Method and device for determining a useful signal

Abstract

Method (300) for determining a useful signal (155), wherein the method (300) comprises the following steps: - Sampling (310) of a read sensor signal (115) with a first sampling frequency (f A1 ), to obtain a first sampling signal (135) and sampling (310) of the sensor signal (115) with a second sampling frequency (f A2 ), to obtain a second sampling signal (145), wherein the first (f A1 ) and second sampling frequency (f A2 ) distinguish; and - Detect (320) the useful signal (155) as signal components (200) of the first (135) and second sampled signal (135), wherein the signal components (200) of the first (135) and second sampled signal (145) have the same frequency (228) within a tolerance range (227).

Description

State of the art

[0001] The invention relates to a device or a method for determining a useful signal according to the preamble of the independent claims. The present invention also relates to a computer program.

[0002] It is common practice to digitize analog signals using analog-to-digital converters. The technology used so far has a general disadvantage: it can generate "valid signals" itself if there are disturbances in the power supply, ground, or signal.

[0003] This faulty behavior will be explained using a micromechanical sensor. We assume a sensor capable of detecting acceleration signals up to 2 kHz. The internal analog-to-digital converter (ADC) uses a sampling rate of 125 kHz. If electromagnetic interference (EMC interference) affects the ADC, it can be disrupted. Interference with frequencies close to the harmonics of internally used frequencies is particularly problematic, for example, interference of 124 kHz or 126 kHz at a sampling rate of 125 kHz. These two frequencies have a frequency separation of 1 kHz from the sampling rate of the example sensor. This leads to "pseudo-acceleration values" of 1 kHz each due to mixing effects (these effects are deliberately used in high-frequency mixing in radio receivers). These pseudo-signals cannot subsequently be distinguished from real signals.This effect is not limited to the first harmonic, but theoretically affects all harmonics. Disclosure of the invention

[0004] Against this background, the approach presented here comprises a method for determining a useful signal, a device that uses this method, and finally a corresponding computer program according to the main claims. Advantageous further developments and improvements of the device specified in the independent claim are possible through the measures listed in the dependent claims.

[0005] A method for determining a useful signal is presented here, the method comprising the following steps: - Sampling a read sensor signal with a first sampling frequency to obtain a first sampling signal and sampling the sensor signal with a second sampling frequency to obtain a second sampling signal, wherein the first and second sampling frequencies differ; and - Recognizing the useful signal as signal components of the first and second sampled signals, wherein the signal components of the first and second sampled signals have the same frequency within a tolerance range.

[0006] A useful signal can be understood as a signal containing useful information that is to be extracted and / or further processed. For example, a signal from a sensor can be considered a useful signal. A signal component can be understood as a portion of the signal within a specific frequency range or at a specific frequency. A tolerance range can be understood, for example, as a range around a frequency that exhibits a deviation from that frequency of a maximum of 20 percent, particularly a maximum of 10 percent. In this sense, the useful signal can be understood as that portion of the first and / or second sampled signal that is contained within a frequency range of, for example, 20 percent around a specific frequency in both sampled signals.

[0007] The approach presented here is based on the understanding that when sampling the desired signal at different sampling frequencies to obtain different sampled signals, the desired signal is contained at the (correct) frequency in each sampled signal. Furthermore, the erroneous signals resulting from the mixing of interfering frequencies with the sampling frequency should also appear at different frequencies in the individual sampled signals. Thus, a typical property of frequency mixing is exploited to detect the interfering signals. This is achieved at the cost of double sampling, which, with conventional, inexpensive signal processing units, will not result in significantly increased costs but will lead to a significant improvement in error detection.

[0008] A particularly advantageous embodiment of the approach presented here is one in which, during the sampling step, a first and second sampling frequency is used that is greater than twice the frequency of the sensor signal and / or a maximum detection frequency during the detection step. Such an embodiment offers the advantage of very precise and simple detection of interference signal components, allowing the useful signal to be determined with high accuracy.

[0009] According to a further embodiment of the approach presented here, the useful signal can be detected in the recognition step if the signal components of the first and second sampled signals have the same amplitude within a tolerance range. Such an embodiment offers the advantage that the useful signal can be unambiguously identified and distinguished from a potential interference signal. This approach exploits the fact that interference signals at different frequencies usually have different amplitudes, so that the useful signal to be determined is very likely the only signal to be processed that has the same signal amplitude in both sampled signals.

[0010] In a further embodiment of the approach presented here, the method includes a step for determining a noise signal and / or a parameter of a noise signal, wherein the noise signal and / or the parameter of a noise signal is determined using the first and second sampling frequencies, the frequency of the signal components recognized as the useful signal, and a first noise signal component contained in the first sampled signal and a second noise signal component contained in the second sampled signal. Such an embodiment offers the advantage of being able to determine further information from the values ​​already available, which can be used, for example, for a subsequent signal processing procedure for error compensation.

