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Fuzzy Control of Magnetic Bearing System Using Modified PDC Algorithm
Joh,Joongseon,Lee,Sangmin 창원대학교 공작기계기술연구센터 1999 연구업적집 Vol.1 No.1
A new fuzzy control algorithm for the control of active magnetic bearing (AMB) systems is proposed in this paper. It combines PDC design of Joh et al. [8], [9] and Mamdani-type control rules using fuzzy singletons to handle the nonlinear characteristics of AMB systems efficiently. They are named fine mode control and rough mode control, respectively. The rough mode control yields the fastest response for large deviation of the rotor and the fine mode control gives desired transient response for small deviation of the rotor. The proposed algorithm is applied a AMB system to verify the performance of the method. The comparison of the proposed method to a linear controller using a linearized model about the equilibrium point and PDC algorithm in [7] show the superiority of the proposed algorithm.
A New Design Method for T-S Fuzzy Controller with Pole Placement Constraints
Joh, Joongseon,Jeung, Eun-Tae,Chung, Won-Jee,Kwon, Sung-Ha Korean Institute of Intelligent Systems 1997 한국지능시스템학회논문지 Vol.7 No.3
A new design method for Takagi-Sugeno (T-S in short) fuzzy controller which guarantees global asymptotic stability and satisfies a desired performance is proposed in this paper. The method uses LMI(Linear Matrix Inequality) approach to find the common symmetric positive definite matrix P and feedback fains K/sub i/, i= 1, 2,..., r, numerically. The LMIs for stability criterion which treats P and K'/sub i/s as matrix variables is derived from Wang et al.'s stability criterion. Wang et al.'s stability criterion is nonlinear MIs since P and K'/sub i/s are coupled together. The desired performance is represented as $ LMIs which place the closed-loop poles of $ local subsystems within the desired region in s-plane. By solving the stability LMIs and pole placement constraint LMIs simultaneously, the feedback gains K'/sub i/s which gurarntee global asymptotic stability and satisfy the desired performance are determined. The design method is verified by designing a T-S fuzzy controller for an inverted pendulum with a cart using the proposed method.
On ths Stability Issues of Linear Takagi-Sugeno Fuzzy Models
Joh, Joongseon Korean Institute of Intelligent Systems 1997 한국지능시스템학회논문지 Vol.7 No.2
Stability issues of linear Takagi-Sugeno fuzzy modles are thoroughly investigated. At first, a systematic way of searching for a common symmetric positive definite P matrix (common P matrix in short), which is related to stability, is proposed for N subsystems which are under a pairwise commutativity assumption. Robustness issue under modeling uncertainty in each subsystem is then considered by proposing a quadratic stability criterion and a method of determining uncertainty bounds. Finally, it is shown that the pairwise commutative assumption can be in fact relaxed by interpreting the uncertainties as mismatch parts of non-commutative system matrices. Several examples show the validity of the proposed methods.
On the Fuzzy Control of Nonlinear Dynamic Systems with Inaccessible States
Joh,Joongseon,Kim,Kwangtae,Kwon,Woohyen 창원대학교 공작기계기술연구센터 1999 연구업적집 Vol.1 No.1
A systematic design method for PDC(Parallel Distributed Compensation)-type continuous time Takagi-Sugeno (T-S in short) fuzzy control systems which have inaccessible states is developed in this paper. Reduced-dimensional fuzzy state estimator is introduced from existing T-S fuzzy model using the PDC structure of wang et al [1]. LMI(Linear Matrix Inequalities) problems which represent the stability of the reduced-dimensional fuzzy state estimator are derived. Pole placement constraints idea for each rules is adopted to determine the estimator gains and they are also revealed as LMI problems These LMI problems are combined with joh et al's[7][8] LMI problems for PDC-type continuous time T-S fuzzy controller design to yield a systematic design method for PDC-type continuous time T-S fuzzy control systems which have inaccessible states.