Abstract:
Exemplary embodiments include a portable articulated arm coordinate measuring machine including a manually positionable articulated arm portion having opposed first and second ends, the arm portion including a plurality of connected arm segments, each of the arm segments including at least one position transducer for producing position signals, a measurement device attached to the first end of the articulated arm coordinate measuring machine, an electronic circuit for receiving the position signals from the transducers and for providing data corresponding to a position of the measurement device, a base coupled to the second end, an upper mount portion disposed on the base, a lower mount portion fixed to a mounting structure and configured to repeatably connect to the upper mount portion and an electronic identification system configured to send identifier information identifying the lower mount portion to the electronic circuit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of provisional application No. 61/296,555 filed Jan. 20, 2010, the content of which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to a coordinate measuring machine, and more particularly to a portable articulated arm coordinate measuring machine having a repeatable base mount having an electronic base mount identification system. 
         [0003]    Portable articulated arm coordinate measuring machines (AACMMs) have found widespread use in the manufacturing or production of parts where there is a need to rapidly and accurately verify the dimensions of the part during various stages of the manufacturing or production (e.g., machining) of the part. Portable AACMMs represent a vast improvement over known stationary or fixed, cost-intensive and relatively difficult to use measurement installations, particularly in the amount of time it takes to perform dimensional measurements of relatively complex parts. Typically, a user of a portable AACMM simply guides a probe along the surface of the part or object to be measured. The measurement data are then recorded and provided to the user. In some cases, the data are provided to the user in visual form, for example, three-dimensional (3-D) form on a computer screen. In other cases, the data are provided to the user in numeric form, for example when measuring the diameter of a hole, the text “Diameter=1.0034” is displayed on a computer screen. 
         [0004]    An example of a prior art portable articulated arm CMM is disclosed in commonly assigned U.S. Pat. No. 5,402,582 (&#39;582), which is incorporated herein by reference in its entirety. The &#39;582 patent discloses a 3-D measuring system comprised of a manually-operated articulated arm CMM having a support base on one end and a measurement probe at the other end. Commonly assigned U.S. Pat. No. 5,611,147 (&#39;147), which is incorporated herein by reference in its entirety, discloses a similar articulated arm CMM. In the &#39;147 patent, the articulated arm CMM includes a number of features including an additional rotational axis at the probe end, thereby providing for an arm with either a two-two-two or a two-two-three axis configuration (the latter case being a seven axis arm). 
         [0005]    What is needed is an AACMM that can be quickly mounted and dismounted in a repeatable manner. 
       SUMMARY OF THE INVENTION 
       [0006]    Exemplary embodiments include a portable articulated arm coordinate measuring machine including a manually positionable articulated arm portion having opposed first and second ends, the arm portion including a plurality of connected arm segments, each of the arm segments including at least one position transducer for producing position signals, a measurement device attached to the first end of the articulated arm coordinate measuring machine, an electronic circuit for receiving the position signals from the transducers and for providing data corresponding to a position of the measurement device, a base coupled to the second end, an upper mount portion disposed on the base, a lower mount portion fixed to a mounting structure and configured to repeatably connect to the upper mount portion and an electronic identification system configured to send identifier information identifying the lower mount portion to the electronic circuit. 
         [0007]    Additional exemplary embodiments include a portable articulated arm coordinate measuring machine including a manually positionable articulated arm portion having opposed first and second ends, the arm portion including a plurality of connected arm segments, each of the arm segments including at least one position transducer for producing position signals, a measurement device attached to the first end of the articulated arm coordinate measuring machine, an electronic circuit for receiving the position signals from the transducers and for providing data corresponding to a position of the measurement device, a base coupled to the second end, an upper mount portion disposed on the base and a lower mount portion fixed to a mounting structure and configured to repeatably connect to the upper mount portion, wherein the upper mount portion and the lower mount portion are components of a curvic coupling or a Hirth coupling. 
