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Fetisov V.S.,
Bersenyov S.F., Sakayev I.I., Sizonenko R.V.
Ufa State Aviation Technical University, Ufa, Russia
MONITORING
OF INDUSTRIAL AND NATURAL OBJECTS
WITH DUTY SQUADRON OF FLYING ROBOTS
Unmanned aerial vehicles (UAV) find a wide
application for monitoring of various objects. Commonly tasks of monitoring
include data acquisition by measuring some parameters of the object or local
zone around it and (or) image
acquisition. Information interchanges between an UAV and a control station are
provided by a radio channel.
Different tasks require corresponding types of
UAVs. For example, it is better to survey extended objects such as terrestrial
pipelines or large woodlands by means of unmanned aircrafts and vice versa,
nonmobile objects of relatively small
size may be monitored by helicopters or multicopters. Such UAVs are able to
hang over a fixed point (above or near the examined object) during a long period
of time. Recently especially multicopters [1] have attracted attention due to their definite advantages
over helicopters, such as good
weight-carrying ability, flight stability, ease of control, simplicity and
reliability of construction. Being battery powered they are very quiet, extremely manoeuverable and
environmentally sound.
As a rule,
airborne equipment of a
multicopter includes radio transceiver,
controller with drivers for brushless motors, gyroscopic flight stabilization
system, GPS receiver and various sensors (optionally). If a multicopter is
equipped with a video camera, additionally camera rotating mechanism and
corresponding controller are necessary.
Commonly on-board power source is a battery of lithium-polymer
accumulators that can provide typical
time of flight about 30 minutes. After that recharging is necessary.
But in many cases it is not enough for
tracking or investigation of an object. Often continuous (sometimes
twenty-four-hour) monitoring is required. Examples of objects where continuous
monitoring is required: natural objects
with catastrophic evolution (flooded areas, volcanoes and geysers, avalanches
and torrents, forest fires and so on); industrial constructions under the
threat of collapse; city thoroughfares with problem traffic.
As well as monitoring multicopters can perform other
functions, such as delivering small packages, spraying some chemicals above the
object, performing the function of
retransmitting station for communication with
hard-to-reach objects and so on.
Arrangement of continuous duty would be possible
under presence of a terrestrial charging station and a group of UAVs. When one
is on duty at the object, other UAVs are
on the charging station. Before the flying UAV’s battery would be fully
discharged, the changing of UAVs must
be done: the duty multicopter have to land onto the charging station and
another (fully charged) goes to the object. Control of charging for each UAV
and dispatching such a group is not a
simple task. All the more so, all control must be realized in automatic mode.
The proposed monitoring system includes the
group of UAVs based on the charging station and the control station (Fig.2). The
control station ejects commands to UAVs and charging station and gathers tracking and telemetric information. The most important part of the system is the charging station which includes a few
charging terminals laying on the horizontal flat site and powered from the
common source. A few variants of realization (contact and noncontact) for
charging terminals are proposed.
The most difficult and critical operation in the
system functioning is the landing approach of the UAV and its accurate
positioning on the charging terminal. Rough approaching to the terminal is executed by the flight
program using UAV coordinates from the embedded GPS receiver. Then the accurate docking subsystem comes into
operation. This subsystem includes a transmitter inside the charging terminal
and an on-board UAV receiver. Such a short-range channel may be realized on the
basis of radio, ultrasound or infrared devices.
A
few variants of realization for charging terminals are proposed. All of them
may be classified into 3 groups:
1)
2-contact terminals;
2)
1-contact terminals;
3)
non-contact terminals.
2-contact
terminal is a device with two traditional connectors (+, -) which provides a
common DC charging chain including a power source and an on-board accumulator.
The obvious advantages of such variant are simplicity of charging circuit and
minimum of energy losses. Disadvantages are high demands of galvanic coupling
quality and necessity of very exact landing of UAV onto the terminal pad.
1-contact
terminal bases on high frequency energy transmission through only one wire. Possibility of such way is
known and discussed from the times of Tesla [2]. In this case there is no need
to position UAV precisely, because of
the landing place corresponds a
solid metal pad of a rather big size. Efficiency factor of such terminal is
lower than the same for traditional 2-contact terminal.
A wireless charging terminal bases on high
frequency (10 kHz..10 MHz) energy transfer from the terrestrial
source to the on-board accumulator charger by means of magnetically coupled
resonant circuits [3].
Flat
circuit coils (one of which is aboard, another one is under landing pad) have
to be close to each other as much as it is possible for high efficiency of
energy transfer. Exact positioning of UAV in the centre of the landing pad is not required, - it is
sufficient if the UAV is inside the terrestrial circuit coil, which must have a
size of a few times greater than the on-board coil.
Moreover,
it is possible to distribute circuit coils on the charging station in such a
way that makes all area of the
charging station be available for landing and charging (Fig.3). This solution requires additional mechanism
of detection and switching only the closest to the landed UAV terrestrial coil.
During
duty over the object information about degree of discharge of the flying UAV
battery is transmitted continuously to the control station. Besides, the
control station receives information about degrees of charge for batteries of
UAVs staying on the charging station. The control station generates commands
for the flying UAV and for the staying UAVs in accordance with the received
charge/discharge information and additional parameters and results of
measurements such as temperature, strength and direction of the wind, UAV
payload and others. Association of all these parameters helps to create and
correct the schedule of flights and charging.
Conclusions
The
proposed system extends capabilities of electric multicopters and shows the
possibility of continuous monitoring
arrangement by means of such UAVs.
References
[1] K.Nonami, et al., Autonomous Flying Robots: Unmanned Aerial
Vehicles and Micro Aerial Vehicles, Springer, 2010; DOI
10.1007/978-4-431-53856-1.
[2] http://pesn.com/2011/06/14/9501846_Tesla_One-Wire_Transmission_by_Bill_Williams
[3] André Kurs, et al., “Wireless Power Transfer via Strongly Coupled Magnetic Resonances”, Science, vol. 317, no 6,
pp. 83-86, July2007; DOI: 10.1126/science.1143254