Universal end of arm robot tool

An end of arm tool subassembly includes three identical linear drive mechanisms connected directly together to provide three directions of movement. Each linear drive mechanism includes a base defined by a longitudinal axis and a slide movably coupled to the base. The base has at least one mounting surface disposed parallel to the longitudinal axis and an end mounting surface disposed perpendicular to the longitudinal axis. The slide traverses in a direction parallel to the longitudinal axis and has a slide mounting surface thereon. One of the identical linear drive mechanisms is directly attached to the end mounting surface of the base of another linear drive mechanism to provide two of the three directions of movement.

BACKGROUND

Industrial manufacturing faces many challenges in making consumer products faster, better and cheaper. As a result, manufacturers continuously explore the feasibility of assisting manual labor with automated tools. Such devices include, among others, computer controlled handling systems, which may pick and place parts in and out of process machines faster, more accurately and, therefore, increase the production throughput and the quality of the part.

While responding to market needs, manufacturers also need to make provisions for fast product changes on the same production line. While manual labor can easily adapt to such changes, automation tools must be physically reconfigured. Such reconfiguration results in down time, which in turn elongates the payback period of the tool.

In order to reduce down time, as result of tool changes, manufacturers are continuously searching for intelligent tools, which may be reconfigured upon controller command in a very short time and, therefore, quickly handle a need for a product change. Such a tool is sometimes referred to as an Intelligent End of Arm Tool (iEOAT).

iEOATs are gaining increased popularity among automotive manufacturers. This is because, in a typical automotive assembly line, exterior body parts, such as hoods, roofs, doors and wheels, can change from one car model to another. Such changes can involve changes in shape, color, size, texture. Accordingly, the tools that handle these parts must therefore change with it.

Automotive body parts are usually welded to each other in their manufacturing process. The body parts, which are being joined together are positioned along the assembly line in frames, fixtures or held by a robot while another robot moves in space to weld them. The need therefore is to have an intelligent tool at the end of the robot arm which will adapt to the changes in the body part. The iEOAT addresses this need by adding a higher level of intelligence and manipulation capabilities to capital equipment used in assembly lines.

In simple terms, the iEOAT may simply be a 3D adaptive gripper, which is mounted at the end of a robot arm, which carries locating pins and clamps. In the manufacturing process, the robot moves its arm at high acceleration in six degrees of freedom. The gripper at the end of the arm moves in close proximity with the car body part, and then moves slowly such that the pins locate the part. The gripper then closes its fingers around the body part and moves it quickly, once again, at high acceleration to the assembly point. The intelligent reconfigurable 3D gripper has the capability of adapting the location of its “pointing fingers” (pins) and “pinching fingers” (clamps) to the size and shape of the body part. However, since the shape of automotive body parts are three dimensional, the iEOAT must have the capability to adapt its finger's positions in three dimensions.

By using an iEOAT system in car manufacturing lines, automotive manufacturers may run small batch production on the same assembly line without the penalty of excessive downtime, which otherwise may be needed to change tools from one car model to the other.

However, conventional end of arm robot tools have one or more of the following limitations:

1. They consist of many accessory parts, like mounting brackets and support brackets, placing a burden on stocking many spare parts;

2. They lack standardization such that each tool requires custom design;

3. They are heavy, which limits the number of parts that the robot can carry;

4. They lack stiffness, which may damage motion components, reduce repeatability;

5. They are large, which limits the number of components which may mount on the robot;

6. They have “finger” motion, which is limited to one or two dimensions, which may limit the number of car models the robot may handle with the same tool;

7. Their stages have short travel of each finger which may limit the reach needed to handle a large number of car models;

8. They are custom made through a long engineering process consuming long setup time;

9. They are relatively expensive since their adaptability is to a limited number of car styles and they have to change with each new production line new car styles change.

Accordingly, it would be desirable to provide a universal end of arm robot tool that addresses all of the above drawbacks.

SUMMARY

In one aspect of the present disclosure, an end of arm tool subassembly is provided. The subassembly includes three identical linear drive mechanisms connected directly together to provide three directions of movement. Each linear drive mechanism includes a base defined by a longitudinal axis and a slide movably coupled to the base. The base has at least one mounting surface disposed parallel to the longitudinal axis and an end mounting surface disposed perpendicular to the longitudinal axis. The slide traverses in a direction parallel to the longitudinal axis and has a slide mounting surface thereon. One of the identical linear drive mechanisms is directly attached to the end mounting surface of the base of another linear drive mechanism to provide two of the three directions of movement.

In a preferred embodiment, each linear drive mechanism includes three mounting surfaces arranged along the longitudinal axis on a back of the base such the linear drive mechanism has at least five mounting surfaces. The slide is traversable along a front of the base opposite the back. Each of the mounting surfaces preferably includes a plurality of mounting holes and the base preferably includes at least one recessed pocket formed in a side of the base for permitting access to the mounting holes of at least one of the mounting surfaces.

