Abstract:
A lifting apparatus and controller therefore, where the lifting apparatus includes independently driven lifting columns and independently driven wheels that are controlled by a controller having a number of sensors such as limit sensors, position sensors, rotation sensors, laser sensors, torque sensors and the like. The independent motors for lifting and driving may also be removed easily to provide for improved servicing and maintenance. The various sensor signals are used to calculate, coordinate and calibrate the apparatus for precise and safe movement by the motors in order to perform lifting and positioning operations, for example rail car repair and service.

Description:
FIELD OF THE INVENTION 
       [0001]    The following invention relates to a lifting and positioning apparatus. More particularly, the following relates to lifting machinery and a controller for rail car and engine maintenance having independent drive and lifting motors. 
       BACKGROUND OF THE INVENTION 
       [0002]    In many factories and repair shops, lifting and positioning equipment is used to move heavy objects or to remove parts to expose the underside of the vehicle or to provide easier access for repair and/or replacement of parts and assemblies. This allows a worker to inspect, repair or assemble various items with greater ease than when attempting to work through gaps or crawl spaces. 
         [0003]    U.S. Pat. No. 7,603,734 to Connelly et al discloses a system for lifting a passenger boarding bridge for an aircraft that avoids rack fault. The system has two electromechanical screw jacks. Each motor receives a signal for adjusting the height of the tunnel selection and the system uses rotational sensors to monitor the position of the two screw jacks. Connelly does not appear to disclose a controller that monitors multiple sensors from each column to determine the position and load on the screw jacks to calculate a control signal for each of the columns. 
         [0004]    One difficulty encountered with some rotational sensors is that they can become out of phase by missing a rotation count. For example, the rotational sensor may count each rotation based on passing an optic or magnetic sensor. In many cases, some of the rotations may not be properly counted, which could lead to one column bearing a higher percentage of the overall load. Further, if the rotational sensor does not count rotations correctly, rack fault could occur. 
         [0005]    U.S. Pat. No. 6,923,599 to Kelso discloses an in-ground lifting system for raising a building foundation. Kelso appears to show columns placed below the foundation of a building. Kelso also appears to disclose the ability to monitor the position through sensors to minimize stresses on the foundation. It does not appear that a control program monitors multiple types of sensors from each column to determine the position and/or load in order to calculate a control signal. 
         [0006]    Further, some lifting apparatuses are designed to move on rails or wheels to allow a worn part to be removed from the rail car or engine and then taken away for repairs. In some cases, another lifting apparatus of a similar type would be placed so that a new or repaired part can be positioned and then attached to the rail car/engine. Thus providing a faster repair/replacement cycle that allows a stock of replacement parts to be maintained and for servicing to be completed on worn parts without requiring downtime of the rail car or engine being repaired. It is therefore desired to provide a lifting and positioning apparatus that overcomes the disadvantages of the prior art. 
         [0007]    Vehicles such as busses, cars and rail vehicles may not provide enough space between the ground and the underside of the vehicle for access to parts or assemblies that require inspection and repair. These vehicles are often rather heavy, and lifting the vehicle or positioning various parts of the vehicle requires precise balancing and positioning of the various items. Also, the machinery used to lift or position these items undergoes a great deal of wear, and thus the maintenance and proper function of the lifting equipment itself is critical for safety concerns. 
         [0008]    Various car hoist or drop table systems are known in the art. These systems have more than one lifting column connected to a single motor, where the rotation of the motor causes translation of a support on the column through a transmission system. The transmission system can be used to adjust the gearing to likewise adjust the speed of the support that moves along the column. For example,  FIGS. 8 and 9  show a positioning apparatus having a motor  1  that is connected to transmission columns  3 ,  5 ,  7 ,  9 . These transmission columns are connected to the motor via a drive shaft. As shown in  FIG. 8 , a track section  11  is connected to the transmission columns. The motor rotates the drive shaft to transmit a rotational force to each of the transmission columns  3 ,  5 ,  7 ,  9 . These transmission columns have a gearing system that adjusts the rotation of the screw  13 ,  15 ,  17 ,  19 . As discussed previously, the load on the columns is often rather high, which can result in increased wear. Failure of gears within the transmission column can result in serious safety issues if failure occurs after a heavy load has been lifted above the floor. 
         [0009]    Further, the replacement and maintenance of the transmission columns can be a skill and labor intensive process that may require specialized individuals who have been trained to repair a particular machine. The scheduling of the repair personnel can often result in a shutdown of a given machine in a way that can create bottlenecks in the repair shop or factory. As shown in  FIGS. 8 and 9 , the drop table system may be provided with a motor and a transmission system that is used to drive the wheels of the drop table to provide movement of the drop table to a different part of the factory or repair shop as necessary. As with the lifting column system using a single motor and transmissions, repair and replacement of worn parts can be a difficult task. Further, proper calibrations and maintenance of the gearing for moving the apparatus is an operation that may require specialized skill from maintenance personnel. 
         [0010]    In some cases, the positioning device is designed to lift the entire vehicle for inspection and repair of the underside of the vehicle. In some cases, the positioning device is designed to be placed under a specific part or assembly of the vehicle, where the part or assembly is dropped down from the vehicle. 
         [0011]    As an example, a rail car such as a locomotive can be rather heavy. It may be more efficient and safer to bring a wheel and axle assembly down from the engine rather than lifting the entire engine. In some cases, however, it is more appropriate to lift the entire rail car or locomotive. In other cases, the repair may only necessitate lifting a part or assembly of the rail car, for example a wheel assembly. The lifting apparatus used depends on the repair or assembly job to be completed. 
