Control system and equipment configuration for a modular product assembly platform

A modular product assembly platform which includes a multiple number of industrial robots or other similar assembly devices. The product assembly platform also includes a programmable controller system housed in a logic control cabinet, a vision control system housed in a vision control cabinet and a set of robot controllers which operate together to control the robots or assembly devices for performing product assembly tasks. The layout and configuration of the platform and the control equipment provide for convenience and flexibility in configuring and reconfiguring the assembly platform for different assembly procedures associated with different products.

BACKGROUND OF THE INVENTION 
The present invention relates to industrial automation equipment and more 
particularly relates to modular platform units for performing product 
assembly procedures. 
In the past, product assembly processes have usually been performed by 
custom designed assembly machinery which have been dedicated to particular 
assembly tasks. In accordance with this conventional approach the design 
and construction of automated assembly lines required enormous engineering 
expenditures and involved high risks to prove functional equipment 
compliance. Furthermore, once such assembly lines were constructed, they 
were completed specialized to the limited applications for which they were 
built and were not reusable for the assembly of different products. The 
assembly units making up the assembly line could be recovered in the event 
manufacturing operations were discontinued, however, in most cases, 
extensive redesign and reconstruction was necessary to adapt the equipment 
for use in assembling new products. 
It is therefore an object of the present invention to provide a control 
system and configuration for a modular product assembly platform that 
allows for the platform to have flexibility and reusability 
characteristics so that the platform can be adapted for assembling 
alternate or different products with a minimum of cost and effort. 
It is a further object of the present invention to provide a control system 
and configuration for a modular product assembly platform which allows for 
the efficient and effective use of assembly robots and machine vision 
equipment. 
It is yet another object of the present invention to provide a control 
system and configuration for a modular product assembly platform wherein 
the system is generically programmable and is interfaced with adaptable 
robotic configurations. 
It is a yet further object of the present invention to provide a control 
system and configuration for a modular product assembly platform which 
facilitates factory automation projects, allows platforms to be brought 
together to perform different types of assembly procedures and optimizes 
production efficiency in terms of equipment utilization, control and cycle 
time requirements. 
SUMMARY OF THE INVENTION 
The present invention constitutes a control system and equipment 
configuration for a modular product assembly platform which includes a 
multiple number of industrial robots or specialized product assembly 
machines. The robots are detachably mounted on a specially designed 
platform deck and include moveable robot arms on which video cameras may 
be mounted as part of a machine vision system and tooling adapted for 
performing product assembly tasks. Robot controllers for separately 
directing the operation of the individual robots are mounted underneath 
the deck. A general purpose programmable controller for controlling the 
assembly process across the entire platform is mounted in a cabinet at one 
end of platform. A user configurable machine vision system is mounted in a 
cabinet at the other opposite end of the platform for use in identifying 
and locating parts in coordination with the operation of the robots. The 
product assembly platform also includes a conveyance system for 
transporting parts and products under assembly across the deck past the 
robots. The robot controllers are configured for controlling the 
"geographic" positioning of the moveable arms of the robots. The vision 
system provides information for recognition of parts and the proper 
alignment and positioning of parts and robot arms. The programmable 
controller system provides overall control and coordination for the 
robots, vision system, robot controllers, assembly tooling on the robot 
arms and the conveyance system. 
