Solutions - Group 4 - 2018/2019, Semester B, Quartile 3

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Solutions

In this section, we consider the requirements of solutions for the problem proposed in the specific problem description, all possible solutions, and both the advantages and disadvantages of each solution.

Categories

When considering the state of the art research presented in the relevant Section, we can distinguish multiple categories in which the presented solutions might fall. In this Section, we further elaborate on these different categories, and as such provide a better overview and allow for more a more specific formulation of requirements. Firstly, different anti-UAV systems serve different purposes. For our study, we differentiate between the following purposes:

Purposes

UAV Detection
These systems serve to detect the presence of UAVs in unwanted airspaces. They often also locate the UAV in question and sometimes include the possibility of continuous location tracking to assist systems categorised under the other purposes.
UAV Identification
Systems from this category serve to identify UAVs, obtaining more information about the UAV than simply its location. This information might include simple statistics, such as the average size of the drone which can often be observed by a human, given that the UAV is present in their field of view. More complicated statistics might also be obtained, such as a serial tracking number to identify commercial UAVs.
UAV Neutralisation
Drone neutralisation systems serve to neutralise a drone. This is the main topic of our study since UAV presence in the airspace above an airport introduces various risks, discussed in other Sections, that have to be neutralised in order to maintain public and societal security.

Now that the scope of the purpose of the anti UAV systems for airport security that we consider has become clear, we might further distinguish the main purpose considered in this study. As such, we differentiate between 3 different subcategories, all part of the drone neutralisation purpose. These categories are as follows:

Categories

Preventative solutions
This category encompasses all solutions that serve to prevent the problem from occurring. More specifically, entries of this category focus on keeping UAVs away from airspace belonging to airports. An example might include the geofencing system that was described previously and will be elaborated on further in the following sections.
Corrective solutions
Solutions from this category focus on solving the problem of UAV presence in the airspace over airports, specifically when said UAV is already present in that airspace. These solutions attempt to do so with minimal damage to the parties involved, an example might consist of a procedure where the control of the drone is overridden, either automatically or by a human, before the drone is removed from the airspace by landing or flight and after which control could be passed back to the pilot.
Destructive solutions
These solutions have the same area of focus as the previous category of corrective solutions, namely the minimising of further risk to air traffic above airports after a UAV has entered the airspace. The main difference is that, while corrective solutions attempt to do so in a non-destructive way, this limitation does not apply to destructive solutions. Sub-systems of a UAV or the UAV as a whole may be destroyed or permanently disabled. A coarse example consists of taking down unwanted UAVs with firearms, causing damage to the UAV and rendering it unable to continue operations.

This division into categories is not entirely black on white, however. Consider an abstract example system that temporarily incapacitates a UAV in flight, causing it to cease operation and enter a free fall towards the ground. This might result in the destruction of the drone, given the collision with the ground. We have found a grey area in our division into subcategories, and as such, we further define destructive solutions as those solutions, where the incapacitation of the drone follows from the destruction, and not the other way around. We also require the destruction to be an integral part of the solution, if we want it to count as a destructive solution. In this example, the destruction is not guaranteed nor does the incapacitation follow from the destruction. Instead, the destruction might follow from the incapacitation, dependent on other circumstances. Therefore, this specific example counts as a preventative or corrective solution, based on where the UAV in question is located. Note, however, that this is based on the keywords `temporarily incapacitates'. If the incapacitation of the UAV or one of its subsystems were permanent, the destruction would be guaranteed since it does not depend on how hard the UAV hits the ground anymore. In this case, it would count as a destructive solution.

Requirements

A solution to the specific problem described will have to adhere to requirements. These requirements are not simply capabilities the solution has to provide in the form of functional requirements, but they should also cover constraints posed on the solution. The constraints can be on the design of the solution in order to meet specified levels of quality, on the environment and technology of the system, and on the project plan and development methods. Note that there can exist multiple different types of solutions and that we, therefore, have to keep the requirements of a solution as abstract as possible. We should not limit the solution space with these requirements. Instead, we should provide a general outline of what capabilities (functional requirements) the solution should provide and under what constraints (non-functional requirements).

