Paper No.
98-3108
An ASAE Meeting Presentation
A LAPTOP COMPUTER BASED DATA ACQUISITION SYSTEM
TO MONITOR TRACTOR PERFORMACE
By
A.A. AL-JANOBI
Associate Professor
M.F. W A H B Y
Professor
M.A. A L - B E L A K H Y
Graduate Student
Department of Agricultural Engineering
College of Agriculture, King Saud University
Riyadh, Saudi Arabia
Written for Presentation at the
1998 ASAE Annual International Meeting
Sponsored by ASAE
Disney's Coronado Springs Resort
Orlando, Florida
July 12-16,1998
Summary:
A data acquisition system was developed to measure a set of performance parameters of an
instrumented tractor. The measured parameters included the front and rear wheel pin forces, the
drawbar forces and the front, rear and fifth wheel speeds. The system included a laptop computer,
two data acquisition cards and a speed signal conditioning circuit. The laptop displayed the
measured parameters and analyzed data on the console in a well-designed format. It also signaled
on faulty transducers and gave an indication of stability of the tractor. The system was field tested
on an asphalt surface for its performance. The system provided accurate and reliable results.
Keywords: Tractors, Performance, Transducers, Data acquisition, Instrumentation.
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A LAPTOP COMPUTER BASED DATA ACQUISITION SYSTEM
TO MONITOR TRACTOR PERFORMANCE
A.A. AL-JANOBI
Associate Professor
M.F. WAHBY
Professor
M.A. AL-BELAKHY
Graduate Student
ABSTRACT
A data acquisition system was developed to measure a set of performance
parameters of an instrumented tractor. The measured parameters included the front and
rear wheel pin forces, the drawbar forces and the front, rear and fifth wheel speeds. The
system included a laptop computer, two data acquisition cards and a speed signal
conditioning circuit. The laptop displayed the measured parameters and analyzed data
on the console in a well-designed format. It also signaled on faulty transducers and gave
an indication of stability of the tractor. The system was field tested on an asphalt surface
for its performance. The system provided accurate and reliable results.
Keywords: Tractors, Performance, Transducers, Data acquisition, Instrumentation.
INTRODUCTION
Recent developments in computer
based data acquisition systems greatly
increased the ability to scan and record various performance parameters of tractors and
implements.
These systems differ in complexity from measuring one or two parameters
to on board computer based data acquisition systems measuring several parameters
simultaneously.
Their design and fabrication varied according to individual data
collection requirements.
Article is written for presentation at the 1998 ASAE Annual International Meeting as ASAE
Paper No. 98-3108.
The authors are: Abdulrahman A. Al-Janobi, Associate Professor, Muhammed F. Wahby,
Professor, and Manzoor A. Al-Belakhy, Graduate student, Department of Agricultural Engineering,
College of Agriculture, King Saud University, Riyadh, Saudi Arabia.
Acknowledgement: The authors would like to acknowledge the research support from the King
Abdulaziz City for Science and Technology, Riyadh, Saudi Arabia (Project AT-16-GS7).
1
Al-Suhaibani et al. (1994) made an extensive review of instrumentation systems
used to measure and record tractor and implement performance parameters. A number
of instrumentation systems to
determine the field
performance of tractors and
implements operating under different field conditions have been developed and reported
by researchers. Majority of them was designed exclusively for a particular tractor and
not easily adaptable to other tractors. Hence they are generally expensive and complex.
Some researchers made attempts to develop instrumentation systems generally portable,
interchangeable and easily acceptable to the most common tractors used in different
farm sites. Al-Suhaibani and Al-Janobi (1996) developed a portable instrumentation
system to measure drawbar pull, PTO torque and speed, tractor speed and slip, fuel
flow, engine speed and temperatures of fuel and engine of a wide range of agricultural
tractors. Lackas et al.
(1991) developed a portable data acquisition system to measure
the draft requirements and operating speeds of soil engaging implements. Thomson and
Shinners (1989) developed a portable instrumentation system to measure draft and
speed when using either pull type or three-point hitch mounted implements.
Presently most of the researchers have been involved in the development of
computer based data acquisition systems for monitoring performance parameters of
tractors and implements. These systems employ a microcomputer to scan a number of
transducers,
convert analog signals into digital format, count pulse signals and store the
data in the memory. These systems are simple, compact and inexpensive and hence to
provide the operators the facility for field verification of collected data. Also they help
to check on correct system function and provide immediate availability of data for use
in demonstrations. Researchers have developed a number of general purpose tractor
instrumentation and IBM compatible computer based data acquisition systems for use in
a wide range
of field experiments on tractor and implement to measure various
performance parameters (McLaughlin et al., 1993; Grevis-james et al., 1983; Tompkins
and Wilhelm, 1982; Freeland et al., 1989).
The objective of this project was to develop a data acquisition system to measure
a set of performance parameters of an instrumented tractor. The specific objectives were
to
2
1. Develop a laptop computer based data acquisition for data collection, analysis,
display and storage
2. Develop a speed signal conditioning circuit for front, rear and fifth wheel speeds
measurement
3. Develop a menu-driven software for the laptop to perform the following tasks:
a) Measure, analyze, display and store the required performance parameters during
field operation
b) Signal the malfunctioning/open transducers during field operation based on an
Expert System knowledge base
c) Give indication of stability condition of the tractor during field operation and
simulate to obtain the best performance of the tractor.
