Sensor self-diagnosis using multiple signal channels

0001Related application This application is a partial continuation application (CIP) of US Patent Application No. 12 / 889,749 (US application Ser. No. 12 / 889,749) filed on September 24, 2010, by reference to this application herein. , The entire disclosure content shall be incorporated into the present application.

0002Technical field The present invention generally relates to an integrated circuit (IC) sensor, and more specifically to an IC sensor self-diagnosis using a plurality of communication signal paths.

0003As part of the development in the field of automotive electronics, recent trends in driving technology have established established passive safety systems such as seat belts and airbags, anti-lock braking systems (ABS), electronic stability control (Electronic Stability Control). ) The aim is to expand the range of driving assistance functions by expanding with active safety systems such as programs (ESP) and electric steering systems. As has already been the case in drivetrains for some time now, systems are now becoming more complex in order to detect dangerous driving situations and allow control systems to actively intervene to help prevent accidents. It's coming. As technology continues to advance, this trend will continue and is expected to intensify in the future.

0004As a result, the significant increase in the number of electronic components with safety-related functions has created unprecedented demands in terms of reliability and system availability. While enabling such requirements to be met, it is desirable to develop efficient methods for functional self-monitoring with integrated testing methods along with redundancy to meet cost goals. ing. At the same time, it is also desired to develop design techniques for the purpose of detecting and avoiding possible weaknesses in safety systems at an early stage. In the field of magnetic field sensors, for example, this has been done with the introduction of the Safety Integrity Level (SIL) standard.

0005In order to meet SIL standards in the automotive field, implement and use appropriate self-tests, including built-in tests, as well as during normal operation as well as start-up, as well as automatic monitoring structures or corresponding redundant functional blocks and / Alternatively, it is required to provide a signal path. Conventional magnetic sensor systems, especially linear hall measurement systems, have used a single channel analog main signal path. Meeting SIL requirements in safety-critical applications with this concept is technically very difficult, or perhaps even feasible. Therefore, it is no longer possible to cover safety requirements with a single sensor system. Therefore, two identical redundant magnetic field sensors have been used in other conventional solutions to meet the requirements of SIL. Needless to say, the major drawback of these solutions is that they have two sensors instead of one, which doubles the cost accordingly. Yet another solution suggests superimposing a defined test signal outside the signal frequency range, for example by providing an additional on-chip conductor loop in the magnetic field sensor or superimposing it on the sensor. Such as a pressure sensor having an electrostatic coupling.

0006Reliable and cost-effective sensor systems that meet SIL and / or other applicable safety standards are still in need.

0007The invention can be further fully understood by taking into account the following detailed description of the various embodiments of the invention in conjunction with the accompanying drawings.

0008<figref num="1">Block diagram showing a system according to one embodiment</figref><figref num="2">Block diagram showing a system according to one embodiment</figref>

0009The present invention is applicable to various modifications and alternative embodiments, but for the purpose of giving specific examples, the drawings show specific embodiments among them, which will be described in detail below. However, as is self-evident, it is not intended to limit the invention to the particular embodiments described herein, and conversely, any modification contained within the ideas and scope of the invention as defined by the appended claims. , Equivalent and alternative forms are intended to be included.

0010Embodiments of the present invention relate to systems and methods for sensor self-diagnosis using multiple signal paths. According to one embodiment, the sensor is a magnetic field sensor and the system and / or method shall meet or be superior to relevant safety standards such as the SIL standard or other industrial standards. It is configured to be.

0011FIG. 1 shows a conceptual block diagram of the sensor system 100 according to one embodiment. System 100 includes a first sensor 102 and a second sensor 104, each of which communicates with a digital signal processor (DSP) 103. According to one embodiment, the first sensor 102, the second sensor 104 and the DSP 103 form a monolithic integrated circuit mounted on a single chip 105, where the DSP 103 is an external electronic control unit (ECU). ) Communicate with 106.

0012One of these sensors is the primary sensor or the main sensor. According to the embodiment of FIG. 1, the sensor 102 is the main sensor, whereas the sensor 104 is the secondary sensor. The main sensor 102 communicates with the DSP 103 via the main signal path, and the secondary sensor 104 communicates with the DSP 103 via a secondary signal path that is at least partially different from the main signal path. This will be described in detail below.

