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Claims  |
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I claim:
1. In a robotic system including a robot arm, a gripper assembly
comprising:
a movable support;
a pair of finger mounts;
a pair of fingers coupled to respective ones of said finger mounts;
shifting means, shiftably coupling said finger mounts to said movable
support, for movement of said finger mounts toward and away from each
other, said shifting means including a DC servo motor having a drive
shaft, and rack and pinion means, coupling said drive shaft to said finger
mounts, for shifting said finger mounts toward and away from each other as
a function of the rotation of said drive shaft drive shaft in opposed
directions;
servo means, coupled to the servo motor for driving the finger mounts
toward and away from each other, whereby a component to be moved can be
gripped by said fingers; and
control means for controlling the actuation of said servo means.
2. In a system as set forth in claim 1, wherein said drive shaft is
generally vertical, said rack and pinion means including racks which are
movable generally in horizontal paths.
3. In a system as set forth in claim 2, further including a linear bearing
for each rack, respectively, the racks being movable on the respective
bearing for movement relative to the support.
4. In a system as set forth in claim 2, wherein said drive shaft of said
motor is generally horizontally disposed, and further including a
rotatable shaft and ball screw mounted on said movable support for
movement relative thereto, one of the racks being coupled to said ball
screw, and an idler pinion gear coupled to said movable support and
connecting said racks together whereby the racks will move together toward
and away from each other.
5. In a robotic system including a robot arm, a gripper assembly
comprising:
a movable support;
a pair of finger mounts;
shifting means, shiftably coupling said finger mounts to said movable
support, for movement of said finger mounts toward and away from each
other, said shifting means comprising
a motor having a drive shaft,
a pinion coupled to said drive shaft,
a first rack coupled between a first side of said pinion and a first one of
said finger mounts for movement of said first finger mount in a first
direction, and
a second rack coupled between a second side of said pinion and a second one
of said finger mounts for movement of said second finger mount in a second
direction;
a pair of fingers coupled to respective ones of said finger mounts;
servo means, coupled to the motor for driving the finger mounts toward and
away from each other, whereby a component to be moved can be gripped by
said fingers; and control means for controlling the actuation of said
servo means.
6. In a robotic system including a robot arm, a gripper assembly
comprising:
a movable support;
a pair of finger mounts;
shifting means, shiftably coupling said finger mounts to said movable
support, for movement of said finger mounts toward and away form each
other, said shifting means comprising
a motor
a drive shaft coupled to said motor,
a ball screw mounted on said drive shaft,
a first rack coupled to said ball screw and a first one of said finger
mounts for movement of said first finger mount in a first direction,
a pinion having a first side coupled to said first rack, and
a second rack coupled between a second side of said pinion and a second one
of said finger mounts for movement of said second finger mount in a second
direction;
a pair of fingers coupled to respective ones of said finger mounts;
servo means, coupled to the motor, for driving the finger mounts toward and
away form each other whereby a component to be moved can be gripped by
said fingers; and
control means for controlling the actuation of said servo means.
7. A gripper system for attachment to a robot arm comprising:
first and second fingers for grasping an object to be moved;
means, coupled to said fingers, for moving said fingers simultaneously in
opposite directions;
a motor, coupled to said means for moving, for driving said means for
moving;
feedback means, coupled to one of said motor and said means for moving, for
providing a feedback signal corresponding to a position of said means for
moving;
servo means, having an input terminal, a feedback terminal and an output
terminal, for providing an output signal on said output terminal, said
feedback signal being provided to said feedback terminal, said output
signal having a first value if an input signal on said input terminal is
greater than said feedback signal and having a second value if said input
signal is less than said feedback signal;
an amplifier coupling said output terminal of said servo means to a power
input of said motor;
a controller having an output coupled to said input of said servo means,
said controller including a program for directing the operation of said
gripper system in response to a plurality of system control signals
provided to an input to said controller;
an input/output port coupled to said controller input for providing said
system control signals to said controller input; and
remote control means, coupled to said controller, for directing the
operation of said fingers, said remote control means including;
a servo/open switch having an open position for disabling said motor and a
servo position for controlling said motor with said remote control means,
an open/close switch for providing a signal to said controller indicating a
direction for said motor, and
a halt switch for stopping the operation of said motor.
