Note: Descriptions are shown in the official language in which they were submitted.
2 1 69~85
AGRICULTURAL VEHICLE INCLUDING A 8Y8TEM FOR
AUTOMATICALLY MOVING AN INPLEMENT AND IMPROVED GROUND
HEIGHT ~EN8ING TO A PREDETERMINED OPERATING PO8ITION
RELATED APPLICATIONS
The present patent application is a
continuation-in-part of serial no. 08/265,238, filed on
June 24, 1994.
FIELD OF THE INVENTION
The present invention relates to the operation of an
implement on an agricultural vehicle. In particular, the
invention relates to a multi-sensor arrangement for
determining the minimum distance between the implement
and ground, and controlling the position of the implement
based upon the minimum distance.
BACKGROUND OF THE INVENTION
The operation of most agricultural vehicles requires
substantial operational involvement and control by the
operator. For example, in a combine the operator is
required to control the direction and speed of the
combine while also controlling the height of the combine
head, the air flow through the combine cleaning fan, and
the amount of harvested crop stored on the combine.
Accordingly, to reduce the effort required by the
operator, it is useful to automate as many tasks
performed by the operator as possible.
One task which has been automated is maintaining the
distance between the harvesting implement (head) of a
combine and the ground. More specifically, some combines
2~ 69885
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include control systems which permit an operator to
control and maintain a selected distance between the head
and ground during harvesting and without further
interaction by the operator. This control is based upon
monitoring one or two transducers which produce signals
representative of the distance between the head and
ground.
A problem with such prior systems for automatically
controlling harvesting head height is that the fields are
normally uneven and a single sensor will not sense the
minimum distance to ground, thus, frequently resulting in
head-to-ground contact. Furthermore, even if one were to
use more than one sensor along the head to sense a
plurality of ground heights, the control system would be
required to monitor a plurality of ground height signals
to provide automatic control thereof.
Accordingly, it would be desirable to provide a
ground height sensing arrangement which includes distance
sensors at the ends and center of a head, and additional
distance sensors depending upon the width of the head
(e.g. a 30-foot wide head may require 4 or more sensors).
Furthermore, the arrangement should be configured to
produce only a single distance signal representative of
the smallest distance between the head and ground.
SUMMARY OF THE INVENTION
The present invention relates to a control system
for controlling a positioner assembly for positioning an
implement carried by an agricultural vehicle. The
control system includes at least three position
transducers supported by the implement to produce a
distance signal representative of the distance between
the implement and ground. A comparison circuit monitors
the signals and produces a minimum distance signal
` 21 69~85
- 3 -
representative of the shortest distance between the
implement and ground. The minimum distance signal is
monitored by the control circuit which controls the
position of the implement based upon the minimum distance
signal.
one embodiment of the control circuit includes
operator control switches, a digital processing circuit
and an A/D convertor for applying the minimum distance
signal to the digital processing circuit. The digital
processing circuit is programmed and coupled to the
positioner assembly so that the implement height is
maintained at a predetermined minimum based upon the
minimum height signal.
The invention further provides a method for
controlling a positioner assembly which positions an
implement carried by an agricultural vehicle. The method
includes the steps of sensing the distance of the
implement to ground with a plurality of position
transducers, determining the smallest distance to ground
based upon the transducer signals, and controlling the
position of the implement based upon the smallest
distance to ground.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 illustrates an agricultural vehicle
including a moveable harvesting implement;
FIGURE 2 is a schematic representation of the
preferred embodiment of an implement position control
system;
FIGURE 2A is a schematic representation of a second
embodiment of an implement position sensing arrangement;
FIGURE 3, including sheets 3A-3C, is a schematic
diagram of the control system circuitry; and
FIGURE 4, including sheets 4A-4D, is a flow chart
representative of the programming for the control system.
21 6q~5
- 4 -
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGURE 1, an agricultural vehicle 10
includes a pair of drive wheels 12 located at the front
end of vehicle 10, a pair of steerable wheels 14 located
at the rear end of vehicle 10, a machinery and grain
storage compartment 16, a grain elevator and chute 18, an
operator cab 20, and a support frame (structure) for
joining and supporting the above-listed components. (By
way of example only, vehicle 10 may be a combine of the
type manufactured by Case Corporation having Model No.
1660.) Attached to the front end of the frame of vehicle
10 (i.e. the front-most end of vehicle 10 along its
forward direction of travel during harvesting) is an
implement 22 such as a grain harvesting head. (By way of
example, implement 22 could be a Combine Corn Head Series
1000 sold by Case Corporation.) Implement 22 is
positioned relative to vehicle 10 and/or the surface 23
upon which vehicle 10 is moving (i.e. the ground from
which the respective plant related matter, grain or
vegetation, is being harvested). To efficiently harvest
the grain or vegetation, it is useful to provide control
over the position or location of implement 22.
FIGURE 2 is a schematic representation of the
preferred embodiment of the implement 22 position control
system 24. Control system 24 includes a microprocessor
based control unit (circuit) 26, a man-controller
interface 28, a vehicle direction and speed control lever
30, a hydraulic control valve 32, a position transducer
34, a location transducer 36, a pressure transducer 38,
and an implement lift mechanism 40 (e.g. hydraulic lift
cylinders, cable lift arrangements, hydraulic motor and
gear arrangements, or electric motor and gear
arrangements). In the present embodiment, mechanism 40
includes hydraulic lift cylinders and transducers 34 and
36 are potentiometers. However, transducers 34 and 36
could be replaced with LVDTs.
