Dr. Xiaoyun Wang Profile

Dr. Xiaoyun Wang

at Canadian Space Agency

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Proceedings Article | 19 March 2008 Paper

Thermo-mechanical analysis of thin membranes and application in active flatness control design

Xiaoyun Wang, Christian Sulik, Wanping Zheng, Yan-Ru Hu

Proceedings Volume 6930, 69300H (2008) https://doi.org/10.1117/12.772004

KEYWORDS: Thermal effects, Solar radiation models, Thermal modeling, Actuators, Temperature metrology, Control systems design, Finite element methods, Antennas, Shape memory alloys, Ultraviolet radiation

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Membrane structures are excellent candidates for many lightweight large space structures, which can be utilized to improve the performance and to reduce the cost of space exploration and earth observation missions. In-orbit thermal disturbance is the main cause of membrane wrinkling, which deteriorates membrane surface accuracy. In order to maintain surface accuracy in the time-varying environment, active flatness control is regarded as a very important technology. In order to properly design active flatness control system, understanding of the thermo-mechanical coupling and the effects of tensioning forces in reducing membrane wrinkling is required. Based on the von-Karman nonlinear plate theory, a theoretical framework is developed in this paper. An FE model for a square membrane is developed as an example for case studies. Using thin shell elements, this model is capable of predicting the amplitude of out-of-plane displacements. Using this model, the effect of thermal disturbance is studied, which qualitatively agrees with experimental observations. By varying corner loads in the numerical model, it is demonstrated that corner loads can efficiently reduce surface deviation caused by a center-located heat source. In order to study the effect of thermal disturbance locations, different temperature distributions are applied to the membrane. With these temperature distributions, different tension forces combinations are evaluated in terms of improving surface accuracy.

Proceedings Article | 5 April 2007 Paper

Active flatness control of membrane structures using adaptive genetic algorithm

Xiaoyun Wang, Wanping Zheng, Yan-Ru Hu

Proceedings Volume 6527, 652704 (2007) https://doi.org/10.1117/12.716039

KEYWORDS: Genetic algorithms, Shape memory alloys, Control systems, Actuators, Cameras, Process control, Antennas, Computer simulations, Numerical simulations, Synthetic aperture radar

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Membrane structures are attracting attention as excellent candidates for lightweight large space structures, which can be utilized to improve the performance and reduce the cost of space exploration and earth observation missions. Membrane structures can be stowed to a small volume during launch and function as large structures after deployed. For many applications, maintaining surface accuracy of membranes is extremely important to achieve satisfactory performance, especially for membrane antennas and adaptive optics. Active flatness control is a vital technology to maintain surface accuracy of membrane structures. In this research, multiple shape memory alloy (SMA) actuators around the boundary of a rectangular membrane are used to apply tension forces to membrane structures to compensate wrinkle effects. The dynamics of membrane structures is nonlinear and computationally expensive, hence unfeasible to be used in real-time active flatness control. As a parallel direct searching method, genetic algorithm (GA) is used search optimal tension force combination on a high dimensional nonlinear surface. Due to increasing number of tension forces to search, the convergence is more difficult to attain. In order to increase responsiveness and convergence of genetic algorithm, an adaptive genetic algorithm (AGA) is proposed. Adaptive rules are incorporated in a modified genetic algorithm to regulate control parameters of genetic algorithm. Through numerical simulation and experimental studies, it is demonstrated that AGA can expedite its search process and prevent premature convergence.

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