DATA ACQUISITION SYSTEM
The data acquisition system consisted of an IBM compatible laptop computer,
two National Instruments' data acquisition cards (DAQ-700 and DAQ-1200), a speed
signal
conditioning circuit, front and rear wheel torque and weight transducers, a
drawbar dynamometer
and a fifth wheel ground speed sensor. The speed signal-
conditioning unit and the laptop computer were small enough to be placed on a locally
made platform in the tractor cab. The complete data acquisition system is illustrated in
figure 1.
The system was designed and developed to be used on a MF 3090 tractor. The
right front and rear wheels of the tractor were equipped with two wheel torque and
weight transducers to measure the torque and forces acting on the tractor wheels. The
design and development of the transducer are reported by Al-Janobi et al. (1997). The
tractor was also equipped with a drawbar dynamometer to measure the force exerted by
implements connected to the tractor. Two optical shaft encoders coupled to the right
front and rear wheels of the tractor through a flexible drive and a slip-ring were used to
measure the travel speed, whereas a fifth wheel together with another optical shaft
encoder connected underneath the tractor was used to measure the tractor ground speed.
These speed transducers were calibrated by running the tractor on a flat asphalt surface
for a distance of 50 m in three selected tractor gears at the rated engine speed. The other
transducers used in
the instrumentation system were calibrated using a specially
3
designed and built calibration rig. The complete description of the instrumentation
system and the calibration procedure are given by Al-Suhaibani et al. (1994)
The laptop computer communicated with the data acquisition card DAQ-700 via
the PCMCI slot, whereas the DAQ-1200 through the parallel port, sampled, analyzed
and stored the data from the transducers. Both the DAQ-700 and DAQ-1200 had the
capability of reading analog signals, counting pulses from speed sensors and outputting
TTL-level digital signals for control purposes. In this project the DAQ-700 was used for
reading analog signals and providing TTL signals for control purposes, whereas the
DAQ-1200 was used exclusively for counting pulses from the speed sensors. The laptop
was equipped with 16 MB of RAM, 810 MB of hard disk and a 3.5" floppy drive of
1.44 MB capacity. Data were stored quickly in data files in the hard disk and this
avoided the
potential
problem
of disk failure due to the rough and dusty field
conditions.
Speed Signal Conditioning Circuit
The optical shaft encoders coupled to the right front and rear wheels were used
to measure the tractor travel speed as well as to determine the angular position of the
clevis bolts in the wheel torque and weight transducers with respect to the vertical
reference passing through the wheel center. The determination of the angular position of
the clevis bolts was necessary to obtain the horizontal and vertical components of forces
acting on the tractor wheel during field operation. The design of an angular position
measurement circuit proposed by Al-Janobi and Al-Suhaibani (1996) was adopted in
this project for measuring the angular positions of the clevis bolts in the wheel torque
and weight transducer as well as conditioning the speed signals suitable for both the
DAQ-700 and DAQ-1200 data acquisition cards.
The electronic circuit which contains
integrated circuit (IC) chips - two 7473
dual JK Flip-Flop, one 7408 Quad 2-input AND Gate, one 4040 14-stage Ripple-Carry
Binary Counter, and 7805 and 7812 voltage regulators providing 5 and 12V respectively
were made to be used in the data acquisition system. The circuit is illustrated in figure 2.
The regulated power supply circuits built around 7805 and 7812 with 15V input
from the tractor electrical system were used to provide power to all the ICs with 5V and
4
the DAQ-1200 with 12V respectively. Vertical position of clevis bolt No. 1 of each
wheel torque and weight transducer was taken as the reference for the angular position
measurement of the clevis bolts. This was marked by the output signal from a magnetic
pickup installed behind the wheel torque and weight transducer. The two magnetic
pickup outputs one each for the front and rear wheel torque and weight transducers were
fed to the clock inputs of 7473, whereas, the J and K inputs of the two 7473 were tied to
the 5 and OV grids respectively. The output of the optical shaft encoder was connected
to one of the inputs of 7408 AND Gate. The other input of the AND Gate was the
output signal from 7473. By the high to low clock transition of 7473 in accordance with
the magnetic pickup output, the AND Gate output set to give signal corresponding to
the optical shaft encoder output. These pulse signals available at the Quad 2-input AND
Gate were fed to the two pulse counters of the DAQ-1200. Due to the lack of sufficient
number of pulse counters in the DAQ cards, the binary counter 4040 together with one
of the I/O ports of DAQ-1200 were used to measure the output signal of the optical
shaft encoder coupled to the fifth wheel. The necessary control signals such as the
RESET signals for 7473 and 4040 and the GATE signals for the counters of DAQ-1200
were provided by the DAQ-700.