8. A method for teaching the gripper system of claim 7 the finger position
for a specified component comprising the steps of:
inputting a part number to said controller
switching said servo/open switch into said servo position;
providing a drive input to said controller from said remote control means
to drive said fingers either towards or away from each other until said
component is grasped by said fingers;
providing a halt signal to said controller;
providing a return signal to said controller; and
storing, in response to said return signal, a current position of said
means for moving under said part number.
9. A method for teaching the gripper system of claim 7 the finger position
for a specified component comprising the steps of:
inputting a part number to said controller for said specified component;
switching said servo/open switch into said open portion;
removing power from said motor;
manually moving said fingers either towards or away from each other until
said component is grasped by said fingers;
providing a return signal to said controller; and
storing, in response to said return signal, a current position of said
means for moving under said part number.
10. A method for grasping a component which has been taught according to
the method of claim 8, comprising the steps of:
inputting said part number;
providing a current position of said fingers to said controller;
comparing said current portion to said stored position for said part
number;
providing a direction signal to said motor dependent upon the results of
said comparison; and
providing a drive signal to said motor until a current position provided by
said feedback means corresponds to said stored position.
11. A method for grasping a component which has been taught according to
the method of claim 9, comprising the steps of:
inputting said part number;
providing a current position of said fingers to said controller;
comparing said current position to said stored position for said part
number;
providing a direction signal to said motor dependent upon the results of
said comparison; and
providing a drive signal to said motor until a current position provided by
said feedback means corresponds to said stored position.
12. A gripper system for attachment to a robot arm comprising:
first and second fingers for grasping an object to be moved;
means, coupled to said fingers, for moving said fingers simultaneously in
opposite directions, said means for moving comprising
a motor,
a drive shaft coupled to said motor,
a pinion coupled to said drive shaft,
a first rack coupled between a first side of said pinion and a first one of
said finger mounts for movement of said first finger mount in a first
direction, an
a second rack coupled between a second side of said pinion and a second one
of said finger mounts for movement of said second finger mount in a second
direction;
feedback means, coupled to one of said motor and said means for moving, for
providing a feedback signal corresponding to a position of said means for
moving ;
servo means, having an input terminal, a feedback terminal and an output
terminal, for providing an output signal on aid output terminal, said
feedback signal being provided to said feedback terminal, said output
signal having a first value if an input signal on said input terminal is
greater than said feedback signal and having a second value if said input
signal is less than said feedback signal;
an amplifier coupling said output terminal of said servo means to a power
input of said motor;
a controller having an output coupled to said input of said servo means,
said controller including a program for directing the operation of said
gripper system in response to a plurality of system control signals
providing to an input to said controller; and
an input/output port coupled to said controller input for providing said
system control signals to said controller input.
13. A gripper system for attachment to a robot arm comprising:
first and second fingers for grasping an object to be moved;
means, coupled to said fingers, for moving said fingers simultaneously in
opposite directions, said means for moving comprising
a motor,
a drive shaft coupled to said motor,
a ball screw mounted on said drive shaft,
a first rack coupled to said ball screw and a first one of said finger
mounts for movement of said first finger mount in a first direction,
a pinion having a first side coupled to said first rack, ad
a second rack coupled between a second side of said pinion and a second one
of said finger mounts for movement of said second finger mount in a second
direction;
feedback means, coupled to one of said motor and said means for moving, for
providing a feedback signal corresponding to a position of said means for
moving;
servo means, having an input terminal, a feedback terminal and an output
terminal, for providing an output signal on said output terminal, said
feedback signal being provided to said feedback terminal, said output
signal having a first value if an input signal on said input terminal is
greater than said feedback signal and having a second value if said input
signal is less than said feedback signal;
an amplifier coupling said output terminal of said servo means to a power
input of said motor;
a controller having an output coupled to said input of said servo means,
said controller including a program for directing the operation of said
gripper system in response to a plurality of system control signals
provided to an input to said controller; and
an input/output port coupled to said controller input for providing said
system control signals to said controller input. |
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Claims |
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Description |
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The appendix contains a listing of a computer program implementing the flow
chart of FIG. 7.
