Patent Publication Number: US-2023146995-A1

Title: System and computer-implemented method for controlling a rotary milking parlor arrangement and computer program

Description:
TECHNICAL FIELD 
     The present invention relates generally to solutions in which animals are located on a rotating platform while being milked. Especially, the invention relates to a system for operating a rotating platform of a rotary milking parlor arrangement and a computer-implemented method for such a system. The invention also relates to a corresponding computer program for the method. 
     BACKGROUND 
     Today&#39;s automatic milking arrangements are highly complex in-stallations. In particular, a rotary milking parlor arrangement is one such example. Namely, here, a very heavy platform carrying a large number of animals rotates while milking machines milk the animals located thereon. Many powerful electric motors are required to effect the rotation of the platform. For example to adjust the rotation speed based on the milking characteristics of the animals currently on the platform, these motors must also be controllable with very high accuracy. Moreover, in case of an accident or a malfunction, it must be possible to stop and/or reverse the rotation of the platform as soon as possible. 
     Typically, one or more friction drive wheels are arranged below the platform, which wheels act on a drive surface of the platform to make it rotate. For the desired control, an integrated brake system may also be employed, for example as described in U.S. 2016/0278340. WO 2020/021521 discloses an example of another control solution. Here, an optimal angular velocity of the milking platform is computed to maximize the number of animals milked per unit of time. EP 2 060 173 shows a design, where the movement of the platform is varied in response to a current performance of a milking robot servicing the milking stalls on the platform. 
     The applicant has found that the efficiency and reliability of the rotary milking parlor arrangement can be improved if the drive mechanism is organized in one or more drive units that are arranged underneath the rotating platform to rotate the same. Each drive unit, in turn, may either include a single drive motor or a pair of drive motors cooperating with one another to reduce the slippage relative to a drive rail. 
     If a drive unit fails, for example due to drive motor breakdown, drive wheel or transmission/gear box malfunction, the overall possibilities to control the rotating platform deteriorates. In particular, retarding its movement can be made less efficient. In other words, from a given speed, it will take longer time to stop the platform. Of course, this has negative effects on the safety for both personnel and animals. 
     SUMMARY 
     The object of the present invention is therefore to offer a solution that provides an early notification of any malfunctioning drive units, so that appropriate safety measures can be taken. 
     According to one aspect of the invention, the object is achieved by a system for operating a rotary milking parlor arrangement that includes a rotating platform with a plurality of stalls each of which is configured to house a respective animal during milking. The arrangement includes one or more drive units configured to cause the rotating platform to move in at least a first direction of rotation around a rotation axis. The system includes a control unit, which is configured to obtain a respective first state of a first operation parameter of each of the drive unit(s) during operation of the rotating platform in a first mode of operation. The control unit is also configured to obtain a respective second state of the first operation parameter of each of the drive unit(s) during operation of the rotating platform in a second mode of operation. For example, the control unit may thus obtain information about a respective electric current to or torque of each drive unit in an idle mode and in steady-state operation respectively. The control unit is further configured to compare, for each of the drive unit, the first and second states of the first operation parameter with one another; and if, for one or more detected drive units a difference between the first and second states does not exceed a threshold level, the control unit is configured to gene- rate a first alarm with respect to the one or more detected drive units. In other words, if for example, the electric current to or torque of a particular drive unit is almost the same in idle mode as in steady-state operation, this drive unit is most probably defective—a circumstance that should be indicated by the first alarm. 
     The above system is advantageous because it enables identifying faulty drive units in a straightforward and reliable manner. Thus, appropriate measures can be taken to compensate for and mitigate the effects of any faulty drive units, for example by preventing operation of the rotating platform or reducing a maximum steady-state speed on each drive unit to compensate for a longer braking time resulting from the faulty drive unit(s) and/or issuing an inspection/service alarm on the faulty drive unit(s). The identification of any faulty drive unit with the first alarm can also be regarded as a software disengagement of any malfunctioning drive units in the meaning that the control unit cannot rely on the malfunctioning drive units in controlling the speed of the rotating platform. Namely, for each non-properly working drive unit, the capacity to operate, accelerate and retard/brake the rotating platform deteriorates. The braking capacity is here the most critical aspect from a safety point-of-view. 
     The first alarm not only involves an indication of a malfunctioning drive motor or transmission/gear box. Instead, depending on the situation, the first alarm may simply involve an indication of a worn-out drive wheel or a non-properly engaged drive wheel. In some types of rotary milking parlor arrangements, the drive units are manually turned into and secured in a position where the drive wheels engage a drive surface on the rotating platform. The system hereby also enables an identification of any improperly secured drive units. 