Each linear drive mechanism preferably includes at least one rail supported by the base, a threaded lead screw rotatably supported by the base, a nut threadably coupled to the lead screw and a motor for rotating the lead screw. The nut traverses along the longitudinal axis as the lead screw rotates and the slide is attached to the nut and is slidably coupled to the rail. The rail and screw may be contained within an interior compartment of the base. In this case, the linear drive mechanism further includes a flexible bellows cover substantially covering the interior compartment for protecting the rail and screw.

In another aspect of the present invention, an end of arm tool for a robot is provided. The tool includes at least two of the subassemblies described above, wherein the base of one of the linear drive mechanisms of one subassembly is directly connected to a base of one of the linear drive mechanisms of another subassembly to form a rigid frame member.

In a preferred embodiment, an end mounting surface of the base of one of the linear drive mechanisms of one subassembly is directly connected to an end mounting surface of the base of one of the linear drive mechanisms of another subassembly to form the rigid frame member. The tool preferably includes four rigid frame members directly connected to each other to form a rigid rectangular frame. In this manner, the frame includes four slides traversing in a first direction and four slides traversing in a second direction perpendicular to the first direction.

In another aspect of the present invention, a method for configuring a plurality of linear drive mechanisms, as described above, to form an end of arm tool for a robot is provided. The method includes determining the global coordinates of a plurality of pick-up locations of a work piece to be manipulated by the tool, determining a required output of the tool based on a desired path of travel of the workpiece, displaying a graphical representation of a configuration of the linear drive mechanisms arranged to perform the required output of the tool and optimizing the configuration by determining the optimum mounting surfaces for directly connecting one linear drive mechanism to another.

In a preferred method, a plurality of graphical representations of optional configurations are displayed, wherein each optional configuration is displayed along with a calculated merit value representing at least one of a cost, weight, stiffness, complexity, configuration time, number of parts, reportability, drivability, programming time, teaching time, design time and implementation time.

Thus, the present invention provides a novel linear positioning stage, which can be used in an iEOAT to position a fixture part such as a pin, clamp, vise, gripper, finger or holding bracket in XYZ position, and having all the desirable characteristics described above.

Since typical body parts have numerous geometrical constraints, the tool of the present invention has been made small. In addition, the tool of the present invention is protected from harsh environments of shock, vibration, temperature changes, and welding residues. Since the robot needs to carry it at high acceleration, the tool has been made light weight. Since the clamping forces may need to be high, the tool of the present invention has been made robust and stiff. Since the tool will typically be subjected to thermal changes, the tool of the present invention has been designed to accommodate thermal deformation without structural distortion. The tool of the present invention is also designed to be accurate, reliable and simple enough to replace in short time. Finally, the tool is modular in nature, thereby eliminating the need for additional mounting brackets and accessories and therefore reducing cost.

DETAILED DESCRIPTION

As used throughout herein, the term “tool” is defined as a device, (such as a pin or a clamp), which is used to handle or process a product such as an automobile body part. The term “iEOAT” is defined as an electromechanical system consisting of frames, XYZ stages, brackets, cables, which carry tools such as clamps and pins and can be reconfigured by intelligent control system to handle and process several products with different size and shape. The term “XYZ subassembly” is defined as a system of interconnected stages and cables which are mounted to the iEOAT and carry a tool such as pin or clamp. The term “stage” is defined as an electromechanical device, which can move under computer control in one specific direction. The term “all in one” is defined as a stage that can connect to another “all in one” stage and be in hundreds of different XYZ configurations without brackets. The term “universal iEOAT” is defined as an iEOAT consisting of several XYZ subassemblies, which can be interconnected to each other without any brackets.

Referring first toFIG. 1, a universal end of arm robot tool subassembly10according to one embodiment of the present invention is shown. The subassembly10generally includes three identical linear drive mechanisms12, (often referred to herein as “stages,” or, in the singular, as “a stage”), directly connected to one another in an XYZ configuration. As will be discussed in further detail below, the subassembly10can be assembled in a multitude of configurations to form a universal reconfigurable end of arm robot system, as shown inFIG. 14, where each XYZ end of arm subassembly consists of several “all in one” stages, as shown inFIG. 6, which carry an of arm tool such as a clamp or a pin.

Returning toFIG. 1, a first linear drive mechanism12a, which drives a slide in a first direction (X-axis), is attached to the end of a robot arm (not shown). The first linear drive mechanism12ais directly attached to a second linear drive mechanism12b, which drives a slide in a second direction (Y-axis), perpendicular to the first direction. The second drive mechanism12bis, in turn, directly attached to a third linear drive mechanism12c, which drives a slide in a third direction (Z-axis), perpendicular to the first and second directions. A workpiece manipulator14, such as a locating pin or a gripper, is attached to the slide of the third linear drive mechanism12c.

As a result, the workpiece manipulator14is provided with three directions (XYZ) of movement with three identical linear stages. Also, because the stages are connected directly together, there is no need for additional mounting brackets.