This invention relates to improvements in the capability of robotic systems
and, more particularly, to an improved gripper assembly having
position-controlled finger mounts for gripping components of different
types and sizes.
BACKGROUND OF THE INVENTION
Robots which are used to move and manipulate parts are typically comprised
of a robotic arm having a gripper at the end thereof. The robotic arm is
typically moved to position the gripper around the object to be grasped,
and the gripper is then activated to grasp the object and hold it during
movement of the robotic arm. Typically, such grippers are pneumatic. The
gripper will typically have a full open position and will close with a
constant amount of force upon the application of air pressure. Such
pneumatic systems are usually limited in the amount of travel of the
gripper fingers, with one inch being average. The gripper would close
until the two fingers touch each other except for the intermediate contact
with the object to be moved.
In a gripper previously sold by applicant, the gripper has a stationary
finger and a moveable finger. The movable finger is controlled by a DC
motor to position the finger as desired. An encoder on the shaft of the DC
motor provides a feedback signal to a servo system which controls power to
the DC motor. The system includes a serial port for providing assembly
level commands to the servo system. The commands can be provided to the
servo system of the gripper by the computer system controlling the robotic
arm. The servo system output is coupled to the DC motor power supply
through a linear analog amplifier. The motor is coupled to control the
movable finger through a rack and pinion in one model or a ball screw and
rack in another model.
SUMMARY OF THE INVENTION
The present invention is an improved gripper for attachment to a robot arm.
The gripper system is a stand alone unit with its own controller and has a
pair of fingers, both of which are movable in opposite directions. The
controller is programmed to direct the operation of the gripper system in
response to system input signals. The fingers are controlled by a
mechanism for moving the fingers simultaneously in opposite directions
with the driving power being supplied by a motor. Feedback from the motor
or moving mechanism is provided to a servo mechanism which provides a
power signal to the motor through an intermediate amplifier. The servo
system compares an input signal from the controller to the feedback signal
and causes the motor to move in an appropriate direction.
The two moving fingers of the gripper of the present invention provide
increased flexibility for a robotic system. The controller allows the
gripper unit to be a turn key device which can be controlled simply
through menu driven software on an associated terminal or other input
means.
Two embodiments are shown for simultaneously moving both fingers in
opposite directions. In a first embodiment, a pinion is coupled to the
drive shaft of the motor and mounted between two racks. The pinion causes
the racks to move in opposite directions, with one rack being coupled to a
first finger and the other rack being coupled to a second finger.
In a second embodiment, a drive shaft coupled to the motor has a ball screw
mounted on it which is connected to a first rack coupled to a first
finger. The first rack is coupled through an intermediate pinion to a
second rack which is coupled to the second finger. Thus, movement in
opposite directions is generated through the combination of a ball screw
and rack and pinion arrangement.
The gripper system can be operated either via a terminal or a remote
control box. The remote box can be carried by an operator to a position
adjacent the gripper for teaching the gripper the size of a component to
be moved. Control of the system is transferred to the remote control by
the movement of a switch on the box. The operator can then use other
switches to directly move the gripper fingers in one direction or the
other or can use a switch to disconnect the motor so that the operator can
manually move the fingers to the desired position for gripping the part.
The operator physically pushes the fingers to the desired position and
then hits a return button on a terminal to store the position.
