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1
Cleave, Ra. "Active bandsaw control." Thesis, University of Canterbury. Mechanical Engineering, 2001. http://hdl.handle.net/10092/7189.
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This thesis investigates the modelling and active control of narrow and wide bandsaw blades, with application to the sawmilling industry. Strings, beams and plates are considered in the modelling work, with advances made in the modelling of exogenous influences and multispan saw blades. Beams and plates are considered in the control work, with classical and optimal controllers considered. Importance is placed on closed-loop robustness with respect to parametric variation, closed-loop performance in vibration suppression and in providing a physically realisable solution to the control problem.
In the string and beam work exogenous influences are modelled by pointwise and distributed forces, including; lateral stiffness, lateral damping and a "follower" force that comprises an in-line and a lateral component. Pointwise actuation and arbitrary disturbance forces as well as pointwise sensing are also included. Successful comparison with results of other contributors, as well as comprehensive experimental work, validates the modelling. The experimental validation also concentrates on system damping and the integration of sensing and actuation.
The plate work considers the single-span cutting blade presented by other contributors, and extends it to include saw guides and partial-span cutting forces. These cutting forces include damping, stiffness and follower loads, and act over a partial length of the cutting edge. While this three span model is not experimentally verified, it is shown to produce credible results.
The control work is in two parts. A comprehensive study of the robustness of various controllers with respect to translation speed and band tension is performed for the beam; theoretically and experimentally. The theory-practice gap was small regarding trends in robustness, but unmodelled effects such as the band weld degraded the agreement of absolute values at higher band speeds. Classical controllers were abandoned due to high frequency noise amplification, and a near optimal H∞ loop shaping controller was found to be superior to others of its type and various H₂ formulations. The plate work is entirely theoretical, but uses the same actuator and sensor dynamics that were successful in the beam work to maintain the physical feasability of the controllers. Both single span and multispan systems are considered, with the central cutting span of the blade being controlled via actuation and sensing of the upstream and downstream noncutting spans. Robustness studies were conducted, with satisfactory robustness achieved with respect to a large number of parameters. Furthermore, substantial increases in maximum allowable cutting loads were achieved, as well as reduced vibration energy.
The control actuation used in this work is electromagnetic force, with eddy current sensors used to sense the blade position. A noncontacting collocated actuatorsensor was developed that, with appropriate control of the winding current, performed excellently in both the validation and control work. Further development of this could lead to a versatile tool in experimental vibration analysis and distributed systems control research and applications.
2
Ibrahim, Kamarul Asri. "Active statistical process control." Thesis, University of Newcastle Upon Tyne, 1989. http://hdl.handle.net/10443/407.
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Most Statistical Process Control (SPC) research has focused on the development of charting techniques for process monitoring. Unfortunately, little attention has been paid to the importance of bringing the process in control automatically via these charting techniques. This thesis shows that by drawing upon concepts from Automatic Process Control (APC), it is possible to devise schemes whereby the process is monitored and automatically controlled via SPC procedures. It is shown that Partial Correlation Analysis (PCorrA) or Principal Component Analysis (PCA) can be used to determine the variables that have to be monitored and manipulated as well as the corresponding control laws. We call this proposed procedure Active SPC and the capabilities of various strategies that arise are demonstrated by application to a simulated reaction process. Reactor product concentration was controlled using different manipulated input configurations e.g. manipulating all input variables, manipulating only two input variables, and manipulating only a single input variable. The last two manipulating schemes consider the cases when all input variables can be measured on-line but not all can be manipulated on-line. Different types of control charts are also tested with the new Active SPC method e.g. Shewhart chart with action limits; Shewhart chart with action and warning limits for individual observations, and lastly the Exponentially Weighted Moving Average control chart. The effects of calculating control limits on-line to accommodate possible changes in process characteristics were also studied. The results indicate that the use of the Exponentially Weighted Moving Average control chart, with limits calculated using Partial Correlations, showed the best promise for further development. It is also shown that this particular combination could provide better performance than the common Proportional Integral (PI) controller when manipulations incur costs.
3
Matheu, Enrique E. "Active and Semi-Active Control of Civil Structures under Seismic Excitation." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30310.
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The main focus of this study is on the active and
semi-active control of civil engineering structures subjected
to seismic excitations. Among different candidate control
strategies, the sliding mode control approach emerges as a
convenient alternative, because of its superb robustness
under parametric and input uncertainties. The analytical
developments and numerical results presented in this
dissertation are directed to investigate the feasibility of
application of the sliding mode control approach to civil
structures. In the first part of this study, a unified treatment
of active and semi-active sliding mode controllers for civil
structures is presented. A systematic procedure, based on
a special state transformation, is also presented to obtain
the regular form of the state equations which facilitates the
design of the control system. The conditions under which
this can be achieved in the general case of control
redundancy are also defined. The importance of the
regular form resides in the fact that it allows to separate
the design process in two basic steps: (a) selection of a
target sliding surface and (b) determination of the
corresponding control actions. Several controllers are
proposed and extensive numerical results are presented to
investigate the performance of both active and semi-active
schemes, examining in particular the feasibility of
application to real size civil structures. These numerical
studies show that the selection of the sliding surface
constitutes a crucial step in the implementation of an
efficient control design. To improve this design process, a
generalized sliding surface definition is used which is based
on the incorporation of two auxiliary dynamical systems.