FIG. 2is an exploded perspective view of one of the identical linear drive mechanisms12shown inFIG. 1. The linear drive mechanism12includes a boxed frame16designed to provide a stiff and light weight construction to the mechanism and to resist structural deformations. The boxed frame16is preferably made of aluminum or other light weight, but strong material. The frame16defines a recessed compartment18and is formed with an exterior side extension20on the bottom of the frame. Extension20also serves as an integrated Z bracket, which stiffens the stage when mounted vertically on any mounting surface of the present invention.

The bottom of the boxed frame16, together with the side extension20, provide a mounting surface22for the end of the robot tool arm, or to another linear drive mechanism. Opposite the mounting surface22, the side extension provides a mounting surface for a motor24, a motor cable26and a transmission case28.

The recessed compartment18defines a longitudinal space for accommodating a lead screw30. The lead screw30is supported within the compartment18at its opposite ends by rotary support bushings32, which are fixed to the boxed frame16, but allow for rotation of the lead screw30within the compartment. The compartment18is designed with a minimal depth so as to mount a nut34and a slide36in a vertical orientation without interference, and without extending the height more than the required minimum.

The lead screw shaft30has built in friction, which eliminates the need for a brake in vertical and horizontal orientation of the stage. It is supported by two rotary bearing on the two ends. Preferably, a bearing32on one end is fixed to the boxed frame16as a thermal expansion pivot. The bearing on the other end is a bushing, which lets the lead screw shaft expand with respect to the boxed frame without generating a distorting thermo-couple effect. The shaft, therefore, also serves as a structural element in minimizing the size and weight of the stage.

The nut34has an internal thread adapted to engage the external thread of the lead screw30. When threadably attached to the lead screw30, the nut34will traverse in a linear direction along the length of the recessed compartment18as the lead screw rotates. The slide36is attached to the nut34and extends outside of the recessed compartment18. Thus, as the nut34travels within the compartment18, the slide travels outside the boxed frame16.

A linear rail38is fixed to an exterior surface of the boxed frame16. The linear rail38may be a separate part attached to the boxed frame, or it may be integrally formed in an exterior surface of the frame. An integrally formed rail minimizes hardware, and reduces alignment with banking surfaces and hardware and, therefore, reduces assembly time. An integrally formed rail further adds high stiffness to the frame16, while reducing the risk of loose hardware due to shock and vibration.

A linear puck40is fixed to the slide36and is movably coupled to the rail38. In this regard, the puck40may be formed with a groove or slot sized to receive the rail in a sliding manner. The groove may include a retaining lip so as to limit movement of the puck only in the direction of the rail38. The puck40and/or the slide36provides a mounting surface for another linear drive mechanism12, a tool accessory14or the end of a robot arm, as desired. In this regard, the slide36is preferably square in size to optimize the mounting footprint of the XYZ configurations.

The compartment18and the rail38are covered by flexible bellows-like covers42provided on opposite sides of the slide36in the longitudinal direction. The bellows-like construction of the covers42allow the covers to move in a telescopic fashion. One side of the covers protects the lead screw30from contamination and environmental particles such as welding residues. The other side of the covers protects the linear rail. Both the linear rail38and the lead screw30require periodic lubrication to assure longevity and high reliability. The cover design is intended to allow quick access to the lubrication points and to internal mounting hardware. This reduces down time and provides simple access to assembly and disassembly of the stages.

As mentioned above, the motor24is firmly mounted to the side extension20of the frame16. The side extension is thus provided with clearance holes therethrough to provide easy access to mounting holes in the motor. The motor height and width is restricted to the height of the frame but unrestricted in length. It can therefore incorporate high enough torque and feedback devices such as an encoder or a resolver, and, as may be needed, a gear reducer and a brake. The motor24can be any type of motor, such as geared motors, linear motors, belt drives, and linear steppers.

The drive shaft of the motor24engages a gear arrangement44contained within the transmission case28. The gears of the gear arrangement44are intended to provide parallel motor drive transmission. They may be used at a 1:1 reduction to provide transmission or they may include a gear reduction ratio to increase the motor torque. This option may eliminate the need for an integrated gear inside the motor therefore reducing cost and increasing reliability. The gears require periodic lubrication to assure longevity and high reliability. Lubrication can easily be provided through access holes in the transmission case28. They are preloaded through motor mounting to minimize backlash. The transmission case encloses the gears and provides support to the motor shaft and the lead screw shafts. It therefore adds to the robust design of the stage.

The cable26is integrally connected to the motor24for power, and feedback. The cable26has connectors on the other end to connect to the user's amplifier, which is mounted in remote. The cable is routed quickly with wide service loops to the cable support surfaces on the other stages. It is also fixed to the external walls of the frames with quick tie wrap fixation.

The embodiment shown inFIGS. 1 and 2thus provides a tool10that requires a common stage with simple integrated parts. The tool10serves as a compact robust axis to be quickly integrated into robot or machine bases, or to any other stage in XY, or XYZ configurations and to the end tool of the user. The result is a compact, robust stage, which has minimum number of parts. It has easy access to mounting for repairs and maintenance. It is protected from the environment and gives the freedom of optimizing the motor and encoder size to fit the application requirement of force and velocity.

