WO2001053192A1

WO2001053192A1 - Method and apparatus for automatic opening and closing of a vehicle fuel door during robotic vehicle refueling

Info

Publication number: WO2001053192A1
Application number: PCT/US2000/032959
Authority: WO
Inventors: John W. Logan; Alex Kascoutas
Original assignee: Shell Oil Company
Priority date: 2000-01-19
Filing date: 2000-12-05
Publication date: 2001-07-26
Also published as: WO2001053192A9; AU2001219458A1

Abstract

A method and apparatus for automatic opening and closing a hinged vehicle fuel door during robotic vehicle refueling is disclosed. The robotic refueling system comprises a manipulator assembly with an end effector having two adjacent arms, one for opening/closing the fuel door (door arm) and another for refueling the vehicle fuel tank (refueling arm). The door arm holds the fuel door during the refueling operation via a vacuum cup located at the tip of the arm by suction with vacuum cup movement controlled by a linear vacuum cup actuator. After securing the fuel door via the vacuum cup, so as to avoid side loads on the door, the door arm swings the fuel door open from its initial door open angle to a pre-defined maximum door open angle in a series of incremental steps using precisely coordinated movements of the four actuators (yaw axis, door arm rotate, door arm swing and vacuum cup actuator). After filling the vehicle tank, the refueling nozzle is fully retracted and the door arm closes the fuel door in a series of incremental steps being the reverse of the door opening steps with software commands to the same four active joints.

Description

METHOD AND APPARATUS FOR AUTOMATIC

OPENING AND CLOSING OF A VEHICLE FUEL DOOR

DURING ROBOTIC VEHICLE REFUELING

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to robotic refueling systems and more particularly to a method for automatic opening and closing of a vehicle fuel door during robotic refueling of motor vehicles and apparatus for controlling the same.

Prior Art

A great deal of effort has been expended to develop a system for robotically refueling automotive vehicles. Such systems may include an overhead gantry which supports a carriage upon which a robot is supported for appropriate movement relative to the vehicle to position the robot adjacent the fuel door on the vehicle. Alternatively, the robotic system may be supported on an island adjacent the vehicle and then moved to a position adjacent the fuel door. As another alternative, the robotic system may be stowed underground and, after positioning of the vehicle, retrieved and moved to a point adjacent the fuel door. Irrespective of the position in which the robot is stored or the manner in which it is moved, all such robotic refueling systems require an appropriate mechanism to insert a hose assembly which includes a nozzle for delivery of fuel into the fuel tank of the vehicle. The fuel hose must be inserted through the vehicle fuel filler pipe and into a position internally of the vehicle fuel filler pipe such that the nozzle is appropriately positioned and so that fuel can easily flow from the nozzle into the vehicle fuel tank without obstruction.

Typically, the fuel hose assembly is extended from the robot arm in accordance with appropriate signals received from a control mechanism. After refueling, the fuel hose assembly is extracted from the fuel filler pipe, the fuel filler door is closed, and the robot is returned to its stowed position. The refueled vehicle may then leave the robotic refueling station. One form of robotic refueling apparatus is shown and described in the United

States Patent Nos. 5,609,190; 5,628,351 and 5,634,503, which are assigned to the assignee of the present application, the disclosures of which are incorporated herein by reference. As is therein shown, a robot is stored on an overhead carriage which in turn is supported for movement upon a gantry so that the robot may be positioned on either side of the vehicle in accordance with the position of the vehicle fuel door. After the robot is appropriately positioned, the fuel door is automatically opened by the robot and the fuel hose inserted into the fuel filler pipe on the vehicle so that fuel may be inserted into the vehicle fuel tank. After filling the vehicle fuel tank, the fuel hose assembly is extracted from the fuel filler pipe, retracted into the robot arm, and the robot is then appropriately stored on the carriage and returned to its stowed position on the gantry until it is reactivated for refueling another vehicle.

It is important to automating the fueling process that a robotic refueling apparatus accommodate a wide range of fuel doors having various placements, opening and closing geometries, motions, and orientations relative to a vehicle and an associated fuel filler tube. Typically, the door opening mechanism is provided by a vacuum cup supported by a telescoping robotic arm assembly. The vacuum cup must be extremely manipulable over a wide range of motions and positions to accommodate the greatest number of fuel filler door configurations and required opening and closing motions. Further, since some fuel doors are self-closing, it may be necessary to hold the door open until the refueling operations are concluded. Even in those situations wherein the fuel door is designed to stay open by itself, it may be difficult to recapture an open door so that it can be closed. Therefore, it is generally the practice to retain a hold on the fuel door once captured and opened until completion of the refueling operation including closing the door. Therefore to avoid interference with the robotic fueling apparatus, the door opening mechanism must be positional out of the way of the end effector refueling apparatus while maintaining a hold on the fuel filler door. This may require substantial repositioning of the door opening mechanism and require a wide range of motion at a distal end of the arm.

