Note: Descriptions are shown in the official language in which they were submitted.
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Description
PLANT ORIENTED CONTROL SYSTEM
1. Field of the Invention
This invention pertains to a plant oriented system for controlling
5 environmental conditions in greenhouses.
It relates in part to our IJnited States Patent No. 4,430,828, issued
February 14, 1984.
2. Background
Automatic closed-loop control of temperature in a greenhouse by
10 regulating heating and ventilation is old in the art. In fact, other factors
affecting the growth and health of the crops being grown in the greenhouse
have been automatically controlled. However, in the past control has been
directed to maintaining the overall greenhouse environment based upon a
small number of sensors and traditional control devices such as single
15 thermostats. Thus prior greenhouse control systems have not been plant or
crop oriented control systems. They have not addressed the problems of
controlling growth and plant health conditions directly at the growing bed or
plant level. Unfortunately, the control of the overall greenhouse conditions,
while providing adequate plant growth and health conditions at one bed, may
20 not provide the proper conditions at another bed. This may be due to the
nonuniformity of a condition, say temperature, throughout the greenhouse or
the fact that different beds are planted with different crops or even that
different beds planted with the same crop are at different stages in the
growing cycle. Prior greenhouse control systems huve not provided adequate
25 individualized control of bed areas based upon feedback of temperature,
light, and humidity conditions directly over the beds.
Irrigation and/or misting are the open-loop controlled application of
moisture to the crop or the soil. Irrigation and/or misting of greenhouse
crops based upon estimated evapotranspiration has been proposed but the
30 approach has been crudely implemented and/or not crop oriented. Also, only
irrigation or misting was controlled ignoring the other controllable para-
meters affecting growth. See, for example, "Mist Control Plus" Operations
Manual, Oglevee Computer Systems, "Effects of Different Irrigation Methods
and Levels on Greenhouse Musk Melon" ACTA HORTICULTURAE 58 (1977)
35 and "Scheduling Irrigations with Computers" Journal of Soil and Water
Conservation, September-October 1969.
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,,
Summary of the Invention
It is an object of this invention to provide a computerized plant
oriented control system or method for control of the greenhouse environment
including open-loop control of irrigation or misting rate and, for example,
5 closed-loop control of temperature, light, and/or carbon dioxide con-
centration.
It is another object of this invention to provide an automated plant
oriented control system or method for programming growth rates by
maintaining the irrigation rate and one or more conditions such as
10 temperature and carbon dioxide concentration in the atmosphere over the
beds as a function of the available light and/or controlled amount of light
incident the crop bed.
It is an object of one embodiment of this invention to provide a
computerized plant oriented control system or method that, as a function of
15 light, and humidity over the beds and the physiological age of the crops,
provides the amount of irrigation necessary to insure healthful propagation
and growth of the crop.
It is an object of this invention to provide a computerized open-loop
plant oriented control system for misting or irrigating greenhouse plants
20 wherein the frequency of moisture application is related to the light incident
the crop bed, the relative humidity above the crop bed and a measure of the
physiological age of the crop.
- It is a feature according to this invention that a greenhouse has a
plurality of sensing zones and a plurality of irrigation (or misting) control
25 zones and wherein each sensing zone is provided individualized environmental
control based upon its particular needs. The system includes components that
collect data such as temperature, light, humidity, wind speed and direction.
A central microcomputer unit uses the data obtained to make decisions and
act upon them. The microcomputer is programmed with one or more
30 algorithms to make the decisions- The algorithms may be modified depending
upon the nature of the crop and the greenhouse system being controlled. The
plant oriented control system provides a fully automated greenhouse
environment with the ability to monitor and control all applicable conditions.
In its broadest expression, the computerized plant oriented control
35 system comprises structure defining a plurality of sensing zones, structure
defining a plurality of irrigation control zones and a microcomputer
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programmed with algorithms or tasks for maintaining irrigation (or misting)
rate and at least one other controllable parameter affecting growth in the
control zones to promote the health and growth of the crop or crops. For
those embodiments which relate to anticipatory control condition, sensors
5 remote from the bed such as external temperature, wind speed and wind
direction sensors are required. The microcomputer must include a real time
clock.
