Abstract:
An apparatus for supporting a device, comprising a base assembly, a plurality of carrier columns extending from the base unit, and a plurality of vertical support plates, each vertically movable along a respective carrier column and including a pivotal device mounting bracket. A pneumatic unit including a piston rod is associated with each vertical support plate such that vertical motion of the piston rod controls vertical motion of the respective vertical support plate.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to systems for positioning and manipulating loads, and more particularly, to systems for positioning and manipulating test heads. 
       BACKGROUND OF THE INVENTION 
       [0002]    In the manufacture of integrated circuits (ICs) and other electronic devices, testing with automatic test equipment (ATE) is performed at one or more stages of the overall process. Special handling apparatus is used which places the device to be tested into position for testing. In some cases, the special handling apparatus may also bring the device to be tested to the proper temperature and/or maintain it at the proper temperature as it is being tested. The special handling apparatus is of various types including “probers” for testing unpackaged devices on a wafer and “device handlers” or “package handlers” for testing packaged parts; herein, “handling apparatus,” “test peripheral,” or simply “peripheral” will be used to refer to all types of such peripheral apparatus. The electronic testing itself is provided by a large and expensive ATE system which includes a test head which is required to connect to and dock with the handling apparatus. The Device Under Test (“DUT” or “dut”) requires precision, high-speed signals for effective testing; accordingly, the “test electronics” within the ATE, which are used to test the DUT, are typically located in the test head, which must be positioned as close as possible to the DUT. The test head is extremely heavy, and as DUTs become increasingly complex with increasing numbers of electrical connections, the size and weight of test heads have grown from a few hundred pounds to presently as much as two or three thousand pounds. The test head is typically connected to the ATE&#39;s stationary mainframe by means of a cable, which provides conductive paths for signals, grounds, and electrical power. In addition, the test head may require coolant to be supplied to it by way of flexible tubing, which is often bundled within the cable. 
         [0003]    In testing complex devices, hundreds or thousands of electrical connections have to be established between the test head and the DUT. These connections are accomplished with delicate, densely spaced contacts. In testing unpackaged devices on a wafer, the actual connection to the DUT is typically achieved with needle-like probes mounted on a probe card. In testing packaged devices, it is typical to use a test socket mounted on a “DUT board.” In either case, the probe card or DUT board is usually fixed appropriately to the handling apparatus, which brings each of a number of DUTs in turn into position for testing. In either case the probe card or DUT board also provides connection points with which the test head can make corresponding electrical connections. The test head is typically equipped with an interface unit that includes contact elements to achieve the connections with the probe card or DUT board. Typically, the contact elements are spring loaded “pogo pins.” Overall, the contacts are very fragile and delicate, and they must be protected from damage. 
         [0004]    Test head manipulators may be used to maneuver the test head with respect to the handling apparatus. Such maneuvering may be over relatively substantial distances on the order of one meter or more. The goal is to be able to quickly change from one handling apparatus to another or to move the test head away from the present handling apparatus for service and/or for changing interface components. When the test head is held in a position with respect to the handling apparatus such that all of the connections between the test head and probe card or DUT board have been achieved, the test head is said to be “docked” to the handling apparatus. In order for successful docking to occur, the test head must be precisely positioned in six degrees of freedom with respect to a Cartesian coordinate system. Most often, a test head manipulator is used to maneuver the test head into a first position of coarse alignment within approximately a few centimeters of the docked position, and a “docking apparatus” is then used to achieve the final precise positioning. Typically, a portion of the docking apparatus is disposed on the test head and the rest of it is disposed on the handling apparatus. Because one test head may serve a number of handling apparatuses, it is usually preferred to put the more expensive portions of the docking apparatus on the test head. The docking apparatus may include an actuator mechanism which draws the two segments of the dock together, thus docking the test head; this is referred to as “actuator driven” docking. The docking apparatus, or “dock” has numerous important functions, including: (1) alignment of the test head with the handling apparatus, (2) pulling together, and later separating, the test head and the handling apparatus, (3) providing pre-alignment protection for electrical contacts, and (4) latching or holding the test head and the handling apparatus together. 
         [0005]    According to the in TEST Handbook (5 th  Edition© 1996, in TEST Corporation), “Test head positioning” refers to the easy movement of a test head to a handling apparatus combined with the precise alignment to the handling apparatus required for successful docking and undocking. A test head manipulator may also be referred to as a test head positioner. A test head manipulator combined with an appropriate docking means performs test head positioning. This technology is described, for example, in the aforementioned in TEST Handbook. This technology is also described, for example, in U.S. Pat. Nos. 5,608,334, 5,450,766, 5,030,869, 4,893,074, 4,715,574, and 4,589,815, which are all incorporated by reference for their teachings in the field of test head positioning systems. The foregoing patents relate primarily to actuator driven docking. Test head positioning systems are also known where a single apparatus provides both relatively large distance maneuvering of the test head and final precise docking. For example, U.S. Pat. No. 6,057,695, Holt et al., and U.S. Pat. Nos. 5,900,737 and 5,600,258, Graham et al., which are all incorporated by reference, describe a positioning system where docking is “manipulator driven” rather than actuator driven. However, actuator driven systems are the most widely used, and the present invention is directed towards them. 
         [0006]    In the typical actuator driven positioning system, an operator controls the movement of the manipulator to maneuver the test head from one location to another. This may be accomplished manually by the operator exerting force directly on the test head in systems where the test head is fully balanced in its motion axes, or it may be accomplished through the use of actuators directly controlled by the operator. In several contemporary systems, the test head is maneuvered by a combination of direct manual force in some axes and by actuators in other axes. 