A fuel door opening and closing apparatus is disclosed in U.S. Patent 5,609,190 above referred to and incorporated herein by reference. As is therein shown, the mechanism utilized to open a hinged fuel door over a vehicle=s fuel inlet includes a pneumatic cylinder supporting a vacuum cup. The vacuum cup is supported on the end of a push tube that is extendable by providing an inner tube that extends out of or retracts into an outer tube while maintaining a sealing relationship therewith. A vacuum is provided to the vacuum cup through the center of the push tube. A yaw positioning cylinder is also provided to turn the vacuum cup to the right or the left as may be required.

When the end effector is placed adjacent to a vehicle=s fuel inlet and pointed to a fuel door covering the fuel inlet, the pitch is adjusted to center the fuel conduit on the expected position of the fuel inlet behind the fuel door and the vacuum cup is then laterally extended to contact the fuel door. Prior to the vacuum cup contacting the fuel door, vacuum is applied and when a sufficiently negative gauge pressure is sensed in the vacuum line going to the vacuum cup. the extension of the vacuum cup is reversed and the movement of the vacuum cup to swing the hinged fuel door open is initiated. The present invention is an improvement over the method for robotic opening/closing a hinged vehicle fuel door disclosed in U.S. Patent No. 5,609,190.

SUMMARY OF THE INVENTION The present invention is directed to a method for opening and closing a hinged vehicle fuel door during robotic vehicle refueling, the method comprising the steps of providing a robotic fuel door arm; securing the robotic fuel door arm normally to the hinged vehicle fuel door; swinging the secured hinged vehicle fuel door open in angular increments about the vehicle fuel door hinge from a first door open angle to a second door open angle to provide refueling access, the robotic fuel door arm maintaining the hinged vehicle fuel door normally secured to substantially eliminate side loads on the secured hinged vehicle fuel door; swinging the secured hinged vehicle fuel door shut in angular increments about the vehicle fuel door hinge from the second door open angle to the first door open angle, the robotic fuel door arm maintaining the hinged vehicle fuel door normally secured to substantially eliminate side loads on the secured hinged vehicle fuel door; and releasing the shut hinged vehicle fuel door. In accordance with one aspect of the present invention, the securing step comprises the substeps of providing the robotic fuel door arm with a vacuum cup coupled to a substantially universally movable joint, the substantially universally movable joint having a center of rotation; and coupling said vacuum cup normally to the hinged fuel door, the normally coupled vacuum cup defining a vacuum cup docking point on the hinged fuel door.

In accordance with another aspect of the present invention, the swinging open step comprises the substeps of defining a vehicle fuel door opening origin on the fuel door hinge relative to the vacuum cup docking point; computing the distance between the center of rotation and the vehicle fuel door opening origin; and displacing the center of rotation of the substantially universally movable joint incrementally in an arcuate manner about the fuel door opening origin from the first door open angle to the second door open angle maintaining the computed distance constant.

In accordance with yet another aspect of the present invention, the swinging shut step comprises the substep of displacing the center of rotation of the substantially universally movable joint incrementally in an arcuate manner about the fuel door opening origin from the second door open angle to the first door open angle maintaining the computed distance constant.

In accordance with still another aspect of the present invention, an apparatus for controlling the automatic opening and closing of a hinged vehicle fuel door by a robotic vehicle fuel door arm is disclosed. The apparatus comprises at least one computer having fuel door opening and closing sequencing software; at least one door arm joint operatively associated with the at least one computer for sequentially actuating the opening and closing of the hinged vehicle fuel door; and at least one position sensor disposed proximate to the at least one door arm joint for providing closed loop joint position feedback to the at least one computer, the at least one door arm joint controlled by the sequencing software in the at least one computer during the sequential opening and closing of the hinged vehicle fuel door.