As the terms are used herein, a "sense zone" or "sensing zone" is a
bed area, preferably not in excess of about 3,000 square feet all planted with
10 the same crop at about the same time having at least two spaced
temperature sensors positioned directly over and near (within about three
feet) of the bed, a light sensor directly over and near the bed and an
aspirated humidity sensor directly over and near the bed. As used herein,
various "control zones" may include a heating control zone, cooling control
15 zone, misting control zone, irrigating control zone, shade control zone, heatretention control zone, horizontal flow control zone, and carbon dioxide
atmosphere control zone. Each control zone has associated with it a
controllable device for affecting the environment within the zone. A heating
control zone comprises a bed area, including at least one sensing zone, that
20 has a controllsble heating element associated therewith. A cooling control
zone comprises a bed area, including at least one sensing zone, that has a
controllable cooling system associated therewith. This may simply be a cross
ventilation pathway controlled by one or more vents. A misting control zone
comprises a bed area, usually one sensing zone, having controllable water
25 spray over the bed. An irrigating control zone comprises a bed area, usually
one sensing zone, having a controllable bed watering system. A shade control
zone comprises a bed area, including at least one sensing zone having a
controllable sunscreen or shade associated therewith. The shade control zone
might become a heat retention zone at night as radiative cooling can be
30 controlled by the presence or not of the screen or shade over the bed. A
horizontal flow control zone is a bed area, including at least one sensing
zone, that has a controllable horizontal circulation fan associated therewith
to prevent stratification when no ventilation is being used. A carbon dioxide
atmosphere control zone comprises a bed area, generally the entire enclosed
35 greenhouse, having means for generating carbon dioxide. lt should be noted
that the various control zones need not be contiguous but very often are
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overlapping. (For example, a large greenhouse may have two cooling zones
but many heating zones.) Controllable devices associated with the control
zones are devices which may be activated, for example, by application of an
AC current such as a solenoid control valve or an AC motor controlled by
5 a motor controller which controller provides the function of starting,
stopping, and reversing a motor.
As stated above, the microcomputer must be programmed with
algorithms or tasks to enable it to make intelligent decisions. According to
this invention, there is provided an algorithm for establishing irrigation rate
10 based upon an evapotranspiration predictor function.
An algorithm or task, at spaced intervals, inputs the digitalized light
intensity and wet bulb and dry bulb temperatures (two sets of data for each
bed) and averages the light data, temperature data for each bed or sense
zone.
The relative humidity is calculated îrom the temperature data.
Based upon a previously initialized function, an evapotranspiration counting
rate is established based upon the light data and relative humidity data. The
evapotranspiration count is then updated based upon the instantaneous
counting rate. When the count reaches a "maximum count" which is
20 preestablished and which is a function of a measure of the physiological age
of the crop, output control signals actuate controllable devices and thus the
crop is irrigated (or misted) to prevent moisture deficiencies. This will be
recognized as an open-loop control. In addition, at least one other parameter
affecting growth is preferably provided with a closed-loop control. For
25 example, the average temperature is then compared to a set point, for
example, a maximum temperature, a minimum temperature or the dew point.
Depending upon the relationship of the average temperature sensed and the
set point, the computer will output control signals to adjust the controllable
devices such a5 heating or ventilating equipment to adjust the temperature
30 relative to the set point temperature. Additionally, an algorithm may
maintain the temperature and carbon dioxide atmosphere as a function of the
available light to provide a desired growth rate and/or to make efficient use
of energy.
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The Drawin~
Further features and other objects and advantages of this invention
will become clear from the following detailed description made with
reference to the drawings in which
FIG. I is a schematic illustrating a greenhouse, sensing zones and
control zones according to this invention;
FIG. 2 is a flow chart for a main program useful according to this
invention; and
FIG. 3 is a flow chart for a subprogram useful for open-loop control
10 of misting or irrigation.
Detai~ed Description
The equipment for the plant oriented control system according to
this invention can be considered in three groups based upon their functions.
First there are the sensors. These collect greenhouse data such as
15 temperature, humidlty, light, and such external conditions as temperature,
light, humldity, wind speed and dlrection. A second group comprises the
microcomputer with associated input and output boards. A third group
comprises the valves and motors necessary to carry out the actions that
bring about a change in the greenhouse environment.
