Method for detecting manipulation of a sensor unit

Abstract

Method for detecting manipulation of a sensor unit (100) comprising a measuring unit (110) configured to measure a physical property and a control unit (120) connected to the measuring unit (110) and configured to receive measurement signals from the measuring unit (110) and to send control signals to the measuring unit (110), the method comprising: - sending at least one predetermined diagnostic signal to the measuring unit (110) by means of the control unit (120), - receiving a response signal generated by the measuring unit (110) in response to the predetermined diagnostic signal at the control unit (120), and - detecting manipulation of the sensor unit (100) if the received response signal deviates from a predetermined reference signal by more than a threshold value.

Description

[0001] The present invention relates to a method for detecting manipulation of a sensor unit, preferably a sensor unit for an internal combustion engine of a vehicle.

[0002] Sensor units typically consist of a measuring unit configured to measure a physical property and generate an electrical measurement signal indicative of the physical property, such as a current signal, voltage signal, or resistance signal. A control unit connected to the measuring unit is configured to receive and process the measurement signals generated by the measuring unit and to send control signals to the measuring unit. The sensor unit, in turn, can be connected to a control device that further processes the sensor signals conditioned by the sensor unit.

[0003] However, sensor manipulation is becoming increasingly common, for example, by replacing the original measuring unit with another that may not offer the same measurement accuracy as the original. Replacing the original measuring unit with an electrical component is also becoming increasingly common, which, however, only delivers satisfactory measurement signals but does not indicate the physical property being measured. Such manipulations must be detected, as they also manipulate and falsify the measurement signal.

[0004] EP 3 581 894 A1 discloses a method, a device, and a system for detecting a tampering attempt on a sensor of a vehicle. A first measurement signal is read in, which is representative of a measured value of the first measurand detected by the sensor. Furthermore, it is determined whether the first measurement signal lies outside a predefined usable range. If it is determined that the first measurement signal lies outside a predefined usable range, an output signal is output, which is representative of a tampering attempt.

[0005] JP 2011-024354 A describes a control method for a motor generator. Specifically, the method is intended to detect whether a speed sensor is connected to the ECU. A disconnection is detected when a detection signal from the speed sensor can no longer be received. Furthermore, it discloses that a disconnection is detected when the ECU receives a pulse signal from the speed sensor that is not a continuous signal at predetermined intervals.

[0006] US 2014 / 0028463 A1 discloses a system and method for detecting a sensor replacement. The absence or disconnection of a current sensor can be determined by a controller based on the raw data of the applied input voltage, which may be random or irregular due to the fault.

[0007] CN 111 044 684 A describes a system for detecting the aging of a NOx sensor. The NOx sensor signal is compared with a reference signal during predetermined operating conditions, and any deviations indicate aging.

[0008] DE 10 2011 002 502 A1 relates to a method for diagnosing an exhaust gas sensor which is arranged in the exhaust gas region of an internal combustion engine for detecting at least one exhaust gas component, which is heated by means of a sensor heater and whose sensor temperature is detected.

[0009] DE 10 2004 031 625 A1 discloses a circuit arrangement for diagnosing a heating resistor which is connected in series with a first switch which connects the heating resistor to a power source for operating the heating resistor with a heating current.

[0010] From DE 101 31 229 A1, a sensor detecting a physical quantity, such as a pressure sensor, is known and further relates to both a device for detecting a physical quantity and a sensor signal processing device.

[0011] It is an object of the present invention to reliably detect a manipulation, such as a replacement of the original measuring unit, of a sensor unit and to issue a corresponding warning.

[0012] This object is achieved by a method according to independent claim 1. Advantageous embodiments are specified in the subclaims.

[0013] The present invention is essentially based on the idea of ​​checking for manipulation of a sensor unit, in particular a measuring unit of the sensor unit, by having a control unit of the sensor unit store a physical fingerprint of the measuring unit and query this fingerprint regularly or as needed, for example upon each restart of the sensor unit. For example, the control unit can query a diagnostic signal from the measuring unit for this purpose, for example in the form of sending a predetermined diagnostic signal and receiving an expected response signal from the measuring unit. If the response signal generated in response to the diagnostic signal does not correspond to expectations, it can be assumed that the measuring unit has been tampered with, for example, an unauthorized replacement of the measuring unit.

[0014] Consequently, according to one aspect of the present invention, a method is disclosed for detecting tampering with a sensor unit comprising a measuring unit configured to measure a physical property and a control unit connected to the measuring unit and configured to receive measurement signals from the measuring unit and to transmit control signals to the measuring unit. The method according to the invention comprises transmitting at least one predetermined diagnostic signal to the measuring unit by means of the control unit, receiving at the control unit a response signal generated by the measuring unit in response to the predetermined diagnostic signal, and detecting tampering with the sensor unit if the response signal received by the control unit deviates from a predetermined reference signal by more than a predetermined threshold value.

[0015] When comparing the received response signal with the predetermined reference signal, two signal curves are considered over time, wherein a deviation by more than the predetermined threshold value exists if at least one temporally discrete value or a variable of the response signal derived from the temporal curve deviates from the predetermined threshold value expected from the temporal curve of the reference signal.

[0016] The present invention takes advantage of the fact that tampering with the sensor unit, in particular the measuring unit, can be detected if the received response signal, which is generated in response to the transmission of the predetermined diagnostic signal, does not correspond to a predetermined expected reference signal or deviates from it by more than the threshold value. If this is the case, tampering with the sensor unit can be reliably detected.

[0017] Preferably, this procedure is performed each time the sensor unit is put into operation. This allows a check to be carried out before the actual measurement to determine whether or not the sensor unit has been tampered with in the meantime, i.e., since the last time it was put into operation.