[0011] A further advantage is an embodiment of the approach presented here in which the method includes a step of applying a test signal to the sensor signal, wherein the test signal has a test signal frequency that differs from a frequency of the sensor signal, and in particular, wherein in the detection step the useful signal is detected when a test signal component at a frequency associated with each test signal is detected in the first and second sampling signals. Such a test signal component associated with each test signal can be expected at a frequency that can be determined by considering the sampling frequency (of the respective sampling signal under consideration) and the test signal frequency. Such an embodiment offers the advantage that the frequency of the test signal (test signal frequency) is known, so that the correct functioning of the method can be easily verified (even in the presence of interference signals with unknown frequencies).Similarly, in another embodiment of the approach presented here, a step of applying an interference signal to the sensor signal can be performed, in particular wherein the method includes a step of verifying the correct functioning of the method, wherein the verification step is successful if the first and second sampling signals contain a frequency component corresponding to the frequency of the interference signal. Such an embodiment can also be used to verify the error-free functioning of the method for determining the useful signal.

[0012] A particularly simple technical implementation of the approach presented here involves filtering a supply voltage and / or current of the device performing the method during the application step. In this filtering step, a frequency component of the supply voltage and / or current that deviates from the frequency of the useful signal is applied to the sensor signal as an interference signal. Such an embodiment offers the advantage that a filter required for filtering interference on the device's power supply lines can be used for an additional function to implement the approach presented here. Therefore, only very minor modifications to existing circuit topologies are necessary to implement this approach.

[0013] Furthermore, during the verification step, a successful execution of the filtering step can be detected if a frequency component of the supply voltage and / or supply current at a predefined filter frequency is identifiable in the first and / or second sampled signal. Such an embodiment offers the advantage that the frequency signal component at the predefined filter frequency can be clearly identified, thus making it very easy to verify the correct functioning of the approach presented here.

[0014] The useful signal can be determined with a high degree of reliability if, according to one embodiment of the approach presented here, signals from two separate circuit modules are used as the first and second sampling signals during the sampling step. These two circuit modules can each be mounted on a different circuit board. Such separation during sampling offers the advantage that, for example, the probability is very low that a signal component in the first sample caused by a hardware fault in one of the circuit modules will have a feedback effect on the corresponding signal components in the second sample, thus enabling more robust detection of the useful signal.

[0015] The method presented here can be implemented, for example, in software or hardware, or in a hybrid form of software and hardware, for example in a control unit.

[0016] The approach presented here further creates a device designed to perform, control, and implement the steps of a variant of the method presented here in appropriate facilities. This embodiment of the invention in the form of a device also allows the problem underlying the invention to be solved quickly and efficiently.

[0017] In this context, a device can be understood as an electrical device that processes sensor signals and outputs control and / or data signals accordingly. The device may have an interface, which can be implemented in hardware and / or software. In the case of a hardware-based interface, the interfaces can, for example, be part of a so-called system ASIC, which incorporates various functions of the device. However, it is also possible that the interfaces are separate integrated circuits or consist at least partially of discrete components. In the case of a software-based interface, the interfaces can be software modules, which, for example, are present on a microcontroller alongside other software modules.

[0018] Also advantageous is a computer program product or computer program with program code that can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and is used to carry out, implement and / or control the steps of the method according to one of the embodiments described above, in particular if the program product or program is executed on a computer or device.

[0019] Exemplary embodiments of the invention are shown in the drawings and explained in more detail in the following description. It shows: Fig. 1 a block diagram of a measuring system with a device according to an exemplary embodiment; Fig. 2 diagrams of signal components for determining the useful signal according to an exemplary embodiment; and Fig. 3 Flowchart of a procedure according to an exemplary embodiment.

[0020] In the following description of favorable embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and acting similarly, without repeating these elements.

[0021] Fig. Figure 1 shows a block diagram of a measuring system 100 with a device 105 according to an embodiment of the present invention. The measuring system 100 comprises a measuring sensor 110, for example in the form of a micromechanical accelerometer, which provides a measuring signal 115. However, this measuring signal 115 is often disturbed during transmission to the device 105 by interference such as electromagnetic coupling of a noise signal 120, so that when determining the pure measuring signal 115, a part of the noise signal 120 mixed into the frequency range to be evaluated by the device 105 may be erroneously recognized as part of the measuring signal 115, and thus the measuring signal cannot be detected precisely.This can have significant disadvantages when using the measurement signal 115, for example to activate personal protection systems in a vehicle, or it can completely prevent the use of the determined measurement signal 115 for a specific purpose.