Furthermore, these requirements might serve as a basic framework for further development of solutions to similar problems, thereby widening the scope to other problem spaces involving UAVs as well.

The capabilities(functional requirements ) of the solution are as follows:

  • The solution should be able to take down any type of drone effectively.
  • The solution should not endanger any humans with any of its actions.

The constraints (non-functional requirements) on the solutions are as follows:

  • The solution should adhere to the new rules proposed in the `New Rules' subsection in the `Present situation' section.
  • The solution should adhere to the new rules proposed in the `Limitations' subsection in the `Present situation' section.

Possible solutions

As we have already elaborated on, a possible solution can be categorised into the purpose it fulfils with respect to anti-UAV systems at and around airports. Since a full anti-UAV system should be able to do three things: detect flying objects, identify that this object is an (unwanted) UAV, and lastly neutralisation of the UAV. However, the identification of the object might be something that is up for discussion, since it might be safer to neutralise every flying object, we will discuss this later on. As most possible (partial) solutions only cover one or two of the three things it should be able to do, before it can be considered at a full anti-UAV system, for each of the (partial) solutions listed below, they are divided up into categories of its purposes it fulfils. Such that, later on, we can compare and afterwards combine multiple of these partial solutions into one system that meets the needs of the users.

UAV Detection

  • Radar system for detecting the location and height of an object in the air. The radar makes use of a transmitter which produces an electromagnetic signal which is radiated into airspace with an antenna. If this signal hits an areal object, it will get reflected in many directions. This reflected signal is received by the radar antenna then it is processed to determine the geographical data of the object.[1]
  • A Wi-Fi receiver can be used to detect a UAV based on the signature of the signal reflected from the propellers of a UAV. Similar to a radar, a transmitter broadcasts signals and a receiver captures reflected signals that bounce of a UAV. [2]
  • Detect a UAV by listening to the communication channel between the UAV and its controller using a wireless receiver. Usually, UAVs communicate with their controllers a few times per second to update their status and to receive commands from the controller. A system could collect wireless samples and observes the signal, analyse them and can then detect a UAV's presence. [2]
  • Detection of UAVs with the use of other UAVs that fly around the airports, carrying lightweight radar systems or cameras to scan their environment.

UAV Identification

  • Identification of any specific aircraft can be done by broadcasting a coded signal, which is decoded by air traffic control towers. Such that allies and enemies can be identified and to avoid targeting a friendly aircraft. As a result, all aircraft where radar service is provided should require systems that are able to broadcast coded signals for identification, for this solution to work. [1]
  • For identification of UAVs, employing a 2D antenna and appropriate signal processing to create a multibeam, 3D, wide area overcomes the weakness of scanning radars and achieves high detection sensitivity. A decision tree based classifier can be used to identify the difference between UAVs and other moving objects. Where it rejects non-UAV targets, decreasing the number of false positives and increases true positives. Such that when neutralising such a moving object in the air, with high probability, it will be a drone instead of for example a flying bird. [3]
  • A lightweight, X-Band (10.5GHz) radar system for use on a small-scale (less than 25 kg) rotorcraft. The prototype implementation of the radar is small enough to be carried by a drone and is able to differentiate other 'miniature rotorcrafts' (drones) by their doppler signature. The prototype uses a radar system which utilises electromagnetic energy to gain information on objects by analysing the reflected energy. [4]