Software
The laptop computer provided the ability to collect, analyze, display and store
the data during the test run. A flexible, modular, user-friendly application program was
needed for the data acquisition system, which was to be used for both research and
educational programs. Thus, a data acquisition software was developed in Borland C++
for this application. This program was menu-driven, windowed input forms and option
selection choice lists to enhance user friendliness. It also incorporated routines to verify
input signals read by the data acquisition system. This helped in identifying whether any
transducers were malfunctioning or disconnected from the instrumentation system.
A flow chart of the data collection and analysis routine is illustrated in figure 3.
During laptop initiation, the data acquisition cards sampled the data from the various
transducers connected in the instrumentation system. The data were converted into the
engineering units using the calibration constants and coefficients. Then these values
were tested for the proper functioning of the transducers and the variability of the
readings. Suitable minimum and maximum numerical values were set in the program to
5
check for the proper operation of the transducers. If a data corresponding to a transducer
would not fall in between the minimum and the maximum values, the display would
show an indication of a faulty/open transducer. For the variability testing, a set of
readings was taken continuously and checked for any marginal difference between
them. If there was no adequate changes in the readings, the tractor was considered to be
operating normally and smoothly.
Then the program entered the routine for determining the stability condition of
the tractor. For the normal stability condition of the tractor, the value of coefficient of
stability, C O S . should be > 1.25. When it comes below to the value 1.0, the tractor
may fall upside down from the front end. This was indicated by an alarm in the laptop.
Then the control was transferred to the speed check routine to see the tractor still
moving. Once the check was successful, the program entered the routines for tractive
efficiency calculation and the simulation to obtain the optimum operating condition of
the tractor.
The program had been continuously monitoring and displaying the sampled as
well as the processed data on the monitor of the laptop in a well-designed format as
illustrated in figure 4. This helped the user to verify the validity of the data collected.
The display of data on the screen could be toggled on or off from the main menu.
Finally, the program provided an option for data collection in a format to obtain the disk
drive, directory path and file name for storing ASCII data
System Performance
The system was field tested for its performance. The system performance was
noted to be excellent in real time display of sampled and processed data. A faulty/open
transducer and stability of tractor could be detected from the graphical display, although
experience in recognizing the corresponding signal was necessary.
REFERENCES
Al-Janobi, A. and S.A. Al-Suhaibani. (1996). A data acquisition system to monitor
tractor performance. ASAE Paper No. 96-1095 St. Joseph, M I : ASAE.
6
Al-Janobi, A., S.A. Al-Suhaibani, A.A. Bedri and A S . Babeir. (1997). A precision
wheel torque
and weight transducer for most common agricultural tractors.
Agricultural Mechanization in Asia, Africa and Latin America 28(1): 13-17, 22.
Al-Suhaibani,
S.A. and A. Al-Janobi. (1996). An instrumentation system for measuring
field performance
of
agricultural
tractors.
Misr
Journal
of Agricultural
Babeir and J. Kilgour.
(1994). Mobile
Engineering 13(3): 516-528.
Al-Suhaibani,
S.A., A.A. Bedri, AS
instrumentation
package
for monitoring tractor performance.
Agricultural
Engineering Research Bulletin No. 40, King Saud University, Riyadh, Saudi
Arabia.
Freeland, R.S., F.D. Tompkins and L.R. Wilhelm. (1989). Portable instrumentation to
study performance of lawn and garden ride-on tractors. Applied Engineering in
Agriculture 5(2): 143-147
Grevis-james, I.W., D R . DeVoe, P.D. Bloome, D.G. Batchelder andB.W. Lambert.
(1983). Microcomputer-based data acquisition for tractors. Transactions of the
ASAE 26(3): 692-695.
Lackas, G.M., R D . Grisso,
acquisition
system
for
M. Yasin and L.L. Bashford. (1991). Portable data
measuring energy requirements of soil-engaging
implements. Computers and Electronics in Agriculture 5: 285-296.
McLaughlin, N.B., L.C. Heslop, D.J. Buckley, G.R. St. Amour, B.A. Compton, A.M.
Jones and P. Van Bodegom. (1993). A general purpose tractor instrumentation
and data logging system. Transactions of the ASAE 36(2): 265-273.
Thomson, N.P.
and K.J. Shinners. (1989). A portable instrumentation system for
measuring draft and speed. Applied Engineering in Agriculture 5(2): 133-137.
Tompkins, F.D.
and L.R. Wilhelm.
(1982). Microcomputer-based,
acquisition system. Transactions of the ASAE 25(6): 1540-1543.
7
tractor data
Front wheel torque transducer
]
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Pin2
Pin3
Rear Wheel torque transducer
,
Drawbar dynamometer
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(1)
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1 Junction box (A B, C, D, and E)
3. Slip ring-shaft er.code: unit
:
2. Strain gauge amolifier
4. Magnetic pickup
Figure 1. Diagram of tractor instrumentation and data acquisition system.
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Figure 2. Speed signal conditioning circuit and the various connections to the laptop.
Read data
Conversion of sampled
data into engineering units
Error
No error
Calculate coefficient of
stability
No
Calculate tractive efficiency
Figure 3. Flow chart of data collection and analysis
10