Global Navigation Satellite Systems (GNSS) based high-precision positioning techniques have been widely used in geodesy, attitude determination, engineering survey and agricultural applications. With the modernisation of GNSS, the number of visible satellites and new signals are increasing. Multi-constellation and multi-frequency data provide users with more observations, and hence increase redundancy in parameter estimation. However, increased number of satellites may increase the chance of multipath errors, especially in difficult environments. Therefore, this thesis aims at characterising the measurement signal quality of all available and new signals of multi-GNSS (GPS, GLONASS, Galileo, BDS, and QZSS) with real data. Also, a new multipath detection model based on machine learning methods is developed. The measurement noise levels in all currently available signals have been studied by investigating their double difference (DD) carrier phase residuals. The positioning precision, accuracy, and ambiguity success rate have been assessed using the selected individual GNSS constellations and their selected combinations with static and kinematic antennas in low multipath and severe multipath environments. The statistical results show the residuals vary from 0.5 mm to 2 mm with different signals and models of receivers. Short baseline tests show that in ideal conditions (i.e., a low multipath environment), using a single GNSS constellation (GPS, GLONASS, Galileo, or BDS) or their combinations can usually achieve millimetre-level precision and centimetre-level accuracy with almost 100% ambiguity success rates, regardless if the rover antenna is static or kinematic. In realistic condition (i.e. a severe multipath environment) the positioning precision and accuracy reduce to the centimetre level or even worse with a kinematic antenna. Multipath effect is one of the major error sources in GNSS positioning. Most of the currently available multipath detection and mitigation methods are based on stochastic modelling, advanced techniques in data processing, spatial geometry modelling, and special hardware designs. A new machine learning based multipath detection model is developed for undifferenced measurements (a single receiver approach). The approach is based on the fact that the multipath signature can be found in the multipath contaminated time series, and the features of multipath signature can be learned and identified by machine learning methods. The proposed model has been trained and validated with simulated data in an urban canyon environment with different satellite geometries. Moreover, the model has been trained and tested with real kinematic LoS and multipath data collected with a rotating arm rig in a multipath environment, and tested with multipath data collected near solar panels and near a building. The model has been tested using all available GNSS signals. The results show the model can achieve accuracy of 80%-90% with the simulated GNSS (GPS, Galileo, and BDS) data, and accuracy of 65%-70% with the real data collected using rotating arm rig on GPS L1 and GLONASS L1 signals. Real data collected near solar panels and near a building show that the well-trained model can achieve accuracy of about 60% in completely different multipath environments. The test results show the model was not well trained on GLONASS L2 and BDS data due to their carrier multipath errors are close to their carrier measurement error in ideal environment (low multipath environment).

This work proposes a method for controlling vibration transmissibility using compliant-based actuators. The compliant actuator combines a conventional actuator with elastic elements in a series configuration, such as passive springs, with the aim of controlling the vibration at important low frequencies. In contrast to the rigid actuator, a compliant actuator provides better accuracy and robustness for force control. At high frequencies, the actuator behaves like a passive spring with low impedance, providing lower output impedance and better shock resistance to the actuator than the stiff actuator. The benefits of compliant actuators for vibration control applications, demonstrated in this work, are twofold: (i) vibration reduction over a wide frequency bandwidth by passive control means; (ii) improvement of vibration control performance when active control is applied using the compliant actuator. The vibration control performance is compared with the control performance achieved using the well-known vibration absorber and conventional rigid actuator systems. The performance comparison showed that the compliant actuator provided a better flexibility in achieving vibration control over a certain frequency bandwidth. The investigation on passive and active control characteristics of the compliant actuator are conducted in relation to the compliant stiffness and damping parameters, which reveal a strong influence of the parameters to the overall passive-active vibration suppression performance. The active control characteristics are analyzed by using the Proportional and Derivative (PD) control strategy which demonstrated the capability of effectively changing the respective effective stiffness and damping of the system. These attractive dual passive-active control characteristics are therefore advantageous for achieving an effective vibration control system, particularly for controlling the vibration over a specific wide frequency bandwidth. The optimization strategy for determining the parameters of a compliant actuator to achieve effective control of vibration transmissibility is also investigated. An