     According to one embodiment, each of the at least one drive unit contains at least one drive motor arranged to engage a drive surface of the rotating platform and, via at least one drive wheel act on the drive surface so as to cause the rotating platform to perform said movement, and the control unit, in response to the first alarm, is further configured to either prevent operation of the rotating platform or reduce a maximum steady-state speed of the rotating platform, and/or issue an inspection/service alarm on the faulty drive unit(s). Preferably, the rotary milking parlor arrangement hereby includes at least two such drive units. Accordingly, if one of the drive units is not working properly, the rotary milking parlor arrangement can remain in operation, while the maximum steady-state speed on the working drive unit(s) (including the faulty drive unit) is reduced for safety reasons. In other words, the rotating platform is not necessarily shut-down in response to the alarm indicating the faulty drive unit. The rotary milking parlor arrangement typically includes a higher number of drive units, such as any number from five to sixteen drive units, so the maximum allowed steady-state speed can be reduced stepwise in response to an increased number of indicated faulty drive units. 
     Each drive unit may include a single drive motor arranged to engage the drive surface of the rotating platform in a non-disengageable manner. In such a case, the drive unit is preferably manually secured in an position where the drive wheel engages the drive surface of the rotating platform. In other words, the non-disengageable manner hereby means that the drive unit cannot be (automatically) disengaged during operation of the rotary milking parlor arrangement. However, the drive unit can be manually disengaged after stopping the rotating platform. 
     Alternatively, each of the at least one drive unit may contain first and second drive motors arranged to engage two of said drive surfaces in the form of a drive rail of the rotating platform and, via respective drive wheels act on a respective side of the drive rail so as to cause the rotating platform to perform said movement. Thus, the first and second drive motors cooperate in an efficient manner. 
     According to one embodiment, in response to the first alarm, the control unit is further configured to send a first control signal to the one or more detected drive units, which first control signal is configured to cause the one or more detected drive units to be automatically/physically disengaged from the drive rail. This is beneficial because if one of the first and second drive motors works satisfactory while the other stands still, the opposing sides of the drive rail experience different degrees of resistance. This, in turn, may lead to the rotating platform derailing, which is both hazardous and costly. 
     According to a further embodiment, the first mode of operation involves operating the at least one drive unit in an idle mode in which no drive motor of any of the at least one drive unit is engaged to cause the rotating platform to move in the at least first direction of rotation around the rotation axis; and the second mode of operation involves operating the at least one drive unit in a steady-state mode in which the at least one drive unit is engaged to cause the rotating platform to move at a steady-state speed in the at least first direction of rotation around the rotation axis. Accordingly, the first operation parameter (such the current or torque) of the drive motor(s) is/are obtained/recorded when running the drive motor(s) in the non-engaged idle mode, whereby the first operation parameter (such as the current or torque) of the drive motor(s) obtained in the steady-state mode is/are compared with the reference values obtained in idle mode to determine if any drive motor(s) is/are malfunctioning. 
     According to another embodiment, the first mode of operation involves operating the at least one drive unit in a non-engaged ramp-up mode in which no drive motor of any of the at least one drive unit is engaged to cause the rotating platform to accelerate toward a steady-state speed in the at least first direction of rotation around the rotation axis; and the second mode of operation involves operating the at least one drive unit in an engaged ramp-up mode in which the at least one drive unit is engaged to cause the rotating platform to accelerate toward the steady-state speed in the at least first direction of rotation around the rotation axis. Accordingly, the first operation parameter (such the current or torque) of the drive motor(s) is/are obtained/recorded when running the drive motor(s) in the non-engaged (non-loaded) ramp-up operation to desired steady-state speed, wherein the first parameter can be used as reference values that may be plotted on reference curve, which is subsequently compared with the values/curve of the first parameter in the engaged ramp-up operation as the rotating platform is accelerated (from standstill) to the desired steady-state speed. Consequently, if the difference between the first and second states does not exceed the threshold level, the control unit is configured to generate the first alarm with respect to the one or more detected drive units during the ramp-up operation. 
