, the reference signal 43 is generated using an actuator 27 with a unique coding depth of 18 mm. The six diagrams show the reflected sound waves received by the receiver 19 and transmitted to the calculation unit 24 in the normalized state of the following actuators 27, which have a coding depth of 17.5 mm, 17.8 mm, 18 mm, 18.1 mm and 19 mm. For a coding depth of 18 mm, two measurement sequences were tested. Figure 4 In FIG. 4 , the maximum and minimum correlation values ​​between the measured signal 41 and the reference signal 43 of different actuators 27 are plotted. Figure 4 On the x-axis of the diagram in FIG. 2 , actuators 27 with increasing encoding depth are plotted, while on the y-axis the correlation value is indicated. An upper limit value and a lower limit value are defined for the correlation value, which are indicated in the diagram by two horizontal lines. Figure 4 The results in show that the correlation for an actuator with a coding depth of 17.8 mm to 18.1 mm is within the stated limit values. In contrast, the reference signal 43 is formed using an actuator 27 with a coding depth of 18 mm.

[0055] Another possible method in this or similar embodiments for balancing the measurement signal 41 with the reference signal 43 is to form a difference signal between the two signals. In contrast to the previously described method of associating a plurality of actuators with different classes, by forming a difference signal or other methods, a binary classification is intended. This means that the result makes a binary statement as to whether the measurement signal 41 fully agrees with the reference signal 43. In the case of complete agreement, the measurement signal 41 is equal to the reference signal 43 and the difference between the two signals is equal to zero. In the case of sound being applied to the reference actuator, the difference between the two signals may deviate from zero. Therefore, a tolerance range in the form of a threshold is defined for the difference, within which the identification of the reference actuator is still evaluated as positive. Binary classification is only used when identifying a single actuator, because it can be determined from this whether the single actuator is in the position it was in during the reference measurement at the time of the measurement. In safety applications, for example, this can be used to check the closed state of a door.

[0056] The proximity switch operates as follows: a sound wave is transmitted by exciting the ultrasonic transducer with two pulses during a predetermined first duration, which is between 0.25 μs and 5 μs depending on the operating frequency of the ultrasonic transducer. Then, the reflected sound wave is detected during a predetermined second duration, which is between 0 μs and 200 μs. Preferably, the reflected sound wave is detected only between 30 μs and 60 μs after transmission, so that the attenuation of the ultrasonic transducer after being excited by the control pulse is not included in the measurement. The current measurement window is between 55 μs and 95 μs of the received echo.

[0057] Although specific embodiments have been described above, it is obvious that different combinations of the implementation possibilities shown can be used, as long as these embodiments are not mutually exclusive.

[0058] Summary: A device and a method for identifying an actuator by applying sound to the actuator by a sensor are shown and described. The device is used in particular for safety applications. The sensor and the actuator can move relative to each other. The sensor comprises a sound wave transmitter, a sound wave receiver and a computing unit. The sound wave transmitter is configured to transmit sound waves in the direction of the actuator. The sound wave receiver is in turn configured to receive the sound waves reflected from the actuator and convert them into an analog signal. The computing unit converts the analog signal into a digital signal and realizes the identification of the actuator by balancing it with a reference signal.

[0059] Reference numerals list:

[0060] 11 Equipment

[0061] 13 Sensors

[0062] 17. Sound Wave Transmitter

[0063] 19 Acoustic Receiver

[0064] 21Analog front end

[0065] 23 First Channel

[0066] 24 First computing unit

[0067] 25 Second channel

[0068] 26 Second computing unit

[0069] 27 Actuator

[0070] 28 Shell

[0071] 29 contact surface

[0072] 31 patterns

[0073] 33 pattern reflective surface

[0074] 35 Sound Wave

[0075] 39 leading paragraph

[0076] 40 variable segments

[0077] 41Measured signal

[0078] 43 reference signal.

Claims

1. A device (11) for identifying an actuator (27) by means of a sensor (13) by applying sound waves (35) to the actuator, in particular in safety applications, wherein - the sensor (13) is movable relative to the actuator (27), The sensor (13) comprises a sound wave transmitter (17), a sound wave receiver (19) and a computing unit (24), wherein the sound wave transmitter (17) and the sound wave receiver (19) can be realized as a single component, and the sound wave transmitter (17) is configured to transmit sound waves (35) in the direction of the actuator (27), and the sound wave receiver (19) is configured to receive the sound waves reflected from the actuator (27) and convert them into analog signals, It is characterized in that The computing unit (24) converts the analog signal into a digital signal and realizes the identification of the actuator (27) by balancing it with a reference signal (43).

