Effect of Operating Parameters on Performance of Target Actuated Sprayer Abstract

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VOL.46 NO.4 2015 AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 81
Effect of Operating Parameters on Performance of
Target Actuated Sprayer
Abstract
Chemical pesticides have played
and will continue to play a major
role in the rapid a dvancement of
ag ricultural produ ction. In crop
spraying, off target application re-
sulting in air and soil pollution has
to be reduced. Hence an attempt has
been made to develop a target actu-
ated sprayer to reduce the off target
application of chemical and thereby
soil and environmental pollution.
The different parameters taken for
this study are concentration of the
spray, width of plant canopy, height
of the sensor from the canopy and
forward speed of operations. Opti-
mization test were also conducted
by using different connectors name-
ly ‘T’ joint, ‘Y’ joint, non-return
va lves and with fou r models of
eductors. From the observations, it
is concluded that eductor model IV
was found to be the best connector
with mixing chamber for the chemi-
cal and car rier liquid. The range
of pressures adopted for chemical
and carrier liquid produced droplets
with VMD and NMD ranging be-
tween 101 to 200 μ and VMD/NMD
ratio of 1.09 to 1.29 which is clas-
sified as fine spray. The amount of
chemical delivered decreased with
the increase in forward speed and
height of sensor and with decrease
in chemical concentration while it
increased with increase in simula-
tion plate width. The Analysis of
Variance for optimum amount of
chemical delivered as inuenced by
concentration of chemical, width of
simulation plate, height of sensor
above the plant canopy and forward
speed of operation indicated that
the selected variables and their in-
teractions signicantly affected the
amount of chemical delivered. The
mean compa rison tests indicated
that the minimum amount of chemi-
cal delivered (499 μl) was achieved
at a chemical concentration of 25
percent, 100 mm width of simula-
tion plate, 3.5 km h-1 forward speed
and sensor height of 300 mm above
the plant c a nop y. A p redic tion
model on the amount of chemical
delivered was developed based on
multiple linear regression analysis
(q = − 707.1769461 + 70.08855205C
+ 16.13430133W − 809.1538611S).
The analysis of variance of lag time
indicated that the selected variables
and their interactions significantly
affected the amount of chemical
delivered at one percent level. The
minimum lag time of 1 ms was ob-
ser ved for the combination of 100
mm width of simulation plate for-
ward speed of 3.5 km h-1 and sensor
height of 300 mm above the plant
ca nop y.
Keywords: off target spraying,
target actuated sprayer, spray drop-
let size, and spray deposition.
Introduction
In crop spraying, off target ap-
plication resulting in air and soil
pollution has to be reduced. Off-
targe t ch emica l application is a
costly and time consuming problem
for agricultural producers and turf
grass managers. Application prob-
lems include: skipped areas, double
application, unintentional applica-
tion, or application to environmen-
tally sensitive areas. Reducing or
eliminating off-target application is
increasingly important in a society
that places high value on environ-
mental quality and in global mar-
kets that are extremely competitive.
Targeted application of chemicals
provides an economic benet in that
less material is applied and a cor-
responding environmental benef it
with less chemical introduced to the
environment. It is known that spray-
er settings are important for spray
distribution in crop canopy. Match-
ing spr ay volum e and d irection
to crop size and shape can reduce
by
Jayashree. G. C.
Assistant Professor,
Department of Agricultural Engineering
University of Agricultural Sciences
Bangalore- 560065. INDIA
jayashreegc@gmail.com
D. Anantha Krishnan
Professor,
Department of Farm Machinery
Agricultural Engineering College
and Research Institute,
Tamil Nadu Agricultural University
Coimbatore- 641 003. INDIA
tnauananth@yahoo.com

AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 2015 VOL.46 NO.482
chemical application, thus reducing
operational costs and environmental
pollution. Manual or sensor actu-
ated sprayers have shown potential
reductions in agrochemical use of
30 % and more. Hence, there is a
need to develop technologies that
automatically detect the presence of
target plants and actuate the device
to apply the pre-determined dose of
pesticide.