21 69~85
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Implement 22 is rotatably supported relative to
vehicle 10 by a bearing assembly 42. Bearing assembly 42
includes a fixed bearing portion 44 and a movable bearing
portion 46 fastened to implement 22. Fixed bearing
portion 44 is fastened to vehicle 10 and to attachment
member 45, and control mechanism 40 is mounted between
member 45 and a second attachment member 47 fixed to
implement 22. In this arrangement, system 24 is operable
to control mechanism 40 which moves (rotates) implement
22 relative to vehicle 10. By way of modification,
implement 22 can be movably supported relative to vehicle
10 using other mechanical arrangements such as, for
example, a parallelogram linkage arrangement which
supports implement 22 and, during raising and lowering,
guides implement 22 along a path which is generally
perpendicular to surface 23.
Referring more specifically to system 24, interface
28 includes a mode switch 48, a reference position
(location) signal generator 50, a reference pressure
signal generator 52, a raise rate signal generator 54,
and a lowering rate signal generator 56. In the present
emhoA;~Gnt, generators 50, 52, 54 and 56 are
potentiometers. However, generators 50, 52, 54 and 56
could be switches which are capable of producing digital
signals representative of the associated positions,
pressures and rates.
In addition to mode selector switch 48, system 24
also includes a raise and lower switch 58 which is
mounted in lever 30S By way of example, raise and lower
switch 58 is a centrally biased momentary contact switch.
Switch 48 is coupled to unit 26 by a signal bus 60,
generator 50 is coupled to unit 26 by a signal bus 62,
generator 52 is coupled to unit 26 by a signal bus 64,
generator 54 is coupled to unit 26 by a signal bus 66,
generator 56 is coupled to unit 26 by a signal bus 68,
and switch 58 is coupled to unit 26 by a signal bus 70.
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Control unit 26 is also coupled to transducer 34 by
a signal bus 72, transducer 36 by a signal bus 74, and
transducer 38 by a signal bus 76. Control unit 26 is
coupled to hydraulic control valve 32 by a signal bus 78.
More specifically, control valve 32 includes a raise
solenoid 80 and a lowering solenoid 82 to which signal
bus 78 is connected. Control unit 26 applies pulse width
modulated signals to solenoids 80 and 82 which allow
valve 32 to control the flow of fluid between a
pressurized hydraulic fluid source 84 and lift cylinders
40. In the present embodiment, source 84 is a hydraulic
pump connected in series with a hydraulic fluid storage
tank and appropriate filters.
Referring to FIGURE 3 (3A, 3B, 3C) control unit 26
includes a digital processor 86 (microcontroller, e.g.
Motorola 80C198) having an internal analog-to-digital
converter 88, an analog-to-digital converter voltage
reference source 9o, a processor watchdog circuit 92, an
analog signal filtering and isolation circuit 94, an
analog multiplexer 96, a switch input control circuit 97,
a serial communications interface 98, a memory and a
programmed logic control and memory circuit 100 (e.g.
psd-312 sold by Wafer Scale Integration or
Phillips/Sygnetics), a pulse width signal generation
circuit 102, and a non-volatile memory 104.
Voltage reference source 90 (Fig. 3B) includes
resistors 106 and 108, capacitors 110, 112 and 114, and
operational amplifier 116 coupled to the voltage
reference and analog ground of processor 86 as shown.
Source 90 operates to provide a voltage range for analog-
to-digital converter 88 within which voltage signals are
converted to digital values.
Processor watchdog circuit 92 (Fig. 3B) includes
resistors 118, 120, 122, 123 and 124, capacitors 126, 128
and 130, diode 132, low voltage detector 134, inverter
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136, and transistor 138 coupled to the reset of processor
86 as shown. Circuit 92 resets processor 86 when the
power source 196 voltage falls below a predetermined
level.
Analog multiplexer 96 (Fig. 3B) includes at least
seven analog inputs which are selectively coupled to an
analog output 166, which is in turn coupled to the input
of isolation circuit 94. Signal buses 62, 64, 66, 68,
72, 74 and 76 are coupled to the analog inputs of
multiplexer 96 by appropriate filtering circuits 152,
154, 156, 158, 160, 162 and 164, respectively. The
analog inputs of multiplexer circuit 96 are selectively
switched between the output 166 via a 4-bit data bus 168
which is coupled to the output of control circuit 100.
Accordingly, processor 86 selectively controls the
application of the signals from transducers 34, 36 and 38
and signal generators 50, 52, 54 and 56 to analog-to-
digital converter 88 by applying the appropriate address
signals to control circuit 100, which in turn applies the
appropriate 4-bit signal to data bus 168 for selectively
applying the desired analog signal to analog output 166.
Analog signal isolation circuit 94 (Fig. 3B) is
coupled between output 166 of multiplexer 96 and one
analog input of analog-to-digital converter 88 to provide
filtering and isolation there between. Circuit 94
includes capacitors 140 and 142, operational amplifier
144, zener diode 146, diode 148 and resistor 150 coupled
between output 166 and the analog input channel of
analog-to-digital converter 88 as shown.