In accordance with a different aspect of the present invention, an apparatus for automatically opening and closing a hinged vehicle fuel door during robotic vehicle refueling is disclosed. The apparatus comprises a robotic door arm having a substantially universally movable joint, the substantially universally movable joint having a center of rotation; engaging means coupled to the substantially universally movable joint for attachment normally to the hinged vehicle fuel door and for defining a docking point on the hinged fuel door, the docking point defining a fuel door opening origin on the fuel door hinge; means for computing the distance between the center of rotation and the fuel door opening origin; means for displacing the center of rotation of the substantially universally movable joint incrementally in an arcuate manner about the fuel door opening origin from a first door open angle to a second door open angle to provide refueling access while maintaining the computed distance constant to substantially eliminate side loads on the attached hinged vehicle fuel door; and means for displacing the center of rotation of the substantially universally movable joint incrementally in an arcuate manner about the fuel door opening origin from the second door open angle to the first door open angle while maintaining the computed distance constant to substantially eliminate side loads on the attached hinged vehicle fuel door. These and other aspects of the present invention will become apparent from a review of the accompanying drawings and the following detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of the general arrangement of a robotic refueling system for use in accordance with the present invention;

Figure 2 is a block diagram of a method for automatic opening and closing of a vehicle fuel door using the robotic system of Fig. 1 in accordance with the present invention;

Figure 3 is a block diagram of a process for controlling the robotic refueling system of Fig. 1 during opening and closing of a vehicle fuel door in accordance with the present invention; Figure 4 illustrates a preferred embodiment of the present invention; and Figure 5 is a diagrammatic representation of the preferred embodiment illustrated in Fig. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, some preferred embodiments of the present invention will be described in detail with reference to the related drawings of Figures 1-5. Additional embodiments, features and/or advantages of the invention will become apparent from the ensuing description or may be learned by the practice of the invention.

The following description includes the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention.

The present invention refers to a method for automatic opening and closing of a hinged vehicle fuel door using a robotic vehicle refueling system comprising a manipulator assembly with an end effector having two adjacent arms, one for opening/closing the fuel door (door arm) and another for refueling the vehicle fuel tank (refueling arm). The hinged vehicle fuel door may be located on either side of the vehicle or in the rear of the vehicle and may have a vertical or horizontal hinge. The door arm holds the fuel door during the refueling operation by suction via a vacuum cup located at the tip of the arm with vacuum cup movement controlled by a linear vacuum cup actuator (VCA).

The door arm is manipulated via a door arm rotate actuator and a door arm swing actuator to enable opening and closing of the fuel door. The manipulator assembly also contains a yaw actuator which is active during opening and closing of the vehicle fuel door. The VCA extends the vacuum cup until it docks with the fuel door such that the vacuum cup is able to pull (suck) on the door with a suction force normal to a fuel door tangential plane at the docking point in order to eliminate all side loads on the door during opening and closing of the same. Having secured the fuel door normally, the fuel door is opened sequentially from its initial door open angle (the quiescent or at rest position) to a pre-defined maximum door open angle in a series of incremental steps using precisely coordinated movements of the four active actuators (yaw axis, door arm rotate, door arm swing and VCA extend). The actual movements are computed by an on-site computer from pre-programmed equations (linear transformations) based on door arm kinematics, joint/sequencing/scaling parameters and fuel door hinge geometry which is stored in a computer vehicle identification database (VID). VID contains data on various automotive vehicles taken during preliminary vehicle testing such as fuel door geometry, filler neck location, fuel door location, etc. When the pre-defined (desired) maximum door open angle is reached, the refueling arm extends a nozzle inside the filler neck with the door arm still holding the fuel door normally by suction during refueling. After filling the vehicle tank, the refueling nozzle is fully retracted and the door arm closes the fuel door sequentially in a series of incremental steps being the reverse of the door opening steps with appropriate software commands to the four active joints. After closing the door, suction is discontinued and the door arm releases the fuel door. The end effector is then stowed away until another vehicle is positioned for refueling.