optimization strategy for the compliant actuator system is proposed by minimizing the H2 norm of the transfer function associated with the force transmissibility of the system, while the active control performance is investigated by using the derivative-type controller. The effectiveness of the proposed optimization strategy is demonstrated by comparison of various compliant actuator systems and the conventional rigid actuator system. It is shown that the overall passive-active control vibration performance can be improved satisfactorily. The investigation on control stability performance of the compliant actuator is also performed. The results show that the compliant actuator with varying compliant stiffness offers promising robustness and control stability for controlling vibration for the given control gain used in the system. The development of a vehicle vibration control system by integrating a compliant actuator in the existing vehicle suspension system. The compliant actuator is attached to the vehicle body and consists of a servo motor, a compliant element and a set of pinion-rack. A vehicle ride model is developed for the vibration control performance analysis, combining the vehicle suspension system with the compliant actuator model. The investigation results show that the compliant actuator can provide beneficial passive and active vibration control characteristics, particularly at low frequency region around the vehicle body resonance. The operational bandwidth of compliant actuator can be adjusted according to the selected compliant stiffness and it has the benefits of protecting the actuator against potential shocks received during vehicle ride. These benefits offer an attractive alternative for the actuator used in vehicle suspension system, compared to the conventional rigid actuator. The active vibration control results using an output feedback control demonstrate the effectiveness of the proposed system in reducing the vehicle body acceleration at important low frequencies. The last part of the thesis presents a case study of the proposed compliant actuator. Here, a new design of the compliant mechanism is proposed. Hence, the characteristics of a compliant mechanism are initially investigated using a flexible beam structure, which is deployed in various angle configurations. The co-rotational finite element method is used to model and simulate the dynamics behavior of the compliant mechanism. The results demonstrate that different configurations of the compliant mechanism will significantly influence the compliant stiffness, which in turn affects the vibration control performance. These properties assist in the selection of suitable control parameters for optimizing the vibration control performance, demonstrated through the force transmissibility analysis. The results show that the proposed compliant actuator with a flexible beam structure offers potentials for vibration control applications, such as for suppressing undesirable vibration normally encountered in various aerospace applications; as an alternative to a compliant actuator with a mechanical passive spring as the compliance.

The aviation community has to implement very stringent navigation integrity requirements in a variety of manned and unmanned aircraft applications. This thesis presents the results of the research activities carried out by the Italian Air Force Research and Flight Test Centre (CSV-RSV) in collaboration with the Nottingham Geospatial Institute (NGI) and RMIT University in the area of Avionics Based Integrity Augmentation (ABIA) for mission-essential and safety-critical Global Navigation Satellite Systems (GNSS) applications in the civil/military aviation context. Space and Ground Based Augmentation Systems (SBAS/GBAS) have been developed in recent years to improve GNSS integrity, accuracy and availability for aircraft navigation and particularly for landing applications. SBAS satellites broadcast correction messages back to the earth, where suitably enabled receivers use the information to improve accuracy and integrity. The US, Europe and other nations have developed their own SBAS systems. In the US, the Wide Area Augmentation System (WAAS) exists and is operational. In Europe, SBAS coverage is provided by the European Geostationary Navigation Overlay Service (EGNOS), in Japan by the Multi-functional Satellite Augmentation System (MSAS) and India is developing the GNSS Aided Geo Augmented Navigation (GAGAN) system. An alternative approach to GNSS augmentation is to transmit integrity and correction messages from ground-based systems. An example is the American Local Area Augmentation System (LAAS), which allows a suitably equipped receiver to derive enhanced accuracy and integrity information in a local area. The combination of WAAS and LAAS is targeted to provide the Required Navigation Performance (RNP) in all phases of aircraft navigation, including en-route, terminal, approach/landing and surface operations. Along with SBAS and GBAS, GNSS augmentation may take the form of additional information being provided by other avionics systems. In most cases, the additional avionics systems operate via separate principles than GNSS and, therefore, are not subject to the same sources of error or interference. A system such as this is referred to as an Aircraft Based Augmentation System (ABAS). The additional sensors used in ABAS may include Inertial Navigation Systems (INS), TACAN/VOR-DME, Radar, Vision Based Sensors, etc. Unlike SBAS and GBAS technology, research on ABAS is limited and mainly concentrates on additional information being blended into