FR2989493A1 - Inductive proximity detector i.e. contactless sensor, has signal processing unit processing signal, where processing unit determines presence or absence of metal target and tag in vicinity of detector and communicates with tag - Google Patents

Abstract

The detector has an oscillating circuit (1) that is sensitive to a metal target (4) or to a radio frequency identification (RFID) tag (5) whose frequency of resonance is close to resonance of frequency of the metal target. The oscillating circuit is excited by a frequency generator (2) that generates dynamic frequency for the oscillating circuit. A signal processing unit (3) processes signal taken on the oscillating circuit. The processing unit determines the presence or absence of the metal target and the tag in the vicinity of the detector and communicates with the tag.

Description

The present invention relates to an inductive proximity sensor also capable of downloading from an RFID tag (radio-tag) its configuration and its application, thus giving it the functionality of a programmable micro-machine. Inductive proximity sensors are non-contact sensors that detect the presence of a target, such as a metal object, when it is placed in the detection zone of the detector. They generally incorporate a temperature correction based on a temperature sensor to compensate for behavioral drifts of the circuits according to the ambient temperature, in order to obtain the best range and accuracy possible for the detector. They provide either a binary output signal indicating for example the presence or absence of a target, or an analog output signal, depending on the distance of the target from the detector. The proximity sensors may, depending on the needs of the application, be configured in multiple ways, depending on the polarity required for the output, depending on the normally open or normally closed state of the output, depending on the required detection range, delay on the output, the all or nothing or analog mode, the detection on distance threshold or frequency, etc ... All these options generate a large number of combinations, and as many possible references of products, and that of as much as these detectors are also available according to their format and their size: cylindrical or parallelepiped, of size 8, 12, 18, 30, 40, or 80 mm for example, and also according to their continuous or alternating power supply mode. This is the reason why the range of proximity sensors currently proposed by the manufacturers limit the combinations and therefore the product references, or integrate rudimentary human-machine interfaces to parameterize the detectors, using buttons push-buttons and light-emitting diodes for example. In the latter case, the extra cost incurred for these detectors 40 generally at a low price is far from negligible, and the manipulation for the parameterization of the detector under tension quite delicate. RFID (radio-identification) stations are devices that make it possible to communicate with an RFID tag, or RFID tag, when it is placed in their communication zone. They can feed the nearby tag with a magnetic field, read or write its memory by modulation of this magnetic field.

There are several standards of RFID communication carrier frequency: 125KHz, 13.56MHz, UHF. The tags of the 125KHz RFID range have certain peculiarities compared to tags operating at other frequency standards: they can initiate communication thanks to their TTF (Tag Talk First) mode, and therefore do not require amplitude modulation of the oscillator by the detector to be detected. Moreover their low frequency makes it possible to process the signal by sampling at each oscillation, and thus to enrich and secure the treatment by a better reactivity and a better filtering of parasitized samples. Finally, 125KHz RFID technology offers greater immunity to noise and metal interference than faster-frequency technologies. The main advantage of the 13.56MHz technology is the low cost of its tags.

RFID stations generally provide a communication service on a serial line to inform for example a remote controller. RFID stations are not autonomous and require an external device to be used. Programmable Logic Controllers (APIs) are programmable electronic devices for the control of industrial processes by sequential processing. They send orders to the outputs by running a client computer application. They require for this input data provided by external sensors such as for example proximity sensors or RFID readers. In addition, the programming of their application requires a serial link and an external device. The present invention relates to an inductive proximity detector which is also capable of communicating at no material cost or specific circuit with RFID tags (5), and to download from these tags a configuration parameter (15) and / or an executable application (16), to also give it a PLC functionality, the latter also having the temperature measurement (11) and the real-time resources ( 18) integrated in the processing unit (3).