     According to another embodiment, the arrangement includes at least three drive units. Here, if the difference between the first and second states exceeds the threshold level for each of the at least three drive units. I.e. the first checkpoint is passed, the control unit is further configured to, during operation of the rotating platform in the second mode of operation, obtain the first operation parameter for each of the at least three drive units, for instance the magnitude of the torque of each drive unit or the electric current fed thereto. The control unit is configured to compare, pairwise, the first operation parameter for each drive unit with the first operation parameter for each of the other drive units to derive a respective first difference value between each combination of drive units. Based on the first difference values, the control unit is configured to determine if the first operation parameter for a particular one of the drive units deviates from the first operation parameter for the other ones of the drive units by more than a first threshold difference. If so, the control unit is configured to generate a second alarm with respect to said particular one drive unit. Thus, a drive unit that shows a deviating performance in the second state (the second mode of operation) can be spotted as faulty. In other words, the embodiment detects a drive unit that may fail during the second mode of operation, e.g. in steady-state operation of the rotating platform. 
     According to still another embodiment, the control unit is further configured to obtain, during operation of the rotating platform in the second mode of operation, at least one second operation parameter for each of the at least three drive units, e.g. a respective magnitude of a voltage and/or a respective value of a frequency (rpm) thereto. Analogous to the above, the control unit is configured to compare, pairwise, the at least one second operation parameter for each of the drive units with the at least one second operation parameter for each other drive unit to derive a respective at least one second difference value between each combination of drive units. Based on said difference values, the control unit is configured to determine if the second operation parameter for a specific one of the drive units deviates from the second operation parameter for the other ones of the drive units by more than a second threshold difference. If so, the control unit is configured to generate a third alarm with respect to said specific one drive unit. This provides an additional means of detecting defective drive units. 
     According to another aspect of the invention, the object is achieved by a computer-implemented method of operating a rotary milking parlor arrangement that includes a rotating platform with a plurality of stalls each of which is configured to house a respective animal during milking. It is also presumed that the arrangement includes at least one drive unit configured to cause the rotating platform to move in at least a first direction of rotation around a rotation axis. The method involves obtaining a respective first state of a first operation parameter of each of the at least one drive unit during operation of the rotating platform in a first mode of operation. The method also involves obtaining a respective second state of the first operation parameter of each of the at least one drive unit during operation of the rotating platform in a second mode of operation. For each of the at least one drive unit, the first and second states of the first operation parameter are compared with one another. If, for one or more detected drive units a difference between the first and second states does not exceed a threshold level, the method involves generating a first alarm with respect to the one or more detected drive units. The advantages of this method, as well as the preferred embodiments thereof, are apparent from the discussion above with reference to the system. 
     According to a further aspect of the invention, the object is achieved by a computer program loadable into a non-volatile data carrier communicatively connected to a processing unit. The computer program includes software for executing the above method when the program is run on the processing unit. 
     Further advantages, beneficial features and applications of the present invention will be apparent from the following description and the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is now to be explained more closely by means of preferred embodiments, which are disclosed as examples, and with reference to the attached drawings. 
         FIG.  1    shows a rotating platform of a rotary milking parlor arrangement according to one embodiment the invention; 
         FIG.  2    illustrates a system for operating a rotating platform according to one embodiment the invention; 
         FIG.  3    shows a perspective view of a drive unit according to a first embodiment the invention; 
         FIG.  4    shows a perspective view of a drive unit according to a second embodiment the invention; 
         FIGS.  5   a - b    schematically illustrate the function of the drive unit according to the second embodiment of the invention; and 
         FIG.  6    illustrates, by means of a flow diagram, the general method according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    is showing a rotating platform  130 , which forms part of a rotary milking parlor arrangement. In this example, the rotating platform  130  has 18 milking stalls S. Of course, however, any higher or lower number of stalls S is conceivable according to the invention. Nevertheless, each stall S is configured to house a respective animal while being milked by a milking machine. 
     The system according to the invention includes at least one drive unit and a control unit  220 . The drive unit(s) cause the rotating platform  130  to move in at least a first direction RF of rotation around a rotation axis P. Depending on the size of the rotating platform  130 , the number of drive units may be anything from one and up to for instance sixteen. 
       FIG.  2    illustrates a system according to one embodiment of the invention for operating the rotating platform  130 . The system includes a control unit  220 , which is configured to obtain a respective first state of a first operation parameter p 11 , p 21 , p 31 , p 41  and p 51  of each of the drive units  241 ,  242 ,  243 ,  244  and  245  respectively during operation of the rotating platform  130  in a first mode of operation. 
