Dan J. O'Boy

Website of Dan J. O'Boy, Structural Dynamics, Vibration and Acoustic Engineer

PhD research opportunities are listed below. Please contact me on d.j.oboy@lboro.ac.uk should you wish to discuss an interest. Alternatively, if you have a strong interest in a current industrial problem, please let me know.

1. Use of aerogels and natural materials such as cork for sound insulation
This project will investigate whether advances in reinforced aerogel materials, or natural materials can replace traditional sound proofing in automotive and aeronautical applications.
2. Active noise control of UAVs and drone rotor blade noise
This project will generate silent drones through active noise cancellation of blade generated aerodynamic noise, in order to facilitate drone deliveries to urban areas or surveillance capabilities.
3. Spatial active noise control of tyre environmental noise pollution
Noise from car tyres becomes the dominant source above a vehicle speed of around 30mph. In this project, active noise cancellation techniques will be used in a 3D environment to reduce the environmental noise pollution, using a combination of inferred microphone measurements and directional, dislocated sound sources.
4. Acoustic camera algorithms and beamforming for tracking drones / UAVs
Drones are currently being developed to track and follow other drones, using a variety of sensors including visual cameras. In order to know roughly where to point the lens and orient the drone, an acoustic camera can be used to identify where the motor noise and blade noise is coming from. Acoustic arrays of microphones can be designed to find the direction of sound, and there are examples of industrial applications using these. The student will need to create a simulation of an acoustic array, using expensive microphones and also a cheaper option, which have a less robust signal to noise ratio. Matlab will be used to obtain a real time direction for a narrow band sound source (perhaps a drone hovering).
5. Dynamic modelling of a structural battery
The movement from petrochemical engine vehicles to electric requires batteries to be incorporated into the vehicle structure (whether aircraft or car). These are heavy and bulky components. Of interest is the move towards structural batteries, either using carbon fibre as an outer reinforcement or integrating layers of materials together as a battery which also provide stiffness and reinforcement. The batteries then become part of the chassis or frame of the vehicle. Manufacturers such as Tesla produce batteries that contribute towards the torsional stiffness of the vehicle. This project is concerned with two aspects of this potential change: i) How might these models be represented in finite element work ii) How might the frequency response function change (vibration response when excited by a force) with a change in the state of charge of the battery. It would be useful to be able to generate simple design rules, or explain how to simplify the modelling of the battery structure, to show what the change of stiffness might be.
6. Embedded sensors inside the tyre carcass
The optimum selection of tyres for automotive and aeronautical vehicles is a long and time consuming process using incremental improvements and steps over previous designs. During the design of an automotive vehicle, very expensive hubs are installed onto the prototype vehicles so that wheel forces and torques can be measured. This restricts the ability of the manufacturer to test a large number of vehicles, or use information from the tyre itself as part of a real time control strategy. Tyre pressure monitoring systems are now commonplace in automotive vehicles and it is a matter of time before inexpensive sensors are included in the tread for real time measurements. Similarly for aircraft, current anti-skid controllers use brake pressures and wheel speed sensors, but no real time estimation of the runway conditions, including estimating friction and suspension forces accurately from sensors in the tyre itself. In this project, the feasibility of using inexpensive embedded sensors inside the carcass of the tyre will be assessed, in terms of the ability to determine friction and shear force measurements of the actual road, the real time road undulations and potential water depth. A transfer function will be determined between the road and wheel hub using a simple toroidal shell model such as from Soedel. The student will see if it is possible to obtain the same hub measurements but using data from the tyre carcass. It is possible that a simple FEM model of the tyre could be generated, or equations for the shell model coded in Matlab. A non contact method of measuring the real time deflection of the tyre such as using an induction coil near to the steel belts will be examined. Typically sensors are inside the tyre using piezoelectric sensors.
