Method and Device for Determining a Definite Distance

Abstract

A method for determining a definite safe distance between a wirelessly communicating object transponder and at least one anchor gateway in accordance with a two-way ranging method, wherein transmission and reception timestamps are detected for each communication message via the transponder and the at least one anchor gateway, each of the timestamps from the transponder and the at least one anchor gateway together with at least one respective piece of timestamp monitoring information are transmitted to a failsafe computing device, at least one check is implemented via the failsafe computing device, and the definite safe distance is determined via the failsafe computing device aided by the checked timestamps, where timestamp errors occurring during the detection of the timestamps are caused solely by the transponder or alternatively solely the one anchor gateway.

Claims

1.-9. (canceled)

10. A method for determining a definite safe distance (d.sub.TWR) between a wirelessly communicating object transponder (T) and at least one anchor gateway (G1-G3), each of which having detectors for detecting timestamps, in accordance with a two-way ranging method, the method comprising: a) detecting transmission and reception timestamps (T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL, T.sub.SGW_RX_FINAL) for each communication message via the transponder (T) and the at least one anchor gateway (G1-G3); b) transmitting each of the timestamps (T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL, T.sub.SGW_RX_FINAL) from the transponder (T) and the at least one anchor gateway (G1-G3) together with at least one respective piece of timestamp monitoring information (CRC1, CRC2) to a failsafe computing device (F-CPU); c) implementing at least one check via the failsafe computing device (F-CPU), selected from the following: c1) checking a correctness of respective timestamps (T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL, T.sub.SGW_RX_FINAL) based on the at least one piece of timestamp monitoring information (CRC1, CRC2); and c2) checking the calculated duration for the processing times of the transponder (T) and that of the at least one anchor gateway (G1-G3) based on known empirical values; and d) determining the definite safe distance (d.sub.TWR) via the failsafe computing device (F-CPU) aided by the checked timestamps (T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL, T.sub.SGW_RX_FINAL), wherein timestamp errors occurring during the detection of the timestamps (T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL, T.sub.SGW_RX_FINAL) are caused solely by the transponder (T) or alternatively solely by one anchor gateway of the at least two anchor gateways (G1-G3); and wherein a poll message, a response message and a final message (MP, MR, MF) are sent and received during the wireless communication between the object transponder (T) and the at least one anchor gateway (G1-G3) for a localization poll.

11. The method as claimed in claim 9, wherein an indicator value (safe_twr_value) for a definite safe distance measurement is determined via the failsafe computing device (F-CPU) based on the following relationship, which is a measure for reliability of the calculated definite safe distance (d.sub.TWR): $\mathrm{safe}\_\mathrm{twr}\_\mathrm{value}=\frac{\left(T_{Round1}-T_{\mathrm{GW}\_\mathrm{REPLY}}\right)-\left(T_{Round2}-T_{\mathrm{TAG}\mathrm{REPLY}}\right)}{2}$ where
T.sub.Round1=2.Math.TOF.sub.1+T.sub.GW_REPLY
T.sub.Round2=2.Math.TOF.sub.2+T.sub.TAG_REPLY
T.sub.GW_REPLY=T.sub.SGW_TX_RESP−T.sub.SGW_RX_POLL
T.sub.TAG_REPLY=T.sub.STAG_TX_FINAL−T.sub.STAG_RX_RESP and TOF.sub.1 or TOF.sub.2 is the respective signal propagation delay between the transponder (T) and one anchor gateway of the at least two anchor gateways (G1-G3), and time stamps T.sub.STAG_TX_POLL, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL are detected by the transponder (T), and time stamps T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.SGW_RX_FINAL are detected by one anchor gateway of the at least two anchor gateways (G1-G3).

12. The method as claimed in claim 9, wherein a transaction number (RNR) is generated by the failsafe computing device (F-CPU) and transmitted by the failsafe computing device (F-CPU) together with the response message (MR) from the at least one anchor gateway (G1-G3) to the object transponder (T).

13. The method as claimed in claim 9, wherein the transaction number (RNR) is a random number.

14. The method as claimed in claim 9, wherein the timestamp monitoring information (CRC1, CRC2) comprises a piece of parity information.