2. The device (11) according to claim 1, characterized in that The actuator (27) has a pattern (31), and the sound wave (35) is reflected and changed by the pattern.

3. The device (11) according to claim 1 or 2, characterized in that The sensor (13) comprises two computing units (24, 26), each of which has a reference signal (43).

4. The device (11) according to claim 2 or 3, characterized in that The actuator (27) has a contact surface (29) for the sensor (13), wherein the pattern (31) is arranged at a distance from the contact surface (29).

5. The device (11) according to any one of claims 2 to 4, characterized in that The actuator (27) is arranged relative to the sensor (13) such that the contact or distance between the sensor (13) and the actuator (27) is as small as possible, and the sound wave transmitter (17) of the sensor (13) is aligned with the pattern (31) of the actuator (27).

6. The device (11) according to claims 2 to 5, characterized in that The sound wave transmitter (17) and the sound wave receiver (19) are arranged on a contact surface (29) of the actuator (27) for identifying the actuator (27).

7. The device (11) according to any one of claims 1 to 6, characterized in that The sound wave receiver (19) receives the reflected sound waves in its entirety.

8. The device (11) according to any one of claims 1 to 7, characterized in that The reference signal (43) is stored in the calculation unit (24).

9. The device (11) according to any one of claims 2 to 8, characterized in that The pattern (31) of the actuator (27) has a three-dimensional structure.

10. The device (11) according to any one of claims 4 to 8, characterized in that The pattern (31) comprises two faces (33) facing the contact face (29) of the actuator (29), the faces being at different distances from the contact face.

11. The device (11) according to claim 10, characterized in that The difference between the distances of these two faces (33) is less than 1 mm, preferably less than 0.5 mm, more preferably less than 0.3 mm.

12. The device (11) according to any one of claims 2 to 11, characterized in that The computing unit (24) infers the pattern (31) of the actuator (27) by comparing it with a reference signal (43).

13. The device (11) according to any one of claims 1 to 12, characterized in that The computing unit (24) generates a binary signal as a function of the identification of the actuator (27).

14. The device (11) according to any one of claims 1 to 13, characterized in that The computing unit (24) generates a shutdown signal if the actuator (27) is not successfully identified.

15. The device (11) according to any one of claims 1 to 14, characterized in that The sound wave transmitter (17) and the sound wave receiver (19) are arranged at the same position, and in particular use the same membrane to transmit and receive sound waves.

16. The device (11) according to any one of claims 1 to 15, characterized in that The sound wave transmitter (17) generates sound waves (35) with a frequency of 300 kHz to 20 MHz, preferably between 350 kHz and 8 MHz and particularly preferably between 1 and 4 MHz.

17. The device (11) according to any one of claims 1 to 16, characterized in that The actuator (27) is made of a plastic that is distinguished by a low speed of sound and its low temperature dependence.

18. A method for identifying an actuator (27) by means of sound waves (35), the sound waves being transmitted by a sound wave transmitter (17) and received by a sound wave receiver (19), The following steps are involved: - sending sound waves (35) to the pattern (31) of actuators (27), - receiving, by means of a sound wave receiver (19), sound waves reflected by the pattern (31) of the actuator (27), - converting the sound waves into electrical signals (41), - balancing said signal with a reference signal (43) stored therein by means of a calculation unit (24), - a binary signal is generated by the computing unit (24) as a result of the comparison and the identification of the actuator (27) is determined based on the binary signal.

19. The method according to claim 18, characterized in that In a first step, the reference signal (43) is generated by a teach actuator (27).

20. The method according to claim 18 or 19, characterized in that The method is used in safety applications and generates a warning signal or a safety release if the actuator (27) is not successfully identified.

21. The method according to any one of claims 18 to 20, characterized in that The actuator (27) has a contact surface (29), and the sound transmitter (17) is adjacent to the contact surface (29) for identifying the actuator (27).

22. The method according to claim 21, characterized in that The sound wave transmitter (17) transmits sound waves oriented perpendicularly to the contact surface (29).

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