         [0012]    The precision of the lifting process is important to balance the load and to ensure correct positioning of the columns and correct positioning of the rail car, locomotive or part or assembly thereof. The present systems and methods provide a more user friendly lifting and positioning apparatus which can aid to provide a safer working environment and reduce repair and maintenance costs. 
         [0013]    As a further aid to safety and reliability, the position control can reduce un-necessary damage to the apparatus. Since of the mass of the item to be lifted may be relatively large, the columns can generate substantial torques and forces. If the position of the individual columns is not controlled properly, one or more of the columns could come out of alignment and bend the support structure that is connected to the columns. Thus, the failure to properly control the columns can result in damage to the structure of the lifting apparatus itself. 
         [0014]    It may be important that the lifting apparatus is properly aligned below the rail car or locomotive so that the lifting apparatus does not need to be moved when the load is in an elevated position, further, proper control and positioning of the drive motors and likewise monitoring thereof may allow for more predictable maintenance operations and likewise shorter repair cycles for the lifting apparatus. 
       SUMMARY OF THE INVENTION 
       [0015]    It is therefore an object of the present invention to provide a lifting and positioning apparatus that allows for more accurate and precise positioning and load balancing. It is still another object of the invention to provide a lifting and positioning apparatus that operates with increased safety and reliability. Yet another object of the invention is to provide a lifting and positioning apparatus that avoids damage to the support structure due to incorrect positioning. The damage avoided could be due to, for example, bending and warping as well as cyclical and plastic deformations and/or failures. 
         [0016]    It is yet another object of the present invention to provide a lifting and positioning apparatus which can allow for easier repair and replacement of critical wear intensive parts and assemblies. 
         [0017]    Because the columns may be interchangeable, the bottom flange may simply be un-bolted from the base, the second support and the first support of the column to be replaced could be dis-connected and the electrical connections dis-connected. This allows for one column to be removed with limited repair skill or specialized mechanical knowledge. In comparison to the prior art, this saves a great deal of time. The prior art systems included geared transmissions that were coupled to a motor, where adjustment of the gear ratio would change the speed of the lift. Since each column has its own motor and sensors in a self-contained package, it is much easier to replace columns and critical wear parts with minimal machinery downtime. 
         [0018]    Likewise, the drive motors can be interchangeable and easily removed and replaced so that maintenance of a multiple wheel transmission and drive system and likewise the time intensive replacement or repair thereof can be avoided. 
         [0019]    Therefore, the above mentioned and other objects are achieved by providing a positioning apparatus including a base. A plurality of columns each having a first support and a lift motor wherein rotation of the lift motor moves the first support along an axis of the column, said plurality of columns may be coupled to the base. Each first support may be coupled to a second support. A plurality of wheels may be coupled to the base. A drive motor may be coupled to the wheels. A controller in communication with the lift and drive motors may generate a control signal to drive at least one said lift or drive motors in order to change a position of at least a part of the positioning apparatus. 
         [0020]    In one aspect, each drive motor is connected to one of the wheels. The controller may be in communication with each drive motor. The control signal may be generated to drive the drive motor in order to move the base. In other aspects a first position sensor coupled the drive motor may generate a first position signal indicative of a position of the wheel coupled to the drive motor. The controller may generate the control signal based on the first position signal. 
         [0021]    In other aspects the wheels may roll on a first track and a second position sensor may be coupled to the base and in communication with the controller. A position indicator and the second position sensor may be used in connection with the first track and lifting apparatus so that when the second position sensor is activated by the position indicator, the control signal stops movement of the positioning apparatus along the first track. In other aspects, the rotation sensors may be calibrated based on activation of the second position sensor/position indicator. 
         [0022]    Other objects are achieved by providing a method of removing a part from a vehicle, the method including one or more steps of: providing a positioning apparatus having at least three columns, each column having a lift motor to move a first support along an axis of the column, the first supports connected to a second support having a track section, the positioning apparatus; providing a controller in communication with said drive and lift motors; receiving at least one sensor signal via the controller, at least one of the sensor signals indicative of a position of said base on a first track; and transmitting a drive control signal generated by the controller to the drive motors to vertically align the track section with a second track by moving the base along the first track. 
         [0023]    In one aspect, the method may include restricting via the controller, movement of said drive motors when said position condition indicates that the track section is in a position other than the first position. 
         [0024]    Other objects are achieved by providing a controller for a positioning apparatus, the controller may include a processor and an input module associated with the processor and receiving a control input indicative of horizontal movement for the positioning apparatus. A sensor module associated with the processor may receive a sensor signal indicative of a position of at least one wheel, each wheel connected to at least one of a plurality of drive motors. A position module associated with the processor may calculate a position of the positioning apparatus from the sensor signal. A control signal module associated with the processor may compare the position of the positioning apparatus to a position of a second track to generate a control signal based on the control input, the control signal for controlling movement of at least one of the plurality of drive motors. 
         [0025]    In one aspect, the controller transmits the control signal to at least one of the drive motors to control the position of the positioning apparatus so that a track section of the positioning apparatus is vertically aligned with the second track. In another aspect the sensor signal is received from a second position sensor, the second position sensor is disposed in a location such that when the second position sensor is activated, the track section is vertically aligned with the second track. In other aspects, the controller restricts movement of the positioning apparatus along the track based on the position/load of the lifting motors and lifting supports associated with the columns. For example, if a load is elevated, the controller may restrict horizontal movement of the positioning apparatus for safety purposes. 
         [0026]    The positioning apparatus may include at least one load sensor connected to each of the plurality of columns and at least one column position sensor connected to each of the first supports. The load sensor may be an electrical load sensor where the load signal is indicative of an electrical current of the motor. The apparatus may include four columns and also include at least one limit switch connected to at least one of the plurality of columns at a bottom or top end. Each limit switch indicates when one of the first supports is in a position associated with the limit switch so that movement, of the first support in the position associated with the limit switch, stops. 