As an alternate to the use of multiplexer 96,
multiplexer 96 could be eliminated by using an analog-to-
digital converter 88 with a sufficient number of analog
input channels to handle the analog input signals from
transducers 34, 36 and 38 and signal generators 50, 52,
54 and 56. However, such an arrangement increases the
2 1 69885
amount of circuitry required for filtering and isolation
since an isolation circuit 94 may be required for all of
the analog input channels to analog-to-digital converter
88. Thus, where sufficient sampling speed is obtained by
using multiplexer 96 and a signal analog channel input to
analog-to-digital converter 88, circuitry can be
conserved since only one isolation circuit 94 is
necessary.
The statuses of switch 48 and switch 58 are
monitored by processor 86 via switch input control
circuit 97, coupled between switch 48 and circuit 97, and
control circuit 100. More specifically, signal bus 60
includes three conductors which are coupled to circuit 97
via an appropriate filtering circuit 170. Mode selector
switch 48 includes three contacts each connected to one
of the three signal conductors of bus 60, and selectively
connected to a reference voltage (e.g. 12 volts) upon the
status (position) of mode selector switch 48. When a
signal is not present on bus 60, switch 48 is assumed to
be in the manual position. Signal bus 70 includes two
conductors connected to contacts in raise and lower
switch 58 which are selectively connected to the
reference voltage, depending upon the status of switch 58
(e.g., when switch 58 is in the uppermost position, one
conductor is connected to the reference voltage and when
switch 58 is in the lowermost position, the other
conductor is connected to the reference voltage). Signal
bus 70 is coupled to control circuit 97 by a filtering
circuit 172. In addition to filtering circuit 172,
further filtering is provided by capacitors 174 and 176
coupled between the conductors of bus 70 and ground.
Processor 86, circuit 97 and circuit 100 cooperate
to sequentially sample each of the conductors of signal
buses 60 and 70. More specifically, circuit 97 operates
as a storage and shift register to sample the statuses of
the six signal conductors in signal buses 60 and 70.
21 6~88~
g
Subsequently circuit 97 shifts through the memory
location associated with each conductor, and sequentially
applies a logic level representative of the status of
each conductor to output data line 178 in response to an
input signal at input control line 180 and a clocking
signal at clock conductor 182. By way of example, when
control line 180 is HIGH, the register is cleared, and
when control line 180 is LOW the statuses of the six
signal conductors are stored in the register and the
register is shifted left (or right depending upon the
biasing of circuit 97) in response to each clock pulse on
line 182. Circuit 97 is coupled to processor 86 to
sequentially apply the logic levels representative of the
statuses of the signal conductors of signal buses 60 and
70 to processor 86 via data line 178.
Pulse-width generation circuit 102 (Fig. 3A)
includes a solenoid coil driver circuit 184 (raising), a
solenoid coil driver circuit 186 (lowering), an AND gate
188, an AND gate 190, a flip flop 192, and a pair of
inverters 194 with hysteresis coupled together and to
processor 86 as shown in FIGURE 3. Driver circuit 184
and 186 are conventional circuits for producing
sufficient power to energize the coils of the raise
solenoid 80 and the lowering solenoid 82 of control valve
32, respectively, based upon the output signals from AND
gates 188 and 190, respectively.
The output of flip flop 192 is coupled to a first
input of AND gates 188 and 190. Flip flop 192 is
connected to the PWM pin of processor 86 and applies a
logic HIGH signal to AND gates 188 and 190 at a frequency
determined by the output of processor 86 applied to flip
flop 192 (e.g. lOOHz) with a selectable pulse width. The
second input to AND gate 188 is coupled to one digital
output of processor 86 and the second input of AND gate
190 is coupled to another output of processor 86 to
select one of circuits 184 or 186. The width of the 100
2 1 6~885
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Hz signal applied to coil driver circuits 184 and 186
from gates 188 and 189, respectively, is varied to
control the speed at which lift cylinders 40 are extended
and contracted (i.e., the rate of fluid flow from fluid
source 84 to lift cylinders 40 depends upon the width of
the pulse, where zero width means no movement of
cylinders 40 and maximum pulse width means movement of
cylinders 40 at their maximum speed), respectively. As a
result, the speed at which implement 22 can be raised and
lowered can be varied by varying the width of the pulse
width modulated signal applied to solenoids 80 and 82 by
coil driver circuits 184 and 186, respectively.
Power for control unit 26 is provided from a
conventional 5V power source 196. By way of example,
power source 196 may include a 5V voltage regulator and
appropriate filtering coupled to the battery of vehicle
10. Power from source 196 is provided to processor 86
via filtering circuits 93 and 95. The clocking for
processor 86 is provided by capacitors 87 and 89, and
crystal 91 coupled together as shown in FIGURE 3B.
Serial communications interface 98 (Fig. 3C) is
provided to permit communication between control circuit
26 and other control systems of vehicle 10. For example,
interface 98 is configured to communicate with a display
control circuit 220 configured to drive an alpha-numeric
display 222 such as a LCD display. Interface 98 includes
an inverter with hysteresis 222, capacitors 224, 226 and
228, resistors 230, 232, 234 and 236, and serial
communication chip 238 (e.g. LT 1485N serial chip)
coupled together between the transmit and receive pins of
processor 86 and display control circuit 220 as
illustrated in Figure 3. Display control circuit 220 is
configured to format data transmitted from processor 86
by interface 98 to circuit 220 so that such data is
capable of producing the appropriate characters on
display 222. By way of example, display 222 may have
2 1 6~885
11 --
four seven-segment characters and a decimal point between
three of the characters and the fourth character.
Alternatively, display 222 may also include icons and
text segments in addition to the character segments.
