Method for establishing a wireless communication link between a field device and a mobile terminal and system

Abstract

The invention relates to a method for establishing a wireless communication link between a field device (1a; 1b) of automation technology and a mobile device (2a; 2b), for switching the field device (1a; 1b) by the mobile device (2a; 2b) by means of the wireless communication link. The field device is controlled based on a current distance estimate (Xid). ti ) switched. Furthermore, the invention relates to a system (100) of automation technology, comprising such a field device (1a; 1b) and such a mobile terminal device (2a; 2b).

Description

[0001] The invention relates to a method for establishing a wireless communication connection between an automation field device and a mobile terminal. Furthermore, the invention relates to an automation system comprising such a field device and such a mobile terminal.

[0002] Field devices are widely used in process automation technology, as well as in manufacturing automation technology. Field devices essentially refer to all devices used close to the process and that provide, process, and / or display process-relevant information. Field devices are used, for example, to record and / or influence process variables. Measuring instruments or sensors are used to record process variables. These are used, for example, for pressure and temperature measurement, conductivity measurement, flow measurement, pH measurement, level measurement, etc. and record the corresponding process variables such as pressure, temperature, conductivity, pH value, level, flow rate, etc. Actuators are used to influence process variables. These are, for example, pumps or valves that can influence the flow of a liquid in a pipe or the level in a container.In addition to the previously mentioned measuring devices and actuators, field devices also include remote I / Os, wireless adapters, and generally devices located at the field level. A large number of such field devices are manufactured and distributed by the Endress+Hauser Group.

[0003] Many such field devices have physical switching and / or operating elements, which can be used to trigger a switching operation. These switching and / or operating elements are designed, for example, as touch displays and / or as knock sensors and / or switches. These switching and / or operating elements are used to trigger certain actions on the field device, such as switching a display on a display unit or setting parameter values, etc. Such physical switching and / or operating elements have a number of disadvantages, including: - the high costs of the hardware components used, the connection and / or assembly; - the effort required for the required sealing of a field device housing, which may have to be designed in accordance with relevant standards, for example in the hygiene sector. - In addition, due to the process-related use, physical switching and / or operating elements of a field device installed in a process plant may be difficult or even impossible to access. - Finally, physical switching and / or control elements have a limited lifespan and / or a certain probability of failure.

[0004] DE 10 2020 120 297 A1 discloses a method for extending the operating functionality of a field device in automation technology from one operating device to at least one further operating device.

[0005] The invention is based on the object of providing a possibility to switch a field device without the use of a physical switching and / or operating element of the field device.

[0006] The problem is solved by a method for establishing a wireless communication connection between a field device of automation technology and a mobile terminal, for switching the field device by the mobile terminal by means of the wireless communication connection.

[0007] Advantageous embodiments are specified in the dependent claims.

[0008] The method according to the invention comprises the steps: - Providing a field device for automation technology, wherein the field device comprises: -- a programmable computing / control unit -- a field device transmitting / receiving unit that can be controlled by the computing / control unit; - Providing a mobile terminal with a terminal transmitting / receiving unit, wherein the field device transmitting / receiving unit and the terminal transmitting / receiving unit are designed to communicate with each other by means of a wireless communication connection, in particular using a predetermined frequency range, in particular according to a standardized communication protocol; - Transmitting telegrams from the terminal device transmitting / receiving unit to the field device transmitting / receiving unit and / or from the field device transmitting / receiving unit to the terminal device transmitting / receiving unit via the wireless communication link; - Determining a current distance estimate based on the transmitted telegrams, which current distance estimate correlates with a current physical distance between the field device and the mobile device; and - Switching, especially automated switching, of the field device based on the current distance estimate.

[0009] The mobile device may be, for example, a smartphone, a tablet or a wearable, such as a smartwatch or data glasses, or a mobile device specifically designed for process automation, such as the FieldXpert marketed by the applicant.

[0010] Modern field devices often have a radio interface through which the field devices can communicate using such mobile devices. For this purpose, the field device and the mobile device are equipped with specially designed transmit / receive units. The transmit / receive units are designed, for example, to be tuned to a predetermined frequency range. Common communication frequencies are usually 2.4 GHz. For example, the transmit / receive units are preferably designed to transmit data or telegrams using a wireless protocol, such as Bluetooth LE and / or Wi-Fi.

[0011] The programmable computing / control unit can be assigned, in particular at least partially, to a transmitter unit, which serves to process and / or forward a measurement signal acquired by the field device. However, the programmable computing / control unit can also be assigned, in particular at least partially, to a module, in particular separate from the transmitter unit, which comprises the field device's transmitting / receiving unit, such as a Bluetooth module.