The grower must determine the number of control zones he intends
to include in his greenhouse. A zone is defined as one part of the total
greenhouse of which indlvidual, independent control can be maintained. The
type and location of existing equipment within a greenhouse determine the
establishment of control zones. Senslng zones and control zones have
25 already been described. Heating and coollng zones need not be related so It
is not necessary that they each have the same dlvision. For example, as a
practical matter, an acre of greenhouse may have sixteen heating zones but
only two cooting zones.
The crops in the adjacent sense zones within the same control zone
30 theoretically might require a controlled condition to be different. However,
due to the nature of crop requirements and the usual greenhouse control
configuration, this is seldom the case. With some planning of crop
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placement, the problem can be avoided. For example, most sense zones are
coincident with a control zone for heating (for example, hot pipes); misting
or irrigating. These are conditions that may vary from crop to crop. On the
other hand, ventilation zones usually span a number of sense zones. The
5 ventilation requirement is generally about the same for all crops.
Referring now to FIG. 1, the system hardware according to this
invention is shown schematically. The large rectangle represents the
greenhouse enclosure 10. Located within the greenhouse is a microcomputer
12 having associated A/D input sections and AC cutput (triac control)
10 sections. Two IO stations 14 and 15 are spaced from the microcomputer.
The IO stations have associated A/D input sections and AC output sections
identical with those directly associated with the microcomputer and, as will
be explained, they are functionally equivalent to those directly associated
with the microcomputer. All A/D input sections and AC output sections are
15 connected to the microcomputer by one common asynchronous serial address-
data-control pathway referred to in here as the data pathway (DPW). It is
possible that iO stations will be unnecessary in a small greenhouse. In fact,
for the number of sense zones illustrated in FIG. l, the A/D input systems
and AC output sections directly housed within the microcomputer would be
20 sufficient. The use of IO stations depends upon the number of sense zones
being monitored and the spacing thereof. It is desirable to reduce the length
of the sense input wires carrying analog signals and thus the additional lO
stations may be required.
The greenhouse of FIG. 1 is divided into eight sensing zones, each
25 having two sense stations a, b, over the bed. Sense stations are aspirated
enclosures for housing at least a dry bulb temperature sensor and often both
dry bulb and wet bulb temperature sensors and for generating an analog
signal indicative of these temperatures. A light sensing station for
generating an analog signal indicative of light intensity over the bed is often
30 associated with the temperature sensing station. A second temperature
sensing station is always associated with each sense zone. The two
temperatures are averaged by the microcomputer to obtain a temperature
representative of the sense zone temperature.
Referring again to FIG. 1, the greenhouse is further divided into a
35 number of control zones. For example, four zones labelled A, B, C, and D
have individually controlled heating and/or watering means. The heating
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means may comprise a number of possible devices, for example, on-off steam
heating below the beds, proportional hot-water heating below the beds,
infrared heaters above the beds or gas fired unit heaters above the beds. The
watering means may comprise pipes that spray a mist over the bed or pipes
that deliver water to the beds.
To illustrate that the control zones may overlap, two ventilation
control zones are illustrated; one extending to heating control zones A and
B and the other to heating control ~ones C and D. Ventilation may be by
opening vents on each side of the greenhouse or by turnin" on fans that draw
air across the ventilation zone. The intake vents may or may not have
evapol ation coolers associated therewith depending upon the application.
~hadé zones comprising canvas shades that are drawn horizontally over the
beds just below the rafters may be arranged in zones. In the example of FIG.
1, there are two shade zones comprisin~ control zones A und B and control
zones C and D. The shades are useful for two purposes: In the daytime, the
drawn shades reduce sunlight and temperature of the beds. At night the
shades help to maintain temperature over the beds by reducing radiation
cooling. Located above the shade is a light sensor 16 enabling the detection
of thc avuilability of sunlight when the shade is drawn.
To this point, all of the elements of the system being described are
positioned within the greenhouse enclosure. Two groups of optionfll elements
may be positioned external to the greenhouse. An external temperature
sensor, wind speed sensor, and wind direction sensor rnay be provided for
anticipatory control as v~ill be explained herein. Also a host computer for
26 downloading new control algorithms or tasks to the microcomputer May be
positioned external to the greenhouse.
