1,504 research outputs found
Observation and control of PDE with disturbances
In this Thesis, the problem of controlling and Observing some classes of distributed parameter systems is addressed. The particularity of this work is to consider partial differential equations (PDE) under the effect of external unknown disturbances. We consider generalized forms of two popular parabolic and hyperbolic infinite dimensional dynamics, the heat and wave equations. Sliding-mode control is used to achieve the control goals, exploiting the robustness properties of this robust control technique against persistent disturbances and parameter uncertainties
Control strategies of series active variable geometry suspension for cars
This thesis develops control strategies of a new type of active suspension for high
performance cars, through vehicle modelling, controller design and application, and
simulation validation. The basic disciplines related to automotive suspensions are first
reviewed and are followed by a brief explanation of the new Series Active Variable
Geometry Suspension (SAVGS) concept which has been proposed prior to the work
in this thesis. As part of the control synthesis, recent studies in suspension control
approaches are intensively reviewed to identify the most suitable control approach for
the single-link variant of the SAVGS.
The modelling process of the high-fidelity multi-body quarter- and full- vehicle
models, and the modelling of the linearised models used throughout this project are
given in detail. The design of the controllers uses the linearised models, while the
performance of the closed loop system is investigated by implementing the controllers
to the nonlinear models.
The main body of this thesis elaborates on the process of synthesising Hâ control
schemes for quarter-car to full-car control. Starting by using the quarter-car single-link
variant of the SAVGS, an Hâ -controlled scheme is successfully constructed, which
provides optimal road disturbance and external force rejection to improve comfort
and road holding in the context of high frequency dynamics. This control technique is
then extended to the more complex full-car SAVGS and its control by considering the
pitching and rolling motions in the context of high frequency dynamics as additional
objectives. To improve the level of robustness to single-link rotations and remove the
geometry nonlinearity away from the equilibrium position, an updated approach of
the full-car SAVGS Hâ -controlled scheme is then developed based on a new linear
equivalent hand-derived full-car model. Finally, an overall SAVGS control framework
is developed, which operates by blending together the updated Hâ controller and
an attitude controller, to tackle the comfort and road holding in the high frequency
vehicle dynamics and chassis attitude motions in the low frequency vehicle dynamics
simultaneously. In all cases, cascade inner position controllers developed prior to the work in this
thesis are employed at each corner of the vehicle and combined with the control systems
developed in this thesis, to ensure that none of the physical or design limitations of
the actuator are violated under any circumstances.Open Acces
Observation and control of PDE with disturbances
In this Thesis, the problem of controlling and Observing some classes of distributed parameter systems is addressed. The particularity of this work is to consider partial differential equations (PDE) under the effect of external unknown disturbances. We consider generalized forms of two popular parabolic and hyperbolic infinite dimensional dynamics, the heat and wave equations. Sliding-mode control is used to achieve the control goals, exploiting the robustness properties of this robust control technique against persistent disturbances and parameter uncertainties
Model Based Teleoperation to Eliminate Feedback Delay NSF Grant BCS89-01352 First Report
We are conducting research in the area of teleoperation with feedback delay. Delay occurs with earth-based teleoperation in space and with surface-based teleoperation with untethered submersibles when acoustic communication links are involved. the delay in obtaining position and force feedback from remote slave arms makes teleoperation extremely difficult. We are proposing a novel combination of graphics and manipulator programming to solve the problem by interfacing a teleoperator master arm to a graphics based simulator of the remote environment coupled with a robot manipulator at the remote, delayed site. the operator\u27s actions will be monitored to provide both kinesthetic and visual feedback and to generate symbolic motion commands to the remote slave. the slave robot will then execute these symbolic commands delayed in time. While much of a task will proceed error free, when an error does occur the slave system will transmit data back to the master and the master environment will be reset to the error state