         [0007]    In order to dock the test head with the handling apparatus, the operator must first maneuver the test head to a “ready to dock” position, which is close to and in approximate alignment with its final docked position. The test head is further maneuvered until it is in a “ready to actuate” position where the docking actuator can take over control of the test head&#39;s motion. The actuator can then draw the test head into its final, fully docked position. In doing so, various alignment features provide final alignment of the test head. A dock may use two or more sets of alignment features of different types to provide different stages of alignment, from initial to final. It is generally preferred that the test head be aligned in five degrees of freedom before the fragile electrical contacts make mechanical contact. The test head may then be urged along a straight line, which corresponds to the sixth degree of freedom, that is normal to the plane of the interface (typically the plane of the probe card or DUT board); and the contacts will make connection without any sideways scrubbing or forces which can be damaging to them. 
         [0008]    As the docking actuator is operating, the test head is typically free to move compliantly in several if not all of its axes to allow final alignment and positioning. For manipulator axes which are appropriately balanced and not actuator driven, this is generally not a problem. However, actuator driven axes generally require that compliance mechanisms be built into them. Some typical examples are described in U.S. Pat. Nos. 5,931,048 to Slocum et al and 5,949,002 to Alden. Often compliance mechanisms, particularly for non-horizontal unbalanced axes, involve spring-like mechanisms, which in addition to compliance add a certain amount of resilience or “bounce back.” Further, the cable connecting the test head with the ATE mainframe is also resilient. As the operator is attempting to maneuver the test head into approximate alignment and into a position where it can be captured by the docking mechanism, he or she must overcome the resilience of the system, which can often be difficult in the case of very large and heavy test heads. Also, if the operator releases the force applied to the test head before the docking mechanism is appropriately engaged, the resilience of the compliance mechanisms may cause the test head to move away from the dock. This is sometimes referred to as a bounce back effect. 
         [0009]    An exemplary positioner system utilizing motor driven, six degrees of freedom adjustment is illustrated in U.S. Pat. No. 7,235,964, which is incorporated herein by reference. 
       SUMMARY OF THE INVENTION 
       [0010]    In one aspect, the present invention provides an apparatus for supporting a device, comprising a base assembly, a plurality of carrier columns extending from the base unit, and a plurality of vertical support plates, each vertically moveable along a respective carrier column and including a pivotal device mounting bracket. A pneumatic unit including a piston rod is associated with each vertical support plate such that vertical motion of the piston rod controls vertical motion of the respective vertical support plate. 
         [0011]    In another aspect, the present invention provides an apparatus for supporting a device, comprising a base assembly, a support assembly configured to support the device, and a plurality of compliant motion units positioned between the base assembly and the support assembly. Each compliant motion unit providing a range of motion in three horizontal degrees of freedom. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a left, rear perspective view of a positioner system according to an exemplary embodiment of the present invention with an exemplary test head positioned thereon in a lowermost position. 
           [0013]      FIG. 2  is a right, front perspective view of the positioner system of  FIG. 1  with the test head positioned thereon in a lowermost position. 
           [0014]      FIG. 3  is a right, front perspective view similar to  FIG. 2  with the test head in a raised position. 
           [0015]      FIG. 4  is a right, front perspective view similar to  FIG. 3  with the test head in a raised position and rotated to a dut-vertical orientation. 
           [0016]      FIG. 5  is a right, rear perspective view of the positioner system of  FIG. 1  with the test head removed. 
           [0017]      FIG. 6  is a right, front perspective view of the positioner system of  FIG. 1  with the test head removed. 
           [0018]      FIG. 7  is a partially exploded right, rear perspective view of the positioner system shown in  FIG. 1 . 
           [0019]      FIG. 8  is a partially exploded left, rear perspective view of the positioner system shown in  FIG. 1 . 
           [0020]      FIG. 9  is top right, rear perspective view of the base assembly of the positioner system shown in  FIG. 1 . 
           [0021]      FIG. 10  is a partially exploded top right, rear perspective view of the base assembly of  FIG. 9 . 
           [0022]      FIG. 11  is a partially exploded bottom right, rear perspective view of the base assembly of  FIG. 9 . 
           [0023]      FIG. 12  is an exploded perspective view of a compliant mounting unit of the base assembly of  FIG. 9 . 
           [0024]      FIG. 13  is a top plan view of the compliant mounting unit of  FIG. 12 . 
           [0025]      FIG. 14  is a cross-sectional view along the line  14 - 14  in  FIG. 13 . 
           [0026]      FIG. 15  is a perspective view of a compliant mounting unit with a pneumatic centering unit in a compliance position. 
           [0027]      FIG. 16  is a perspective view of the compliant mounting unit with the pneumatic centering unit in a locked position. 
           [0028]      FIG. 17  is a top plan view of the compliant mounting unit with the pneumatic centering unit in the compliance position. 
           [0029]      FIG. 18  is a top plan view of the compliant mounting unit with the pneumatic centering unit in the locked position. 
           [0030]      FIG. 19  is a perspective view of a compliant mounting unit with a mechanical centering unit in a compliance position. 
           [0031]      FIG. 20  is a perspective view of the compliant mounting unit with the mechanical centering unit in a locked position. 
           [0032]      FIG. 21  is a perspective view of the support assembly of the positioner system of  FIG. 1 . 
           [0033]      FIG. 22  is a perspective view illustrating the rail side of a first vertical support of the support assembly. 
           [0034]      FIG. 23  is an enlarged perspective view of a portion of the first vertical support of  FIG. 22 . 
           [0035]      FIG. 24  is a perspective view illustrating the bracket side of the first vertical support. 
           [0036]      FIG. 25  is an enlarged perspective view of a portion of the first vertical support of  FIG. 24 . 
           [0037]      FIG. 26  is a perspective view illustrating the bracket side of a second vertical support of the support assembly. 
           [0038]      FIG. 27  is top plan view of the positioner system of  FIG. 1 . 
           [0039]      FIG. 28  is an exploded perspective view of a portion of an exemplary pneumatic unit. 
           [0040]      FIG. 29  is an assembled perspective view of the pneumatic unit of  FIG. 28 . 
           [0041]      FIG. 30  is a cross-sectional view of the pneumatic unit taken along the lines  30 - 30  shown in  FIG. 29 . 