In the preferred embodiment, the feedback mechanism is an encoder coupled
to the motor drive shaft This encoder provides a square wave proportional
to the position of the drive shaft. The square wave is provided as an
input to the servo system which compares the position represented by the
square wave to a desired position input by the controller. The servo
system an analog output to a pulse width modulated pWM amplifier. The PWN
amplifier converts the analog servo signal into digital form for
performing pulse width modulation of an output signal. The output signal
is filtered to give an analog output which is provided to the DC motor.
Different sizes and shapes of parts can be taught to the gripper using the
remote control box. The operator first inputs a part number into the
system and then uses the remote control box to position the gripper
fingers on the object with the proper amount of force. Then, by simply
hitting the return button on a terminal, the system will store the desired
gripping position in association with the designated part number. The
gripper position itself includes a force component since a greater force
will translate into a slightly different position of the gripper fingers.
Thereafter, in a run mode, the gripper will move to a position it has been
"taught" when the designated part number is specified. The speed of
movement of the fingers can be separately programmed to vary the time for
which the gripping force is applied to the object to be moved.
The present invention thus provides an improved gripper system with
increased flexibility and capabilities. The system can also be used to
verify the proper size of an object to be moved by comparing the position
in which the fingers stop (indicating contact with the object) with the
desired position of the gripper arms.
Other objects of this invention will become apparent as the following
specification progresses, and with reference to the accompanying drawings
for an illustration of several embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the robotic system of the present
invention, showing the way in which the system can be used, for instance
an application of placing a component on the board in a specific location
on a circuit board;
FIG. 2 is a front elevational view of one embodiment of the servo gripper
of the present invention, the gripper being partially broken away to
illustrate details of construction;
FIG. 3 is a vertical section looking in the direction of one and of the
servo gripper of FIG. 2;
FIG. 4 is a view similar to FIG. 2 but illustrating a second embodiment of
the servo gripper of the present invention;
FIG. 5 is a view similar to FIG. 3 but showing the second embodiment of the
servo gripper;
FIG. 6 is a block diagram of the robotic system of the present invention;
FIG. 7 is a flow chart, showing the functions of the robotic system of the
present invention;
FIG. 7A is a flow chart of the teach subroutine of FIG. 7; and
FIG. 7B is a flow chart of the run subroutine of FIG. 7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The robotic system of the present invention is broadly denoted by the
numeral 10 and includes a first embodiment of a servo gripper 12 coupled
with a controller 14 operated by a remote control means 16 having a number
of operating devices, such as switches, thereon. The servo gripper
includes a pair of spaced fingers 18 which are driven laterally by the
mechanism of gripper 12 so as to perform a certain function, such as to
grip and lift a component 20 at one location and move it to a second
location, such as at a specific location 22 on a circuit board 24
positioned on a surface, such as a table top or the like. Gripper 12 is
coupled to a robot arm 13 and is moved about by the arm 13 under the
influence of control means (not shown) for arm 13. Controller 14 is
typically mounted with the controls for the rest of the robotic system.
Gripper 12 may have a programmable gripping force exerted by fingers 18 so
as not to damage the component 20, yet the force will be sufficient to
retain the component clamped by the fingers while the component is being
moved from one place to another. Moreover, gripper 12 can be programmed to
grip and carry a component of any size within a predetermined range. Such
components can be of any desired configuration, such as rectangular or
circular.
A first embodiment of servo gripper 12, using a rack and pinion arrangement
is shown in FIGS. 2 and 3. The gripper 12 is enclosed in a housing 26
which includes a top plate 28 and a side cover 30 which can be opened to
gain access to the interior of housing 26.
Within housing 26 is a DC motor 32 on which is mounted an encoder 34, the
encoder being responsive to and coupled to one end of the drive shaft of
the motor. For purposes of illustration, the motor drive shaft is
vertical. The opposite end 36 of the drive shaft of motor 32 extends
downward from the motor and is secured to a shaft coupling 38 having a
lower stub shaft 40 which is mounted and rotates in a bearing 42 and
having a pinion 44 at the lower end thereof. Bearing 42 is carried by a
pair of legs 45 forming a part of the overall support defined by housing
26, the legs 45 being spaced above a pair of gear racks 46 which are in
mesh with and responsive to pinion 44.