In one embodiment of system 24, processor 86 is
configured (programmed) to transmit data representative
of the position of implement 22 as monitored by
potentiometer 34 to display control circuit 220 via
interface 98. Based upon this data, circuit 220 controls
display 222 to produce a displayed value representative
of the positional relationship between implement 22 and
vehicle 10. Processor 86 is programmed to convert the
position signal produced by potentiometer 34 to data for
controlling display 222 to display the height of
lS implement 22 in inches or centimeters.
Processor 86 can also be programmed to transmit data
to display control circuit 220 which is representative of
the signal produced by potentiometer 36 which is in turn
representative of the location of implement 22 relative
to the ground surface 23. Based upon this data, control
circuit 220 controls display 222 to display a numerical
value representative of the distance between bottom
surface 206 of implement 22 and ground surface 23 (e.g. a
distance having units of inches or centimeters).
Additionally, processor 86 may also be programmed to
transmit data representative of the force (e.g. pounds or
neutrons) being exerted by mechanism 40 on implement 22
to control circuit 220 via interface 98. In particular,
processor 86 monitors transducer 38 and converts the
hydraulic pressure into data representative of the float
force required to maintain the position of implement 22
relative to vehicle 10 or ground surface 23. This data
is utilized by control circuit 220 to produce a number
representative of the force on display 222. By way of
example, the force may be displayed as a percentage of
~1 6~885
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the pressure when implement 22 is fully supported by
surface 23 or mechanism 40.
Depending upon the application, processor 86 may be
programmed to produce display data representative of one
or more of the locations of implement 22 relative to
vehicle 10, the distance of implement 22 relative to
surface 23, or the force applied to implement 22. Where
more than one type of data is displayed, the icons and/or
text segments can be controlled to inform the operator of
the type of data being displayed. System 24 may be
calibrated by setting high and low positions of implement
22 relative to vehicle 10, high and low locations
relative to surface 23, and high and low forces applied
by mechanism 40 by moving implement 22 between the
desired positions and locations, and by applying a range
of forces while in a calibration mode. Furthermore,
processor 86 may be programmed to permit calibration of a
range for the display data.
The interaction of control circuit 26 with valve 32
for controlling the raising and lowering of implement 22
is described in detail below in reference to FIGURE 4.
The programming which configures (programs) processor 86
to provide appropriate control of the position of
implement 22, also described in reference to FIGURE 4, is
stored in memory circuit 100. In general, control unit
26 controls the position of implement 22 based upon the
position (setting) of selector switch 48, the status of
switch 58, the digital values produced by analog-to-
digital converter 88 representative of the settings of
generators 50, 52, 54 and 56, and the analog signals
produced by transducers 34, 36 and 38.
As discussed above, transducers 34 and 36 are
potentiometers in the present embodiment. Potentiometer
34 is mechanically coupled to a linkage arrangement 200
which rotates the wiper of potentiometer 34 to produce a
21 6q~85
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voltage representative of the positional relationship
between implement 22 and vehicle 10. Potentiometer 36 is
mechanically coupled to a location sensor skid 202,
located generally at the center of implement 22, and to a
cable arrangement 204 which move the wiper of
potentiometer 36 based upon the distance between the
bottom 206 of implement 22 and the surface 23 upon which
skid 202 is resting. This arrangement of potentiometer
36, skid 202 and cable arrangement 204 produces a voltage
representative of the distance between bottom 206 and
surface 23. Alternatively, depending upon the
application, another type of proximity sensor such as an
ultrasound sensor could be substituted for potentiometer
36, skid 202 and cable assembly 204 to produce a signal
representative of the distance between bottom 206 and
surface 23.
In Figure 2A another embodiment of the implement
location sensor of system 24 is schematically
illustrated, and includes a plurality of potentiometers
36, 36a, 36b, 36c being connected to respective skids
202, 202a, 202b, 202c spaced along the bottom 206 of
implement 22. The plurality of position transducers
(i.e. potentiometers 36, 36a, 36b, 36c and associated
skids 202, 202a, 202b, 202c) are supported by the
implement to produce a plurality of signals
representative of the distances between surface 23 and
bottom 206 at a plurality of locations spaced apart along
the implement. Preferably, the skids 202, 202a, 202b,
202c are located along a line on the bottom 206 of the
implement along its width (perpendicular to the transport
direction of the implement), which line is, in normal
operation conditions on planar ground, parallel to the
ground.
The voltages generated by potentiometer 36-36c are
applied to the input of a comparison circuit 25. Circuit
25 includes an A/D converter 25a, a microprocessor 25b,
21 69885
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and a conversion circuit 25c. By way of example only,
A/D 25a and microprocessor 25b may be integrated into a
single microcontroller such as a Motorola 68HC705. A/D
25a converts the signals generated by potentiometer 36-
36c into digital signals. Microprocessor 25b isprogrammed (configured) to select the digital signal
representative of the smallest monitored distance between
the ground and the implement ("selected signal").
Based upon the selected signal, microprocessor 25b
generates a pulse-width-modulated ("PWM") signal which is
related (e.g. proportional) to the smallest distance
between the ground and the implement. The PWM signal is
converted back to an analog signal by conversion circuit
25c which applies the analog signal to conductor 74.
Circuit 25c is configured to produce analog signals
within the voltage range acceptable by control unit 26.
By way of example, conversion circuit 25c may be a
filter.
