Systems Engineering Principles 4
- Category:Engineering and Construction
- Document type:Assignment
Title : Systems Engineering Principles for Unmanned Aerial Vehicle (UAV)
Table of Contents
2Scope of Document 2.
Radio Communication 4 3.1.1
NAVSTAR Global Positioning System (GPS) 6 3.2.1
7Concept of Operations and System Specification 4.
Software 7 4.1.1
Hardware 8 4.1.2
Hardware 9 4.2.1
Software 9 4.2.2
10Fundamental Inputs to Capability (FIC) 5.
11Collective training 5.3
12Major systems 5.4
14Command and Management 5.8
An Unmanned Aerial Vehicle (UAV), as the name suggests, is a specialized type of aircraft that does not require the pilot to be in the vehicle during operation. It is also referred to as Unmanned Aerial System (UAS) or more colloquially as ‘drone’. The vehicle is controlled remotely by human operators or autonomously by onboard super computers [ CITATION ICA11 l 1033 ]. This allows the UAV to provide a high level of autonomy as the control may be shifted between the supercomputers and the pilots depending on the requirements of the task at hand. UAVs were generally developed for use in military operations, for use in missions that were deemed too dangerous or mundane for human pilots, such as battlefield reconnaissance and long range attacks on the enemy. However, in the recent past, UAVs have increasingly been used for commercial, scientific and social tasks[ CITATION Fra15 l 1033 ].
Following the events of ‘Black Saturday’[ CITATION Zwa09 l 1033 ], it was determined that the government was grossly unprepared to tackle such an outbreak, and as such, there was need to drastically improve the capabilities available to tackle bushfires. The Australian Government is considering the use of these UAVs to aid in the management of bushfires which ravage the countryside. Due to their large surveying capability, high digital resolution techniques and flexibility in maneuvering, UAVs provide significant advantage over conventional means of detecting and fighting bushfires.
This paper details some of the capabilities that are essential so that the UAV can effectively assist the authorities in bushfire management.
Key words: UAV, bushfire, capability, communication, navigation
Scope of Document
The main aim of this document will be to introduce and define the capabilities to be installed in the UAV. It discusses the first two phases of the systems engineering lifecycle as shown in the diagram below;-
Figure 1: The V- Model for the Systems Engineering Process[ CITATION FHW05 l 1033 ]
The Concept of Operations stage details the characteristics of the proposed capabilities from the viewpoint of the pilots who will be required to pilot the UAVs. It provides the quantitative and qualitative characteristics of the proposed system to the key stakeholders.
The Requirements and Architecture stage focusses on the systems which are deemed necessary for the UAV to obtain the necessary functionality in order to meet its intended use. In this document, this stage is referred to as Fundamental Inputs to Capability,following the Defence Capability Development Manual.
The term capability refers to the synergy that arises from the combined effect of multiple inputs that are applied to achieve a desired outcome [ CITATION Cap06 l 1033 ]. Different capabilities provide the UAV with added technologies and functionalities that allow it to perform the tasks required of it with efficiency, giving it an advantage over traditional methods available for use. The capabilities to be implemented in the UAV should be readily compatible with and integrate into the existing infrastructure available to the Australian Government [ CITATION Men14 l 1033 ].
Though bushfires can cause a lot of damage, only small UAVs can be developed due to the financial constraints, as well as the fact that the vehicles can only be used for surveillance and not actual fighting of the fire.
A direct link between the UAV and the command post is very essential for efficient operation. This is emphasized by the fact that the UAV has no onboard pilot, and as such, any changes to the mission parameters needs to be done remotely by the human pilots, or by sending instruction to the guiding supercomputers. This communication consists primarily of a transmitting command and control from the pilots/ operators (this is referred to as ‘up- link’) and the returns from the UAV, such as the status of the payload (referred to as ‘down-link’).
This necessitates the need for a secure radio wave line shielded from any kind of interference that allows communication between the vehicle and the command post, through a dedicated channel linked through a satellite. A disruption of the communication system means that the versatility and wide capability of the UAV is lost, turning it into a mere drone system. The UAV will be fitted with a dongle antennae on its surface to allow for the transmission of signals to the satellite from any location.