         [0008]    Further exemplary embodiments include a method of operating a portable articulated arm coordinate measuring machine, with steps including providing a manually positionable articulated arm portion having opposed first and second ends, the arm portion including a plurality of connected arm segments, each of the arm segments including at least one position transducer for producing position signals, a measurement device attached to the first end of the articulated arm coordinate measuring machine, an electronic circuit for receiving the position signals from the transducers and for providing data corresponding to a position of the measurement device, a base coupled to the second end, and an upper mount portion disposed on the base, providing a first lower mount portion fixed to a first mounting structure and configured to repeatably connect to the upper mount portion, connecting the articulated arm coordinate measuring machine to the first lower mount portion and sending to the electronic circuit first identifier data that identifies the first lower mount portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Referring now to the drawings, exemplary embodiments are shown which should not be construed to be limiting regarding the entire scope of the disclosure, and wherein the elements are numbered alike in several FIGURES: 
           [0010]      FIG. 1 , including  FIGS. 1A and 1B , are perspective views of a portable articulated arm coordinate measuring machine (AACMM) having embodiments of various aspects of the present invention therewithin; 
           [0011]      FIG. 2 , including  FIGS. 2A-2D  taken together, is a block diagram of electronics utilized as part of the AACMM of  FIG. 1  in accordance with an embodiment; 
           [0012]      FIG. 3 , including  FIGS. 3A and 3B  taken together, is a block diagram describing detailed features of the electronic data processing system of  FIG. 2  in accordance with an embodiment; 
           [0013]      FIG. 4 , including  FIGS. 4A and 4B , are perspective views of curvic couplings and Hirth couplings, respectively, that are used as part of a mount for mounting the AACMM of  FIG. 1  in a specific location according to embodiments of an aspect of the present invention; 
           [0014]      FIG. 5  is a cross section view of a portion of the base of the AACMM of  FIG. 1  having the mount embodied therein according to embodiments of an aspect of the present invention; 
           [0015]      FIG. 6 , including  FIGS. 6A and 6B , are perspective views, partially cutaway, of the mount in unassembled and assembled positions, respectively, according to embodiments of an aspect of the present invention; and 
           [0016]      FIG. 7  illustrates a flow chart of a method for mounting the AACMM in accordance with exemplary embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Exemplary embodiments include a repeatable base mount having an electronic base mount identification system that associates a base-mount serial number with a prior measurement history for one or more AACMMs. The exemplary base mount allows the AACMM to be removed and repeatably replaced without the need to re-establish the frame of reference of the one or more AACMMs. 
         [0018]      FIGS. 1A and 1B  illustrate, in perspective, a portable articulated arm coordinate measuring machine (AACMM)  100  according to various embodiments of the present invention, an articulated arm being one type of coordinate measuring machine. As shown in  FIGS. 1A and 1B , the exemplary AACMM  100  may comprise a six or seven axis articulated measurement device having a measurement probe housing  102  coupled to an arm portion  104  of the AACMM  100  at one end. The arm portion  104  comprises a first arm segment  106  coupled to a second arm segment  108  by a first grouping of bearing cartridges  110  (e.g., two bearing cartridges). A second grouping of bearing cartridges  112  (e.g., two bearing cartridges) couples the second arm segment  108  to the measurement probe housing  102 . A third grouping of bearing cartridges  114  (e.g., three bearing cartridges) couples the first arm segment  106  to a base  116  located at the other end of the arm portion  104  of the AACMM  100 . Each grouping of bearing cartridges  110 ,  112 ,  114  provides for multiple axes of articulated movement. Also, the measurement probe housing  102  may comprise the shaft of the seventh axis portion of the AACMM  100  (e.g., a cartridge containing an encoder system that determines movement of the measurement device, for example a probe  118 , in the seventh axis of the AACMM  100 ). In use of the AACMM  100 , the base  116  is typically affixed to a work surface. 