UAV Neutralization

  • Taking out UAVs by using air to air missiles, where these air missiles could be launched from other UAVs used by the airport or possibly any other aerial vehicle.[1]
  • Taking out UAVs or disabling specific subsystems might be achievable by using lasers. Different kinds of lasers can be used for different purposes, either permanently or temporarily disabling a UAV. [1]
  • Electromagnetic attacks to interfere with the GPS signals of the UAV, that the UAV uses to position itself. Jamming the GPS signals causes the UAV not to be able to follow the pilot's navigation commands accurately.[1]
  • Taking control of a UAV by spoofing the GPS signals of the UAV, such that the UAV thinks that it is still talking to the original pilot when it is actually being taken over. This way the drone can easily and safely be landed somewhere out of danger.[1]
  • Capturing a UAV using another UAV carrying a net, which drops the net over the unwanted UAV. Thereby taking control of the UAV as the net makes sure the UAVs rotors get tangled in the net making sure it is unusable for the pilot. Then with a parachute on the net, it can be made sure that the UAV lands safely on the ground[5]
  • A bazooka with an intelligent locking system to aid the controller to hit the UAV successfully, that shoots a net to capture a UAV. The rotors of the UAV will then get tangled in the net, making sure it cannot cause any harm anymore. Then a parachute that is attached to the net will make sure that the UAV will land safely on the ground. [6]
  • Transmitting geo-fence coordinates, avoidance commands or disruption of radio communication in order to avoid UAV's entering no-fly zone. [7]
  • Using trained eagles to neutralise UAVs. These eagles would be trained into considering UAVs as preys so that they could catch these drones and place them in a safe area. [8]
  • Geo-fencing software built into the UAVs restricts consumer UAVs to even be able to fly within a certain range of unwanted areas such as airports. [9]
  • Using high powered radio waves to disable drones, it blocks their communication with the controller and switches them off mid-air. [10]

Advantages and disadvantages

UAV Detection

Radar system

When it comes to UAV detection, radar systems provide a sufficient solution. There already exists much research on these type of systems. This partly helps with financing the solution as it is already existing technology, which should be cheaper than technology that is not fully developed yet. The disadvantage is that many airports already make use of radar systems, but that they do not seem to suffice. What one should ask themselves is whether or not these radar systems can be made in such a way that they would be reliable right now. Furthermore, how reliable would these radar systems be in the future if they are `apparently' already not reliable enough right now? All in all, radar systems offer an inexpensive way to detect UAVs, but not each type of UAV is detected.

WiFi receiver

WiFi receivers can accurately determine the position of drones. They are, however, very susceptible to interference. For example, WiFi signals can be blocked by obstacles. While it might be sufficient for right now, it is very possible for malicious attackers to attach WiFi interfering tools to their UAVs. Then, WiFi receivers might not be as reliable in the future. When it comes to solutions, reliability is one of the main concerns as the solutions has to work in all cases.

Listening on communication between drone and ground

Listening to communication between a drone and its operator can be an easy way to detect the presence of both the drone and the operator. Often, this type of communication is not encrypted. The U.S. government displayed how easy it is to hack drones made by Parrot, DBPower, and Cheerson[11]. One significant disadvantage, however, is that custom built drones might use significantly different communication standards which do make use of encryption. So this solution is only good when the communication is not encrypted, which still happens quite often as of now. The number of communications that do make use of encryption is suspected to increase with the years as the technology gets more established. Then, this solution does not provide a way of detecting drones.

Detecting drones with other drones

When we use drones to detect other drones, we do not depend on insecure channels. With this solution, we are not just limited to drones in the line of sight as the drone-detecting drone can fly around. A disadvantage, however, is that flying around with a drone at a busy airport can be quite dangerous. Furthermore, these drones can only stay in the air for a limited time due to battery or accu related constraints. This can be mitigated by simply using larger batteries, but this increases the weight of the drone, which leads to some negatives again. This might, however, still provide to be a sound solution as it makes dealing with the illegal drone activity easier as the drone itself can, for example, be weaponised.

UAV Identification

Identification by coded signal

UAV identification through coded signals can quickly identify activity. A disadvantage, however, is that other areal entities, such as bird, might also be targeted. This is due to birds being able to be roughly similarly sized as drones. Thus, this method can identify aerial activity, but there is no guarantee that only illegal drone activity is identified. Then, this could lead to negative results when we consider, for example, birds. It is possible they are targeted by the drone interception system.

