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

Abstract

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.

Experimental characterization for active flatness control of membrane structures

“…The membrane flatness, in terms of root mean square (rms) of d, of those measured points , is calculated using the following equation, effects of mechanical loading and how boundary tension forces can change thermal effects? Numerical simulations have been performed to investigate thermal and mechanical effects on membranes [10]. In order to validate these results and answer questions on some other control issues, systematic experimental studies have to be pursued.…”

Adaptive Shape Control for Thermal Deformation of Membrane Mirror with In-plane PVDF Actuators

“…A series of tests on membrane shape control with SMA wires were undertaken by the Canadian Space Agency. A generic algorithm-based control system was developed and tested on a square membrane by Peng et al [14][15][16][17] and Wang et al [18][19][20] investigated active flatness control of membrane structures under thermal and mechanical loads with SMA actuators. Furthermore, Shan et al [21] in York University developed a photogrammetry software to measure the flatness of a membrane structure that actively boundary controlled by SMA wires.…”

An Experimental Study on the Interaction of Thermal Loading and Mechanical Loading in Membrane Structures

“…How thermal loading effects would affect the effects of mechanical loading and how boundary tension forces can change thermal effects? Numerical simulations have been performed to investigate thermal and mechanical effects on membranes [15]. In order to validate these results and answer questions on some other control issues, systematic experimental studies have to be pursued.…”

“…Wang et.al. [15] applied a TST based method to compute wrinkle amplitudes and areas caused by thermal fields. The root‐mean square (rms) of membrane surface deviations is also calculated.…”

“…In both Balandio and Wang’s studies [15, 16], the sequentially coupled thermo‐mechanical procedure is used, i.e. heat generated by membrane mechanical deformation is ignored.…”