D G Tilley's research while affiliated with University of Bath and other places
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Publications (40)
The performance of hydraulically actuated machine systems could be improved with the use of valves that have high bandwidth and high flowrates under low pressure drops. Although high flowrates can be achieved using very large spool strokes and/or diameters, the overall bandwidth of the valve will be reduced. Research has therefore been undertaken o...
To expand the operational capabilities of hydraulically actuated systems the development of new valves capable of enhanced flow rates and bandwidth performance is required. In previous work, the solution to achieving desired flow rates was to increase valve spool size and travel, but this is at the expense of the dynamic response. To increase flow...
Non-linear seal friction can impede the performance of hydraulic actuation systems designed for high precision positioning with favourable dynamic response. Methods for predicting seal friction are required to help develop sealing systems for this type of application. Recent simulation techniques have claimed progress, although have yet to be valid...
A multi-technique approach to modelling artificially ventilated patients on the adult general intensive care unit (ICU) is proposed. Compartmental modelling techniques were used to describe the mechanical ventilator and the flexible hoses that connect it to the patient. 3D CFD techniques were used to model flow in the major airways and a Windkessel...
The research was carried out to discuss the possibility of using piezoelectric (PZT) actuator for screw in cartridge valves. Main smart materials were introduced briefly and the PZT stack was selected as the best actuator for cartridge valves. The concept of a spool valve piloted by a PZT valve was brought forward. The mathematical model of a hydra...
This paper describes two approaches to modelling lung disease: one based on a multi-compartment statistical model with a log normal distribution of ventilation perfusion ratio ( V ˙ / Q ˙ ) values; and the other on a bifurcating tree which emulates the anatomical structure of the lung. In the statistical model, the distribution becomes bimodal, whe...
Research has been undertaken to explore the possibility of using smart materials for the actuation of screw-in cartridge valves. Four types were considered and a piezoelectric (PZT) stack was selected as the most appropriate actuator. The concept of a spool valve piloted by a PZT valve was chosen for investigation. A mathematical model of a hydraul...
This paper addresses a controller design methodology for the hydraulic actuation of non-linear multi-body systems. It takes account of system uncertainties, envisaged system changes through added mass, positioning speed requirements, and vibration control. A mathematical model developed in the companion paper, Part 1, describes an experimental mult...
Modern engineering design is leading towards structures that are complex and lightweight. These structures often contain flexible and rigid components actuated through large displacements by a non-linear hydraulic system. Due to the increased system complexities, there is a need to define structural models that can be easily coupled to models of th...
In order to expand the operational capabilities of hydraulically actuated systems the development of new valves to allow of enhanced flow rates and bandwidth performance is required. Previously, the technical challenge in developing such valves was the need for large spool strokes to achieve the desired flow rates. However, this would then hinder t...
This paper explores the potential of isotope V/Q lung scans to quantify lung disease. Areas of restricted perfusion in subjects with a pulmonary embolus (PE) were identified in 3D reconstructions of V/Q images achieved using anatomical data from the Visible Human Project. From these, the extent of lung damage was quantified. Significant differences...
Fluid inertia within passageways of hydraulic components is known to have a significant impact on their dynamic response and fluid-borne noise characteristics. This inertance is often hard to quantify either theoretically or experimentally due to the complex nature of component geometries, and because it is related to dynamic, not steady-state beha...
Accurate predictions of pressure surges are crucial in many fluid-line systems. There are several techniques available for modelling flow transients in hydraulic pipelines, offering different advantages and disadvantages and therefore suiting different applications. In this paper four modelling methods are evaluated in terms of accuracy, computatio...
This paper considers the system dynamics associated with a hydraulic system moving a large flexible structure, namely the Gateshead Millennium Bridge. The hydraulic components possess a range of non-linear characteristics, which become coupled to the bridge structural dynamics. The bridge structure is lightly damped and may be represented by a line...
This paper discusses intrinsic safety, advocating its embodiment in design artefacts, as the most effective means to reduce hazards and also to reduce costs. At odds with this desirable goal, real-world designs tend to exhibit layering of protective devices to mitigate hazardous side effects of existing features, so introducing unnecessary complexi...
This paper discusses intrinsic safety, advocating its embodiment in design artefacts, as the most effective means to reduce hazards and also to reduce costs. At odds with this desirable goal, real-world designs tend to exhibit layering of protective devices to mitigate hazardous side effects of existing features, so introducing unnecessary complexi...