In operation, either stationary or robot arm mounted video cameras are 
positioned so that the parts to be worked on will be located in their 
field of view. Either the programmable controller or one of the robot 
controllers commands the vision system to capture images (take a picture) 
of the parts. The stored image attributes are analyzed by the vision 
system per preprogrammed instructions. For "recognition" type applications 
such as presence sensing and gauging, the information is provided to the 
programmable controller for subsequent operation. For robot "guidance" 
type applications, the coordinate location and rotary position of the part 
is determined by the vision system in conjunction with the robot 
controller's calibration function. The information is used by the robot 
controller to position the robot arm mounted tooling to perform the 
required task. When the tool is in position, the programmable controller 
signals the tooling to execute the product assembly task associated with 
each assembly process step. The programmable controller signals the robot 
controllers and the vision equipment to proceed from one assembly process 
step to another in coordination with the operation of the conveyance 
system as parts proceed across the platform in accordance with the desired 
assembly procedure.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIGS. 1, 2A and 2B, a modular product assembly platform 10 
is shown as including a frame 12 having a raised deck 14 on which a set of 
three industrial product assembly robots 16 are removably mounted. The 
platform 10 also includes a conveyor 20 for transporting parts 25 on trays 
17 from the near end 11 of the deck 14 to the far end 13 of the deck 14 
past the robots 16. The robots 16 comprise conventional industrial robots 
(one of which is a cartesian robot and two of which are SCARA robots) 
having movable arms 22 and specialized tools 18 such as grippers, 
screwdrivers, welding appliances and the like attached to the outer ends 
of the movable arms 22 for performing product assembly tasks. Support 
stands 21 are adapted for storing alternative robot tools or tooling 18 
which may be interchangeably used by the robots 16. Video cameras 24 are 
mounted either on the arms 22 of the robots 16 or on stationary supports 
for recognition and location detection of the parts 25 on the trays 17 
being worked on by the robots 16. 
The arms 22 of the robots 16 are individually controlled by three robot 
controllers 26 installed in bays 28 underneath the deck 14 and by a 
programmable controller system 90 (see FIG. 4) mounted within a logic 
control cabinet 30 at the far end 13 of the platform 10. The robot 
controllers 26 control positioning of the movable arms 22 on the robots 16 
while the programmable controller 90 regulates the assembly process steps 
to be performed and, in particular, controls the operation of the tooling 
18 in coordination with the selection of the movement steps to be 
performed by the robot arms 22. The video cameras 24 are controlled by a 
vision control system 110 (see FIG. 5) mounted within a vision control 
cabinet 34 on the near end 11 of the platform 10 which in turn operates 
under direction of the programmable controller system 90 at the far end 13 
of the platform 10 in the cabinet 30. The control console 40 provides an 
operator interface for allowing operator control over the machinery on the 
platform 10 while the power control cabinet 42 houses various electrical 
power distribution and control elements subject to regulation by the 
operator through the use of the control console 40. The control console 40 
includes a set of power control pushbuttons 41 for manually turning 
platform machinery on and off, an input panel 43 for manual sequencing of 
platform machinery through their control programs and a numerical keypad 
and corresponding LCD display 45 for entry of control parameters and the 
like. A wiring and communications conduit 50 comprised of wiring and 
control cabinets extends around the periphery of the raised deck 14 for 
housing power distribution, control and communication lines as well as 
small size relays and terminal strips mounted on DIN rails. The conduit 50 
includes the cabinets 42, 64, 30, 62, 34 and 66 which form a continuous 
ring encircling the entire platform deck 14. A data display unit 52 is 
mounted above the console 40 for displaying operating information and 
especially platform operating fault notices in response to signals from 
the programmable controller system 90. The superstructure 46 may be used 
to house pneumatic lines for providing pneumatic power along the edge of 
the deck 14 from alongside the conduit 50. 
In operation, the platform 10 provides for parts 25 to be transported past 
the robots 16 on the conveyor 20. The robots 16 may perform various 
assembly tasks on the parts 25 as they pass by on the conveyor 20 in 
accordance with programs executed by the programmable controller system 90 
in the cabinet 30 as selected by the operator through the use of the 
control console 40. The vision control system 110 within the cabinet 34 
provides parts recognition and robot arm guidance information to the robot 
controllers 26 and the programmable controller system 90 in the cabinet 
30. The configuration of the platform 10 allows for a great deal of 
flexibility in programming and reprogramming the overall system 
represented by the platform 10 for accomplishing different sets of 
assembly tasks on different types of products. 
Referring now to FIG. 3, the power control cabinet 42 comprises a sheet 
metal enclosure which can be accessed through two outward opening doors. 