Referring now more particularly to Figure 1 , there is shown the general arrangement of components of a robotic vehicle refueling system 2 of the type disclosed in U.S. Patent No. 5,609,190 which utilizes a fuel door opening assembly constructed in accordance with the principles of the present invention. As is therein shown, an overhead gantry 4 having a set of longitudinal supports 6 and a cross member 8 is provided. Gantry 4 is provided to move an upper manipulator assembly 10 which is disposed over a lower manipulator assembly 12 which sits on top of a pitch assembly 7 to position an end effector 14 preferably on either side of a vehicle 18 (or in the rear of a vehicle) adjacent its fuel door such as a vehicle fuel door 16. As shown in Fig. 1, robotic system 2 is capable of moving end effector 14 along axis J, (gantry 4), along axis J₂ (either one of supports 6) and along axis J₃ which is along the longitudinal axis of upper manipulator assembly 10. End effector 14 can also rotate or yaw relative to axis J₃ as shown in Fig. 1 in which case the degree of freedom is along yaw axis (circular arc) J₄. The pitch angle of end effector 14 is varied via pitch assembly 7 with the degree of freedom along pitch axis (circular arc) J₅ whereby the movement is essentially rotation in a plane normal to the yaw plane of rotation (Fig. 1). End effector 14 comprises a refueling arm 15 mounted proximate to a door arm 17. Refueling arm 15 has an elongated body which includes a fuel line and a fueling nozzle 19 for dispensing fuel into the vehicle filler neck. Door arm 17 also has an elongated body including a wrist assembly 21 attached to a flexible accordion-type vacuum cup 23 which can preferably extend forward linearly and which attaches by suction to a portion of vehicle fuel door 16 during refueling. Vacuum cup 23 is extended and retracted linearly by a linear vacuum cup actuator (VCA) (not shown). Position feedback on the VCA extend joint is provided by any known transducer (not shown). The set up includes a pneumatic piston cylinder anchored at a fixed end to a frame that is attached to a pivot bracket.

As shown in Fig. 4, wrist assembly 21 has an internal yaw joint 27 which has an axis of rotation 27a and an internal pitch joint 29 which has an axis of rotation 29a and a flexible vacuum tube 31 which has a central longitudinal axis 31a. As depicted in Fig. 4, axes 31a. 27a and 29a intersect within vacuum tube 31 at point C defining in essence the center of wrist assembly 21. Point C is also designated as vacuum cup control point for purposes of describing the present invention. Point C can also be described as the center of rotation of a universal Hooke=s (ball and socket) joint. Any other substantially universally movable joint may be used in this regard if such a joint does not depart from the intended purpose of the present invention. Wrist assembly 21 is fitted in vacuum cup 23 (shown separate from wrist assembly 21 in Fig. 4 for clarity). Prior to vacuum cup 23 contacting fuel door 16, vacuum is applied to the center of the suction cup 23 via vacuum tube 31. Upon contact with door 16 at a docking point D (Fig. 4), negative pressure is increased at which point the extension of vacuum cup 23 is reversed securing cup 23 to door 16. Further details on the structure and operation of wrist assembly 21 are disclosed in United States patent application entitled WRIST ASSEMBLY FOR ROBOTIC REFUELING SYSTEMS (attorney docket TH1620) which is assigned to the assignee of the present application and is incorporated herein by reference, both patent applications being filed together on the same date with the United States Patent and Trademark Office.

Door arm 17 is also provided with a door arm swing actuator (not shown) defining a door arm swing joint and an associated position sensor (not shown) for angular position feedback during operation. Door arm swing is essentially rotation along a circular arc in a plane normal to the plane of motion of the VCA extend.

Door arm 17 is further provided with a door arm rotate actuator (not shown) defining a door arm rotate joint and an associated rotary position sensor (not shown) for angular position feedback during operation. Door arm rotate is essentially rotation along a circular arc in a plane normal to the door arm swing plane of motion (also normal to the VCA extend plane of motion).

Further details on the structure and operation of door arm 17 are disclosed in United States patent application entitled FUEL DOOR OPENING ASSEMBLY FOR USE WITH AUTOMATIC ROBOTIC REFUELING SYSTEM which is assigned to the assignee of the present application and is incorporated herein by reference, both patent applications being filed together on the same date with the United States Patent and Trademark Office.

The location of the vehicle fuel filler tube (not shown) can be determined from data obtained from a transponder card (not shown) which is disposed within the vehicle to be refueled. The transponder card can be one of various types which provide vehicle information to automated refueling system 2 informing the same of the vehicle fuel filler tube (neck) and fuel door location. As shown in Fig. 1 , typically a customer interface 20 is provided to allow communication between the driver of the vehicle and robotic system 2.

Customer interface 20 allows the driver to input various types of information in system 2 such as credit card, type of fuel and any other information that may be needed by the system.

