Assembly line fluid filling system and method

Abstract

A method for fueling an automotive vehicle 26 on a conveyer line 28 is provided. The conveyer line 28 moves generally along a first axis 170 and the method utilizes a robotic arm 34 with an end effector 54 for fueling a fuel stem 90 of the vehicle 26 . The method includes determining a first position of the fuel stem 90 along the first axis 170 . The method further includes moving the robotic arm 34 to position the end effector 54 proximate to the first position. The method further includes determining a three-dimensional position of the fuel stem 90 utilizing a vision system 164 . The method further includes moving the end effector 54 proximate to the three-dimensional position to enable the end effector 54 to mate with the fuel stem 90 and moving said robotic arm 34 relative to said first axis 170 at a speed substantially equal to a speed of said conveyer line 28 . Finally, the method includes fueling the fuel stem 90 with the end effector 54.

We claim:  
     
         1 . A method for assembly line fluid fill of a container in a vehicle moving along the assembly line comprising the steps of: 
 (A) determining a position of an inlet of the container using a machine vision system while the vehicle is moving along the assembly line;    (B) positioning a fluid fill delivery outlet to the inlet using a robot; and    (C) filling the container via the outlet while the vehicle continues to move.    
     
     
         2 . The method of  claim 1  further comprising the step of moving the delivery outlet in substantial synchronism with said inlet.  
     
     
         3 . The method of  claim 2  wherein said moving step includes the substep of updating the position of the container inlet.  
     
     
         4 . A method for fueling an automotive vehicle on a conveyer line, said conveyer line moving generally along a first axis, said method utilizing a robotic arm with an end effector for fueling a fuel stem of said vehicle, said robotic arm having a workspace within which the fuel stem must lie in order to be fueled, said method comprising: 
 determining a first position of said fuel stem along said first axis;    moving said robotic arm to position said end effector proximate to said first position such that said fuel stem lies within said workspace;    determining a three-dimensional position of said fuel stem utilizing a vision system;    moving said end effector proximate to said three-dimensional position to enable said end effector to mate with said fuel stem and moving said robotic arm relative to said first axis at a speed substantially equal to a speed of said conveyer line; and,    fueling said fuel stem with said end effector.    
     
     
         5 . The method of  claim 4  wherein said step of determining a first position of said fuel stem includes: 
 storing a first encoder position value indicative of a position of said vehicle when said vehicle passes a predetermined position on said conveyer line;  
 storing a second encoder position value indicative of a position of said vehicle after said vehicle has passed said predetermined position; and,  
 calculating said first position of said fuel stem responsive to said first and second encoder position values.  
 
     
     
         6 . The method of  claim 5  wherein the step of storing the second position includes detecting the presence of the vehicle.  
     
     
         7 . The method of  claim 6  wherein said step of storing said second position value includes: 
 monitoring a light beam being projected across said conveyer line; and,  
 determining when said light beam is interrupted by said vehicle.  
 
     
     
         8 . The method of  claim 4  wherein said vision system includes first and second cameras and said step of determining said three-dimensional position of said fuel stem includes: 
 generating a first digital image of said workspace including said fuel stem utilizing said first camera;  
 simultaneously generating a second digital image of said workspace including said fuel stem utilizing said second camera; and,  
 calculating said three-dimensional position of said fuel stem with respect to a predetermined coordinate system responsive to said first and second digital images.  
 
     
     
         9 . The method of  claim 4  wherein said three-dimensional position is a center point of said fuel stem with respect to a predetermined coordinate system, said center point lying on a plane defined by the sealing surface (typically an outer edge) of said fuel stem.  
     
     
         10 . The method of  claim 4  wherein said step of moving said end effector to said second position includes the steps of: 
 monitoring said speed of said conveyer line while said end effector is mated with said fuel stem; and  
 matching the speed and position of the end effector with that of the fuel stem.  
 
     
     
         11 . The method of  claim 4  wherein said step of fueling further includes: 
 monitoring a force exerted on said end effector by said fuel stem; and  
 adjusting said position of said end effector responsive to said force.  
 
     
     
         12 . The method of  claim 4  wherein said step of fueling said fuel stem with said end effector includes: 
 opening a fuel valve in said end effector to supply fuel to said fuel stem; and,  
 closing said fuel valve after a predetermined amount of fuel is pumped into said fuel stem.  
 
     
     
         13 . The method of  claim 4  further including retracting said end effector from said fuel stem after a predetermined amount of fuel is pumped into said fuel stem.  
     
     
         14 . The method of  claim 4  further including illuminating said fuel stem.  
     