The performance of the communication system is analyzed using the following parameters;-
Data rate – amount of data a communication channel transfers, per second (Bps)
Bandwidth – the difference between the highest and lowest frequency in a communication channel (Hz)
The link through which communication between the UAV and the command post needs to transmit data securely and at adequate rate and reliability. This may be achieved by one of the following media;-
Laser – this is an optical communication technology using propagation of light in free space to transmit data wirelessly. It is useful where physical connections are impractical due to financial or other constraints. However, it is largely being abandoned due to limited range and reduced reliability
Fiber optics – data is transmitted through a wire that propagates light. It is used in operations high data rate transmission and security with the flights at low altitudes, such as measurements of toxins contamination or in battlefield. However, it is limited in range due to the required capital and infrastructure outlay
Radio – this is currently the most used technology with UAV systems
Electromagnetic waves in the frequency range (3Hz to 300GHz) are generally considered as usable radio carriers of information. Extremely low frequency (ELF) waves to Ultra- high frequency (UHF) waves, in the range of 3Hz to 3GHz respectively, are regarded as true radio waves as they are refracted by the atmosphere, compensating for the curvature of the earth over long distances. Super- high frequency (SHF) and extremely high frequency (EHF) waves are not refracted, thus their transmission capability is limited to the line of sight.
Data transmission between the UAV and the command post requires high data rate, tending towards the higher frequency waves. Therefore, there is need to develop infrastructure to help maintain the direct line of sight between stations. As a result, a compromise is needed between the frequency of transmission and the data rate required for the system. UHF frequencies are the most desirable, but there’s conflict with domestic uses, requiring data transmission to be done at higher frequencies, such as SHF.
Table 1: Radio Frequency Spectra
For successful transmission and reception of UAV data, the configuration of the antennae needs to be similar. The antennae is mounted on a rotatable turret to maintain connection with the UAV, unless an omnidirectional antenna is used. The most common antennae used with UAV systems are shown below;-
Figure 2: Types of Antennae[ CITATION Aus10 l 1033 ]
There is a variety of navigation systems available for UAVs to fly a route to the assigned location. A basic navigation system integrates the use of a low cost inertial measurement unit, a GPS receiver, and a triad of magnetometers to generate a solution that in turn is used to develop the navigational algorithms [ CITATION Elk12 l 1033 ]. The UAV should be sufficiently navigable to reach the desired destination avoiding obstacles along the way. The positioning system should also be accurate enough so that the information sent back to the command post is reliable enough to allow accurate decision making.
NAVSTAR Global Positioning System (GPS)
This system was developed for the US Military but was declassified for general use. A receiver calculates its position using the signals sent from four or more GPS satellites selected from a cluster of 24 nominal satellites, selected based on quality of signal and geometry. The signals transmitted contain the departure time from each satellite. The UAV’s receiver uses the arrival time to calculate the distance from each satellite, thereby determining its global positioning. The GPS makes use of radio frequencies between 1.1 and 1.6 GHz.
There are two available services of GPS, namely;-
Standard Positioning System (SPS) – used by civilian users, utilizing signals at L1 frequency with an unencrypted course acquisition code. It is accurate to
Precise Positioning Service (PPS) – utilizes both L1 and L2 frequencies, modulated using encryption codes to establish a position fix. They are accurate to and are used for military applications
Differential GPS may be used to improve the accuracy of GPS systems. It involves a network of fixed reference station on the ground that broadcast the difference between the fixed and virtual satellite positions. These differences are then used to correct the data received from the UAV system.
A major shortfall of GPS signals is their vulnerability to interference. The signals at the receiver are usually weak, and as such, can be jammed using natural emissions or even radio emissions. This may be catastrophic given that the UAV is exposed to infrared radiation when surveying the bushfires.
Concept of Operations and System Specification
All UAVs, regardless of size and application, utilize sensor systems which provide an estimate of the vehicle’s full state vector. The state vector consists of position coordinates, velocity vectors and the vehicle’s attitude. The UAVs also make use of guidance systems which determine the path to be followed to the destination and control systems which adjust the vehicle’s control surfaces to follow the determined path.
Figure 3: Unmanned Aerial Vehicle Operation Concept
The components to allow for proper communication between the UAV and the command post are as follows;
An Orthogonal Frequency Division Multiplexing (OFDM) based modem architecture is proposed for operation of the UAVs to achieve flexible data rates (about 62kbps to 744kbps) depending on the link quality. This provides the drone with a high range of maneuverability as a direct link can be maintained over a high fluctuation of frequency, where the signal processing is done using Field Programmable Gate Arrays (FPGAs) [ CITATION Mah07 l 1033 ]. This technology allows for seamless connection between drones and command posts from 100m up to 10 km away from each other.
The OFDM based architecture also provides for the use of adaptive modulation and coding, allowing for robustness in environments with selective fading frequency. This is advantageous to bushfire management as large sectors of the vulnerable area have limited to none network coverage.