[0012] The distance estimate is used to determine the physical proximity of the field device to the mobile device. Preferably, based on the current distance estimate, the field device is automatically switched using the mobile device, so that the field device can be switched or operated using the mobile device even without the use and / or secure accessibility of physical switching and / or control elements. In particular, the field device can be free of physical switching and / or control elements.

[0013] In one embodiment of the procedure, this includes the following steps: - Comparison of the current distance estimate with a specified or specifiable limit value; - In case that at least the current distance estimate either exceeds or falls below the limit value: Switching the field device.

[0014] The limit value is selected, for example, such that if a physical distance between the field device and the mobile terminal estimated by means of the distance estimate is smaller than a maximum distance, e.g. is estimated to be less than 1.5 m, in particular less than 0.5 m, preferably less than 0.2 m, the field device can be switched by means of the mobile terminal, in particular is switched automatically.

[0015] In one embodiment of the method, at least one of the following steps is carried out during switching: - Switching the field device into an active communication mode in which there is an increased range of the field device transmitting / receiving unit compared to the range of the field device transmitting / receiving unit outside the active communication mode, wherein the range is increased in particular to at least twice, preferably at least 10 times, compared to the range of the field device transmitting / receiving unit outside the active communication mode; - Activating and / or changing a display, in particular an optical and / or acoustic display, that is displayed on a field device display unit.

[0016] Outside of active communication mode, the range of the wireless communication connection of the field device's transceiver unit is limited to a maximum of 1 m, especially 0.5 m, for security reasons, e.g., to prevent the field device from communicating with a more distant mobile device. The range limitation thus serves as a tamper protection.

[0017] In active communication mode, the range can be increased, for example, by increasing the transmission power. Outside of active communication mode, the range is limited to a reduced value below the technically feasible transmission power and the associated range. For example, a range of 100 meters or even more is technically possible for Bluetooth. Even in active communication mode, the range may not be increased to the technically maximum possible value—for example, to ensure continued compliance with a standard specified in the relevant norms.

[0018] The field device display unit includes, for example, an optical display unit, e.g. a physical or virtual display, such as an LCD display, an LED, etc. and / or an acoustic display unit such as a loudspeaker.

[0019] Activating and / or changing an optical display includes, for example: flashing, changing the color and / or brightness, switching through measurement and / or status values ​​determined by the field device on a display, etc.

[0020] Activating and / or changing an acoustic indication includes, for example, playing and / or changing a sound, e.g. a beep, etc.

[0021] In one embodiment of the procedure, the procedure comprises the following steps: - Sending a distance estimate telegram by the terminal device transmitting / receiving unit and receiving the distance estimate telegram from the field device transmitting / receiving unit; - Determination of a signal strength of the distance estimation telegram by the computing / control unit; - Determining the current distance estimate based on at least the determined signal strength of the distance estimate telegram by the computing / control unit.

[0022] In this embodiment, the computing / control unit assigned to the field device preferably determines the current distance estimate itself. In particular, the field device is not switched using a distance estimate determined by the mobile device. Therefore, the mobile device preferably does not perform a distance estimate and does not need to be configured to do so.

[0023] In one embodiment of the method, the distance estimation telegram comprises terminal identification information specific to the mobile terminal and / or the field device transmitting / receiving unit determines a reception time information specific to a time of reception of the distance estimation telegram by the field device transmitting / receiving unit, wherein at least one of the following information is transmitted together with the determined signal strength from the field device transmitting / receiving unit to the computing / control unit: - the terminal device identification information, - the reception time information.

[0024] The distance estimate is estimated by the field device specifically for the respective mobile device. This can be achieved, for example (see the following embodiments), by storing the distance estimate as a distance estimate specific to a respective mobile device, by always linking it to the device identification information in a memory of the field device.

[0025] In one embodiment of the method, a data set comprising at least one of the following: - the signal strength, the terminal identification information, the reception time information, and the current distance estimate are stored in a writable and readable memory of the computing / control unit.

[0026] In one embodiment of the procedure, this includes the step: - Recurring transmission of distance estimate telegrams by the terminal device transmitting / receiving unit and receiving the recurringly transmitted distance estimate telegrams from the field device transmitting / receiving unit.

[0027] In one embodiment of the method, this comprises the step: In the event that, for a time interval which is greater than a predetermined limit time interval, no distance estimation telegrams are received from the field device transmitting / receiving unit which comprise terminal device identification information that matches terminal device identification information of a data set stored in the memory: - Deleting the data record from the memory, whereby the specified limit time interval is less than five minutes, in particular less than one minute, and preferably less than half a minute.