0013The secondary sensor 104 and the secondary signal path corresponding to this sensor are typically less accurate and slower and / or noisier than the main sensor 102, operate using different modes of operation, and / or add. Has a secondary sensing task. This allows the secondary sensor 104 to be less costly than the main sensor 102 and is main to the positioning and chip area, as well as other factors that affect the cost and complexity of the system 100. It can also be less constrained than the sensor 102. The secondary sensing tasks described above include the measurement of compensating signals such as temperature, mechanical stress, internal operating voltage or bias voltage, operating current or bias current, and / or a simpler auxiliary measurement of the subject. For example, sensors 102 and 104 include a magnetic field sensor according to one embodiment, in which case the magnetic field is the object of measurement for this type of sensor. However, in some embodiments, the secondary sensor 104 may include a plurality of sensors or sensor arrays, and as a specific example, according to one embodiment, a magnetic field sensor that mirrors the main sensor 102 and a temperature sensor. And a stress sensor may be included.

0014However, according to one embodiment, the secondary sensor and the secondary signal path can be used for validation comparison with the main sensor and the main signal path. Further, the secondary sensor and the secondary signal path can be used for failure detection and verification of the main sensor and the main signal path. Such a configuration can provide several advantages. First, SIL compatibility can be achieved. Second, it offers size and cost advantages when compared to conventional solutions, and can be self-tested during normal operation with little extra hardware. In addition, additional self-testing capabilities of digital signal processors (DSPs) and signal processing software can be implemented. In addition to these, field failure rates and return rates can also be reduced, which improves cost effectiveness for both, both the manufacturer of the underlying chip and the customer who mounts the chip.

0015With reference to FIG. 2 next, an embodiment of the sensor system 200 based on the concept shown in FIG. 1 is depicted as a block diagram. System 200 includes a main magnetic field sensor 202 and a secondary magnetic field sensor 204, such as the Hall effect or giant magnetoresistance (GMR). However, according to another embodiment, the sensors 202 and 204 may be different types of sensors, and these sensors are not limited to magnetic field sensors. The sensor 202 is conceptually similar to the sensor 102, while the sensor 204 is conceptually similar to the sensor 104, and these sensors have already been described with reference to FIG.

0016System 200 also includes one or more additional sensors 208, which are also considered to be secondary or auxiliary sensors. In various embodiments, the one or more sensors 208 may include the form of a temperature sensor, a stress sensor, a current sensor, a magnetic field sensor or some other sensor.

0017According to one embodiment, the main sensor 202 communicates with the digital signal processing (DSP) unit 220. The DSP unit 220 itself can communicate with an external ECU or other control unit (see, for example, FIG. 1) via the input / output unit 210. According to one embodiment, the sensors 202 and 204 communicate with the DSP unit 220 via separate signal paths, which separate signal paths can include structurally different analog and combined signal paths. , And for a particular range, digital signal paths and digital signal processors, and software components. In FIG. 2, the main signal path associated with the main sensor 202 is shown by a thick line, while the secondary signal path associated with the sensor 204 is shown by a simple dashed line.

0018For example, according to the embodiment of FIG. 2, the main signal path can transmit a signal from the main sensor 202 to the analog / digital (A / D) converter 212 and the cross switch 214 of the A / D conversion channel. The secondary signal path transmits signals from the secondary sensor 204 to the multiplexer 216, which receives all signals as input from the additional sensor or auxiliary sensor 208. The secondary signal path then continues from the MUX 216 to the second A / D converter 218, which also transmits its output to the crossswitch 214.

0019According to one embodiment, the elements of the main signal path and the elements of the secondary signal path are not identical and / or are implemented using different modes of operation. For example, the A / D converter 212 in the main signal path can have a third-order delta-sigma converter, while the A / D converter 218 in the secondary signal path can have a first-order delta-sigma converter. It can have type converters, or one or more analog-to-digital converters can use sequential comparison register (SAR) or flash type techniques instead of delta-sigma type. In other words, the secondary sensor 204 is typically less accurate and slower than the main sensor 102, and / or is noisy, operates using different modes of operation, and / or additional secondary sensing tasks. Similarly, the same applies to the A / D converter 218 when compared to the A / D converter 212. Further, when the secondary sensor 204 is compared with the main sensor 102, the sampling rate is low, the latency time is high, the bandwidth is low, the analog-to-digital conversion resolution is low, and the signal range can be narrowed. Further, the signal coding may be different, the sensor signal mapping may be different, the compensation algorithm may be different, and / or the processing schedule may be different. Moreover, the secondary sensor 204 can include a second sensing element, which is less than the main sensor 102, which includes the first sensing element. Further, the secondary sensor 204 may include a second sensing element having a second detection area that is narrower than the main sensor 102 that includes the first sensing element in the first detection area.