Plant oriented control systems must gain an adcquate amoullt of
information from each zone to be able to make the proper decisions for the
correct levels of controi. Each 20ne contains at least two temperature
sensors, one light sensor, and one humidity sensor- The overbed sensors are
housed in aspirated fan bo~;es. A light sensor must be mounted close to the
roof away from shadows. The temperature sensors comprise solid-state dry
bulb temperature monitoring devices having a range -10C to 100C. The
humidity sensor is a solid-state wet bulb temperature monitoring device.
When used in conjunction with the dry bulb dcscribed above this provides a
very precise humidity rleasurement. 1'he light energy sensor meusures light
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intensity in foot candles. Two types of sensors are used. The first provides
very precise measurement of light in the range of 0 to 800 foot candles for
use with artificial day leng~th control. The second is a ~eneral daylight sensorthat provides less resolution in a much wider photosynthetic range of ~ to
5 4,UU0 foot candles; that is, the range at which actual plant growth occurs.
Typically the temperature sensors comprise a heat sensitive diode, say,
LM335 with associated caiibration potentiometers. They are commercially
available calibrated for a 2.73 volt output in ice water and a 10 millivolt per
degree Kelvin output.
To provide more efficient control, conditions outside of the green-
house are also monitored. This enables the plant oriented control system to
anticipate the greenhouse needs prior to any internal changes and also aids
in conserving energy. A tcn-mile per hour wind speed increase increases the
heating load approximately fifteen percent.
The microcomputer comprises a micloprocessor, RAi~l mernory, ROi~l
memory, a 1~-piace keypad input and an ~-digit display, for example. The
computer is enclosed within ùn air-tight cabinet; preferably protected from
both direct sunlight and other tempera-ture extremes. Cornputers are
available at rated operating temperatures between 0 und 70C (32 and
~0 15~P). Operational greenhouses have an internal temperature well within
this range.
'I'he sellse sectio.ris of the rnicrocomputer, whether in the same
cabinet or in an IO cabinet spaccd therefrom, collects analog data from the
above mentioned sensory elements wld converts it to a digital signal with an
:~S ~nalo~ to digital signal converter.
l~eferring now to FIG. 2, a flow chart for thc mahl prograrn is set
forth. 'l'hc proglllm passes se~luentially îrom all initialization routine through
a data gathering procedure and through n tempcrature udjusting procedure
that ure repcatea for each control zone and thence through a plurality of
30 procedures that are not necessariiy zone spccific.
After the initializatioll (progrummillg of ports and clearing oï
memory areas, etc.) which only tal~es place upon start-up or r eset, the
pr(jgraln moves to the main line loop.
The initialization routine ulso includcs <iircct l~eyboard or host
3S computer inputs ol certain proccss constunts that enuble the customization
of thc system to pnrticular crops.
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After initialization the main line of the program is entered.
Referring to FIG. 2, the îirst step in the main line is labeled "sense" and
comprises the irlput of digitized data from all sense zoMes and preprocessing
of the data (for example converting wet bulb and dry bulb temperature to
5 relative humidity). The next step, labeled "alarms" is to compare the data
to threshold values for which alarms should be activated to call attention to
dangerous or potentially catastrophic conditions; for example, loss of heat in
the winter months. The next step comprises referring to each control zone
and adjusting the controls for that zone. As shown in ~IG. 2, the closed-loop
10 controls are first implemented and then the open-loop irrigation or misting
controls are implemented. When the controls have been implemented in all
zoncs, certain set point driver routines are performed, the physiological age
accumulator is updated and the main line is restarted either immediately or
following a programmed delay. For a description of the set point drivers
15 reference is made to our above noted patent.
Referring now to ~IG. 3, there is shown a subtask for irrigating or
misting. The first step is to access the light intensity and relative humidity
for the zone in question. This data was input in a previous step and stored
in a temporary memory location. The data is used to generate an adjusted
20 counting rate which is specific to the crop in the zone being considered.
Thereafter, the addition to the total count is made based upon the length of
time since the last update and the adjusting counting rate. At this point, the
total COUllt is compared to the count required for irrigation or misting
(referrcd to as "maximum count"). If the count exceeds maximum COWlt then
25 irrigation is initiated and the count is reset to zero. This open-loop misting
or irrigating applies moisture at intervals throughout the day and into the
night. Typically, the duration of the period of the mist or irrigation is fixed
and the nozzles are adjustable so that the amount of water applied each time
is the same. This is consistent with the established greenhouse practices.