           [0042]      FIG. 31  is a schematic diagram of a portion of an exemplary pneumatic system for controlling movement of the positioner system. 
           [0043]      FIG. 32  is a schematic diagram of a portion of another exemplary pneumatic system for controlling movement of the positioner system. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0044]    Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention. 
         [0045]    When used herein, the following words and phrases have the meaning provided. Rear shall indicate the side of the positioner system  10  including the operator handle and front shall indicate the opposite side there from. Left and right shall indicate the directions when looking at the positioner system  10  from the rear. Up, upper, upward, above, down, lower, downward, below, underlying, and the like indicate the directions relative to the positioner system  10  as shown in  FIG. 1 . These words and phrases are utilized herein only for a clearer understanding of the drawings and are not intended to limit the orientation or positioning of components of the present invention unless specifically indicated. 
         [0046]      FIGS. 1-4  are perspective views of a positioner system  10  according to an exemplary embodiment of the present invention holding a test head  20  in various positions and orientations.  FIGS. 1-3  show the test head  20  in a dut-up orientation while  FIG. 4  shows the test head  20  in a dut-vertical orientation. The positioner system  10  in accordance with an exemplary embodiment of the invention facilitates positioning of the test head  20  with dock-from-below package handlers, horizontal-plane package handlers or vertical-plane handlers. The invention is however not limited to use with such handlers and may be utilized in other applications. 
         [0047]    A positioner system  10  is used for holding and moving a heavy load such as a test head  20  which is more fully described in U.S. Pat. No. 4,527,942, which is incorporated by reference. As shown in  FIG. 6  of that patent, six degrees of motion freedom are defined. The positioner system  10  in accordance with an exemplary embodiment of the present invention accomplishes these six degrees of motion freedom. 
         [0048]      FIGS. 5 and 6  are perspective views of the positioner system  10  shown in  FIG. 1  with the test head  20  removed, and  FIGS. 7 and 8  are exploded perspective views of the positioner system  10  shown in  FIG. 1 . As shown, the positioner system  10  generally comprises a base assembly  50  and a support assembly  100 . The base assembly  50  is configured to roll upon the floor and provides three degrees of motion freedom in the horizontal plane, namely, in-out motion; side-to-side motion; and rotation about a vertical axis. The support assembly  100  provides compliant motion in the remaining three degrees of freedom, namely, up-down motion; roll; and tumble or pitch. The exemplary positioner system  10  also includes a control panel  200  as will be described hereinafter. 
         [0049]    An exemplary base assembly  50  will be described with reference to  FIGS. 9-11 . Referring to  FIG. 9 , the exemplary base assembly  50  has a generally u-shaped configuration defined by a rear rail  52  extending between a pair of side rails  51  and  53 , with the side opposite the rear rail  52  defining an open side  54 . The open side  54  helps to facilitate mounting of the test head  20  to the positioning system  10 , as described hereinafter. The rails  51 - 53  define four corners  55 - 58 , namely, rear corners  55  and  56 , and front corners  57  and  58  at the front ends of the side rails  51  and  53 , respectively. A respective caster  60 ,  62 ,  64 ,  66  is attached to the base assembly  50  at each corner  55 - 58 . The front casters  64  and  66  are preferably fixed direction casters and the rear casters  60  and  62  are preferably swivel casters. The casters  60 ,  62 ,  64 ,  66  enable an operator to push the positioner system  10  around and position it with respect to the test peripheral. The rear casters  60 ,  62  have foot actuated locks  61 ,  63  to allow the operator to lock the base assembly  50  in a desired position with respect to the test peripheral. Any combination of rigid and swivel casters may alternatively be used as may best fit a specific application. Additionally, swivel casters that include the option to allow the operator to lock out the swivel motion while retaining linear motion may also be used. Such casters are commercially available and well known. The locking-out swivel feature may be useful, for example, in vertical plane docking when the manipulator has been correctly positioned and aligned in five degrees of freedom and straight-line motion of the casters is required for final docking. 
         [0050]    Movement and locking of the base assembly  50  relative to the test peripheral provides macro-compliant motion in the three horizontal plane degrees of freedom, namely, in-out motion; side-to-side motion; and rotation about a vertical axis. The exemplary base assembly  50  is further configured to provide micro-compliant motion in the three horizontal plane degrees of freedom. To facilitate such, a compliance mounting unit  70  is provided at each corner  55 - 58 . Each of the compliance mounting units  70  may have the same construction. Referring to  FIGS. 1 and 2 , the load support plates  102  of the support assembly  100  are attached to and supported by the compliant mounting units  70 , thereby providing such micro-compliant motion to the support assembly  100 . 
         [0051]    An exemplary compliant mounting unit  70  is illustrated in  FIGS. 12-14 . The compliant mounting unit  70  includes a housing  76  positioned about a ball  71  supported in a ball holder  72 . The ball  71  is generally freely rotatable relative to the ball holder  72 . A support disk  73  is positioned between the housing  76  and the ball  71  and is supported by the ball  71 . Because the ball  71  is freely rotatable, the support disk  73  supported thereon is horizontally freely moveable within the constraints defined by the housing  76 . A load support post  74  extends from the support disk  73  through a range of motion aperture  77  defined through the housing  76 . The support post  74  has an outside diameter less than the inside diameter of the range of motion aperture  77  such that the support post  74  has limited motion relative to the housing  76 . Contact of the support post  74  with the edges of the range of motion aperture  77  defines the range of motion of the support disk  73  and support post  74 . The illustrated range of motion aperture  77  has a rounded square configuration, but may have other configurations. Each support post  74  has a tapped hole  75  configured to receive a socket head cap screw  69  (see  FIGS. 1 ,  2  and  10 ) to secure a portion of a respective support assembly load support plate  102  relative thereto. 