[0022] In order to enable interference immunity optimization in the detection of the measurement signal 115, a sampling frequency generator 125 is used in the device 105 according to the approach presented here, which generates a first sampling frequency f A1 and a second sampling frequency f that differs from the first sampling frequency A2 The measurement signal 115, which is disturbed by the interference signal 120, is processed by a first analog-to-digital converter 130 (ADC = Analog-to-Digital Converter) using the first sampling frequency f. A1The signal is sampled to obtain a first sampled signal 135. In a second analog-to-digital converter 140, the second sampled frequency f is used. A2 The measurement signal 115, which was disturbed by the interference signal 120, was sampled in order to obtain a second sampling signal 145.

[0023] Fig. Figure 2 shows diagrams of signal components 200 of the first sampled signal 135 and the second sampled signal 145 for determining the useful signal 155. The diagrams plot the amplitude of the first sampled signal 135 and the second sampled signal 145 against the frequency. This is shown in the Fig. 2 illustrated embodiment of a measurement signal 115 (here, for example, an acceleration signal) with a frequency of 0.5 kHz, an interference signal of an EMC disturbance with a frequency of 124 kHz, a first sampling frequency of f A1 = 125 kHz and a second sampling frequency of f A2= 128 kHz. It can be seen that in both the first and second sampling signals 135 and 145 respectively, a signal component 200 occurs in the frequency range 210 (from 0 to 2 kHz) to be evaluated by the unit 150 for detection, at the frequency of 0.5 kHz of the actual measurement signal 115, whereas in the first sampling signal 135, a mixing effect 215 of the interference signal 120 of frequency 124 kHz with the first sampling frequency f A1 a first false signal (pseudo-signal) 220 of frequency 1 kHz and in the second sampled signal 145 through a mixing effect 215 of the interference signal 120 of frequency 124 kHz with the second sampled frequency f A2A second false signal (pseudo-signal) 225 with a frequency of 4 kHz occurs. The first and second false signals 220 and 225, respectively, are therefore interference signals that are not to be considered when recognizing the measurement signal 115 as the useful signal 155. In a recognition unit 150, the useful signal 155 is now recognized, according to the more detailed description below, as that part of the measurement signal 115 superimposed by the interference signal 120 which has the same frequency 228 within a tolerance range 227 (of, for example, 10%).

[0024] It is particularly advantageous if the difference between the two ADC frequencies is f A1 or f A2 is greater than twice the highest signal frequency to be processed. This prevents an interference frequency that lies exactly between the two ADC frequencies f. A1 or f A2 lies, generating a "valid signal".

[0025] In unit 150, the evaluation of the first sample signal 135 and the second sample signal 145 reveals that a signal component 200 is present in the 0.5 kHz range (for example, taking into account a 10% deviation from this value of 0.5 kHz). However, only the first sample signal 135 contains an additional signal component at a frequency of 1 kHz within the evaluated frequency range 210, which therefore cannot originate from the measurement signal 115. The component 225 in the second sample signal, which is downmixed from the interference signal 120, lies outside the evaluated frequency range 210 and has no corresponding counterpart in the first sample signal 135. It can therefore be identified as a pseudo-signal 225 resulting from mixing. The signal components 200 in the first and second sample signals 135, respectively, are...145 are thus recognizable as signal components of a real signal, so that the unit 150 outputs the useful signal 155 as the corresponding signal components 200 for recognition.

[0026] It is also conceivable that by knowing the first and second sampling frequencies f A1 or f A2 and the first or second pseudo-signal 220 or 225 identifies a frequency of the interference signal 120, so that this information can also be output by unit 150 for detection and used to avoid further interference from the interference signal 120 or to compensate for it.

[0027] In other words, the approach presented here enables noise immunity optimization in the evaluation of signals with ADCs (Analog-to-Digital Converters) or with micromechanical sensors.

[0028] By using two ADC units 130 and 140 respectively with different processing frequencies f A1 or f A2 Such pseudo-signals 220 and 225 can be identified. Only real acceleration signals, such as those leading to signal components 200, produce the same values ​​for both ADCs 130 and 140. By comparing the two ADC outputs, or signals 135 and 145, real acceleration signals 115 and pseudo-signals 220 and 225 can be clearly identified and processed.

[0029] Alternatively, a disturbance could be deliberately introduced during regular operation using a test signal 230 (for example, with a frequency of 0.75 kHz), thus verifying the correct functionality of both ADC units 130 and 140. This test signal 230 would then be identified as a deliberately generated test pseudo-signal 230 and subsequently checked for accuracy. If a signal component at a frequency of 0.75 kHz is present in both the first sample signal 135 and the second sample signal 145, it can be ensured that the sample units 130 and 140 are functioning correctly.

