Method and apparatus for evaluating a signal

Abstract

The invention relates to a method and a device for evaluating a signal (105), wherein the signal (105) is supplied from a signal source (110) via a signal conditioning unit (140) to a microcontroller (150) for signal evaluation, wherein the method has the following steps: - detecting a signal (105) from the signal source (110) and transmitting the signal (105) to a signal conditioning unit (140), which has an anti-aliasing filter (142); - filtering the signal (105) by means of an anti-aliasing filter (142) set in accordance with the signal (105) to be detected, and supplying the filtered signal (105) to a microcontroller (150); - processing and evaluating the filtered signal (105) in the microcontroller (150).

Description

Technical Field

[0001] This disclosure relates to a method and apparatus for evaluating a signal, wherein the signal is provided from a signal source to a microcontroller via a signal conditioning unit for signal evaluation. Signal evaluation may, for example, include measuring the amplitude, frequency, or load period of a noisy or disturbed PWM signal. Background Technology

[0002] In conventional signal evaluation using a microcontroller, the signal is first detected at the signal source and then transmitted to a signal conditioning unit via a transmission element such as a cable or line. The signal conditioning unit preprocesses the signal before it is sent to the microcontroller for signal evaluation. Interference can affect or introduce noise into the signal during signal detection, transmission, and preprocessing, also within the conditioning unit. In conventional devices for signal evaluation, the signal conditioning unit is correspondingly implemented in hardware such that the input signal level is adapted to the voltage range of the microcontroller. Relatedly, a bandpass filter, such as a low-pass filter, can be provided to remove high-frequency interference from the signal. Furthermore, the signal conditioning unit may have comparators or Schmitt triggers to obtain a sufficient signal-to-noise ratio relative to the switching threshold of a timer for measuring the frequency or load cycle. To adapt to signal characteristics, multiple comparators with different switching thresholds are sometimes implemented, or different switching thresholds are provided at the comparators used. This hardware solution or individual devices are space-intensive and prone to errors, which can interfere with or impair the signal evaluation. Traditional equipment, or methods used for signal evaluation, are sensitive to signal interference and edge smoothing (Flankenverschliff), and thus to amplitude and timing distortion when using low-order input filters. Furthermore, the different components result in high material costs and a larger required circuit board area. Additionally, higher software overhead can occur whenever limit values ​​or case-specific switching of comparators are required. Summary of the Invention

[0003] Therefore, the objective of this disclosure is to create a method and apparatus in which signal evaluation can be performed relatively simply while maintaining or improving the quality of the signal evaluation.

[0004] This task is accomplished by a method or apparatus having the features of the independent patent claims. Advantageous designs of this disclosure are described in the dependent claims.

[0005] According to this disclosure, a method for evaluating a signal has the steps listed below. For signal evaluation, a signal is provided from a signal source to a microcontroller via a signal conditioning unit. The signal source is the location or region where the signal is detected, for example, by means of a sensor. The signal conditioning unit is a unit configured to process or condition the signal before it is supplied to the microcontroller for signal evaluation. The microcontroller is configured to evaluate the signal.

[0006] - The signal from the signal source is detected and transmitted to a signal conditioning unit with an anti-aliasing filter. According to the method steps, the signal from the signal source is first detected and transmitted to the signal conditioning unit. The signal is then filtered using an anti-aliasing filter. The anti-aliasing filter is a filter constructed to reduce the bandwidth of the signal in order to satisfy the Nyquist-Shannon theorem regarding the relevant bandwidth. The anti-aliasing filter is a relatively simple form of bandpass filter (first-order RC low-pass), and therefore is not only the most cost-effective but also the most area-efficient implementation on a circuit board.

[0007] - The signal is filtered using an anti-aliasing filter, which is configured according to the signal to be detected. According to the method steps, the signal from the signal source is filtered using an anti-aliasing filter. Here, the anti-aliasing filter is configured such that the signal remains as unfiltered as possible within the relevant bandwidth, or the range can be advantageously and accurately evaluated for further signal evaluation.

[0008] - The filtered signal is processed in the microcontroller, wherein the filtered signal is processed by means of the following steps. The filtered signal provided to the microcontroller is further processed according to subsequent method steps for signal evaluation.