         [0052]    Referring again to  FIGS. 9-11 , each compliant mounting unit  70  is secured to a respective corner  55 - 58  of the base assembly  50 . The side rails  51 ,  53  preferably have corresponding apertures  59  configured to receive the bottom portion of a respective ball holder  72 . The housing  76  may include screw holes  78  for securing of the compliant mounting unit  70  to a respective rail  51 ,  53 . The compliant mounting units  70  positioned on the base assembly  70  allow the test head  20  support assembly  100  to freely move over a limited range of motion in the three degrees of freedom in the horizontal plane, thus, providing the desired micro-compliant motion necessary for docking. 
         [0053]    At times it may be desirable or necessary to center the test head  20  with respect to these horizontal degrees of freedom. As illustrated in  FIG. 9 , the base assembly  50  includes centering units  80  on two of the compliant mounting units  70 . The centering units  80  are illustrated on the compliant mounting units  70  positioned at the rear corners  55  and  56 , but may be otherwise positioned. Additionally, the invention is not limited to two centering units. 
         [0054]    An exemplary pneumatic centering unit  80  will be described with reference to  FIGS. 15-18 . The centering unit  80  includes a pair of opposed blades  81  and  82 . Preferably, the blades  81  and  82  have the same configuration and are simply oriented inverted to one another, but they may alternatively have differing configurations. In the present embodiment, each blade  81 ,  82  has a housing connection portion  83 , a actuator connection portion  85  and a curved centering portion  84  therebetween. Each housing connection portion  83  is pivotally connected to the housing  76  at a pivot point  86 . Each actuator connection portion  85  is pivotally connected to a respective actuator plate  91 ,  92  at a pivot point  88 . A scissor screw  89  passes through both housing connection portions  83  and is received in a slot  79  on the housing  76 . The scissor screw  89  is free to move along the slot  79  (compare  FIGS. 17 and 18 ) to guide a scissor motion between the opposed blades  81  and  82 . 
         [0055]    Referring to  FIGS. 15 and 17 , the centering unit  80  is shown in a compliance position wherein the support post  74  is free to move within the range of motion aperture  77 . The blades  81  and  82  are configured such that in this position, the curved centering portions  84  of the blades  81 ,  82  are outside of the perimeter of the range of motion aperture  77  and therefore do not interfere with the free motion of the support post  74 . 
         [0056]    Referring to  FIGS. 16 and 18 , the centering unit  80  is shown in a locked position wherein the support post  74  is centered relative to the range of motion aperture  77  and prevented from moving. The blades  81  and  82  are configured such that in this position, the curved centering portions  84  of the blades  81 ,  82  are brought together to define a confinement area  90  that is centered relative to the range of motion aperture  77 . As the blades  81  and  82  are moved from the compliance position to the locked position, one or both of the blades  81 ,  82  contact the support post  74  and move the support post  74  to the confinement area  90 , thereby centering the support post  74  within the range of motion aperture  77 . Preferably, the blades  81  and  82  are locked in this position such that the support post  74  remains secured in such position. 
         [0057]    In the present embodiment, a pneumatic cylinder  93  is utilized to move the blades  81  and  82  between the compliance position and the locked position. Referring to  FIGS. 15 and 17 , one of the actuator plates  92  is fixed to the pneumatic cylinder  93  and the other actuator plate  91  is fixed to the piston rod  94 . The pneumatic cylinder  93  is configured such that it is fluidly controlled to extend and retract the piston rod  94 . In the compliance position, the cylinder  93  is preferably deactivated such that the piston rod  94  is free to extend and the actuator plates  91  and  92  are spaced apart, thereby separating the blades  81  and  82 . When centering is desired, the pneumatic cylinder  93  is actuated to retract the piston rod  94 . As the piston rod  94  is retracted, the actuator plates  91  and  92  are drawn together, thereby causing the blades  81  and  82  to scissor about the pivot points  86 ,  88  and define the confinement area  90 . Once centered, the pneumatic cylinder  93  may stay actuated to keep the load centered within its compliant range. To return to compliant mode, which requires little force, the pneumatic cylinder  93  is deactivated. Preferably, each of the centering units  80  (see  FIG. 9 ) is actuated or deactivated simultaneously, although such is not required. A pneumatic control for the centering units  80  may be provided on the control panel  200 , as described in more detail hereinafter. 
         [0058]    Referring to  FIGS. 19 and 20 , an exemplary mechanical centering unit  80 ′ is illustrated. The mechanical centering unit  80 ′ is substantially the same as the pneumatic centering unit  80 , except that the pneumatic cylinder  93  and piston rod  94  are replaced with a mechanical clamp assembly. Like features are numbered alike in the various figures. The centering unit  80 ′ includes a clamp handle  95  that is pivotally connected  97  at one end to the actuator plate  92 . A clamp linkage  96  is pivotally connected  98  at one end to the actuator plate  91  and pivotally connected  99  at its opposite end to a mid portion of the clamp handle  95 . As shown in  FIG. 19 , as the clamp handle  95  is pivoted toward the actuator plate  91 , the actuator plates  91  and  92  are spaced apart, thereby separating the blades  81  and  82 . As shown in  FIG. 20 , as the clamp handle  95  is pivoted in the opposite direction, the actuator plates  91  and  92  are drawn together, thereby causing the blades  81  and  82  to scissor about the pivot points  86 ,  88  and define the confinement area  90 . The clamp linkage  96  is preferably configured such that the centering unit  80 ′ remains locked in the centering position upon movement of the clamp handle  95  to the position shown in  FIG. 20 . In all other aspects, the centering unit  80 ′ operates in the same manner as in the previous embodiment. 
         [0059]    An exemplary support assembly  100  will be described with reference to  FIGS. 21-30 . Referring to  FIG. 21 , the support assembly  100  generally comprises a pair of opposed load support plates  102  interconnected by a pair of cross braces  105 . As illustrated in  FIGS. 24 and 26 , each load support plate  102  may include a reinforcement bar  104  positioned there along. Additionally, each load support plate  102  includes a pair of connection holes  103  adjacent the opposed ends and configured to receive a socket head cap screw  69  to secure the load support plate  102  to a respective compliant mounting unit  70 . An upright  106  is mounted at the rear end of each load support plate  102  and an operator handle  107  extends between the uprights  106 . As illustrated, the control unit  200  may be mounted to one of the uprights  106 . An angle bar  108  may also be provided at the rear end of each load support plate  102 . The angle bars  108  provide protection for the compliance equipment and may also be configured to provide an area for the operator to apply foot pressure to move the positioner system  10 . 