the position calculation to increase accuracy and/or continuity of the integrated navigation solutions. Additionally, no significant attempts have been made of developing ABAS architectures capable of generating integrity signals suitable for safety-critical GNSS applications (e.g., aircraft precision approach and landing) and no flight certified ABAS products are available at present. During flight test activities with GNSS and Differential GNSS (DGNSS) systems, it was observed that one or more of the following conditions was prone to cause navigation data outages or severe performance degradations: • Antenna obscuration due to aircraft manoeuvring; • Bad satellite geometries and low carrier-to-noise ratios (C/N0); • Doppler shifts caused by aircraft-satellites relative motion; • Interference, at the airborne GNSS antenna, caused by non-GNSS RF signals; • Multipath caused by GNSS signals reflected by the earth surface or the aircraft body. The last two problems can be mitigated by existing technology solutions (i.e., choosing a VHF/UHF Data Link, filtering the radio frequency signals reaching the GNSS antenna, identifying suitable locations for the GNSS antenna and providing adequate shielded of the antenna itself, either by physical devices or via dedicated software masks, etc.). However, there is little one can do in order to prevent critical events during realistic test/training manoeuvres and particular approach procedures (e.g., curved and segmented approaches) performed with high performance military aircraft. Furthermore, although in some cases a careful mission planning may significantly reduce the number of GNSS outages, the adoption of specific aircraft piloting strategies (using the information currently available in the cockpit) cannot effectively avoid the occurrence of these events. ABIA is a new concept that progressively evolved based on research with GNSS-based Time and Space Position Information (TSPI) systems. TSPI research activities included design, integration and ground/flight testing carried out on MB-339CD, TORNADO and TYPHOON military aircraft. As soon as the validity of the TSPI-ABIA (T-ABIA) concept was established, a prototype system was developed for use in flight test applications. This system is capable of alerting the pilot when the critical conditions for GNSS signal loss are likely to occur (within a specified maximum time-to-alert). In this T-ABIA prototype, the aircraft on-board sensors provide information on the aircraft relevant flight parameters (navigation data, engine settings, etc.) to an Integrity Flag Generator (IFG), which is also connected to the on-board GNSS receiver. The IFG can be incorporated into one of the existing airborne computers or can be a dedicated processing unit. Using the available data on GNSS and the aircraft flight parameters, integrity signals are generated which are displayed on one of the cockpit displays and sent to an Aural Warning Generator. At the same time, an alternate flight path is computed taking into account the geometry and the tracking status of the available GNSS satellites, together with the current mission requirements and the information provided by the aircraft Flight Test Instrumentation (FTI) and standard on-board sensors. Based on the results of T-ABIA research a more advanced ABIA system was developed suitable for manned and unmanned aircraft applications. Detailed mathematical algorithms were developed to cope with the main causes of GNSS signal outages and degradation in flight, namely: obscuration, multipath, interference, fading due to adverse geometry and Doppler shift. Adopting these algorithms, the ABIA system is able to provide steering information to the pilot and electronic commands to the aircraft flight control system, allowing real-time avoidance of safety-critical flight conditions and fast recovery of the required navigation performance in case of GNSS data losses. This is achieved by implementing both caution (predictive) and warning (reactive) integrity flags, as well as 4-Dimensional Trajectory (4DT) optimisation models suitable for all phases of flight. The detailed design of the ABIA IFG module was completed and validation activities were performed on TORNADO-IDS, A-320 and AEROSONDE UAV simulated platforms to determine the Time-to-Alert (TTA) performances of the ABIA system in various flight phases from departure to final approach. The results of these activities were encouraging, showing that the system TTA performance is in line with current ICAO, FAA and CAA requirements for the different flight phases, with a potential synergy with SBAS and GBAS systems to support departure, en-route and TMA operations, including CAT-I/III precision approach. Further research concentrated on the 4DT computation module and extended the scope of ABIA applications to Unmanned Aircraft Systems (UAS). In particular, an initial investigation was accomplished to identify the potential synergies of ABIA with UAS Sense-and-Avoid (SAA) architectures for mid-air collision avoidance tasks. In conclusion, although current and likely future SBAS/GBAS augmentation systems can provide significant improvement of GNSS navigation performance, it is shown that the novel ABIA system developed in this research can play a key role in GNSS integrity augmentation for mission-essential and safety-critical applications such as aircraft precision approach/auto-landing and UAS sense-and-avoid. Furthermore, using suitable data link and data processing technologies, a certified ABIA system could play a key role as part of a future GNSS Space-Ground-Aircraft Augmentation Network (SGAAN).