A linear bearing 50 allows one-dimensional linear motion of gear racks 46
on a bottom plate 52 forming a part of housing 26 so that the gear racks
can move in opposite directions with respect to each other in response to
the rotation of pinion 44 under the influence of motor 32. A pair of
finger mounts 54 are coupled with respective gear racks 46. Fingers 18 are
secured to respective mounts 54 as shown in FIG. 2.
When the motor is energized to rotate its shaft in one direction, the
pinion 44 rotates to cause movements of the racks 46 in directions to open
or move fingers 18 apart. When the shaft of the motor is rotated in the
opposite sense, the racks are moved in directions toward each other so as
to move fingers 18 toward each other. The encoder 34 senses the rotation
of the motor drive shaft and thereby provides the information necessary to
position the fingers and set the proper force on the component 20 (FIG. 1)
by fingers 18 when it is desired to lift the component and move it to
another location, such as locations 22 on board 24.
A second embodiment of the servo gripper of the present invention using a
ball screw in combination with a rack and pinion arrangement is denoted by
the numeral 60 and is shown in FIGS. 4 and 5. Gripper 60 includes a
support housing 62 including a top plate 64 and a side cover 66 which is
removable to gain access to the interior of the gripper when desired.
A DC servo motor 68 is mounted by a plate 69 in housing 62 in the manner
such that its drive shaft 70 is, for purposes of illustration, generally
horizontal. The drive shaft 70 is coupled at one end thereof to an encoder
72 and at the opposite end to a timing pulley 74 coupled by a timing belt
76 to a second timing pulley 78 coupled to a shaft 80 journaled in plate
69 and bearing 83. A ball screw 82 is mounted on shaft 80 for linear
movement along the shaft.
The ball screw is coupled to a gear rack 84, which in turn is coupled to a
pinion 86 secured to a vertical shaft 87 rotatably mounted on a fixed part
of the support housing. A second gear rack 88 is in mesh with pinion 86
and is mounted for horizontal, linear movement with respect to housing 62.
A linear bearing 90 couples gear racks 84 and 88 to support housing 62 so
that, as the motor drive shaft 70 rotates, it causes movements of the gear
racks 84 and 88 in opposite directions with respect to each other. Finger
mounts 92 are coupled to respective gear racks 84 and 88 so that fingers,
such as fingers 18, secured to mounts 92 will move toward and away from
each other depending upon the direction of movement of the drive shaft 70
of servo motor 68.
As shown in FIG. 6, controller 14 includes a CPU board 100 coupled to a
servo board 102. An input/output rack 104 is coupled by line 106 to the
CPU board, there being a group 108 of input and output lines coupled by
line 110 to the input/output line of rack 104.
A serial interface 112 is coupled by a line 114 to a terminal 116. A power
amplifier 118 is coupled by a line 120 to servo board 102 and by a line
122 to a gripper interface 124 whose output line 126 supplies gripper
power to gripper 12 or to gripper 60, whichever is used. A line 128
carries encoder signals from encoder 34 or encoder 72 to gripper interface
124 which, in turn, directs such signal over a line 130 to servo board
102. A remote control box 134 is coupled by a line 136 to a pendant
interface 138 which, in turn, is coupled by a line 140 to CPU board 100
and by a line 142 to input/output rack 104.
CPU board 100 contains an Intel 8052 microprocessor, 8K of random access
memory (RAM), 8K of programmable read only memory (PROM) and an
input/output interface. The PROM contains the program for the gripper
system. CPU board 100 can receive inputs from two sources, serial
interface 112 or I/O rack 104. I/O rack 104 consists of a series of
optically isolated interface buffers for coupling to input and output
lines 108 which can be coupled to the main robot controller, a host
computer, or a host programmable logic controller (PLC).