         [0060]    A vertical support  110 ,  110 ′ extends up from each load support plate  102 . The vertical supports  110  and  110 ′ are alike except for the coupling brackets  120  and  140 , respectively. Like features are numbered alike in the various figures. Referring to  FIGS. 22-25 , vertical support  110  will be described. Vertical support  110  includes a pneumatic unit  26  with a fluidly controlled piston rod  28 . The pneumatic unit  26  and fluid control will be described in more detail hereinafter. Adjacent to the pneumatic unit  26  is a carrier column  112  which extends from the load support plate  102  and has an inwardly directed rail  114  extending there along. Referring to  FIGS. 22 and 23 , vertical mounting plate  116  includes a pair of linear bearings  115  and  117  which are configured to engage the rail  114  such that the vertical mounting plate  116  is vertically moveable along the rail  114 . A coupling member  118  is interconnected between the vertical mounting plate  116  and the piston rod  28  of pneumatic unit  26 . As such, fluidly controlled motion of the piston rod  28  will control vertical motion of the vertical mounting plate  116  to which the test head  20  is connected, as described hereinafter. These components described with respect to vertical support  110  are common to vertical support  110 ′ as shown in  FIGS. 21 and 26  and do not require further description. 
         [0061]    Referring to  FIGS. 22-25 , vertical support  110  includes a coupling bracket  120  configured for connection to a mounting bracket  22  on one side of the test head  20  (see  FIG. 7 ). Coupling bracket  120  is rotatably mounted to mounting plate  116  with an appropriate pivotal coupling  123  inserted into a suitably located bore in plate  116 . As described hereinafter, vertical support  110 ′ includes a second rotatable coupling bracket  140 ; the two brackets support test head  20  and enable it to rotate about a horizontal axis that is parallel to the X-axis in  FIG. 1 . Rotation about this axis is referred to as “tumble” motion and the axis may be called the “tumble axis.” Tumble motion is one of the six degrees of freedom. Typically, the system is configured so that the tumble axis passes through the center of gravity of test head  20  so that it may rotate freely. The coupling bracket  120  provides limited compliant tumble motion, tumble lock, and a change-over capability between dut-up and dut-vertical orientations. The coupling bracket  120  includes a linear portion  122  and a curved portion  124 . The linear portion  122  of the coupling bracket  120  is pivotally mounted to the vertical mounting plate  116  via a pivotal coupling  123 . A pair of mounting bores  125  are provided along the linear portion  122  of the coupling bracket  120  and are configured to facilitate interconnection between the test head  20  mounting bracket  22  and the coupling bracket  120 . 
         [0062]    The coupling bracket  120  includes a pair of compliance slots  126  and  127  which are offset by approximately 90° relative to one another. Compliance slot  126  is configured to provide tumble compliance when the test head  20  is positioned in a dut-up orientation and compliance slot  127  is configured to provide tumble compliance when the test head  20  is positioned in a dut-vertical orientation. The pivotal coupling  123  of coupling bracket  120  allows a test head  20  to be moved between these orientations without removing the test head  20  from the positioner system  10 . A first stop  131  extends from the vertical mounting plate  116  and provides a rotational stop for the coupling bracket  120  when such is in the dut-up orientation (as shown). A second stop  133  extends from the vertical mounting plate  116  and provides a rotational stop for the coupling bracket  120  when such is in the dut-vertical orientation. 
         [0063]    To provide tumble compliance, a commercially available cam-actuated, spring-loaded plunger unit including plunger handle  135  and plunger rod  130  is attached to vertical mounting plate  116  of vertical support  110 . This is used in conjunction with compliance slots  126  and  127 , which are included in coupling bracket  120 . Rod  130  is circular in cross section, and the width of slots  125  and  126  are slightly wider than the diameter of rod  130 . With handle  135  in a first position, plunger rod  130  is withdrawn from engagement in either of slots  126  and  127 , and test head  20  may be freely rotated between the dut-up and dut-vertical positions. When test head  20  is, for example, in the dut-up position, handle  135  may be rotated to a second position, which causes rod  130  to extend into slot  126 . Similarly, when test head  120  is in the dut-vertical position, handle  135  may be rotated to the second position, causing rod  130  to extend into slot  127 . With rod  130  extended into either of slots  126  and  127 , the slots  126 ,  127  may move with respect to rod  130 ; and test head  20  may be compliantly rotated an amount limited by the lengths of the respective slots  126 ,  127 . Slot  126  may be made having a length that differs from that of slot  127 , allowing different amounts of tumble compliance in the dut-up and dut-vertical positions, if it is so desired. Obviously, if it is desirable to have a compliant position at some other angle, it can be readily achieved by including a slot at an appropriate location. 
         [0064]    A tumble motion lock mechanism is also provided for use when it is desired to lock test head  20  in this degree of freedom. The mechanism comprises lock handle  235 , threaded lock rod  230 , plastic tip  231 , and lock bracket  240 . Lock bracket  240  is attached to the vertical mounting plate  116  of vertical support  110  with appropriate fasteners such as screws. Lock handle  235  is fixed to lock rod  230 . Lock rod  230  includes a threaded section along its length and is threaded through a tapped hole in bracket  240 . A plastic tip  231  is attached to the distal end of lock rod  230 . These components are arranged so that the axis of rod  230  is in the plane of coupling bracket  120 . Thus, rotation of handle  235  in a first direction (typically clockwise) will cause tip  231  to move in the direction of and ultimately engage the edge of curved portion  124  of coupling bracket  120 . With tip  231  pressing firmly against the edge of coupling bracket  120 , tumble motion of test head  20  is prevented; and this motion axis is accordingly locked. Rotation of handle  235  in the opposite (typically counterclockwise) direction will cause tip  231  to move away from the edge of coupling plate  120 , unlocking the tumble axis and allowing tumble motion. 
