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RISS 인기검색어
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- 저자 : Nicholas Tham (검색결과 3 건)
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Mitigating Control Loop Interactions
Ming Tham,Nicholas Pooley,Amin Ganjian,Richard Jones 제어로봇시스템학회 2010 제어로봇시스템학회 국제학술대회 논문집 Vol.2010 No.10
This paper examines the feasibility of using disturbance observers (DOs) to compensate for interactions between control loops in non-linear multivariable systems. A distillation column application is considered. Traditionally, both steady-state and dynamic decouplers, designed using a linear model of the nonlinear system, are used to improve the multi-loop control of distillation columns. The multi-loop control strategy used here is proportional and integral (PI) feedback control on each loop with the controller parameters being derived from the linear model of the column. Steady-state and dynamic decoupling work well on linear systems but less so on nonlinear systems when there is a degree of mismatch between the linear model used to design the decouplers and the underlying non-linear system. Previous work on DOs has indicated their ability to compensate for system nonlinearities, implying that the use of DO’s for decoupling in nonlinear multivariable systems might provide an improvement over the traditional decoupling strategies. Control studies on the non-linear distillation column model indicate that the dynamic decoupler is extremely sensitive to model mismatch, leading to severe deterioration in performance when applied to the non-linear system. The steady-state decoupler was less sensitive to model mismatch and indeed, tends to be the approach used practically. DOs, on the other hand, alleviated the effects of loop interaction quite well even in the presence of modeling errors. This suggests that DOs will work well in a non-linear environment in the presence of model mismatch, perhaps providing much better robust performance than that displayed by the traditional decoupling approaches.
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Lasers in Additive Manufacturing: A Review
이협,김영진,Chin Huat Joel Lim,Mun Ji Low,Nicholas Tham,Vadakke Matham Murukeshan 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.4 No.3
In recent years, additive manufacturing, also known as three-dimensional (3D) printing, has emerged as an environmentally friendly green manufacturing technology which brings great benefits, such as energy saving, less material consumption, and efficient production. These advantages are attributed to the successive material deposition at designated target areas by delivering the energy on it. In this regard, lasers are the most effective energy source in additive manufacturing since the laser beam can transfer a large amount of energy into micro-scale focal region instantaneously to solidify or cure materials in air, therefore enabling high-precision and high-throughput manufacturing for a wide range of materials. In this paper, we introduce laser-based additive manufacturing methods and review the types of lasers widely used in 3D printing machines. Important laser parameters relevant to additive manufacturing will be analyzed and general guidelines for selecting suitable lasers for additive manufacturing will be provided. Discussion on future prospects of laser technologies for additive manufacturing will be finally covered.
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