         [0027]    The apparatus may further include a third limit switch coupled to at least one of the columns and disposed between the first and second limit switches, the third limit switch in communication with the controller, where the control input is indicative of a position associated with the third limit switch. The controller can calculate a control signal from the position signal, load signal and control input to move the first support to the position associated with the third limit switch. Movement of at least one of the first supports may stop when the third limit switch indicated the first support is in a position associated with the third limit switch. 
         [0028]    Each column of the apparatus may include first, second and third limit switches. The column position sensor may be a linear position sensor coupled to the first support member. The position signal may be indicative of a position of said first support member in relation to a fixed point. The apparatus may include first and second limit switch coupled to at least one of the plurality of columns. The first and second limit switches may be respectively positioned at top and bottom ends of the column. The motor may stop once one of the top or the bottom limit indicates a the first support is in a position corresponding to one of the top or bottom limit switches. 
         [0029]    The apparatus may include a control input received by the controller and indicative of a direction of movement for the second support. The controller may calculate a load distribution among the first supports to generate a calibration for the controller. The controller may maintain the load distribution during movement of the second support. The load distribution may also be maintained within a range of loads. The range may be predetermined, set by the operator or another user, calculated based on the amount of load on the second support or be within a percentage range. Other scenarios for the range as would be apparent to one of skill in the art are contemplated and these examples are not limiting. 
         [0030]    The term “rail car” as used herein includes but is not limited to locomotives, freight cars, box cars, rail cars, repair vehicles, push cars, and other vehicles that have wheels and can move on rails whether indoors or outdoors. This may include, for example, vehicles that can move on rails in a factory floor. The term “vehicle” includes but is not limited to “rail cars” as well as other powered and un-powered vehicles such as automobiles, cars, trucks, and military and construction vehicles such as tanks, excavators and construction equipment. 
         [0031]    Other objects of the invention and its particular features and advantages will become more apparent from consideration of the following drawings, claims and accompanying detailed description. It should be noted that, while various functions and methods have been described and presented in a sequence of steps, the sequence has been provided merely as an illustration of one advantageous embodiment, and that it is not necessary to perform these functions in the specific order illustrated. It is further contemplated that any of these steps may be moved and/or combined relative to any of the other steps. In addition, it is still further contemplated that it may be advantageous, depending upon the application, to utilize all or any portion of the functions or combinations of functions described herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]      FIG. 1A  is a perspective view showing the base of the lifting and positioning apparatus resting on tracks 
           [0033]      FIG. 1B  is a perspective view of the lifting and positioning apparatus of  FIG. 1A  with columns and a controller connected thereto. 
           [0034]      FIG. 2A  is a functional flow diagram of the system of  FIG. 1A . 
           [0035]      FIG. 2B  is another functional flow diagram of the system of  FIGS. 1A and 1B . 
           [0036]      FIG. 3  is a functional flow diagram of how loads and positions may be compared according to  FIG. 2B  in order to operate the positioning apparatus of  FIGS. 1A and 1B . 
           [0037]      FIGS. 4A and 4B  are functional flow diagrams showing other aspects of the lifting and positioning apparatus of  FIGS. 1A and 1B . 
           [0038]      FIG. 5  is a side view of part of the lifting and positioning apparatus of  FIGS. 1A and 1B . 
           [0039]      FIG. 6  is a top view of the part of the lifting and positioning apparatus of  FIGS. 1A and 1B . 
           [0040]      FIG. 7  is a side view showing various positions of the lifting and positioning apparatus of  FIGS. 1A and 1B . 
           [0041]      FIGS. 8 and 9  show a prior art lifting and positioning apparatus. 
           [0042]      FIG. 10  is a partial cutaway rear view of a positioning column of  FIGS. 1A and 1B . 
           [0043]      FIGS. 11 and 12  show side and perspective views of a positioning column of  FIGS. 1A and 1B . 
           [0044]      FIG. 13  is a section view of the positioning column of  FIG. 11  shown along section line  13 - 13 . 
           [0045]      FIG. 14  is a section view of the positioning column of  FIG. 10  shown along section line  12 - 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0046]    Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views. 
         [0047]      FIG. 1A  shows base  1000  with lifting columns ( 2020 ,  2120 ,  2220 ,  2320 ) removed. Drive motors  100 ,  101 ,  102 ,  103  are connected to wheels  1110 . The connection between wheels  1110  and the drive motors may include a gearing system, but may also be direct drive. Drive motors include a sensor array  120 ,  121 ,  122 ,  123 , which may include position and/or load sensors. For example, a rotational encoder type sensor may monitor position. Load sensors may include electrical load sensors, torque sensors, mechanical load sensors such as strain/force sensors and the like. The motors are connected to a controller  200 . Optionally, the drive controller  200  may be connected to controller  4000  or drive controller  200  may be absent and drive motors  100 ,  101 ,  102 ,  103  may be connected directly to controller  4000 . It is contemplated that the functions of a controller as shown and described herein may be performed all or in part by one or more of the drive controller  200 , controller  4000  or combinations thereof, therefore use of the term “controller” could indicate various functions, features and calculations are performed by the drive controller  200 , the controller  4000  or the functions, features etc may be performed partially by both the drive controller  200  and the controller  4000 . 
         [0048]    The second track  104  may be elevated and may run perpendicular to the first track  105 , which the positioning apparatus moves on. Although the positioning apparatus is shown having railway style wheels that run on tracks, it is understood that the positioning apparatus can run on wheels that operate on a surface such as a factory or shop floor. It is further understood that the independent nature of the motors shown and described herein can allow the wheels to steer the positioning apparatus without providing for articulating steering joints. Thus, the controller could increase the speed of one or more wheels relative to other wheels in order to steer or re-position the positioning apparatus. 