Review of Literature
Azimi et al. (1985) investigated
the nozzle spray distribution for
pesticide broadcast application, with
sp ray table (patternato r) having
troughs to measure the distribution
across the sprayed swath from sin-
gle nozzle. It was reported that the
distribution pattern was dependent
on the nozzle type, nozzle pressure,
height of the nozzle above the target
surface and the angle at which the
noz zle was oriented wit h respect
to the motion of the sprayer. Solie
and Gerling (1985) reported that the
nozzle height must be considered in
order to achieve uniform coverage
or distribution across the swath of
the boom nozzle.
Wang et al. (1995) investigated
the effect of nozzle height on uni-
formity of spr ay distribution . A
laboratory set up including a simu-
lated boom sprayer system and a
spray deposition measuring system
were used for the study. It was ob-
served that the nozzle height had
a strong effect on spray distribu-
tion uniformity. The width of plant
canopy is the parameter that decides
the width of spray to be applied on it
such that the width of spray should
go inside the average width of plant
canopy to get maximum coverage.
(Speelman and Jansen, 1974 and
Giles and Comino, 1989). Whitney
et al. (1989) examined the effect of
ground speed (1.6, 2.8 and 4.0 km
h-1) on upper and lower leaf surface
deposition using different air blast
spr ayers and sp ray volume and
stated that the speed of operation
signif icantly increased deposition Fig. 1 Different models of eductors (I, II, III, IV).

VOL.46 NO.4 2015 AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 83
on the upper leaf surface, but not on
the lower leaf surface.
Materials and Methods
The concentration of spray chemi-
cal is decided by the pressures at
which the chemical and the carrier
liquid are delivered to the mixing
chamber and mixed. These pres-
sures also decide the discharge rate
of the spray and the distribution of
droplet size. Hence the pressure in
the chemical tank and pressure in
the carrier liquid tank are to be opti-
mized with respect to the discharge
rate and the droplet size distribution
at desired concentration level. The
different parameters taken for this
study are concentration of the spray,
width of plant canopy, height of the
sensor from the canopy and forward
speed of operations.
Measurement of Discharge Rate
An experimental test rig was de-
veloped to measure the discharge
rate at different pressure combina-
tions of chemical and carrier liquid.
The different levels of pressure ad-
opted were 0.05, 0.1, 0.15, 0.2, 0.25,
0.3 and 0.35 MPa in both tanks. Dif-
ferent combinations of chemical and
carrier liquid pressure were adopted
to get pressure differences of 0.00,
0.05 and 0.1 MPa between chemical
and ca rrier liquid. The discharge
(v) for each pressure difference was
collected for a known time (t) and
the rate of discharge (q) was calcu-
lated as
q = v/t, L s-1 ............................... (1)
From the discharge rate the appli-
cation rate (Q) was calculated as,
Q = 36000q / (S × w) × 104, L
ha-1 ......................................... (2)
Where ,
Q: application rate, L ha-1
q: discharge rate, L s-1
S: speed of operation, km h-1
w: row to row spacing, m
Optimization of Pressure of Car-
rier and Chemical Liquid
Optimization of pressure is very
impor tant for ach ieving de sired
combination to get particle size and
mixing of carrier and chemical in
recommended proportion. Optimi-
zation tests were conducted by us-
ing different connectors namely ‘T’
joint, ‘Y’ joint, non-return valves
and educators of various models (I,
II, III, IV) shown in Fig. 1.
Optimization of Spray Concentra-
tion
Mix ing ratio of ch emical a nd
water at dif fere nt pressures will
indicate the concentration of chemi-
cal achieved. Spraying concentrated
chemical without dilution is danger-
ous and it results in scorching of
leaves. Pre-dilution of chemical is
based on stage of the crop and the
recommended dosage. Pre-diluted
chemical is again mixed with carrier
at the time of spraying. To achieve
proper mixing of carrier and chemi-
cal with difference in pressure, con-
nector was designed.