[0028] A time interval is thus determined that has elapsed since the last reception of a distance estimate telegram sent by a respective mobile device. The time interval is determined, for example, based on the time information at the time of reception and with the aid of a time recording unit (e.g., a timer) that the field device, in particular the computing / control unit, has; see also the system mentioned below, which is also encompassed by the invention. The limit time interval ensures regular emptying of the memory in the event that no more distance estimate telegrams are received from the respective mobile device. This prevents the memory from filling up, or the memory can be designed accordingly small.

[0029] In one embodiment of the method, if a previous distance estimate is stored in the memory, which previous distance estimate was determined on the basis of a previous distance estimate telegram received at a previous time, the step of determining the current distance estimate comprises the following steps: - Determining a last signal strength, which last signal strength corresponds to the signal strength of a last received distance estimate telegram; - Determining a last time, which last time corresponds to the time of receipt of the last received distance estimate telegram; - Reading the previous distance estimate and the previous time from the memory; - Determining a time difference between the last time and the previous time; and - determining the current distance estimate as a smoothed estimate, wherein the current distance estimate depends on both the last signal strength and the previous distance estimate such that the contribution of the last signal strength and the previous distance estimate to the current distance estimate is taken into account by means of a smoothing coefficient, which smoothing coefficient depends on the time difference.

[0030] In a further development of the previous embodiment, the contribution of the last signal strength and the contribution of the previous distance estimate to the current distance estimate are taken into account by means of the smoothing coefficient such that the greater the time difference, the more the last signal strength and the less the previous distance estimate contributes to the current distance estimate.

[0031] For example, in the simplest case, a weighted average is used, where the current distance estimate Xid ti depending on the previous distance estimate Xid tj and the last signal strength SP_i is determined to: Xidti=α (Δt)*SP_i+[1−α (Δt)]*Xidtj, where in the above formula for the smoothing coefficient α (Δt) 0 < α (Δt) < 1, and the smoothing coefficient α (Δt) increases with increasing time difference, especially continuously. In this way, with increasing time difference, the previous distance estimate Xid tj weaker, and with increasing time difference, the last signal strength SP_i is weighted more heavily. This corresponds to a so-called exponential smoothing with a smoothing coefficient α (Δt) dependent on the time difference.

[0032] In a further development of the previous embodiment, the smoothing coefficient depends on the time difference in such a way that the time difference is included in the smoothing coefficient only in relation to the limit time interval, in particular as a quotient formed from the time difference divided by the limit time interval.

[0033] In one embodiment of the method, if no previous distance estimate is stored in the memory, the step of determining the current distance estimate comprises the following step: - Determining the current distance estimate as the last signal strength, which last signal strength corresponds to the signal strength of a last received distance estimate telegram.

[0034] In one embodiment of the method, the mobile terminal is designed to execute at least one operating program with a plurality of display elements and operating functionalities, wherein the field device can be operated by means of the operating program, and wherein at least the following steps are carried out during switching: - Displaying the field device in a display element of an operating program executed by the mobile device, in particular simultaneously with the activation and / or changing of the, in particular optical and / or acoustic, display on the field device display unit.

[0035] Such an operating program is published by the applicant in the form of an app under the name “SmartBlue”. The app shows the display elements on the mobile device. Such display elements are, for example, control surfaces, menu structures and / or buttons via which operating inputs can be made, or graphs which visualize data from the field devices, e.g. measured values ​​or status information. In the case of data glasses as the mobile device, for example, the display elements are displayed in the field of vision and the execution of operating functions, e.g. control via gestures, takes place in the field of vision. Using the method according to the invention, the respective field device that can be switched using the mobile device is displayed in the operating program on the basis of the current distance estimate, which is used to identify a current physical proximity of the field device to the mobile device. This is particularly important.It is advantageous if several field devices can be operated via the operating program, all of which are listed in the operating program. In this case, the field device that can be switched via the mobile device is specifically displayed in the operating program, e.g., with a color background.

[0036] In one embodiment of the method, the memory - a first data set, the first data set comprising a first current distance estimate and / or a first signal strength of the first mobile terminal, with first terminal identification information belonging to a first mobile terminal and - a second data set, the second data set comprising a second current distance estimate and / or a second signal strength of the second mobile terminal, stored with a second terminal identification information belonging to a second mobile terminal, wherein both the first current distance estimate and the second current distance estimate are related to the limit value such that the field device can be switched by both the first mobile terminal and the second mobile terminal by means of the wireless communication connection, and wherein the method comprises the following step to be performed before switching the field device: - Selection of one of the two mobile devices for switching, based on at least one of the following: - a comparison of the first current distance estimate with the second current distance estimate - a comparison of the first signal strength with the second signal strength.