         [0049]    The controller may be connected to a second position sensor similar to the limit switches described herein. A position indicator  107  and a catch  108  can interact to depress the catch  108  and thus cause the position sensor  106  to signal to the controller that the positioning apparatus is at the position associated with the position indicator  108 . Typically, the position indicator will be aligned so that the track section  3100  of the positioning apparatus will align with the second track  104 . This way, the controller stops movement of the positioning apparatus so that the positioning apparatus is positioned below the second track. This further allows the catches  3200  associated with the track sections  3100  to extend into recesses  3202  to lock the track section  3100  at the proper location. Although the limit switch and position indicator shown herein are mechanically activated, it is understood that electrical, optical and other sensors can be used for the second position sensor. 
         [0050]    When the base moves along the first track, the position sensors associated with the drive motors can determine the position of the base using, for example, rotation sensors. As the base approaches a desired stopping point, the speed of the drive motors can be reduced so that the base slowly approaches a desired position. For example, as the base approaches the position associated with a position indicator, the drive motors could slow down. Thus the control signal can be calculated to achieve this slowing of the base. This allows avoidance of overshooting the a desired position and further avoids any sudden stops or jerking movements, which can potentially be dangerous or can cause damage to the apparatus. 
         [0051]      FIG. 1B  shows a lifting and positioning device  2  having four columns  2000 ,  2100 ,  2200 ,  2300 . Each column includes a lift motor  2020 ,  2120 ,  2220 ,  2320  that rotates a screw (not shown) to move a first support  2010 ,  2110 ,  2210 ,  2310  up and down based on signals received from a controller  4000 . The columns are affixed to a base  1000  that may have wheels  1100 ,  1110  to move the positioning apparatus. It is understood that although the wheels are shown as being adapted to run on rails, wheels that move on other surfaces can be provided. In addition, where desirable, one or both sets of the wheels can be adapted to turn to steer the positioning apparatus  2 . As shown, wires  2030 ,  2130 ,  2230 ,  2330  connect the lift motors to the controller  4000 . It is also understood that the wires may be designed to connect to a power source, and the controller could communicate with the individual lift motors through a wireless connection. Although shown with four columns, there could be more or less columns used, depending on the application. For example, two columns may be appropriate in certain circumstances, with one column on each end of the second support that is connected to the two columns. Further, the apparatus shown in  FIG. 1  may be modified to include one column at each corner of the second support and then columns between, for example columns  2000  and  2300  and columns  2100  and  2200 . It is also contemplated that columns can be placed between the corners to allow for longer track sections. In this case, the width of the base  1000  would be wider and thus the distance between columns  2000  and  2100  would likewise be larger. An additional column between columns  2000  and  2100  may provide added rigidity when the item to be lifted is longer, larger and thus heavier. 
         [0052]    As shown, the controller is separate from the base  1000 . It is understood that the base may be designed to have a location for the controller to affix thereto so that when the base rolls along the wheels  1100 ,  1110 , the controller moves with the base. For example, the drive controller  200  may perform all or some of the functions of controller  4000 . The wires or connections  2030 ,  2130 ,  2230 ,  2330  can have removable connections that allow for a stationary controller to work with columns and supports that are moved into place and then connected to the controller  4000  so that the second support  3000  can be moved up and down in response to a control input. The columns could be interchangeable with the controller to allow for easier maintenance and repair. 
         [0053]    The second support  3000  can include more than one level, for example levels  3500  and  3400 . The upper level  3500  has track sections  3100  extending therefrom. The bottom level  3400  can be used as a platform that allows workers to stand below the rail car part that will be worked on. For example, a rail car wheel assembly may be placed on the track sections  3100  for maintenance and repair. The bottom level  3400  would allow for maintenance workers to replace and repair the wheel assembly and replace or grease various parts. Likewise, the top level  3500  could allow access to different areas of the rail car part. As an example, the lifting and positioning apparatus shown may be what is referred to as a drop table. The drop table may be designed to interlock with a main rail system in an upper position where catches  3200  extend into a corresponding recess adjacent to a gap in the main track to lock the support  3000  in place. The rail car is then placed on the rail, with the wheel assembly to be repaired resting on track section  3100 . The wheel section is released from the rail car and the catches  3200  are likewise released. A link mechanism  3300  is rotated to extend and retract the catches  3200 . The lift motors are then operated by the controller  4000  to move the first supports  2010 ,  2110 ,  2210 ,  2310  down to a level where a worker accesses the bottom level  3400  of the second support  3000 . 
         [0054]    Once the wheel assembly is lowered and removed, the base  1000  may be moved along a secondary track or simply moved out of the way. Then a second positioning apparatus would be moved into place below the main track and a replacement wheel assembly could be lifted up to the vehicle. The catches  3200  would extend to lock the track section  3100  in place and the wheel assembly would then be affixed to the vehicle. The old wheel assembly, now on the first positioning apparatus can be repaired on the positioning apparatus, or may alternately be moved to other locations in the factory or repair shop where repair can take place. 
         [0055]    A number of sensors may be fitted to the positioning apparatus  2 . Position sensor  2004  may read indicator strip  2014  using a laser or other optical device. Alternately a sensor interface  2028  may include a rotational encoder that counts the revolutions of the motor to determine the position of the first support  2010 . Further, limit switches  2006 ,  2008  may be used to designate a stopping position for the second support  3000  at an end of the column. An intermediate limit switch  2016  may be placed between the ends of the column to designate a pre-determined position for the system. These intermediate switches may be adjustable to allow for the pre-set positions to be later modified. Although one intermediate switch is shown, it is understood that multiple switches may be affixed to the columns. Further, although each column is shown having its own set of limit switches, it is understood that the limit switches may be positioned on a single column, and the controller would use other position sensors to keep the second support  3000  and likewise the first supports in the proper position. 