Numerical simulations show that this definition renders a
controller design which is more flexible, facilitating its
tuning to meet different performance specifications. This
study also considers the situation in which not all the state
information is available for control purposes. In practical
situations, only a subset of the physical variables, such as
displacements and velocities, can be directly measured. A
general approach is formulated to eliminate the explicit
effect of the unmeasured states on the design of the sliding
surface and the associated controller. This approach,
based on a modified regular form transformation, permits
the utilization of arbitrary combinations of measured and
unmeasured states. The resulting sliding surface design
problem is discussed within the framework of the classical
optimal output feedback theory, and an efficient algorithm
is proposed to solve the corresponding matrix nonlinear
equations. A continuous active controller is proposed
based only on bounding values of the unmeasured states
and the input ground motion. Both active and semi-active
schemes are evaluated by numerical simulations, which
show the applicability and performance of the proposed
approach.<br>Ph. D.
4
Khairallah, Ousama Said. "Robotics Control using Active Disturbance Rejection Control." Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1262832204.
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5
Abbaspour, Ali Reza. "Active Fault-Tolerant Control Design for Nonlinear Systems." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3917.
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Faults and failures in system components are the two main reasons for the instability and the degradation in control performance. In recent decades, fault-tolerant control (FTC) approaches were introduced to improve the resiliency of the control system against faults and failures. In general, FTC techniques are classified into two major groups: passive and active. Passive FTC systems do not rely on the fault information to control the system and are closely related to the robust control techniques while an active FTC system performs based on the information received from the fault detection and isolation (FDI) system, and the fault problem will be tackled more intelligently without affecting other parts of the system.
This dissertation technically reviews fault and failure causes in control systems and finds solutions to compensate for their effects. Recent achievements in FDI approaches, and active and passive FTC designs are investigated. Thorough comparisons of several different aspects are conducted to understand the advantages and disadvantages of different FTC techniques to motivate researchers to further developing FTC, and FDI approaches.
Then, a novel active FTC system framework based on online FDI is presented which has significant advantages in comparison with other state of the art FTC strategies. To design the proposed active FTC, a new FDI approach is introduced which uses the artificial neural network (ANN) and a model based observer to detect and isolate faults and failures in sensors and actuators. In addition, the extended Kalman filter (EKF) is introduced to tune ANN weights and improve the ANN performance. Then, the FDI signal combined with a nonlinear dynamic inversion (NDI) technique is used to compensate for the faults in the actuators and sensors of a nonlinear system. The proposed scheme detects and accommodates faults in the actuators and sensors of the system in real-time without the need of controller reconfiguration.
The proposed active FTC approach is used to design a control system for three different applications: Unmanned aerial vehicle (UAV), load frequency control system, and proton exchange membrane fuel cell (PEMFC) system. The performance of the designed controllers are investigated through numerical simulations by comparison with conventional control approaches, and their advantages are demonstrated.
6
Johnson, Martin Eric. "Active control of sound transmission." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243189.
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Huang, X. "Active control of aerodynamic instabilities." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237877.
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8
Tideman, Erik. "Control System for Active Camouflage." Thesis, Linköpings universitet, Institutionen för datavetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-122282.
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9
Cobelo, I. "Active control of distribution networks." Thesis, University of Manchester, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.685442.
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10
Aoki, Yohko. "Strain transducers for active control." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/66297/.
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This thesis presents the results of a theoretical and experimental study of active vibration control using velocity feedback with piezoceramic actuator(s) and closely located velocity sensor(s). The first part of the thesis presents modeling and design studies for a square piezoceramic actuator used to implement a single channel velocity feedback control with a velocity sensor at its center. A fully coupled mobility model of the panel with a square piezoceramic patch actuator is introduced and experimentally validated in order to predict the sensor-actuator open loop response over much wider frequency range than is commonly used, so that the stability of the feedback control loop can be properly assessed using the Nyquist criterion. These simulations suggest that increasing the width and reducing the thickness of the square actuator improves the control performance of a single channel velocity feedback control loop in the case considered. The second part of this thesis investigates a new configuration of the velocity feedback control system, which is composed of a piezoceramic actuator shaped as isosceles triangle with a velocity sensor at its tip. A fully coupled mobility model has been developed, which predicts the response of the sensor-actuator pair more accurately than the conventional modeling method. The implementation of a 16 channel decentralized control system using triangular actuator has been experimentally demonstrated. Significant levels of attenuation, up to 20 dB, are achieved at the first few resonant peaks in term of both structural vibration and sound radiation. Closed loop measurements have highlighted that the control performance are significantly improved by increasing the base length and/or the height of the triangle actuators, with the limitation that the increase of the height reduces the usable frequency range of the control system.
11
Reynolds, Matthew. "Active control of viscoelastic metamaterials." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/377011/.
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Metamaterials have been the subject of significant interest over the past decade due to their ability to produce novel acoustic behaviour beyond that seen in naturally occurring media. As well as their potential in acoustic cloaks and lenses, of particular interest is the appearance of band gaps which lead to very high levels of attenuation across the material within narrow frequency ranges. Unlike traditional periodic materials which have been employed at high frequencies, the resonant elements within metamaterials allow band gaps to form within the long wavelength limit; at low frequencies where it is most difficult to design satisfactory passive isolation solutions. Hence metamaterials may provide a useful path to high performance, low frequency isolation. Passively these band gaps occur over a narrow bandwidth, however the inclusion of active elements provide a method for enhancing this behaviour and producing attenuation over a broad band. Two active metamaterials are investigated in this thesis, first a novel viscoelastic metamaterial is developed that achieves double negativity and could be employed as a high performance vibration isolator at low frequencies. A prototype is produced, the band gap confirmed in the laboratory, and active control is applied to create a wideband region of attenuation. Next an acoustic metamaterial consisting of an array of Helmholtz resonators is presented and it is shown that such a metamaterial has a resonant band gap and dispersive density and bulk modulus. The acoustic metamaterial is produced using 3D printing techniques and the predicted behaviour confirmed in the laboratory. Finally an active Helmholtz resonator is introduced as a pathway to creating an active acoustic metamaterial and the potential for band gap and material parameter manipulation is investigated before a prototype resonator is produced and feedback controllers applied, enhancing the band gap attenuation.