The wrist joint is highly complex and there remain unresolved problems to be overcome in designing a successful wrist joint prosthesis. Consequently, the results of total wrist joint replacements have been poor compared to those for hip and knee joint replacements. A multidisciplinary team of orthopaedic surgeons and engineers is working at Bath to...
The increasing use of simulation for both circuit and component analysis in the aircraft industry has come about due to the requirement for acceptable transient as well as steady state performance of aircraft systems. The computer simulation package, Bathfp, developed at the Fluid Power Centre, University of Bath, is suitable for investigations int...
This paper presents a modelling approach to the study of thermal-hydraulic performance in fluid power systems. A set of lumped parameter mathematical models are developed which are based on conservation of mass and energy for the system. The theoretical basis and modelling strategy are discussed for an open circuit containing a hydraulic pump, load...
This paper describes a dynamic model for slipper-pads that allows lift and tilt behavior to be predicted, including the effects of possible contact with the swashplate or slipper retaining plate. This model has been incorporated in the Bathfp simulation package and used to examine the dynamic stability of slipper-pads over the pumping cycle, and to...
The performance of hydraulic system employing counterbalance valves frequently encounter problem due to oscillation which are primarily due to the load inertia, volume of pressure system, response of the counterbalance valve and the flow at which the valve is required to regulate the load. This paper describes an application of CAD via a computer s...
The Engineering Design Centre (EDC) in fluid power systems, was established in the School of Mechanical Engineering, University of Bath in 1992 to develop computer-based techniques for fluid power systems design. This paper gives an overview of the research being undertaken at the EDC relating to: system design and performance evaluation using comp...
A Bathfp computer simulation model is given for a proposed ship traction winch system. This has been used to investigate the dynamic and steady state performance of the system under a wide range of operating conditions, involving lifting and lowering a load into and out of the sea. The purpose of the study was to assess the suitability of the desig...
The suction dynamics of axial piston pumps become more critical if the pump is to be used at high speeds. In order to prevent air-release and cavitation from occurring within the pump it is necessary to pressurise the pump inlet. As the speed of a pump is increased, higher boost pressures are required, due to the extra losses incurred through the s...
A mathematical model of the human respiratory system is being developed in order to simulate manned diving operations using various types of breathing equipment. A simulation study is presented of a human diving to a depth of 50 m, using a semi-closed re-breathing system with two different oxygen flow settings. A gas supply with 32.5 per cent oxyge...
The following topics are discussed: lung motion and gas flow; model of the nose and mouth; model of the tracheobronchial tree (trachea and respiratory pathways); model of the lung; polynomial representation of lung stiffness; model of pleural compartment; comparison of predicted breathing patterns with experimental data; block diagram analysis of t...
Modelling techniques have been developed to perform transient simulations of pneumatic components used in industrial engineering systems. The individual component models are connected to predict overall system performance using the software package Bath∫p. A position feedback control actuator system is used to show the application of the package to...
The development of mathematical models of the nasal passageways, tracheobronchial tree, alveolar and pleural compartments, and blood supply that are used to perform a detailed analysis of the gas exchange in the respiratory system is reported. The aim of the research is to use computer simulation to predict human interaction with underwater diving...
The computer simulation package BATHfp has been developed at the Fluid Power Centre, University of Bath to perform transient time domain simulations of fluid power systems. Utilities are provided which allow new models to be introduced into the component database. This enables the package to be tailored to particular dedicated areas of interest suc...
We have developed a computer model of chest-mounted counterlungs, which accounts for counterlung shape, effective volume, and pressure centroid. The model has been validated and the principles are applicable to other counterlung systems. The highly non-linear and discontinuous behavior of a counterlung is predicted by use of a sophisticated numeric...
In order to obtain a satisfactory fluid power system, an iterative design process must be employed. This will include circuit selection, component selection and performance assessment. Traditionally, performance assessment has been based on the use of steady state analysis and in some cases, dynamic analysis using linearisation techniques. However,...
The operational performance of underwater breathing systems is currently assessed using manned and unmanned testing. Due to the complexity of these systems, it is often difficult to understand fully the observed behaviour. Computer simulation is a well-established technique in the analysis of complicated dynamic systems and is considered an ideal t...
This paper discusses the application of plane wave theory to the modelling of pressure ripples generated by positive displacement pumps in high-pressure hydraulic systems. These ripples can lead to structural vibration of pipework and associated components and hence result in airborne noise. A clear understanding of the mechanism of pressure ripple...
BATH fp is a completely new simulation package for fluid power systems replacing the HASP package used at the Fluid Power Centre for over a decade. It is based on the WIMP paradigm using windows, icons, menus and pop-ups and minimises user keyboard interaction. The user builds the circuit to be studied in much the same way as it would be drawn by a...