     
         15 . A method for providing position data to a controller to enable a robotic arm controlled by said controller to move to a position of an object, said object lying within the workspace of said robotic arm, said method utilizing first and second cameras disposed at first and second coordinate systems, respectively, said method comprising: 
 generating a first digital image of said workspace including said object utilizing said first camera;    searching said first digital image with a first image template to determine a location in said first image where a first correlation score between that portion of said image being searched and said template is greater than a predetermined threshold;    simultaneously generating a second digital image of said workspace including said object utilizing said second camera;    searching said second digital image with a second image template to determine a location in said second image where a second correlation score between that portion of said image being searched and said template is greater than a predetermined threshold;    calculating a three-dimensional position of said object with respect to a predetermined coordinate system responsive to said first and second digital images when said first and second correlation scores are both greater than a threshold correlation score;    calculating a triangulation error of said position; and,    transferring position data indicative of said three-dimensional position to said controller when said triangulation error is less than a threshold error value.    
     
     
         16 . The method of  claim 15  wherein said object is a fuel stem and said three-dimensional position is a center point of said fuel stem.  
     
     
         17 . The method of  claim 15  wherein said step of calculating said three-dimensional position includes: 
 calculating a first direction vector from an origin of said first coordinate system responsive to said first digital image, said first vector pointing towards an estimated first center point of said object;  
 calculating a position of said first coordinate system and an orientation of said first direction vector relative to said predetermined coordinate system;  
 calculating a second direction vector from an origin of said second coordinate system responsive to said second digital image, said second direction vector pointing towards an estimated second center point of said object;  
 calculating a position of said second coordinate system and an orientation of said second direction vector relative to said predetermined coordinate system;  
 determining a first point along said first direction vector that is closest to said second direction vector;  
 determining a second point along said second direction vector that is closest to said first point; and,  
 calculating a midpoint between said first and second points to obtain said three-dimensional position of said object.  
 
     
     
         18 . The method of  claim 15  further including illuminating said object.  
     
     
         19 . The method of  claim 15  further including moving said robotic arm to said three-dimensional position.  
     
     
         20 . A fueling system for fueling an automotive vehicle on a conveyer line, said conveyer line moving generally along a first axis, comprising: 
 a gantry having a carriage configured to move generally parallel to said first axis;    a robotic arm attached to said carriage that moves with said carriage, said robotic arm having an end effector configured to mate with a fuel stem on said vehicle and to supply fuel to said fuel stem through a fuel hose;    a vision system including first and second cameras for iteratively determining a three-dimensional position of said fuel stem relative to a predetermined coordinate system;    a robot controller configured to command said carriage to move proximate said three-dimensional position and to move said end effector to said position to mate with said fuel stem, said robot controller being further configured to move said robotic arm relative to said first axis at a speed substantially equal to a speed of said conveyer line.    
     
     
         21 . The fueling system of  claim 20  further including a position encoder operatively connected to said conveyer line.  
     
     
         22 . The fueling system of  claim 20  further including a light sensor for detecting when said vehicle passes a predetermined location on said conveyer line.  
     
     
         23 . The fueling system of  claim 20  further including a light for illuminating said fuel stem.  
     
     
         24 . The fueling system of  claim 20  wherein said vision system further includes a vision controller and a frame grabber, said frame grabber retrieving digital images generated by said first and second cameras, said vision controller configured to calculate said three-dimensional position of said fuel stem responsive to said digital images.  
     
     
         25 . The fueling system of  claim 20  wherein the robotic controller includes means for positioning a joint of said robotic arm; 
 means for calculating a desired joint position;  
 means for automatically positioning a stop corresponding to said desired joint position using a low powered motor and a self-locking mechanism; and  
 means for driving said joint against said stop using a pneumatic actuator.  
 
     
     
         26 . The fueling system of  claim 20  comprising: 
 further including means for detecting loss of or damage to said fuel hose;  
 means for providing said fuel hose with a tip having a size configured to impair retraction through a boot of said end effector;  
 means for actuating said fuel hose using a pneumatic cylinder;  
 means for arranging a stroke of said pneumatic cylinder such that said stroke remains when said tip has bottomed in said boot of said end effector;  
 means for providing a first limit switch which energizes when said pneumatic cylinder has retracted to a first position corresponding to said hose tip being bottomed in said boot;  
 means for providing a second limit switch which energizes when said pneumatic cylinder is fully retracted to a second position beyond said first position; and  
 means for providing said robot controller with logic to sense that said fuel hose has been lost or damaged when said second limit switch is energized.  
 
     
     
         27 . A method for providing updated kinematic parameters to a controller to enable a robotic arm controlled by said controller to compensate for dimensionally unstable portions of said robotic arm, said method comprising the steps of: 
 providing one or more markers on an end effector of said robotic arm;    positioning the markers within a workspace of said robotic arm;    using a vision system associated with said robotic arm to determine respective three-dimensional locations of said markers; and    calculating updated kinematic parameters by comparing the determined locations of said markers returned by said vision system to respective expected locations of said markers.