15. The method as claimed in claim 9, wherein a communication address of at least one of the object transponder (T) and the at least one anchor gateway (G1-G3) is taken into account during the calculation of the timestamp monitoring information (CRC1, CRC2).

16. The method as claimed in claim 9, wherein definite safe distances (d.sub.TWR) are determined in each case at a first and a second point in time, from which distances a movement speed of the transponder (T) is calculated, and the movement speed is compared with a predefined limit value.

17. A device for determining a definite safe distance (d.sub.TWR) between a wirelessly communicating object transponder (T) and at least one anchor gateway (G1-G3), each of which having detectors for detecting timestamps, via a failsafe computing device (F-CPU) in accordance with a two-way ranging method, wherein the device is configured to: a) detect transmission and reception timestamps (T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL, T.sub.SGW_RX_FINAL) for each communication message via the transponder (T) and the at least one anchor gateway (G1-G3), b) transmit each of the timestamps (T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL, T.sub.SGW_RX_FINAL) from the transponder (T) and the at least one anchor gateway (G1-G3) together with at least one respective piece of timestamp monitoring information (CRC1, CRC2) to a failsafe computing device (F-CPU), c) implement at least one check via the failsafe computing device (F-CPU), selected from the following: c1) check a correctness of respective timestamps (T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL, T.sub.SGW_RX_FINAL) based on the at least one piece of timestamp monitoring information (CRC1, CRC2); and c2) check the calculated duration for the processing times of the transponder (T) and that of the at least one anchor gateway (G1-G3) based on known empirical values; and d) determine the definite safe distance (d.sub.TWR) via the failsafe computing device (F-CPU) aided by the checked timestamps (T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL, T.sub.SGW_RX_FINAL), wherein timestamp errors occurring during the detection of the timestamps (T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL, T.sub.SGW_RX_FINAL) are caused solely by the transponder (T) or alternatively solely by one anchor gateway of the at least two anchor gateways (G1-G3); and wherein a poll message, a response message and a final message (MP, MR, MF) are sent and received during the wireless communication between the object transponder (T) and the at least one anchor gateway (G1-G3) for a localization poll.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the attached drawings, in which:

[0053] FIG. 1 shows an exemplary embodiment of a warning and protection system in accordance with the invention;

[0054] FIG. 2 shows an exemplary flowchart for definite safe determination of the distance in accordance with the invention;

[0055] FIG. 3 shows an exemplary poll message in accordance with the prior art;

[0056] FIG. 4 shows an exemplary TWR response message in accordance with the prior art;

[0057] FIG. 5 shows an exemplary response message in accordance with the invention;

[0058] FIG. 6 shows an exemplary TWR final message in accordance with the invention; and

[0059] FIG. 7 shows an exemplary final message in accordance with the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0060] FIG. 1 shows an exemplary embodiment of a warning and protection system.

[0061] A respective poll signal P1-P3 that comprises a poll message MP (“Poll”) is transmitted into a radio channel by an object transponder or “tag” T, which is worn on the body of a person P, for example.

[0062] The respective poll signal P1-P3 is received from the radio channel by the respective gateway G1-G3, processed further and retransmitted as a respective response signal R1-R3 that comprises a respective response message MR (“Response”).

[0063] The response signals R1-R3 are received by the object transponder T, processed further and retransmitted into the radio channel as a respective final signal F1-F3 which comprises the respective final message MF (“Final”).

[0064] The final signals F1-F3 are received by the respective gateway G1-G3 and transferred to a computing device F-CPU operating in a failsafe manner, which determines the protection radius r.sub.P of a safety zone S.

[0065] When a hazard system, for example, in the form of a production plant, is in operation and during this time a robot arm R of the production plant encroaches into the safety zone S, an abort action is triggered to cause the robot arm to halt its operation, as a result of which the robot arm instantly comes to a stop.

[0066] The intervention into the safety zone S may occur, for example, as a result of the person P approaching the robot arm R impermissibly closely, and personal protection is no longer reliably ensured.

[0067] A method according to the TWR principle that is intended for determining a definite safe distance d.sub.TWR between a wirelessly communicating object transponder T and at least one anchor gateway G1-G3, each of which having detectors for detecting timestamps, is described below with reference to an exemplary embodiment of the invention.