7. Implementation of damping in tyre off-road performance using Simulink
The design of vehicles for off-road performance on mud, snow, clay or sand is usually done through expensive experimental testing with trained test drivers. This means that prototype test vehicles need to be designed, by which time it is too late to alter the development of a vehicle or its suspension settings. Clearly, it would be preferable to be able to simulate the vehicle or alternatively, use smaller, safer scale test rigs to develop the suspension and tyre data. This project uses a Simulink model designed for replicating off road performance in near real time using an analytical model of the tyre. The stiffness and force generated is reflected in the code currently, but the damping isn't clear. What is required of the student is to understand in the existing material where the damping is currently shown and where it then needs to be added. The type of damping should be informed by civil engineering studies and the literature. I would expect the student to be able to show where the damping becomes important (how fast does the tyre need to rotate)? Mathematical models to simulate off-road tyre behaviour have been developed in the AAE department. As part of the development process it is essential to be able to compare the predictions of such models with experimental measurements. A scale test rig to measure soil parameters as a tyre rolls over sand or clay has been developed and instrumented with load cells and linear displacement sensors. This will be further developed and used to measure how the sand or clay soil deforms for different tyres, and produce data to be used to validate numerical models.
8. Machine intelligence for acoustic identification and tracking of drones / UAVs
Buildings which are secured may need to be able to detect when a drone is flying near and categorize it. Examples are prisons where it is useful to know both where the drone is, and also what type. In this project, we will explore whether it is possible to generate an artificial training database for a typical fixed and rotary wing drone to train a machine intelligence algorithm to detect and categorize the equipment. This will aid any visual equipment, such as CCTV cameras, augmenting them with an artificial intelligence algorithm. The student will be using the Matlab toolboxes to create a real time process where microphone data can be entered and design parameters output (number of motors, typical size).
9. Nastran finite element simulation of joint damping in structures
Finite element models are used to predict the vibration characteristics of aircraft and automotive vehicles. A large and complex model can be generated to determine the level of vibration which can be transmitted from one area to another. Manufacturers produce simulations of the structure and compare their results to experimental measurements. One area where there are a lot of unknowns is in the damping level to put into the simulation (the stiffness is usually easy to estimate). When comparing simulation with experimental measurements on real components, many differences are apparent. For example, there may be variability among the production components, assembly errors or environmental differences during the testing period (temperature, humidity). In this project, a finite element model of a vehicle component or body will be obtained and fitted with small areas which may be predicted to show variability. One such area might be the representation of joints, in terms of the differences in torque settings for bolts or rivets or other effects from manufacture. If there are changes from one joint to another, the vibration natural frequencies of the body might also change, due to the change of stiffness of the joint or damping in the joint. In this project a student will have to research the modelling of bolted joints, in terms of their representation for transmission of vibration at frequencies of interest to designers using finite element simulations. High fidelity models can provide very accurate results if you know how the joint is formed, but how do you reduce the complexity of the model while keeping the important physical parameters. The student will be expected to create a suite of simulations of bolted and spot welded joints in large detail and simulate a vibration experiment, and estimate where the damping is being generated. The student will be expected to use NX Nastran to carry out studies on representation of joints in vehicle assemblies. You will learn how to carry out frequency response function predictions using solutions 103, 111 108, and how these are used in industry. It may also be possible to create a number of test specimens to measure experimentally, if the student is interested in physical testing and learning skills in data acquisition and processing.
