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Suboptimal reliable guaranteed cost control for continuous-time systems with multi-criterion constraints
Deng-feng ZHANG, Hong-ye SU, Jian CHU, Zhi-quan WANG
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(8): 1024-1033.
https://doi.org/10.1631/jzus.A0720031
The suboptimal reliable guaranteed cost control (RGCC) with multi-criterion constraints is investigated for a class of uncertain continuous-time systems with sensor faults. A fault model in sensors, which considers outage or partial degradation of sensors, is adopted. The influence of the disturbance on the quadratic stability of the closed-loop systems is analyzed. The reliable state-feedback controller is developed by a linear matrix inequalities (LMIs) approach, to minimize the upper bound of a quadratic cost function under the conditions that all the closed-loop poles be placed in a specified disk, and that the prescribed level of H∞ disturbance attenuation and the upper bound constraints of control inputs’ magnitudes be guaranteed. Thus, with the above multi-criterion constraints, the resulting closed-loop system can provide satisfactory stability, transient property, a disturbance rejection level and minimized quadratic cost performance despite possible sensor faults.
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A closed-loop particle swarm optimizer for multivariable process controller design
Kai HAN, Jun ZHAO, Zu-hua XU, Ji-xin QIAN
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(8): 1050-1060.
https://doi.org/10.1631/jzus.A0720081
Design of general multivariable process controllers is an attractive and practical alternative to optimizing design by evolutionary algorithms (EAs) since it can be formulated as an optimization problem. A closed-loop particle swarm optimization (CLPSO) algorithm is proposed by mapping PSO elements into the closed-loop system based on control theories. At each time step, a proportional integral (PI) controller is used to calculate an updated inertia weight for each particle in swarms from its last fitness. With this modification, limitations caused by a uniform inertia weight for the whole population are avoided, and the particles have enough diversity. After the effectiveness, efficiency and robustness are tested by benchmark functions, CLPSO is applied to design a multivariable proportional-integral-derivative (PID) controller for a solvent dehydration tower in a chemical plant and has improved its performances.
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A spatially triggered dissipative resource distribution policy for SMT processors
Hong-zhou CHEN, Xue-zeng PAN, Ling-di PING, Kui-jun LU, Xiao-ping CHEN
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(8): 1070-1082.
https://doi.org/10.1631/jzus.A0720083
Programs take on changing behavior at runtime in a simultaneous multithreading (SMT) environment. How reasonably common resources are distributed among the threads significantly determines the throughput and fairness performance in SMT processors. Existing resource distribution methods either mainly rely on the front-end fetch policy, or make distribution decisions according to the limited information from the pipeline. It is difficult for them to efficiently catch the various resource requirements of the threads. This work presents a spatially triggered dissipative resource distribution (SDRD) policy for SMT processors. Its two parts, the self-organization mechanism that is driven by the real-time instructions per cycle (IPC) performance and the introduction of chaos that tries to control the diversity of trial resource distributions, work together to supply sustaining resource distribution optimization for changing program behavior. Simulation results show that SDRD with fine-grained diversity controlling is more effective than that with a coarse-grained one. And SDRD benefits much from its two well-coordinated parts, providing potential fairness gains as well as good throughput gains. Meanings and settings of important SDRD parameters are also discussed.
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Applying sub-band energy extraction to noise cancellation of ultrasonic NDT signal
Qi ZHANG, Pei-wen QUE, Wei LIANG
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(8): 1134-1140.
https://doi.org/10.1631/jzus.A0720072
In ultrasonic non-destructive tests, the echo signal at the flaw is highly complex due to the interference of multiple echoes with random amplitudes and phases, and is disturbed by all kinds of noises, such as thermal noise, digitalization noise, and structure noise. In this paper, the ultrasonic signal was decomposed by empirical mode decomposition (EMD) to obtain the intrinsic mode function (IMF) components according to ultrasonic defect echo signals occuring at the corresponding time, and the energy of the ultrasonic signal was concentrated. The IMF component selection criterion based on sub-band energy extraction was proposed to extract the ultrasonic signal component accurately and automatically from IMF components. When the selected IMF components were filtered by a band pass filter, the signal-to-noise ratio (SNR) was enhanced greatly.
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A novel current-sharing scheme based on magamp
Wen-xi YAO, Xiao-yuan HONG, Zheng-yu LU
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(8): 1150-1156.
https://doi.org/10.1631/jzus.A0720112
The magamp (magnetic amplifier) is widely used in power supplies due to its low cost, simplicity and other advantages. This paper discusses a novel application of the magamp in switching power supplies, where the magamp is used to regulate pulse width modulation (PWM) instead of power signal in the main circuit. This method extends the application of the magamp in power supplies, and makes it possible to further regulate control signal when PWMs have been generated. Based on this application, a new current-sharing (CS) scheme using the magamp is proposed, which uses a modified inner loop CS structure. In this scheme PWMs are generated by one main controller, and CS is achieved by regulating PWMs using a magamp in each module. Compared with traditional application of the magamp, the new CS scheme can be used in most topologies and only requires magamps of low power capacity. Then a test circuit of parallel power supply is developed, in which CS is achieved by a PWM regulator with the magamp. The proposed scheme is also used to upgrade an electroplate power to make it capable of paralleling supplies. Experimental results show that the proposed scheme has good CS performance.
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16 articles
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