This invention relates to robot arms and to methods for locating robot arms.
Robotic systems that incorporate robot arms can be used in many situations where repeatability and/or precision of movement is desirable. One example of such robotic systems is a robotic surgical system.
It is highly desirable, especially in a robotic surgical system, that the position of a robot arm is known. This enables the motion of the arm to be accurately controlled, preventing damage to objects and/or people in the vicinity of the robot arm. This can be achieved in some systems by connecting several robot arms to a base unit. It is then possible to determine the relative positions of the arms to one another, using the base unit as a frame of reference.
The base unit is typically a common base unit, to which the several robot arms are connected.
In other systems, it is necessary to determine the location of each robot arm prior to use. This can be done by manoeuvring the arm so that the distal end of the arm touches a known point in the environment, such as on an operating table. Positional information could also be manually entered into the robotic system.
For separable robot arms, the need to carry out these separate calibration steps prior to use introduces delays into the system. These delays can be compounded where an arm is moved from one place to another, since the calibration step must then be carried out again when the arm is newly placed and before it can be used.

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It may be difficult, or impossible, for an arm to be manoeuvred in a calibration step where the operating environment is crowded. In such cases, either the arm cannot be used, or it must be used without being able to accurately determine its location.
There is a need for an improved robot arm, and an improved method for locating a robot arm.
SUMMARY
According to one aspect of the present invention there is provided a robot arm comprising a mounting portion configured for mounting in a socket so as to support the robot arm, the mounting portion comprising a reader for reading a location identifier so as to determine the location of the robot arm.
The provision of a reader permits the determination of the location of the robot arm when mounted in the socket. The robot arm may be for use in a robotic surgical system.
Suitably the robot arm is a surgical robot arm.
Suitably the reader is configured to communicate with a processor for processing a signal received from the reader. Suitably the reader is configured to communicate with the processor at least in part by a wireless connection. This can minimise wiring needed and/or can increase flexibility of positioning of the reader on the robot arm. Suitably the reader is configured to send to the processor a signal in dependence on the reading by the reader of the location identifier. Suitably the processor is configured to receive the signal from the reader and to determine the location of the robot arm in dependence on the signal received from the reader.
The robot arm may comprise the processor. Suitably the processor is configured to send the result of the location determination to a central controller configured to control the robot arm.

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The processor may be configured to send information, for example the signal received from the reader, to the central controller. The central controller may be configured to determine the location of the robot arm in dependence on the information received from the processor, for example in dependence on the signal received from the reader.
Suitably the processor is remote from the robot arm. Suitably a central controller configured to control the robot arm comprises the processor.
Suitably the reader is provided on a portion of the mounting portion which is arranged to be within the socket when the mounting portion is mounted in the socket.
The reader may be provided at an exterior location, for example on an exterior surface, of the mounting portion, to allow the reader to read location identifiers adjacent or near to the robot arm. The mounting portion may comprise a window, and the reader may be provided within the mounting portion such that it can read location identifiers through the window. This arrangement can provide the reader with some physical protection from knocks and/or environmental conditions.
Suitably the reader is configured to read the location identifier at least one of optically and magnetically. Suitably the window is at least one of optically and magnetically transparent, to permit optical and/or magnetic reading of the location identifier by the reader through the window. Suitably the window is a solid material. The reader may be a code reader, for example a QR code reader. The location identifier may be an optical code such as a QR code. Provision of a reader which can read an orientation-specific code such as a QR code can enable the reader to determine additional information, for example orientation information, as well as location information.
The window may comprise a hole in the mounting portion. The whole of the mounting portion may comprise the window. Suitably the mounting portion is transparent to permit the reading of the location identifier by the reader. In other words, the whole of