Droplet Size Determination
The size of spray droplet is the
most important parameter that in-
fluences penetration and car rying
ability of hydraulic sprayer. It also
influences the eff iciency of catch
of sprays by plant surfaces and in-
sects. Droplet size also affects the
uniformity and completeness of
coverage on plant surfaces and drift
of the material from the treated area
(Kepner et al., 2000; Farooq et al.,
20 01, Se nthil Kumar, 1995).The
uniformity of spray deposition was
expressed as VMD (Volume Median
Diameter), NMD (Numeric Median
Diameter) and VMD/NMD ratio.
Volume Median Diameter (VMD)
VMD is the diameter of spray
droplet which divides the volume of
the droplets deposited on the photo-
graph paper into two equal halves.
In other words, it is the diameter of
the spray droplet, which divides the
droplet spectrum into two halves
where the tot al volu me of spr ay
droplet which is smaller in size,
will equal the total volume of spray
droplets which are larger in size.
Numeric Median Diameter (NMD)
NMD i s the average d iameter
of the droplet, which divides the
number of droplets into two equal
halves. In other words it is the diam-
eter of the spray droplet, which di-
vides the droplet spectrum into two
halves where, the total number of
spray droplets which are smaller in
size will equal the number of spray
droplets which are larger in size.
VMD/NMD ratio
VMD/NMD ratio is a factor used
for indicating the breadth of the
spectra. For unifor m distribution
of spray particles the VMD/NMD
ra tio should equal to unity. The
VM D/ NMD ratio was calculated
from NMD and VMD obtained in
the droplet size measurements.
The droplet size was determined
by measuring the diameter of circles
formed by droplet deposition on
multilayer microporous ink –re-
ceptive white photographic paper.
Methylene blue solution was used
as the dye solution, at the rate of
10 g L-1. The photographic paper
was cut into (70 × 70) mm size. The
photographic paper was kept on a
hor izontal surface directly below
the nozzle. The target was enclosed
in a ring and covered by a top sheet.
Plant Sensors
Sensing of plants mainly depends
on the spectral properties of plants.
An optical sensor is an electronic
component that detects the presence
of visible light, infrared (IR) trans-
mission, and/or ult raviolet (UV)
energy. Optical sensors consist of
semiconductor having a propert y
called photoconductivity, in which
the electr ical conductance va ries
depending on the intensity of radia-
tion striking the material. Sensing
of crops can be done by using dif-
ferent types of sensors and in this
study optical sensor was used. The
Equinox optical sensor is PNP type,
working on 10 to 30 V DC battery.
The optical sensor will sense the

AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 2015 VOL.46 NO.484
object when the obstruction comes
in front of the sensor. The sensing
distance ca n be adjusted from 10
mm to 400 mm.
Width of Plant Canopy (W)
The width of plant canopy decides
the actuation period of the sensor
which in turn controls the duration
of spray on that particular plant. The
minimum width of plant canopy was
90 mm and the plant to plant spac-
ing in a row was 300 mm. Hence the
levels of variables is xed between
100 mm and 250 mm with an incre-
ment of 50 mm. Articial targets in
the form of simulated green colored
plates of width 100 mm, 150 mm,
200 mm and 250 mm corresponding
to the width of plants were used in
the lab set up for optimization.
Height of Sensor from the Canopy
(H)
The machine vision sensing sys-
te m was use d to sen se t he plant
canopy and produce a signal which
activated an electrically operated
soleno id va lve th roug h a r elay
switch to switch between ON/OFF.
A non-contact type 10 to 30 V DC
Equinox optical sensor of PNP type
was used to sense the plant material
which interferes with in its sensible
range which is shown in Fig. 2. A
12 volt battery was used to energize
the optical sensor. Infrared proxim-
ity switches work by sending out
beams of invisible infrared light.
A photo detector on the proximity
switch detected any reflections of
this light. These reections allowed
infrared proximity switches to de-
termine whether there was an object
nearby. Since the maximum range
of the IR sensor used in this study
was 350 mm, the levels of variable
selected namely height of the sen-
sor from the plant canopy were 100,
150, 200, 250 and 300 mm only. A
height adjustable frame was devel-
oped to hold the sensor and also to
adjust the heights between the plant
and sensor and widths based on the
row spacing which is shown in Fig.
3.
Forward Speed of Operation (S)
The va riation in forward speed
of operation inuences the duration
of sensor ac tivation, the amou nt
of spray and in turn the amount of
chemical deposite d on the plant.
