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991.
Decoupling control can substantially simplify the design of multivariable control systems. However, decouplers are usually sensitive to modeling errors, especially for the systems with relative gains being far away from unity. Hence, decoupling control is limited in practical application. In the present study, robust control of a decoupling system with external loops is developed. Design of the control system consists of two steps. The first step is to design the decoupler and the controller based on the nominal plant. The second step is to design the filters in the external loops by using a robust stability criterion. The robust control is implemented without changing the original design of the decoupler and the controller. The control system with external loops for decoupling control significantly improves the control performance. The proposed robust control enhances the applicability of decoupling control. 相似文献
992.
DESIGNING PID CONTROLLERS WITH A MINIMUM IAE CRITERION BY A DIFFERENTIAL EVOLUTION ALGORITHM 总被引:5,自引:0,他引:5
Although the integral of absolute error (IAE) has long been used as a performance measure for controller evaluation, a systematic approach is still lacking for the design of optimal PID controller with the minimum IAE performance criterion. This may be ascribed to the nonsmoothness of the IAE objective function and the lack of closed-form expression for the IAE performance index. In this paper, we propose the use of a differential evolution algorithm (DEA) to design a minimum-IAE PID controller to overcome the nondifferentiability of the IAE objective function. To achieve also a specified least relative stability margin and least damping ratio, the D-partition technique is used to identify the allowable domain in the tuning parameter space. Three examples are provided to illustrate the effectiveness of the DEA. 相似文献
993.
Do-Hyung Kim Pyung Hwang Jang-Kyo Kim Man Lung Sham 《Metals and Materials International》1998,4(4):812-817
Hardness and elastic modulus of a typical leadframe material which consists of a Cu alloy substrate with Ni and Pd bi-layer
coatings were characterised using Vicker’s micro-hardness and nano-indentation tests. The two different testing methods produced
similar results in that ‘composite’ hardness for all coated specimens decreased (except at very low loads in the nano-indentation
test) with increasing indentation depth and tended to converge at sufficiently high loads due to the strong influence of the
coating/substrate interaction. The hardness values of substrate and Ni and Pd coatings were successfully determined from the
‘composite’ hardness values based on the empirical linear relationship with the inverse of indentation diagonal and the rule
of mixtures principle. 相似文献
994.
Yoon-Gil Paik Kyung-Ho Hwang Woo-Young Yoon Young-Hyun Paik Dong-Sik Kim 《Metals and Materials International》1998,4(5):987-994
For a super clean steel, the oxygen content should be restricted to a very low level, and controlled during the melt state.
The oxide behavior in an Al killed stainless steel melt were observed by analysing the forces exerted. New parameter, homogenization
number (H number), was introduced to generalize the forces. Quantitative analysis of the removal of oxides was conducted,
and a homogenization number was used to predict whether the oxides would be separated from the melt or mixed with the melt.
It was also shown that the H number could possibly be used to estimate the capacity of oxide-absorption at the top slag. 相似文献
995.
Dr Yean-Ren Hwang Cha-Shong Liang 《The International Journal of Advanced Manufacturing Technology》1998,14(6):399-405
Current computer-aided manufacturing (CAM) systems generate cutter contact points (CC points), cutter location points (CL points) and cutter orientation angles (CO angles) based only on the sculptured surface geometry. However, under certain situations, the cutting errors of 5-axis NC machines are larger than expected using these CC, CL and CO data. It is shown in this paper that the cutting error depends on the structures of 5-axis NC machines as well as the surface geometry. A new algorithm has been developed to estimate the cutting error and calculate the maximum allowable step length for spindle-tilting type 5-axis NC machines. Simulation results show that the new algorithm provides better estimation on the cutting errors for spindle-tilting type 5-axis NC machines. 相似文献
996.
Multiridge detection and time-frequency reconstruction 总被引:10,自引:0,他引:10
The ridges of the wavelet transform, the Gabor transform, or any time-frequency representation of a signal contain crucial information on the characteristics of the signal. Indeed, they mark the regions of the time-frequency plane where the signal concentrates most of its energy. We introduce a new algorithm to detect and identify these ridges. The procedure is based on an original form of Markov chain Monte Carlo algorithm especially adapted to the present situation. We show that this detection algorithm is especially useful for noisy signals with multiridge transforms. It is a common practice among practitioners to reconstruct a signal from the skeleton of a transform of the signal (i.e., the restriction of the transform to the ridges). After reviewing several known procedures, we introduce a new reconstruction algorithm, and we illustrate its efficiency on speech signals and its robustness and stability on chirps perturbed by synthetic noise at different SNRs 相似文献
997.
B. Y. Kang H. S. Ryoo W. Hwang S. K. Hwang S. W. Kim 《Materials Science and Engineering: A》1999,270(2):173
Synthesis of an intermetallic compound based on Ti5Si3 by an explosive compaction of elemental powders was studied with the detonation velocity as the main experimental variable. Prior to the explosion experiment, a computer simulation of the compaction process was conducted by using the DYNA program, and the result was utilized in designing the experiment. The relative density of the compacted compound increased with the detonation velocity. To enhance the density of the compound further, however, it was necessary to adjust other variables associated with the can, powder, and the backup tube. From an X-ray diffraction analysis of the explosion-compacted compound, it was confirmed that formation of the Ti5Si3 phase was complete. Although there is a room for further improvement of the density and the crack resistance of the compacted alloy, the present work verified that explosion synthesis is a potentially viable method to consolidate intermetallic compounds. 相似文献
998.
999.
Jin-Woo Ahn Seok-Gyu Oh Jae-Won Moon Young-Moon Hwang 《Industry Applications, IEEE Transactions on》1999,35(5):1067-1075
A new excitation strategy for a switched reluctance motor (SRM) is described and tested. This scheme excites two phases of an SRM simultaneously, which is similar to the two-phase excitation method of a step motor. In this scheme, the torque is produced by mutual-inductance as well as by self-inductance. The abrupt change of a phase excitation produces mechanical stresses, resulting in torque ripple and noise. The acoustic noise is reduced through a sequential two-phase excitation. Noise reduction occurs because the scheme reduces abrupt changes in excitation levels by distributed, balanced excitation and freewheeling during commutation. The operational principle and a characteristic comparison to that of the conventional SRM show that this novel excitation scheme has some advantages, including torque ripple and noise reduction, as well as simple inverter topology 相似文献
1000.
Summary
Two nonlinear optical (NLO) methacrylate monomers, 2-methyl-acrylic acid 2-(ethyl-{4-[2-(6-nitro-quinolin-2-yl)-vinyl]-phenyl}-amino)-ethyl
ester (5) and 2-methyl-acrylic acid 6-{3-[2-(6-nitro-quinolin-2-yl)-vinyl]-carbazol-9-yl}-hexyl ester (7) were newly synthesized and copolymerized with methylmethacrylate to give NLO polymers, P1 and P2. These polymers were well soluble in organic solvents and showed glass transition temperatures at 145 °C and 114 °C, respectively.
The number average molecular weights (Mn) were 26,600 for P1 and 9,300 for P2. The SHG coefficients (d33) of corona-poled films of P1 and P2 measured with 1.064 μm Nd-YAG laser were 32.2 pm/V and 17.6 pm/V, respectively.
Received: 29 September 1998/Revised version: 7 December 1998/Accepted: 11 December 1998 相似文献