The cabinet 42 houses a main disconnect switch 79, a motor drive unit 80 
for the conveyor 20, two control circuit transformers 82, a DC power 
supply 83, a set of terminal strips 84 for making electrical control and 
power distribution connections, a set of control relays 85 and a set of 
overload relays 87. The transformers 82 provide AC power to the electrical 
machinery mounted on the platform 10 such as the robots 16. The motor 
drive 80 controls the operation of the conveyor 20. The terminal strips 84 
enable the motor drive 80, transformers 82, relays 85 and 87 and power 
supply 83 to be conveniently interconnected with the console 40 and the 
electrical machinery of the platform 10. The cabinet 42 is connected to 
the cabinets 64 and 62 at openings 63 and 65 for enabling the passage of 
power, control and communications lines. 
Referring now to FIG. 4, the logic control cabinet 30 comprises a sheet 
metal enclosure which can be accessed through two outward opening doors. 
The cabinet 30 houses a conventional programmable controller system 90 
having a chassis 92 in which power supply, logic processor, and I/O 
modules are mounted. In the present case the programmable controller 
system 90 comprises a power supply 89, a logic processor module 91 and 
sixteen I/O modules 93. The system 90 allows control instructions in the 
form of an industrial control program such as ladder logic programs 
resident in the memory of the logic processor module 91 to be executed to 
examine the state of selected inputs at modules 93 and thereafter control 
the state of selected outputs at modules 93 depending upon the state of 
one or more of the inputs. Large numbers of inputs may be examined by the 
system 90 at the same time as it controls large numbers of outputs. The 
wiring by which the system 90 is connected to sensing and control output 
devices (such as tooling 18) is generally directed through the casing 95 
within which multiple terminal strips are mounted for establishing the 
required electrical interconnections. The communication cables 97a, 97b 
and 97c connect communication ports on the processor module 91 to the 
remote I/O rack 100 (FIG. 5), the vision system 110 (FIG. 5), control 
console 40 and data display unit 52 via conventional packet network 
communication links. The power, control and communication lines for the 
system 90 pass through conduits 62 and 66 to the sensing devices, 
electrical machinery and the control equipment of the platform 10 which 
work under the control of the programmable controller system 90. 
Referring now to FIG. 5, the vision control cabinet 34 comprises a sheet 
metal enclosure which can be accessed through two outward opening doors. 
The cabinet 34 houses a remote I/O rack 100 containing a power supply 
module 102, six remote I/O modules 104 and a communications adapter module 
106. The communications adapter module 106 links the remote I/O rack 100 
to the programmable controller system 90 by way of the cable 97b connected 
to a communications port on processor module 91 in the chassis 92. The 
remote I/O rack 100 allows for input and output services related to the 
control program of the system 90 to be resident at the near end 11 of the 
platform 10 within the cabinet 34. The cabinet 34 also contains a 
user-configurable vision control system 110 which is adapted for receiving 
video input from the video cameras 24. The vision control system 110 
includes a power supply 112 and a vision control module 114 having the 
capability of working with multiple video cameras (although multiple 
vision control modules 114 could be used). The vision control module 114 
is separately connected by the video signal cables 117 to each of the 
video cameras 24 on the robots 16. The vision module 114 is also connected 
to the robot controllers 26 and is connected to the programmable 
controller system 90 via the communications cable 97a which is connected 
to one of its communications ports for establishing a communications 
network link with the controller system 90. The vision system 110 may also 
communicate with the controller system 90 by way of the I/O rack 100. The 
wiring by which the systems 100 and 110 are connected to the sensing and 
control output devices is generally directed through the casing 105 within 
which multiple terminal strips are mounted for establishing the required 
electrical interconnections. The power, control and communications lines 
for the systems 100 and 110 pass through the cabinets 64 and 66 of the 
conduit 50. 