The engine size of modern aircraft is principally determined by take-off conditions, since initial acceleration requires the maximum engine power. An Electromagnetic Launch (EML) system could provide some or all of the energy required during the take-off phase of the flight so that the engine power requirement and fuel use could be significantly reduced. EML also has the potential of reducing the required runway length by increasing aircraft acceleration. Expensive airport extensions to face constant air traffic growth might then be avoided by allowing large aircraft to operate from short runways at small airports. The proposed system has positive impacts on total aircraft noise and exhaust emissions near airports and improves overall aircraft efficiency through reducing engine design constraints. So far, EML for aircraft has been adopted only for military applications to replace steam catapults on the deck of aircraft carriers. This thesis considers the feasibility of different technologies for EML systems to assist civil aircraft takeoff. The research develops, models, designs and compares three possible linear motor topologies which may be used to propel an A320-200 sized aircraft up to the take-off speed. The theories exploited to design the motors are thoroughly explained while the comparison of the performance is made on results from both analytical and finite element analysis (FEA). The work is validated using a small experimental setup to launch a UAV weighing 4.5 kg. The electromagnetic analysis developed for civil aircraft launchers has been employed to size the scaled down motors and the methods proposed to design all the other components of the test rig are also presented.

No description available.

Unmasking Aircraft and Rotorcraft Pilot Couplings (A/RPC) prior to vehicle entry into service has been a long standing challenge in the Aerospace Industry. A/RPCs, often only exposed through unpredictable or very specifc circumstances have arisen throughout the history of manned powered ight, and have required short-term 'fixes' to ensure system safety. One of the reasons for this occurrence is th lack of detailed practice regarding the prediction and detection of RPCs prior to full-scale testing. Often in simulation, A/RPCs are only investigated once problems have been experienced during other aircraft qualifcation activities. This is a particular issue for the rotorcraft community, where system sophistication is 'catching-up' with their fixed-wing counterparts. This research helps to extend the state-of-art knowledge surrounding the exposure of RPCs prior to any catastrophic occurrences, through the introduction of novel tools for use both in the rotorcraft design process and beyond. Using key definitions and findings from previous research efforts, objective and subjective measures have been developed for use in both real-time piloted flight and for pre- or post-flight analysis. These tools have been designed to compliment one another, in a process that should reduce the susceptibility to RPC in future rotorcraft. Novel tools developed have been tested through real-time piloted simulation, with results allowing RPC susceptibility boundaries and regions to be identified. Application of all tools developed, both subjective and objective, have been validated through comparison with existing methods. This work provides novel methods to quantify both the propensity of pilot-vehicle systems to RPCs, and the severity of these interactions. Methods have been designed with simplicity of use in mind, whereby they can be applied to vehicles of different configuration, are applicable to a wide range of RPCs, and are easily understandable for prospective users. It is believed that research contained within can contribute to the realisation of European Commission 2020 objectives, by helping to reduce the average accident rate of global aircraft operators.