[0037] The invention further comprises an automation system comprising: - a field device of automation technology, comprising: -- a programmable computing / control unit and -- a field device transmitting / receiving unit that can be controlled by the computing / control unit; and - a mobile terminal comprising a terminal transmitting / receiving unit;wherein the system is designed to carry out the method according to the invention.

[0038] The system includes, mutatis mutandis, all the above-mentioned embodiments of the procedure.

[0039] The invention is explained in more detail with reference to the following figures, which are not to scale. Like reference numerals denote like features. Where necessary for clarity or otherwise deemed appropriate, reference numerals have been omitted from the figures.

[0040] They show: Fig. 1: An embodiment of a system 100 according to the invention; Fig. 2: Steps of the method according to the invention in an embodiment of the method according to the invention; and Fig. 3: Steps of the method according to the invention in an embodiment of the method according to the invention.

[0041] Fig. 1 shows an automation system 100 in one embodiment of the invention. In the embodiment shown here, this comprises two field devices 1a; 1b, which are installed in the same automation process plant, as well as two mobile terminals 2a; 2b. For the sake of clarity, the invention is explained using the system 100 shown here. Without limiting generality, the system 100 can of course also comprise a plurality of field devices 1a, 1b,... and mobile terminals 2a, 2b,... Each of the mobile terminals 2a, 2b and field devices 1a, 1b is equipped with a transmitting / receiving unit, by means of which a communication connection KV can be established. Furthermore, without limiting generality, the invention is explained here and below in connection with transmitting / receiving units designed to transmit telegrams TG according to the wireless protocol of a Bluetooth standard, e.g., BLE.Of course, the invention also includes all other transmitting / receiving units or wireless protocols known from the prior art for wireless communication for establishing wireless communication connections KV.

[0042] For security reasons, the Bluetooth range of the field devices 1a; 1b is initially limited by artificially limiting the transmission power below a technically possible transmission power. The field device 1a; 1b periodically transmits telegrams using its field device transmit / receive unit 4. The terminal device 2a; 2b periodically listens to the wireless channel of the communication link KV using the terminal transmit / receive unit 5. As soon as the terminal transmit / receive unit 5, as in Fig. When the device receives the telegrams TG shown in Figure 1 from the field device transceiver unit 4, it immediately responds with another telegram TG to request more data from the field device 1a, 1b. This step is also referred to in the prior art as "advertising and scanning" (here with active scanning), for example, within the framework of the aforementioned BLE standard.

[0043] Preferably, the further telegram TG that the terminal device transmitting / receiving unit 5 sends as an immediate response to one of the telegrams TG periodically sent by the field device transmitting / receiving unit 4 as part of the "advertising and scanning" is used as a distance estimate telegram TGX. Preferably, the mobile terminal device 2a; 2b therefore only needs to scan for telegrams TG and, upon receipt, immediately respond with the distance estimate telegram TGX. The actual estimation of the physical distance and the determination of a current distance estimate Xid ti is carried out based on the received distance estimation telegrams TGX by the field device 1a; 1b or its computing / control unit 3 itself. Since many of the operating systems used on common mobile devices 2a; 2b, e.g. Android / iOS, scan in the background by default (e.g. as soon as a display is unlocked), the determination of the current distance estimation Xid tiparticularly suitable for practical use in the context of the method according to the invention.

[0044] In Fig. For the sake of simplicity, Figure 1 shows only the first field device 1a and the first mobile terminal 2a, showing how the distance estimate telegram TGX is sent via the communication connection KV from a terminal transmitting / receiving unit 5 of the mobile terminal 2a; 2b and received by the field device transmitting / receiving unit 4. The current distance estimate Xid ticorrelates with a current physical distance between the field device 1a and the mobile terminal and is determined by a computing / control unit 3 of the field device 1a. The field device transmitting / receiving unit 4 of the field device 1a is part of a Bluetooth module 9, which comprises programmable components of the computing / control unit 3 of the field device 1a. The field device 1a comprises a memory 31, in which the variables determined within the scope of the method according to the invention (see the following figure description for Fig. 2). If necessary, the computing / control unit 3 includes a timer as a time recording unit 8 for executing the method according to the invention.

[0045] The field device 1a is switched by the mobile terminal 2a when, based on the current distance estimate Xid tiIt is determined that the mobile device 2a is sufficiently close to the field device 1a. This preferably happens automatically when a user carries the mobile device 2a and moves it through the process plant.

[0046] When switching the field device 1a, it is, for example, put into an active communication mode in that the transmission power of the field device transmitting / receiving unit 4 is no longer artificially limited, thereby increasing the range of the communication connection KV.

