In the head positioning control of hard disk drives, a digital control is widely used. Therefore, if a small sampling period could be used, the performance obtained by the digital controller is not so deteriorated com...
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In the head positioning control of hard disk drives, a digital control is widely used. Therefore, if a small sampling period could be used, the performance obtained by the digital controller is not so deteriorated compared with the one obtained by the analog controller. However, in hard disk systems, the sampling period cannot be chosen arbitrary. Because it is determined by the other factor which is nothing to do with control requirements in almost cases. In this paper, we apply the sampled-data H∞ control synthesis to the head positioning control of the hard disk drive. This method enable us to design a desirable digital controller directly by taking into account of intersampling behaviors. Experimental results show that good following performances can be achieved by the long sampling period.
We propose here an adaptive observer for estimation of a road friction coefficient, which is important for vehicle control. The observer needs driving torque and wheel speeds of driven and non-driven wheels as inputs....
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We propose here an adaptive observer for estimation of a road friction coefficient, which is important for vehicle control. The observer needs driving torque and wheel speeds of driven and non-driven wheels as inputs. The road friction coefficient is assumed to be represented by a product of a known function and an unknown parameter to be estimated by an adaptive law. It is shown that non-robust adaptive law can get the true value, if there are no disturbance. However, it diverges when disturbances are added. Periodical σ-modification is proposed here as a robust adaptive law. The estimation robustness against disturbances can be improved with the law. Numerical simulation results are presented to show the effectiveness of the law.
We study the spatiotemporal dynamics of flow separation in a planar diffuser to extract reduced-order models that may be used to guide active separation control. Proper orthogonal decomposition of numerical simulation...
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We study the spatiotemporal dynamics of flow separation in a planar diffuser to extract reduced-order models that may be used to guide active separation control. Proper orthogonal decomposition of numerical simulation data revealed organized dynamics of the large-scale separated structures. This result, combined with the observation (in simulations as well as laboratory experiments) of limit cycle/quasiperiodic dynamics and spatial symmetry breaking, suggests an underlying low-dimensional dynamical system. Galerkin-based and neural network-based modeling of the POD modal coefficients lead to (parameter dependent) low-dimensional models of separation dynamics. The use of such models for active separation control appears promising.
Reactive distillation integrates reaction and separation into one apparatus and offers the possibility to overcome restrictions given by chemical and phase equilibria. The batch and semibatch modes permit a more flexi...
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Reactive distillation integrates reaction and separation into one apparatus and offers the possibility to overcome restrictions given by chemical and phase equilibria. The batch and semibatch modes permit a more flexible operation compared to the continuous case especially for multi product plants. Here the heterogeneously catalyzed esterification of methanol and acetic acid in a reactive distillation column which is operated in semibatch mode is investigated. The solution of a minimum batch time problem defines the optimal trajectory of the process. The task of feedback control is to track this trajectory in the presence of disturbances and model uncertainties. Due to the nonlinear plant behaviour, robustness properties have to be taken into consideration in the design. The nonlinearity of the system is considered as an uncertainty of the linear nominal model in the optimal operating region. A robust controller is designed using a combination of a loop shaping procedure and frequency response approximation. The linear closed-loop system is stable for the nominal model as well as for the models containing uncertainties. The controller also shows good tracking performance when used with the nonlinear model.
The design of suspension is very important for ride-comfort on automobiles. A lot of active and semi-active suspensions have been studied. In recent years, the car with active or semi-active suspension has been put in...
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The design of suspension is very important for ride-comfort on automobiles. A lot of active and semi-active suspensions have been studied. In recent years, the car with active or semi-active suspension has been put into practice. Since the active suspension needs large power and space, a semi-active suspension have recently received attention. In this study, the bilinear disturbance accommodating control theory is established and it is applied to the semi-active control of suspension for automobiles. In this study, a 1/2 body model with 4-DOF is used. By applying the proposed bilinear disturbance accommodating optimal control to the semi-active suspension, its performance is investigated in the simulation. As a result, it showed better performance than the passive control with respect to the vertical acceleration and the pitch angular acceleration of ear body which give influence on ride-comfort for automobiles.
The state-dependent Riccati equation (SDRE) method is used to control the nonlinear nonminimum-phase dynamics of a continuously stirred tank reactor (CSTR). The benefits of using the SDRE method are that it can be dir...