Automated refueling system 2 also includes a vision system comprising a camera 22 positioned (Fig. 1) above the expected location of the parked vehicle looking down at the vehicle. Camera 22 produces an image that is captured, reduced to a digital format and communicated to a primary computer 30 (Fig. 3) having a hard drive and a microprocessor such as Pentium II/III or the like. Primary computer 30 may be located conveniently in an adjacent building at the robotic system site or off-site. The vision system can determine from the data provided by camera 22 the actual location of vehicle 18 as long as vehicle 18 is parked within view of camera 22. The camera data, along with information provided by the transponder card, is processed by primary computer 30 which outputs corresponding software command signals to a secondary computer 32 (Fig. 3) to move end effector 14 to an appropriate position to refuel vehicle 18 automatically. The software commands are part of the door path planning (sequencing) software which contains the various kinematic linear system transformations describing joint movements, all pertinent joint parameters (dimensions, equipment), various sequencing parameters (limits, offsets) and any pertinent scaling parameters and is installed in primary computer 30. Secondary computer 32 communicates in turn via a Device Net Node (DNN) 34 (Fig. 3) located in a control compartment 36 contained in lower manipulator assembly 12 with four of the above- mentioned joints, namely the yaw joint, the door arm swing joint, the door arm rotate joint and the VCA extend joint causing door arm 14 to open and close fuel door 16 in an orchestrated fashion to accomplish the automatic refueling. Secondary computer 32 contains joint movement control software which handles actual joint movements in a closed loop feedback fashion (controls loop closures) receiving continuous position feedback information from each of the active joint sensors. In particular, secondary computer 32 controls movement of the door arm swing joint based on closed loop position feedback from the door arm swing position sensor (box 36 in Fig. 3). Similarly, secondary computer 32 controls movement of the door arm rotate joint based on closed loop position feedback from the door arm rotate rotary position sensor (box 38 in Fig. 3). Also, secondary computer 32 controls movement of the VCA extend joint based on closed loop position feedback from the VCA linear position sensor (box 40 in Fig. 3). Moreover, secondary computer 32 controls movement of the yaw joint based on closed loop position feedback from a digital encoder (not shown) located in the yaw motor (not shown) - box 42 in Fig. 3. The degrees of freedom of the door arm rotate, swing and VCA joints for the purpose of disclosing the present invention will be hereby designated E„ E₂ and E₃, respectively. Secondary computer 32 also provides feedback to primary computer 30 during the opening/closing operation as shown in Fig. 3.

The above-described robotic set up is capable of providing a relatively high control bandwidth for each of the above-mentioned active joints, which is of primary importance in any robotic control system, so that each active joint is capable of fast response to a software command within a pre-set tolerance range. Also, the robotic set up does not employ force feedback which is the standard mode of operation in prior art robotic refueling systems, rather position sensors are used which is a much simpler and cost efficient feedback control approach.

In accordance with a preferred embodiment of the present invention, the opening and closing fuel door sequence, as illustrated in Fig. 2, is achieved in a series of steps. Specifically, the first step in the door path planning software (which is stored on primary computer 30) sequence, i.e. step 50 in Fig. 2, involves fine positioning of end effector 14 to locate fuel door 16 in preparation for extending vacuum cup 23 towards fuel door 16. End effector 14 preferably includes an on-board camera (not shown) which takes an image of fuel door 16 and sends the same to primary computer 30 for template matching. Primary computer 30 compares the image of the current location of the vehicle fuel door with an image of the Aideal≡ location of the vehicle fuel door for the particular vehicle type/model which was previously taken during vehicle testing and stored in VID. When the two images match, an output signal is sent by primary computer 30 to secondary computer 32 with the output being the desired fuel test position (FTP) of end effector 14 so as to be able to accomplish robotic refueling of the particular parked vehicle. Providing a FTP is essentially asking the robot to move rather than the driver moving the parked vehicle to an Aideal≡ refueling position which is obviously impractical. The next step (step 52) in the door path planning software involves moving J,, J₂, J_l5 J₄ and J₅ axes as needed to position end effector 14 at the desired ( Aideal≡) FTP. Movement of the axes is accomplished by secondary computer 32 on command from primary computer 30. The door arm rotate joint, the door arm swing joint and the VCA extend joint remain passive (or stowed) or. in other words, door arm 16 does not change its orientation during this step.

Having moved end effector 14 to FTP, the next command, step 53, from primary computer 30 is to extend the VCA until the vacuum switch is closed, i.e. until vacuum cup 23 has docked onto and secured normally vehicle fuel door 16 (as mentioned hereinabove) at docking point D (Figs. 3, 4). Secondary computer 32 receives the command and issues an appropriate control software command to the VCA joint via DNN 34 to extend vacuum cup 23 accordingly. The VCA linear position sensor continuously sends position feedback on the vacuum cup location to secondary computer 32 which compares actual VCA stroke with desired (or ideal) VCA stroke and produces an error (difference) signal.