10. Off-road tyre simulation using a real time simulator and Matlab / Simulink
When manufacturers specify a tyre for an aircraft or road vehicle, it is done with regard to functionality related to the vehicle performance, for example, the load that can be carried, durability or sidewall stiffness. Using experimental testing, experienced drivers can rank different tyres subjectively for grip and feel. Aircraft pilots can also relate stopping distance and stability, with reliability and durability. The problems with experimental testing are primarily the cost associated with manufacturing many batches of custom, one off designs which might not be useful. There is then the driver, vehicle / aircraft, test conditions and location, safety and time to consider. If you are testing with a particular vehicle or aircraft in mind, by the time the tyres are tested, it is unlikely that the tyre design (constrained given the conservative nature of the industry) or final vehicle design can change significantly. It would therefore be better to be able to bring forward some of the experimental selection to a simulation stage. However, for numerical prediction tools, the vehicle manufacturers need tyre input data, either in the form of stiffness, cornering stiffness, friction data etc. The process for aircraft tyre simulation is similar. The vehicle manufacturers are not told, nor are interested in what makes up the particular tyre, only that the functionality is correct. In this project, the student will perform a literature review on tyre design and functional performance, focused on off-road tyres, and will look at the common models available. This project uses a simple Simulink, real time model of an off road tyre to predict how a tyre will roll over a rough surface. Mathematical models to simulate off-road tyre behaviour have been developed in the AAE department. The successful student will be able to run these models with changes in certain parameters to see how the response of the tyre changes, either to increase traction or minimise energy use. It would be useful for the student to generate an objective measure of how a successful tyre design can be measured (so that it may be compared against on road performance e.g. energy used in a certain task, CO2 linked measure etc). If time is permitted, we will put the simulation on the full motion simulator and see if it is possible to feel differences between the tyres (from a test driver point of view).
11. Simulation of aeroengine noise reduction materials
Skills gained: Simulation methods, data analysis, investigation of the validity of patents. The noise produced by aero engines is beginning to put limits on the operation around airports and may begin to constrain growth. With existing materials and methods, future noise reductions are extremely challenging, especially given the extreme operating conditions inside the engine and constrained dimensions. This project aims to produce future methods to reduce the operational noise and therefore increase operational effectiveness and availability of the aircraft. Simulation measurements of metamaterials will be made using numerical tools such as OpenFoam, or simplified analytical models to provide impedances of resonators. One of the most problematic is fan noise, which is low frequency and hard to attenuate. The current jet engines have liners which are designed as large numbers of small Helmholtz resonators (think of the sound of air blowing over a bottle partially filled with water). This is an effective solution at one frequency only, but does not provide a broad band sound reduction. Two options may be considered in this project, coupled Helmholtz resonators, or examining whether a distribution of sizes would provide an effective broad band reduction. Alternatively, there have been studies published that suggest a new class of man-made materials (metamaterials) can offer very large reductions in noise with only a small volume required. In this project, the student will aim to create several of these and experimentally test them for sound reduction potential. These designs will be based on existing papers published and available to the student. Previous projects have shown little success at replicating the published results, but have not been able to show whether it was due to experimental error or experimental build problems. Aerogels are another option as a class of material to consider. It is likely that a simplified plane acoustic wave solution will be generated, or a grazing flow rig using equations in Matlab. The bias flow in the engine is a particular challenge, so this needs to be considered in the equations.
12. Simulation of energy loss in flexural structural joints using finite elements
Finite element models are used to predict the vibration characteristics of aircraft and automotive vehicles. A large and complex model can be generated to determine the level of vibration which can be transmitted from one area to another. These finite element simulations can be used to predict how the structure will respond when forced harmonically, generating vibration and sound. Manufacturers need to know what vibration is transferred from one component to another to assess fatigue, levels of luxury and benchmark themselves against competitors. Manufacturers produce simulations of the structure and compare their results to experimental measurements. One area where there are a lot of unknowns is in the damping level to put into the simulation (the stiffness is usually easy to estimate). When comparing simulation with experimental measurements on real components, many differences are apparent. For example, there may be variability among the production components, assembly errors or environmental differences during the testing period (temperature, humidity). One particularly surprising area of uncertainty is how much damping should be included when joints are considered, for example rivets, bolts, welds or adhesive. Some of the damping comes from changes to the material, some from the two components moving against each other with friction. In bolts, the friction can be generated at several levels. In this project, flexural motion of joints will be considered which are typical of a vehicle component or body. One such area where differences might be explored are differences in torque settings for bolts or rivets or other effects from manufacture. If there are changes from one joint to another, the vibration natural frequencies of the body might also change, due to the change of stiffness of the joint or damping in the joint. In this project a student will have to research the modelling of bolted joints, in terms of their representation for transmission of vibration at frequencies of interest to designers using finite element simulations. If you are passing information to a finite element simulation tool, you need to be able to suggest where the friction is generated and how to represent the damping easily. The student will create a number of simulation test specimens to measure the flexural response of the joint.