[0047] Furthermore, upon switching, a field device display unit 6 (here an LED) flashes and / or changes color. In this way, the mobile terminal 2a can immediately detect that the field device 1a is located near the mobile terminal 2a.

[0048] Preferably, the mobile terminal 2a is configured to execute an operating program 7 for operating the field devices 1a, 1b, etc., for example, for executing the aforementioned "SmartBlue" app. Using the operating program 7, display elements for operating the field devices 1a, 1b (e.g., all of the applicant's field devices installed in the process plant) are displayed on the mobile terminal 2a. The display elements are represented here by individual boxes on a display unit of the mobile terminal 2a. Within the scope of the method according to the invention, in one embodiment, the display element belonging to the field device 1a located near the mobile terminal 2a is specifically highlighted (box with a solid border). In contrast, the display elements for all other field devices 2b, etc. are not specifically highlighted (boxes with a hatched border). The highlighting occurs simultaneously with the flashing of the LED field device display unit 6.In this way, a field device 1a; 1b can be very easily identified, e.g., for subsequent operation via the operating program 7, after it has been switched by the mobile terminal 2a via the communication connection KV.

[0049] The exact determination of the current distance estimate Xid ti is in Fig. 2 is shown in more detail.

[0050] In a first step of the Fig. 2 shown design (cf. Fig. 1) the distance estimate telegram TGX is sent by the terminal device transmitting / receiving unit 5 and received by the field device transmitting / receiving unit 4. The subsequent steps represent the concrete determination of the current distance estimate Xid ti by the computing / control unit 3 of the field device 1a; 1b.

[0051] The steps of the procedure for determining the current distance estimate Xid tiare at least partially implemented as a computer-aided method by means of an algorithm in the computing / control unit 3. As already mentioned above, the computing / control unit 3 is, in particular partially, assigned to a module 9 comprising the field device transmitting / receiving unit 4, e.g., a Bluetooth module - since, for example, a Bluetooth chip comprises (partially) programmable software - and / or the computing / control unit 3 is designed as an electronic component of the field device, e.g., a (programmable) microcontroller and / or an FPGA.

[0052] In a second step of the Fig. In the embodiment shown in Figure 2, the signal strength SP, together with a reception time information item EZ and an identification information item ID specific to the respective mobile terminal device 2a; 2b, is written into the memory 31 by the computing / control unit 3 and evaluated. The identification information ID is information by means of which the respective mobile terminal device 2a; 2b can be uniquely identified, for example a so-called MAC address (short for: "media access control") and / or an IP address. The identification information ID, the reception time information item EZ, and the signal strength SP are transferred, for example, from a Bluetooth stack of the Bluetooth module. The so-called "Received Signal Strength Indicator" (RSSI for short) of the distance estimate telegrams TGX received by the field device transceiver unit 4 is used as the signal strength SP.A high RSSI correlates with a short physical distance between the field device 1a,1b and the mobile device 2a,2b.

[0053] In a third step of the Fig. In the embodiment shown in Figure 2, it is checked whether a data set DS comprising the identification information ID is stored in the memory 31, that is, whether the mobile terminal 2a; 2b is known to the field device 1a; 1b, namely by the (recent) previous receipt of a distance estimation telegram TGX from the respective mobile terminal 2a; 2b.

[0054] In the event that no data set DS with the identification information ID is stored in the memory 31 (arrow “n” of the third step) and consequently no previous distance estimate Xid tj a last signal strength SP_i is used as the current distance estimate Xid tiThe last signal strength SP_i corresponds to the signal strength SP of a last received distance estimation telegram TGX.

[0055] In the event that a data set DS with the identification information ID is stored in the memory 31 (arrow “y” of the third step), the current distance estimate Xid ti determined based on both a previous distance estimate Xid tj , as well as based on the last signal strength SP_i. The previous distance estimate Xid tj was in turn determined based on a previous distance estimate telegram TGX received at a previous time tj. This is therefore a recursive procedure. The previous distance estimate Xid tjand the previous reception time tj (the latter can be determined from the reception time information EZ) are determined from the data set DS read from the memory 31. Subsequently, a time difference Δt between the last time ti and the previous time tj is determined. Finally, the current distance estimate Xid ti as a smoothed estimate. The contributions of the last signal strength SP_i and the previous distance estimate Xid tj to the current distance estimate Xid ti are taken into account by means of a smoothing coefficient α (Δt) which depends on the time difference Δt. The larger the time difference Δt, the stronger the last signal strength SP_i and the weaker the previous distance estimate Xid tj to the current distance estimate Xid tiThe smoothing coefficient α(Δt) is dependent on the time difference Δt and lies between 0 and 1. For example, the last signal strength SP_i and the previous distance estimate Xid tj weighted as follows: Xidti=α (Δt)*SP_i+[1−α (Δt)]*Xidtj, where α (Δt) = α0+ Δt / timeout * (1- α0). Here, α0 is a given (i.e. hard-coded) or predeterminable weighting parameter that lies between 0 and 1. In any case, Δt is always smaller than the given or predeterminable parameter timeout, since the memory is regularly emptied. This is explained in connection with the following description. Fig. 3. Therefore, 0< Δt / timeout < 1 always applies. For this reason, 0 < α (Δt) < 1 also applies in this example.