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the mounting portion may be transparent. The whole of the mounting portion, or a portion of the mounting portion, may act as the window.
The reader may be configured to read the location identifier electromagnetically, for example via at least one of radio waves, inductively and capacitively. Suitably the window is electromagnetically transparent, to permit electromagnetic reading of the location identifier by the reader through the window. The window is considered transparent if the reader can read the location identifier through the window.
Suitably the reader is configured to read a matrix bar code or a 2D bar code. Suitably the location identifier comprises a matrix bar code or a 2D bar code. The reader may be configured to read a magnetic code or pattern. Suitably the location identifier comprises a magnetic code or pattern. The reader may be configured to read one or more of a RFID identifier, an inductive identifier and a capacitive identifier. The location identifier may comprise one or more of a RFID identifier, an inductive identifier and a capacitive identifier.
The robot arm may comprise a light for illuminating the location identifier. The provision of the light can permit the reader to read the location identifier even in low light conditions. Suitably the mounting portion comprises the light. The robot arm may comprise a light sensor for sensing the light level. The light may be arranged to turn on in dependence on the light level sensed by the light sensor. The robot arm may comprise a local power source for powering at least one of the reader, the light and the light sensor. The robot arm may comprise a power connection permitting the robot arm to be connected to an external source of power for powering at least one of the reader, the light and the light sensor.
According to another aspect of the present invention, there is provided a robotic system comprising the robot arm as defined above and a socket configured to receive at least a portion of the mounting portion of the robot arm. The robotic system may be a robotic surgical system.

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According to another aspect of the present invention, there is provided a socket configured to receive at least a portion of the mounting portion of the robot arm.
The socket may comprise the location identifier. Suitably the location identifier is provided at an interior location, for example on an inside surface, of the socket. This arrangement allows the reader to easily read the location identifier when the mounting portion is mounted in the socket. This arrangement also restricts inadvertent reading of the location identifier by a reader of a robot arm not mounted in the socket.
The socket may be configured to receive the mounting portion of the robot arm in a plurality of orientations. Suitably the plurality of orientations are arranged rotationally about an axis of insertion of the mounting portion into the socket. The socket may comprise a plurality of location identifiers, each corresponding to a respective one of the plurality of orientations.
The socket is preferably configured so that the respective ones of the plurality of location identifiers are aligned with the reader when the mounting portion is mounted in the socket in the respective ones of the plurality of orientations.
Suitably the socket is movable between a first location and a second location so that a single socket can be used to mount the robot arm in the first and second locations. The socket may be movable between the first and second locations with the robot arm mounted in the socket. Suitably the socket comprises a first socket window through which one of a first location identifier at the first location and a second location identifier at the second location can be read by the reader. Suitably the first socket window is configured to be aligned with the reader when the mounting portion is mounted in the socket.
Suitably the socket comprises a plurality of socket windows through which the plurality of location identifiers can be read by the reader. Suitably the plurality of socket windows correspond to the plurality of location identifiers. In other words, the plurality of socket windows may correspond to the plurality of orientations.

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Suitably the first socket window and/or at least one of the plurality of socket windows is at least one of optically and magnetically transparent, to permit optical and/or magnetic reading of the location identifier by the reader. Suitably the first socket window and/or at least one of the plurality of socket windows is a solid material.
Suitably the first socket window and/or at least one of the plurality of socket windows is electromagnetically transparent, to permit electromagnetic reading of the location identifier by the reader, for example via at least one of radio waves, inductively and capacitively.
The socket may be movable on or along a mounting apparatus, the mounting apparatus comprising a plurality of indexed mounting locations. The indexed mounting locations can include the first location and the second location. In other words, the mounting apparatus may provide for the socket to be located in discrete mounting locations on or along the mounting apparatus. Suitably each indexed mounting location is provided with a respective location identifier. The respective location identifiers may be provided at an exterior location, for example on an exterior surface, of the mounting apparatus adjacent the respective indexed mounting location.
Suitably the mounting apparatus is a crenellated rail. The socket may be configured to be beatable at positions along the crenellated rail adjacent at least some of the protrusions and/or recesses of the rail. The crenellated rail may comprise location identifiers at positions adjacent at least some of the protrusions and/or recesses of the rail. That is to say, the crenellated rail may comprise location identifiers at positions adjacent or near to the positions along the crenellated rail at which the socket is beatable.
Suitably the socket comprises a socket power connection for connecting to the power connection of the robot arm. Suitably the socket comprises a signal connection for connecting to the robot arm to transfer signals from the robot arm to a central controller configured to control the robot arm.