12
Tu, Yifeng. "Multiple Reference Active Noise Control." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36790.
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The major application of active noise control (ANC) has been
focused on using a single reference signal; the work on
multiple reference ANC is very scarce. Here, the behavior
of multiple reference ANC is analyzed in both the frequency
and time domain, and the coherence functions are provided to
evaluate the effectiveness of multiple reference ANC.
When there are multiple noise sources, multiple reference
sensors are needed to generate complete reference signals.
A simplified method combines those signals from multiple
reference sensors into a single reference signal. Although
this method could result in satisfactory noise control
effects under special circumstances, the performance is
generally compromised. A widely adopted method feeds each
reference signal into a different control filter. This
approach suffers from the problem of ill-conditioning when
the reference signals are correlated. The problem of
ill-conditioning results in slow convergence rate and high
sensitivity to measurement error especially when the FXLMS
algorithm is applied. To handle this particular problem,
the decorrelated Filtered-X LMS (DFXLMS) algorithm is
developed and studied in this thesis.
Both simulations and experiments have been conducted to
verify the DFXLMS algorithm and other issues associated
with multiple reference ANC. The results presented herein
are consistent with the theoretical analysis, and favorably
indicate that the DFXLMS algorithm is effective in improving
the convergence speed.
To take the maximum advantage of the TMS320C30 DSP board
used to implement the controller, several DSP programming
issues are discussed, and assembly routines are given in
the appendix. Furthermore, a graphical user interface (GUI)
running under Windows' environment is introduced. The main
purpose of the GUI is to facilitate parameters modification,
real time data monitoring and DSP process control.<br>Master of Science
13
Hanagan, Linda M. "Active control of floor vibrations." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-164824/.
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14
Abouel-Nour, Aly. "Active control of vehicle suspension." Thesis, University of Leeds, 1989. http://etheses.whiterose.ac.uk/2552/.
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Various types of actively controlled suspension systems for automotive or agricultural applications are theoretically studied on the basis of the well known quarter car model subjected to realistic inputs chosen to represent road surface/forward vehicle speed combinations for a range of different conditions. The vehicle response is evaluated through the performance criteria (the ride comfort, dynamic tyre load and suspension working space) and power requirements (the power input to actuator, power dissipated in damper or actuator and power fluctuation in spring and tyre). The range of suspension systems includes fully active, semi-active, slow-active, single state feedback active, two state switchable damper, continuously variable damper and conventional passive. Computer programmes relating to the general dynamic modelling of ground vehicle suspension systems (generation of the artificial road, random process analysis and human response criteria) are designed. Computer programmes relating specifically to vehicle ride (linear or non linear), derivation of responses and power calculations for linear or non linear models, as well as performance criteria and optimal control of vehicle suspension are also designed. The switchable damper system which involves continuously switching between two discrete settings is of considerable interest because such dampers are currently available. It is shown to offer worthwhile improvements over passive systems in terms of ride performance if a simple control law is followed. Linear optimal control theory is used to obtain the optimal feedback gains of the fully active and slow-active suspension systems. The behaviour of the fully active linear control systems and the possibility of improving their performance by using a non-linear control law is investigated. The performances of the four and two state feedback slow-active systems, using an actuator with limited frequency response up to 3 Hz, are similar. In terms of the power demand, there is little difference between the fully active and slow-active systems, configured with a conventional passive spring in parallel with the actuator, and their ride performances are also similar. The behaviour of the semi-active systems are evaluated with a control law based exactly on the optimal control of the fully active system, except that no power input is available. A method of comparing performance and power requirements is based on the practical viewpoint that the suspension designer is essentially allocated a given amount of working space and must optimise the suspension within this constraint. Hence, all the competing systems are compared on the basis of equal workspace contours. Conclusions and suggestions for further work are discussed with particular reference to the relationship between the predictive models and their practical usefulness in assisting the designer of advanced suspension systems for on and off - road vehicles.
15
Li, Shi. "Modeling of active crack damage control and the active fatique damage control of adhesive joint." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-08222009-040330/.
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16
Gopal, Vinod Kumar. "Active Stirling Engine." Thesis, University of Canterbury. Electrical and Computer Engineering, 2012. http://hdl.handle.net/10092/7306.
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Micro Combined Heat and Power systems or microCHP systems generate heat and electricity for a home. Stirling engines are widely used as prime movers in microCHP applications. Stirling engine is an external combustion engine having an enclosed working fluid (as helium) that is alternately compressed and expanded to operate a piston. The displacer shuttles the working fluid between the hot and cold ends. The piston is coupled to a transmission and to an electrical machine to generate power. Conventional Stirling engines are not controllable to a great degree. The piston and displacer are connected to the same crank and they maintain the same phase difference throughout the cycle. Also the piston and displacer are normally constructed to move in a sinusoidal fashion.
The Active Stirling Engine is a new concept introduced in this thesis which has a free displacer. The displacer is driven separately compared to a coupled drive in conventional Stirling engines. The displacer motion can be non-linear with dwell at each ends of the stroke, opening up the possibilities to increase the pressure volume diagram which indicates the work done by the engine. A separately driven displacer also allows introducing phase control and stroke control to improve the controllability of a Stirling engine.
This thesis examines the effect of non-linear displacer motion and phase control of the displacer on Stirling engine performance. Simulations are performed in Sage, the leading Stirling engine simulation software, to understand the effect of displacer phase control. A test rig is constructed with the actively controlled displacer connected to a linear machine controlled by a programmable servo. Heat is applied to the test rig though an electric heating coil. The test rig is charged with nitrogen at 20Bar pressure. The power piston is connected to a rotating electrical machine via the transmission. The rotating electrical machine is used to start the engine and to act as the generator.