     The first mode of operation may involve operating the drive units and the rotating platform  130  in an idle mode or non-engaged ramp-up mode in which no drive motor of any of the drive units  241 ,  242 ,  243 ,  244  or  245  is engaged to cause the rotating platform  130  to move in the at least first direction RF of rotation around a rotation axis P. Hence, the drive units are running in idle mode or non-engaged ramp-up mode and the rotating platform is standing still. A second mode of operation may involve operating the drive units and rotating platform  130  in a steady-state mode or engaged ramp-up mode in which the drive units  241 ,  242 ,  243 ,  244  and  245  are engaged to cause the rotating platform  130  to move at or accelerate to a steady speed in the at least first direction RF of rotation around the rotation axis P. 
     The first operation parameter p 11 , p 21 , p 31 , p 41  and p 51  may represent a respective magnitude of an electric current fed to each of the drive units  241 ,  242 ,  243 ,  244  and  245  in the first and second states respectively. Alternatively, the first operation parameter p 11 , p 21 , p 31 , p 41  and p 51  may represent a respective torque of each of the drive units or a respective magnitude of a voltage or a respective value of a frequency fed to each of the drive units  241 ,  242 ,  243 ,  244  and  245 . 
     Nevertheless, the control unit  220  is configured to obtain a respective second state of the first operation parameter p 11 , p 21 , p 31 , p 41  and p 51  of each of the drive units  241 ,  242 ,  243 ,  244  and  245  during operation of the rotating platform  130  in the second mode of operation. 
     For each of the drive units  241 ,  242 ,  243 ,  244  and  245 , the control unit  220  is configured to compare the first and second states of the first operation parameter p 11 , p 21 , p 31 , p 41  and p 51  with one another, for example the magnitude of a respective electric current fed to each drive unit in the idle mode and in the steady-state mode. If, for one or more detected drive units, say  241 , a difference between the first and second states does not exceed a threshold level, the control unit  220  is configured to generate a first alarm A 1  with respect to the one or more detected drive units, here  241 . 
     Generally, according to the invention, the first and second states are selected such that a drive unit operating as intended shows distinctly different values of the first operation parameter p 11 , p 21 , p 31 , p 41  and p 51  in the first and second states respectively. 
     According to the invention, each of the drive units  241 ,  242 ,  243 ,  244  and  245  includes at least one drive motor that is arranged to engage a drive surface of the rotating platform  130 . The at least one drive motor is therefore mechanically connected to at least one drive wheel, which, in turn, acts on the drive surface so as to cause the rotating platform  130  to perform its rotating movement. 
     Each drive unit  241 ,  242 ,  243 ,  244  and  245  is configured produce at least one respective signal p 11 , p 12  p 13 ; p 21 , p 22 , p 23 ; p 31 , p 32 , p 33 ; p 41 , p 42 , p 43  and p 51 , p 52  p 53  indicating a respective first, second and/or third operation parameter of the drive unit in question. The first operation parameter p 11 , p 21 , p 31 , p 41  and p 51  may represent a respective magnitude of an electric current fed to the drive units  241 ,  242 ,  243 ,  244  and  245  respectively or a respective torque of each of the drive units  241 ,  242 ,  243 ,  244  and  245 . The second operation parameter p 12 , p 22 , p 32 , p 42  and p 52  may represent a respective magnitude of a voltage fed to drive units  241 ,  242 ,  243 ,  244  and  245  respectively. The third operation parameter p 13 , p 23 , p 33 , p 43  and p 53  may represent a respective value of a frequency fed to the drive units  241 ,  242 ,  243 ,  244  and  245  respectively. 
       FIG.  3    shows a perspective view of a drive unit  241  according to a first embodiment the invention. Here, the drive unit  241  contains a single drive motor  341  that is arranged to engage drive surface of the rotating platform  130  in a non-disengageable manner as previously described. The drive unit  241  is shown in a non-engaged outer position used for recording the first operation parameter in an idle mode or a non-engaged ramp-up mode. The drive unit  241  may thereafter be secured into engagement by manually turning the drive unit into an inner position and locking an arm equipped with rollers  361  and  362  arranged to press a drive wheel  350  into a secure engagement with the drive surface on the rotating platform  130 . Since the drive motor  341  cannot be automatically disengaged from the inner locked or engaged position with the rotating platform  130 , a detected malfunction of the drive unit  342  can be considered as a software disengagement. This means that the control unit  220  cannot rely on the drive unit  342  when controlling the rotating platform  130 . In particular, in response to the first alarm A 1 , the control unit  220  may therefore be configured to reduce a maximum allowed steady-state speed of the rotating platform  130  and issue an inspection/service alarm on the drive unit  342  to the operator of the arrangement. 