In the presently preferred embodiment of circuit 25,
this circuit is separate from control unit 26 so that
unit 26 is not burdened with the task of converting more
than one position signal to digital data, and selecting
the signal representative of the smallest distance
between the implement and ground. Because the position
of the implement must be actively controlled in real
time, this separation of tasks may be important depending
upon the computational speed of unit 26.
In an alternative embodiment of comparison circuit
25, A/D 25a, microprocessor 25b an circuit 25c could be
replaced with an analog comparison circuit. In
particular, each of the signals from potentiometer 36-36c
would be applied to a circuit including analog
comparators arranged to output the potentiometer signal
which represents the smallest monitored distance between
the implement and the ground.
21 69~85
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As another alternative, circuit 25 could be
implemented with a multiplexer circuit operable with a
comparator circuit which selects the multiplexer address
based upon a comparison of the input signals of the
position transducers. Thus, the multiplexer applies the
signal corresponding to the lowest distance to surface 23
to signal bus 74. In the latter case it may be
preferable to process the multiplexed position transducer
signals in an analog-to-digital converter before
comparison so that the comparator circuit could be
implemented with a digital processor ti.e. logic gate
array or simple microprocessor). From the above it
follows that the comparator circuit could either be
adapted to process analog or adapted to process digital
data, and that the output sent via signal bus 74 to
control circuit 26 could either be a digital value or the
analog signal corresponding to the smallest distance
above ground. If the signal is digital, bus 74 would be
coupled to a serial input of control unit 26 rather than
A/D 88.
In the present embodiment, transducer 38 is a
pressure transducer which communicates with the fluid
conduit which pressurizes lift cylinder 40 to raise
implement 22. This arrangement of pressure transducer 38
produces a signal representative of the force being
applied to implement 22 for example, equal to some
minimum value when the full weight of implement 22 is not
being supported by surface 23.
System 24 can operate in a manual mode, return to
cut (RTC) mode, a float mode, and a height mode. In the
manual mode, system 24 moves implement 22 up and down in
response to the operation of switch 58. In the height
mode, system 24 maintains implement 22 at a selected
location relative to surface 23. In the float mode,
system 24 maintains implement 22 at a selected contact
pressure with surface 23. In the RTC mode, system 24
21 69885
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allows the user to raise implement 22 from a
predetermined position by toggling switch 58 upward
(typically at the end of a row in a field) and then
automatically return to the position by toggling switch
58 downward (typically at the beginning of a row in the
field).
FIGURE 4 (4A, 4B, 4C, 4D) illustrates the sequence
of steps which processor 86 is programmed (configured) to
carry out while operating in one of the manual, RTC,
float or height modes. Each time processor 86 completes
the sequence of steps specified by FIGURE 4, processor 86
clocks the first inputs of AND gates 188 and 190 (FIGURE
3), and applies the appropriate pulse-width signal to the
other inputs of AND gates 188 and l9o. For example, if
upon executing all of the instructions associated with
the flow chart of FIGURE 4, a decision is made to raise
implement 22, 0 width pulses would be applied to AND gate
190 so that coil driver circuit 186 is inoperative, and
pulses of appropriate widths would be applied to AND gate
188 to cause coil driver circuit 184 to open valve 32.
In response, valve 32 applies pressurized fluid to lift
cylinders 40 to raise implement 22.
As discussed in detail below, when implement 22 is
moved by system 24, the speed of movement is based upon
the difference between the selected position and the
desired position, the selected height and the actual
height, or the selected float pressure and the actual
float pressure (e.g., proportional control). Thus, when
the difference is large, the error is large, and the
width of the pulses applied to the appropriate AND gate
188 or 190 is correspondingly large. As the implement is
moved toward the desired position, height location or
float position, the error is reduced, the width of the
pulses applied to the appropriate AND gate 188 or 190 is
reduced to slow the speed at which implement 22 is moved,
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and the speed of implement 22 goes to zero when the
desired setpoint is reached.
In operation, processor 86 samples the status of
selector switch 48 via shift register 97 and circuit 100
to determine the mode of operation for system 24 (step
250, startup). Next, processor 86 determines the digital
value associated with signal generators 50 and 52 (step
252). The analog values produced by generators 50 and 52
are applied to analog-to-digital converter 88 via
multiplexer 96 and filtering circuit 94. Depending upon
the mode selected at switch 48, processor 86 stores the
digital value produced by analog-to-digital converter 88
representative of the position of generator 50 as the
desired height or position value, and the digital value
produced by converter 88 representative of the position
of generator 52 as the desired float value.
In step 254, processor 86 controls multiplexer 96
via databus 168 to apply the signals produced by
potentiometers 34 and 36, and transducer 38, to converter
88 via multiplexer 96 and isolation circuit 94. Upon
applying the respective signals produced by transducers
34, 36 and 38 to converter 88, the digital values
produced by converter 88 are stored by processor 86 in
the memory of circuit 100.
In step 256, processor 86 determines if momentary
switch 58 has been momentarily actuated to the lower most
position (e.g. .1-.6 seconds). If such a condition has
occurred, soft-lower flag is set. In step 258, processor
86 controls multiplexer 96 via bus 168 to apply the
analog signals produced by generators 54 (maximum raise
rate signal, e.g. 2-10 seconds for implement 22 raising)
and generator 56 (maximum lower rate signal, e.g. 2-10
seconds for implement 22 lowering) to analog-to-digital
converter 88 via filtering circuit 94. Processor 86
stores the digital values produced by converter 88
21 6~88S
- 18 -
representative of the maximum raise and lower rates in
circuit 100. Based upon the maximum raise and lower rate
signals, processor 86 calculates and stores acceleration
and deceleration values representative of the
accelerations between zero speed of implement 22 and the
selected raise and lower rates. By appropriately
accelerating and decelerating implement 22 via control
unit 26, relatively smooth motion of implement 22 is
achieved even though hydraulic accumulators are either
eliminated from system 24 or reduced in size.