CPU board 100 controls servo board 102 which is preferably a DMC 3000 -10
chip set produced by Galil. The servo board receives the encoder signals
in the form of a square wave pulse from gripper 112 through line 128 and a
connector 120 on a line 130. This square wave pulse is compared with an
input from CPU board 100 and an analog output is provided on line 120 to a
pulse width modulated amplifier 118. PWM amplifier 118 is preferably a
model 201 amplifier from Complex Controls. The output of the amplifiers is
provided on line 122 through gripper interface connector 124 to a motor
power line 126.
Remote control box 134 includes a first switch 131 for designating either
pendant (remote control box) operation or controller operation. The
controller operation position provides inputs to CPU board 100 through
either serial interface 112 or parallel I/O rack 104. The pendant position
puts CPU board 100 under the control of remote control box 134. A second
switch 133 designates whether the gripper is to be operated in the free or
servo mode. In the free mode, the signal from remote control box 134
causes CPU board 100 to remove power from the gripper motor so that an
operator can manually move fingers 18 to a desired position. In the servo
mode, the movement of the fingers is controlled by control box 134.
If the servo mode is selected, the operator will indicate the direction in
which the fingers are to move with a switch 135. If the open position is
chosen, the fingers will move away from each other, if the closed position
is chosen, the fingers will move towards each other. The speed at which
the fingers move is controlled by a dial 137 which the operator can
manipulate to vary the speed at which the fingers move. A hold button 139
is provided as a fail safe to stop the movement of fingers 18.
FIG. 7 shows a flow chart illustrating the operation of the system 10 when
serving to grip, lift and move components, such as component 20, in the
manner shown in FIG. 1.
Four subroutines A-E, are shown in FIG. 7. Subroutine A is the calibration
subroutine in which the controller instructs the motor to move so that the
fingers close to determine the zero position. The position of the encoder
at this closed position is then noted to provide the zero calibration.
In subroutine B, a list of parts to be manipulated by the gripper is input
by an operator via terminal 116 of FIG. 6 or is down loaded from a
computer system through input lines 108.
Teach subroutine C and run subroutine D relate to teaching the system how
to manipulate a part and subsequently manipulating that part,
respectively. The details of these subroutines are shown in FIGS. 7A and
7B, respectively. Subroutine E allows the system to be controlled by a
menu driven software on terminal 116 or directly with commands the I/O
lines 108.
In the teach subroutine as shown in FIG. 7A, the controller first
determines whether the free/servo switch is in the free or servo position
(step F). If the switch is in the free position, a control signal is sent
to stop the operation of the motor (step G). The system is then monitored
to detect a toggling of the servo switch (step H) at which time the input
from the encoder is read (step I) and the encoder input is stored as the
grasping position for a previously designated part number (step J).
If the servo mode was selected, the controller then determines whether the
open/close switch is in the open or closed position (step K). If the open
position is designated, a control signal is sent through servo board 102
to drive the motor in a first direction (step L). If the switch is in the
closed position, a different control signal is provided to servo board 102
to direct the motor to move in an opposite direction (step M). The input
speed from control knob 137 is then read (step). A control signal is then
sent through the servo board 102 to the motor to operate the motor at the
designated speed (step O). If the speed is zero (step 2), the controller
monitors for a return button on the terminal being hit (step P). If the
return key has been hit, the encoder is read and its value is stored as
the position for the designated part number (steps I and J).
Once the system has been taught a particular part, it can be run using the
subroutine of FIG. 7B. A part number is first input (step Q) and the
encoder is read to determine the current gripper position (step R). The
current position is compared to the position stored in memory for the
designated part number (step S) and the determination is made whether the
current position is greater than or less than the desired position (step
T). If the current position is greater, a first control signal is sent
through servo board 102 to the motor to move the motor in a first
direction (step U). If the current position is smaller than the desired
position, a second control signal is sent through servo board 102 to move
the motor in the opposite direction (step B). The controller then
specifies a motor speed to servo board 102 in accordance with a speed
designated by a previous input for the designated part number or a default
speed (step W). The encoder is monitored (step X), and the motor is
operated at the designated speed until the encoder position equals the
designated position (step Y).