13. Simulation of sound radiation from air pumping mechanism in beams with joints using finite elements
Finite element models are used to predict the vibration characteristics of aircraft and automotive vehicles. A large and complex model can be generated to determine the level of vibration which can be transmitted from one area to another. These finite element simulations can be used to predict how the structure will respond when forced harmonically, generating vibration and sound. Manufacturers need to know what vibration is transferred from one component to another to assess fatigue, levels of luxury and benchmark themselves against competitors. Energy is lost in the structure, converted to heat. One energy loss comes from an air pumping mechanism, where two plate surfaces which may be spot welded together flexurally vibrate out of phase with each other. Air is pumped out and drawn back in again, causing mini vortices and potentially, sound. Manufacturers have great uncertainty with including damping accurately in finite element simulations, so this project will aim to provide some clarity through design rules and estimations. In this project, two plates joined with bolts or welds are considered, and finite element models are created to simulate the air pumping mechanism. This is highly non-linear, so the student will need to be prepared to develop the model from linear simulations first, and potentially add Matlab simplifications to the code (analytical expressions).
14. Simulation of the noise inside an electric motor
Electric motors are becoming common as propulsion devices. They generate two types of mechanical noise, one linked to the electromagnetic field which imposes a radial excitation onto the casing and thus the frequency changes with the motor speed and also a current excitation (Pulse Width Modulation) which doesn't change with motor speed. The student will model the motor casing in finite elements, and it is of key interest to see how detailed the model can be made / what fidelity, through open access information sources. If it is possible to parameterise the model so that a designer can alter dimensions, this is useful. The aim of the project is to understand (for a typical permanent magnet synchronous motor), how sensitive some of the frequencies are to small changes in the design. For example, if a manufacturer changes the casing thickness slightly between prototype and production, does this change the response? Anecdotal evidence suggests this may be a problem.
15. Experimental vehicle directional sound source measurements in the anechoic chamber
Skills developed: Experimental measurements, knowledge of ultrasonics and vehicle safety systems. Vehicle safety systems have traditionally been passive, reacting to dangerous events such as collisions, e.g. impact bars, deformable structures. With the greater introduction of cameras, sensors and autonomous vehicle control, it is now possible for the vehicle to assess the path of travel and determine whether dangerous situations are present and if so, whether to take action. One such example may be a warning sound generated in a particular direction, appropriate to the danger being faced, to prevent the collision in the first place. Thus, a highly directional sound source is required. It will allow the vehicle to positively influence the surroundings rather than just being a passive entity. In addition, the transition from conventional combustion engine vehicles to electric and hybrid vehicles provides a significant opportunity to reduce the amplitude of noise heard by urban communities. Constant traffic noise is a source of health problems including stress, reduced quality of sleep and higher blood pressure. One problem which has become apparent from the interaction with low noise vehicles are from groups who use the noise from an engine to determine whether it is safe to cross a road, for example visually impaired persons, elderly and cyclists. To avoid danger to these groups, legislation has been introduced in America, the EU and Japan to install loudspeakers onto electric vehicles, producing noise to alert pedestrians. In order to avoid annoying all residents of an area, it is useful to consider highly directional loudspeakers so that the noise is only heard in the immediate danger area. These would also avoid the wider population being subjected to the same level of environmental noise pollution as before. Traditional methods of directional sound sources include many speakers (see cinema systems) to target one area. These are bulky and large. Think of the reversing warning sounds - they are loud regardless of whether you are in danger or not, therefore not directional. One novel possibility may be ultrasonic parametric arrays. Two high amplitude ultrasonic waves will interact to produce an audible sound, which can be used to produce an engine tone, at specific directions. Vehicle manufacturers are against any systems that create noise externally as they would create noise inside the cabin (their primary interests are for the driver, not the wider