Low cost hardware components readily available in the market can be used to develop the system. These components should provide for up and down conversion of information, over a flexible data rate network. The hardware should also have low power consumption to allow the drone to cover more extensive areas, and offer reliable service for control applications operating on rates considered low or moderate.
Figure 4: FPGA Transmitter and Receiver
A decoder and encoder will also be required to properly code the message to prevent any distortion due to interference during transmission.
The components for an efficient navigation system are as mentioned below;
There are different aircraft models used as UAVs, such as the Ultrastick 120 fixed- wing aircraft model, also known as the Free- flying for Subscale Experimental Research (FASER). It is equipped with flight control surfaces available on conventional aircraft, as well as wingtip vanes on either sides of the aircraft[ CITATION Elk12 l 1033 ] . The FASER underwent extensive wind tunnel testing to come up with the most efficient aerodynamic model.
Figure 5: The FASER aircraft model
The autopilot used to navigate the aircraft is referred to as Santa Cruz Low- cost UAV GNC System – SLUGS [ CITATION And09 l 1033 ]. It has undergone various changes over the recent past in a bid to implement more reconfigurable autopilot for UAV guidance, navigation and control. High fidelity and high bandwidth must be available to the controller to allow for proper guidance and control of the UAV, as well as automatic control to allow for precision applications which require accurate positioning, such as landing.
Figure 6: The UCSC SLUGS Autopilot
Relatively low cost powerful computers have been implemented in the UAV, to allow for sensor fusion to facilitate navigation. This involves the blending of information from various sources, which may have inherent flaws, to obtain a more representative image. Advances in the technology aim to increase the accuracy of individual sensors so as to reduce the number of sensors required to give accurate information.
Fundamental Inputs to Capability (FIC)
The proposed UAV system to be deployed in bushfire management will be a complex unit comprising of an array of sophisticated systems providing different functionalities. The functionalities assessed in this document to determine their effectiveness of the UAV system in meeting its intended use are;
The following FICs are analyzed to determine the impact the implementation of each of the above capabilities will have on them.
The personnel required for the operation of the UAV are the pilots who control it remotely. The UAV are a new technology that the Australian Government intends to implement to aid in bushfire management. As a result, there is need for additional personnel requirements, preferably from the Air Force, who have experience controlling such drone systems.
The communication system is intended to be interoperable with the existing system, so that the decision- making channel is not interrupted. Consequently, no additional personnel will be required for the operation and maintenance of the communication system of the UAV.
The navigation system will consist of a network of ground and aerial satellites. Additional personnel will be required for the installation, deployment, operation and maintenance of these satellites. Further personnel will be required for the maintenance of the UAV aircraft itself.
The management staff for the capability will be sourced from the Bushfire Management Committee, the Rural Fire Service (RFS), Fire and Rescue NSW and the State Emergency Service (SES). These departments will provide a majority of the personnel requirements required for capability implementation. Additional staff may be required during the Acquisition, In- service and Disposal stages.
The impact to personnel can largely be attributed to Training (section 5.1.3 below). All other levels of support will be provided by the Support Contactor or the Military.
A special unit to operate the UAV system will be setup within the Bushfire Management team, using existing resources for purchase and support of the UAV. The unit will also include some members of the Australian Military.
The UAV will be operated by this special unit utilizing the resources of the Bushfire Management team. The UAV’s communication system should integrate seamlessly with the existing communication systems.
The organizational impact on the contractors dealing with Acquisition and Support to provide their contributions towards the UAV capability, such as delivery and Through Life Support (TLS), will be handled internally.
The introduction of the UAV system will necessitate the training of the associated groups in the Bushfire Management team. This training will focus on the deployment, operations and maintenance of the system. Personnel required to take training will include those interpreting the data received from the UAV and the managers in charge of decision- making. There is need for training of the pilots on the operations of the communication systems.
Deployment training will be provided to the pilots in a bid to familiarize them with bushfire scenarios and management procedures. Given the military background of these personnel, it is expected that this training will be conducted for a short period.
Navigational training will be provided to allow the pilots to completely understand their aircrafts, understanding its strengths and weaknesses. This will involve a series of obstacle courses to determine the effectiveness of the navigation system, as well as the pilot’s proficiency.
If the UAV communication system is different from the existing, there will be need for additional training. This is, however, unexpected as integration of the two is paramount. The pilots should be able to discern the information being provided to them by the system, so as to make quick and well informed decisions.
