Initial Control Results for the Thirty Meter Telescope

MacMynowski, Douglas G.; Blaurock, Carl; Angeli, George Z.; Meter, Thirty

doi:10.2514/6.2005-6075

Cited by 4 publications

(6 citation statements)

References 28 publications

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“…11,12 Progress has also been made in modeling the dynamic response of the telescope structure to the wind disturbance. 12,13 Similar efforts in understanding the wind and the telescope response have been made by other design teams. 14 The fundamental purpose of any model is to inform particular design decisions.…”

Section: Introductionmentioning

confidence: 87%

“…The coupling of these resonances through the structure leads to a spread in resonant frequencies. 13 However, while these structural resonances limit the achievable bandwidth of the primary mirror control system, there is insufficient wind energy at these frequencies for these resonances to contribute significantly to the telescope dynamic response. Therefore, rather than designing a single model that can simultaneously estimate the controlstructure interaction with the entire primary mirror control system while also estimating the wind-induced buffeting of the structure, it is far more efficient to separate these tasks and design one model that can assess the achievable control bandwidth, and a separate model that can estimate the wind response.…”

Section: Raytracementioning

confidence: 99%

“…The resonances themselves can be separately added for assessing achievable primary mirror control bandwidths as in Ref. 13. The 738 segment nodes are adequate to describe the low wavenumber deformation of the primary mirror that is relevant to seeing-limited image degradation, and it is not necessary to predict the rotations of the segments: this reduces the number of input degrees of freedom by nearly a factor of three.…”

Section: Telescope Structurementioning

confidence: 99%

“…The overall telescope involves many control loops, 13 several of which have a significant impact on the wind response of the telescope. The most important in terms of image stability are the main axis drives, and the elevation drive in particular.…”

Section: Controlmentioning

confidence: 99%

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Modeling wind-buffeting of the Thirty Meter Telescope

MacMynowski

Blaurock²,

Angeli³

et al. 2006

SPIE Proceedings

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The Thirty Meter Telescope project is designing a 30 m diameter ground-based optical telescope. Unsteady wind loads on the telescope structure due to turbulence inside the telescope enclosure impact the delivered image quality. A parametric model is described that predicts the optical performance due to wind with sufficient accuracy to inform relevant design decisions, including control bandwidths. The model is designed to be sufficiently computationally efficient to allow rapid exploration of the impact of design parameters or uncertain/variable input parameters, and includes (i) a parametric wind model, (ii) a detailed structural dynamic model derived from a finite element model, (iii) a linear optical response model, and (iv) a control model. Model predictions with the TMT structural design are presented, including the parametric variation of performance with external wind speed, desired wind speed across the primary mirror, and optical guide loop bandwidth. For the median mountaintop wind speed of 5.5 m/s, the combination of dome shielding, minimized cross-sectional area, and control results in acceptable image degradation.

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Section: Introductionmentioning

confidence: 87%

Section: Raytracementioning

confidence: 99%

Section: Telescope Structurementioning

confidence: 99%

Section: Controlmentioning

confidence: 99%

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Modeling wind-buffeting of the Thirty Meter Telescope

MacMynowski

Blaurock²,

Angeli³

et al. 2006

SPIE Proceedings

Self Cite

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“…TMT, shown in Fig. 1-2(f), is a planned thirty meter diameter telescope operating in the ultraviolet to infrared wavelengths [54]. It is at the end of the design phase and will investigate planet, star and galaxy formation.…”

Section: (D)mentioning

confidence: 99%

Spatial Nyquist fidelity method for structural models of opto-mechanical systems

2008

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As technology employed in complex multidisciplinary systems such as high performance telescope systems becomes ever more sophisticated, simulation is becoming more important during the initial design phases. The method of building these simulation models is often based on engineering experience with older, potentially dissimilar systems. A method is needed to measure the fidelity of simulation models so early design decisions are made based on appropriate modeling techniques.Previously, fidelity was a qualitative concept used to indicate a model's validity or accuracy. Here it is defined as the ability of a model to accurately predict chosen output figures of merit. In this thesis, a quantitative measure of fidelity, termed the Nyquist fidelity metric, is defined for commonly used structural model components. It expresses the ability of a finite element model to accurately predict structural eigenvalues based on the mesh size required by the spatial Nyquist criterion. The Nyquist fidelity method is developed which uses the fidelity metric to both assess the fidelity of existing complex models and to synthesize new multi-component models starting from architectural considerations such as geometric and material properties of the system. This method also estimates the error bound on the output figures of merit based on the fidelity levels and sensitivity analysis.The Nyquist fidelity method is applied to simple sample problems to first demonstrate the methodology and it is then applied to complex telescope models to show the accuracy and computational benefits of this method compared to current methods such as model reduction. The three high performance telescope case studies are the Modular Optical Space Telescope (MOST), the Thirty Meter Telescope, and the Stratospheric Observatory for Infrared Astronomy. It is shown in the MOST example that the Nyquist fidelity method provides a 40% improvement in computational time while assuring less than 5% modal frequency error, and less than 2.2% error in the output figure of merit.

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