[0009] - The filtered signal is digitized using an analog-to-digital converter, thereby generating discrete values. According to this step, discrete values ​​are generated from the filtered signal using an AD converter, wherein the discrete values ​​are stored, for example, in a memory.

[0010] The generated discrete values ​​are compared with a predefined threshold or range, wherein the comparison is performed using a configurable digital comparator. According to the method steps, the generated discrete values ​​from the digitization are compared with a predefined range or a predefined threshold. The threshold or range may also be, for example, a limit band, a model, or a family of characteristic curves. According to one embodiment, the configurable digital comparator may be software-configurable.

[0011] - The comparison result is transmitted to the timer system. According to the method steps, the comparison result is transmitted to the timer system within the microcontroller.

[0012] If each discrete value is greater than a predefined threshold or a predefined range, or meets a comparison criterion, then each discrete value is stored in a predefined storage area, where the storage is initiated by a timer system. According to this method, if the corresponding discrete values ​​have already met the comparison criterion, the storage of each discrete value is initiated by a timer system based on a previously performed comparison. The comparison criterion is, for example, that each discrete value is greater than a predefined threshold or a predefined range. According to another embodiment, it is also conceivable that the comparison criterion includes not exceeding a predefined threshold or a predefined range, or that the comparison criterion is exceeding a predefined limit band.

[0013] - Evaluate the discrete values ​​of a signal stored in a predefined memory area. For example, the functional software of a microcontroller can perform evaluations from the predefined memory area to determine, for example, the amplitude, frequency, or other parameters of the signal.

[0014] According to this disclosure, external components such as threshold switching switches, comparators, and high-order filters are eliminated for signal evaluation. Furthermore, there is no need for a separate input at the microcontroller to the timer system for directly transmitting signals to the timer, nor is there any necessary control circuitry to the comparator or the switchable threshold. In addition to eliminating external components, this also reduces the board area. Accordingly, signal evaluation can be advantageously and robustly achieved with reduced board area and thus a simplified overall structure using the method according to this disclosure.

[0015] According to one embodiment, the anti-aliasing filter is configured such that the signal is attenuated as little as possible within the desired frequency range and has a sufficiently high stopband attenuation at the corresponding Nyquist frequency, depending on the signal to be detected. The desired frequency range is determined based on the signal to be detected, allowing for advantageous detection of the signal. According to one embodiment, the anti-aliasing filter is configured by a specific selection of the cutoff frequency. For example, if the desired frequency range (passband) is 50 kHz, the cutoff frequency of the anti-aliasing filter is set to 100 kHz, thereby keeping the effects in the passband low (attenuation, phase rotation). According to this embodiment, the stopband attenuation should be at least 40 dB to sufficiently suppress aliasing effects. Correspondingly, a Nyquist frequency of 10 MHz and a signal sampling rate of at least 20 MHz are obtained to satisfy Shannon's theorem. Overall, the detected signal can be advantageously and effectively detected and evaluated.

[0016] According to one embodiment, time-interval sampling of the filtered signal is performed by means of an analog-to-digital converter. Here, according to one embodiment, the sampling rate is configured to satisfy the prerequisites of digital signal processing for detecting the desired signal passband. According to one embodiment, the sampling rate is selected such that the Nyquist-Shannon sampling theorem is satisfied, thereby enabling the detection of the desired signal passband. As stated in the example shown above, a sampling rate of at least 20 MHz would be sufficient to satisfy the Nyquist-Shannon sampling theorem, correspondingly at a Nyquist frequency of 10 MHz.

[0017] According to one embodiment, a trigger time point or trigger window is defined by means of a timer system, during which the analog-to-digital converter digitizes the filtered signal and / or stores discrete values ​​in a predefined storage area. According to this embodiment, the timer system correspondingly pre-defines the trigger time point or trigger window during which the filtered signal is digitized by the analog-to-digital converter. The trigger time point or trigger window may correspondingly represent, for example, a relevant time point or window for signal evaluation during which signal evaluation or storage or digitization of the filtered signal should be performed. According to this embodiment, furthermore, if the timer system defines or pre-defines a corresponding trigger time point or trigger window, the discrete values ​​digitized by the analog-to-digital converter can only be stored in the predefined storage area. According to this embodiment, the storage space required for storing discrete values ​​can be reduced accordingly. Furthermore, according to this embodiment, the timer system can specifically pre-define during which time intervals or at which time points the corresponding signal evaluation can or should be performed.