The test rig is instrumented to determine the linear position of the displacer and piston, angular position of the rotating electrical machine shaft, temperatures, pressures and flow. A LabVIEW™ based data acquisition system is set up to capture data from the test rig. Data is collected at various test cases. The simulation result is compared against post processed data.
An efficiency improvement of 15% is achieved using this method and is demonstrated experimentally. Applications in micro combined heat and power systems utilising the improved efficiency due to non linear motion and controllability due to phase control are explored in this thesis.
17
Hedborg, Mårten, and Patrik Grylin. "Active Noise Control of a Forest Machine Cabin." Thesis, Linköping University, Department of Electrical Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-9065.
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<p>Today, a high noise level is considered a problem in many working environments. The main reason is that it contributes to stress and fatigue. Traditional methods using passive noise control is only practicable for high frequencies. As a complement to passive noise control, active noise control (ANC) can be used to reduce low frequency noise. The main idea of ANC is to use destructive interference of waves to cancel disturbing noises.</p><p>The purpose of this thesis is to design and implement an ANC system in the driver's cabin of a Valmet 890 forest</p><p>machine. The engine boom is one of the most disturbing noises and therefore the main subjective for the ANC system to suppress.</p><p>The ANC system is implemented on a Texas Instrument DSP development starter kit. Different FxLMS algorithms are evaluated with feedback and feedforward configurations.</p><p>The results indicate that an ANC system significantly reduces the sound pressure level (SPL) in the cabin. Best performance of the evaluated systems is achieved for the feedforward FxLMS system. For a commonly used engine speed of 1500 rpm, the SPL is reduced with 17 dB. The results show fast enough convergence and global suppression of low frequency noise.</p>
18
Szoke, Matthew. "Trailing edge noise control using active flow control methods." Thesis, University of Bristol, 2019. http://hdl.handle.net/1983/e45a9e22-3146-4467-90c4-01d3b6aebeb3.
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Active flow control methods are investigated experimentally with the aim of reducing the trailing edge noise on a zero pressure gradient flat plate test rig. Flush-mounted microphones are embedded in the wall of the plate between the flow control section and the trailing edge to study the surface pressure fluctuations exposed on the wall by the turbulent boundary layer. Three different types of active flow control techniques are considered, namely uniform inclined flow suction, uniform inclined flow injection and inclined transverse jets. The velocity statistics reveal that inclined flow suction can relaminarize the boundary layer flow. As the boundary layer reaches a laminar state, flow suction significantly reduces the trailing edge noise at mid-frequencies, while some penalties observed at low and high frequencies. Once laminarisation is achieved, the noise reduction capabilities of flow suction reach its maximum, and further increasing the suction rate does not provide any additional benefit of noise reduction. Flow injection triggers the boundary layer separation and the development of a shear layer. As a result, the trailing edge noise increases in a broadband manner. Increasing the blowing rate to moderate levels can reduce the trailing edge noise at mid and high frequencies, while noise increase is observed at low frequencies. A more significant noise reduction can be achieved at high injection angles and blowing rates when the boundary layer entirely separates from the wall. Finally, a single line of jet nozzles is installed parallel to the trailing edge of the plate. The individual jets merge downstream of the jet nozzles and they form a layer of jet fluid characterized by low energy content. The estimates of the trailing edge noise show that jets injection can reduce the trailing edge noise over the whole range of frequencies under analysis.
19
Ulker, Fatma Demet. "Active Vibration Control Of Smart Structures." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1098409/index.pdf.
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The purpose of this thesis was to design controllers by using H1 and ¹<br>control strategies
in order to suppress the free and forced vibrations of smart structures. The smart structures
analyzed in this study were the smart beam and the smart ¯<br>n. They were aluminum passive
structures with surface bonded PZT (Lead-Zirconate-Titanate) patches. The structures were
considered in clamped-free con¯<br>guration.
The ¯<br>rst part of this study focused on the identi¯<br>cation of nominal system models of the
smart structures from the experimental data. For the experimentally identi¯<br>ed models the
robust controllers were designed by using H1 and ¹<br>-synthesis strategies. In the second part,
the controller implementation was carried out for the suppression of free and forced vibrations
of the smart structures.
Within the framework of this study, a Smart Structures Laboratory was established in the
Aerospace Engineering Department of METU. The controller implementations were carried out
by considering two di®<br>erent experimental set-ups. In the ¯<br>rst set-up the controller designs were based on the strain measurements. In the second approach, the displacement measurements,
which were acquired through laser displacement sensor, were considered in the controller design.
The ¯<br>rst two °<br>exural modes of the smart beam were successfully controlled by using
H1 method. The vibrations of the ¯<br>rst two °<br>exural and ¯<br>rst torsional modes of the smart
¯<br>n were suppressed through the ¹<br>-synthesis. Satisfactory attenuation levels were achieved for
both strain measurement and displacement measurement applications.
20
Forsgren, Fredrik. "Active Noise Control in Forest Machines." Thesis, Umeå universitet, Institutionen för fysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-48661.
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Achieving a low noise level is of great interest to the forest machine industry. Traditionally this is obtained by using passive noise reduction, i.e. by using materials for sound isolation and sound absorption. Especially designs to attenuate low frequency noise tend to be bulky and impractical from an installation point of view. An alternative solution to the problem is to use active noise control (ANC). The basic principle of ANC is to generate an anti-noise signal designed to destructively interfere with the unwanted noise. In this thesis two algorithms (Feedback FxLMS and Feedforward FxLMS) are implemented and evaluated for use in the ANC-system. The ANC-system is tuned to the specific environment in the driver’s cabin of a Komatsu forest machine. The algorithms are first tested in a simulated environment and then in real-time inside a forest machine. Simulations are made both in Matlab and in C using both generated signals and recorded signals. The C code is implemented on the Analog Devices Blackfin DSP card BF526. The result showed a significantly reduction of the sound pressure level (SPL) in the driver’s cabin. The noise attenuation obtained using the Feedback FxLMS was approximately 14 dB for a tonal 100 Hz signal and 11 dB using recorded engine noise from a forest machine at 850 rpm.