[0056] The current distance estimate Xid tiis written into the memory after its determination together with the reception time information EZ, the identification information ID and, if applicable, the current signal strength SP_i. If applicable, the data set DS belonging to a respective identification information ID in the memory 31 is also overwritten as soon as, triggered by the repeated reception of a distance estimate telegram TGX with the same identification information ID (i.e., from the same mobile terminal 2a; 2b) by the field device transmitting / receiving unit 4, the current distance estimate Xid ti is redetermined. After redetermining the current distance estimate Xid ti the previous distance estimate Xid ti no longer needed. The new, current distance estimate Xid ti is then added to the previous distance estimate Xid tjfrom a point in time of a repeated reception of a distance estimate telegram TGX with the same identification information ID.

[0057] In a fifth step of the Fig. 2, it is checked how the determined current distance estimate Xid ti to a given or predeterminable limit value GW. Does the current distance estimate Xid ti to the limit value GW such that the distance between the field device 1a; 1b and the mobile terminal 2a; 2b is estimated to be sufficiently small, e.g., to a value less than 0.5 m, preferably less than 0.2 m, the field device 1a; 1b is switched by means of the mobile terminal 2a; 2b, preferably automatically. This is done in the sixth step of the Fig. 2 shown configuration (box “s” for switch).

[0058] To prevent the memory 31 from filling up or to ensure that it is sufficiently small, a check is carried out for each data set DS in the memory 31 to determine how a time recorded with a time recording unit 8 behaves at the reception time EZP and the limit time interval timeout. In the event that no new distance estimation telegrams TGX are received from the field device transmitting / receiving unit 4 for a time interval that is greater than a predetermined limit time interval timeout (i.e., with a terminal device identification information ID that matches the terminal device identification information ID stored in the memory 31), the data set DS associated with the identification information ID is deleted from the memory 31. For example, in the Fig. 3 checks whether the recorded time time minus the reception time EZP is less than the limit time interval timeout: time−EZP <Timeout

[0059] If this is the case, the data set DS is deleted from memory 31. The specified timeout interval is less than five minutes, especially less than one minute, and preferably less than half a minute.

[0060] If necessary, a global variable "Proxy" that can assume the value "True" (T) or "False" (F) is used to test whether any mobile terminal 2a; 2b is sufficiently close to the field device 1a; 1b. The variable Proxy initially assumes the value Proxy=F, at which the field device 1a; 1b cannot be switched by the mobile terminal 2a; 2b. Proxy=T is only set if the current distance estimate Xid for at least one data set DS in the memory 31 tirelates to the limit value GW in such a way that the physical distance between the field device 1a; 1b and the mobile device 2a; 2b is estimated to be sufficiently small. Otherwise, the variable Proxy=F is set. If there is no mobile device 2a; 2b for whose current distance estimate Xid ti in the memory 31 e.g. Xid ti > GW applies (or Xid ti< GW, depending on the design of the method), Proxy=F applies. In this case, the field device 1a; 1b is returned, preferably automatically, to its previous state, so that, for example, the field device 1a; 1b is outside of the active communication mode and, accordingly, the range of the field device transmitting / receiving unit 4 is reduced again and / or the display of the field device display unit 6 is deactivated again and / or no longer advances. The value of the variable Proxy is continually redetermined, for example, triggered by the receipt of a new distance estimation telegram TGX and / or after the expiration of a time period of a limit time interval timeout (controlled by the time recording unit 8).