[0018] According to one embodiment, the frequency and / or load period of a signal are determined by the timer system itself based on the results of comparisons transmitted to the timer system for signal evaluation. According to this embodiment, the timer system itself can determine the frequency and / or load period of the filtered signal solely from the results of the transmitted comparisons. The comparison results are, for example, 0 or 1, or a process of 0 and 1 over time (e.g., 0000, 1111, 0000). Based on this process, the timer system can read the edges and durations of each plateau, from which the frequency and load period of the signal can be determined.

[0019] According to one implementation, the frequency of the timer system is selected such that the required time resolution of the signal can be achieved. For example, if the signal to be detected has a frequency of 10 kHz and a resolution better than 1% should be achieved, then the frequency of the timer system must be 1 MHz.

[0020] According to one embodiment, the time resolution of the timer system is configurable and specified according to the expected frequency and / or expected load period of the signal to be measured. According to this embodiment, the time resolution of the timer system is set sufficiently high, for example, to map the expected frequency or load period of the signal to be detected to the required accuracy with the required tolerance. According to this embodiment, signal detection and signal evaluation can be advantageously performed with high precision accordingly. According to one embodiment, the resolution of the timer system is configurable according to the microcontroller.

[0021] According to one embodiment, the microcontroller has at least one configurable digital hardware filter by means of which frequency band limiting and / or decimation of discrete values ​​are performed before storing discrete values ​​in a predefined memory area. According to this embodiment, the software computation time for signal evaluation and the required memory area for storing discrete values ​​can be minimized or reduced.

[0022] According to one embodiment, bandwidth limiting and / or decimation of discrete values ​​are performed in a software unit using a computer-implemented digital filtering algorithm. According to another embodiment, bandwidth limiting and / or decimation of discrete values ​​can also be performed using a computer-implemented digital filtering algorithm before storing the discrete values ​​in a predefined storage area. According to this embodiment, noise filtering can be performed on the signal accordingly. Furthermore, computation time and required storage space can be minimized or reduced.

[0023] According to one embodiment, an evaluation of discrete values ​​stored in a predefined storage area is performed in a software unit using a computer-implemented method. Here, the discrete values ​​stored in the predefined storage area are provided to the software unit, and / or a frequency determined by a timer system and / or a determined load period are provided to the software unit. The software unit can then perform further evaluation of the signal based on the stored discrete values ​​and / or based on the frequency determined by the timer system and / or the determined load period. According to this embodiment, the signal evaluation is performed by the software unit based on the provided values, for example, to control the transmission system of a vehicle.

[0024] In one implementation, the predefined threshold or range is a programmable digital threshold or programmable digital range. The digital range may accordingly constitute a digital limit band, based on which the comparison result is determined. The programmable digital threshold or programmable digital range is programmed, for example, according to the signal to be detected and is stored in a microcontroller.

[0025] According to one embodiment, defined PWM communication is implemented on the plug interface between the charging post and the battery-powered vehicle using one of the aforementioned methods.

[0026] According to another aspect of this disclosure, an apparatus for signal evaluation is described. The apparatus includes a signal detection unit, a signal conditioning unit, and a microcontroller for signal detection. The signal is detected by means of the signal detection unit and provided to the microcontroller via the signal conditioning unit for signal evaluation, wherein the signal is preprocessed in the signal conditioning unit. The microcontroller includes an analog-to-digital converter, a software unit, and a timer system. The apparatus according to this aspect is constructed to implement one of the methods mentioned above. Attached Figure Description

[0027] Embodiments and improvements of the method according to this disclosure are shown in the figures and described in more detail below:

[0028] Figure 1 A schematic diagram of a signal processing device according to the prior art is shown.