         [0056]    Load sensor interfaces  2002  may read strain gauges to determine the load on individual columns. It is also understood that sensor interface  2028  can include an electrical load sensor that can be used to determine the load on each column. Other types of load sensors may be used, for example, hydraulic load cells, pneumatic load cells, pressure sensors and others. Strain gauges may be arranged in what is commonly referred to as a Wheatstone bridge configuration. These strain gauges are then coupled to a transducer or other device that produces a signal indicative of the load. The signal is transmitted to the controller  4000  for analysis and calculation. 
         [0057]    The controller  4000  is shown with a display  4400 , a processor  4100  and controls  4500 ,  4502 ,  4504 . The joy stick  4500  may be used to move the second support  3000  up and down. As shown, there are four joy sticks, which may be independently linked to the columns to allow for manual control. As an example, manipulation of a single joy stick may cause all four columns to change position in response to the control input. The control program that executes on the processor  4100  will receive the control input that may be indicative of a position change, or a desired position. The control program would then calculate a control signal that would be transmitted to the columns  2000 ,  2100 ,  2200 ,  2300  to change the position of the columns while monitoring the position and load sensors. 
         [0058]    Button  4502  may indicate a pre-determined position that is designated by the intermediate limit switch  2016  or the top  2006  and bottom  2008  limit switches. The key board  4504  may be used to select or input certain desired positions or to indicate various control functions. The controller may provide a graphic user interface that can be used in conjunction with a mouse (not shown). The display  4400  may also be a touch sensitive display that receives user input for the control of the positioning device. 
         [0059]    In  FIG. 2A  wheel assemblies  300  are shown including load sensors  140 , a drive motor  100  and position sensors  130 . The controller compares the load sensor signal  141  to determine load balance  150 , for example on the drive motors or wheels. Likewise, the controller input  154  is compared to compare to the load balance  152 . The controller determines if the drive motors are outside a threshold  156 . If no, the control signal is calculated  158 . If the drive motors are outside a load threshold, the controller determines if the position sensors are also outside the threshold  168 . The controller can calculate a load distribution among the drive motors to generate a calibration for the controller. The controller may maintain the load distribution during movement of the drive motors. The load distribution may also be maintained within a range of loads. The range may be predetermined, set by the operator or another user, calculated based on the amount of load on the drive motors or be within a percentage range. Other scenarios for the range as would be apparent to one of skill in the art are contemplated and these examples are not limiting. 
         [0060]    Also shown, the position sensor signals  131  are compared to determine position  160  of the drive motors/base. The position is compared to the control input  162 . The system determines if motors are outside desired position (or speed) thresholds  164 . If so, the load and position signals are compared  168 . If the motors are within thresholds, the control signal is calculated  166 , and the control signal  176  is generated to move the drive motors, which moves the base along the first track. In some cases, drive motors would be expected to be associated with different thresholds. For example, if there is a curve in the track, the outer drive motors would rotate faster than the inner drive motors. Thus, although the outer wheels spin faster than the inner wheels, the loads would be expected to remain the same in terms of torque on the wheel axle. 
         [0061]    If position and load signals are not both outside thresholds, the system determines if sensors are not working  170 . The control signal may then be calculated from working sensors  174 . If same motors are outside thresholds, the control signal is calculated  172  to bring all motors within desired thresholds, which may be done progressively to avoid sudden jerking motion or sudden position changes. 
         [0062]    In  FIG. 2B , the positioning column  2000  includes a lift motor  2010  a load sensor  2002  and position sensor  2004  that may or may not be connected to the lift motor. The load and position sensors may be connected in other places on the positioning column, for example, the screw  2040 , the first support  2010  or other locations. The load sensor transmits a load signal  2003  to the controller and the position sensor sends a position signal  2005  to the controller. Therefore, if there are four columns, each column sends a load signal and a position signal. The four position signals are compared by the controller to determine the position of each column, or to determine the position of each column relative to a reference. Likewise, the four load signals in this example are compared to determine the load balance or the deviation of certain columns from a reference. For example, if the average load on the columns is 5 tons, this could be the reference. If a particular column has a load of 4.9 tons, his could indicate that the load is off balance or that the position of one or multiple columns needs to be adjusted to balance the load. 
         [0063]    The calculated positions and the calculated loads can be compared to a threshold. This threshold is an acceptable range or percentage that is built into the control program. For example, if the difference in position is within ¼ of an inch, adjustment may not be necessary. Further, since the system may be moving in response to a control input, it is expected that certain variances may be tolerated. The example of a ¼inch above is exemplary only and not limiting. 
         [0064]    The same threshold holds true for a load signal. The controller compares the positions  4304  and then determines if any columns are outside the threshold  4306 . If the calculated or measured loads are within a certain percentage of the average, for example 5%, adjustment may not be necessary. Therefore, in the case where the sensor readings indicate that the columns are within the desired thresholds or tolerances that are acceptable for the correct movement and control of the apparatus, the control signal  4200  could be generated and sent to the motors  2010 ,  2110 ,  2210 ,  2310  to continue moving the first supports and likewise the second support  3000  towards the desired location according to the control input  4002 . 