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The robotic system may comprise the processor. The robotic system may comprise the central controller.
According to another aspect of the present invention, there is provided a method of determining the location of a robot arm, the robot arm comprising a mounting portion, the mounting portion comprising a reader, the method comprising mounting at least a portion of the mounting portion in a socket, reading a location identifier with the reader and in dependence on the reading of the location identifier with the reader, determining the location of the robot arm.
The method may comprise sending a signal from the reader to a processor and determining at the processor the location of the robot arm. The processor may be a remote processor.
The robot arm may comprise a light, and the method may comprise turning on the light to illuminate the location identifier, and reading the location identifier with the reader when the light is on.
The robot arm may comprise a light sensor, and the method may comprise sensing with the light sensor the light level, determining whether the light level is sufficient to illuminate the location identifier to be read by the reader, and if not, of turning the light on.
Any one or more feature of any aspect above may be combined with any one or more feature of any other aspect above. Any apparatus feature may be written as a method feature where possible, and vice versa. These have not been written out in full here merely for the sake of brevity.
BRIEF DESCRIPTION OF DRAWINGS

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The present invention will now be described by way of example only with reference to the accompanying drawings. In the drawings:
Figure 1 schematically shows a robot arm;
Figure 2a schematically shows a mounting portion of a robot arm and a socket;
Figure 2b schematically shows the mounting portion of figure 2a mounted in the socket
of figure 2a;
Figure 3 shows a partial section of a socket;
Figure 4 shows a crenellated rail;
Figure 5 shows a process of determining the location of a robot arm;
Figure 6 shows another process of determining the location of a robot arm;
Figure 7 shows another process of determining the location of a robot arm; and
Figure 8 shows another process of determining the location of a robot arm.
DETAILED DESCRIPTION
Robotic surgical systems permit precise control of surgical implements and the like by a surgeon through use of one or more robot arm. Typically the surgeon works at a remote workstation rather than directly at a surgical opening in a patient. The use of a robot arm permits use of various surgical tools which can be inserted through a smaller surgical opening than used in traditional surgery. The smaller surgical openings needed for surgery can improve patient recovery time following surgery.
A robot arm 10 for use in robotic surgical systems is shown schematically in figure 1. The robot arm 10 comprises a plurality of arm segments 12 coupled to one another by a plurality of joints 14. A tool portion 16 for carrying a surgical tool (not shown) is provided towards the distal end of the robot arm 10, and a mounting portion 18 is provided towards the proximal end of the robot arm 10. In some examples the joints 14 are one or other of revolute joints and prismatic joints. In some examples the joints are some combination of revolute, prismatic and/or other forms of joint. The joints 14 permit the tool portion to move relative to the mounting portion 18 such that the robot

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arm 10 can be controlled to position a tool carried by the tool portion 16 in a desired position and orientation.
In some examples the surgical tool carried by the tool portion 16 of the robot arm 10 can be changed during a surgical procedure. In some examples it is desirable to leave the surgical tool in place on the robot arm 10, and to change the robot arm 10 instead. Thus, it is desirable that the robot arm 10 can easily be mounted to and demounted from the robotic surgical system.
In some examples, whether or not the surgical tool carried by the tool portion 16 of the robot arm 10 is to be changed, it is desirable to change the position of the robot arm 10. This might be the case when, for example, the robot arm 10 is to be used on a different surgical site in the same procedure, or in the same surgical site but in a different configuration. In these examples as well, it is desirable that the robot arm 10 can easily be mounted to and demounted from the robotic surgical system.
In some examples, a robotic surgical system comprises a central controller which receives inputs, for example from a surgeon workstation, and outputs control signals to a robot arm 10 to effect desired movement of the robot arm 10. For the central controller to accurately control the movement of the robot arm 10 it is desirable for the location of the robot arm 10 to be known. Therefore, before the robot arm 10 is used in the surgical procedure, its location is input into the system.
Where, as in some examples mentioned, robot arms are changed either at the start of or during a surgical procedure, it is desirable for the location of each robot arm to be input to the system with minimal delay and/or maximal accuracy. This approach enables efficient use of the system in a surgical procedure. If long delays were introduced when moving robot arms, this would prolong the surgical procedure, which is undesirable.
The robot arm 10 is mountable in a socket 22. This is shown schematically in figure 2. The robot arm 10 is mountable in the socket 22 by the mounting portion 18. Figure 2a