         [0019]    Each bearing cartridge within each bearing cartridge grouping  110 ,  112 ,  114  typically contains an encoder system (e.g., an optical angular encoder system). The encoder system (i.e., transducer) provides an indication of the position of the respective arm segments  106 ,  108  and corresponding bearing cartridge groupings  110 ,  112 ,  114  that all together provide an indication of the position of the probe  118  with respect to the base  116  (and, thus, the position of the object being measured by the AACMM  100  in a certain frame of reference—for example a local or global frame of reference). The arm segments  106 ,  108  may be made from a suitably rigid material such as but not limited to a carbon composite material for example. A portable AACMM  100  with six or seven axes of articulated movement (i.e., degrees of freedom) provides advantages in allowing the operator to position the probe  118  in a desired location within a 360° area about the base  116  while providing an arm portion  104  that may be easily handled by the operator. However, it should be appreciated that the illustration of an arm portion  104  having two arm segments  106 ,  108  is for exemplary purposes, and the claimed invention should not be so limited. An AACMM  100  may have any number of arm segments coupled together by bearing cartridges (and, thus, more or less than six or seven axes of articulated movement or degrees of freedom). 
         [0020]    The probe  118  is detachably mounted to the measurement probe housing  102 , which is connected to bearing cartridge grouping  112 . A handle  126  is removable with respect to the measurement probe housing  102  by way of, for example, a quick-connect interface. The handle  126  may be replaced with another device (e.g., a laser line probe, a bar code reader), thereby providing advantages in allowing the operator to use different measurement devices with the same AACMM  100 . In exemplary embodiments, the probe housing  102  houses a removable probe  118 , which is a contacting measurement device and may have different tips  118  that physically contact the object to be measured, including, but not limited to: ball, touch-sensitive, curved and extension type probes. In other embodiments, the measurement is performed, for example, by a non-contacting device such as a laser line probe (LLP). In an embodiment, the handle  126  is replaced with the LLP using the quick-connect interface. Other types of measurement devices may replace the removable handle  126  to provide additional functionality. Examples of such measurement devices include, but are not limited to, one or more illumination lights, a temperature sensor, a thermal scanner, a bar code scanner, a projector, a paint sprayer, a camera, or the like, for example. 
         [0021]    As shown in  FIGS. 1A and 1B , the AACMM  100  includes the removable handle  126  that provides advantages in allowing accessories or functionality to be changed without removing the measurement probe housing  102  from the bearing cartridge grouping  112 . As discussed in more detail below with respect to  FIG. 2 , the removable handle  126  may also include an electrical connector that allows electrical power and data to be exchanged with the handle  126  and the corresponding electronics located in the probe end. 
         [0022]    In various embodiments, each grouping of bearing cartridges  110 ,  112 ,  114  allows the arm portion  104  of the AACMM  100  to move about multiple axes of rotation. As mentioned, each bearing cartridge grouping  110 ,  112 ,  114  includes corresponding encoder systems, such as optical angular encoders for example, that are each arranged coaxially with the corresponding axis of rotation of, e.g., the arm segments  106 ,  108 . The optical encoder system detects rotational (swivel) or transverse (hinge) movement of, e.g., each one of the arm segments  106 ,  108  about the corresponding axis and transmits a signal to an electronic data processing system within the AACMM  100  as described in more detail herein below. Each individual raw encoder count is sent separately to the electronic data processing system as a signal where it is further processed into measurement data. No position calculator separate from the AACMM  100  itself (e.g., a serial box) is required, as disclosed in commonly assigned U.S. Pat. No. 5,402,582 (&#39;582). 
         [0023]    The base  116  may include an attachment device or mounting device  120 . The mounting device  120  allows the AACMM  100  to be removably mounted to a desired location, such as an inspection table, a machining center, a wall or the floor for example. In one embodiment, the base  116  includes a handle portion  122  that provides a convenient location for the operator to hold the base  116  as the AACMM  100  is being moved. In one embodiment, the base  116  further includes a movable cover portion  124  that folds down to reveal a user interface, such as a display screen. 
         [0024]    As described further herein with respect to  FIGS. 4-6 , the base  116  and mounting device may further include a repeatable base mount  150  incorporated into the base  116  and having an electronic base mount identification system that associates an arm serial number and prior measurement history with the mount  150 . The exemplary base mount allows the AACMM  100  to be removed and properly replaced relatively more quickly without the need to establish all the baseline parameters of measurement each time the AACMM  100  is removed from the mount  150  and then subsequently replaced in the mount  150 . 