       FIG.  4    shows a perspective view of a drive unit  242  according to a second embodiment the invention. Here, the drive unit  242  contains first and second drive motors  541  and  542  respectively (see also  FIGS.  5   a  and  5   b   ) that are arranged to engage a drive rail  230  of the rotating platform  130 . Specifically, each of the first and second drive motors  541  and  542  is mechanically connected to a respective drive wheel  551  and  552  that acts on opposing sides of the drive rail  230  so as to cause the rotating platform  130  to perform its rotating movement as described below with further reference to  FIGS.  5   a    and  5   b.    
     In response to the first alarm A 1 , the control unit  220  is preferably configured to send a first control signal C 2  to any drive unit  242  that has been detected as faulty. The first control signal C 2  is configured to cause the detected drive unit  242  to be automatically/physically disengaged from the drive rail  230 . 
       FIGS.  5   a  and  5   b    show schematic views of the drive unit  242  according to the second embodiment the invention.  FIG.  5   a    illustrates an operation of the drive unit  242  where the rotating platform  130  is caused to move in a first direction RF, say forward; and  FIG.  5   b    illustrates operation of the drive unit  242  where the rotating platform  130  is caused to move in a second direction RB, say backward. The first and second drive motors  541  and  542  are each arranged to engage a drive surface of the rotating platform  130  in the form of a drive rail  230 . The drive rail  230  is preferably located under the rotating platform  130 , and the drive rail  230  follows the circular outline of the rotating platform  130 . 
     Referring now again also to  FIG.  4   , the drive unit  242  includes an actuator  410 , which, in response to the control signal C 2  is configured to cause the drive unit  242  to be disengaged from the drive rail  230  by separating the first drive wheel  351  from the second drive wheel  352 . The actuator  410 , in turn, may include a pneumatic cylinder, a hydraulic cylinder or an electric linear motor that is arranged to separate the first and second drive wheels  551  and  552  from one another. 
     The first drive wheel  551  is arranged on a first side of the drive rail  230 , e.g. on the inside of a circular loop formed by the drive rail  230 . The first drive wheel  551  is operated by a first drive motor  541  in the drive unit  242 . The second drive wheel  552  is arranged on a second side of the drive rail  230 , e.g. on the outside of the circular loop, and is operated by a second drive motor  542  in the drive unit  242 . 
     Preferably, the drive unit  242  contains at least one clamping member, which, in an engaged mode, is configured to force the first drive wheel  551  towards the first side of the drive rail  230  and force the second drive wheel  352  towards the second side of the drive rail  230 . The embodiment of the invention shown in  FIG.  4    has two clamping members  421  and  422  respectively, which can be represented by resilient elements, such as helical and/or leaf springs. Hence, in practice, whenever the actuator  410  is inactivated, the clamping members  421  and  422  press the drive wheels  551  and  552  towards drive rail  230 , so that drive wheels  551  and  552  engage the drive wheel and may cause the platform  130  to rotate. Activation of the actuator  410  results in that the entire motor and drive wheel arrangements  541 / 551  and  542 / 552  respectively are swung away from one another by rotation around a pivot axis. 
     According to one embodiment of the invention, the arrangement includes at least three drive units  241 ,  242 ,  243 ,  244  and  245 . Here, if the difference between first and second states of the first operation parameter p 11 , p 21 , p 31 , p 41  and p 51  exceeds the threshold level for each of the at least three drive units  241 ,  242 ,  243 ,  244  and  245 , the control unit  220  is configured to execute the following steps. 
     During operation of the rotating platform  130  in the second mode of operation, here steady-state operation, the control unit  220  is configured to obtain the first operation parameter p 11 , p 21 , p 31 , p 41  and p 51  for each of the drive units  241 ,  242 ,  243 ,  244  and  245  respectively. The control unit  220  is further configured to compare, pairwise, the first operation parameter p 11 , p 21 , p 31 , p 41  and p 51  for each of the drive units  241 ,  242 ,  243 ,  244  and  245  with the first operation parameter p 11 , p 21 , p 31 , p 41  and p 51  for each of the other drive units  241 ,  242 ,  243 ,  244  and  245  to derive a respective first difference value between each combination of drive units of the at least three drive units  241 ,  242 ,  243 ,  244  and  245 . Based on the first difference values, the control unit  220  is configured to determine if the first operation parameter for a particular one of the drive units, say  242 , deviates from the first operation parameter for the other ones of the drive units  241 ,  243 ,  244  and  245  by more than a first threshold difference. If so, it is concluded that the drive unit  242  has an uncharacteristic operational behavior in the second mode of operation, here steady-state operation. Therefore, the control unit  220  is configured to generate a second alarm A 2  with respect to the drive unit  242 . 