[0018] In a particularly preferred embodiment of the method according to the invention, the predetermined diagnostic signal is one or more Dirac-type current pulses or an impedance measurement of electrodes of the measuring unit. Consequently, it is preferred that the predetermined diagnostic signal be a temporally shortest possible excitation with a defined bandwidth and amplitude, which forces the system to generate a response signal with a frequency and amplitude. This response signal is then compared by the control unit with a predetermined reference signal. A particular advantage of the Dirac-type diagnostic signal is the high information content of the response signal due to the broadband excitation.

[0019] In an advantageous embodiment of the method according to the invention, the sensor unit is designed to be used in an aircraft, a loading vehicle, a rail vehicle, a watercraft or a building.

[0020] In a particularly advantageous embodiment of the method according to the invention, the sensor unit is selected for use in an electric vehicle, a hybrid vehicle, or a vehicle with an internal combustion engine. In particular, it is an exhaust gas sensor for detecting the nitrogen oxide and / or ammonia concentration in the exhaust tract of the vehicle's internal combustion engine, wherein the measuring unit comprises a ceramic-based sensor element, such as yttrium-stabilized zirconium oxide.

[0021] In such a preferred embodiment, the yttrium-stabilized zirconium oxide, together with the electronics attached thereto, forms the measuring unit of the sensor unit within the meaning of the present invention. The sensor control unit (SCU), which is electrically connected to the measuring unit, forms the control unit of the sensor unit within the meaning of the present invention.

[0022] Preferably, the method according to the invention further comprises issuing a warning indicating manipulation of the sensor unit when manipulation of the sensor unit has been detected.

[0023] Further objects and features of the present invention will become apparent to those skilled in the art by practicing the present teachings and viewing the accompanying drawings in which: Fig. 1 schematic view of a sensor unit, and Fig. 2 an exemplary flow diagram of a method according to the invention for detecting a manipulation of the sensor unit of the Fig. 1.

[0024] The Fig. 1 shows a schematic view of a sensor unit 100. The sensor unit 100 of the Fig. 1 consists of a measuring unit 110, which is connected to a control unit 120 via an electrical connecting line 112. The control unit 110 can send control signals to the measuring unit 110 via the electrical connecting line 112, and the measuring unit 110, in turn, can transmit measurement signals to the control unit 110 via the electrical connecting line 112 for further processing.

[0025] The Fig. 2 shows an exemplary flow diagram of a method according to the invention for detecting a manipulation of the sensor unit 100 of the Fig. 1. In particular, the method according to the invention can be used to replace the measuring unit 110 of the sensor unit 100 of the Fig. 1 can be determined using a different unit of measurement.

[0026] The procedure of Fig.2 starts at step 200 and then proceeds to step 210, in which the control unit 120 sends at least one predetermined diagnostic signal to the measuring unit 110 via the connecting line 112. In a subsequent step 220, the measuring unit 110 generates a response signal in response to the predetermined diagnostic signal and transmits it to the control unit 120, which receives this response signal.

[0027] In a subsequent step 230, a check is performed to determine whether the received response signal deviates from a predetermined reference signal by more than a threshold value. If it is determined in step 230 that the received response signal deviates from the predetermined reference signal by more than the threshold value, the method proceeds to step 240, where tampering with the sensor unit 100 is detected before the method ends in step 260.

[0028] However, if it is determined in step 230 that the received response signal does not deviate from the predetermined reference signal by more than the threshold value, the method proceeds to step 250, at which a proper sensor unit 100 is diagnosed before the method again ends in step 260.

[0029] The predetermined diagnostic signal sent by control unit 120 can preferably be one or more Dirac-like current pulses, which, if the measuring unit 110 is functioning properly, lead to a known and expected response signal, which should correspond to a predetermined reference signal. Thus, by comparing the received response signal with the expected response or reference signal, tampering can be detected. The threshold value can be a measured value or a signal waveform.

Claims

[1] Method for detecting a manipulation of a sensor unit (100) comprising a measuring unit (110) configured to measure a physical property and a control unit (120) connected to the measuring unit (110) and configured to receive measurement signals from the measuring unit (110) and to send control signals to the measuring unit (110), the method comprising: - sending at least one predetermined diagnostic signal to the measuring unit (110) by means of the control unit (120), - receiving a response signal generated by the measuring unit (110) in response to the predetermined diagnostic signal at the control unit (120), and - detecting manipulation of the sensor unit (100) if the received response signal deviates from a predetermined reference signal by more than a threshold value. [2] Method according to claim 1, wherein the method is carried out each time the sensor unit (100) is put into operation. [3] Method according to one of the preceding claims, wherein the predetermined diagnostic signal is one or more Dirac-like current pulses or an impedance measurement of electrodes of the measuring unit (110). [4] Method according to one of the preceding claims, wherein the sensor unit (100) is designed to be used in an aircraft, a land vehicle, a rail vehicle, a watercraft or a building. [5] Method according to one of claims 1 to 3, wherein the sensor unit (100) is designed to be used in an electric vehicle, a hybrid vehicle or a vehicle with an internal combustion engine. [6] Method according to claim 5, wherein the sensor unit (100) is an exhaust gas sensor for detecting the nitrogen oxide and / or ammonia concentration in the exhaust tract of the internal combustion engine of the vehicle, wherein the measuring unit (110) comprises a ceramic-based sensor element. [7] Method according to one of the preceding claims, further comprising: - issuing a warning indicating tampering with the sensor unit (100) when tampering with the sensor unit (100) has been detected.

Images