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Teleoperated Experiments On Board Remotely Piloted Vehicles
Using the World Wide Web
Charles E. Hall, Jr.
North Carolina State University
PO Box 7910
Raleigh, NC 27695
and
Siddhartha Mukherjee
Glistening Web Communications Corporation
PO Box 994
Blue Bell, PA 19422
Abstract
The World Wide Web is a tool that offers many newWorld Wide Web as a means for students to teleoperate experiments. This
paper describes work that has been performed to allow distant students
to operate experiments over the web
that are airborne in a remotely piloted vehicle.
Introduction
The use of the World Wide Web (WWW) as a teaching tool is reaching into
more classrooms everyday. Most of the WWW sites utilized by students are
essentially interactive computer programs or databases. There are a few
sites on the WWW that permit the visitor to operate a piece of equipment
and perceive the results. Many teaching and research laboratory
facilities incorporate computers that reside on the Internet. These
facilities can be incorporated into a web site that will allow
undergraduate or secondary school students access to perform
experiments.
At North Carolina State University an active program in Remotely
Piloted Vehicles (RPV) has been in operation for the past twenty years.
Initially this program was based solely on the capstone senior design
course, but this has expanded during the past seven years to include a
research based component. There has been a symbiotic relationship
between the senior design and the research programs. Equipment and and exciting
possibilities. The use of the World Wide Web for educational purposes
has btechniques developed for one program have been applied to the other.
Examples of this symbiosis are the on board computers systems for flight
control and data acquisition and telemetry systems.
This paper describes efforts to connect a web site to the computers
systems that are operating on board a RPV during flight tests via a
telemetry data link. Students are able to activate, operate and obtain
data from experiments on board the RPV in nearly real time. The flight
tests facilities, equipment and aircraft will be described. The WWW
techniques will be presented. Finally, the integration of all the
systems will be described.
Aircraft Support
The NCSU Flight Test Facility is located north of Butner, NC on
university property which is surrounded by the North Carolina Department
of Forestry land, and other unpopulated state and federal lands. This
provides for an isolated and unpopulated area for the flight testing of
RPV's. The Butner Flight Test Facility is located 28 air-miles north of
the main NCSU campus. Due to the remoteness of the facility there are no
Internet connections located on site. The flying site is located within
the NCSU Beef Cattle Research Station, which does have telephone lines
that are a mile from the runway. The runway is a 450 ft by 50 ft
een implemented. Although these appblacktop runway, oriented in the 03-21 directions. Located at the flying
site is a computer operated weather station that measures temperature,
pressure and humidity, and records this data for use in post flight
analysis.
The Converse RPV (Fig. 1) was designed at NCSU for flight testing of
small payloads. It was designed to minimize the effort and crew required
for flight test operations. The Converse RPV is capable of carrying a
payload of over 8 pounds in a space of 0.4 cubic feet. This is ample
space to contain the telemetry system, one or more of the Flight
Computer Systems (FCS), various transducers and battery packs. There are
RPV's at NCSU that are capable of carrying larger payloads, but for this
demonstration and most teleoperated experiments the payload capability
of the Converse RPV is adequate.
The computer on board the RPV is a key element for the system. The
Flight Computer System was originally developed at NCSU in 1991 to be a
general purpose on board computer system that is capable of data
acquisition and implementation of control laws[1-6]. The system is based
on the Dallas Semiconductor DS2250 microcontroller. The Dthat is used multiple times, or it can be reprogrammed at the flying
site. For example, in one afternoon 11 different student designed flight
control laws were flight tested and performance data of their systems
was recorded for each student. Included in the FCS are several support
circuits. A radio interface receives signals from the radio control
system and supplies signals to the servos which typically operate the
control surfaces. There are six channels of analog to digital converters
which typically operate with 13.5 bits of precision, but this is
modifiable via programming. Also, due to the conversion technique two
channels also generate a hybrid analog-digital integration of the
signal. The analog to digital converters are calibrated against four
precision voltages during operation to ensure accuracy of the converted
data. For communications with other computers and devices there is a RS
232 interface.
To date NCSU has flown numerous transducers on board RPV's such as
angular rate, pressure, temperature, accelerometers, velocity, position,
strain gauges and angle of attack transducers to name a few. An FCS has
been interfaced to a PSI module for measurement of multiple pressures.
In the spring 1998, the 1997-1998 Senior Design program will fly a PSI
module on a RPV with built in pressure taps in the wing and blended
wing-fuselage portions of the aircraft. With this selection of
transducers a wide variety of experiments can be designed for the
students. In addition, the on board computers can control any device S2250 is an
8-bit microprocessor, with 64K bytes of nonvolitile memory, two
programmable timers and a serial port. A major advantage of using the
DS2250 is the ability of programming it in a high level language using a
Franklin, Ltd. ANSI C compiler. This permits the generthat is carried in the RPV, to include the RPV itself.
One of the devices that the RS232 serial port of the FCS has been
connected to is a telemetry system. The telemetry systems at NCSU are
based on commercially available radiomodems. The telemetry system
primarily for the research efforts is a high speed, 128KB, full duplex,
900 MHz spread spectrum (SS) system. While the telemetry system for the
senior design program is a 19.2KB, simplex, 450MHz, narrow band FM
(NBFM) system. Both system have their inputs and outputs as standard
RS-232 and can be operated in the asynchronous mode. The SS system can
also be run in the synchronous mode. The other significant differences
between these two system are size, weight and cost. At first is may seem
that the NBFM system is severely limited by its 19.2KB simplex
structure, but since the data is transmitted in a integer binary format
that is compressed and not as ASCII numbers in engineering format the
small bandwidth can transmit a large quantity of data. This compressed
integer binary system has been employed both with the SS system and on
board data storage systems to increase their bandwidth. The NBFM system
has a key advantage over the SS system, in that operates at a lower rf
frequency and thus the NBFM system experiences less atmospheric
attenuation. Since both systems operate with a nominal 1W rf output, the
NBFM system has a longer range. The NBFM system has a range that reaches
from the main NCSU campus to the Butner Flight Test Facility a distance
of 28 miles. The SS system has a maximum range, with acceptable bitation of complex
code with ease, speed, and accuracy. The FCS can be programmed with code
lications have opened new worlds for
students, one area that has not been investigated is the use of the
error rates, of 4 miles. Thus, the SS system requires the use of a
telephone line with modems to span the distance, since there are
currently no Internet connections at the flying site. Initial
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