         [0025]    In accordance with an embodiment, the base  116  of the portable AACMM  100  contains or houses an electronic data processing system that includes two primary components: a base processing system that processes the data from the various encoder systems within the AACMM  100  as well as data representing other arm parameters to support three-dimensional (3-D) positional calculations; and a user interface processing system that includes an on-board operating system, a touch screen display, and resident application software that allows for relatively complete metrology functions to be implemented within the AACMM  100  without the need for connection to an external computer. 
         [0026]    The electronic data processing system in the base  116  may communicate with the encoder systems, sensors, and other peripheral hardware located away from the base  116  (e.g., a LLP that can be mounted to the removable handle  126  on the AACMM  100 ). The electronics that support these peripheral hardware devices or features may be located in each of the bearing cartridge groupings  110 ,  112 ,  114  located within the portable AACMM  100 . 
         [0027]      FIG. 2  is a block diagram of electronics utilized in an AACMM  100  in accordance with an embodiment. The embodiment shown in  FIG. 2  includes an electronic data processing system  210  including a base processor board  204  for implementing the base processing system, a user interface board  202 , a base power board  206  for providing power, a Bluetooth module  232 , and a base tilt board  208 . The user interface board  202  includes a computer processor for executing application software to perform user interface, display, and other functions described herein. 
         [0028]    As shown in  FIG. 2 , the electronic data processing system  210  is in communication with the aforementioned plurality of encoder systems via one or more arm buses  218 . In the embodiment depicted in  FIG. 2 , each encoder system generates encoder data and includes: an encoder arm bus interface  214 , an encoder digital signal processor (DSP)  216 , an encoder read head interface  234 , and a temperature sensor  212 . Other devices, such as strain sensors, may be attached to the arm bus  218 . 
         [0029]    Also shown in  FIG. 2  are probe end electronics  230  that are in communication with the arm bus  218 . The probe end electronics  230  include a probe end DSP  228 , a temperature sensor  212 , a handle/LLP interface bus  240  that connects with the handle  126  or the LLP  242  via the quick-connect interface in an embodiment, and a probe interface  226 . The quick-connect interface allows access by the handle  126  to the data bus, control lines, and power bus used by the LLP  242  and other accessories. In an embodiment, the probe end electronics  230  are located in the measurement probe housing  102  on the AACMM  100 . In an embodiment, the handle  126  may be removed from the quick-connect interface and measurement may be performed by the laser line probe (LLP)  242  communicating with the probe end electronics  230  of the AACMM  100  via the handle/LLP interface bus  240 . In an embodiment, the electronic data processing system  210  is located in the base  116  of the AACMM  100 , the probe end electronics  230  are located in the measurement probe housing  102  of the AACMM  100 , and the encoder systems are located in the bearing cartridge groupings  110 ,  112 ,  114 . The probe interface  226  may connect with the probe end DSP  228  by any suitable communications protocol, including commercially-available products from Maxim Integrated Products, Inc. that embody the 1-Wire® communications protocol  236 . 
         [0030]      FIG. 3  is a block diagram describing detailed features of the electronic data processing system  210  of the AACMM  100  in accordance with an embodiment. In an embodiment, the electronic data processing system  210  is located in the base  116  of the AACMM  100  and includes the base processor board  204 , the user interface board  202 , a base power board  206 , a Bluetooth module  232 , and a base tilt module  208 . 
         [0031]    In an embodiment shown in  FIG. 3 , the base processor board  204  includes the various functional blocks illustrated therein. For example, a base processor function  302  is utilized to support the collection of measurement data from the AACMM  100  and receives raw arm data (e.g., encoder system data) via the arm bus  218  and a bus control module function  308 . The memory function  304  stores programs and static arm configuration data. The base processor board  204  also includes an external hardware option port function  310  for communicating with any external hardware devices or accessories such as an LLP  242 . A real time clock (RTC) and log  306 , a battery pack interface (IF)  316 , and a diagnostic port  318  are also included in the functionality in an embodiment of the base processor board  204  depicted in  FIG. 3 . 