[0029] Figure 2 A schematic diagram of a signal processing apparatus according to a first embodiment is shown. Detailed Implementation

[0030] Figure 1 A signal processing apparatus 100 as used in the prior art is shown. The signal processing apparatus 100 is configured to evaluate a pulse width modulated signal 105. Accordingly, the pulse width modulated signal 105 from a signal source 110 is first transmitted to a signal conditioning unit 140 via a signal transmission 120. Interference 130 may affect the signal 105 during signal detection from the signal source 110, during signal transmission 120, and through signal conditioning in the signal conditioning unit 140. Figure 1Interference 130 is schematically shown. For example, signal 105 is pre-filtered by means of signal conditioning unit 140. The filtered signal 105 is then fed from signal conditioning unit 140 to microcontroller 150. Microcontroller 150 has analog-to-digital converter 160, timer system 170, and software unit 180. According to this embodiment, the filtered signal from signal conditioning unit 140 is fed to analog-to-digital converter 160 and timer system 170 of microcontroller 150 via separate PIN inputs. Timer system 170 can trigger AD converter 160 to digitize the filtered signal. The digitized value from AD converter 160 and data from timer system 170 are fed to software unit 180 for signal evaluation. Software unit 180 then performs signal analysis 190 for signal evaluation. According to one embodiment, signal conditioning unit 140 has an upstream input filter for analog evaluation and a comparator for conditioning the signal so that it can be fed to timer system 170. Additionally, software unit 180 includes a limit value monitoring unit 200, which is configured to monitor limit values ​​or thresholds and, if necessary, control the limit values ​​or thresholds according to a function. The monitoring results can be sent to signal conditioning unit 140, or the switching of the comparator in signal conditioning unit 140 can be initiated.

[0031] Figure 2 A signal processing apparatus 100 according to one embodiment of the present disclosure is shown. According to this embodiment, the signal processing apparatus 100 is also configured to evaluate a signal 105. Accordingly, the signal 105 from the signal source 110 is detected. The detected signal 105 is transmitted to a signal conditioning unit 140 by means of a signal transmission 120. Interference 130 may occur at the signal source 110, during signal detection, signal transmission 120, and / or in the signal conditioning unit 140. Figure 2Interference 130 is schematically shown. According to this disclosure, signal conditioning unit 140 has an anti-aliasing filter 142 for filtering signal 105. Subsequently, the filtered signal 105 is provided to microcontroller 150, which is part of signal processing device 100, via a single input. Microcontroller 150 has an AD converter 160, a timer system 170, a software unit 180, a function 200 for threshold adaptation as needed, and a threshold probe 210. The function 200 for threshold adaptation as needed and the threshold probe 210 may be part of the software unit 180. The filtered signal 105 is fed to AD converter 160. AD converter 160 digitizes the filtered signal, thereby generating discrete values. The generated discrete values ​​are then compared with a predefined threshold or range, wherein the comparison is performed by means of threshold probe 210, which is part of software unit 180. According to one embodiment, threshold probe 210 is a configurable digital comparator. Its threshold is configured, or updated as necessary by means of a threshold adaptation function 200. It compares the digitized analog value obtained from the AD converter 160 with its threshold and transmits the digitized analog value (dieses) along with the result to the timer system 170. If each discrete value is greater than a predefined threshold or a predefined range, or meets a comparison criterion, then each discrete value is stored in a predefined storage area of ​​the signal processing device 100, where storage is initiated by the timer system 170. Subsequently, the discrete values ​​of the signal 105 stored in the predefined storage area of ​​the signal processing device 100 are evaluated by means of signal analysis 190 to assess the signal, for example, to determine the frequency and / or load period and / or amplitude of the signal 105.

[0032] According to this embodiment, the anti-aliasing filter 142 is configured based on the signal 105 to be detected, such that the signal 105 is attenuated as little as possible within the desired relevant frequency range, and has sufficiently high stopband attenuation at the corresponding Nyquist frequency. The analog-to-digital converter 160 performs time-interval sampling on the filtered signal, wherein the sampling rate is selected to achieve detection of the desired signal passband. According to one embodiment, the timer system 170 may define trigger times or trigger windows during which the analog-to-digital converter 160 digitizes the filtered signal 105 and / or stores discrete values ​​in a predefined memory area.