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shows the mounting portion 18 (the remainder of the robot arm 10 is omitted here for clarity) and the socket 22 separate from one another, and figure 2b shows the mounting portion 18 within the socket 22. The socket 22, in some examples, forms part of the robotic surgical system. The socket 22 is configured to receive at least a portion of the mounting portion 18 of the robot arm 10 so as to hold the robot arm 10 in place. The mounting portion 18 is, in some examples, configured to cooperate with the socket 22. In some examples the mounting portion 18 is configured to be seated substantially within the socket 22. This can provide a more firm hold of the robot arm 10 by the socket 22.
In one example the mounting portion 18 is cylindrical and is configured to lock into place in the socket 22. The mounting portion 18, in one example, comprises a projecting lug which is receivable into a recess or channel in the socket 22. The lug is receivable into a first channel portion on insertion of the mounting portion 18 into the socket 22 in a mounting direction. The mounting portion 18 is rotatable about the axis of insertion (along the mounting direction) to enable the lug to pass into a second channel portion which communicates with and is configured at an angle to the first channel portion. The second channel portion is configured to retain the lug so that the mounting portion 18 is retained in the socket 22. In one configuration the mounting portion 18 is not removable from the socket 22 without being rotated again about the axis of insertion so as to cause the lug to move into the first channel portion.
Two or more lugs, and two or more recesses or channels could also be used. Where a plurality of lugs and recesses are used, it is preferable for the lugs to be spaced about the circumference of the mounting portion and for the recesses to be correspondingly spaced about the circumference of the socket. Equal spacing of the lugs and recesses can assist in stability of the retention of the mounting portion in the socket.
Similarly, one or more lugs may be provided on the socket, and a corresponding one or more recesses or channels may be provided on the mounting portion.

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Other mechanisms for locking the mounting portion in place in the socket will be apparent to the skilled person.
An approach to easily and/or accurately determine the location at which a robot arm 10 is located is to use location identifiers. A location identifier can be provided at a particular location so as to identify that location. The location identifier may uniquely identify the location. The location identifier can be read by a reader. The reading by the reader of the location identifier indicates that the reader is at the particular location.
In one example the reader is configured to produce a signal on reading a location identifier. The signal is sent to a processor. The processor is configured to determine the location in dependence on the signal. In one example the processor is configured to use the signal to reference a look-up table, from which the location can be determined. In another example the location identifier may directly identify the location, so that the processor is enabled to determine the location on the basis of the signal. For example, the signal may provide details of the location at which the location identifier giving rise to that signal is located.
The mounting portion 18 comprises a reader 20 for reading location identifiers. In some examples, the socket 22 comprises a location identifier 26 (see figure 3). In some examples the location identifier is provided at an interior location, for example on an inside surface 27, of the socket. The mounting portion 18 and the socket 22 are configured so that, on mounting the mounting portion 18 in the socket 22, the reader 20 is able to read the location identifier 26.
In some examples the location identifier 26 is configured to be read optically. In some examples the location identifier 26 is additionally or alternatively configured to be read magnetically. The reader 20 is configured to read location identifiers at least one of optically and magnetically. For example, the location identifier 26 can be an optical code such as a QR code, and the reader 20 can be an optical code reader such as a QR code reader. In some examples the reader 20 is a camera.