Referring now to FIG. 6, the cabinet 66 of the conduit 50 is typical of the 
cabinets 62, 64 and 66 and comprises a sheet metal enclosure which can be 
accessed by unscrewing and removing its outer cover. The cabinet 66 houses 
multiple sets of wires 130 for distributing power to the electrical 
machinery on the platform and for conducting control and communications 
signals between the electrical machinery on the deck 14 and the 
programmable controller system 90, the I/O rack 100, the robot controllers 
26 and the vision system 110. Terminal strips 132 and control relays 133 
are mounted on a DIN rail 134 within the cabinet 66. The terminal strips 
132 allow for easy interconnection of the wiring within the cabinet 66 
while the relays 133 provide for control in the immediate vicinity of 
platform machinery. The cabinets 62, 64 and 66 are characterized by access 
ports opening onto the deck 14 for passage of wiring to the electrical 
machinery and control equipment on and under the deck 14. The conduit 50 
provides a highly useful function in allowing complete electrical 
interconnection all around the periphery of the deck 14 of the platform 10 
thereby facilitating the efficient interconnection of the machinery and 
control equipment of the platform 10 and enabling convenient configuration 
and reconfiguration of the platform 10 for different product assembly 
applications. 
Referring now to FIG. 7, the pedestals 140 for mounting the robots 16 are 
mounted onto the deck 14 using rails 142. The rails 142 run lengthwise 
across the deck 14 parallel with the conveyor 20. Each of the rails 142 
has a special cross-section in the form of a modified T shape including a 
downward facing incline 144 on one lateral side and which intersects the 
deck 14 at an acute angle an overhanging ledge 146 on its other lateral 
side which intersects the deck 14 at a right angle. Each pedestal 140 
mounts onto two rails 142 using two recessed tracks 150 and 152 running 
parallel across its base plate 154 and two mounting blocks 156 and 158 
which can be drawn upward toward the plate 154 by bolts 160 and 162. The 
mounting block 156 has the shape of an inverted T for mating with a ledge 
146 while the mounting block 158 has an incline 155 along one of its faces 
for mating with an incline 144. To provide vertical stability and 
alignment, the bolt 160 draws up the block 156 against the bottom 164 of 
the ledge 146 and the track 150 so that the rail, and more particularly, 
the ledge 146 is trapped between the block 156 and the plate 154. To 
provide horizontal alignment and stability, the bolt 162 draws up the 
block 158 against the incline 144 in order to push the outer lateral edge 
166 of the ledge 146 of the rail 142 against the outer wall 168 of the 
track 152. Together the rails 142, tracks 150 and 152 and blocks 156 and 
158 provide a very stable and accurate mounting and alignment system for 
the pedestals 140 and the robots 16. 
Referring now to FIG. 8, the electrical control system of the platform 10 
includes the programmable logic controller system 90, the robot 
controllers 26 and the vision control system 110. The programmable logic 
controller system 90 is responsible for overall coordination and control 
of the electrical machinery on the platform 10. The robot controllers 26 
direct the actual mechanics for "geographic" positioning of the robot arms 
22 of the robots 16. The vision control system 110 receives video input 
from the cameras 24 associated with the robots 16 and in response performs 
various recognition and robot guidance functions with respect to which it 
may transmit data to the controller system 90 and/or robot controllers 26. 
When the robot arms 22 and parts 25 are in proper alignment the 
programmable logic controller system 90 actuates the tooling 18 to perform 
the appropriate assembly tasks. 
Referring now to FIGS. 9, 10A, 10B and 10C, the flow of control signals 
associated with a particular robot 16 in a typical control system as shown 
in FIG. 9 takes place in a series of sequential control steps as shown in 
FIGS. 10A, 10B and 10C. In step 200 the programmable controller system 90 
signals the robot controller 26 that the next product assembly step should 
be undertaken. In response the robot controller 26 transmits control 
signals to the robot 16 for directing movements of the robot arm 22 and 
the arm 22 is repositioned in accordance with step 202 so that the camera 
24 (mounted on arm 22) is in position to take a picture of a part. As 
indicated in step 204 different vision/control routines are followed for 
guidance or recognition applications (other types of vision/control 
routines could also be followed). If a robot guidance application is 
involved both the controller system 90 and vision system 110 "jointly" 
regulates operations in accordance with the guidance routine of FIG. 10B 
If a recognition application such as presence sensing or gauging is 
involved the controller system 90 regulates operations in accordance with 
the recognition routine of FIG. 10C. 