If the error is within a pre-set tolerance range (step 54), step 58 applies. If the error is outside of the tolerance range, the error or difference in position is applied to the FTP and the sequence repeats (Step 56) until the error between the actual VCA stroke and the requested VCA stroke is minimized, i.e. is within the pre-set tolerance (Figs. 2 - 3). Having achieved the desired VCA stroke, a software command (step 58) is issued from primary computer 30 to check with VID if the parked vehicle is equipped with an internal release. If so, a soft pull sequence command (step 60) is issued from primary computer 30 to secondary computer 32 to move the VCA extend joint in order to pull with a limited amount of force on fuel door 16 at the area of docking. The next command (step 62) from primary computer 30 is to ask the driver via driver interface 20 to release fuel door 16 in preparation for door opening sequence. Actual soft pull movement of the VCA joint is directed by secondary computer 32 which issues an appropriate software command via DNN 34.

If the vehicle fuel door is not equipped with an internal release or if the internal release has been released, the actual fuel door opening sequence may now begin.

The first command (step 64) in the fuel door opening sequence comes from primary computer 30 which commands secondary computer 32 to move the yaw joint so as to remove fueling arm nozzle 19 out of the anticipated fuel door opening path. Secondary computer 32 complies communicating with the yaw joint via DNN 34 and using closed loop feedback through out the step.

In accordance with another preferred embodiment of the present invention, as illustrated in Fig. 4, vacuum cup 23, which generally has a circular cross-section at its docking end 23a, is docked on fuel door 16 in circular area 13 such that central axis 3 la is parallel with a unit normal vector N emanating from a tangential plane at docking point D on the outer surface of fuel door 16. In other words, and in accordance with the best mode for practicing the present invention, if central axis 31a is imagined having a unit docking vector at its tip, the scalar (dot) product of such a unit docking vector with unit normal vector N should be equal to 1 which would ensure a normal suction force at docking point D eliminating (or minimizing within a pre-set tolerance) all side loads on the fuel door during the opening and closing operation as long as such a normal suction force is maintained throughout the fuel door opening and closing operation. The present invention is capable of maintaining a normal suction force at docking point D at all times during fuel door opening/closing (as will be described hereinbelow) which is a marked improvement over prior art fuel door opening/closing methods in which jerking of the fuel door in all directions is standard and may result in undesirable damage to the fuel door.

In accordance with the general principles of the present invention, the two wrist joints (27, 29) are not under the control of secondary computer 32 during the fuel door opening and closing operation. Specifically, wrist yaw joint 27 and wrist pitch joint 29 remain free to move during opening of door 16. Since door arm 16 does not change its orientation during step 52 (as mentioned above), the actual docking location (area 13) of vacuum cup 23 follows from the FTP determined in step 52. Thus, the coordinates of docking point D on fuel door 16 are known. Therefore, as illustrated in Figures 4, 5, drawing a vector normal to fuel door hinge axis 92 from point D would define a unique intersection point O on hinge axis 92 (vector OD - Figures 4, 5) which for the purposes of describing .he present invention will be designated as fuel door opening origin. The location of fuel door hinge axis 92 relative to a Aworld≡ (x, y, z) coordinate system for each vehicle positioned for refueling is available to primary computer 30 from VID. Any fuel door hinge axis can be uniquely defined in x,y,z - space by its rotation angle (in x,y-plane) and its inclination angle (between the hinge axis and z-axis).

In accordance with the best mode for practicing the invention, primary computer 30 calculates the Aworld≡ (x,y,z) location of vacuum cup control point C by forward kinematics, i.e. software transformations of current (E_:, E₂, E₃) active joint positions to corresponding (x,y,z) coordinates. Having calculated the (x,y,z) location of vacuum cup control point C and knowing already the (x,y,z) location of docking point D, a vector CD can be drawn which would make an angle A with vector OD (Fig. 5). Typically, angle A is greater than 90 degrees for most vehicles due to the fact that the fuel door hinge axis is positioned behind the fuel door panel. Since the x,y,z coordinates of points C, D and O are known, a vector OC can be drawn to indicate the relative distance of the vacuum cup control point to the fuel door opening origin (Fig. 5).

