Abstract:
There is described a method to operate a mobile operating device and a mobile operating device, with which machines within of effective ranges which are spanned by RFID transponders can be operated wirelessly. A safety module is provided in the operating device, with which both measured values assigned to the RFID transponders and also reference values of two reference transponders simulated in the operating device are checked in order to ensure the correct measurement and further processing in this way.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of European Patent Office application No. 07015226.9 EP filed Aug. 2, 2007, which is incorporated by reference herein in its entirety. 
       FIELD OF INVENTION 
       [0002]    The invention relates to a method for using a mobile operating device and a mobile operating device with which at least one machine can be operated within a plant in a safety-relevant manner 
       BACKGROUND OF INVENTION 
       [0003]    It is not permitted to carry out hazardous actions at machines/plants in the safety-relevant environment from any location. Previously it was only possible to operate these systems at stationary points or with cabled devices. These limiting factors are however overcome by wireless transmission technologies. To comply with the requirements of safety technology ranges must be technically defined and there must be a unique assignment to these ranges. The practice of defining corresponding effective ranges is already known, within which a machine can be operated wirelessly by means of an operating device. In such cases the effective ranges are delimited by one or more RFID transponder. High demands as regards safety are imposed on the use of such operating devices in conjunction with the function of the effective ranges. To save money and development costs, such devices are developed where possible according to a standard process using standard components available. However these components are still to be included in the safety function. 
       SUMMARY OF INVENTION 
       [0004]    An underlying object of the invention is thus to propose a method of the type specified above, which ensures that the radio signals received by the operating device are processed correctly in order to make their use in the safety-relevant area possible. 
         [0005]    Another object of the is to propose an operating device of the type described above with which the correct further processing of the received radio signals is ensured, to make it possible to use said operating device in the safety-relevant environment. 
         [0006]    The aim here is to check the entire transmission chain of hardware and software components for determining transponder data. 
         [0007]    The first object is achieved by a method with the features as claimed in a first independent claim. The further object is achieved by a mobile operating device with the features as claimed in a further independent claim. 
         [0008]    Advantageous developments of the invention are to be taken from the subclaims. 
         [0009]    For the method the mobile operating device is provided. The mobile operating device has a read device for receiving the radio signals sent out by RFID transponders in an plant and an evaluation unit for evaluation of these radio signals. At least one machine can be operated within a plant in a safety-relevant manner, with operation being undertaken within an effective range assigned to the machine which is delimited by one or more RFID transponders. 
         [0010]    An especially advantageous development of the inventive method is produced by the reference transponders being simulated by upwards modulation of corresponding reference transponder signals in the read device. 
         [0011]    It is also advantageous for a first and a second of the reference transponders to be assigned an identification number in each case and for the entire range of identification numbers of the RFID transponders located in the plant to be covered by these two identification numbers. 
         [0012]    If the reference transponder signals of the reference transponder modulated upwards in the read device are delayed by means connected downstream from the read device, through which an additional distance is simulated, the correct distance measurement and evaluation of the correct distance measurement can be checked in this way. The known delay namely results in an additional defined distance. 
         [0013]    If the reference transponder signals of the first reference transponder and those of the second reference transponder are modulated upwards alternately in the read device, it is thus possible to cater for any blocking of a bit which may occur. 
         [0014]    It is also of particular advantage if for expected values to be present in the safety module for the first reference transponder in respect of the identification number and the distances with and without delay of the reference transponder signals, which is compared with data determined via the transmission chain as regards the identification number and the distances with and without delay. In this way it is possible to check the entire transmission chain of hardware and software components for determination of the transponder data. 
         [0015]    Finally it also proves especially advantageous if for one of the two expected values for the distance with and without delay to be determined mathematically for the second reference transponder from one of the two measured distance values and the other of the two expected values respectively for the distance with and without delay. With these method steps it is possible to cater for a “Stuck AT error” in a simple manner for example. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0016]    An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. The figures show: 
           [0017]      FIG. 1  a system with a mobile, wirelessly communicating operating device for operation of machines in a safety-relevant environment, 
           [0018]      FIG. 2  an inventive operating device, 
           [0019]      FIG. 3  a table with the reference values of a first reference transponder and 
           [0020]      FIG. 4  a table with the reference values of a second reference transponder. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0021]      FIG. 1  shows a system for operating machines  2  or plants. System  1  features a controller  3  and a mobile operating device  4 , which has means for wireless communication, here specifically an RFID (Radio Frequency Identification) radio connection with the controller  3 . 