The minimum speed of tractor in
the field can be 1.5 km h-1 wh ile
the maximum eld speed of tractor
can be 4 km h-1. Hence the levels of
forward speeds of operation were
selected from 1.5 to 3.5 km h-1 with
an increment of 1.0 km h-1.
Development of Prototype Target
Actuated Sprayer
The pa ramet ers such a s travel
speed, height of sensor and the pres-
Fig. 2 Non-contact type 10 to 30 V DC
Equinox optical sensor.
Fig. 3 Sensor is xed to
the Adjustable frame.
Fig. 5 Developed Target actuated sprayer.
Fig. 4 Schematic diagram of the target actuated sprayer.

VOL.46 NO.4 2015 AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 85
sure of carrier liquid and chemical
were optimized based on the obser-
vations of the experimental set up to
give desired chemical deposition on
the plant canopy. These optimized
values were used for the develop-
ment of prototype target actuated
sprayer.
The schematic diagram and pro-
toty pe target act uated sprayer is
shown in Figs. 4 and 5. The rotary
power to drive the hydraulic pumps
of the prototype was taken from the
PTO of the tractor while the electri-
cal power required for operating the
solenoid valve and the sensors was
taken from the battery of the trac-
tor. The prototype target act uated
sprayer consisted of the following
major components like main frame,
single acting pump, double acting
pump, carrier liquid tank, chemical
tank, sensor, solenoid valve, educa-
tor, nozzle, spray boom with height
adjustment and power transmission
system
Results and Discussion
The pre ssu re of che mical and
that of carrier liquid determines the
concentration of spray. These pres-
sures also decide the discharge rate
and the droplet size dist ribution.
The pressure in the chemical tank
and the pressure in carrier liquid
tank were optimized with respect
to discharge rate and droplet size
distr ibution. The outlets from the
chemical and carrier liquid were
connected using T joint, Non return
valves, Y joint and the eductor and
the discharge from both the tanks
were measured and the results were
tabulated.
The pressure of carrier and chem-
ical liquid for getti ng maximum
discharge using different connectors
namely T joint, Non return valves,
Y joint and the eductor were varied
for getting pressure difference of
0.0, 0.05 and 0.1MPa and the corre-
sponding total discharge and chemi-
cal contribution were measured and
tabulated. From the tabulated values
it was observed that a higher chemi-
cal concentration of 49 percent at
0.0 MPa pressure difference, 39 to
40 percent at 0.05 MPa pressur e
difference and 23 to 25 percent at
0.10 MPa pressure difference was
achieved with eductor model I V.
Since the inner volume of the educ-
tor was drastically reduced, there
was no accumulation of the liquid in
the eductor. Hence the discharge of
chemical stopped instantaneously at
the moment of cut off by the chemi-
cal solenoid. Hence eductor model
IV has been selected as the con-
nector and mixing chamber for the
chemical and carrier liquid.
Droplet Size Distribution
The droplet size was determined
by measuring the diameter of circles
formed by droplet deposition on
photographic paper. Methelyne blue
was adde d as dye solution to the
chemical at the rate of 10 g lit-1. The
photographic paper of size 70 × 70
mm was used to collect the droplet
samples produced at different pres-
sure combinations. The droplet im-
ages were digitalized and analyzed
using the software developed with
MATLAB. The properties of indi-
vidual ent ity in an image such as
NMD, VMD and VMD/NMD ra-
tio, were recorded and presented in
Table 1.
From Ta ble 1, it i s obse r ved
that the Volume Median Diam-
eter (VM D) and Number Median
Dia met er ( NMD) wer e r angi ng
between 106.28 to 185.56 μ and
VMD / NMD ratio was bet ween
1.09 to 1.29. If VMD and / or NMD
is within the range of 101 to 200 it
is classied as ne spray as per the
classication given by Thronhill and
Mathews (1995). Hence the particle
size distribution with eductor model
IV under the various pressure com-
binations tested was categorized as
fine spray which is recommended
for effective spray.