3D radar system with machine learning

UAV identification through a 3D radar system that uses machine learning can eventually lead to a precise system. The issue with it is that it first needs data to learn from. The gathering of this data can provide to be difficult. Furthermore, even if it learns from this data, it does not always have to lead to correct results as there are, often, biases in data.

X-band radar system

UAV identification through an X-band radar system can perform accurate shape analysis of flying objects using doppler and high-frequency radar signals. Attaching a radar system to a drone, however, can be an issue around airports as this might result in interference with already existing systems.

UAV Neutralisation

Missiles
  • Pro:
    • Missiles will quickly take out a drone
    • Missiles are relatively cheap
  • Con:
    • The unwanted drones could be destroyed, meaning that police investigation will be more difficult
    • Having missiles at an airport could pose a safety issue
Lasers
  • Pro:
    • Lasers are very precise

Con:

    • Dangerous if it were to malfunctions
    • A huge amount of energy would be required to fire the laser
Interfering with GPS
  • Pro:
    • It won't cause harm to the drones
  • Con:
    • It may cause harm to other devices using GPS, such as aeroplanes.
    • Getting regulatory approval of jamming devices can be difficult in some jurisdictions.
GPS spoofing
  • Pro:
    • It could be used to safely retrieve the drone, making sure it lands in the desired location
  • Con:
    • GPS spoofing may also affect aeroplanes' GPS as well
    • Won't work if the flight path is pre-programmed, or if the drone is programmed to hover in one position
Capturing drones with nets underneath other drones
  • Pro:
    • Cheap and easy to implement
  • Con:
    • Requires drones to fly near aeroplanes
Bazooka net system
  • Pro:
    • Easy to implement
    • Allows for safe retrieval of drones
  • Con:
    • Limited range
Geo-fence coordinates
  • Pro:
    • Robust solution
    • Very cheap to implement
  • Con:
    • Hobbyist drones could simply ignore these constraints
Eagles

Using eagles to intercept drones is an economically friendly solution. Furthermore, the chances of a technical malfunction are non-existing. It is, however, still possible for the birds to deviate from the standard procedure when intercepting a drone even after extensive training. Moreover, flying birds near and around airports can be dangerous as they can get damaged by aeroplanes and other obstacles.

The Dutch police started using eagles to intercept drones back in 2016 already[12]. This, initially, seemed like a successful approach to seize drones mid-air. Not long after their initial usage, the Dutch political part `Partij voor de dieren' expressed their concerns regarding the safety and the wellbeing of the eagles.

After a year of training the birds, the police have concluded that the eagles were barely used. Furthermore, the NOS reports, the training of the eagles is more complex and more expensive than the police expected. Additionally, there was little to no return in training these birds. Moreover, the birds did not always follow the procedures they were instructed to follow and therefore, the police was not convinced the birds would follow these procedures in real use[12].


Anti-Drone Eagles - title text: It's cool, it's totally ethical--they're all programmed to hunt whichever bird of prey is most numerous at the moment, so they leave the endangered ones alone until near the end.


Let us consider the following comic created by Randall Munroe on May 26, 2017. This comic raises an important ethical argument against the use of eagles in anti-drone mechanisms. While eagles, the predators they are, have natural inclinations to attack central parts of drones while evading sharp bits, their lives is still put at risk.

Cueball (person in the middle) argues that using eagles as anti-drone mechanisms is unethical as it forces a rare animal to put their lives at risk. Cueball compares it to using police dogs for traffic control, which is something that most people would frown upon after giving it some thought.

The effectiveness of eagles depends a lot on the conditions of how they are used. Naturally, eagles cannot be used everywhere, but they are often effectively used where some form of ground security is present that can be used to identify and arrest those illegally flying their drones. This is partly due to these people not being able to replenish their hardware indefinitely.