         [0032]    The base processor board  302  also manages all the wired and wireless data communication with external (host computer) and internal (display processor  202 ) devices. The base processor board  204  has the capability of communicating with an Ethernet network via an Ethernet function  320  (e.g., using a clock synchronization standard such as Institute of Electrical and Electronics Engineers (IEEE) 1588), with a wireless local area network (WLAN) via a LAN function  322 , and with Bluetooth module  232  via a parallel to serial communications (PSC) function  314 . The base processor board  204  also includes a connection to a universal serial bus (USB) device  312 . 
         [0033]    The base processor board  204  transmits and collects raw measurement data (e.g., encoder system counts, temperature readings) for processing into measurement data without the need for any preprocessing, such as disclosed in the serial box of the aforementioned &#39;582 patent. The base processor  204  sends the processed data to the display processor  328  on the user interface board  202  via an RS485 interface (IF)  326 . In an embodiment, the base processor  204  also sends the raw measurement data to an external computer. 
         [0034]    Turning now to the user interface board  202  in  FIG. 3 , the angle and positional data received by the base processor is utilized by applications executing on the display processor  328  to provide an autonomous metrology system within the AACMM  100 . Applications may be executed on the display processor  328  to support functions such as, but not limited to: measurement of features, guidance and training graphics, remote diagnostics, temperature corrections, control of various operational features, connection to various networks, and display of measured objects. Along with the display processor  328  and a liquid crystal display (LCD)  338  (e.g., a touch screen LCD) user interface, the user interface board  202  includes several interface options including a secure digital (SD) card interface  330 , a memory  332 , a USB Host interface  334 , a diagnostic port  336 , a camera port  340 , an audio/video interface  342 , a dial-up/cell modem  344  and a global positioning system (GPS) port  346 . 
         [0035]    The electronic data processing system  210  shown in  FIG. 3  also includes a base power board  206  with an environmental recorder  362  for recording environmental data. The base power board  206  also provides power to the electronic data processing system  210  using an AC/DC converter  358  and a battery charger control  360 . The base power board  206  communicates with the base processor board  204  using inter-integrated circuit (I2C) serial single ended bus  354  as well as via a DMA serial peripheral interface (DSPI)  356 . The base power board  206  is connected to a tilt sensor and radio frequency identification (RFID) module  208  via an input/output (I/O) expansion function  364  implemented in the base power board  206 . 
         [0036]    Though shown as separate components, in other embodiments all or a subset of the components may be physically located in different locations and/or functions combined in different manners than that shown in  FIG. 3 . For example, in one embodiment, the base processor board  204  and the user interface board  202  are combined into one physical board. 
         [0037]    Referring to  FIGS. 4-6 , another aspect of the improvements to the portable AACMM  100  of embodiments of the present invention relates to a repeatable base mount  150  having an electronic base mount identification system that associates a mount serial number with the and prior measurement history of one or more articulated arm CMMs. The repeatable base mount  150  includes a lower mount portion  402  and an upper mount portion  404 . The repeatable base mount  150  can be integral with the base  116 , and the mounting device  120  can be used to hold upper mount portion  404  in contact with lower mount portion  402 . This may be done by screwing the mounting device  120  downward against the threads of lower mounting portion  402  using a method similar to that illustrated in FIG. 9 of U.S. patent application Ser. No. 13/006,490, filed 14 Jan. 2011, which is hereby incorporated in its entirety by reference. 