         [0065]    Referring to  FIG. 26 , the coupling bracket  140  of the vertical support  110 ′ is similarly rotatably mounted to mounting plate  116  with an appropriate bearing unit inserted into a suitably located bore in plate  116 . Coupling bracket  140  is not required to additionally provide the above functions, and therefore, is configured to provide simple pivotal support of one side of the test head  20 . As such, coupling bracket  140  is a linear plate pivotally connected to the respective vertical mounting plate  116  via pivotal coupling  143 . A pair of mounting bores  145  are provided along the coupling bracket  140  and are configured to facilitate interconnection between a second test head mounting bracket  24  on the opposite side thereof and the coupling bracket  140 . 
         [0066]    Comparing  FIGS. 7 and 8 , it is shown that the test head mounting brackets  22  and  24  are preferably oriented 90° relative to one another. 
         [0067]    In order to adapt the manipulator to different peripherals it may be necessary to locate test head  20  at different locations with respect to mounting plate  116 . For example, a peripheral requiring docking in the dut-vertical position may require the test head to be mounted in a higher location than a peripheral requiring docking in a dut-up orientation. Additional pivot coupling  123  mounting bores may be included in mounting plates  116  at the time of manufacture to facilitate changeover from one application to another in a reasonable time in the user&#39;s facility. For example, additional bores  223  are shown in plates  116  in  FIGS. 21 ,  22 ,  24  and  26 . 
         [0068]    Referring to  FIG. 27 , the vertical supports  110  and  110 ′ are preferably mounted on opposite sides of the centerline CL of the support assembly  100 , however, the pivot couplings  123  and  143  are along the centerline CL such that the load is balanced between the two vertical supports  110  and  110 ′. Additionally, it is preferable that the test head  20  is arranged so that its center-of-gravity (cg) is substantially midway between the two vertical uprights  106  such that the pressure in the two pneumatic units  26  will nominally be equal in supporting the test head  20  in a level orientation, and one regulator may be used to provide fluid to both cylinders. If the cg is badly off center (a rare occurrence), a system with two regulators may be used wherein each pneumatic unit  26  is independent of the other. If the cg is slightly off center, suitable weights may be added to test head  20  to provide balance. 
         [0069]    Referring to  FIGS. 28-30 , an exemplary pneumatic unit  26  will be described. Preferably, both pneumatic units are the same configuration. The pneumatic unit  26  includes a telescoping piston rod  28 . In the illustrated embodiment, the pneumatic unit  26  includes a brake lock  630  configured to lock the position of the telescoping piston rod  28  relative to the cylinder block of the pneumatic unit  26 . The brake lock  630  is further configured to provide a pneumatic signal to the pneumatic control unit  200  if the pneumatic cylinder is out of balance by more than a given amount. The pneumatic control unit  200  may be configured to prevent unlocking of the brake lock  630  when such signal is received. 
         [0070]    Referring to  FIGS. 28-30 , the brake lock  630  includes a brake control port  631 . The brake lock  630  has a default locked position such that the lock is applied when no pressure is received through port  631 . When the brake lock  630  is switched to an unlocked position, fluid will be provided to port  631  to release the brake lock  630  provided an unbalanced condition is not detected as described below. 
         [0071]    In the present embodiment, the brake lock  630  includes through passages  635  which facilitate positioning of the brake lock  630  on corresponding support rods  720 . The support rods  720  are each secured at a first end to the cylinder block of the pneumatic unit  26 . The brake lock  630  is axially moveable along the rods  720  between a bottom contact plate  700  and a top contact plate  710 . Springs  721  or the like are positioned between the bottom plate  700  and the brake lock  630  and springs  723  or the like are positioned between the top plate  710  and the brake lock  630 . The springs  721  and  723  support the brake lock  630  for a limited range of motion between the plates  700  and  710 . Nuts  726  or the like are secured to the opposite ends of the rods  720  to axially secure the plates  700 ,  710 , springs  721 , 723  and brake lock  630 . The amount of tightening of the nuts  726  may be utilized to control the range of motion of the brake lock  630  between the plates  700  and  710 , thereby control the tolerance or sensitivity of the unbalanced signal. 
         [0072]    As described with reference to  FIG. 31 , when the lock switch is moved to the locked position, pneumatic pressure is removed from the brake lock  630  and the lock is applied to the piston rod  28 , thereby fixing the lock relative to the piston rod  28 . In the present embodiment, the springs  721 ,  723  allow the brake lock  630  to move over a limited range of motion. As such, for example, if the brake lock  630  is locked and thereafter additional weight or external force is applied on the piston rod  28 , the piston rod  28 , and the brake lock  630  fixed thereto, will move against the force of springs  721 . If the weight or external force is sufficient, the brake lock  630  will move into contact with the bottom plate  700 . As described hereinafter, the system is configured to provide a pneumatic signal indicating an unbalanced condition when the brake lock  630  moves into contact with the bottom plate  700 . Similarly, if weight is removed from the piston rod  28 , the piston rod  28 , and the brake lock  630  fixed thereto, will move upward against the force of springs  723  due to the pressure in the pneumatic unit  26 . If the decrease is sufficient, the brake lock  630  will move into contact with the top plate  710 . Again, the system is configured to provide a pneumatic signal indicating an unbalanced condition when the brake lock  630  moves into contact with the top plate  710 . 
         [0073]    Referring to  FIG. 31 , an exemplary pneumatic system  600  which is part of the pneumatic control unit  200  and which is configured to control the linear motion of both of the telescoping piston rods  28  will be described. The pneumatic system  600  is configured to control the pressure and flow of fluid to each pneumatic unit  26  to control the up and down motion of the piston rods  28  as well as its static and compliant behavior. In the illustrated embodiment, a single throttle control assembly  660  controls both pneumatic units  26 . 