The raise and lower rate acceleration values are
stored as values which progressively increase to the
maximum raise/lower rate values, and the raise and lower
rate deceleration values are stored as values which
progressively decrease from the maximum raise/lower rate
values to zero. The acceleration values are used by
processor 86 to increase (ramp up) the pulse widths from
zero to the maximum associated with the maximum rate
during the acceleration period for implement 22 (e.g. .1-
.5 seconds), and the deceleration values are used byprocessor 86 to decrease (ramp down) the pulse widths
from the maximum to zero during the period of
deceleration of implement 22 (e.g. .1-.5 seconds).
In step 260, processor 86 reads data stored in
memory 100 representative of the state (selected mode) of
switch 48 and executes the subroutine associated with the
selected mode. In step 262, processor 86 defaults to the
manual mode. In step 264, if switch 48 is set to the
height mode, if the soft lower flag is set, and if the
desired height value as generated by generator 50 is less
than the height value sensed at potentiometer 36,
processor 86 sets a flag for the "to height mode"
subroutine (step 266) and the lower feeder subroutine is
called (step 268). The lower feeder subroutine sets the
width of the pulses applied to valve 32 for lowering
implement 22 based upon pressure or position error or a
21 698~5
fixed width based upon the setting of generator 56 when
in the manual mode.
If switch 48 is not set to the height mode or the
desired height value is greater than the height value
representative of the signal from potentiometer 36,
processor 86 executes step 270. In step 270, if switch
48 is set to the float mode, if the soft lower flag is
set, and if the desired float value produced by generator
52 is less than the sensed float value produced by
transducer 38, processor 86 sets a flag for the "to float
mode" subroutine (step 272) and the lower feeder
subroutine is called (step 268). It should be noted that
the sensed float valve referred to here corresponds to
the pressure in cylinders 40 reguired to support
implement 22. Thus, lowering implement 22 has the effect
of lowering the sensed float value by allowing implement
22 to be supported to a greater degree by surface 23. If
switch 48 is not set to the float mode, or the desired
float value is greater than the value representative of
the signal produced by transducer 38, processor 86
executes step 274.
In step 274, processor 86 determines if switch 48 is
set to the RTC mode, if the soft lower flag is set, and
if the desired position value representative of the
signal produced by generator 50 is less than the feeder
position value representative of the signal produced by
potentiometer 34, processor 86 sets the control position
subroutine flag (step 276) and the lower feeder
subroutine is called (step 268). If any of the
conditions in step 274 are not true, processor 86
defaults to the manual mode and samples the status of
switch 58 to determine if switch 58 has been toggled to
the raise or lower position (steps 278 and 280). If
switch 58 is in the raise position, the raise feeder
subroutine is called (step 282), and if switch 58 is in
the lower position, the lower feeder subroutine is called
21 6~885
- 20 -
(step 284). The raise feeder subroutine sets the width
of the pulses applied to valve 32 for raising implement
22 based upon position error, or a fixed width when in
the manual mode.
While system 24 is operating in the return to cut
mode, and implement 22 is operating in the position
selected for cutting, as represented by the signal
produced by generator 50, the "control position"
subroutine is executed by processor 86. In step 286,
processor 86 begins executing the "control position"
subroutine. In step 288, switch 58 is sampled to
determine whether or not the operator is attempting to
manually control the location of implement 22. If switch
58 has been operated, processor 86 goes into the manual
mode and executes a combination of steps 278, 280, 282
and 284 (step 290). If switch 58 was not operated,
processor 86 calculates the difference between the
desired position value and the position value
representative of the signal generated by potentiometer
34 to produce a position error value (step 292). If the
position error indicates that implement 22 is too low
(step 294), the raise feeder subroutine is called (step
296). If processor 86 determines that implement 22 is
not too low (error high), processor 86 compares the
desired float sensor value to the float sensor value
representative of the signal produced by pressure
transducer 38 (step 298). If processor 86 determines
that the float error represents a float pressure lower
than the desired pressure (steps 300 and 302, again
referring to the pressure tending to raise implement 22),
the raise feeder subroutine is called (step 296). If
processor 86 calculates a float error which represents
that the float pressure is higher than the desired float
pressure (step 304), the lower feeder subroutine is
called (step 306). Upon completion of the control
position routine, switch 58 is again sampled by processor
86 (steps 278 and 280) and the raise and lower feeders
21 698~5
- 21 -
subroutines are appropriately called (steps 282 and 284).
(Steps 298, 300, 302, 304 and 306 provide float control
override of position control.)
The "to height mode" subroutine (step 308) is
entered when the height mode has been set in step 266 as
discussed above. In the "to height mode" subroutine,
switch 58 is sampled (step 310) and if the raised
position of switch 58 has been toggled, processor 86 goes
into the manual mode and executes a combination of steps
278-284 (step 312). In step 314, processor 86 determines
whether or not a setting is present in memory 100
representative of the position of implement 22 associated
with a particular height setpoint value (i.e. feeder
found flag is set) as determined in step 252. Upon
startup of vehicle 10, a position value associated with
the desired height value will not be present in memory
100. When a position value is not available (i.e. the
feeder found flag is not set), processor 86 determines
the difference between the desired height value
representative of the position of generator S0 and the
actual height value representative of the value produced
by potentiometer 36 (step 316).