21
Sun, Xiao-Dong. "Active control of aircraft using spoilers." Thesis, Imperial College London, 1993. http://hdl.handle.net/10044/1/11324.
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Munn, Jacqueline Marie. "Virtual sensors for active noise control /." Title page, abstract and table of contents only, 2003. http://web4.library.adelaide.edu.au/theses/09PH/09phm9668.pdf.
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Chang, Min-Yung. "Active vibration control of composite structures." Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-09162005-115021/.
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Rybing, Peter. "Active Noise Control in Home Environment." Thesis, KTH, Reglerteknik, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-109486.
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Disturbing noise is a growing problem in the society. Also in the home environment noise making devices exist, for example the vacuum cleaner. A simple way to decrease the annoyance from a vacuum cleaner is to use personal passive ear defenders. A problem with passive ear defenders is that they also attenuate wanted signals, such as speech or music. In this thesis a pair of prototype active ear defenders for vacuum cleaner noise attenuation have been developed and evaluated. Active noise control technology was used, which solved the problem with wanted signal attenuation. A measured noise reference was used with a pair of open earphones as actuator. The overall cancellation performance of the prototype system was quite low for vacuum cleaner noise. Due to that the coherence between the measured noise reference and the unwanted noise was low. Wanted signals were shown to be just slightly affected by the prototype system.
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Inyiama, Fidelis Chidozie. "Active control of hydrodynamic slug flow." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/7996.
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Multiphase flow is associated with concurrent flow of more than one phase (gas-liquid, liquid-solid, or gas-liquid-solid) in a conduit. The simultaneous flow of these phases in a flow line, may initiate a slug flow in the pipeline. Hydrodynamic slug flow is an alternate or irregular flow with surges of liquid slug and gas pocket. This occurs when the velocity difference between the gas flow rate and liquid flow rate is high enough resulting in an unstable hydrodynamic behaviour usually caused by the Kelvin-Helmholtz instability.
Active feedback control technology, though found effective for the control of severe slugs, has not been studied for hydrodynamic slug mitigation in the literature. This work extends active feedback control application for mitigating hydrodynamic slug problem to enhance oil production and recovery.
Active feedback Proportional-Integral (PI) control strategy based on measurement of pressure at the riser base as controlled variable with topside choking as manipulated variable was investigated through Olga simulation in this project. A control system that uses the topside choke valve to keep the pressure at the riser base at or below the average pressure in the riser slug cycle has been implemented. This has been found to prevent liquid accumulation or blockage of the flow line.
OLGA (olga is a commercial software widely tested and used in oil and gas industries) has been used to assess the capability of active feedback control strategy for hydrodynamic slug control and has been found to give useful results and most interestingly the increase in oil production and recovery. The riser slugging was suppressed and the choke valve opening was improved from 5% to 12.65% using riser base pressure as controlled variable and topside choke valve as the manipulated variable for the manual choking when compared to the automatic choking in a stabilised operation, representing an improvement of 7.65% in the valve opening. Secondly, implementing active control at open-loop condition reduced the riser base pressure from 15.3881bara to 13.4016bara.
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Li, Xiao Dong. "Active vibration control of vehicle suspension." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=67007.
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Structure-borne noise generated by tire contact on road irregularities is a very important factor in interior vehicle noise. This kind of low-frequency noise can seriously affect the driver's concentration and passenger comfort. In order to reduce this vibration-induced noise, an active vibration control of the vehicle suspension is proposed, as opposed to acoustic noise control. Since modeling uncertainties are inevitable in characterizing the dynamics of the vibration transmission path, robust feedback controllers are considered. In this thesis, an H-infinity robust controller and a mu-synthesis robust controller are designed to reduce the vibrations using actuators acting directly on the suspension. First, closed-loop simulation results are obtained on a quarter-car suspension at the Université de Sherbrooke, showing a significant reduction in vibration. Second, simulation of the controllers is also conducted on a real car. Closed-loop test results are presented and the effectiveness of the robust feedback controllers is discussed.<br>Le bruit de vibration structurelle produit par le contact des pneus du véhicule sur la surface de la route est un facteur important du bruit à l'intérieur du véhicule. Ce type de bruit à basse fréquence peut affecter sérieusement la concentration du conducteur et le confort des passagers. De manière à réduire ce bruit de vibration, un contrôle actif de vibration dans la suspension du véhicule est proposé, en contraste avec la réduction active de bruit acoustique. Puisqu'il est inévitable d'avoir des incertitudes dans le modèle de la dynamique de transmission de la vibration, des contrôleurs rétroactifs robustes sont considérés. Dans cette thèse, un contrôleur robuste H-infini et un contrôleur à synthèse mu sont conçus pour réduire la vibration en utilisant des actionneurs agissant directement sur la suspension. En premier lieu, des résultats de simulation obtenus sur une suspension d'une seule roue à l'Université de Sherbrooke démontrent une réduction significative de la vibration. Puis, une simulation des contrôleurs est effectuée sur le modèle de la voiture. Les résultats des tests en boucle fermée sont présentés et l'efficacité des contrôleurs rétroactifs robustes est discutée.
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Li, Yong. "Active control of boundary layer instabilities." Thesis, Queen Mary, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413644.
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Ashworth, Anthony Ian. "Active control of V/STOL aircraft." Thesis, Lancaster University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296678.