0020Different operating methods can be implemented by any of a plurality of methods. Different operating methods can be implemented as hardware implementations for functional parts with a first signal path, while the corresponding functional parts of the second signal path are realized in software. As another option, different modes of operation can be implemented for the first signal path using a different sensing technique than the second signal path. Yet another option is to use a different mode of operation with respect to the first functional part of the first signal path, at least partially with respect to the second functional part of the second signal path corresponding to this first functional part. It can be implemented by adopting different functional processing hardware.

0021The output of the cross switch 214 is associated with both the main signal path and the secondary signal path and is supplied to the digital signal processing (DSP) unit 220. According to one embodiment, the DSP 220 includes a state machine 222, a clamping algorithm 224, and a memory matrix 226. To match the concept of providing a main signal path and a secondary signal path, the DSP 220 also includes a first software section associated with the main signal path and a second software section associated with the secondary signal path. It has been. In addition to these, or optionally, the DSP 220 may implement different DSP techniques or DSP techniques for the main signal path and the second signal path. According to one embodiment, the DSP 220 is connected to the I / O 210 via interface 228, and the I / O 210 itself is connected to an external ECU (not shown in FIG. 2). ..

0022The DSP220 can be implemented as a multi-core processor or as two or more DSPs. In this case, the multi-core DSP may have the same core or may have different cores. Further, the DSP 220 may have a DSP of a certain manufacturer in the main path, and may have a multi-core DSP of a different manufacturer in the secondary signal path.

0023In this way, the main signal path and the secondary signal path can provide two different, so to speak, redundant analog signal paths, which provide a number of useful properties. For example, by transmitting the main magnetic field signal from the sensor 202 in one cycle via the main signal path, highly accurate calculation results can be obtained. Here, the main signal path itself operates faster, at least with much higher accuracy than the secondary signal path, using chopping or other techniques. In addition, the main signal path is free to operate independently without being affected by other system components.

0024The secondary signal path also provides an option to supply its own data to the control unit for analysis purposes, in which the data can be processed with either a positive or negative polar sign. While system 200 has been shown to allow parallel output from DSP 220 to interface 228 and I / O 210, it is also possible to implement sequential transmission, for example using time division multiplexing or on demand as an external request. it can.

0025The output from the DSP 220 to the interface 228 can be sent out via only one terminal. Depending on the multiplex scheme, this terminal will supply the first output signal associated with the main signal path in some cases, and in other cases the secondary according to the multiplex scheme. A second output signal associated with the signal path will be supplied.

0026The sensors 202 and 204, and optionally the sensor 208, can use different sensing methods for their measurements, and such various sensing methods include processing techniques, technical performance and specifications, sensors 202 and 204. Includes its own size and / or placement, as well as biassing. One embodiment of the system 200 includes two bandgap biasing units 230 and 232 and a biasing comparison unit 234. The biasing unit 230 is associated with the main signal path, and the biasing unit 232 is associated with the secondary signal path. The bicing units 230 and 232 provide different bicing options for the sensors 102 and 104, respectively, while the bicing comparison unit 234 allows the output signal to the DSP 220 to be considered.

0027Further, according to some embodiments of the system 200, different A / D conversion and / or switching concepts can also be used via the A / D converters 212 and 218 and the crossswitch 214. For example, as described above, the A / D converter 212 in the main signal path can have a third-order delta-sigma converter, while the A / D converter 218 in the secondary signal path has 1 It can have the following delta-sigma transducers, or one or more analog-to-digital converters can use sequential comparison register (SAR) or flash type technology instead of delta-sigma type. it can. In various embodiments, such different A / D conversion and / or switching concepts can result in different failure behaviors and / or failure probabilities. In some additional embodiments, the measurement range can also be switched via the inputs described to the A / D converters 212 and 218 of FIG. 2 for the purpose of detecting clamping or limiting effects.