         [0038]    In certain work scenarios, the operator of the portable AACMM  100  must routinely remove virtually the entire portable AACMM  100  (i.e., the base and arm portions) from a tool, machine, fixture, instrument stand, surface plate, or other work surface to which it was affixed during a machining or assembly operation. The operator must then re-install the portable AACMM  100  to take subsequent measurements. In current portable CMM systems, each time the portable AACMM  100  is re-installed, a relatively long time is required to properly re-establish a coordinate system and re-initiate the measurement session. For example, to establish a frame of reference, the AACMM is used to measure positions on the workpiece or the surroundings in at least three, but usually more, points. If the AACMM is moved to multiple locations, common points are measured by the AACMM in each of the locations to establish a common frame of reference. The user accesses application software to convert the coordinates of the measured points into mathematical transformation matrices that are needed when moving the AACMM from one mounting location to another. Such matrices might be 4×4 matrices that combine the actions of rotation and translation, for example. Methods for obtaining and using transformation matrices are well known to those of ordinary skill in the art and will not be discussed further. Using the transformation matrices, software can be used to find the pose (x, y, z, and three orientation angles) of the AACMM  100  at the new mount position. In general, the time it takes to perform the above-described steps greatly exceeds measurement times. As such, the exemplary embodiments described herein greatly improve efficiency in using the AACMM  100 . 
         [0039]    The present invention provides a repeatable base mount  150  that allows the AACMM  100  to be removed and repeatably replaced without the need to re-establish the pose of the AACMM  100  whenever the AACMM is moved. 
         [0040]    Some embodiments of the current invention use kinematic mounting elements, which may include combinations of balls and rods, for example. Other embodiments of the present invention are based on the principle of elastic averaging (overconstraint) to resist deformation from large forces. Such an embodiment includes a repeatable base mount  150  that can accommodate the relatively extreme forces required to secure the base  116  and arm portion  104  of the AACMM  100  to a mounting ring  400 , without deformation. For example, a static force can be an order of magnitude of a weight of the AACMM  100 . The torque on the mount of the AACMM  100  can be an order of magnitude of maximum spring forces times a length of the arm segments  106 ,  108 . An embodiment of the repeatable base mount  150  makes use of the principle of elastic averaging (overconstraint). Examples of elastic-averaging mounts  400  shown in  FIGS. 4A and 4B  include curvic ring couplings  410  ( FIGS. 4A ,  6 A,  6 B) and Hirth ring couplings  420  ( FIG. 4B ), which is also known as V-tooth or Voith couplings. The curvic ring couplings provide a relatively large support surface area and also constrain motion vertically, radially, and concentrically. Implementation of the curvic ring couplings  410  and the Hirth ring couplings  420  overcome the problems of the relatively extreme forces as described herein. As known in the art, curvic ring couplings  410  have precision face splines with curved radial teeth of contact depth. Curvic ring couplings  410  are implemented for joining two or more members to form a single operating unit. Also as known in the art, Hirth ring couplings  420  include radial grooves milled or ground into an end face of a cylindrical feature of a part. Grooves are made one by one into the part tilted by a bottom angle of the grooves, and rotated from groove to groove until serration is complete. Hirth ring couplings  420  are implemented to connect two pieces of a part together and are characterized by teeth that mesh together on end faces of each part half. 
         [0041]    In addition to the features that enable the repeatability of the couplings  400 , the base mounting system  150  also includes a key or pin to ensure a single mounting orientation. Each coupling  400  has a lower mount portion  402  and an upper mount portion  404 . The lower mount portion  402  is incorporated into a mounting ring, which can be attached using conventional means to a tool, machine, fixture, instrument stand, surface plate, or other work surface. The mounting ring may, for example, be integrated into mounting device  420 . The lower mount portion  402  may be assigned a unique serial number that can be transmitted to the AACMM  100  when installed on the mounting ring. This communication can be achieved wirelessly, magnetically, or via electrical connectors. In an embodiment, an encapsulated RF identification (RFID) tag  440  may be installed in the center of the mount assembly. In an embodiment, the serial number of the RF identification tag  440  is read by a transceiver  430 . 
         [0042]    An alternative design that provides a relatively more rigid coupling is a center drawn (e.g., bolt) attachment instead of a threaded ring (such as the threaded ring shown in lower mount portion  402  of  FIG. 6A ). Such a design may involve moving the RFID tag off the center of the lower mount portion  402  and the transceiver  430  off the center of the base  116 . In their places, a bolt is threaded between the lower mount portion  402  and the base  116  to hold the lower mount portion  402  and upper mount portion  404  securely together. Compared to a threaded design, this alternative design may provide a relatively more uniform edge loading of the ring, thereby providing a relatively more rigid mount. 