The compound helicopter is a high speed design concept that is once again being explored due to the emerging requirements for rotorcraft to obtain speeds that significantly surpass the conventional helicopter. The speed of the conventional helicopter is limited by retreating blade stall, however the introduction of compounding delays the onset of this aerodynamic limitation until greater flight speeds. There are two common types of compounding known as lift and thrust compounding. Lift compounding, provided by the addition of a wing offloads the main rotor of its lifting responsibilities in high speed flight. Thrust compounding, provided by the addition of a propulsive source such as a propeller, provides additional axial force divorcing the main rotor of its propulsive duties at high speeds. The addition of compounding to the helicopter design can therefore increase the maximum speed of the aircraft. This increase in speed, provided that efficient hover capability is maintained, would make the compound helicopter suitable for various roles and missions in both military and civil markets. The compound helicopter is not a novel idea with many compound helicopter configurations flight tested in the 1960's. Due to these test programmes, as well as other studies, there is some material relating to the compound helicopter in the literature. However, the majority of the compound helicopter work describes flight tests of experimental aircraft or focuses on the design of the aircraft configuration. There are no systematic studies of the flight dynamics of compound helicopters which have been published. This Thesis targets this gap in the literature. Consequently, the aim of this Thesis is to investigate the effects of compounding on the conventional helicopter and how this addition to the helicopter design influences the flight mechanics of this aircraft class. With the renewed interest in the compound helicopter design this work is both original and timely. To investigate the flight dynamics of this aircraft class, two mathematical models of compound helicopter configurations are developed and compared with a conventional helicopter. The first compound helicopter configuration features a coaxial rotor with a pusher propeller providing additional axial thrust, and is referred to as the coaxial compound helicopter. The second configuration, known as the hybrid compound helicopter, features two wings each with a tip mounted propeller providing thrust compounding. The conventional helicopter features a standard helicopter design with a main rotor providing the propulsive and lifting forces, whereas a tail rotor, mounted at the rear of the aircraft, provides the yaw control. Other authors have focused on design considerations and have quantified all of the benefits of compounding but to date, a comprehensive study of the effect of compounding on the flight dynamics of a helicopter has not been published. The strategy of the work is to take the three aircraft configurations, the two compound helicopter configurations and the conventional helicopter, and determine their flight mechanics characteristics. Subsequently, the compound helicopter results can be compared with the baseline configuration, thereby isolating the effects of compounding. The flight mechanics characteristics that are determined in this Thesis include: trim, performance, stability and manoeuvrability attributes of the three helicopter configurations. These attributes are assessed by calculating the control angles which result in a steady flight condition and by the use of numerical linearisation and inverse simulation algorithms. All of these flight mechanics characteristics were assessed with the results, in some aspects, reinforcing the potential of the compound helicopter as well as highlighting some possible difficulties that will have to be addressed in the design of a compound helicopter.

With airports becoming busier and often struggling with insufficient capacity, the efficiency of the airports resource utilisation becomes more and more important all over the world. The efficiency may be improved by integration of the airport operations which historically were handled in separation. More effective resource utilisation would not only smooth the airport operation but also should have a positive environmental impact. The gate allocation problem is one of the important airport operations, which is often solved without considering the links with other airport operations. Modelling and analysis of new constraints which allow the ground movement information to be taken into consideration in the allocation planning in advance as well as design of appropriate solution methods are discussed. It is observed that when the additional information from the ground movement is incorporated in the allocation planning process the number of expected routing conflicts, both around gates and on taxiways, drops. This should results in a smoother airport operation during the day of operation. Data from Manchester Airport is used in this thesis to build the model, as well as to test and to validate the solution methods.