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In some examples the location identifier 26 is configured to be read electromagnetically, for example via radio waves, inductively and/or capacitively. In these examples, the reader 20 is configured to read the location identifier electromagnetically, for example via at least one of radio waves, inductively and capacitively.
The reader 20 is, in some examples, provided on an exterior surface of the mounting portion 18. In other examples, the reader 20 is provided in the interior of the mounting portion 18 and the mounting portion 18 is configured so that the reader 20 is able to read location identifiers in the vicinity of the mounting portion 18. In some examples the mounting portion 18 comprises a window (not shown) through which the reader can read location identifiers. The provision of the window can provide some environmental protection to the reader 20. In some examples, the window is solid, for example glass or plastic such as clear plastic. The window is configured to be at least partially transparent such that the reader 20 is able to read location identifiers through the window. In other words, where the location identifier is read optically, the window is at least partially optically transparent so that the reader 20 can optically read the location identifier 26 through the window. Where the location identifier is read magnetically, the window is at least partially magnetically transparent so that the reader 20 can magnetically read the location identifier 26 through the window.
Where the location identifier 26 is configured to be read electromagnetically, the window is at least partially electromagnetically transparent.
In some examples, such as where the socket 22 is movable, the location identifier 26 is not provided on the socket 22 itself, but is instead provided adjacent or near to the socket 22 location. In some examples, where the socket 22 is movable, a plurality of location identifiers are provided, each adjacent or near to one of the socket 22 locations.
In some examples, the socket 22 comprises a first socket window 24 (the first socket window 24 is shown in dashed lines in figure 2a to indicate that it is optional). The first

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socket window is provided such that the location identifier 26 can be read by the reader 20 through the first socket window 24. In other words, when a robot arm 10 is mounted in the socket 22, the reader 20 can read the location identifier 26 through the first socket window. Reference is made to figure 2b, which shows the mounting portion 18 mounted in the socket 22; the reader 20 is aligned with the first socket window 24, and is able to read location identifiers through the first socket window 24.
In some examples, the first socket window 24 is at least partially optically and/or magnetically transparent. This permits the reader 20 to read location identifiers optically and/or magnetically through the first socket window 24. In some examples the first socket window 24 is solid. In some examples the first socket window is glass or plastic, such as clear plastic. This can provide some environmental protection to the reader 20 and/or the mounting portion 18 when mounted in the socket 22. It can also restrict entry of environmental material, such as dust and/or detritus, into the socket 22 interior.
In some examples, the first socket window 24 is at least partially electromagnetically transparent. This permits the reader 20 to read location identifiers electromagnetically through the first socket window 24.
Where the location identifier 26 is provided on an exterior surface, this can include attaching the location identifier 26 to the exterior surface by adhesive, such as sticking an optical code and/or a magnetic code onto the surface. It can also include etching a pattern such as an optical code into the surface.
Providing the location identifier 26 on an exterior surface can also include magnetising the surface in a pattern, or attaching one or more of a RFID identifier, an inductive identifier and a capacitive identifier to the surface.
In some examples, the robotic system comprising the mounting portion 18 and the socket 22 has a plurality of configurations. The robotic system is in some examples configured so that the mounting portion 18 is mountable in the socket 22 in a plurality

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of orientations. For example, the plurality of orientations can be arranged rotationally about an axis of insertion of the mounting portion 18 into the socket 22. In one example, a first orientation is arranged at a 90 degree rotational offset from a second orientation. In this example, the robotic system is configured so that the socket 22 permits mounting of the robot arm 10 in either of the first or second orientation. This permits additional flexibility in the use of the robot arm 10. In this example, each of the first and second orientations has associated therewith a respective location identifier 26. These are provided such that on mounting the robot arm 10 in the first orientation, the reader 20 is enabled to read the location identifier associated with the first orientation; on mounting the robot arm 10 in the second orientation, the reader 20 is enabled to read the location identifier associated with the second orientation. In this way, the location and orientation of the robot arm 10 can be determined.
The location identifiers are, in some examples, associated with the first and second orientations by being provided on an interior, such as on an interior surface, of the socket 22. The location identifiers are provided spaced from one another, by 90 degrees around the socket 22 in this example. This may be the case where the socket 22 is not movable.
i The location identifiers are, in some examples, associated with the first and second orientations by being provided adjacent or near to the socket 22. In this example the socket 22 comprises the first socket window and a second socket window, spaced from the first socket window by a 90 degree rotation about the socket 22 axis. One of the location identifiers is provided adjacent or near to the first socket window and the
i other of the location identifiers is provided adjacent or near to the second socket window. In this way, the reader 20 can read one of the location identifiers through the first socket window when the robot arm 10 is mounted in the socket 22 in the first orientation. The reader 20 can read the other of the location identifiers through the second socket window when the robot arm 10 is mounted in the socket 22 in the
i second orientation.