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Hancock, Matthew. "Vehicle handling control using active differentials." Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/8075.
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This thesis describes an investigation into vehicle handling control using active differentials in the rear axle of a motor vehicle. Such devices are able to transfer torque between the rear wheels and have traditionally been used to improve traction whilst minimising the impact on vehicle handling. However, the capacity to generate a lateral torque difference across an axle also gives them the potential to be used for yaw moment control. In order to generate a rigorous assessment of this potential, the investigation is carried out in three distinct phases. Firstly, an analysis of the scope for modifying vehicle handling given unrestricted control over torque transfer between the rear wheels is carded out in the simulation environment. For this purpose an idealised yaw sideslip controller is developed. This is used to show that an ideal active differential can have significant yaw moment authority in terms of generating both understeer and oversteer and that this can be used to actively modify a vehicle's handling balance and apply stability control at the limits of adhesion. In the second phase, the capabilities of two types of contemporary active differential, the torque vectoring differential (TVD) and active limited slip differential (ALSID), are then assessed against the ideal differential and against a brake based yaw moment controller. TVDs are found to be able to offer very similar performance to both their ideal counterpart and to the brake based system. They Gan also deliver this performance with a fraction of the energy loss that is observed in the brakes, thus making TVDs a viable proposition for applying continuous yaw control below the limits of adhesion. ALSDs, on the other hand do not offer equivalent functionality to an ideal active differential but are still shown to be very effective stability control devices. In the third phase, the ALSID results are validated on a prototype vehicle where it is shown that they do indeed offer substantial stability improvements both on high and low-P surfaces. However in order to deliver such benefits and be practical for implementation, it is also shown that significant redevelopment of the idealised controller is required. Finally, with the ALSID operating alongside a commercial brake based stability control system, it is proven that substantial reductions in brake intervention can be achieved without significant controller integration.
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Sansawatt, Thipnatee Punim. "Adaptive control for active distribution networks." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/6268.
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Rise of the global environmental awareness and climate change impacts caused by greenhouse gases emissions brings about a revolution in the power and energy industries to reduce fossil fuels and promote low-carbon and renewable distributed generation (DG). The new dimensions, mainly encouraged by the governments’ legislative targets and incentives, have allowed the development of DG worldwide. In the U.K., renewable DG especially wind is being connected on distribution networks and ranges widely in scales. Despite the growing number of potential DG sites, the surplus generation present on the passive networks can lead to some technical problems. In particular, rural networks where wind farms exist are prone to voltage rise and line thermal constraints. In order to accommodate new DG and ensure security of supply and network reliability, active management to mitigate these issues are required. In addition, the duties to provide cost-effective DG connections at avoided expensive investment incurred from conventional solutions, e.g., reinforcement and maintain robust network are a major challenge for Distribution Network Operators (DNOs). This thesis endeavours to develop an adaptive control scheme that provides local and real-time management against voltage variations and line capacity overload at the point of wind connections on rural distribution networks. Taking into account maximising power exports and providing an economically-viable control scheme, the wind turbine’s capability, comprising reactive power control and active power curtailment, is used. Whilst the thesis concentrates on the decentralised control applying several different algorithms, in addition, semi-coordinated and centralised approaches that adopt on-load tap changing transformers’ regulation and Optimal Power Flow tool are developed. Comparisons of these approaches based upon measures, i.e., economics, DG penetration and performance are determined. As an outcome, the developed scheme can enable growing integration of renewable DG on distribution networks and can be seen as an interim solution for the DNOs towards Smart Distribution Networks.
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Turner, Michael James. "Active control of moving coil loudspeakers." Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531597.
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Lane, Jeremy David. "Active Control of Noise Through Windows." Thesis, University of Canterbury. Mechanical Engineering dept, 2013. http://hdl.handle.net/10092/10523.
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Windows are a weakness in building facade sound transmission loss (STL). This coupled with the detrimental effects of excessive noise exposure on human health including: annoyance, sleep deprivation, hearing impairment and heart disease, is the motivation for this investigation of the STL improvements active noise control (ANC) of windows can provide.
Window speaker development, ANC window experiments and analytical modelling of ANC windows were investigated. Five different window speaker constructions were characterised then compared with a previously developed window speaker. ANC window testing used three different ANC configurations and was performed in two different
environments, one with a reverberant receiving room, and the other with an anechoic receiving room. Optimisation of ANC systems with particular control source locations was the aim of the modelling. This enabled comparison with the ANC window tests and would aid in further development of ANC windows.
Window speaker constructions were characterised by sound pressure level (SPL) measurements performed in an anechoic room. These measurements were made in a way that enabled comparison with the previously developed window speaker.
Total sound energy reduction calculations were used to determine the relative performance of the tested ANC windows.
An STL model, based on a modal panel vibration model, was initially created and verified against published STL data before it was expanded to include ANC control sources. The model was used to simulate the performed anechoic environment tests and an ideal ANC case.
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Houlston, Paul Robert. "Active vibration control of rotating machines." Thesis, University of Nottingham, 2007. http://eprints.nottingham.ac.uk/10275/.