Referring now to FIG. 10B, in a guidance application, the robot controller 
26 signals the vision system 110 as per step 220 that the video camera 24 
is in position to spot a part to be worked on in accordance with its most 
recent positioning of the robot arm 22. Thereafter, the vision system 110 
controls the camera 24 to take a "picture" of the location where the part 
is positioned in accordance with step 221. After the picture is taken and 
the attributes of the image are analyzed by the vision system 110 per 
preprogrammed instructions in step 222, the vision system 110 transmits 
coordinates to the robot controller 26 in step 223 indicating the location 
and rotation of the part with respect to its own vision coordinate frame 
of reference. The robot controller 26 then transforms the vision 
coordinates into its own robot coordinate frame of reference (per a 
preprogrammed initial calibration procedure) and repositions the robot arm 
22 to the desired position for further operations as per step 224 in 
accordance with the coordinate information from the vision system 110. 
Once the robot arm 22 has been moved into position the robot controller 26 
signals the controller system 90 in step 225 that the robot arm 22 is now 
in position for the tooling operation to be performed. 
Referring now to FIG. 10C, in a recognition application, the robot 
controller 26 signals the controller system 90 as per step 230 that the 
video camera 24 is in position to spot a part to be recognized in 
accordance with its most recent positioning of the robot arm 22. As 
indicated in step 231 the controller system 90 then signals the vision 
system 110 that the camera 24 is in position and, thereafter, the vision 
system 110 controls the camera 24 to take a picture of the location where 
the part may be located in accordance with step 232. After the picture is 
taken and the attributes of the image are analyzed by the vision system 
110 per preprogrammed instructions in step 233, the vision system 110 
transmitted either a "Go" or "No Go" signal to the controller system 90 
based on its analysis of the presence or characteristics of the part. 
Referring back to FIG. 10A, following the execution of the guidance routine 
of step 206, the controller system 90 transmits appropriate control 
signals for actuating the tooling 18 to perform the assembly task 
associated with the current assembly process step as indicated in step 
212. After a short delay for the tooling to accomplish its task, the 
controller system 90 proceeds to the final step 214. On the other hand, 
following the execution of the recognition routine of step 208, the 
controller system 90 responds to the "Go" or "No Go" signal from the 
vision system 110 in accordance with step 210 by either actuating the 
tooling 18 pursuant to step 212 in the case of a "Go" signal or proceeding 
to step 214 in the case of a No Go signal. In step 214, the controller 
system 90 queries whether the last step in the overall assembly procedure 
has now been executed and either halts operations if the last step has 
been executed or jumps back to step 200 if the last step has not been 
executed. 
Referring now to FIG. 11, multiple product assembly platforms 10a-f having 
different configurations of robots 16 may be used in combination to 
perform complicated assembly procedures comprising multiple assembly 
steps. In particular, the product assembly platforms 10a and 10e and 10f 
feed parts to the main assembly line consisting of platforms 10b, 10c and 
10d where the parts are incorporated into the final product at platforms 
10c and 10d, respectively. A network controller 250 is in communication 
with the programmable controller systems on platforms 10b-f and conveyance 
device 256 for coordinating platform operations and regulating the 
operation of the conveyance device 256 for controlling the transfer of 
parts between platforms. The modular nature of the platforms 10a-f allows 
them to be used as building blocks in assembly systems for factories. The 
platforms 10a-f have a great advantage in that they can be easily 
reprogrammed or reconfigured in new arrangements for the assembly of 
different products without rebuilding and retooling of the entire factory 
floor on which the platforms are installed. 
While particular embodiments of the present invention have been shown and 
described, it should be clear that changes and modifications may be made 
to such embodiments without departing from the true scope and spirit of 
the invention. It is intended that the appended claims cover all such 
changes and modifications.