The subroutine of FIG. 7B can be varied in a number of respects. For
instance, the encoder position may never reach the designated position in
step Y if the part is out of tolerance. Thus, the controller can end the
subroutine if no change in the encoder signal is detected for a certain
amount of time, indicating that the fingers have contacted the part even
though the desired position has not been reached. This position can then
be compared to the designated position and an out of tolerance signal
generated to terminal 116 if the difference is greater than a
predetermined amount.
SYSTEM OPERATION
To operate system 10, terminal 116 with RS232 serial port is set for 8-bit
data, one stop bit, no parity, and any baud rate from 110 to 9,600. Cable
114 (FIG. 6) connects serial port 112 to terminal 116. Also necessary for
operation is a power source of 115 volts, 60 Hz at 2 amps.
When powering the system, the screen of terminal 116 will be blank. The
controller 14 requires several seconds to boot up. After waiting seven to
eight seconds, the SPACE key of the terminal is pressed to initialize the
serial port on the controller to match it to the baud rate of the
terminal. After the SPACE key has been pressed, the screen will display
"sys int". For the next several seconds, the system will be loading all of
the stored data. Pressing the return key will be bring the Main Menu onto
the screen.
The controller for either gripper 12 or gripper 16 has a menu-driven
operating system. Each time the system is powered up or when returning
from another part of the system, the Main Menu screen is displayed on the
terminal 116. The Main Menu provides several fields from which to choose
from namely calibrate, parts list, teach, run and exit as indicated by
boxes A, B, C, D and E of FIG. 7. The exit field functions only when the
optional command software module is installed in the controller 14. To
call up the field of the Main Menu, it is necessary to enter the
corresponding number of the field and then to press the return key of the
terminal. Unless the gripper is calibrated, it is not possible to enter
the teach mode.
In the calibrate mode, fingers 18 are calibrated to their closed positions.
The fingers first open all of the way to the ends of their paths of
travel. Then the fingers close on center. With the fingers together, they
define the calibrated or "home" position. When the calibration has been
completed, controller 14 then returns to the main menu screen (except
during the run mode).
The parts list mode displays all of the information pertaining to the
taught parts of the gripper. It is possible to teach the gripper a total
of about 32 parts listed on two separate screens, 16 parts per screen. The
data listed for each part includes the part number, the part grip (ID or
OD) part clearance, grip force in the top part widths. After the first 15
parts have been displayed, controller 14 waits for the input to continue.
Pressing the return key will display the second set of 16 parts. Pressing
the return key of the terminal a second time returns the system to the
Main Menu screen.
In the teach mode, information relating to each part is entered into the
system and the part is taught to the gripper. Up to 32 different parts can
be stored in nonvolatile memory. After selecting teach from the Main Menu,
the system asks for input on the part that is to be taught to the gripper.
The first question to be taught relates to the part number. The part can be
any number from 0 to 31. A negative number will exit the system back to
the Main Menu screen.
The second question asks if the grip is ID (inside diameter) or OD (outside
diameter). An ID grip means that the fingers approach the part from the
inside position and move outwardly to grasp the part. An OD grip means
that the fingers approach apart from the outside positions and move
inwardly to grasp the part.
The third question asks for clearance on the part. The part clearance is a
total additional offset the fingers travel to clear the part when the
gripper is approaching or departing the part's location. When the grip is
ID, the part clearance is subtracted from the finger opening. When the
grip is OD, the part clearances added to the finger opening.
The fourth question asks for the grip force. This is a level of force for
the fingers during the move and while holding the part. The grip force
values can range from 0 to 100 with 100 being the maximum force. This
programmable grip force allows for handling of delicate parts along with
heavier objects with the same gripper.