         [0043]    The upper mount portion  404  is attached to the base  116  of the AACMM  100 . The base  116  includes a means to read the serial number of the mount. In an embodiment, an RF transceiver  430  may be mounted inside the base  116  of the AACMM  100 , and an RF transparent window permits RF energy to pass from the base  116  to the RFID tag  440 . Shielding may be provided around the transceiver  430  and RFID tag  440  to minimize RF radiation emission from the transceiver  430  and susceptibility to RF radiation by the transceiver  430 . 
         [0044]    In embodiments of the present invention, the AACMM  100  contains hardware and software to allow storage of the pose (x, y, z, and three orientation angles) of the AACMM  100  within the global frame of reference for each position of a lower mounting portion  402 . Consequently, installation of the AACMM  100  on the mount is relatively fast. That is, the previous set-up information (i.e., pose) for that AACMM  100  is not lost and may be reused to quickly re-establish the baseline coordinate system for that particular AACMM  100 . Multiple mount and AACMM  100  combinations can be created and stored. Multiple lower mount portions  402  can be secured within a work area and an AACMM  100  moved from one lower mount portion  402  to another. Multiple AACMMs  100  and multiple lower mount portions  402  may store unique set-up information allowing for relatively fast, flexible equipment changes. 
         [0045]      FIG. 7  illustrates a flow chart of a method  700  for mounting the AACMM  100  in accordance with exemplary embodiments. At step  705 , the transceiver  430  of the AACMM  100  reads the serial number of the RFID tag  440  attached to the lower mount portion  402 . At step  710 , the electronic data processing system  210  determines whether the pose of the AACMM  100  is known for the serial number read in step  705 . If the serial number is known, then in step  715  the electronic data processing system  210  reads from memory  304  the six numbers (three positions and three angles) associated with the pose of the AACMM  100 . If the serial number is not known, then in step  720  the operator uses the AACMM  100  to measure a collection of points that are used by software to establish the pose of the AACMM  100  within a desired (e.g., global) frame of reference. Generally at least three points need to be measured. The points may be referenced to features from a CAD model or to features on a workpiece. In some cases, the same points may be measured by other AACMMs to place the AACMMs in a common frame of reference. In step  725 , the electronic data processing system  210  stores in the memory  304  the pose of the AACMM  100  and the serial number from the RFID tag  440  of the lower mount portion  402 . 
         [0046]    The method described with reference to  FIG. 7  assumes that the lower mount portion  402  has not been moved since the pose of the AACMM  100  was last determined. The possibility that the lower mount portion  402  has been moved can be accounted for in the application software, if desired. 
         [0047]    In embodiments hereinabove, an electronic identification system, which may include an RF identification tag and a transceiver, for example, is used to automatically send information to the electronic data processing system  210  to identify the particular lower mount portion  402 . For example, the lower mount portion  402  may be identified by a serial number. In another embodiment, the operator may take an action to identify the lower base portion  402 . For example, the application software may provide a user interface that enables the operator to identify the lower mount portion  402  whenever AACMM  100  is moved. By this means the operator can identify a particular lower mount portion  402  even if an electronic identification system is not available. In this case, the AACMM  100  can be moved among lower base portions  402  and quickly identified by the user in software. The software will then have access to the required transformation matrices, thereby eliminating the time-consuming measurement steps that would otherwise be required. 
         [0048]    Technical effects and benefits include the ability to store and recall the pose for an AACMM  100  when placed on a lower mount portion  402 , thereby saving setup time when moving an AACMM from place to place. 
         [0049]    As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method, or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon. 
         [0050]    Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that may contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. 
         [0051]    A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. 
         [0052]    Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. 
         [0053]    Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++, C# or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). 
         [0054]    Aspects of the present invention are described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, may be implemented by computer program instructions. 
         [0055]    These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer program instructions may also be stored in a computer readable medium that may direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks. 
         [0056]    The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
         [0057]    The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, may be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions. 
         [0058]    While the invention has been described with reference to example embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.