Nonlinear Controller (nonlinear + controller)

Distribution by Scientific Domains


Selected Abstracts


Fault-tolerant control of nonlinear processes: performance-based reconfiguration and robustness

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 3 2006
Prashant Mhaskar
Abstract This work considers the problem of control system/actuator failures in nonlinear processes subject to input constraints and presents two approaches for fault-tolerant control that focus on incorporating performance and robustness considerations, respectively. In both approaches, first a family of candidate control configurations, characterized by different manipulated inputs, is identified for the process under consideration. Performance considerations are first incorporated via the design of a Lyapunov-based predictive controller that enforces closed-loop stability from an explicitly characterized set of initial conditions (computed using an auxiliary Lyapunov-based nonlinear controller). A hierarchical switching policy is derived, that uses stability considerations (evaluated via the presence of the state in the stability region of a control configuration) to ascertain the suitability of a candidate backup configuration and then performance considerations are again considered in choosing between the suitable backup configurations. Next, we consider the problem of implementing fault-tolerant control to nonlinear processes subject to input constraints and uncertainty. To this end, we first design a robust hybrid predictive controller for each candidate control configuration that guarantees stability from an explicitly characterized set of initial conditions, subject to uncertainty and constraints. A switching policy is then derived to orchestrate the activation/deactivation of the constituent control configurations. Finally, simulation studies are presented to demonstrate the implementation and evaluate the effectiveness of the proposed fault-tolerant control method. Copyright © 2005 John Wiley & Sons, Ltd. [source]


Modelling, identification, and control of a spherical particle trapped in an optical tweezer

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 16 2005
A. Ranaweera
Abstract We provide an introduction to modelling, identification, and control of a spherical particle trapped in an optical tweezer. The main purpose is to analyse the properties of an optical tweezer from a control systems point of view. By representing the non-inertial dynamics of a trapped particle using a stochastic differential equation, we discuss probability distributions and compute first mean exit times. Within the linear trapping region, experimentally measured mean passage times for a 9.6-µm diameter polystyrene bead show close agreement with theoretical calculations. We apply a recursive least squares method to a trapped 9.6-µm diameter polystyrene bead to study the possibility of obtaining faster calibrations of characteristic frequency. We also compare the performance of proportional control, LQG control, and nonlinear control to reduce fluctuations in particle position due to thermal noise. Assuming a cubic trapping force, we use computer simulations to demonstrate that the nonlinear controller can reduce position variance by a factor of 65 for a 1-µm diameter polystyrene bead under typical conditions. Copyright © 2005 John Wiley & Sons, Ltd. [source]


Robust nonlinear ship course-keeping control by H, I/O linearization and , -synthesis

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 1 2003
Shr-Shiung Hu
Abstract In this paper, the H, input/output (I/O) linearization formulation is applied to design an inner-loop nonlinear controller for a nonlinear ship course-keeping control problem. Due to the ship motion dynamics are non-minimum phase, it is impossible to use the ordinary feedback I/O linearization to resolve. Hence, the technique of H, I/O linearization is proposed to obtain a nonlinear H, controller such that the compensated nonlinear system approximates the linear reference model in I/O behaviour. Then a , -synthesis method is employed to design an outer-loop robust controller to address tracking, regulation, and robustness issues. The time responses of the tracking signals for the closed-loop system reveal that the overall robust nonlinear controller is able to provide robust stability and robust performance for the plant uncertainties and state measurement errors. Copyright © 2002 John Wiley & Sons, Ltd. [source]


Nonlinear Controller Design for PWM,Controlled Converters

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003
A. Kugi Prof. Dr. techn.
This contribution is concerned with the nonlinear controller design for a certain class of PWM (pulse width modulation) , controlled converter systems. It will be shown that under certain assumptions the SSA (state space averaging) , model of the PWM,controlled converter with the duty ratio as the plant input has a very special mathematical structure. Based on this mathematical model a modified version of the nonlinear H2,design where an integral term is systematically included in the nonlinear controller will be presented. [source]


Optimal grade transition control for liquid-propylene polymerization reactor,

ASIAN JOURNAL OF CONTROL, Issue 3 2010
Mohammad Al-haj Ali
Abstract A nonlinear control system integrating an off-line optimizer and a nonlinear model-based controller is developed to perform optimal grade transition operations in a continuous pilot plant reactor. A simple black-box model is developed and used to determine optimal trajectories of inputs and outputs for a series of three polypropylene grades. The simplified model is also used to develop a nonlinear controller. This controller is similar to generic model control; however, the integral action is omitted and an on-line updating scheme is incorporated to update pre-specified model parameters using delayed process measurements. The time optimal inputs, which are calculated by the off-line optimizer, are introduced to the plant in a feedforward manner. At the same time, the deviations from the optimal output are corrected using the feedback nonlinear controller. The simulations on a complex mechanistic model of the process reveal that the nonlinear control scheme performs well for both set point tracking and disturbance rejection. This paper integrates well-known methodologies, such as the generic-model control algorithm, parameter update schemes, and off-line optimization, together to develop an applicable and robust control technique for continuous polymerization reactors. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source]


Stabilization of the inverted spherical pendulum via Lyapunov approach,

ASIAN JOURNAL OF CONTROL, Issue 6 2009
O. Octavio Gutiérrez F.
Abstract In this paper a nonlinear controller is presented for the stabilization of the spherical inverted pendulum system. The control strategy is based on the Lyapunov approach in conjunction with LaSalle's invariance principle. The proposed controller is able to bring the pendulum to the unstable upright equilibrium point with the position of the movable base at the origin. The obtained closed-loop system has a very large domain of attraction, that can be as large as desired, for any initial position of the pendulum which lies above the horizontal plane. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source]


INPUT-STATE LINEARIZATION OF A ROTARY INVERTED PENDULUM

ASIAN JOURNAL OF CONTROL, Issue 1 2004
Chih-Keng Chen
ABSTRACT The aim of this paper is to design a nonlinear controller for the rotary inverted pendulum system using the input-state linearization method. The system is linearized, and the conditions necessary for the system to be linearizable are discussed. The range of the equilibriums of the system is also investigated. Further, after the system is linearized, the linear servo controllers are designed based on the pole-placement scheme to control the output tracking problem. The performance of the controller is studied with different system parameters. The computer simulations demonstrate that the controller can effectively track the reference inputs. [source]