The invention thus makes it possible to produce 3 products in one by pooling all the hardware and software resources integrated in the detector. The first object of the invention is to provide a parameterization method of the economic proximity detector, simple and fast, and automatic if necessary. It suffices to present an RFID tag (5) in front of the detector to enable the detector to download the parameterization instructions contained in this tag, provided that this tag has in its memory a parameter field containing these parameterization instructions, and that the detector is allowed to load them. This method may be suitable for large series, the same tag can be used for an unlimited number of detectors; The method can be automated by passing near the parameterization tag energized detectors carried by their production line.

Another possibility offered by the method is the scalability of the parameterization: In a production line equipped with such detectors, a tag integrated at the beginning of the chain of a new series can modify the parameterization of the detectors so as to adapt them to this new series.

Thus a same detector reference can be configured in multiple ways. The memorization of the setting of a detector in a tag also facilitates replacement, because it is sufficient to put this tag near the replacement detector to obtain the copy 40 of the detector to be replaced.

Another object of the invention is to allow the downloading of an application, or the outputs of the detector can be used, depending on the client application (16) downloaded by the tag vis-à-vis (5), to be operated according to programmed timings using the real-time clock (18), to count metal objects, access control, to detect a threshold of frequency of passage of objects, to actuate an output in analog mode by pulse cycle modulation (PWM), to transmit a Weigand frame, to make temperature control by means of the integrated temperature sensor (11), etc. Figure 1 shows the detector, its subassemblies, as well as a metal target (4) and a RFID tag (5) detectable nearby. According to the invention, the processing means (3) determine when a demodulated signal has the characteristics of an RFID tag transmission and if so, deserialize and memorize the received frame. According to the invention, the processing means (3) read the memory of a tag (5) in the vicinity and distinguish therefrom a certain number of fields separated by identifiers, each of these fields possibly containing either configuration parameters, or a client application, or application data. According to the invention all or some of the fields present in the tag (5) can be saved in the non-volatile memory 30 (9) of the detector, and replace the parameters (15), applications (16) and data (17) previously saved, provided that the detector is not protected for all or part of these replacements.

According to the invention the parameterization (15) thus stored in the non-volatile memory (9) fixes the operating mode of the detector, for example the normally open or normally closed state of each of the outputs (14), the required detection range for the target (4), the delays or monostables on rising or falling on each of the outputs (14), the all or nothing mode or PWM type modulation, the detection on threshold of range or frequency, the mode detection of ferrosity of the target, the locking of the detector in order to freeze the parameterization and / or the application, or any other characteristic According to the invention the tag vis-à-vis, some of the fields stored in the memory nonvolatile may contain client application code (16) to be executed by the detector. According to the invention, the oscillator LC (1), sensitive to a metal target (4) or to an RFID tag (5) of resonance frequency close to its own, is excited by a frequency generator 20 (2) granted dynamically to LC (1), and the signal taken from this oscillator is transmitted both to a demodulator (6) to detect a signal from a tag (5), and to a threshold detector (7) to detect a weakening due to a metal target (4). The detector is thus able to detect a metal target (4) as well as a tag (5), thanks to the processing of the CPU (8). According to the invention, the frequency generator (2) can be periodically deactivated by the CPU (8) in order to modulate the transmission thereof to transmit a command to the tag nearby (5), and also in order to allow a frequency measurement (13) of the freely oscillating oscillator (1). This measurement (13) allows the CPU (8) to dynamically tune the oscillator (1) by adjusting the frequency of the generator (2), in order to improve the detection range and the quality of the transmission to the oscillator (1). the tag (5). This measurement (13) also gives the CPU (8) complementary information on the ferrous nature and the distance of the target (4).

According to a particular embodiment of the invention, the processing unit can be fully integrated in a microcontroller or a DSP (digital signal processor), using its I / O ports (input / output) (14) for the management 5 outputs, its CPU as CPU (8), its EEPROM or flash memory as nonvolatile memory (9), a PWM as a frequency generator (2) 125 KHz RFID standard, an analog digital converter including the synchronized sampling by the PWM allows the CPU to know the level of the oscillations of the LC circuit (1) to perform both the threshold detection (7) to detect a target (4) and the demodulator (6) for detecting a tag (5) in TTF mode (Tag Talk First), an analog comparator for detecting a particular phase of the oscillator, and thus measuring its period with a timer from the CPU, and finally allowing the control of the period of the PWM on that of the oscillator. Industrial applications are numerous, covering all areas of application, from proximity sensors to RFID readers and micro-PLCs.