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Second order matrix equations arise in the description of real dynamical systems. Traditional modal control approaches utilise the eigenvectors of the undamped system to diagonalise the system matrices. Any remaining off-diagonal terms in the modal damping matrix are discarded. A regrettable automatic consequence of this action is the destruction of any notion of the skew-symmetry in the damping. The methods presented in this thesis use the `Lancaster Augmented Matrices' (LAMs) allowing state space representations of the second order systems. `Structure preserving transformations' (SPTs) are used to manipulate the system matrices whilst preserving the structure within the LAMs. Utilisation of the SPTs permits the diagonalisation of the system mass, damping and stiffness matrices for non-classically damped systems. Thus a modal control method is presented in this thesis which exploits this diagonalisation. The method introduces independent modal control in which a separate modal controller is designed in modal space for each individual mode or pair of modes. The modal displacements and velocities for the diagonalised systems are extracted from the physical quantities using first order SPT-based filters. Similarly the first order filters are used to translate the modal force into the physical domain. Derivation of the SPT-filters is presented together with a method by which one exploits the non-uniqueness of the diagonalising filters such that initially unstable filters are stabilised. In the context of active control of rotating machines, standard optimal controller methods enable a trade-off to be made between (weighted) mean-square vibrations and (weighted) mean-square control forces, or in the case of a machines controlled using magnetic bearings the currents injected into the magnetic bearings. One shortcoming of such controllers for magnetic bearings is that no concern is devoted to the voltages required. In practice, the voltage available imposes a strict limitation on the maximum possible rate of change of control force (force slew rate). This thesis presents a method which removes the aforementioned existing shortcomings of traditional optimal control. Case studies of realistic rotor systems are presented to illustrate the modal control and control force rate penalisation methods. The system damping matrices of the case studies contain skew-symmetric components due to gyroscopic forces typical of rotating machines. The SPT-based modal control method is used to decouple the non-classically damped equations of motion into n single degree of freedom systems. Optimal modal controllers are designed independently in the modal space such that the modal state, modal forces and modal force rates are weighted as required. The SPT-based modal control method is shown to yield superior results to the conventional notion of independent modal space control according to reasonable assessment.
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Nicholson, Guy Charles. "The active control of acoustic impedance." Thesis, University of Salford, 1994. http://usir.salford.ac.uk/14778/.
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The application of an active control force on a thin-walled acoustic boundary can modify the motional dynamics, and so influence the impedance presented to incident waves. This impedance determines transmission of acoustic energy, reflection of acoustic waves from the boundary and absorption of incident energy. This thesis studies control systems that generate control forces for the active control of surface acoustic impedance. The proposed systems rely on measurement of the acoustic pressure and surface velocity of the boundary. The systems can use adaptive digital signal processing, which offers significant advantages over non-adaptive techniques. The active control of the specific acoustic impedance of a loudspeaker that terminates a waveguide for axially propagating plane waves provides a motivating problem. Theoretical analysis establishes the control of specific acoustic impedance of a simple compliantly-suspended piston by a control force. Operational constraints of a physical piston define theoretical operating limits for controlled specific acoustic impedances. The control systems use either feedback or feed-forward techniques for which theoretical treatment reveals restrictions on the range of controlled specific acoustic impedance. A novel result is that conventional implementations of the control systems can be unstable for certain desired impedances unless feedback cancellation is used. Digital feedback techniques are less effective for broader frequency bandwidth where feed-forward techniques may work. Theoretical analysis produces solutions that confirm the feasibility of these control techniques for the active control of specific acoustic impedance. Potential errors in the implementation of the systems have predictable effects on the controlled specific acoustic impedance. Experimental results support the theoretical work presented in this thesis, demonstrating active control of specific acoustic impedance for normally incident acoustic plane waves. An adaptive digital feed-forward control system creates desired specific acoustic impedances for band-limited noise and transient signals.
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Hopper, David John Frederick. "Active control of V/STOL aircraft." Thesis, University of Salford, 1990. http://usir.salford.ac.uk/14698/.
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Vertical/Short Take-Off arid Landing (V/STOL) fighter aircraft are characterised by increased control complexity caused by the extra degree ol freedom. This can result in a high pilot workload which may be alleviated with the careful application of active flight control. However, the advent of control configured vehicles demands that the controller design must be part of a fully integrated and iterative aircraft design; hence it must allow the two-way flow of design information. In this thesis a suitable controller design method is developed to solve this two-fold problem. The method is based upon a singular perturbation analysis which is used to expose the underlying dynamics of a closed-loop state-space system. developments are described which allow high-order, dynamically complex parasitics, such as actuators, to be included in the design. Furthermore, the method gives the designer insight into the problem allowing tuning and engineering trade-offs to be performed intelligently with a two-way flow of design information. The end result is a robust high-gain multivariable controller. In order fully to develop arid analyse the method it has been applied to a representative non-linear time-varying aircraft simulation model. This LS supplied by the Royal Aerospace Establishment, Bedford. The necessary slate-space matrices are otitairted by lirLearisirig the model at several different flight cases. This occurs over a wide flight envelope, from hover to 300 Kts, and consequently the multivariable control laws are implemented using gain scheduling. Finally, task tailored control and handling qualities requirements are derived for a V/STOL aircraft in the form of a design brief. This design brief is then fulfilled by designing a controller which alleviates pilot workload during transitions from jet-borne to fully wing-borne flight (and vice versa).
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Truscott, A. J. "Control studies in active suspension systems." Thesis, University of Manchester, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282524.
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Chan, T. M. "Active control of sound in ducts." Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390327.
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Tseng, Wen-Kung. "Sound minimisation for local active control." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342925.
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Jenkins, Michael David. "Active control of periodic machinery vibrations." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.480701.
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Hillis, Andrew John. "Adaptive control of active engine mounts." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416822.
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Wang, Lin. "Active control of fluid-borne noise." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501639.