In order to provide the desired light weight and rigidity the linear drive mechanism12can be specially designed in several ways. For example,FIG. 3shows a cross-section of an alternative embodiment of a linear drive mechanism12ain which two rails38aand38bare provided on perpendicular exterior surfaces46aand46bof a boxed frame in the form of a solid base16a.

In the embodiment shown inFIG. 3, the base16ais preferably manufactured by extrusion of a light-weight, but rigid material, such as aluminum. The base16aincludes an integrated Z-bracket48, which defines a compartment for housing the motor24and the cable.

As mentioned above, one linear rail38ais mounted to one exterior surface46aof the base16a, while another linear rail38bis mounted on a second exterior surface46bof the base, which is perpendicular to the first surface46a. As described above, each rail38a,38bmay have one or more moving pucks40a,40b. The pucks40a,40btogether are connected to a linear slide36, which may carry a process moving load50, or other motion accessories, such as a motion stop clamp52.

The advantage of the perpendicular rail set38a,38bis to minimize the puck force reactions to external forces and moments in all directions. It should also be noted that the advantage of the two rails on two perpendicular planes is the considerable reduction of moment loading of the pucks40a,40b, and the reduction of reaction forces to external moments due to maximizing the possible distance between the pucks.

To further provide the desired light weight and rigidity to the linear drive mechanism12, the base itself can be specially designed in several ways. For example,FIG. 4shows a cross-section of another alternative embodiment of a base16bin the form of an extrusion having integral stiffeners.

The base16bshown inFIG. 4is an extrusion for a light weight positioning stage, which maximizes the stiffness to bending in normal and transverse directions as well as the stiffness in torsion. This is accomplished by providing integral thin wall stiffening ribs in both normal and inclined directions. Specifically, the base includes external stiffening ribs54, arranged in a square configuration forming a periphery of the base, as well as internal stiffening ribs56arranged in a cross configuration within the external ribs.

The base16bis further preferably formed with perpendicular rail mounting surfaces58a,58b, which are an integral part of the external ribs54. The internal ribs56form an inside compartment60, which accommodates the actuator mechanism, such as the ballscrew or the linear motor (not shown). Both the external and internal ribs54,56also include threaded mounting holes62at end faces thereof for mounting end caps (not shown). At least one of the external ribs54is further formed with at least one integral mounting rib64, which serves as a Z bracket, for mounting the base to a robot arm or to another base.

FIG. 5shows another embodiment of a base16cin the form of an extrusion with crossed aluminum stiffeners and compartments for “sandwiched” stiffeners of composite material (e.g. carbon fiber) on its periphery. In particular, the base16cis an aluminum extrusion having an outer wall66forming a rectangular periphery. Two linear rails38a,38bare mounted to an outer face of one of the walls, and each rail has a puck40a,40bcoupled to the rail in a sliding manner.

The base16cof this embodiment further includes an inner wall68spaced from the outer wall66to thereby form a compartment between the inner and outer wall. The inner wall68serve as stiffeners for bending and torsion and the compartments70receive composite stiffeners72to further provide stiffness to the base. The stiffeners72may be fastened, for example by glue, pins or bolts, to the enclosed compartment defined between the inner and outer walls66,68. Together they form a “sandwich” configuration, which provides enhanced stiffness and rigidity in bending and torsion.

The base16cis further preferably formed with cross stiffeners74, which provide additional rigidity to bending and twist, and a circular stiffener76. The circular stiffener76forms a compartment communicating with the exterior of the extrusion for accommodating the lead screw, belt or linear motor (not shown).

In all embodiments, the base is uniquely designed to provide maximum modularity benefits to the linear drive mechanism of the present invention. Specifically, as shown inFIG. 6, the base and slide of the linear drive mechanism of the present invention provide five (5) mounting surfaces1,2,3,4,5for mounting to a robot arm or to another linear drive mechanism. The slide36of each drive mechanism provides a first mounting surface1, the longitudinal end78, opposite the motor, provides a second mounting surface2and the back surface80, opposite the slide36, provides three separate mounting surfaces3,4,5spaced along the length of the base. Thus, the linear drive mechanism of the present invention allows for numerous assembly configurations.

For example,FIG. 6shows three identical linear drive mechanisms12a,12b,12cconnected together in one arrangement. A first linear drive mechanism12ais connected to the end78of a second linear drive mechanism12bvia its third mounting surface provided on the back face of its base. The second linear drive mechanism12bis connected to a third linear drive mechanism12cvia a slide to slide connection. Specifically, the first mounting surface1provided on the slide of the second linear drive mechanism12bis attached to the first mounting surface1provided on the slide of the third drive mechanism12c. Any one of the remaining mounting surfaces can be attached directly to a robot arm. Similarly, a workpiece manipulator, such as a pin or gripper, can be mounted to one of the mounting surfaces for full XYZ travel.

FIG. 7shows in further detail the multiple mounting capabilities of the linear drive mechanism of the present invention. Specifically,FIG. 7shows a first linear drive mechanism12aconnected to a second linear drive mechanism12bin a slide-to-slide connection. This can be accomplished by directly fastening the slides together with suitable bolts.