After all required information pertaining to a particular part has been
entered into the system, the system will then list all of the data and ask
if the data is correct. If the answer is no, the system will start over
again with the first question. If the answer is yes, the part will be
taught to the gripper. With the remote pendant interface 138 (FIG. 6), it
is possible to teach the part one of two ways either by jogging the
fingers or by freeing them.
When jogging the fingers there are two speeds i which one can select, slow
or very slow. The fingers are first moved to clear the part and the part
is placed in the way of the fingers to be grasped. When this is done, the
fingers are driven to grasp the part, making sure that the part is
positioned correctly and being held tightly.
It is also possible to teach the part by pressing the free switch on the
pendant. This action turns the servo motor off and allows the fingers to
move freely throughout their travel. With the fingers limp, the part being
taught is placed between the fingers. The fingers are pressed tightly to
hold the part then the switch is toggled back to servo on the pendant The
gripper will servo to that position.
If the remote pendant option is not provided, the fingers will go limp
after the instruction on the screen had reached "teach part the gripper".
The instructions stated previously, use the Free/Servo function on the
pendant. After the fingers on the part have been closed the return key is
pressed on the terminal. The fingers will now servo at that location.
After the fingers have been moved to grasp the part, the return key on the
terminal is pressed. This stores the fingers location along with all the
related data in the nonvolatile memory.
The next question relates to whether or not another part is to be taught. A
"no" answer will exit the system from the teach mode and return it to the
Main Menu screen. A "yes" answer will return the system to the first
question at the beginning of the teach mode.
When selecting the run mode, the controller switches from the menu-driven
operator interface to the digital I/O interface with the host system
(robot controller). A message will appear on the terminal screens, stating
that the controller is in the run mode. In this mode, the controller will
accept only inputs from the digital I/O. To exit from the run mode, it is
necessary to toggle the run/terminal signal bit to terminal along with
setting the abort bit. The system will then return to the Main Menu
screen, an emergency stop will occur, causing the gripper to go limp. The
gripper will need to be calibrated to resume operations.
To drive the gripper, several bits are needed. Part bit 0, part bit 1, part
bid 2, part bit 3 and part bit 4 identify the part number to be used (0 to
31). The open/closed bit calls the offset for the finger positioning. The
read bit commands the controller to read all the bits, assign the part
number, part grip, part clearance (if open bit it set), grip force, along
with part width and to execute the move. When the controller is ready for
the next move, the ready bit will be turned on. While the controller is
reading the bits and executing the move, the ready bit will be turned off.
The abort bit (without the run/terminal bit, set to terminal), will stop
all movements of the gripper. The gripper does not go limp and there is no
need to recalibrate the gripper. The system then continues to the next
read command. It is recommended that the I/O signals be set for 100
millisecond duration.
In the exit mode, the system will function only if the optional command the
software module is installed. The exit mode allows the system to leave the
menu-driven software and drive the gripper directly through assembly like
instructions. The command software module functions only through the
controllers serial port and ignores all digital I/O inputs. It is possible
to enter the commands either through a terminal or a host controller.
The system can be set to Autorun in two different modes on power up. With
both the run/terminal bits set to run and the calibrated bit set to run
and the calibrated set, the system will enter the run mode and calibrate
the gripper. It will be ready to accept read commands.
With just the run bit set, the system will enter the command software
module (if installed). It is possible to then enter commands from either
the robot or host system to drive the gripper. The controller does not
wait for a space key to determine the band rate. The band rate is fixed at
9,600. It is possible to leave either of these modes and return to the
main menu screen at any time.
As it will be understood by those familiar with the art, the present
invention may be embodied in other specific forms without departing from
the spirit or the essential characteristics thereof. For example, the
system can be simultaneously accepting inputs of parts in subroutine B and
be operated by the remote control box. Accordingly, the disclosure of the
preferred embodiments of the invention is intended to be illustrated, but
not limiting, of the scope of the invention which set forth in the
following claims.
##SPC1##
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