     Alternatively, or additionally, according to one embodiment of the invention, and provided that the arrangement includes at least three drive units  241 ,  242 ,  243 ,  244  and  245 , the control unit  220  is configured to execute the following steps. 
     During operation of the rotating platform  130  in the second mode of operation the control unit  220  is configured to obtain at least one second operation parameter p 12 , p 22 , p 32 , p 42  and p 52  for each of the at least three drive units  241 ,  242 ,  243 ,  244  and  245 ; and compare, pairwise, the at least one second operation parameter p 12 , p 22 , p 32 , p 42  and p 52  for each of the drive units  241 ,  242 ,  243 ,  244  and  245  with the at least one second operation parameter p 12 , p 22 , p 32 , p 42  and p 52  for each of the other drive unit  241 ,  242 ,  243 ,  244  and  245  to derive a respective at least one second difference value between each combination of drive units  241 ,  242 ,  243 ,  244  and  245 . Based on the difference values, the control unit  220  is configured to determine if the at least one second operation parameter operation parameter p 12 , p 22 , p 32 , p 42  and p 52  for a specific drive unit, say  243 , deviates from the at least one second operation parameter for the other ones of the at least three drive units  241 ,  242 ,  244  and  245  by more than a second threshold difference. If so, analogous to the above, this interpreted as a sign of that the drive unit  243  has an uncharacteristic operational behavior in the second mode of operation. Therefore, the control unit  220  is configured to generate a third alarm A 3  with respect to the drive unit  243 . 
     It is generally advantageous if the control unit  220  is configured to effect the above-described procedure in an automatic manner by executing a computer program  227 . Therefore, the control unit  220  may include a memory unit  225 , i.e. non-volatile data carrier, storing the computer program  227 , which, in turn, contains software for making processing circuitry in the form of at least one processor  223  in the central control unit  220  execute the above-described actions when the computer program  227  is run on the at least one processor  223 . 
     In order to sum up, and with reference to the flow diagram in  FIG.  6   , we will now describe the general computer-implemented method according to the invention of operating a rotating platform of a rotary milking parlor arrangement. 
     In a first step  610 , a respective first state is obtained of a first operation parameter of each drive unit during operation of the rotating platform in a first mode of operation. 
     Then, in a step  620 , a respective second state is obtained of the first operation parameter of each drive unit during operation of the rotating platform in a second mode of operation. 
     In a subsequent step  630 , the first and second states of the first operation parameter are compared with one another for each of the drive units. 
     Thereafter, in a step  640 , it is checked if a respective difference between the first and second states of the first operation parameter is above a threshold for each of the drive units. If so, the procedure ends. Otherwise, a step  650  follows in which a first alarm is generated in respect of each drive unit for which said difference does not exceed the threshold. Then, the procedure ends. 
     All of the process steps, as well as any sub-sequence of steps, described with reference to  FIG.  6    may be controlled by means of a programmed processor. Moreover, although the embodiments of the invention described above with reference to the drawings comprise processor and processes performed in at least one processor, the invention thus also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice. The program may be in the form of source code, object code, a code intermediate source and object code such as in partially compiled form, or in any other form suitable for use in the implementation of the process according to the invention. The program may either be a part of an operating system, or be a separate application. The carrier may be any entity or device capable of carrying the program. For example, the carrier may comprise a storage medium, such as a Flash memory, a ROM (Read Only Memory), for example a DVD (Digital Video/Versatile Disk), a CD (Compact Disc) or a semiconductor ROM, an EPROM (Erasable Programmable Read-Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a magnetic recording medium, for example a floppy disc or hard disc. Further, the carrier may be a transmissible carrier such as an electrical or optical signal which may be conveyed via electrical or optical cable or by radio or by other means. When the program is embodied in a signal, which may be conveyed, directly by a cable or other device or means, the carrier may be constituted by such cable or device or means. Alternatively, the carrier may be an integrated circuit in which the program is embedded, the integrated circult being adapted for performing, or for use in the performance of, the relevant processes. 
     The term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components. However, the term does not preclude the presence or addition of one or more additional features, integers, steps or components or groups thereof. 
     The invention is not restricted to the described embodiments in the figures, but may be varied freely within the scope of the claims.