Not only would the use of eagles be unethical, but also ineffective. That is partly due to the supply of eagles being rather limited. Furthermore, there are natural boundaries to how fast they can be replenished, whereas more drones can easily be created to replace those that have been destroyed. Of course, this will involve more money, but we should be prepared for the worst. As brought up in the third part of the comic, traffic control dogs would be similarly ineffective, as dogs would struggle to run equally fast as racing motorcycles. Moreover, they would, in most cases, be too powerless to stop the motorcycle even if they could keep up them.

Megan (the girl on the right) states that both ideas, the usage of eagles and dogs, sound `cool'. She does, however, understand the ethical argument that Cueball raises against their use for traffic control. On the other hand, Black hat (the man on the left) goes a step further and states that he has created a drone that hunts eagles. This flips the premise from `anti-drone eagles' to `anti-eagle drones'. In the title text, which represents a statement from Black hat, he continues that it is ethical because they - the `anti-eagle drones' - only target the most populous species first, although they will eventually eradicate the endangered ones once they bring down the number of all birds of prey. Here, Black hat seems to miss the point that it is not merely the relative number of birds that creates an ethical problem, but the fact that animals' lives are being put at direct risk by humans. This is especially negative when other mechanisms can be used that are similarly effective for a bit more money, if not equal or less. The construction of his anti-eagle drone may simply be for the point of making the eagles' goals not only dangerous but also entirely ineffective.

All things considered, the comic above raises a critical ethical argument against the use of eagles in anti-drone mechanisms.


Radio interference
  • Pro:
    • It won't damage the drones
  • Con:
    • It may cause harm to other devices, such as aeroplanes.
    • Getting regulatory approval of jamming devices can be difficult in some jurisdictions.



Back to the root page.

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 Yin, Tung. "Game of drones: defending against drone terrorism", Tex. A&M L, 2015. Retrieved on 2019-02-06.
  2. 2.0 2.1 Nguyen, P., Ravindranatha, M., Nguyen, A., Han, R., & Vu, T. "Investigating Cost-effective RF-based Detection of Drones", ACM, June 2016. Retrieved on 2019-02-06.
  3. Jahangir, M., & Baker, C. "Persistence Surveillance of Difficult to Detect microdrones with L-band 3-D Holographic RadarTM", Sensor Signal Processing for Defence (SSPD), September 2016. Retrieved on 2019-02-07.
  4. Moses, A., Rutherford, M. J., & Valavanis, K. P "Radar-Based Detection and Identification for Miniature Air Vehicles", Control Applications (CCA), September 2011. Retrieved on 2019-02-07.
  5. Liberatore, S., "How do you catch a drone? With an even BIGGER drone and a giant net: Tokyo police reveal bizarre 'UAV catcher'", DailyMail, December 2015, Retrieved on 2019-02-07.
  6. Burns, M., https://techcrunch.com/2016/03/04/the-skywall-100-bazooka-captures-drones-with-a-giant-net/?guccounter=1 "The SkyWall 100 bazooka captures drones with a giant net"], TechCrunch, 2016, Retrieved on 2019-02-07.
  7. Etak Systems LLC."Anti-drone flight protection systems and methods", Google patents, 2016. Retrieved on 2019-02-07.
  8. Thuy Ong. "Dutch police will stop using drone-hunting eagles since they weren't doing what they're told", 12 December 2017, Retrieved on 14-02-2019
  9. Gettinger, D., & Michel, A. H. " "Drone sightings and close encounters: An analysis", Center for the Study of the Drone, Bard College, 2015. Retrieved on 2019-02-14.
  10. Adam Bannister. "With anti-drone tech on the market, why was Gatwick Airport so unprepared?", December 21 2018, Retrieved on 14-02-2019
  11. The U.S. government showed just how easy it is to hack drones made by Parrot, DBPower and Cheerson. (2017). Recode. Retrieved 15 February 2019, from [1]
  12. 12.0 12.1 Haye Kesteloo, Dutch police halts use of eagles to intercept drones (2017) [2]