As can be seen inFIG. 7, the back surface80of each extruded base16has a plurality of mounting holes82formed therein. The mounting holes82are equally spaced along the length of the base16and are provided adjacent both lateral edges of the base at equal distances apart. In this manner, the back surface80of the base16can be divided into three separate mounting surfaces3,4,5spread out along the length of the base.

To provide access to these mounting holes82from both directions, the sides of each base16are formed with access pockets84having a depth so as to communicate with the mounting hole and to enable insertion and tightening of a mounting bolt.

The bases16shown inFIG. 7are also provided with an end cap86fastened to one longitudinal end thereof. The end cap86can be fastened with bolts engaged with threaded holes formed in the end of the base, as described above. The end cap86includes additional mounting holes88formed therein to provide the second mounting surface2for the drive mechanism12.

For example, as shown inFIG. 8, the end cap86includes mounting holes88that have a spacing in the lateral direction of the base16that matches the lateral spacing of the mounting holes82on the back surface80of the base16. The spacing in the other direction for all of the mounting holes will also match so as to enable total mounting capability between all mounting surfaces1,2,3,4,5of multiple linear drive mechanisms.

The slide36also includes mounting holes89for mounting the slide to any of the mounting surfaces of another linear drive mechanism. The mounting holes89of the slide will preferably have an arrangement of alternating threaded holes and counter-bored through holes so as to allow a bolted connection without nuts. The lateral spacing between the mounting holes89provided on the slide36matches the lateral spacing of the end cap mounting holes88and the base mounting holes82. The spacing between adjacent threaded holes of the slide in the other direction will match the longitudinal spacing of all of the other mounting holes. Likewise, the spacing between adjacent counter-bored holes of the slide in the other direction will match the longitudinal spacing of all of the other mounting holes. This will allow for selection of one set of holes in one slide to a cooperating set of mounting holes in the other slide.

As can also be seen inFIG. 8, the access pockets84of the base16have a depth to also enable access to the mounting holes88of the end cap and the mounting holes89of the slide. This will allow insertion of a bolt from one direction and a cooperating nut from the other direction for fastening two mounting surfaces together.

The front surface90of the base16, opposite the back surface80, may also be provided with a plurality of mounting holes92similar to the back surface. These mounting holes92, which are also accessible via the access pockets84allow for insertion and tightening of bolts for one method of mounting one slide36to another. After assembly, the mounting holes92may be covered by edge guards94, as shown inFIG. 8.

FIG. 7ashows another method for attaching the slide36of a first linear drive mechanism12ato the slide36of another linear drive mechanism12b. In this embodiment, a pair of clamping fingers94is mounted to each slide36for engagement with the opposite slide. Each slide36is also formed with a retaining rib96adapted to be captured and retained by the clamping finger94of the opposite slide. The clamping fingers are releasably attached to their respective slides by conventional bolts or screws. With the retaining rib96of one slide retained by the clamping finger94of the other slide, the two slides can be secured together.

Returning toFIG. 8, an alternative embodiment for mounting the motor24is shown. In this embodiment, the motor24is mounted directly to the end of the base16opposite the end cap86. This provides a more compact linear drive mechanism, which eliminates the need for a side bracket and a transmission case. In this embodiment, the third mounting surface3, provided on the back face80of the base16, is disposed adjacent the motor24, the fourth mounting surface4is provided midway between the motor and the end cap86, and the fifth mounting surface5is disposed adjacent the end cap, which provides the second mounting surface2.

FIG. 9shows the linear drive mechanism12shown inFIG. 8, with the slide, covers and edge guards removed. In this drawing, it can be seen how the base16is formed with a central recessed compartment18defining a longitudinal space for accommodating the lead screw30. The lead screw30is supported within the compartment18at its opposite ends by rotary support bushings32, and a brake, which are fixed to the base16, but allow for rotation of the lead screw30within the compartment. The motor24is coupled to one end of the lead screw30for rotating the lead screw. The compartment18also accommodates the nut34, which is threadably coupled to the lead screw30for movement up and down the length of the compartment as the lead screw rotates, as described above.

Two linear rails38aand38bare fixed to a front surface of the base16and two pucks40are slidably coupled to each rail. The slide36(not shown inFIG. 9) is, in turn, attached to both the nut34and the pucks40so that, as the nut is driven up and down the length of the compartment18, the slide travels along the rails via the pucks. The covers42(not shown inFIG. 9) protect both the interior compartment18and the rails38a,38b.

FIG. 10is a cross-sectional view of the linear drive mechanism12shown inFIG. 9. As can be seen inFIG. 10, the compartment18is designed with a minimal depth so as to mount the nut34in a vertical orientation without interference, and without extending the height more than the required minimum.