0028Further, according to some embodiments, it is also possible to provide an option to switch between the sensors 202 and 204 and their individual main and secondary signal paths. For example, the secondary sensor 204 can be switched to the main signal path, and so on for the sensor 202 and the secondary signal path. This option can improve fault detection and / or fault locating, for example by making the sensor independent of its path.

0029Another advantage brought about by the embodiment of the system 200 is that the output signals of each of the main signal path and the secondary signal path can be compared and the result evaluated, such as by forming a quotient. This result can be evaluated to determine one or more situations related to the performance or functionality of sensors 202 and 204, each signal path, system 200, and / or some other component. For example, a comparison of output signals can detect rapid changes in input signals. In embodiments where compensation such as temperature compensation is used when the sensor 208 includes a temperature sensor, the output signals can be compared depending on the temperature compensation signal. According to yet another embodiment, clamping or limiting of information from sensor 208 can be performed to separate other signals, characteristics or information.

0030Since the DSP 220 uses software 1 for the main signal path and software 2 for the secondary signal path, the output results of these signal paths can be compared according to some embodiments. Such a comparison makes it possible to check the software algorithm itself. Internal or external window comparisons can be used to validate the two signal paths or comparison results of the DSP220. Warnings and / or failure thresholds can be implemented as part of this type of validation check.

0031To compare the output results of each of the two signal paths, see the quotient of each output result of the two signal paths, the linear transformation, and the comparison of the absolute difference between the output results of the two signal paths and the difference threshold. You can include at least one of them.

0032Therefore, according to some embodiments, safety standard compatibility as well as failure self-diagnosis in the sensor system can be provided. Depending on the type and rigor and the particular system of interest and / or the standards involved, failure handling may vary, but some embodiments show detected problems to the system user. You will be able to provide an opportunity to warn. For example, in safety-critical automotive electronic power steering sensor applications that use magnetic sensors, critical system issues can be communicated to the ECU to take appropriate action. Can be warned to the driver. In some applications, the ECU can be programmed to switch to safe mode or safe operating protocol in the event of an error, failure or deviation.

0033In addition, some embodiments are more efficient in terms of space and cost than conventional solutions with redundant primary sensors. For example, depending on some embodiments, using only one primary sensor instead of two, and making the secondary sensor a generally cost-effective device in terms of reduced performance requirements. For example, the main / secondary sensors and signal paths can limit the chip area to less than 10% increase. The advantage over the conventional solution with two primary sensors on a single chip is also achieved in that the cost of the secondary sensor is kept low.

0034So far, various embodiments relating to systems, devices and methods have been described. These embodiments are presented only for the purpose of showing specific examples, and are not intended to limit the scope of the present invention. Furthermore, it should be understood that the various features of the embodiments described so far can be combined in various ways to create a number of additional embodiments. In addition, various materials, dimensions, shapes, installation locations, etc. have been described for use with the disclosed embodiments, but other materials other than those disclosed here are also used without exceeding the scope of the present invention. be able to.

0035Further, as will be obvious to those skilled in the art, the features that can be included in the present invention may be less than those shown in any of the individual embodiments described above. Furthermore, the embodiments described here are not intended to present a method capable of combining various features of the present invention. Thus, those embodiments are not a combination of features that are mutually exclusive, but rather the invention is self-evident to those skilled in the art, of the individual various features selected from the various individual embodiments. It can include combinations.

0036Any incorporation by reference to the references mentioned above is restricted so that it does not incorporate a gist contrary to the explicit disclosure of the present application. In addition, any inclusion by reference to the above-mentioned documents is further restricted so that the claims contained in the document are not incorporated by reference. Moreover, any of the definitions presented in the literature, whatever the inclusion by reference to the above-mentioned literature, is further restricted so that it is not incorporated by reference unless otherwise stated in the present application.

0037It is specifically intended for the purposes of interpreting the claims of the present invention that the provisions of 35 USC, Article 112, paragraph 6 are the specific term "means for" or. That is, it does not apply unless a "step for" is stated in the claim.