[0068] Generally, the following steps are performed during the method: [0069] a) detecting transmission and reception timestamps T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL, T.sub.SGW_RX_FINAL for each communication message via the transponder T and the at least one anchor gateway G1-G3, [0070] b) transmitting each of the timestamps T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL, T.sub.SGW_RX_FINAL from the transponder T and the at least one anchor gateway G1-G3 together with at least one piece of respective timestamp monitoring information CRC1, CRC2, for example, a piece of parity information, to a failsafe computing device F-CPU, [0071] c) implementing at least one check via the failsafe computing device (F-CPU), selected from the following: [0072] c1) checking the correctness of the respective timestamps T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL T.sub.SGW_RX_FINAL based on the at least one piece of timestamp monitoring information CRC1, CRC2, and [0073] c2) checking the calculated duration for the processing times of the transponder T and that of the at least one anchor gateway G1-G3 based on known empirical values, and [0074] d) determining the definite safe distance d.sub.TWR via the failsafe computing device F-CPU with the aid of the checked timestamps T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL, T.sub.SGW_RX_FINAL,

[0075] where timestamp errors occurring during the detection of the timestamps T.sub.STAG_TX_POLL, T.sub.SGW_RX_POLL, T.sub.SGW_TX_RESP, T.sub.STAG_RX_RESP, T.sub.STAG_TX_FINAL, T.sub.SGW_RX_FINAL are caused solely by the transponder T or alternatively solely by the at least one anchor gateway G1-G3.

[0076] From this, an indicator value safe_twr_value for a definite safe distance measurement can be determined via the failsafe computing device F-CPU based on the following relationship, which is a measure for the reliability of the calculated definite safe distance d.sub.TWR:

[00002]$\mathrm{safe}\_\mathrm{twr}\_\mathrm{value}=\frac{\left(T_{Round1}-T_{\mathrm{GW}\_\mathrm{REPLY}}\right)-\left(T_{\mathrm{Round}2}-T_{\mathrm{TAG}\_\mathrm{REPLY}}\right)}{2}$

[0077] where

T.sub.Round1=2.Math.TOF.sub.1+T.sub.GW_REPLY

T.sub.Round2=2.Math.TOF.sub.2+T.sub.TAG_REPLY

T.sub.GW_REPLY=T.sub.SGW_TX_RESP−T.sub.SGW_RX_POLL

T.sub.TAG_REPLY=T.sub.STAG_TX_FINAL−T.sub.STAG_RX_RESP

[0078] and TOF.sub.1 or TOF.sub.2 is the respective signal propagation delay between the transponder T and one of the at least two anchor gateways G1-G3.

[0079] During the wireless communication, a poll message, a response message and a final message MP, MR, MF are sent and received between the object transponder T and the at least one anchor gateway G1-G3 for a localization poll.

[0080] Furthermore, a transaction number RNR can be generated by the failsafe computing device F-CPU and transmitted together with the response message MR. The transaction number RNR is a random number, for example.

[0081] An address of the object transponder T or of the at least one anchor gateway G1-G3 can also be taken into account in the calculation of the timestamp monitoring information CRC1, CRC2.

[0082] FIG. 2 shows an example of a flowchart for determining the definite safe distance d.sub.TWR, with reference to which the invention is described in detail.

[0083] A definite safe distance is a true distance that is determined without systemic errors during a time-of-flight measurement.

[0084] Undesirable effects, caused, for example, by a fluctuating or inaccurate time base, which can occur during a time-of-flight measurement of signals, are systemically excluded by a corresponding definite “safe” calculation.

[0085] The position of the object transponder T (also known as a “tag”) in a three-dimensional space is to be determined in accordance with the statements presented hereinafter, where reference is made to the anchor or gateway transponders G1, G2, G3 at known positions.

[0086] The poll message MP is sent at the transponder T or tag at a time having a timestamp T.sub.STAG_TX_POLL and received at the respective anchor gateway G1-G3 at a time having a timestamp T.sub.SGW_RX_POLL.

[0087] The transmission of the poll message MP in the radio channel between the transponder T and the respective gateway of the three gateways G1-G3 requires a duration TOF.sub.1 (“time of flight”).

[0088] The poll message MP is processed by the anchor gateway within a time interval T.sub.GW_REPLY and a corresponding response message MR from the anchor gateway to the transponder T is sent at a time having a timestamp T.sub.SGW_TX_RESP and received at the tag at a time having a timestamp T.sub.STAG_RX_RESP.