In this regard, a specially designed nut34is preferably provided to allow for a minimum depth of the compartment18. As shown inFIG. 11, the specially designed nut34includes an end plate portion34aand a slide support portion34b. The end plate portion34aand the slide support portion34bmay be formed integrally, or they may be separate parts attached together. The end plate portion34ais formed with a threaded hole34cto engage the external thread of the lead screw. The slide support portion34bhas an upper surface34dhaving threaded mounting holes for mounting the slide. The end plate portion34ahas a curved bottom34eopposite the upper slide mounting surface34d. The curved bottom34eis machined to match the bottom circular curvature18aof the recessed compartment18.

Returning toFIG. 10, it can be seen that the base16is designed to provide the desired light weight and rigidity to the linear drive mechanism12. Thus, the base16is manufactured by extrusion of a light-weight, but rigid material, such as aluminum, and includes internal integral thin wall stiffeners in both normal and inclined directions. Formed centrally in the base is a circular stiffener forming the curved-bottom compartment18. External stiffeners form the outer periphery of the base, including the back surface80having the mounting holes82, and further define the access pockets84described above. The external stiffeners further include threaded mounting holes62at end faces thereof for mounting the end cap at one end and the motor at the opposite end.

By providing multiple mounting surfaces, the universal linear drive mechanisms of the present invention can be configured in many different ways. One of the unique ways the linear drive mechanisms may be configured is by an end-to-end connection. Specifically,FIG. 12shows how the second mounting surface2provided by the end cap86can be utilized to mount one linear drive mechanism to another end-to-end. As described above, the base16of each linear drive mechanism is provided with a recessed access pocket84, which allows for insertion of a bolt96through a mounting hole88of the end cap86of one drive mechanism for threaded engagement with a nut (not shown) residing in the access pocket84of the base of the other drive mechanism.

In an alternative embodiment, the motor24of each drive mechanism can be provided with a flange98that allows for motor-to-motor connection between two drive mechanisms12a1,12a2, as shown inFIG. 13.

In addition to end-to-end connections, the second mounting surface2provided on the end cap86, as shown inFIG. 12, or on the motor24, as shown inFIG. 13, further allows for direct perpendicular mounting of linear drive mechanisms without the need for additional angle brackets or mounting hardware between the stages themselves. This permits true orthogonal mounting of linear drive mechanisms for three directions (X-Y-Z directions) of movement for the workpiece manipulator with respect to the robot arm.

For example,FIGS. 14, 15aand15bshow a configuration of twenty-four (24) linear drive mechanisms12connected in triplets to form an end of arm tool100carrying workpiece manipulators in the form of four fingers102and four clamps104. The tool100shown inFIGS. 14, 15aand15bis made by first connecting the bases of eight linear drive mechanisms12a1,12a2,12a3,12a4,12a5,12a6,12a7and12a8together to form a rigid frame106. Preferably, two linear drive mechanisms are connected end-to-end via their end caps to form four pairs. The back face of each base of a connected pair is then attached to a back face of a base of another connected pair so that a rigid square frame106is formed. The frame106thus formed is directly connected to an end of a robot arm108, as shown inFIGS. 15aand15b.

As can be seen in the drawings, the slides of two opposite pairs of connected drive mechanisms forming the frame106face in one direction and the slides of the other two opposite pairs of the frame face in the other direction. Also, the slides of two opposite pairs of connected drive mechanisms travel back and forth in a first direction (X-direction), while the slides of the other two opposite pairs travel in a direction perpendicular to the first direction (Y-direction).

Attached to each slide of the drive mechanisms12a1,12a2,12a3,12a4,12a5,12a6,12a7and12a8forming the base frame106is a second level drive mechanism12b1,12b2,12b3,12b4,12b5,12b6,12b7and12b8. In a preferred embodiment, the slides of the second level drive mechanisms12b1,12b2,12b3,12b4,12b5,12b6,12b7and12b8are respectively connected directly to the slides of the frame drive mechanisms12a1,12a2,12a3,12a4,12a5,12a6,12a7and12a8. Each second level drive mechanism12b1,12b2,12b3,12b4,12b5,12b6,12b7and12b8has a slide that travels in a direction perpendicular to the direction of travel of the slide to which it is attached.

Attached to each end cap of the second level of drive mechanisms12b1,12b2,12b3,12b4,12b5,12b6,12b7and12b8is a slide of a respective third level drive mechanism12c1,12c2,12c3,12c4,12c5,12c6,12c7and12c8. Accordingly, the third level drive mechanisms12c1,12c2,12c3,12c4,12c5,12c6,12c7and12c8travel in a third direction (Z-direction) perpendicular to the first direction (X-direction) and second direction (Y-direction).

Attached to the end cap86of each third level drive mechanism is one of a finger102or a clamp104. As a result of such assembly, each finger102and each clamp104is provided with three directions of travel (X, Y and Z directions). This can be seen inFIG. 15a, showing all of the linear drive mechanisms in their fully extended state, andFIG. 15b, showing all of the drive mechanisms in their retracted state.

The linear drive mechanisms of the present invention can be assembled in various ways. For exampleFIG. 16shows a configuration of an end of arm robot tool100awherein one or more directions of travel of the pins102and/or clamps104are not perpendicular to each other. This can be achieved by providing inclined mounting surfaces108to one or more slides, as desired.