[0033] According to another embodiment, the timer system 170 can itself determine the frequency and / or load period of the signal based on the result of the transmitted comparison. The time resolution of the timer system 170 is defined according to the expected frequency and / or expected load period of the signal 105 to be measured. According to one embodiment, the microcontroller has at least one configurable digital hardware filter, by means of which the discrete values ​​are band-limited and / or decimated before being stored in a predefined memory area. Accordingly, the required memory area can be reduced and the required computational power can also be reduced. According to another embodiment, the software unit 180 has a computer-implemented digital filtering algorithm, thereby enabling the band-limiting and / or decimation of the discrete values. According to one embodiment, the predefined threshold or predefined range is a programmable digital threshold or programmable digital range that can be programmed according to parameters. Accordingly, the predefined threshold or predefined range can also be a family of characteristic curves or a model. The signal evaluated by means of the signal processing device 100 can be used, for example, to control the drivetrain of a vehicle.

Claims

1. A method for evaluating a pulse width modulation (PWM) signal, wherein the PWM signal is provided from a signal source to a microcontroller via a signal conditioning unit for signal evaluation, the method comprising the following steps: - Detect the PWM signal from the signal source and transmit the PWM signal to the signal conditioning unit, the signal conditioning unit having an anti-aliasing filter; - The PWM signal is filtered by means of an anti-aliasing filter set according to the PWM signal to be detected, and the filtered PWM signal is provided to the microcontroller; - The filtered PWM signal is processed in the microcontroller by means of the following steps: - The filtered PWM signal is digitized using an analog-to-digital converter, thereby producing discrete values; - The resulting discrete values ​​are compared with a predefined threshold or range, wherein the comparison is performed by means of a configurable digital comparator; - The result of the comparison is transmitted to the timer system; - The timer system determines the frequency and / or load period of the PWM signal based on the comparison results received from the configurable digital comparator; If each discrete value is greater than the predefined threshold or predefined range, or meets the comparison criteria, then each discrete value is stored in a predefined storage area, wherein the storage is initiated by the timer system based on the frequency and / or load cycle of the PWM signal, and - Evaluate the discrete values ​​of the PWM signal stored in the predefined storage area.

2. The method of claim 1, wherein the anti-aliasing filter is configured according to the PWM signal to be detected such that the PWM signal is attenuated as little as possible within the required frequency range and has a sufficiently high stopband attenuation at the corresponding Nyquist frequency.

3. The method according to claim 1 or 2, wherein time-isolated sampling of the filtered PWM signal is performed by means of the analog-to-digital converter.

4. The method according to claim 1 or 2, wherein a trigger time or trigger window is defined by means of the timer system, during which the analog-to-digital converter digitizes the filtered PWM signal and / or stores the discrete values ​​in the predefined storage area.

5. The method according to claim 1 or 2, wherein the frequency and / or load period of the PWM signal are determined by means of the timer system based on the result of a comparison transmitted to the timer system for signal evaluation.

6. The method of claim 1 or 2, wherein the time resolution of the timer system is configurable and is specified according to the expected frequency and / or expected load cycle of the PWM signal to be measured.

7. The method of claim 1 or 2, wherein the microcontroller has at least one configurable digital hardware filter, by means of which the frequency band limiting and / or decimation of the discrete values ​​are performed before the discrete values ​​are stored in the predefined storage area.

8. The method according to claim 1 or 2, wherein the frequency band limiting and / or decimation of the discrete values ​​is performed in a software unit by means of a computer-implemented digital filtering algorithm.

9. The method of claim 1 or 2, wherein the evaluation of discrete values ​​stored in the predefined storage area is performed in the software unit by means of a computer-implemented method, wherein the discrete values ​​stored in the predefined storage area are provided to the software unit, and / or wherein the frequency determined by means of the timer system and / or the determined load period are provided to the software unit.

10. The method according to claim 1 or 2, wherein the predefined threshold or the predefined range is a programmable digital threshold or a programmable digital range.

11. A signal processing apparatus for evaluating a pulse width modulation (PWM) signal, wherein the signal processing apparatus includes a signal detection unit, a signal conditioning unit, and a microcontroller, wherein the PWM signal is detected by means of the signal detection unit and provided to the microcontroller via the signal conditioning unit for signal evaluation, wherein the microcontroller includes an analog-to-digital converter, a digital comparator, a software unit, and a timer system, wherein the signal processing apparatus is configured to implement the method according to any one of claims 1 to 10.

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