For uniform particle size distribu-
tion the VMD / NMD ratio should
be close to unity. The results of the
above study show that the VMD /
NMD ratio was in the vicinity of
un it y. He nce the pressure ranges
adapted for the particle size distribu-
tion was used in the tests conducted
for the optimization of the variables
Carrier tank
pressure (MPa)
Chemical tank
pressure (MPa) VMD NMD VMD/ NMD
0.0 MPa pressure difference
0.1 0.1 185.56 144 .31 1.29
0.15 0.15 169.25 138.72 1.22
0.2 0.2 165.38 142. 56 1.16
0.25 0.25 156.69 124.35 1.26
0.3 0.3 148 .62 123.86 1.2
0.35 0.35 138.92 120.8 1.15
0.05 Mpa pressure difference
0.1 0.05 183.03 141.67 1. 29
0.15 0.1 167.94 159.38 1.2
0.2 0.15 161.85 134.87 1.2
0.25 0.2 146.59 117.86 1.24
0.3 0.25 140.73 110.28 1.28
0.35 0.3 138.48 131.8 8 1.05
0.10 Mpa pressure difference
0.15 0.05 153.32 118.75 1.29
0.2 0.1 153.63 12 0. 31 1.28
0.25 0.15 14 6.35 120.48 1.22
0.3 0.2 133.63 122.92 1.1
0.35 0.25 112.5 4 106.28 1.06
Table 1 Droplet size distribution.

AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 2015 VOL.46 NO.486
affecting the chemical deposition.
Effect of Forward Speed on Quan-
tity of Chemical Delivered
The effect of for ward speed on
the quantity of chemical delivered
with respect to width of the simula-
tion plate and height of sensor at 50,
40, and 25 percent concent ration
achieved by 0.0, 0.05 and 0.1 MPa
pres sure difference bet we en t he
chemical and carrier liquid tanks is
represented in Fig. 6.
It was observed that the amount
of chemical delivered was reduced
to one third for all heights of sen-
sor for 100 mm simulat ion plate
width when the speed was increased
from 1.5 to 3.5 km h-1. For simula-
tion plate width of 150 mm, it was
reduced to about 50 percent for all
concentrations and heights of sen-
sor. For simulation plate width of
200 mm, it was reduced to about
58 percent for all concent rations
and height of sensor. For simula-
tion plate width of 250 mm, it was
reduced to about 34 percent for all
concentrations and heights of sen-
sor. The reduction in the amount of
chemical delivered with increase in
speed was due to the fact that the
duration of exposure of the simula-
tion plate to the sensor was reduced
as the speed was increased.
Effect of Simulation Plate width on
Quantity of Chemical Delivered
The effect of width of the simula-
tion plate on the quantity of chemi-
cal delivered at different heights
of sensor and for ward speed with
50, 40 and 25 p erc ent chemical
concentration achieved by a pres-
sure difference of 0.0, 0.05 and 0.1
MPa between chemical and carrier
liquid tanks is shown in Fig. 7. It is
observed that when the simulation
plate width was increased from 100
to 250 mm the chemical delivered
for all heights of sensors and at all
concentrations for a travel speed
of 1.5 km h-1 was almost doubled.
Similarly it was increased by about
2.5 times for all heights of sensor
and all concentrations when the for-
ward speed was 2.5 kmh-1. It was in-
creased by 3.7 times for all the con-
centrations and heights of sensors
when the forward speed was 3.5 km
h-1.The increase in the amount of
chemical delivered with the increase
in the width of the simulation plate
was due to the increased activation
time of the sensor. At the same time
the reduction in the increase of the
amount of chemical delivered with
the increase in forward speed was
due to reduction in exposure time to
the sensor.
Effect of Chemical Concentration
on Quantity of Chemical Delivered
The effe ct of concentration on
the chemical delivered at a forward
speed of 1.5, 2.5 and 3.5 km h-1 for
different simulation plate widths
and different heights of sensors is
presented in Fig. 8. It was observed
that when the chemical concentra-
tion was decreased from 50 to 25
pe rce nt t he a mount of chemical
delivered was almost doubled for all
combinations with different forward
speed, different widths of simula-
tion plates and different heights of
sensors. The increase in the quan-
Fig. 6 Effect of forward speed and height of sensor on quantity of chemical delivered
for different simulation plate widths at 50, 40 and 25 % chemical concentration.

