MONITORING OF INDUSTRIAL AND NATURAL OBJECTS WITH  DUTY SQUADRON OF FLYING ROBOTS

Технические науки / 9. Авиация и космонавтика

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