1,095 research outputs found
CONTROL TECHNIQUES APPLIED TO INTEGRATED SHIP MOTION CONTROL
Fins stabilisers are devices which are fitted to the hull of a ship and utilised to ameliorate its
rolling motions. They apply a regulated moment about the ship's axis of roll in order to
oppose the sea induced disturbances. Recognising their unsurpassed performance, the Royal
Navy, since the 1950's, equips all its vessels with fin stabilisers. It can be shown that the
rudders, in vessels of appropriate size, also have the potential to be harnessed as roll
stabilisers Rudder Roll Stabilisation (RRS) without degrading the ship's course-keeping.
Thus creating a more stable platform for the human operators and equipment.
The reported success of RRS imparted an impetus to the Royal Navy to initiate this study.
The objectives are to ascertain whether RRS is possible without rudder modifications and to
establish whether enhanced levels of stabilisation would accrue if the fins and RRS were
operated in congress. The advantages in this novel approach being: avoidance of redesign
and refit of rudders, three modes of operation (fins alone, RRS alone and combined RRS
and fins), reduced fin activity and by implication self-generated noise, and amenability to be
retrofitted by simple alteration of any existing ship's autopilot software.
The study initially examined the mathematical models of the ship dynamics, defining
deficiencies and evaluating sources of uncertainty. It was postulated that the dual purpose
of the rudder can be separated into non-interacting frequency channels for controller design
purposes. An integrated design methodology is adopted to the roll stabilisation problem.
Investigating the capabilities of the rudder servomechanism, a new scheme, the
Anti-Saturation Algorithm (ASA) was proposed which can eliminate slew rate saturation.
Application of the ASA is generic to any servomechanism.
The effects of lateral accelerations of the ship on human operators was examined. This
resulted in an unique contribution to the Lateral Force Estimator problem in terms of
generating time domain models and defining the limitations of the applicability of a control
design strategy.
Linear Quadratic Guassian and two types of classical controllers were constructed for the
RRS and fins. A novel application of linear robust control theory to the ship roll
stabilisation problem resulted in H . controllers whose performance was superior to the
other design methods. This required the development of weight functions and the
identification and quantification of possible sources of uncertainty. The structured singular
value utilised this information to give comparable measures of robustness.
The sea trials conducted represent the first experience of the integrated ship roll stabilisation
approach. Experimental results are detailed. These afforded an invaluable opportunity to
validate the software employed to predict ship motion. The data generated from the sea
trials concurs with the simulations data in predicting that enhanced levels of roll stabilisation
are possible without any modification to the rudder system. They also confirm that when the
RRS is acting in congress with the fin stabilisers the activity of both actuators diminishes
Online identification of a two-mass system in frequency domain using a Kalman filter
Some of the most widely recognized online parameter estimation techniques used in different servomechanism are the extended Kalman filter (EKF) and recursive least squares (RLS) methods. Without loss of generality, these methods are based on a prior knowledge of the model structure of the system to be identified, and thus, they can be regarded as parametric identification methods. This paper proposes an on-line non-parametric frequency response identification routine that is based on a fixed-coefficient Kalman filter, which is configured to perform like a Fourier transform. The approach exploits the knowledge of the excitation signal by updating the Kalman filter gains with the known time-varying frequency of chirp signal. The experimental results demonstrate the effectiveness of the proposed online identification method to estimate a non-parametric model of the closed loop controlled servomechanism in a selected band of frequencies
Model Predictive Regulation
We show how optimal nonlinear regulation can be achieved in a model
predictive control fashion
Optimum PI/PID Controllers Tuning via an Evolutionary Algorithm
In this chapter, it is demonstrated that when using advanced evolutionary algorithms, whatever the adopted system model (SOSPD, nonminimum phase, oscillatory or nonlinear), it is possible to find optimal parameters for PID controllers satisfying simultaneously the behavior of the system and a performance index such as absolute integral error (IAE). The Multidynamics Algorithm for Global Optimization (MAGO) is used to solve the control problem with PID controllers. MAGO is an evolutionary algorithm without parameters, with statistical operators, and for the optimization, it does not need the derivatives, what makes it very effective for complex engineering problems. A selection of some representative benchmark systems is carried out, and the respectively two-degree-of-freedom (2DoF) PID controllers are tuned. A power electronic converter is adopted as a case study and based on its nonlinear dynamical model, a PI controller is tuned. In all cases, the control problem is formulated as a constrained optimization problem and solved using MAGO. The results found are outstanding
Disturbance Observer-based Robust Control and Its Applications: 35th Anniversary Overview
Disturbance Observer has been one of the most widely used robust control
tools since it was proposed in 1983. This paper introduces the origins of
Disturbance Observer and presents a survey of the major results on Disturbance
Observer-based robust control in the last thirty-five years. Furthermore, it
explains the analysis and synthesis techniques of Disturbance Observer-based
robust control for linear and nonlinear systems by using a unified framework.
In the last section, this paper presents concluding remarks on Disturbance
Observer-based robust control and its engineering applications.Comment: 12 pages, 4 figure
Optimal control of an internal combustion engine and transmission system
The control of an internal-combustion engine such that
it will produce its required output, with a minimum consumption
of fuel, even in the presence of random load disturbances,
has become a necessary requirement for future prime-mover
and vehicular applications. This thesis is concerned with
an attempt to produce a practical scheme to meet that requirement
from a study of several methods of achieving optimal
engine regulation and a method of obtaining optimal start-up.
An attempt was made first to identify the response of the
engine-transmission-load combination with a mathematical
model obtained by the use of computers. The servo-mechanism
associated with the throttle was identified also, and then
a complete state-variable description of the system was
obtained. Next an automatic gear-changing scheme was
designed and implemented. With the availability of this
practical system an optimal control function was generated
then to implement optimal start-up. The optimal function
was calculated by solving the associated multi-point boundary
value problem by means of technique of quasi-linearisation.
To subject the system to random loads an artificial road was
simulated, and a scheme was devised to vary the dynamometer
loading in response to this 'road' signal.
The remainder of the thesis is concerned with a study of
several different methods of obtaining optimal or sub-optimal schemes of regulation and with comparisons of experimental
results and the results from associated theoretical computer
studies.
Many suggestions for further investigations are contained
in the final chapter
Research in and application of modern automatic control theory to nuclear rocket dynamics and control, volume I Semiannual status report
Linear optimal feedback control theory for nuclear rocket dynamics and control problem
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