         [0065]    It is also possible that if a load signal indicates a load outside the threshold, the position could indicate that the second support  3000  is level. For example, if columns  2000  and  2300  both shown a higher load, the item on the second support  3000  may be off center, thus causing the discrepancy. However, if a single column is outside the load threshold, it would be more likely that that column needs to be adjusted, thus the controller could calculate the control signal to balance the load more evenly across the four columns. If columns  2000  and  2100  are both out of the load threshold, this could indicate that the corresponding side of the positioning apparatus needs adjustment. However, if the position sensors indicate that the second support  3000  is level, the off balance load may be due to the load on the second support being off center, thus not requiring adjustment to the columns to level the second support  3000 . 
         [0066]    The control input  4002 ,  154  may be indicative of a specific position. The control input may also indicate a directional. For example, if joystick  4500  is pressed forward, the associated control input would indicate that the operator wishes to move the second support  3000  upwards. The control input may also have a speed indicator. For example, pressing the joystick  4500  all the way forward would indicate a higher speed than pressing the joystick halfway forward between the neutral and maximum positions of the joystick. As discussed above, the keyboard  4504 , buttons  4502  or display  4400  can receive control inputs. These inputs may be associated with particular pre-programmed positions. The pre-programmed positions may, for example, be associated with intermediate limit switches  2016  or with particular linear position indicators or measurements. 
         [0067]    Balancing the load may require moving the object that is resting on the second support. In this case, the control program would ensure that pairs of columns are balanced according to pre-determined parameters. For example, columns  2000  and  2300  may be linked as a balanced pair and columns  2100  and  2200  could likewise be linked as a balanced pair. Therefore, the average load between the four columns may be 5 tons, with Columns  2000  and  2300  each having 4.9 tons and columns  2100  and  2200  having 5.1 tons. Before transmitting a control signal, the controller would also verify the position of each of the columns. If all columns are in a level position, the control signal would not try to balance the load for an evenly distributed 5 tons across all four columns. This is because the likely cause of the unbalanced load is that the item sitting on top of the track sections  3100  is not centered. If the position signals indicate that the second support is level, adjusting the columns to balance the load may result in the item on the top of the track moving or rolling due to a non-level surface. 
         [0068]    In order to avoid abrupt starts and stops when moving the first supports, the controller may calculate the control signal to slow down movement of the first support(s)  2010 ,  2110 ,  2210 ,  2310  as the desired position approaches. Similarly, the controller can calculate the control signal for the drive motors  100 ,  101 ,  102 ,  103  to slow down as a desired position approaches, for example the position where the track section is aligned with the second track. Likewise, the initial movement of the drive/lift motor from a rest position could slowly accelerate the screw/gearing. As an example, upon receiving the control input, the control signal would be calculated by comparison of the positions and loads to verify that the first supports and likewise the second support is starting from a level position. The load on the columns may impact how quickly a load can be sped or up or how long it takes to slow movement. Based on the position and load sensors, the controller can generate the control signal on a case by case basis based on the load on the columns. 
         [0069]    If the initial position is not level, the controller would adjust the columns on an individual basis to achieve a position that is level within the position thresholds that may be either selected or built into the system. This may be considered a calibration procedure that verifies the starting point of a lifting or positioning operation. The load may be off center in relation to the second support as previously discussed, thus once an initial and level position is determined, the load balance would be built into the expected movement and load thresholds for each column. 
         [0070]    The initial calibration of the load balance may be done in relation to a known position. For example, when the track is lifted to the top position  3020 , the limit switches of each column  2006 ,  2106 ,  2206 ,  2306  may be activated on each column to indicate the upper position. Since the limit switches are in a position that is known to be level, the position sensors and the load sensors can be calibrated with the known level position. Thus, when the portion of the vehicle is placed on the track section  3100 , the calibration can assume a level position according to the limit switches. Upon receiving the control input to move from the top position  3020  to the bottom position  3010 , the system could calibrate the position sensors or determine the load balance or both. The load balance may be used in setting the load threshold, which is a range of load values or percentage deviation that are considered acceptable tolerances during movement. The same calibration can be done with intermediate switches that have been previously discussed herein. 
         [0071]    In the case where the load sensor is an electrical load sensor, the calibration may be partially based on previous lifting operations. This calibration may be stored with the lift/drive motor or the controller. If the controller stores a motor specific calibration, the motor may have an identifier that is read by the controller to associate a connected motor with a calibration. The calibration may be necessary due to manufacturing tolerances and efficiency discrepancies between the various motors. For example, one motor may be slightly more efficient than the other three, thus would have a reduced electrical load for the same mechanical load exerted on the first support or on the wheel/axle. Therefore, when the second support is being moved in a level orientation, the electrical load may be expected to be different for each lift motor. There may be more than one load threshold associated with the lift/drive motors. One threshold may be based on specific calibrations for each motor, and another threshold may be based on the range of efficiencies commonly seen in the particular type of motor. For example, the motors may have factory calibrated ranges of efficiency and torques that are expected and verified for a motor of a given size. A motor falling outside the factory calibrated efficiency ranges could indicate that the motor is in need of repair. Thus the controller can verify the expected ranges of performances of the motors and can likewise produce a signal for display on the controller, where the signal can indicate which motor needs repair. 
         [0072]    When calculating the control signal, there could be a speed associated with the rotation of the motors. As previously discussed, the position sensors may be a rotational encoder that counts the number of rotations of the motor or screw. Based on gearing and the pitch of the screw threads, the position of the first support can be calculated using time and number of rotations. Likewise, the gearing associated with the drive motor can be used to determine the speed and thus position of the wheels. Alternately, the position sensor can be a linear or true position sensor that measures the position relative to the columns or relative to the first track/ground, for example the optical sensor  2004  and the position strip  2014  previously discussed. Numerous types of linear position sensors can be interchanged with the optical sensor  2004  as would be apparent to one of skill in the art. 