In accordance with step 66 (Fig. 2), the magnitude of vector OC (distance between point O and point C) is then readily calculated by primary computer 30. Step 68 involves the automatic inputting of the initial fuel door open angle B₀ (which is known) and the calculated distance OC in the door path planning software residing in primary computer 30.

In step 70, fuel door 16 is preferably opened by pulling incrementally point C about hinge axis origin O such that point C describes a circular arc F of radius of rotation OC starting from an initial fuel door open angle B₀ up to a pre-defined maximum fuel door open angle B_ma (Fig. 5). Fuel door open angle B is incremented in small increments ΔB by the door path planning software installed in primary computer 30 with radius OC rotating from initial angle B₀ to (B₀ + ΔB) to (B₀ + 2ΔB), etc. Pulling center of wrist point C at a constant distance from fuel door opening origin O ensures normal suction force at docking point D throughout the opening sequence substantially eliminating all side loads on fuel door 16 while the same is being opened. The value of maximum fuel door open angle is stored in VID for each qualified vehicle with the data gathered during preliminary vehicle testing. The general preferred angular range for angle B is about 90 degrees - 1 10 degrees.

The following step (72) describes the physical movements behind the incremental rotation of radius OC. In accordance with the general principles of the present invention, step 72, includes primary computer 30 commanding secondary computer 32 to move the center of wrist, point C, incrementally about origin O keeping distance OC constant so as to maintain normal suction force at docking point D at all times while the door is being opened. Primary computer 30 uses inverse kinematics to transform (via its door path planning software) each set of world (x,y,z) coordinates of incrementally displaced point C into corresponding local active joint (E,, E₂, E₃) coordinates for the door arm rotate, door arm swing and VCA extend joints, respectively, and passes each new set of (E,, E₂, E,) coordinates to secondary computer 32. Secondary computer 32 in turn commands simultaneously all active joints via control compartment DNN 34 to move to the desired new (E,, E₂, E₃) position closing the feedback loops at each incremental step within predefined tolerances. When door open angle B_max is reached, the fuel door opening sequence is complete.

Step 74 includes the automatic fueling sequence which is described in detail in United States Patent Nos. 5,609,190; 5,628,351 and 5,634,503 and the above-identified to-be-filed United States patent applications.

Step 76 checks whether fueling nozzle 19 is fully retracted and if so, door closing sequence may begin. If nozzle 19 is not yet fully retracted, a Awaits signal, step 78, is generated from primary computer 30 to secondary computer 32.

Step 80 initiates the fuel door closing sequence which corresponds to reversing the above-described angular sequencing steps. Primary computer 30 uses again inverse kinematics to transform world (x.y.z) coordinates for displaced point C into local active joint coordinates (E1.E2.E3). The sequence moves point C incrementally from maximum fuel door open angle B_max back to initial fuel door open angle B₀. During closing of fuel door 16, wrist yaw joint 27 remains free to move, while wrist pitch joint 29 is preferably mechanically limited in its angular movement to help close door 16.

Step 82 completes the fuel door closing sequence for vehicle fuel doors equipped with internal release by performing a generally uniform open loop extra push of about 1 - 2 pounds on vehicle fuel door 16 in docking area 13 to ensure that fuel door 16 is fully closed before vacuum cup 23 releases fuel door 16. Thereafter, vacuum cup 23 releases fuel door 16 and end effector 14 is stowed. For vehicle fuel doors not equipped with an internal release, vacuum cup 23 automatically releases fuel door 16 at the completion of the door closing sequence.

Finally, it is worth noting that the above-mentioned J,, J₂ J₃ and J₅ axes corresponding respectively to gantry, support, longitudinal upper manipulator axis and pitch assembly remain stationary during the fuel door opening and closing sequence.

The novel fuel door opening and closing method may be used in a variety of robotic refueling systems with the above-described robotic set up being just one of many possible set ups. For example, a ground-based robotic refueling system may be used in which case the bridge and gantry of the above-described set up would be replaced with a pair of tracks on the refueling island. One disadvantage of using ground-based robotic systems is higher set up cost, since refueling may be done only on one side of the vehicle. A second refueling robot is needed on the other side of the vehicle lane to accommodate vehicles with fuel doors located on that side of the vehicle. Another example is a pedestal-mounted articulated door arm having an elbow joint and a wrist joint with the arm free to rotate in all three dimensions whereby the pedestal is bolted to the island. Alternatively, the articulated door arm may be hung from the ceiling of an overhead structure. Other robotic variations and/or modifications may be employed as long as they do not depart from the intended purpose of the present invention.