Claims (9)

REVENDICATIONS1. Inductive proximity detector also capable of communicating with an RFID tag and provided with programmable logic controller functionality, characterized in that it consists of an oscillating circuit LC (1) responsive to a metal target (4) or a RFID tag (5) of resonance frequency close to its own, and excited by a frequency generator (2) dynamically tuned to the oscillating circuit LC (1), characterized in that the detector comprises means for processing the signal taken from the oscillating circuit (1), these processing means (3) making it possible to determine, in the vicinity of the detector, the presence or absence of a metal target (4), but also of an RFID tag (5), and of communicate with this tag (5). 15 2. Detector according to claim 1, characterized in that the processing means (3) are composed of a frequency generator (2), a demodulator (6), a threshold detector (7), d a frequency measurement (13) of the oscillating circuit (1), a central processing unit CPU (8) with its random access memory, a non-volatile memory (9), and outputs (14). 3. Detector according to one of claims 1 to 2, characterized in that the processing means (3) can detect a tag (5) nearby by determining whether the demodulated signal (6) has the characteristics of a transmission RFID tag (5). 4. Detector according to one of claims 1 to 3, characterized by its ability to read the memory of a tag (5) detected nearby and to distinguish one or more fields separated by identifiers, each field may contain configuration settings, an executable client application, or application data 5. Detector according to one of claims 2 to 4, characterized in that any field of configuration parameters, executable client application, or application data (5), present in the tag, can be saved in the non-volatile memory (9). ), replacing the configuration parameters 40 (15) and / or the executable client application (16) and / or the previously saved application data (17), provided that the detector is not protected against all or part of these replacements . 6. Detector according to claim 5, characterized in that the parameterization (15) thus stored in the non-volatile memory (9) sets the operating mode of the detector, for example the normally open or normally closed state of each of the outputs ( 14), the detection range required for the target (4), the delays or monostables on rising or falling on each of the outputs (14), the all or nothing mode or by PWM modulation of each of the outputs, the range or frequency threshold detection, the target ferrosity detection mode, the locking of the detector in order to freeze the parameterization and / or the application. 7. Detector according to one of claims 5 to 6, characterized in that the application or applications (16) stored by the detector contain an application code executable by this detector, allowing it to react to all or part of the events related to a nearby target (4), depending on its distance as well as its frequency of passage, also to react to a nearby tag (5) and its contents, to the temperature provided by its detector (11), to the real-time constraints provided by its clock (18), in order to actuate the output (s) (14) of the detector, and / or to modify the contents of a nearby tag (4). 8. Detector according to one of claims 1 to 7, characterized in that the frequency generator (2) can be periodically deactivated by the CPU (8) in order to modulate the transmission thereof to transmit a command to the tag (5). ) in the vicinity and also in order to allow a frequency measurement (13) of the freely oscillating oscillator (1). 35 9. Detector according to one of claims 1 to 8 characterized in that the processing means can be fully integrated into a microcontroller or a DSP, using its I / O ports (14) for output management, its central unit as CPU (8), its EEPROM or flash memory as nonvolatile memory 40 (9), a PWM as a frequency generator (2) to 125 KHz RFID standard, an analog digital converter whose sampling synchronized by the PWM allows the CPU to know the level of oscillations of the LC circuit (1) to perform both the threshold detection (7) to detect a target (4) and the demodulator (6) to detect a tag (5) in mode TTF (Tag Talk First), an analog comparator to detect a particular phase of the oscillator, and thus measure its period using a timer of the CPU, and finally allow the servocontrolling of the PWM period on 10 that of the oscillator.