An alternative embodiment for forming the frame106ais also shown inFIG. 16. In this embodiment, two pairs of end-to-end connected linear drive mechanisms are provided, as described above. However, the linear drives of the other two pairs of linear drive mechanisms are connected together via the back surfaces of their respective bases. Also, the end caps provided at the opposite ends of this pair of linear drive mechanisms is attached to a respective back surface of the end-to-end connected linear drive mechanisms.

Thus, as shown inFIG. 17, the present invention provides a system constructed entirely as a frame structure106made of only one type of a small “all-in-one” positioning stage. The frame structure106is attached directly to a robot arm110, without the need for any end of robot arm structures, or stiffening brackets.

Each linear drive mechanism has several mounting surfaces, all of which are capable to interconnect by sets of access and mounting holes, which allow the linear drive mechanism itself to be used as both a structural element, supporting multiple XYZ stages in flat, upright or tilted orientations, as well as to operate as an XYZ positioning system, for positioning process tools. Each XYZ stage may carry a tool, such as a registration pin or a clamp, depending on the specific applications.

FIG. 18shows another alternative embodiment of a frame structure106bassembled from only four first-level “base” or “frame” linear drive mechanisms12a1,12a2,12a3and12a4. In this embodiment, the bases of four linear drive mechanisms are connected perpendicularly to each other to form a rigid square frame106b. Specifically, the end cap of each base is connected to one of the outer bottom mounting surfaces of another base so that a rigid square frame106bis formed. The frame106bthus formed is directly connected to an end of a robot arm108.

Further connection of second-level linear drive mechanisms to the frame106b, and third-level linear drive mechanisms to the second-level linear drive mechanisms, as described above will result in a small universal iEOAT consisting of a base of 4 stages with a total of twelve XYZ stages supporting four tools104. It can be appreciated thatFIG. 18shows only one of thousands possible configurations with the same twelve stages without the use of any brackets.

FIG. 18further shows collision protection devices116provided between the base mounting surfaces of connected linear drive mechanisms. As also shown in further detail inFIGS. 19aand 19b, the collision protection device116includes two spring preloaded plates118a,118b, which can be mounted any where between any two stages in their XYZ configuration and serve to absorb shock by accidental robot collision without damaging the stage.

The plates118aand118bare adapted for mounting to a respective mounting surface of a linear drive mechanism. The plates118aand118bare also kinematically coupled to one another via flexing elements120, such as springs, having a sufficient resiliency so as to create compliance for impact absorption and some lateral and angular displacement between the plates.

The crash protection device116may be an optional part of the universal iEOAT base frame connecting between some of the base stages (at least one per system), or it may be mounted as part of any XYZ stage at a convenient location. The flexing elements120are designed to collapse above the maximum expected process load, but less than the yield point of the stages. A small deflection at the base of the universal iEOAT will allow a much larger deflection at the outer distance, where the accidental crash may most likely hit an exposed stage.

The end of arm robot tool of the present invention can be used in many applications, and can be customized to perform many functions.FIG. 20, for example shows a configuration which uses the same universal iEOAT, both as a part handler100L (on the left) and a Geo platform100R (on the right). Each universal iEOATs100L,100R are carried by a respective robot110L,110R. As shown, the robot on the right110R picks a main car body part112with the universal iEOAT100R via multiple pins and clamps, and positions the part in a given orientation in space, which was taught to the robot110L.

The robot110L on the left picks up, with the same universal iEOAT100L, two independent stiffening parts114to be welded to the main part112. The robot110L on the left inserts the two locating holes of the small stiffener part into the two exposed pins on the main part, while the second stiffener is retracted. A welding robot (not shown) then welds the smaller stiffener to the main part. After welding the pins of the smaller part, the pins holding the smaller part retract and the same process repeats for the second stiffener.

After both stiffeners are welded, the main robot1108on the right unloads the assembled part and loads a new part112. The handling robot on the left110L returns to the loading station and picks up two new parts114.

The advantages provided by this application include: 1) Eliminates the need for a floor mounted geometric frame therefore saving cost and floor space; 2) The universal iEOAT can handle several parts on one round trip, therefore saving time of the handling robot going back and forth to pick individual parts; 3) Uses the same universal iEOAT for both main part support (acting as the geo frame) and for the part handling, therefore, saving cost of customization of part grippers and geo frames, with one standard iEOAT system; 4) The same robot can change roles servicing different parts on its 4 sides, (e.g., acting as a part handler on the left and as a Geo stand on the right), therefore, giving flexibility of plant automation layout and saving cost of robots and tooling; 5) The two robots can rotate the part 360 degrees and present it to a smaller welding robot and saving the cost of a larger welding robot.