[0061] For example, the value automatically changes from T to F if a mobile terminal 2a;2b is no longer sufficiently close to the field device 1a;1b due to a service technician carrying the mobile terminal 2a;2b continuing to walk, so that the data set DS is still present in the memory 31, but the switching condition (either Xid ti < GW or Xid ti > GW) is no longer met, or if, for example, the mobile terminal 2a; 2b is switched off, so that after the limit time interval timeout has elapsed, the data record DS belonging to the mobile terminal 2a; 2b is deleted from the memory 31. Reference signs and symbols 100 systems 1a, 1b field devices 2a, 2b mobile devices 3 Computing / control unit 31 storage 4 Field device transmitter / receiver unit 5 Terminal transmitting / receiving unit 6 Field device display unit 7 Operating program 8 Time recording unit 9 Module KV communication connection TG Telegrams TGX, TGXi distance estimation telegrams Xid ti„ Xid1 ti , Xid2 ti current distance estimates Xid tj previous distance estimate DS data set ID identification information EZ reception time information GW limit SP, SP_i signal strength Δt time difference α(Δt) smoothing coefficient timeout limit time interval time time interval QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 120 297 A1

[0004]

Claims

[1] Method for establishing a wireless communication connection between a field device (1a; 1b) of automation technology and a mobile terminal (2a; 2b), for switching the field device (1a; 1b) by the mobile terminal (2a; 2b) by means of the wireless communication connection, the method comprising the steps: - Providing a field device (1a; 1b) of automation technology, wherein the field device (1a; 1b) comprises: --a programmable computing / control unit (3) --a field device transmitting / receiving unit (4) which can be controlled by the computing / control unit (3); - Providing a mobile terminal (2a, 2b) having a terminal transmitting / receiving unit (5), wherein the field device transmitting / receiving unit (4) and the terminal transmitting / receiving unit (5) are designed to communicate with each other by means of a wireless communication connection (KV), in particular using a predetermined frequency range, in particular according to a standardized communication protocol; - transmitting telegrams (TG) from the terminal transmitting / receiving unit (5) to the field device transmitting / receiving unit (4) and / or from the field device transmitting / receiving unit (4) to the terminal transmitting / receiving unit (5) via the wireless communication connection; - Determine a current distance estimate (Xid ti ) based on the transmitted telegrams (TG,TGX) which current distance estimate (Xid ti ) correlates with a current physical distance between the field device (1a; 1b) and the mobile terminal (2a; 2b); and - Switching the field device (1a; 1b) based on the current distance estimate (Xid ti ) [2] A method according to claim 1, comprising the steps of: - Comparison of the current distance estimate (Xid ti ) with a specified or specifiable limit value (GW); - In case that at least the current distance estimate (Xid ti ) either exceeds or falls below the limit value (GW): switching of the field device (1a; 1b). [3] Method according to at least one of the preceding claims, wherein at least one of the following steps is carried out during switching: - Switching the field device (1a; 1b) into an active communication mode in which an increased range of the field device transmitting / receiving unit (4) is present, compared to the range of the field device transmitting / receiving unit (4) outside the active communication mode, wherein the range is increased in particular to at least twice, preferably at least 10 times, compared to the range of the field device transmitting / receiving unit (4) outside the active communication mode; - Activating and / or changing a display, in particular an optical and / or acoustic display, which is displayed on a field device display unit (6). [4] Method according to at least one of the preceding claims, comprising the steps: - sending a distance estimate telegram (TGX) by the terminal device transmitting / receiving unit (5) and receiving the distance estimate telegram (TGX) from the field device transmitting / receiving unit; - Determination of a signal strength (SP) of the distance estimation telegram (TGX) by the computing / control unit; - Determine the current distance estimate (Xid ti ), based on at least the determined signal strength (SP) of the distance estimation telegram (TGX) by the computing / control unit. [5] Method according to claim 4, wherein the distance estimation telegram (TGX) comprises terminal identification information (ID) specific to the mobile terminal (2a; 2b) and / or wherein the field device transmitting / receiving unit determines reception time information (EZ) specific to a time of reception of the distance estimation telegram (TGX) by the field device transmitting / receiving unit, and wherein at least one of the following information is transmitted together with the determined signal strength (SP) from the field device transmitting / receiving unit to the computing / control unit: - the terminal identification information (ID), - the reception time information (EZ). [6] Method according to at least one of the preceding claims 4 to 5, wherein a data set comprising at least one of the following: - the signal strength (SP), the terminal identification information (ID), the reception time information, and the current distance estimate (Xid ti ), is stored in a writable and readable memory (31) of the computing / control unit (3). [7] Method according to at least one of the preceding claims 4 to 6, comprising the step: - Recurring transmission of distance estimate telegrams (TGX1, ...) by the terminal device transmitting / receiving unit (5) and receiving the recurringly transmitted distance estimate telegrams (TGX1, ...) from the