While the present invention has been described in detail with regards to the preferred embodiments, it should be appreciated that various modifications and variations may be made in the present invention without departing from the scope or spirit of the invention. In this regard it is important to note that practicing the invention is not limited to the above described method steps and novel apparatus. For example, the primary and secondary computer may be combined into a single computer having fuel door opening and closing sequencing software and joint movement control software which would still achieve the goals of the present invention.

Many other applications may be utilized provided that they do not depart from the intended purpose of the present invention. It should also be appreciated by a person skilled in the art that features illustrated or described as part of one embodiment can be used in another embodiment to provide yet another embodiment such that the features are not limited to the specific embodiments described above. Thus, it is intended that the present invention cover such modifications, embodiments and variations as long as they come within the scope of the appended claims and their equivalents.

Claims

What is Claimed is:

1. A method for opening and closing a hinged vehicle fuel door during robotic vehicle refueling, the method comprising the steps of: (a) providing a robotic fuel door arm; (b) securing said robotic fuel door arm normally to the hinged vehicle fuel door;

(c) swinging the secured hinged vehicle fuel door open in angular increments about the vehicle fuel door hinge from a first door open angle to a second door open angle to provide refueling access, said robotic fuel door arm maintaining said hinged vehicle fuel door normally secured to substantially eliminate side loads on the secured hinged vehicle fuel door;

(d) swinging the secured hinged vehicle fuel door shut in angular increments about the vehicle fuel door hinge from said second door open angle to said first door open angle, said robotic fuel door arm maintaining said hinged vehicle fuel door normally secured to substantially eliminate side loads on the secured hinged vehicle fuel door; and

(e) releasing the shut hinged vehicle fuel door.

The method of Claim 1 , wherein said securing step comprises the substeps of:

(b,) providing said robotic fuel door arm with a vacuum cup coupled to a substantially universally movable joint, said substantially universally movable joint having a center of rotation; and

(b₂) coupling said vacuum cup normally to the hinged fuel door, said normally coupled vacuum cup defining a vacuum cup docking point on the hinged fuel door.

3. The method of Claim 2, wherein said swinging open step comprises the substeps of:

(c,) defining a vehicle fuel door opening origin on the fuel door hinge relative to said vacuum cup docking point;

(c₂) computing the distance between said center of rotation and said vehicle fuel door opening origin; and

(c₃) displacing said center of rotation of said substantially universally movable joint incrementally in an arcuate manner about said fuel door opening origin from said first door open angle to said second door open angle while maintaining said computed distance constant.

4. The method of Claim 2, wherein said swinging shut step comprises the substep (d,) of displacing said center of rotation of said substantially universally movable joint incrementally in an arcuate manner about said fuel door opening origin from said second door open angle to said first door open angle maintaining said computed distance constant.

5. An apparatus for controlling the automatic opening and closing of a hinged vehicle fuel door by a robotic vehicle fuel door arm, said apparatus comprising: at least one computer having fuel door opening and closing sequencing software; at least one door arm joint operatively associated with said at least one computer for sequentially actuating the opening and closing of the hinged vehicle fuel door; and at least one position sensor disposed proximate to said at least one door arm joint for providing closed loop joint position feedback to said at least one computer, said at least one door arm joint controlled by said sequencing software in said at least one computer during the sequential opening and closing of the hinged vehicle fuel door.

6. An apparatus for automatically opening and closing a hinged vehicle fuel door during robotic vehicle refueling, said apparatus comprising: a robotic door arm having a substantially universally movable joint, said substantially universally movable joint having a center of rotation; engaging means coupled to said substantially universally movable joint for attachment normally to the hinged vehicle fuel door and for defining a docking point on the hinged fuel door, said docking point defining a fuel door opening origin on the fuel door hinge; means for computing the distance between said center of rotation and said fuel door opening origin; means for displacing said center of rotation of said substantially universally movable joint incrementally in an arcuate manner about said fuel door opening origin from a first door open angle to a second door open angle to provide refueling access while maintaining said computed distance constant to substantially eliminate side loads on the attached hinged vehicle fuel door; and means for displacing said center of rotation of said substantially universally movable joint incrementally in an arcuate manner about said fuel door opening origin from said second door open angle to said first door open angle while maintaining said computed distance constant to substantially eliminate side loads on the attached hinged vehicle fuel door.