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In more general terms, the plurality of location identifiers associated with the plurality of orientations (and the plurality of socket windows, where present) are spaced from one another about the axis of the socket. They need not be equally spaced, depending on the desired configurations.

We Claim

A surgical robot arm comprising a mounting portion configured for mounting in a
socket so as to support the robot arm, the mounting portion comprising a reader for
reading a location identifier so as to determine the location of the robot arm,
wherein the reader is provided on a portion of the mounting portion which is arranged to be within the socket when the mounting portion is mounted in the socket.
2. A surgical robot arm as claimed in claim 1, wherein the reader is configured to communicate with a processor for processing a signal received from the reader, the reader being configured to send to the processor a signal in dependence on the reading by the reader of the location identifier.
3. A surgical robot arm as claimed claim 2, wherein the robot arm comprises the processor, and the processor is configured to receive the signal from the reader and to determine the location of the robot arm in dependence on the signal received from the reader.
4. A surgical robot arm as claimed in claim 3, wherein the processor is configured to send the result of the location determination to a central controller configured to control the robot arm.
5. A surgical robot arm as claimed in any preceding claim, wherein the reader is configured to read the location identifier electromagnetically.
6. A surgical robot arm as claimed in any preceding claim, wherein the reader is a 2D code reader.
7. A surgical robot arm as claimed in any preceding claim, wherein the robot arm comprises a light for illuminating the location identifier.

8. A surgical robot arm as claimed in any preceding claim, wherein the robot arm comprises a light sensor for sensing the light level.
9. A surgical robotic system comprising the robot arm as claimed in any preceding claim and a socket configured to receive at least a portion of the mounting portion of the robot arm.

10. A surgical robotic system as claimed in claim 9, wherein the socket comprises the location identifier.
11. A surgical robotic system as claimed in claim 9 or claim 10, wherein the socket is configured to receive the mounting portion of the robot arm in a plurality of orientations.
12. A surgical robotic system as claimed in any of claims 9 to 11, wherein the socket is movable between a first location and a second location so that a single socket can be used to mount the robot arm in the first and second locations.
13. A surgical robotic system as claimed in claim 12, wherein the socket is movable between the first and second locations with the robot arm mounted in the socket.
14. A surgical robotic system as claimed in claim 12 or claim 13, wherein the socket comprises a first socket window through which one of a first location identifier at the first location and a second location identifier at the second location can be read by the reader.
15. A surgical robotic system as claimed in claim 14, wherein the first socket window is configured to be aligned with the reader when the mounting portion is mounted in the socket.
16. A surgical robotic system as claimed in any of claims 12 to 15, wherein the socket comprises a plurality of socket windows through which the plurality of location identifiers can be read by the reader.

17. A surgical robotic system as claimed in any of claims 14 to 16, wherein the first socket window and/or at least one of the plurality of socket windows is at least one of optically and electromagnetically transparent, to permit optical and/or electromagnetic reading of the location identifier by the reader.
18. A surgical robotic system as claimed in any of claims 12 to 17, wherein the socket is movable on or along a mounting apparatus, the mounting apparatus comprising a plurality of indexed mounting locations.
19. A surgical robotic system as claimed in claim 18, wherein each indexed mounting location is provided with a respective location identifier.
20. A surgical robotic system as claimed in claim 18 or claim 19, wherein the mounting apparatus is a crenellated rail.
21. A method of determining the location of a surgical robot arm, the robot arm comprising a mounting portion configured for mounting in a socket so as to support the robot arm, the mounting portion comprising a reader provided on a portion of the mounting portion which is arranged to be within the socket when the mounting portion is mounted in the socket, the method comprising:
mounting at least a portion of the mounting portion in the socket, reading a location identifier with the reader, and
in dependence on the reading of the location identifier with the reader, determining the location of the robot arm.
22. A method as claimed in claim 21, wherein the robot arm comprises a light sensor,
and the method comprises sensing with the light sensor the light level, determining
whether the light level is sufficient to illuminate the location identifier to be read by the
reader, and if not, of turning the light on.