30 Misting takes place until an adequate moisture coating e,Yists over the foliage
of the crop. Irrigating takes place until a run-off of from ~ to 20 percent
is achieved. Again, the volume of watcr is controlled by the no~zle setting
or throttle setting in the water supply.
The daytime frequency of the open-loop misting or irrigating is
35 controlled by at least three factors, the light intensity, the relative humidity,
and the age of the crop (prcferably the physiological age, not the
chronological agej.
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The particular algorithm used by the applieants herein is designed to
be easily adapted to a partieular erop aeeording the grower's aequired
experience for manually misting or irrigating the erop. The light intensity
(photocell output) is eonverted to a counting rate. The conversion factor is
5 based upon a number of eonstant parameters and the relative humidity. The
eonstant parameters are a maximum eounting rate (CRmaX)~ a maximum
light level or photocell output (LLmaX) corresponding to that light level, and
a minimum counting rate (CRmin), and finally a minimum light level (LLm~
corresponding to that level. The four constant inputs (CRma~C, LLma2~,
10 CRmin, and LLmjn) may be thought of as two ordered pairs establishing the
linear funetion between light level and eounting rate over the expeeted range
of light LLmin to LLmaX (reeall that two points establish the graph of a
straight line function). The above described constant faetors are entered on
the assumption of a eonstant relative humidity, say 50 pereent.
The linear funetion is then modified by a slope adjustment based upon
relative humidity (recall that a linear funetion ean also be defined by a point
and a slope). The eonstant input required are minimum relative hurmidity
(RElmin), maximum relative humidity (E~Hma~y)~ and proportional
inerease ~ at the maximum eounting rate from Rllmin to R~lmaX~ From the
20 three faetors (RHmin~ RHmaX~ and ~ ), the ehange in the slope eorresponding
to a speeific relative humidity can be ealculated.
A counter is incremented at the counting rate until a preselected
eount ("maximum eount"~ between irrigating~ or misting times is obtained. As
soon as a preseleeted eount is reaehed, misth7g or irrigating is initiated and
25 the eount is reset to zero.
The eounting rate may also be adjusted by factors such as outside
temperature and whether or not the crop beds are being heatcd to still bettcr
approximate the evapotranspiration rate.
The frequency of the misting is adjusted by adjusting the
30 preseleeted count ("maximum count") between mistings aeeording to the age
of the crop. This ean be aeeomplished in two ways. The erop age may be
taken as a chronologieal age in which case the preselected count is adjusted
daily. This requires the following preoperating inputs: counts between
mistings Cs on the first day, number of days 1) on which the count is to be
35 adjusted, and counts between mistings Cf on the final day. Thus, the
maximum eount is adjusted at a lineal rate day-by-day. (A more eomplicated
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algorithm in which the rate of adjustment is an exponential function can also
be implemented.) This procedure for increasing the frequency of misting or
irrigation with crop aids is suitable in some applications; however, the
frequency should be adjusted according to the crops physiological age.
A better measure of the physiological age than chronological age is
the accumulated counts (same counts used to establish irrigation at
"maximum count"). This requires the operator input of the number of counts
in a light day (CLD). Every time the accumulated counts reaches CLD,
"maximum count" is adjusted.
It should be understood that the maintenance of the proper mist (in
the case of unrooted cuttings) or the proper irrigation (in the case of rooted
crops) is necessary to prevent environmental moisture deficiencies. Should
there be a deficiency, the growth rate is reduced. It should also be
understood that excessive misting or irrigation can result in damage to the
crop through leaching. Even a slight excess can result in reduction of the
growth rate due to leaching of nutrients from the crop.
After sunset and for a period of several hours, it is necessary to
continue misting or irrigating at fixed intervals. Thus it is preferred that
there be a task for establishing the times of sunrise or a sunset based upon
the latitude and longitude of the greenhouse being controlled. It is also
necessary to set a fixed interval, say 60 minutes, between mistings and the
number of mistings to follow sunset, say four.
As used in the following claims, watering refers to either irrigating
or m isting.
Having thus described the invention in the detail and purticularity
required by the Patent Laws, what is desired protected by Lettels Patent is
set forth in the f ollowing claims.