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Fluid-borne noise is one of the main components of hydraulic noise. Its attenuation may have a significant effect on the cost of hydraulic systems. Standard passive silencers and dampers can be useful in reducing it in certain frequency ranges; however, these tend to be heavy, bulky and expensive. Active control algorithms, which are a comparatively recent means of reducing fluid-borne noise, can be applied to overcome this compromise. The work presented in this thesis is the development of some active control algorithms utilized in a simple hydraulic system to cancel a number of harmonic orders of fluid-borne noise generated by a servo valve or a real pump. To realize cancellation the filtered reference least mean square (FXLMS) adaptive control method is mainly presented. Furthermore, a fast response servo valve is applied as an actuator to generate a proper anti-noise flow signal in real-time. For simplicity, an off-line identification method for the secondary path is applied in the time invariant working condition. Moreover, ripple reflection from both ends of the hydraulic circuit can produce different effects under different working conditions. In order to execute the cancellation without any prior information about the dynamics of hydraulic systems, the on-line secondary path identification method is discussed. However, in this algorithm an auxiliary white-noise signal applied to an on-line method may contribute to residual noise and an extra computation burden may be added to the whole control system. The performance of these control algorithms is firstly investigated via simulation in a hydraulic pipe model and the real-time application on a test rig using a servo valve as a noise source. Finally, these schemes are realized in a simple hydraulic system with a real pump noise source. The fluid-borne noise can be attenuated by about 20 dB in normal working conditions.
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Maldonado-Mercado, Julio Cesar. "Passive and active control of structures." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36654.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1995.<br>Includes bibliographical references (leaves 94-98).<br>by Julio Cesar Maldonado-Mercado.<br>M.S.
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Kokossalakis, George 1976. "Neural network based active structural control." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/80945.
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Tsai, Frank J. (Frank Jin-Fong) 1976. "Distributed active control for tension structures." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/81544.
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Pinsley, Judith Ellen. "Active control of centrifugal-compressor surge." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/39016.
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Abdul, Muthalif Asan Gani. "Active control of high-frequency vibration." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612225.
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Scruggs, Jeffrey. "Active, Regenerative Control of Civil Structures." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/34332.
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An analysis is presented on the use of a proof-mass actuator as a
regenerative force actuator for the mitigation of earthquake
disturbances in civil structures. A proof-mass actuator is a machine
which accelerates a mass along a linear path. Such actuators can
facilitate two-way power flow. In regenerative force actuation, a bi-
directional power-electronic drive is used to facilitate power flow
both to and from the proof-mass actuator power supply. With proper
control system design, this makes it possible to suppress a disturbance
on a structure using mostly energy extracted from the disturbance
itself, rather than from an external power source.
In this study, three main objectives are accomplished. First, a new
performance measure, called the "required energy capacity," is proposed
as an assessment of the minimum size of the electric power supply
necessary to facilitate the power flow required of the closed-loop
system for a given disturbance. The relationship between the required
energy capacity and the linear control system design, which is based on
positive position feedback concepts, is developed. The dependency of
the required energy capacity on hybrid realizations of the control law
are discussed, and hybrid designs are found which minimize this
quantity for specific disturbance characteristics.
As the second objective, system identification and robust estimation
methods are used to develop a stochastic approach to the performance
assessment of structural control systems, which evaluates the average
worst-case performance for all earthquakes "similar" to an actual data
record. This technique is used to evaluate the required energy
capacity for a control system design.
In the third objective, a way is found to design a battery capacity
which takes into account the velocity rating of the proof-mass
actuator. Upon sizing this battery, two nonlinear controllers are
proposed which automatically regulate the power flow in the closed-loop
system to accommodate a power supply with a finite energy capacity,
regardless of the disturbance size. Both controllers are based on a
linear control system design. One includes a nonlinearity which limits
power flow out of the battery supply. The other includes a
nonlinearity which limits the magnitude of the proof-mass velocity.
The latter of these is shown to yield superior performance.<br>Master of Science
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Sun, Guohua. "Active Control of Impact Acoustic Noise." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1413542213.
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Lau, M. W. S. "Active vibration control at machinery feet." Thesis, Aston University, 2000. http://publications.aston.ac.uk/15340/.
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The unmitigated transmission of undesirable vibration can result in problems by way of causing human discomfort, machinery and equipment failure, and affecting the quality of a manufacturing process. When identifiable transmission paths are discernible, vibrations from the source can be isolated from the rest of the system and this prevents or minimises the problems. The approach proposed here for vibration isolation is active force cancellation at points close to the vibration source. It uses force feedback for multiple-input and multiple-output control at the mounting locations. This is particularly attractive for rigid mounting of machine on relative flexible base where machine alignment and motions are to be restricted. The force transfer function matrix is used as a disturbance rejection performance specification for the design of MIMO controllers. For machine soft-mounted via flexible isolators, a model for this matrix has been derived. Under certain conditions, a simple multiplicative uncertainty model is obtained that shows the amount of perturbation a flexible base has on the machine-isolator-rigid base transmissibility matrix. Such a model is very suitable for use with robust control design paradigm. A different model is derived for the machine on hard-mounts without the flexible isolators. With this model, the level of force transmitted from a machine to a final mounting structure using the measurements for the machine running on another mounting structure can be determined. The two mounting structures have dissimilar dynamic characteristics. Experiments have verified the usefulness of the expression. The model compares well with other methods in the literature. The disadvantage lies with the large amount of data that has to be collected. Active force cancellation is demonstrated on an experimental rig using an AC industrial motor hard-mounted onto a relative flexible structure. The force transfer function matrix, determined from measurements, is used to design H and Static Output Feedback controllers. Both types of controllers are stable and robust to modelling errors within the identified frequency range. They reduce the RMS of transmitted force by between 30?80% at all mounting locations for machine running at 1340 rpm. At the rated speed of 1440 rpm only the static gain controller is able to provide 30?55% reduction at all locations. The H controllers on the other hand could only give a small reduction at one mount location. This is due in part to the deficient of the model used in the design. Higher frequency dynamics has been ignored in the model. This can be resolved by the use of a higher order model that can result in a high order controller. A low order static gain controller, with some tuning, performs better. But it lacks the analytical framework for analysis and design.
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Pelegrinis, Michail T. "Local active control of reflected sound." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/7362/.
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