In another aspect of the present invention, a method for assembling multiple linear drive mechanisms to perform a specified function is provided. The method is utilized for constructing a reconfigurable universal multi-axes intelligent end of arm tool (iEOAT), which is particularly adapted for high productivity of automotive manufacturing processes. This method is preferably implemented with an interactive online software program referred to herein as “the softool” and/or “the configurator.” Both software programs are intended to assist the process engineer in selecting the optimal configuration for the iEOAT, through a quick interactive process

The method for assembling multiple linear drive mechanisms according to the present invention has several objectives. First, the configuration parameters must be defined. This involves defining the desired location of the tools of each work piece, then calculating the required travel in the X, Y, and Z directions for all of the XYZ stages of the present invention. This further involves defining the teach point location of the robot that carries the iEOAT. Once the travel of the XYZ for each tool is determined, it is desired to determine the best configuration for mounting and support surfaces of each stage such that deformations under load are minimized and the precision is maximized.

More specifically, referring to the flow chart shown inFIG. 21, the method according to the present invention generally involves two phases. In the first phase (“softool phase”), the stage travels for each tool (pin or clamp) are selected using an iterative optimization process. In the second phase (“configurator phase”), the selected stage travel of each tool is optimized in an iterative process for their mounting configurations.

The first phase begins with the step200of determining locations for all contact points of tools for all of the workpieces to be manipulated by the tool. This information can be provided by a plant engineer as XYZ coordinates referenced to a global coordinate system based on the plant environment. The coordinates include contact points for clamps and/or hole centers for locating pins. These coordinates define the location of the workpiece to be picked-up.

In step201, these coordinates are input into fields of a computer work screen, as shown inFIG. 22A. As can be seen inFIG. 22A, a computer software program generates a screen that includes fields that can be populated with the respective global coordinate for each body part model and each tool for each model

In step202, Softool provides an output of the required XYZ travel of each tool in the input. This will typically include the required travel of the tool in the XYZ direction for each workpiece (e.g. body part style). In step203, the center position of the tool within its travel range and the teach points of the robot end of arm (EOA) interface to the end of arm tool (EOAT), etc. A sample computer screen page for inputting such information is shown inFIG. 22B.

As can be seen inFIG. 22B, a computer software program generates a chart which shows stage travel and location, as well as robot positions for single teach points and multiple teach points.FIG. 22Crepresents a pictorial view of information in FIG.20B including a drawing with the XY foot print of each pin, pin center location, and robot teach point for a single teach point and for multiple teach point options. Step204of the process involves a review of the drawing and a decision if improvement is required. Such graphical representation can assist the designer to visualize the location and movement for each stage.

If changes in stage sizes are required, an “optimizer” sub-routine is run by the computer software program in step205. The optimizer sub-routine can offer the designer the option to insert an offset to the robot. Such an offset requires a new teach point, but will make the required travel of some stages less and some stages higher. This feature is helpful in case there is a limitation of available all in one stage travel.

After a choice is made for one tool, a repeat stage selection is done for a new tool with, possibly, a new XYZ stage length.

Phase 2 (“configurator phase”) begins with step206. The output information from the softool then becomes an input to the configurator, which runs at step206with the following steps. The XYZ travel of each tool, as found in the Softool, is entered in step207to the Configurator work screen, as shown inFIG. 24A. Then, the output of the Configurator, as shown inFIG. 24B, is reviewed in step208. In step209, the compatibility of the defection of the stage under load is checked against maximum recommended deflection. In step210, the mounting configuration may change in an iterative process of searching for the stiffest mounting configuration, which is then selected in step211. The process then repeats for the XYZ configuration of the next tool, until all configurations are done.

FIG. 23shows an example of various mounting configurations of 4 tools including a set of metrics that may be used to further rate each configuration with respect to their specific merits. As can be seen inFIG. 23, computer software programmed to carry out the method of the present invention will process the data input to generate visual representations of a number of stage configurations (i.e., numbers and arrangements of linear drive mechanism) that can perform the desired functions. The computer program further weights each possibility based on a number of criteria, which may include cost of the system, weight, stiffness, complexity, configuration time, number of parts, repeatability, durability, programming time, teaching time, EOAT design time, iEoat implementation time. These merits of value can then be displayed in a comparison chart, as shown inFIG. 23.

Thus, the method according to the present invention allows the designer to design a very stiff frame made of interconnected stages. Other stages can be mounted in hundreds of different configurations to best fit the application, all with minimal or no brackets or heavy supporting frames. The software tools provide the designer with a quick way of analyzing the best XYZ stage travel and mounting configuration to result in high stiffness and high precision of the iEOAT tools, such as pins and clamps. In addition, the entire structural frame may be reconfigured to serve a different class of body parts. The entire structure is extremely stiff since it employs several stages in carrying the process loads in different directions. Therefore, weak spots of the small stage, such as roll stiffness, are not being expressed when working in parallel with other stages, which resist the load in direction of higher stiffness.

The entire structure is light-weight, which is ideal for robot handling since only the stages participate in the structure without any additional mounting frames or stiffening brackets.

While various embodiments of the present invention are specifically illustrated and/or described herein, it will be appreciated that modifications and variations of the present invention may be effected by those skilled in the art without departing from the spirit and intended scope of the invention.