This paper describes how computer simulation can be of benefit in the design and analysis of fluid power systems, and a strategy is outlined which should be of assistance to those wishing to undertake such analysis. A number of aspects of the simulation process are considered in detail. These include the following: use of simulation packages; liais...
This paper describes techniques used to determine the fluid borne noise characteristics of hydraulic systems. The experimental test method, which is based upon the measurement of pressure and flow fluctuations generated by positive displacement pumps, is described together with details of instrumentation. Test results are presented for four differe...
Citations
... Compared to other component-oriented, hydro-static simulation tools such as OHCS (Nakashima and Baba, 1989), Bathfp (Tilley et al., 1991), DSHplus (Kett, 1993), HOPSAN (Krus et al., 1991), ITI-SIM (Großmann and Uhlig, 1996), or MOSIHS (Piechnick and Feuser, 1994), the utilization of structural information as pursued by art deco goes beyond current simulation technology. ...
... Experimental approaches for the component sizing and matching purpose are, in general, time and cost intensive processes because they require series of climate simulated chassis dynamometer tests with expensive prototype components and vehicles. Accordingly, there have been many efforts to use numerical modeling approaches for the vehicle thermal management system development in order to reduce development cost and period [1][2][3][4][5][6][7][8][9][10]. Numerical tools can be very useful during the early stage of the system development especially for concept studies or feasibility studies. ...
... However, it is difficult and time-consuming to derive the mathematical model for the circuit and to construct the program for computer simulation. From the above-mentioned viewpoint, some exclusive simulation packages such as Bath-fp[1], DSH-plus[2], HOPSAN[3], AME-Sim[4], Ideafp[5] and OHC- Sim[6,7,8] have been developed. Using these simulation packages, an oil-hydraulic circuit can be easily constructed on the display by connecting oil-hydraulic component icons similar to oil-hydraulic symbols. ...
... Fluid passing through small orifices can impact the temperatures of the hydraulic system and consequently compromise the equipment's performance and damage its internal subcomponents. Previous studies discussed the influence of temperature variation on the system time and frequency response and aeroelastic requirements [2] [4] or the temperature behavior of the hydraulic system during normal operation [5][6] [7][8] [9]. ...
... 10,11 In literature, one will find various principles of piezoelectrically actuated flow control valves being presented, such as nozzle-flapper [12][13][14] and jet-deflector 15 piloted flow valves as well as direct drive valves with sliding spools. 9,[16][17][18][19] In contrast to piezoelectric bimorphs and ring benders, the use of piezoelectric stacks can be instrumental in reaching the goal of driving large-scale spools. However, strokes of commercially available piezoelectric stacks are much small with the deformation of about 0.1%-0.15% of their length, limiting 1 the flow rate. ...
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... To increase flow without hindering dynamic performance the use of multiple metering edges is proposed. This is achievable using the Hörbiger plate valve principle with an integrated high bandwidth piezoelectric multilayer actuator [2,3]. ...
... Bath University's Min Pan et al. have used high-speed rotary valves to control the flow and pressure of a hydraulic supply [33]. Actuators made from piezoelectric materials [34][35][36][37], magnetostrictive materials [38][39][40], or shape memory alloys [41,42] provide different ideas for valve actuators. Nevertheless, novel form actuators designed by voice coil actuators [43,44], a stepping motor [45,46], and magnetorheological (MR) fluid [47] are booming with the development of Industry 4.0 [1]. ...
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... While as a result, the pilot pressure must be high, which leads to additional energy consumption. 5,6 Due to the high spring stiffness, the stroke of the spool is often very short and accordingly a gradient orifice is almost impossible to achieve on such a short stroke. As a result, traditional LCVs always can only be used for bang-bang flow rate control, which makes the system have to employ another valve to control the load velocity. ...
... A rebreather can be viewed as a system that takes exhalation as an input and produces an output for inhalation. An advanced computer simulation model of the human respiration is dealt with in [14] and its application to semi-closed circuit underwater breathing equipment is discussed in [15]. For rebreather fault simulations, a simplistic respiration model is constructed in this section in accordance with European Standard EN14143:2003 [16]. ...
... A number of numerical optimisation approaches have previously been used to automatically size and select components in fluid power circuits by linking the algorithm to the fluid power simulation environment Bathfp (Tomlinson & Tilley, 1993). The algorithms used include Genetic Algorithms (Donne, 1993) and Tabu search (Connor and Tilley, 1998). ...
Reference: A multi-thread Tabu search algorithm