Collisions between animals and motor vehicles are frequent and often result in animal mortality. In Australia, macropods are regular victims of these collisions. This has serious implications for animal welfare and conservation as well as aesthetics and tourism. Collisions with large animals and secondary collisions caused by the presence of animals on road easements, can lead to serious personal injury and property damage. A range of mitigative measures to prevent animal-vehicle collisions exists, but no single measure can be fully effective and the efficacy of many mitigation measures remains untested. An integrated management approach, employing many mitigative techniques is required to reduce vehicle-animal collisions. Repellents have recently been identified as a potential mitigative measure for reducing vehicle-animal collisions. The aim of this study was to identify the potential role of repellents in reducing macropod-vehicle collisions in New South Wales. This required the identification and assessment of potential repellents since research investigating repellents in an Australian context is scant. Macropus rufogriseus banksianus was selected as a test species for this research as a high abundance of this species exists in southeastern Australia and it is a common victim of roadkill in New South Wales. Preliminary screening trials of four potential macropod repellents highlighted the utility of two of the substances: Plant Plus, a synthetic compound based on the chemistry of dog urine; and a formulation consisting of chicken eggs. Feeding by M. rufogriseus banksianus was significantly reduced when these substances were applied near feed trays. Modest results were also detected for Δ3-isopentenyl methyl sulfide (a constituent of fox urine), while a commercial animal repellent (SCAT® Bird and Animal Repellent) was ineffective in altering feeding by M. rufogriseus banksianus. A barrier trial conducted with the two most successful repellents indicated that Plant Plus was a more effective macropod repellent then the egg formulation. Plant Plus displayed qualities of an area repellent and elicited a stronger response from M. rufogriseus banksianus when compared to the egg formulation. Further captive trials determined that the habituation of response to Plant Plus by M. rufogriseus banksianus was minimal after six weeks of constant exposure and Plant Plus retained repellent properties after exposure to ambient environmental conditions for at least ten weeks. Field trials to establish the effectiveness of Plant Plus with free ranging macropods (M. rufogriseus banksianus and M. giganteus) were unsuccessful due to methodological limitations stemming from high background variance in observed responses, equipment failure and site disturbance from outside influences. The potential role of Plant Plus as a repellent for managing macropod-vehicle collisions was highlighted by the captive trials. However, several factors requiring further research were identified. This included assessing the repellent abilities of Plant Plus in the field and further defining the properties of Plant Plus with captive trials. The effects of Plant Plus on non-target species and an assessment of potential environmental impacts also requires attention. Research assessing the potential role of repellents in other management contexts in Australia would be beneficial and the identification and assessment of repellents for other species should proceed. However, in the context of assessing repellents for use in the management of vehicle-macropod collisions, immediate focus should concentrate on extending the research to assess the effects of Plant Plus with other species of large macropod, and assessing if Plant Plus can reduce the numbers of macropods in road easements.

All vehicles have changing payloads that affect their dynamic response. Compared to passenger vehicles, heavy machinery have larger and more greatly varying payload masses, higher centers of mass, and encounter larger disturbances. These factors lead to significant increases in the amount of vibration experienced by heavy machinery operators. This fact, when coupled with the large amount of exposure time that a typical heavy machinery operator incurs, leads to much greater vibration dosage values for the heavy machinery operator. In addition, the heavy machinery operator faces equal or greater opportunity for accident. The chance of accident, along with the increased vibration dosage, leads to an operating condition with significant safety risks, both short and long term. It has been shown that payloads affect both the stability and vibration isolation properties of a vehicle. Large payloads reduce vehicle stability while increasing the amount of vibration transmitted to the operator. A method to compensate for these loading affects would prove to be a useful technique to increase the safety of the vehicle, both in terms of accident avoidance and long term health effects of vibration. This thesis provides such payload compensation techniques. Improved vehicle dynamics were accomplished with the use of both active and semi-active suspension control. The active systems used are optimal control based, and provided the greatest improvements in vehicle performance. An optimal controller designed around a nominal payload, however, proved insufficient for operation over the entire payload range due to too large peak actuator forces at low payloads. A multiple model approach was used to remedy this problem. Semi-active systems based on a Linear Quadratic Regulator with output feedback and damping selection via static deflection were developed. The semi-active systems would require far less power than the active systems, with the need for knowledge of fewer systems states. It was shown that despite these lower demands, the semi-active systems closely approach the performance of the fully active systems.