In step 314, when a position value associated with
the height value is-not available, a flag is set by
processor 86 to reduce the size of the pulse widths
applied to AND gates 188 or 190. This is done so that
implement 22 is moved relatively slowly while being moved
toward the desired height. This prevents jerking of
implement 22 since skid 202, linkage 204 and
potentiometer 36 do not begin producing a meaningful
signal until skid 7.02 comes in contact with the ground.
In step 316, if the height value representative of the
signal at potentiometer 36 is greater than the desired
height value representative of the signal produced by
generator 50, the lower feeder subroutine is called (step
322). When the sensed height value is less than the
~1 6~
desired height value, the height mode flag is set (step
318).
If processor 86 determines that a position value
associated with the desired height value is stored in
memory 100, processor 86 calculates the error between the
position value representative of the signal produced by
potentiometer 34 and the position value associated with
the desired height (step 324). In step 326, the
processor calls the raise feeder subroutine (step 320) if
the error represents the location of implement 22 which
is too low for the associated height, and in step 328, if
the error is high, calls the lower feeder subroutine
(step 322). If the error is neither high nor low,
processor 86 sets the height mode flag (step 330). In
general, while running the "to height subroutine,"
processor 86 controls the operation of lift cylinders 40
using potentiometer 34 (i.e. position control) until
implement 22 is at a position within a range defined by
high and low error bands (e.g. within +1.5% to 2% of the
desired position) at which time processor 86 enters the
height mode subroutine (step 332) to begin controlling
the location of implement 22 relative to surface 23 based
upon the signal generated by potentiometer 36 (i.e.
height or location control).
The "height mode" (step 332) subroutine is entered
in response to processor 86 setting a height mode flag in
steps 318 or 330. In step 333 the feeder found flag is
cleared. In step 334, processor 86 determines whether or
not switch 58 has been toggled to the raise position. If
switch 58 has been toggled to the raise position, then
processor 86 goes into the manual mode (step 336) and
sets the feeder position value associated with the
desired height stored in memory 100 to the position value
representative of the signal produced by potentiometer 34
(step 338). In step 340, processor 86 sets a feeder
found flag which is tested by processor 86 in step 314 to
21 6q885
- 23 -
determine whether or not a position value representative
of the desired height is stored in memory 100. In step
334 if switch 58 has not been toggled to the raise
position, processor 86 determines if switch 58 has been
toggled to the lower position (step 342). If switch 58
has been toggled to the lower position, the lower feeder
subroutine is called in step 284. If switch 58 has not
been toggled to the lower position, processor 86 samples
the height value representative of the signal produced by
potentiometer 36, compares this actual height value to
the desired height value representative of the signal
produced by generator 50, and calculates a height error
value (step 344). If the error value indicates that
implement 22 is too low, the raise feeder subroutine is
called (step 346 and 348), if the error signal indicates
that implement 22 is too high, the lower feeder
subroutine is called (steps 350 and 352). If the error
calculated is between the low error value (step 346) and
the high error value (step 350), processor 86 does not
call either the raise or lower feeder subroutines. After
steps 340, 342, 348 or 352 have been executed, processor
86 samples the status of switch 58 at steps 278 and 280,
and returns to the start of the program (step 254).
The "to float mode" subroutine (step 356) is entered
in response to the setting of the "to float mode" flag at
step 272 discussed above. In the "to float mode," switch
58 is sampled (step 358) and if the raised position of
switch 58 has been toggled, processor 86 goes into the
manual mode and executes a combination of steps 278-284
(step 360). In step 362, processor 86 determines whether
or not a setting is present in memory 100 representative
of the position of implement 22 associated with a
particular float setpoint value (i.e. checks the float
feeder found flag). (Upon startup of vehicle 10, a
position value associated with the desired float value
will not be present in memory 100.) Where a position
value is not available, processor 86 determines the
21 6~8~5
- 24 -
difference between the desired float value representative
of the position of generator 52 and the actual float
value representative of the signal produced by pressure
transducer 38 (step 364).
S In step 362, when a position value associated with
the float value is not found (i.e. float feeder found
flag set), a flag is set by processor 86 to reduce the
size of the pulse widths applied to AND gates 188 or 190
during the execution of the lower feeder flag subroutine.
This is done so that implement 22 is moved relatively
slowly while being moved toward the desired float
pressure. This reduces jerking of implement 22 since the
float value representative of the signal produced by
transducer 38 changes abruptly when bottom 206 of
implement 22 comes in contact with the ground. If the
sensed float value is greater than the desired float
value, the lower feeder subroutine is called (step 368).
In step 364, if the float value representative of the
signal at transducer 38 ("sensed float value") is less
than the desired float value representative of the signal
produced by generator 52, the float mode flag is set
(step 366).
If processor 86 determines that a position value
associated with the desired float value is stored in
memory 100 (i.e. float feeder found flag set), processor
86 calculates the error between the position value
representative of the signal produced by potentiometer 34
and the position value associated with the desired float
value (step 370). In step 372, processor 86 calls the
raise feeder subroutine (step 374) if the error
represents the location of implement 22 which is too low
for the associated float value. In step 376, if the
error is high, the processor 86 goes to step 368 to call
the lower feeder subroutine. If the error is between the
high and low limit values, processor 86 sets the float
mode flag (step 378).