field device transmitting / receiving unit. [8] Method according to at least one of the preceding claims 4 to 7, comprising the step: in the event that for a time interval (time), which time interval (time) is greater than a predetermined limit time interval (timeout), no distance estimation telegrams (TGX1,...) are received by the field device transmitting / receiving unit (4) which comprise a terminal device identification information (ID) matching a terminal device identification information (ID) of a data set (DS) stored in the memory (31): - deleting the data set (DS) from the memory (31), wherein the predetermined timeout interval is less than five minutes, in particular less than one minute, and preferably less than half a minute. [9] Method according to at least one of the preceding claims 4 to 8, wherein in the event that a previous distance estimate (Xid tj ) is stored, which previous distance estimate (Xid tj) was determined on the basis of a previous distance estimate telegram received at a previous time (tj), the step of determining the current distance estimate (Xid ti ) includes: - Determining a last signal strength (SP_i), which last signal strength (SP_i) corresponds to the signal strength (SP) of a last received distance estimation telegram and - Determining a last time (ti), which last time (ti) corresponds to the time of receipt of the last received distance estimate telegram; - Reading the previous distance estimate (Xid tj ) and the previous time (tj) from the memory (31); - Determining a time difference (Δt) between the last time (ti) and the previous time (tj); and - Determine the current distance estimate (Xid ti ) as a smoothed estimate, where the current distance estimate (Xid ti) from both the last signal strength (SP_i) and the previous distance estimate (Xid tj ) such that the contribution of the last signal strength (SP_i) and the previous distance estimate (Xid tj ) to the current distance estimate (Xid ti ) are taken into account by means of a smoothing coefficient (α (Δt)), which smoothing coefficient (α (Δt)) depends on the time difference (Δt); [10] Method according to claim 9, wherein the contribution of the last signal strength (SP_i) and the contribution of the previous distance estimate (Xid tj ) to the current distance estimate (Xid ti ) can be taken into account by means of the smoothing coefficient (α (Δt)) in such a way that - the larger the time difference Δt, the more the last signal strength (SP_i) and the less the previous distance estimate (Xid tj ) to the current distance estimate (Xid ti ) contributes. [11] Method according to at least one of claims 9 to 10, wherein the smoothing coefficient (α(Δt)) depends on the time difference (Δt) in such a way that the time difference (Δt) is included in the smoothing coefficient (α(Δt)) only in relation to the limit time interval (timeout), in particular as a quotient formed from the time difference (Δt) divided by the limit time interval. [12] Method according to at least one of the preceding claims 4 to 11, wherein in the event that no previous distance estimate (Xid tj ), the step of determining the current distance estimate (Xid ti ) includes: - Determine the current distance estimate (Xid ti ) as the last signal strength (SP_i), which last signal strength (SP_i) corresponds to the signal strength (SP) of a last received distance estimate telegram. [13] Method according to at least one of the preceding claims, wherein the mobile terminal (2a; 2b) is designed to execute at least one operating program (7) with a plurality of display elements and operating functionalities, wherein the field device (1a; 1b) can be operated by means of the operating program (7), wherein at least one of the following steps is carried out during the switching: - Displaying the field device (1a; 1b) in a display element of an operating program (7) executed by the mobile terminal (2a; 2b), in particular simultaneously with the activation and / or changing of the, in particular optical and / or acoustic, display on the field device display unit. [14] Method according to at least one of the preceding claims, wherein in the memory (31) - a first data set, the first data set comprising a first current distance estimate (Xid1 ti) and / or a first signal strength (SP1) of the first mobile terminal (2a), with a first terminal identification information (ID1) belonging to a first mobile terminal (2a) and - a second data set, the second data set comprising a second current distance estimate (Xid2 ti ) and / or a second signal strength (SP2) of the second mobile terminal (2b), with a second terminal identification information (ID2) belonging to a second mobile terminal (2b) is stored, where both the first current distance estimate (Xid1 ti ) as well as the second current distance estimate (Xid2 ti ) are such with respect to the limit value (GW) that the field device (1a; 1b) can be switched by both the first mobile terminal (2a) and the second mobile terminal (2b) by means of the wireless communication connection, and wherein the method comprises the following step to be carried out before switching the field device (1a; 1b): - Selection of one of the two mobile terminals (2a, 2b) for switching, based on at least one of the following: - a comparison of the first current distance estimate (Xid1 ti ) with the second current distance estimate (Xid2 ti ) - a comparison of the first signal strength (SP1) with the second signal strength (SP2). [15] Automation system (100), comprising: - a field device (1a, 1b) of automation technology, comprising: --a programmable computing / control unit (3) and --a field device transmitting / receiving unit (4) which can be controlled by the computing / control unit (3); and - a mobile terminal (2a; 2b) having a terminal transmitting / receiving unit (5); wherein the system is designed to carry out the method according to at least one of steps 1 to 14.

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