         [0073]    The controller could have a desired motor speed that would equate over time to desired positions. Upon transmitting the control signal to the motor(s), the controller can verify that the motors and the first supports/wheels are moving according to expected calculations. At the same time, it is possible that the position sensor could miss a rotation or a marking and thus begin reading incorrect positions. Since the load balance was done initially, if one sensor fails, the other sensors can be used to verify that the second support is maintained at a level position during the positioning operation and that the wheels maintain desired speeds and torques. 
         [0074]    In  FIG. 3  a flow diagram shows the calculation of the calibration based on the activation of the limit sensors. In order to begin the calibration routine, a control input  4002  may have been received to move the second support  3000  away from the position associated with the limit switch. Alternately, upon reaching a limit switch or intermediate limit switch, the position and load signals at the time the limit switch or intermediate switch was activated can be used for purposes of calibration. Depending on the sensors used, an electrical load sensor may not show any load when the first supports are stationary. In this case, the calibration may only impact the position sensor. Although, once movement has begun, the load sensors may be re-calibrated shortly after movement commences under the assumption that the position of the first supports after a small movement will remain in an appropriate position. If the limit sensor is not activated, the original calibration can be maintained  5002 , as discussed previously, if the limit switch was recently de-activated, it may be appropriate to re-calibrate or verify the calibration of the load sensors. When calibration is to occur, the load is calculated on each column  5100  using the load sensor signal  2003 . The position of each column is calculated  5102  using the position sensor signal  2005 . The loads of each column are compared  5200  to determine load balance and the calculated position of each column is compared to the known limit sensor position  5200 . Using these comparisons  5200 ,  5202 , a calibration is generated  5300 . This calibration is then used by the controller  4000 . In some cases, the motor may store the calibration  2010  if the apparatus is to be used with a different controller. This would allow a positioning base with columns to move along the factory to a different location using the wheels  1100 ,  1110  as previously described. At the different or second location, the apparatus can then be connected to a controller and the calibration that was sent to the motor can be read in order to re-use the previously calculated calibration. It is also contemplated that the calibration routine can be done based on a user input to the controller. Thus, if appropriate, the user could request a calibration once a load is placed on the second support, and the controller would run the calibration routine. 
         [0075]    In  FIG. 4A  one aspect of a safety feature of the present device is shown. The control input  154  is received for the drive motors. The position of the lift track  3100  is determined  400 . If the lift track is elevated  402 , a safety alert  404  may be returned. It may be possible to override the safety alert, but typically, the system will request confirmation that the lift track  3100  should be lowered  406 . The confirmation is received  408  and a control signal is generated to lower the lift track  410  according to the controller parameters discussed herein. This control signal is sent one or more of the to the lift motors  412 , and signals  2003 / 2005  may be used to monitor the position of the lift track and to verify that the lift track is no longer in the elevated position. In one example, the safety feature may require that the first supports are in a bottom position such that bottom limit switches indicate the appropriate position. 
         [0076]    When the lift track is no longer in the elevated position, the control signal may be calculated to move the base  414 . The position of the base may be determined, and once the base is in the desired position, movement stops  418 . In order to monitor position, the second position sensor  106  may be used to determine if a pre-set position has been reached. In addition rotation sensors  420  can likewise be monitored. The control signal  176  is generated to move the base and is sent to one or more drive motors  100 ,  101 ,  102 ,  103 . If appropriate, a calibration may be used to calibrate load sensors or adjust rotation sensors based on the second position sensor activation  422 . 
         [0077]    In  FIG. 4B , when the control signal  4200  is transmitted, a corresponding movement and load could be expected to be read on the sensors. Based on the control signal  4200  and the elapsed time  6000  a comparison  6100  can determine the expected position  6002  and/or the expected load  6004 . The expected load and or positions are compared  6200  to the position signals  2005  and the load signals  2003 . If the actual positions and/or loads are the same as expected  6300 , the system continues with the control signal  6302  and the associated parameters. The control signal in this case would continue to cause the motor to rotate according to the parameters that were calculated based on the control input. These parameters may include gradual speeding and slowing of the rotation at the ends of the movement cycle, and may include pre-determined positions. If the loads or positions are not the same as expected, the system compares the loads and positions to thresholds  6400 . If the loads are outside acceptable thresholds, the control signal may require adjustment or re-calculation for one or multiple lift/drive motors or columns  6402 . In this case, the adjusted control signal is sent to the motor(s) in order to keep the first supports and likewise the second support level. The thresholds may be calculated in part based on the calibration referenced in  FIG. 3 . If a load is off balance or off center of the second support, the positions of the columns would be expected to be equal, but the loads would not. Typically, the discrepancy of the loads would be associated with pairs of columns. For example, it would be expected that loads on columns  2000  and  2300  would be similar or the same (within a first threshold), and the loads on columns  2100  and  2200  would be the same (within a second threshold). The ranges of the first and second thresholds may be the same size in terms of load. For example a range of 200 lbs could be associated with the threshold where the difference between columns  2000  and  2300  should be less than 200 lbs in order to be within the threshold, assuming the load is off center and two thresholds are used in order to maintain a level second support  3000 . Similar ranges based on amperage or wattage may be associated with electrical load sensors if used. Ranges can also be applied to torque on the wheels/axles in order to maintain the drive motors within appropriate load balances. 
         [0078]    In  FIG. 5 , motor  1200  may be connected to the wheels  1110 . It is understood that there may be a motor for each set of wheels  1100 ,  1100  or a single motor coupled to the front and back wheels. It is further understood that one or both sets of wheels may rotate about an axis orthogonal to their axles in order to steer the positioning apparatus  2 . Also shown is an actuator  3310 , which may, for example be a solenoid, motor or a pneumatic or hydraulic cylinder. It is understood that other types of actuators may be used to manipulate the linkage  3300 . The actuator  3310  is used to extend and retract the catches  3200 . A downward force on bar  3302  could extend the catches, whereas an upward force would retract the catches  3200 , both actions causing a rotational force or torque on linkage  3300 . The screws  2240 ,  2340  can be rotated by the motors  2220 ,  2320  in response to control signals from the controller. 