         [0022]    Command Signals via WLAN 
         [0023]    The operation of the machine  2  is only permitted after logging on in specific effective ranges which are spanned by specific RFID transponders  5 . Only after log on in these effective ranges can hazardous actions, e.g. operating machines, be undertaken. 
         [0024]    To comply with safety systems requirements ranges must already be defined and unique assignments must be made to these ranges. Accordingly the effective ranges WB which are spanned by one or more RFID transponders are defined for the system  1 . In this case the spatial definition of the effective ranges WB is determined by the antenna characteristic of the RFID transponder  5  as well as by the projectable maximum distance of the mobile operating device  4  to the relevant RFID transponder  5 . 
         [0025]    The mobile safety-relevant operating device  4  features non safety-relevant hardware and software components in an effective range module  6  which is supported by a safety module  7  with safety measures. This safety module  7  is used to check and ensure that the evaluation of the radio signals received in the effective range WB is correct. The effective range module  6  has a read device  8  for receiving radio signals as well as an evaluation unit  9  for evaluation of the radio signals. Coupled to the read device  8  are one or more reference transponders R, R 1 , R 2 , that are simulated by upwards modulation of the corresponding reference transponder signals in the read device  8 . As well as the direct coupling of the read device  8  to the evaluation unit  9  an intermediate connection of a delay line  11  between these two components is possible. 
         [0026]    Essentially two parameters are determined in the non-safety-relevant affective range module  6 . The first parameter is the evaluation of the identification number ID of the relevant RFID transponder  5  and the second parameter is the distance to the RFID transponder  5  measured during receiving of the identification number ID. These two parameters must be available to the safety module  7 . 
         [0027]    To be able to trust the parameters determined, reference measurements with reference transponders R, R 1 , R 2  are conducted independently of the ongoing measurements to the RFID transponders  5 . With these reference measurements the hardware and software components of the effective range module  6  that are responsible for determining the parameters needed, as well as the read device  8 —evaluation unit  9 —safety module  7  transmission chain are checked. The safety module  7  has a definite time and value-linked expected relationship to the received reference values. If this expected relationship is violated, i.e. if the expected values do not conform to the timings or values required, the effective range module  6  is no longer trusted and the safe state is assumed. 
         [0028]    To this end a simulated reference transponder R, R 1 , R 2  is injected into the read device  8  at defined points in time independently of the ongoing measurements to the RFID transponders  5 . Since the injected reference transponder signal is always stronger than a normal transponder signal, this ensures that a reference measurement is undertaken at specific time intervals. The identification number ID 1  or ID 2  of a first or second reference transponder R 1 , R 2  and the corresponding distance to these reference transponders are subsequently determined in the evaluation unit  9  with the injection of the reference signal. 
         [0029]    Since the reference transponder R, R 1 , R 2  is located in the effective range module  6  itself, the measured distance to the reference transponder must correspond to 0 m. However, in order to detect an error in which the distance measurement always delivers the reference distance value 0 m, the delay  11  is additionally provided, which increases the reference distance value by 3 m. Each measurement is undertaken in the following two steps, regardless of whether a reference transponder R, R 1 , R 2  or a normal RFID transponder  5  is involved. 
         [0030]    First step:
       Measurement of the distance without delay line  11 .       
 
         [0032]    Second step:
       Measurement of the distance with delay line  11 .       
 
         [0034]    This means that the result of each measurement, in addition to the identification number ID, delivers a first distance value and a distance value increased by three meters. With the delay line  11  the range of values can be additionally increased and additional information produced about the measurement itself. 
         [0035]    At least two reference transponders R 1 , R 2  should have been provided, of which the signals are injected alternately at specific intervals x into the read device  8 . Their identification numbers ID 1 , ID 2  are selected in accordance with  FIGS. 3 and 4  with 0x0000 and 0xFFFF so that they cover the entire area of all RFID transponders  5  in the plant and allow the blocking of a bit to be detected. To cater for the range of values of the distance measurement, the measured distance is additionally subtracted from the maximum range of values in a reference measurement—as shown in the table depicted in  FIG. 4  for the reference transponder R 2 . In the table depicted in  FIG. 3  the measured resistance values of the reference transponder R 1  as well as the associated expected values are also mapped. 
         [0036]    The inventive mobile operating device  4  is designed so that all measurement data of the effective range module  6  can be forwarded without intermediate storage to the safety module  7 , i.e. the measured values for the reference transponders R, R 1 , R 2  take the same path as the measured values of the RFID transponder  5  of the plant.