community). With a novel system such as directional speakers, it is possible to attenuate the noise inside the cabin very effectively to avoid needing significant damping materials again. This will be experimentally tested in this project through measurements in the noise and vibration laboratory and anechoic chamber. This project will investigate the possible use of these arrays against more traditional loudspeakers as generators of warning sounds. The student will be expected to utilise an existing parametric speaker system, to see what the noise is inside a vehicle. The student will also have to research the noise from electric and conventional vehicles, including the safety legislation surrounding them, the risks and side effects of introducing sound generators for low noise vehicles. The array systems do have some disadvantages, which need to be investigated. The power consumption is potentially high, although by using pulse width modulation, that may be reduced. The presence of ultrasonic waves in the environment may be attenuated using a mesh grid, which needs testing. Finally the suitability of the system for generation of real engine noises rather than just a single tone requires testing. It is likely that the student will need to liaise with the electrical workshop to produce supplementary support equipment. The student should be interested in developing experimental skills using the facilities in the department. I would also like to generate a simple Matlab model of the non-linear sound wave interaction, based on existing literature (I'm thinking perhaps of using this to identify methods to change the yaw angle of the sound source). So programming skills will be developed.
16. Validation of a finite element electric motor model
Electric motors are now common in electric vehicles and aircraft. They are complicated structures with different laminated materials, contact surfaces, bearings, windings and magnets. Loughborough has a real time motor simulation model for noise and vibration prediction, which requires validation. More precisely, the structural model needs updating in finite elements so that it agrees with the experimental measurements. We would like a student to develop this finite element model, additional complexity and specifications in Nastran / NX / Abaqus and perhaps do experimental measurements of the motor casing to produce validation data. Essentially, the more complex the design, the more uncertainty there is about the properties, especially at higher frequencies. This is a project which is linked to Ford and there may be possibilities to look at the electric motor in a Ford transit van on the hub dyno.
17. Simulation of energy loss in shear lap structural joints using finite elements
Finite element models are used to predict the vibration characteristics of aircraft and automotive vehicles. A large and complex model can be generated to determine the level of vibration which can be transmitted from one area to another. These finite element simulations can be used to predict how the structure will respond when forced harmonically, generating vibration and sound. Manufacturers need to know what vibration is transferred from one component to another to assess fatigue, levels of luxury and benchmark themselves against competitors. Manufacturers produce simulations of the structure and compare their results to experimental measurements. One area where there are a lot of unknowns is in the damping level to put into the simulation (the stiffness is usually easy to estimate). When comparing simulation with experimental measurements on real components, many differences are apparent. For example, there may be variability among the production components, assembly errors or environmental differences during the testing period (temperature, humidity). One particularly surprising area of uncertainty is how much damping should be included when joints are considered, for example rivets, bolts, welds or adhesive. Some of the damping comes from changes to the material, some from the two components moving against each other with friction. In bolts, the friction can be generated at several levels. In this project, shear motion of lap joints will be considered. One such area where differences might be explored are differences in torque settings for bolts or rivets or other effects from manufacture. If there are changes from one joint to another, the vibration natural frequencies of the body might also change, due to the change of stiffness of the joint or damping in the joint. In this project a student will have to research the modelling of bolted joints, in terms of their representation for transmission of vibration at frequencies of interest to designers using finite element simulations. If you are passing information to a finite element simulation tool, you need to be able to suggest where the friction is generated and how to represent the damping easily. The student will create a number of simulation test specimens to measure the shear response of the joint, including current test methods using hysteresis loops.