         [0079]    In  FIG. 6  the surface of the second support  3000  may include texture  3510  to provide additional traction for repair or factory personnel. It is understood that the texture may exist on both the upper  3500  and lower  3400  levels of the second support. 
         [0080]      FIG. 7  shows top  3020  and bottom  3010  limits of the second support  3000 . The top and bottom limits may be monitored using limit switches  2006 ,  2008  as shown in  FIGS. 11 and 12 . The limit switches  2006 ,  2008  are in communication with the motor and/or the controller. For example, the limit switches may send a signal to the motor or the controller to stop the first supports from moving. For example, if the second support is in the top position  3020  and the motors continued to rotate, the female threaded sections of the first supports could become un-connected to the screw, thus causing placing a potentially heavy load in a precarious position. The use of the limit switches can prevent the motor from rotating the first support off of the screws. It is also contemplated that the positioning of the limit switches  2006 ,  2008  can be adjustable based on common positions that are expected to be used with the positioning apparatus  2 . It is also contemplated that intermediate switches may be placed along the column, for example between switches  2006  and  2008 . The intermediate switch could likewise be set up to provide an intermediate stopping point that is commonly used in a given application. The intermediate switch could be associated with different logic and or electric controls than the limit switches. For example, the limit switches may be common positions, but these switches also provide a safety stop that prevents the first support and the screw from becoming uncoupled. The intermediate switch simply provides a signal that indicates to the motor and/or the control program that the second support  3000  has reached a pre-configured position. 
         [0081]    It is also contemplated that the limit switches or the position sensor  106  can be directly linked to the power supply to the motor. Thus, when the limit switch is reached, the power to the motor stops for the particular column. If one column stops, the controller would then limit the movement of the other columns to a pre-determined range. For example, in case a limit switch is not working properly, movement of one column could be stopped, allowing the other columns to continue movement could damage the machinery. 
         [0082]    It is also contemplated that the controller will allow for operator overrides for a number of the positioning routines that would allow the load to be moved under a manual operation or a manual override. 
         [0083]    In  FIG. 10 , a partial cutaway shows screw  2040  and upper bearing  2042  of the column. In  FIGS. 11 and 12 , the bottom  2008  and top  2006  limit switches are shown. Flange  2004  is adapted to releasably secure to the base of the positioning apparatus, for example, with nuts and bolts.  FIG. 13  shows the column along section line  13 - 13 . The motor  2020 , screw  2040  and bottom limit switch  2008  are likewise shown. In one embodiment a sensor interface  2028  is coupled to the motor. This sensor interface may include a rotational encoder that measures the position of the first support by counting the number of rotations of the screw. It is also understood that the sensor assembly  2028  can further include voltage and/or amperage sensors that can likewise detect the power drawn by each motor and thus determine the load on the columns. In  FIG. 14 , a cross section of the column is shown along section line  14 - 14 . The bottom bearing  2044  is coupled to the screw  2040 , and the first support  2010  can move up and down in response to rotation from the motor. The column has a flange at the bottom end that can connect to the base of the positioning apparatus. This flange can be releasably secured so that one column can be replaced with a replacement column with minimal downtime. The sensor and electrical connections of the new column can likewise connect to the controller with releasable connections so that the columns can be quickly connected and disconnected from the overall positioning apparatus system. 
         [0084]    The control input may indicate a desired position that is associated with the intermediate switch. In this case, when the intermediate switch is activated, a signal is sent to stop the motor. It is understood that the signal can also cut power to the motor by opening the circuit. Although the intermediate and limit switches each provide a specific position, it is understood that other position and load sensors may be used in order to smoothly control the lifting and positioning of the load. For example, as the first or second supports approach a desired position, the controller could progressively slow the rotation of the motor so that the desired position is not passed and/or so that when the desired position is reached, there is not an abrupt halt to the lifting motion. The limit switches may prevent the motors from continuing to rotate and thus forcing the first support off the end of the screw. 
         [0085]    Although some mechanical limit switches have been shown, it is also contemplated that optical sensors similar to the optical position sensors can be used as limit switches. For example, the optical sensor may send a light wave towards a reflector, and when the first support or another object is placed between the light and the reflector, the optical limit switch would transmit a signal to the controller that indicates the first support has reached the position of the limit switch. The limit switch may be associated with a logic in the controller or overall system that is a on or off operation. For example, when the limit switch is in the “on” position or operation, the first supports will move. When the limit switch is in the “off” position or operation, the controller or overall system will know not to move the first support past the position of the limit switch. For example, the top limit switch would reduce the likelihood that the first support would be moved to a point where it came off the screw at the top position. 
         [0086]    When the sensors are indicative of a position of the first support they are likewise indicative of a position of the second support, because the first and second supports are connected. For example, if there are four sensor signals that each indicate the position of one of the first supports, the sensors both collectively and individually would indicate a position of the second support. As a further example, first support  2010  as shown is connected to the second support  3400  at an interface that uses a number of nuts and bolts. Thus, a signal indicating the position of the first support would indicate that one corner or location of the second support is in the same position. At the same time, each signal indicative of the position of one of the other first supports could indicate that different locations on the second support are in a different vertical position or a different position relative to a reference. 
         [0087]    Although the invention has been described with reference to a particular arrangement of parts, features and the like, these are not intended to exhaust all possible arrangements or features, and indeed many modifications and variations will be ascertainable to those of skill in the art.