         [0074]    Each pneumatic unit  26  is a double acting cylinder which is vented to atmosphere at port  601  on one side of the piston  45  and connected to a pneumatic feed line  603  on the opposite side of the piston  45 . A spring biased check valve  602  is provided in feed line  603  and is configured to close upon loss of pilot pressure in the system to prevent falling of the piston rod  28 . A piloted, biased pressure regulator  604  is positioned along the feed line  603  and is configured to control the pressure (and consequently the rate of flow) of the fluid delivered to the pneumatic unit  26 . The pressure regulator  604  receives pressurized fluid from a pressure source  650  along pressure feed line  605 . A pressure regulator  648  is provided along the pressure feed line  605  to regulate the fluid pressure to a desired pressure. Pressure regulator  648  also includes a filter (unnumbered) to clean the air as it enters the system. 
         [0075]    A throttle assembly  660  is provided in the pneumatic system  600  to allow an operator to control upward and downward movement of the piston rod  28 . The throttle assembly  660  includes a cylinder  662  with a piston  664  moveable within the cylinder  662  via a handle or the like. One end of the cylinder  662  includes a port  667  open to atmosphere and the other end includes a port  663  that is connected to a pilot line  665  fluidly connected to the pilot control of the biased pressure regulator  604 . A variable volume chamber  668  is defined between the piston  664  and the port  663 , however, the mass of fluid, e.g. air, within the chamber  668  and pilot line  665  is fixed. 
         [0076]    The throttle assembly  660  is assembled such that when force is not applied to the handle  666 , the piston  664  is positioned such that the fluid pressure within the chamber  668  and pilot line  665  is neutral, i.e. a zero pilot pressure (relative to atmospheric pressure) is provided to the pilot control of the biased pressure regulator  604 . With no pilot pressure to the pilot control, biased pressure regulator  604  remains in the equalized position such that the piston rod  28  remains in the balanced or static state. 
         [0077]    To move the telescoping column  20  upward, the operator moves the handle  666 , and thereby the piston  664 , toward the port  663 , thereby reducing the volume of chamber  668 . Since the fluid mass is constant, the decrease in volume of the chamber  668  will cause the fluid pressure in the chamber  668  and pilot line  665  to increase. The increased pressure is applied directly through the pilot line  665  to the pilot control of pressure regulator  604 . As explained above, the set pressure of the biased pressure regulator  604  can be adjusted by adding or subtracting pilot pressure to the pilot control member. 
         [0078]    In the up scenario, the positive pressure to the pilot control of biased pressure regulator  604  causes the set pressure of regulator  604  to increase, thereby increasing the pressure within pneumatic units  26 , causing the piston rods  28  to rise. The amount of increase in the set pressure of regulator  604  correlates to the amount of additional positive pressure on the pilot control. Since movement of the handle  666  controls the volume of the chamber  668 , the amount of increase in pilot pressure, and the corresponding increase in set pressure of regulator  604 , is continuously variable over the range of movement of the piston  664  between the neutral position toward the port  663 . 
         [0079]    Upon release of the handle  666 , the piston  664  moves back to the neutral position to allow the pressure within the chamber  668  and pilot line  665  to return to the neutral pressure. 
         [0080]    To translate the piston rod  28  downward, the operator moves the handle  666  such that the piston  664  moves from the neutral position away from the port  663 , thereby increasing the volume of the chamber  668 . Since the fluid mass is constant, the increase in volume of the chamber  668  will cause the fluid pressure in the chamber  668  and pilot line  665  to decrease. The decreased pressure is applied directly through the pilot line  665  to the pilot control of pressure regulator  604  which causes the set pressure of regulator  604  to decrease, thereby decreasing the pressure within pneumatic unit  26 . As such, the weight of the piston rod  28  and the testing head  20  will be greater than the pressure in the pneumatic unit  26  and the piston rod  28  will be lowered. Again, release of the handle  666  will return the piston  664  to the neutral position, thereby discontinuing negative pilot pressure to the pilot control of the pressure regulator  604 . 
         [0081]    As with the up scenario, since movement of the handle  666  controls the volume of the chamber  668 , the amount of decrease in pilot pressure, and the corresponding decrease in set pressure of regulator  604 , is continuously variable over the range of movement of the piston  664  between the neutral position away from the port  663 . In both the up and down scenarios, the variable pressure range provides a tactile feedback at the handle  666 . The operator senses that the more force the operator applies to the handle  666 , the more the pressure will change (either increase or decrease) in response thereto. This change in pressure, felt in force by the operator upon the handle  666 , represents the force applied to the piston  45  via the biased pressure regulator  604  and throttle assembly  660 , thus providing tactile feedback. The operator can also control the acceleration, speed, and position of the test head  20  in this manner. The operator may observe the movement and/or the behavior of the test head  20  as he or she causes the set pressure of biased regulator  604  and thus the force on piston  45  to change via moving the handle  666  up or down. The operator may adjust the handle  666  as necessary to initiate motion of the test head  20  at a desired rate, maintain a desired speed, and stop motion at a desired rate and position. 
         [0082]    The exemplary pneumatic system  600  is also configured to provide a pneumatic signal of an unbalanced condition in either of the pneumatic units  26 . Pressurized fluid is also provided to lock/unlock toggle valve  632 . The toggle valve  632  is normally closed so that no pressure is applied to either brake lock  630 , locking the brake locks  630  to the piston rods  28 . To release the brake locks  630 , the toggle is switched to the open position. The fluid flowing through the opened toggle valve  632  flows to a detector valve  730 . The detector valve  730  is spring biased to an initial position wherein fluid travels toward a pair of sensor valves  732  and  734 , but not to the brake lock port  631 . The fluid also travels through a restrictor  634  toward an opening pilot  730   a  on the detector valve  730 . The restrictor  634  is configured to provide a sufficient delay before the opening pilot is energized to open the detector valve from its initial position. In the present embodiment, each pneumatic unit  26  is provided with a pair of sensor valves  732  and  734 . The output of the respective sensor valves  732  is coupled via a shuttle valve  741  and the output of the respective sensor valves  734  is coupled via a shuttle valve  742 . As such, the operation will be described with respect to a single set of sensor valves  732  and  734 . 