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The state-dependent Riccati equation (SDRE) method is used to control the nonlinear nonminimum-phase dynamics of a continuously stirred tank reactor (CSTR). The benefits of using the SDRE method are that it can be directly applied to the nonminimum-phase system and hard bounds can be imposed on the control activity. From simulation analysis, it is determined that a complicated state-dependent state weighting matrix Q(x) would be required in order to produce satisfactory responses to changes in the set point of the reactor. To avoid the problem of finding such a state weighting matrix, an asymmetric solution of the SDRE is used instead of the symmetric positive-definite solution. Since there are an infinite number of asymmetric solutions, the paper discusses the process that was used in obtaining the selected asymmetric solution. Simulations are performed which produce a level of confidence that the closed loop system is asymptotically stable and is robust to parameter variations in the chemical concentration level in the educt flow.
The concept of Plug & Play has become increasingly popular in consumer electronics because of the ease of use and low maintenance, it now appears possible to apply this concept to the motor drive design. New gener...
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The concept of Plug & Play has become increasingly popular in consumer electronics because of the ease of use and low maintenance, it now appears possible to apply this concept to the motor drive design. New generations of DSP controllers, such as the Texas Instruments TMS320C240 ('C240) DSP controller, by integrating the high performance of a DSP core and the powerful on-chip peripherals of a microcontroller into a single-chip solution, have made this possible. This paper describes the practical implementation of a linear induction motor drive, which consists of power module and a single DSP controller, which will both reduce the cost and the complexity of the design. In order to save space and enable continuous operation, a linear induction motor has been specifically built for this study. Experimental results will be presented by a videotape in the conference.
This paper addresses the potential for energy reduction obtained by using dynamic line tensioning in thruster assisted position mooring systems. Traditionally, mooring systems have been designed in such a way that thr...
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This paper addresses the potential for energy reduction obtained by using dynamic line tensioning in thruster assisted position mooring systems. Traditionally, mooring systems have been designed in such a way that thruster assistance has hot been necessary under normal environmental conditions. However, as oil production moves into deeper waters, such over-dimensioned mooring systems are no longer feasible. Thus, new `hybrid' solutions must be developed, in which increased thruster action compensates for fewer, and lighter, anchor lines. In this paper, controlling the line tensions dynamically is suggested as an additional means of station keeping, and a control law is derived based on passivity. A model consisting of a rigid-body submodel for the vessel, and a finite element submodel for the mooring system is presented and used for simulations. The simulations show the performance of the proposed controlsystem.
In this paper a nonlinear controller is designed for a 6dof model of an unmanned underwater vehicle (UUV) which includes both the kinematics and the dynamics. It is shown how the use of a Lyapunov function consisting ...
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In this paper a nonlinear controller is designed for a 6dof model of an unmanned underwater vehicle (UUV) which includes both the kinematics and the dynamics. It is shown how the use of a Lyapunov function consisting of a quadratic term in the velocity (both linear and angular), a quadratic term in the position and a logarithmic term in the attitude leads to a design of a control law that achieves global asymptotic stabilization to an arbitrary set point in position/attitude. The control law is made linearly bounded by avoiding cancellation of some of the quadratic nonlinearities in the model. No information about the inertia matrix, the damping, and the Coriolis/centripetal parameters is used in the controller, endowing it with a certain amount of parametric robustness. The control law is given in terms of the Modified Rodrigues parameters. An extensive simulation study shows that the proposed control law achieves excellent tracking for slowly changing trajectories, even though it is designed only for set point regulation. The nonlinear controller dramatically outperforms a linear controller.
In this note, we propose a simple and useful decentralized approach for the states and parameters estimation of general non-linear discrete-time Multi-Input/Multi-Output (MIMO) systems. Thanks to a simple and useful p...
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In this note, we propose a simple and useful decentralized approach for the states and parameters estimation of general non-linear discrete-time Multi-Input/Multi-Output (MIMO) systems. Thanks to a simple and useful parametrization technique recently developed in [Bou97], we investigate the stability analysis and it turns out that not only asymptotic convergence is assured under very general conditions but also how to enlarge the basin of attraction with high tracking ability. Performances and accuracy of the results are illustrated, first, through a simulation example under severe conditions. Next, the proposed technique will be successfully applied to a real single-link rigid manipulator using only the position measurement.
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