Teleprogramming: Overcoming Communication Delays in Remote Manipulation (Dissertation Proposal)
Modern industrial processes (nuclear, chemical industry), public service needs (firefighting, rescuing), and research interests (undersea, outer space exploration) have established a clear need to perform work remotely. Whereas a purely autonomous manipulative capability would solve the problem, its realization is beyond the state of the art in robotics [Stark et al.,1988]. Some of the problems plaguing the development of autonomous systems are: a) anticipation, detection, and correction of the multitude of possible error conditions arising during task execution, b) development of general strategy planning techniques transcending any particular limited task domain, c) providing the robot system with real-time adaptive behavior to accommodate changes in the remote environment, d) allowing for on-line learning and performance improvement through experience , etc. The classical approach to tackle some of these problems has been to introduce problem solvers and expert systems as part of the remote robot workcell control system. However, such systems tend to be limited in scope (to remain intellectually and implementationally manageable), too slow to be useful in real-time robot task execution, and generally fail to adequately represent and model the complexities of the real world environment. These problems become particularly severe when only partial information about the remote environment is available
The PRIMA fringe sensor unit
The Fringe Sensor Unit (FSU) is the central element of the Phase Referenced
Imaging and Micro-arcsecond Astrometry (PRIMA) dual-feed facility and provides
fringe sensing for all observation modes, comprising off-axis fringe tracking,
phase referenced imaging, and high-accuracy narrow-angle astrometry. It is
installed at the Very Large Telescope Interferometer (VLTI) and successfully
servoed the fringe tracking loop during the initial commissioning phase. Unique
among interferometric beam combiners, the FSU uses spatial phase modulation in
bulk optics to retrieve real-time estimates of fringe phase after spatial
filtering. A R=20 spectrometer across the K-band makes the retrieval of the
group delay signal possible. The FSU was integrated and aligned at the VLTI in
summer 2008. It yields phase and group delay measurements at sampling rates up
to 2 kHz, which are used to drive the fringe tracking control loop. During the
first commissioning runs, the FSU was used to track the fringes of stars with
K-band magnitudes as faint as m_K=9.0, using two VLTI Auxiliary Telescopes (AT)
and baselines of up to 96 m. Fringe tracking using two Very Large Telescope
(VLT) Unit Telescopes (UT) was demonstrated. During initial commissioning and
combining stellar light with two ATs, the FSU showed its ability to improve the
VLTI sensitivity in K-band by more than one magnitude towards fainter objects,
which is of fundamental importance to achieve the scientific objectives of
PRIMA.Comment: 19 pages, 23 figures. minor changes and language editing. this
version equals the published articl
Fault tolerant control for nonlinear aircraft based on feedback linearization
The thesis concerns the fault tolerant flight control (FTFC) problem for nonlinear aircraft by making use of analytical redundancy. Considering initially fault-free flight, the feedback linearization theory plays an important role to provide a baseline control approach for de-coupling and stabilizing a non-linear statically unstable aircraft system. Then several reconfigurable control strategies are studied to provide further robust control performance:- A neural network (NN)-based adaption mechanism is used to develop reconfigurable FTFC performance through the combination of a concurrent updated learninglaw. - The combined feedback linearization and NN adaptor FTFC system is further improved through the use of a sliding mode control (SMC) strategy to enhance the convergence of the NN learning adaptor. - An approach to simultaneous estimation of both state and fault signals is incorporated within an active FTFC system.The faults acting independently on the three primary actuators of the nonlinear aircraft are compensated in the control system.The theoretical ideas developed in the thesis have been applied to the nonlinear Machan Unmanned Aerial Vehicle (UAV) system. The simulation results obtained from a tracking control system demonstrate the improved fault tolerant performance for all the presented control schemes, validated under various faults and disturbance scenarios.A Boeing 747 nonlinear benchmark model, developed within the framework of the GARTEUR FM-AG 16 project âfault tolerant flight control systemsâ,is used for the purpose of further simulation study and testing of the FTFC scheme developed by making the combined use of concurrent learning NN and SMC theory. The simulation results under the given fault scenario show a promising reconfiguration performance
- âŠ