Oh-Kyu Kwon

Optimal FIR filters for time-varying state-space models

An optimal FIR (finite impulse response) filter and smoother is introduced for the time-varying state-space model. The suggested filter has an FIR structure and utilizes finite observation. It is shown that the impulse response of the optimal FIR filter can be obtained by a simple Riccati-type matrix differential equation. Especially for time-invariant systems, this FIR filter reduces to previously known simple forms. For implementation, a recursive form of the optimal FIR filter and smoother is derived by using adjoint variables, and computational algorithms are suggested. It is also shown by sensitivity analysis that the proposed optimal FIR filter alleviates potential divergence characteristics of the standard Kalman filter. >

Fault Detection and Diagnosis in Gas Turbines

In this study, analytical redundancy methods have been applied to gas turbine engine transient data with the view to extracting the desired fault information. The basic idea is to use mathematical models to interrelate the measured variables and then monitor the effects of fault conditions on the new estimates of the model parameters. A new method of quantifying the effects of changes in the operating conditions is presented when simplified models are employed. The technique accounts for undermodeling effects and errors arising from linerization of an inherently nonlinear system

Compensation of networked control systems using LMI-based delay-dependent optimization method

Transmission delays in networked control systems are inevitable and can degrade the system performance or stability. The paper proposes a compensation method for networked control systems with network induced delay using a LMI-based delay-dependent optimization method. The delay-dependent optimization method has been adapted to provide an upper bound of the delay such that the system is asymptotically stable. Some simulations applied to numerical examples with networked control show that the proposed method works well.

Brief Estimation and detection of unknown inputs using optimal FIR filter

The optimal finite impulse response (FIR) filter is applied to systems with both unknown inputs and noise, in order to obtain noise-suppressed estimates of the unknown inputs. The unknown inputs are modeled as random-walk processes and estimated together with the state. Using the optimal FIR filtering algorithm, the estimate for each unknown input is shown to be independent of the window initial state and also of other unknown inputs. A detection scheme for an unknown input is developed utilizing a test variable independently of other unknown inputs. Finally, numerical examples are given to show the performance of the proposed estimation and detection method.

Fault-Tolerant Model Based Predictive Control with Application to Boiler Systems

Abstract This paper deals with the fault-tolerant control problem under nonlinear boiler systems with noise and disturbance. MCMBPC (Multivariable Constrained Model-Based Predictive Controller) proposed by Wilkinson et al . is used and modified in this paper in order to be applied to nonlinear boiler systems. Fault-tolerant control scheme combining MCMBPC with a fault detection method based on the unknown input observer is proposed. The fault-tolerant controller proposed is shown, via simulation, to have acceptable tracking performance even under some faults of input valves in the boiler system.

Twin Rotors System Modeling and Bumpless Transfer Implementation Algorithm for LQ Control

In this paper a twin rotors system is implemented, and a proper analytic nonlinear model is derived based on real data. Also, linear models are proposed at each operating point to design a linear controller. Next, a bumpless transfer algorithm is proposed for the LQ control of twin rotors system. Via some simulations we exemplify the performance of the proposed bumpless transfer algorithm and show usefulness through applying it to the real twin rotors system

Robust H/sub /spl infin// FIR filter for discrete-time uncertain systems

A robust H/sub /spl infin// filter with FIR (finite impulse response) structure is proposed for linear discrete time-varying uncertain systems represented by the state-space model having parameter uncertainty. Firstly, when there is no parameter uncertainty in the system, the discrete-time H/sub /spl infin// FIR filter is derived by using the equivalence relationship between the FIR filter and the recursive filter, which corresponds to the standard H/sub /spl infin// filter. Secondly, when the system has the parameter uncertainty, the robust H/sub /spl infin// FIR filter is proposed for the discrete-time linear uncertain system. It is also derived from the equivalence relationship between the robust H/sub /spl infin// FIR filter and the robust H/sub /spl infin// filter proposed by de Souza and Xie (1994) and Xie et al. (1991) for discrete-time systems. Estimation performance of the discrete-time H/sub /spl infin// FIR filters proposed is compared with two other techniques, Kalman filter and the robust H/sub /spl infin// filter, via some simulations to exemplify the performance superiority of the proposed method over other techniques.

Networked control systems design with time-varying delays

Abstract This paper has proposed a controller design method for networked control systems with network induced delays by using LMI-based delay-dependent optimization. The delays are described by a Markov chain, since they are to be time-varying and even longer than the sampling time. A delay-dependent compensation method has been proposed here with a jump linear system analysis technique to stabilize the networked control system. To exemplify the performance of the proposed method, some simulations applied to numerical examples with the networked control are performed.

Robust H∞ Fir Filter for Uncertain Systems

Abstract This paper deals with the issue of the robust H ∞ FIR (Fmite Impulse Response) filtering problem for linear systems with parameter uncertainty in the state-space model. Firstly, the H ∞ FIR filter is presented for the system without the uncertainty, which corresponds to the H ∞ filter proposed by Nagpal and Khargonekar (1991). The impulse response of the H ∞ FIR filter is calculated by the equivalence relationship between the FIR filter and the recursive filter (Kwon et al., 1990; 1994). Secondly, the robust H ∞ FIR is proposed for the linear uncertain system with the parameter uncertainty. It is also derived from the relationship between the robust Hqq FIR filter and the robust Hoo filter proposed by Xie and de Souza (1991) and Fu et al. (1992). Estimation performances of the H ∞ FIR filters proposed are compared with two other techniques by Kalman filter and the robust H ∞ filter (Shaked and Theodor, 1992; Fu et at., 1992) via some simulations to exemplify the superiority of the proposed method over other techniques.

Development of a Rapid Control Prototyping System Based on Matlab and USB DAQ boards

In this paper, we propose a new and cost-effective RCP (Rapid Control Prototyping) system based on Matlab/Simulink and a DAQ (Data Acquisition) unit with the high speed USB communication interface. The proposed RCP system has a feature that a computer on which Simulink is running acts as a realtime controller and a DAQ unit performs data acquisition, transmission of the data to and from a computer, and the application of control data received from the computer. For its implementation, we develop 10 communication blocks each of which is constructed by using S-function. In order to increase the data communication speed and thus to reduce the sampling period of the overall control system, we propose to use a batch transfer strategy through the USB interface. The proposed RCP system has several advantages over existing methods such as good maintainability, portability due to the USB interface, low cost, and no necessity for C-code generation even though it can only be applied to control systems with moderate sampling rates. It is expected that the proposed RCP system can be useful in teaching control-related topics to undergraduate and graduate students.