[0030] Regular disturbances on the supply line 250 can also be used as test signal 230 (see Fig. 1) They can be used, for example, when a DC / DC or AC / DC converter operates at a suitable frequency, the electrical filters 260 of the supply voltage 250 can be lower so that a certain proportion of known disturbances is on the supply line 250 and can then be used as a test signal.

[0031] This special method even allows the correct function of the power supply filter 260 to be checked simultaneously. This is because incorrect component placement or damage (keyword FMEA) on assembled circuit boards leads to different filter characteristics and then generates a different test signal 230 or test result in the sampling signals 135 or 145.

[0032] Another version is the (in the Fig. 1 (not shown) use of a second sensor element, which then runs completely on different drive / processing frequencies together with the second ADC unit.

[0033] It is clear that those relating to Fig. The described design is the most cost-effective because, due to the high integration of today's ASIC / silicon processes, an additional ADC unit does not incur any significant additional costs. (Compared to other optimization options for reducing EMC interference in ADCs)

[0034] Fig.Figure 3 shows a flowchart of a method 300 for determining a useful signal according to an embodiment of the present invention. The method 300 comprises a step 310 of sampling a read sensor signal at a first sampling frequency to obtain a first sampling signal and sampling the sensor signal at a second sampling frequency to obtain a second sampling signal, wherein the first and second sampling frequencies differ. Furthermore, the method 300 comprises a step 320 of recognizing the useful signal as signal components of the first and second sampling signals, wherein the signal components of the first and second sampling signals have the same frequency within a tolerance range.

[0035] If an embodiment includes an “and / or” connection between a first feature and a second feature, this is to be read as meaning that the embodiment according to one embodiment has both the first feature and the second feature, and according to another embodiment either only the first feature or only the second feature.

Claims

[1] Method (300) for determining a useful signal (155), wherein the method (300) comprises the following steps: - Sampling (310) of a read sensor signal (115) with a first sampling frequency (f A1 ), to obtain a first sampling signal (135) and sampling (310) of the sensor signal (115) with a second sampling frequency (f A2 ), to obtain a second sampling signal (145), wherein the first (f A1 ) and second sampling frequency (f A2 ) distinguish; and - Detect (320) the useful signal (155) as signal components (200) of the first (135) and second sampled signal (135), wherein the signal components (200) of the first (135) and second sampled signal (145) have the same frequency (228) within a tolerance range (227). [2] Method (300) according to claim 1, characterized by , that in the sampling step (310) a first (f A1 ) and second sampling frequency (f A2) is used, which is greater than twice a maximum detection frequency in step (320) of detection. [3] Method (300) according to any one of the preceding claims, characterized by , that in the recognition step (320) the useful signal (155) is recognized when the signal components (200) of the first (135) and second sample signal (145) have the same amplitude within a tolerance range. [4] Method (300) according to one of the preceding claims, characterized by a step of determining a disturbance signal (120) and / or a parameter of a disturbance signal (120), wherein the disturbance signal (120) and / or the parameter of a disturbance signal (120) is determined using the first (f A1 ) and second sampling frequency (f A2), the frequency of the signal components (200) recognized as the useful signal (155) and a first noise component (220) contained in the first sampled signal (135) and a second noise component (225) contained in the second sampled signal (145) is determined. [5] Method (300) according to one of the preceding claims, characterized by a step of applying a test signal (230) to the sensor signal (115), wherein the test signal (230) has a test signal frequency (f Test ) exhibits a frequency that differs from that of the sensor signal (115), in particular wherein, in the detection step (320), the useful signal (155) is detected when, in the first (135) and second sampling signal (145), a test signal component is present at a frequency (f) associated with the test signal (230). Test ) is recognized. [6] Method (300) according to any one of the preceding claims, characterized by, that in the step of applying the signal a supply voltage and / or a supply current of a device (105) performing the method (300) is filtered, wherein in the step of filtering a frequency component of the supply voltage and / or the supply current which deviates from the frequency of the useful signal (155) is applied to the sensor signal (115) as an interference signal. [7] Method (300) according to claim 6, characterized by , that in the verification step, a flawless execution of the filtering step is further detected if a frequency component of the supply voltage and / or the supply current at a predefined filter frequency is detectable in the first (135) and / or second sampling signal (145). [8] Method (300) according to any one of the preceding claims, characterized by , that in the sampling step (310) signals from two separate circuit assemblies are used as the first sampling signal (135) and second sampling signal (145). [9] Device (105) configured to carry out the method (300) according to any one of the preceding claims. [10] Computer program configured to perform the method (300) according to any one of the preceding claims. [11] Machine-readable storage medium on which the computer program according to claim 10 is stored.

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