VOL.46 NO.4 2015 AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 87
tity of chemical delivered was due
to the injection of higher volume of
chemical when the pressure differ-
ence was increased from 0.0, 0.05
and 0.10MPa
Fig. 7 Effect of simulation plate width and height of sensor on quantity of chemical delivered
for different forward speeds at 50, 40 and 25 % chemical concentration.
Effect of Height of Sensor on
Quantity of Chemical Delivered
The effect of height of sensor on
Fig. 8 Effect of concentration and height of sensor on quantity of chemical delivered
for different simulation plate widths at 1.5, 2.5 and 3.5 km h-1.

AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 2015 VOL.46 NO.488
the amount of chemical delivered at
different forward speed for different
widths of simulation plats at a con-
centration of 50, 40 and 25 percent
is presented in Fig. 9. The decrease
in amou nt of chem ical delivered
with increase in height of sensor
with all combinations with different
forward speeds, width of simulation
plates and chemical concentration
was due to the fact that the sensi-
tivity of the sensor decreases with
increase in the distance from the re-
ector namely the simulation plate.
Experimental Statistical Design
To statistically verify the inf lu-
ence of the different independent
variables on the amount of chemical
delivered, all the data recorded with
the experimental set up were ana-
lyzed using SAS (Statistical Analy-
sis Software).
Analysis of variance for the amount
of chemical delivered
The analysis of variance for opti-
mum amount of chemical delivered
as inf luenced by concentration of
chemical, width of simulation plate,
height of sensor above the plant can-
opy and forward speed of operation.
From the results it is conrmed that
each of the independent variables
namely chemical concentration (C),
width of the simulation plate (W),
height of sensor (H) and forward
speed (S) sig nifica ntly affect the
amount of chemical delivered. Also
the interaction effect of the vari-
ables in pairs C × W, C × H, W ×
H, C × S, W × S and H × S on the
amount of chemical delivered were
signicant. The interaction effect of
the variables in combination of trip-
licates, C × W × S, and W × H × S
on the amount of chemical delivered
were signicant. But the interaction
effect of the variables in combina-
tion of triplicates C × W × H and C
× H × S and the combination of all
four variables C × W × H × S were
not significant. The non - signifi-
cance of the above three combina-
tions may be due to the insignicant
effect of heig ht of se nsor on the
amount of chemical delivered. This
indicates that the different levels of
the fou r variables individually as
well as in combinations have a great
effect on the amount of chemical
delivered except the combination of
the height of sensor with chemical
concentration, width of simulation
plate and forward speed.
Conclusions
The significance of spray liquid
discharge rate, concentration of the
spray, width of plant canopy, height
of the sensor from the canopy and
for ward speed of oper at ions was
quantified. The range of pressures
adopt ed for chemica l and car rier
liquid produced droplets with VMD
and NMD ranging between 101 to
200 μ and VMD/NMD ratio of 1.09
to 1.29 which is classified as fine
spray. The Analysis of Variance for
optimum amount of chemical deliv-
ered as inuenced by concentration
of chem ical, width of simu lation
plate, height of sensor above the
plant canopy and forward speed of
operation indicated that the selected
va r iable s and t hei r int era ctions
Fig. 9 Effect of height of sensor and simulation plate width on quantity of chemical delivered
for different forward speeds at 50, 40 and 25 % concentration.

VOL.46 NO.4 2015 AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 89
significantly affected the amount
of chemical delivered. The mea n
co mpa r ison tests i ndicated that
the minimum amount of chemical
delivered (499 μl) was achieved at
a chemical concentration of 25 per-
cent, 100 mm width of simulation
plate, 3.5 km h-1 forward speed and
sensor height of 300 mm above the
plant canopy.
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AMA Vol. 46, No. 3
Summer, 2015
Page 34 writer's position
Writer's name Correct Position
Tarl Berry Postgraduate Student
Mulugeta A. Delele Postdoctoral Fellow
ERRATA