The training packages will be developed by the Acquisitions contractor and approved by the Bushfire Management team. The type, duration and frequency of the trainings will be determined by the Acquisitions contractor to maintain seamless operation of the system. The Bushfire Management Team can request additional trainings should the need arise.
The personnel to be trained include;
UAV operators – operator training
UAV maintainers – maintainer training
The UAV is fitted with a wide array of electronic systems which process the influx of information received through the numerous on- board sensors. These systems should be able to assess the data, filter it and present the relevant data to the pilots for them to make the appropriate changes, without undue interference.
The navigation system will require a wide array of ground and orbit satellites in order to accurately determine the position of the UAV above the earth. This allows the Bushfire Management team to comprehend the extent of the fire and come up with solutions that can be used to mitigate its spread.
The versatility provided for by the UAV system means that no additional major systems are required for its continued operation. The aircraft can be launched from any location, and the remote navigation determines its flight path.
The operational needs and supportability of the UAV system will be considered when determining the required supplies. The Bushfire Management team is responsible for distribution of supplies, and will manage the Acquisition and Support contractors to ensure there is enough stock available during operation
The communication system is vulnerable to various factors, such as heat, smoke, dust and bombardment, which are plenty in case of a bushfire outbreak. The range, quantity and storage distribution of all necessary supplies will take into consideration the area of coverage and the expected area vulnerable to bushfire outbreak, using optimization methodology and tools.
The deployment and navigation of the UAV system will be assessed using similar methodologies, assessing the impact of introduction of new parts requiring coding on the performance of the system.
The distribution of these supplies will follow existing procedures of bushfire management. Components of the new technologies requiring specialized handling will require development of new distribution channels, in conditions not affecting their efficiency.
There is need for proper storage facilities where the UAV aircrafts will be placed when not in operation. These facilities could also be where necessary repairs to the system can be carried out, to ensure the efficiency of the capability is maintained.
The communication system implemented in the UAV system is expected to be similar or complementary to the existing one, negating the need for additional facilities.
The navigational system depends on the continuous relay of information using various infrastructure, physical, such as telephone masts or wireless, like satellites. The limitation in the distances between transmitting and receiving towers is governed by line of sight, determining the positions where these facilities need to be installed.
Any impact on the Acquisition and/ or Support contactors with regard to their proprietary utilities or facilities will be catered for by the associated contractor.
The operation of the UAV system will involve the broader support infrastructure and services of the Australian Military, the Bushfire Management Committee and specialized civilian population in general to achieve its intended purpose.
The deployment system will require relatively minimal support as the system is largely self- sufficient and integrates seamlessly into the existing system. No additional skills will be necessary to facilitate the operation of these systems.
The communication system requires gadgets and equipment that facilitate its operation. These technologies do not function best when placed inside the vehicle, due to obstruction and interference from other systems in the vehicle. Therefore, these systems are installed on the outside of the vehicle, with robust housing to withstand the harsh conditions associated with bushfires.
The navigational system requires significantly robust support infrastructure in the form of satellites, transmission and receiving towers. A safety/ salvage system, such as parachutes or airbags, should also be provided should the UAV fail mid- flight to prevent it from complete damage when it falls to the ground. These systems should be automatically deployable if there is an uncontrollable descent.
The Acquisition and Support contractors will provide external assistance to the UAV, when required, to the maturity of the proposed capability. This support includes the provision and implementation of infrastructure and services and other external relationships supporting UAV functionality.
Command and Management
The UAV system will be required to comply with the regulatory framework in place and subsequent approvals by the Bushfire Management Committee.
The communication systems are proprietary property, and as such, legal procedures must be followed regarding its purchase, installation and use in military operations. The pilots will have to be held accountable for any damages that are caused to the system which are not as a direct result of the activities of bushfire management.
The technical regulatory command and management structures already in place in the Bushfire Management Committee will be followed during the operation and maintenance stages of the UAV system.
There is no need for the establishment of additional command and control posts for the proposed capability to be achieved and maintained.
The UAV is a very important component to help in the management of bushfires, and the proposed capabilities provide crucial functionalities that enable it to perform its task effectively. Efficient communication between the UAV and the Command Post allows for data collected to be relayed back and help in the deployment of emergency services to quell the danger. The communication link also allows the pilots to remotely control the vehicle and gather as much relevant data as possible.
Proper navigation is also crucial to ensure that the drone is able to portray the situation in the most sensitive areas, to allow for prioritized deployment of the emergency services. It is also important to keep the vehicle safe from the dangers posed by bushfires, so as not to lose an invaluable piece of equipment.
Therefore, the use of the UAV could help the Australian Government gain more control in bushfire management.
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