Browsing by Author "Lin, PT"

Now showing 1 - 5 of 5

Support vector regression performance analysis and systematic parameter selection
(2005)
Lin, PT
;
Su, SF
;
Lee, TT
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Support Vector Regression (SVR) based on statistical learning is a useful tool for nonlinear regression problems. The SVR method deals with data in a high dimension space by using linear quadratic programming techniques. As a consequence, the regression result has optimal properties. However, if parameters were not properly selected, overfitting and/or underfitting phenomena might occur in SVR. Two parameters sigma, the width of Gaussian kernels and epsilon, the tolerance zone in the cost function are considered in this research. We adopted the concept of the sampling theory into Gaussian Filter to deal with parameter sigma. The idea is to analyze the frequency spectrum of training data and to select a cut-off frequency by including 90% of power in spectrum. The corresponding sigma can then be obtained through the sampling theory. In our simulations, it can be found that good performances are observed when the selected frequency is near the cut-off frequency. For another parameter epsilon, it is a tradeoff between the number of Support Vectors and the RMSE. By introducing the confidence interval concept, a suitable selection of epsilon can be obtained. The idea is to use the L-1-norm (i.e., when epsilon = 0) to estimate the noise distribution of training data. When E is obtained by selecting the 90%, confidence interval, simulations demonstrated superior performance in our illustrative example. By our systematical design, proper values of sigma and epsilon can be obtained and the resultant system performances are nice in all aspects.
Time-optimal control via fuzzy approach
(2004-01-01)
Lin, PT
;
Su, SF
;
Lee, TT
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, a fuzzy model based time-optimal controller will be proposed. The control input is bounded, and only achieved in minimum time. A design approach of the minimal time fuzzy controller using Pontryagin's Minimum Principle (PMP) is presented. The necessary conditions of PMP for time-optimal problem achieve the goal in minimum time under bounded controls can be formulated as bang-bang control. Determination of time-optimal solution by solving the corresponding two-point boundary-value problems (TPBVP) is, in general, done by shooting method. The TPBVP solved by the shooting method that allows to satisfy all the equations and the boundary conditions. An illustrative example is provided to show the validity of the proposed approach.
Time-optimal control via fuzzy approach
(2004-01-01)
Lin, PT
;
Su, SF
;
Lee, TT
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, a fuzzy model based time-optimal controller will be proposed. The control input is bounded, and only achieved in minimum time. A design approach of the minimal time fuzzy controller using Pontryagin's Minimum Principle (PMP) is presented. The necessary conditions of PMP for time-optimal problem achieve the goal in minimum time under bounded controls can be formulated as bang-bang control. Determination of time-optimal solution by solving the corresponding two-point boundary-value problems (TPBVP) is, in general, done by shooting method. The TPBVP solved by the shooting method that allows to satisfy all the equations and the boundary conditions. An illustrative example is provided to show the validity of the proposed approach.
Time-optimal fuzzy control based on computation method
(2005)
Lin, PT
;
Lee, TT
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, a fuzzy model based time-optimal controller will be proposed. The control input is bounded, and only achieved in minimum time. A design approach of the minimal time fuzzy controller using Pontryagin's Minimum Principle (PMP) is presented. The necessary conditions of PMP for time-optimal problem achieve the goal in minimum time under bounded controls can be formulated as bang-bang control. Determination of time-optimal solution by solving the corresponding two-point boundary-value problems (TPBVP) is, in general, a difficult problem. The proposed approach does not require to solve TPBVP. The Euler's method can be adopted to obtain approximate solution for T-S fuzzy model. Based on this method, the separating set of each subsystem in T-S fuzzy model is analytical and can cope with firing strength to generate switching conditions.
UV stability of high birefirngence liquid crystals
(2004)
Lin, PT
;
Wu, ST
;
Chang, CY
;
Hsu, CS
;
應用化學系
The ultraviolet stability of several high birefringence liquid crystal structures was studied. Compounds containing carbon-carbon double bond or triple bond are less stable than those containing merely phenyl rings. In addition to the structural effect, absorption wavelength also plays an important role to the degradation mechanisms.