2 1 6q885
In general, while running the "to float mode"
subroutine, processor 86 controls the operation of lift
cylinders 40 using potentiometer 34 until implement 22 is
at a position within a range defined by the high and low
error values associated with the selected float pressure.
Subsequently, processor 86 can enter the "float mode"
subroutine to begin controlling the location of implement
22 relative to surface 23 based upon the signal generated
by transducer 38 (float control).
The "float mode" (step 380) subroutine is entered in
response to processor 86 setting a float mode flag in
steps 366 or 378. In step 381 the float feeder found
flag is cleared. In step 382, processor 86 determines
whether or not switch 58 has been toggled to the raise or
lower position. If switch 58 has been toggled to the
raise or lower position, then processor 86 goes into the
manual mode (step 384) and sets the feeder position value
associated with the desired float to the position value
representative of the signal produced by transducer 34
(step 386). Processor 86 then sets a float feeder found
flag (step 388) which is tested by processor 86 in
subsequent loops through the program at step 362 to
determine whether or not a position value associated with
the desired float value is stored in memory 100.
If switch 58 has not been toggled, processor 86
samples the float value representative of the signal
produced by transducer 38, compares the float value to
the desired float value representative of the signal
produced by generator 52, and calculates a float error
value (step 390). If the error value indicates that
implement 22 is too low (i.e. that the pressure currently
exerted to support implement 22 is too low), the raise
feeder subroutine is called (steps 392 and 394), if the
error signal indicates that implement 22 is too high
(i.e. that cylinders 40 are currently supporting
implement 22 to an extent greater than desired), the
21 69885
- 26 -
lower feeder subroutine is called (steps 396 and 398).
If the error calculated is between a low error value
(step 392) and a high error value (step 396), processor
86 does not call either the raise or lower feeder
subroutine. After processor 86 samples the status of
switch 58 at steps 278 and 280, processor 86 returns to
the start of the program (step 254).
Upon reaching step 354 (Figure 4D), processor 86
will have calculated a pulse width, and stored the values
of the pulse width in memory 100. The maximum width of
the pulse width value for raising and lowering implement
22 via the control of lifting cylinders 40 by control
valve 32 is determined by processor 86 from the digital
values representative of the settings of generators 54
and 56, respectively. Based upon the range of pulse
width values available for controlling the speed of
raising and lowering and the error signal, processor 86
calculates the raise or lower pulse width values when the
raise and lower feeder subroutines (steps 282 and 284)
are called. Thus, for a very high error signal values,
processor 86 will use the maximum pulse width values, and
for an error signal value approaching zero, processor 86
will use a relatively short duration pulse width values.
Each time processor 86 goes through the control
sequence represented in FIGURE 4 and reaches step 354,
the pulse width modulated signal having a width
calculated when the raise or lower subroutine is called,
is applied to the appropriate AND gate 188 or 190
depending upon whether or not implement 22 is to be
raised or lowered. If implement 22 is to be raised, AND
gate 188 is pulsed by processor 86 to drive coil driver
184 which pulses valve solenoid 80 of valve assembly 32
to pressure lift cylinders 40 and thereby raise implement
22. If implement 22 is to be lowered, processor 86
applies a pulse width modulated signal to AND gate 190
which applies the pulse width signal to coil driver
21 6~885
- 27 -
circuit 186 which pulses valve solenoid 82 of valve
assembly 32 to allow hydraulic fluid to flow from lift
cylinders 40 and thereby lower implement 22. Subsequent
to pulsing the appropriate gate 188 or 190, processor 86
goes back to step 250 and executes the control sequence
represented in FIGURE 4.
It will be understood that the description above is
of the preferred exemplary embodiment of the invention
and that the invention is not limited to the specific
forms shown and described. For example, the control
system is disclosed in reference to a grain harvesting
device; however, the system may also be utilized with
other harvesting devices such as cotton pickers.
Furthermore, depending upon the application, the various
communication links which are hardwired for data and
signal communication could be replaced with appropriate
wireless communication hardware. Another modification to
the system includes providing a potentiometer 36 and skid
arrangement 202 at both ends of implement 22 and coupling
the second potentiometer to an eight input multiplexer
96. Using this arrangement, processor 86 can be
programmed to monitor both potentiometers 36 and use the
signals from both potentiometers 36 to control the
location of implement 22. For example, processor 86 may
be programmed to generate a height value for implement 22
relative to surface 23 by (1) averaging the signals from
potentiometers 36, (2) using the greatest value from
potentiometers 36, or (3) using the lowest value from
potentiometers 36. Since implement 22 can typically be
over 30 feet long, and surfaces 26 can be relatively
uneven over such a width, implement 22 location control
can be improved by using more than one location sensor
such as discussed above. As a further modification, a
plurality of potentiometers (e.g. four) and skid
arrangements 202 could be spaced along implement 22,
where a logic circuit is coupled to the potentiometers
and only outputs the value from the potentiometer
21 69~5
- 28 -
associated with the lowest portion of implement 22 to
circuit 96.
Other substitutions, modifications, changes and
omissions may be made in the design and arrangement of
the preferred embodiment without departing from the
spirit of the invention as expressed in the appended
claims.