[0089] The time interval T.sub.GW_REPLY is determined by the clock pulse of the gateway component T.sub.GW_CLK and is known within certain and known limits.

[0090] The following can thus be specified:

T.sub.GW_REPLY=T.sub.SGW_TX_RESP−T.sub.SGW_RX_POLL

[0091] The time interval T.sub.Round1 denotes the signal propagation delay between the timestamp T.sub.STAG_TX_POLL and the timestamp T.sub.STAG_RX_RESP.

T.sub.Round1=T.sub.STAG_RX_RESP−T.sub.STAG_TX_POLL

[0092] The transmission in the radio channel requires the duration TOF.sub.2. If the transponder T has not been moved, then TOF.sub.1=TOF.sub.2 applies.

[0093] The response message MR is processed by the tag within a time interval T.sub.TAG_REPLY and a corresponding final message MF is sent from the anchor gateway to the transponder T at a time having a timestamp T.sub.STAG_TX_FINAL.

[0094] The time interval T.sub.TAG_REPLY is determined by the clock pulse of the gateway component T.sub.TAG_CLK and is known within certain and known limits.

[0095] The transmission in the radio channel requires the duration TOF.sub.3. If the transponder T has not been moved, then TOF.sub.1=TOF.sub.2=TOF.sub.3 applies.

[0096] The anchor gateway receives the final message MF at a time having a timestamp T.sub.SGW_RX_FINAL.

[0097] The time interval T.sub.Round2 denotes the signal propagation delay between the timestamp T.sub.SGW_TX_RESP and the timestamp T.sub.SGW_RX_FINAL.

T.sub.Round2=T.sub.SGW_RX_FINAL−T.sub.SGW_TX_RESP

[0098] The following can thus be specified:

T.sub.TAG_REPLY=T.sub.STAG_TX_FINAL−T.sub.STAG_RX_RESP

[0099] The timestamps are detected by a tag counter CT in the object transponder or by a gateway counter CG in the anchor transponder.

[0100] The signal propagation delay in the radio channel can be determined from the calculated times of flight TOF=TOF.sub.1=TOF.sub.2=TOF.sub.3 and the corresponding distance d.sub.TWR via the speed of light c.

[00003]$\mathrm{TOF}=\frac{T_{Round1}.T_{Round2}-T_{G{W}_{REPLY}}.T_{\mathrm{TAG}\_\mathrm{REPLY}}}{T_{Round1}+T_{Round2}+T_{{\mathrm{GW}}_{\mathrm{REPLY}}}+T_{\mathrm{TAG}\_\mathrm{REPLY}}}{d}_{\mathrm{TWR}}=c.Math.\mathrm{TOF}$

[0101] The computing device F-CPU can now detect a first error if the timestamps of the transponder and the gateways required for calculating the distance are falsified.

[0102] It is assumed in this case that only errors on the part of the transponder T or alternatively only errors on the part of one of the gateways G1-G3 happen at the same time, and not errors on the part of the transponder and a gateway simultaneously.

[0103] A systemic error is understood to mean an error that adversely affects the generation or detection of timestamps, for example, an undesirably deviating time base in an electronic component, which may be caused by changing temperature, aging, component tolerances or similar. Such an error can occur between individual components in a system, such as the transponder T and a gateway G1-G3, because a local time base in the form of a clock generation for a digital electronics circuit changes erratically.

[0104] Timestamps or a drift of a respective timer clock pulse in a component, such as the transponder T1 or the gateways G1-G3, are independent of one another. Consequently, an error affects only the timestamp of the component in question and not those of the other components.

[0105] TWR features integrated error detection. This is based on the following relationships:

T.sub.Round1=2.Math.TOF.sub.1+T.sub.GW_REPLY

T.sub.Round2=2.Math.TOF.sub.2+T.sub.TAG_REPLY

[0106] A deviation from TOF, i.e., the difference between TOF.sub.1 and TOF.sub.2 due to errors in the transponder or in the gateway, can now be calculated by the relationship

[00004]$\mathrm{safe}\_\mathrm{twr}\_\mathrm{value}=\frac{\left(T_{Round1}-T_{\mathrm{GW}\_\mathrm{REPLY}}\right)-\left(T_{\mathrm{Round}2}-T_{\mathrm{TAG}\mathrm{REPLY}}\right)}{2}$

[0107] A TWR result is valid for safe.sub.twrvalue<safe_twr_value_limit at safe_twr_value_limit=825 ps, otherwise the result is invalid.