         [0083]    Sensor valve  732  is connected via line  733  to an inlet port  712  on top plate  710  which is fluidly connected to an open port  715  through compressible plug  714  extending from the bottom surface of top plate  710 , as shown in  FIGS. 28-30 . Similarly, sensor valve  734  is connected via line  735  to an inlet port  702  on bottom plate  700  which is fluidly connected to an open port  705  through compressible plug  704  extending from the top surface of bottom plate  710 . Each of the sensor valves  732 ,  734  has a normally closed position such that the fluid flowing thereto bypasses the valve  732 ,  734  and flows out the respective open port  715 ,  705 . Provided there is no back pressure, both sensor valves  732 ,  734  will remain in such closed condition. 
         [0084]    If an unbalanced condition exists as described above, the brake lock  630  will contact one of the plates  700 ,  710  and compress the respective plug  704 ,  714 , thereby closing the open port  705 ,  715 . Due to the closed port,  705 ,  715 , a back pressure will be received at the respective sensor valve  734 ,  732 . The back pressure energizes the respective sensor pilot and causes the sensor valve  734 ,  732  to open. Fluid travels through the sensor  732 ,  734  and actuates a respective pressure high or pressure low indicator  736 ,  738 . The flow continues through either line  737  or  739  and through a shuttle valve  740  to the maintain closed pilot  730   b  of detector valve  730 . The force of the maintain closed pilot  730   b  in combination with the original spring bias of the valve  730  will maintain the valve  730  in its initial position even upon fluid passing through the restrictor  634  and reaching the opening pilot  730   a . The detector valve  730  will remain in this initial position, and will not allow fluid to flow to the brake release port  631 , until the load is balanced, thereby uncompressing the plug  704  or  714  and removing the back pressure on the actuated sensor valve  732 ,  734 . 
         [0085]    The pressure high and pressure low indicators  736 ,  738  may be utilized in rebalancing the load. As explained above, if the load is unbalanced when the toggle valve  632  is moved to the unlock position, the brake lock  630  will not release and either the pressure high indicator  736  or the pressure low indicator  738  will be actuated. Upon actuation, the indicators  736 ,  738  provide a signal to an operator that the load is unbalanced, i.e. if the load has been reduced, the pressure high indicator  736  will provide a signal and if load has been increased, the pressure low indicator  738  will provide a signal. The signals may take various forms, for example, an audible signal, a visual signal, or a combination thereof. In an exemplary configuration, each indicator  736 ,  738  includes an extensible post (not shown) which is pneumatically extending upon actuation of the indicator  736  or  738 . 
         [0086]    The indicator signals alert the operator to the necessary pressure adjustment to rebalance the load. If the pressure high indicator  736  is actuated and providing a signal, the operator is alerted to decrease the set pressure of the biased pressure regulator  604 , for example, by reducing the force on the mechanical biasing member. If the pressure low indicator  738  is actuated and providing a signal, the operator is alerted to increase the set pressure of the biased pressure regulator  604 , for example, by increasing the force on the mechanical biasing member. In an exemplary configuration, the means for increasing or decreasing the force on the mechanical biasing member is through a rotatable dial. In this configuration, the indicators  736 ,  738  may be positioned relative to the rotatable dial such that the actuated indicator  736  or  738  will guide the operator of the proper direction to rotate the dial to rebalance the load. For example, if counterclockwise rotation of the dial decreases the set pressure and clockwise rotation of the dial increases the set pressure, the pressure high indicator  736  is positioned to the left of the dial and the pressure high indicator  738  is positioned to the right of the dial. As such, if the pressure high indicator  736  is actuated, the operator will know to turn toward the indicator  736 , thereby turning the dial in the counterclockwise direction, and conversely, if the pressure low indicator  738  is actuated, the operator will know to turn toward the indicator  738 , thereby turning the dial in the clockwise direction. The invention is not limited to this configuration of the adjustment mechanism or indicators. 
         [0087]    Once the load is rebalanced, or if the load was balanced to begin, both ports  715  and  705  will remain open and the corresponding sensor valves  732 ,  734  will remain closed. With the sensor valves  732 ,  734  closed, no fluid pressure flows to the maintain closed pilot  730   b  of the detector valve  730 . As such, the fluid which flows through the restrictor  634  will reach the opening pilot  730   a  and provide a force sufficient to overcome the original spring bias of the detector valve  730 , thereby causing the detector valve  730  to open to allow fluid to flow to the release port  631  of the brake lock  630 . In the present embodiment, fluid also flows to an opening pilot of a throttle release valve  750 . The throttle release valve  750  is positioned along the pilot line  665  and has a default closed position such that the throttle can not be used for up or down movement until the detector valve  730  is opened and the brake lock  630  released. 
         [0088]    Another exemplary pneumatic control system  600 ′ is illustrated in  FIG. 32 . This system is substantially the same as in the previous embodiment, but further includes a second toggle valve  800  configured to control the pneumatic cylinders  93  of the centering units  80 . As explained above, the pneumatic cylinders  93  are biased to an extended position of the piston rod  94 , such that the posts  74  are free to move. Upon actuation of the toggle valve  800 , fluid is supplied to the cylinders  93  to retract the rods  94 , thereby locking the centering units  80 . A check valve  802  is positioned along the line between the valve  800  and the cylinders  93  to trap air in these cylinders  93  in the case of system pressure loss or turning off the air to the system to allow the centering units  80  to still hold the base compliance modules in the locked position. 
         [0089]    The illustrated embodiments show various features which may be incorporated into the pneumatic control unit  200 . The invention is not limited to the illustrated features. Furthermore, while the system is described as a pneumatic system utilizing pressurized air, other fluids may be utilized. 
         [0090]    Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.