[0108] With the value safe_twr_value_limit=825 ps, a clock drift for the transponder is limited at <±200 ppm.

[0109] Also shown in the figure in simplified form as part of the flowchart is a program P_T of the transponder T comprising method steps PT1-PT3 for the transponder T.

[0110] A program P_G of a respective gateway G1-G3 comprising method steps PG1-PG3 for the respective gateway G1-G3 can also be seen, as well as a program P_F of the failsafe computing device F-CPU comprising method steps PF1-PF4 for the computing device F-CPU.

[0111] In step PT1, the poll message MP is initiated by the transponder T and sent.

[0112] In step PG1, the respective gateway receives the poll message MP and determines the transmission time point for the response message MR.

[0113] In step PF1, a random number RNR is generated by the failsafe computing device F-CPU and sent to the respective gateway.

[0114] In step PG2, the gateway sends a response message MR containing the random number RNR to the transponder T.

[0115] In step PT2, the response message MR is received by the transponder T and the transmission time point for the final message MF is calculated.

[0116] In step PT3, the transponder T determines a first checksum CRC1 from the timestamps and the address of the transponder T, as well as the random number, and sends a final message MF containing the first checksum CRC1 from the transponder T to the gateway.

[0117] In step PG3, the gateway receives the final message MF and determines a second checksum CRC2 from the timestamps and the address of the gateway and the first checksum CRC1 and transmits the timestamps and the address of the gateway and of the transponder T, as well as the second checksum CRC2, to the device F-CPU.

[0118] In step PF2, the device F-CPU calculates a third checksum CRC3 and compares the third checksum CRC3 with the second checksum CRC2.

[0119] In step PF3, the device F-CPU calculates a definite safe value safe_twr_value for the distance between the gateway and the transponder T via the TWR method and submits the values to a plausibility check.

[0120] In step PF4, the device F-CPU calculates the desired definite safe distance with the aid of the preceding relationship in respect of the signal propagation delay in the radio channel TOF.

[0121] FIG. 3 shows by way of example a poll message MP_TWR in accordance with the prior art for TWR, which comprises data elements for a sequence number MPSN, a destination address MPZA, a source address MPQA and a function code MPFC, and which can also be used, for example, as a poll message MP in the method in accordance with the disclosed embodiments of the invention.

[0122] FIG. 4 shows by way of example a response message MR_TWR in accordance with the prior art for TWR, which comprises data elements for a sequence number MRSN, a destination address MRZA, a source address MRQA and a function code MRFC.

[0123] FIG. 5 shows by way of example the response message MR in accordance with the invention, which comprises data elements for a sequence number MRSN, a destination address MRZA, a source address MRQA and a function code MRFC. The function code MRFC may be different from that of the prior art.

[0124] The random number RNR is included in addition.

[0125] FIG. 6 shows by way of example the final message MF in accordance with the prior art for TWR, which comprises data elements for a sequence number MFSN, a destination address MFZA, a source address MFQA and a function code MFFC. The function code MFFC may be different from that of the prior art.

[0126] In addition, the final message MF contains a data element for a time difference MFRXTX, which denotes the time elapsed between the transmission of the poll message MP and the reception of the response message MR via the transponder T. The final message MF also includes a data element for a time difference MFTXRX, which denotes the time elapsed between the reception of the response message MR and the transmission of the final message MF via the transponder T.

[0127] FIG. 7 shows by way of example the final message MP according to the invention, which comprises data elements for a sequence number MPSN, a destination address MPZA, a source address MPQA and a function code MPFC. The function code MFFC may be different from that of the prior art.

[0128] The final message MP further contains a data element in the form of a timestamp in each case for a poll transmission time point MF_PTX, a response reception time point MF_RRX, and a final transmission time point MF_FTX.

[0129] The final message MP also contains the first checksum CRC1, which is formed by way of the timestamps of the transponder T and by way of the random number RNR.

[0130] Thus, while there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the methods described and the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.