Advances in edge sensors for the Thirty Meter Telescope primary mirror

Shelton, Chris; Mast, Terry S.; Chanan, G. A.; Nelson, Jerry; Roberts, Lewis C.; Troy, Mitchell; Sirota, Mark J.; Seo, Byoung-Joon; MacDonald, D.

doi:10.1117/12.790415

Cited by 12 publications

(6 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The edge sensor (Mast et al 1983;Chanan et al 2004;Shelton et al 2008) includes two parts, the sensor body and the target (a plane mirror), as shown in Figure 1. The main body is composed of a light-transmitting part, a lightreceiving part, and a collimating lens.…”

Section: Working Principle Of the Edge Sensormentioning

confidence: 99%

Edge sensor based real-time calculation method for active panel position of QTT

Wang

Yan

et al. 2020

Res. Astron. Astrophys.

View full text Add to dashboard Cite

QiTai Telescope (QTT), the world's biggest full-steerable telescope, will be constructed in Xinjiang, China. Its extra high operating frequency (115 GHz) imposes strict requirements on the accuracy of the reflector, while its large aperture (110 m) increases the impact of antenna weight and environment on surface accuracy. However, the panels of reflector will deform under the influence of gravity and the environment. Therefore, to compensate for the performance degradation caused by this deformation, a technique called active surface adjustment has been proposed. The existing adjustment methods cannot detect the deformation caused by environment of the reflector surface in real time, which can result in a delay in the compensation. Consequently, it is difficult to achieve an optimal compensating result. To solve this problem, a real-time method to estimate the large-aperture reflector antenna surface by calculating the antenna panel position based on edge sensors is proposed in this paper. In the proposed method, a panel coordinate transfer matrix has been formulated and the data measured from these edge sensors can then be treated as input for the proposed transfer matrix to calculate the actual position of the antenna panel in real time. A numerical simulation has been carried out in the QTT model and the results obtained show that the proposed real-time method is a promising tool to estimate the large reflector surface position in real time. It is believed that this active surface adjustment method has laid the foundation for new methods that will be developed to compensate for the reflector electrical performance.

show abstract

Section: Working Principle Of the Edge Sensormentioning

confidence: 99%

Edge sensor based real-time calculation method for active panel position of QTT

Wang

Yan

et al. 2020

Res. Astron. Astrophys.

View full text Add to dashboard Cite

show abstract

“…A singular value decomposition of A hz has been useful in understanding the properties of this matrix [6]. The output signal from each sensor is a linear combination of a signal generated by a height change and a signal due to the change in dihedral angle (relative rotation about the shared segment edge) [8]. The relative sensitivity between these has units of length (i.e., m∕radian), and is denoted L eff ; (at Keck, L eff 55 mm corresponds to a physical moment arm).…”

Section: A Descriptionmentioning

confidence: 99%

“…Other than the effect of the unobservable torsion mode, the vector of in-plane motion w can be estimated from the gap measurements, and this used to estimate the shear at sensor locations [8]. This allows calibration of the sensor response to both gap and shear motion using only gap measurements, with errors due to the unobservable torsion mode, and due to the propagation of gap-measurement noise.…”

Section: Estimation Of In-plane Motionmentioning

confidence: 99%

“…Nonzero sensor installation errors also result in cross-talk between the gap and shear motion at the sensor location and the sensor height reading; this can be a significant effect if not corrected. These effects can be minimized by estimating the in-plane motion, and using this to correct the desired sensor readings based on a calibration algorithm [8].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

In-plane effects on segmented-mirror control

et al. 2012

Self Cite

View full text Add to dashboard Cite

Extremely large optical telescopes are being designed with primary mirrors composed of hundreds of segments. The "out-of-plane" piston, tip, and tilt degrees of freedom of each segment are actively controlled using feedback from relative height measurements between neighboring segments. The "in-plane" segment translations and clocking (rotation) are not actively controlled; however, in-plane motions affect the active control problem in several important ways, and thus need to be considered. We extend earlier analyses by constructing the "full" interaction matrix that relates the height, gap, and shear motion at sensor locations to all six degrees of freedom of segment motion, and use this to consider three effects. First, in-plane segment clocking results in height discontinuities between neighboring segments that can lead to a global control system response. Second, knowledge of the in-plane motion is required both to compensate for this effect and to compensate for sensor installation errors, and thus, we next consider the estimation of in-plane motion and the associated noise propagation characteristics. In-plane motion can be accurately estimated using measurements of the gap between segments, but with one unobservable mode in which every segment clocks by an equal amount. Finally, we examine whether in-plane measurements (gap and/or shear) can be used to estimate out-of-plane segment motion; these measurements can improve the noise multiplier for the "focus-mode" of the segmented-mirror array, which involves pure dihedral angle changes between segments and is not observable with only height measurements.

show abstract

“…In the horizontal layout, the sensor is positioned parallel to the mirror surface along its edge, while in the vertical layout, it is placed perpendicular to the mirror. A typical example of the vertical layout is the edge sensor used in the TMT [10]. This design employs non-interlocking and non-moving parts to simplify segment replacement.…”

Section: Introductionmentioning

confidence: 99%

A Novel Tandem Differential Edge Sensor Layout for Segmented Mirror Telescopes

Huo,

Yang,

Wang

et al. 2023

Sensors

View full text Add to dashboard Cite

The performance of an active control system, crucial for the co-phase maintenance of segmented mirrors, is closely related to the spatial layout of sensors and actuators. This article compares two types of edge sensor layouts, vertical and horizontal, and proposes a novel tandem differential sensor layout that saves layout space and reduces the number of positioning references. The control performance of this scheme is analyzed in terms of error propagation, mode representation, and the scalable construction of the control matrix. Finally, we constructed a tandem differential-based sensor detection system to examine the performance of edge sensors and the effect of laboratory environmental variables on sensor measurements. Simulations and experiments demonstrate that this scheme has the same ability to fully characterize actuator modification modes as the Keck edge sensor layout. Although the total error multiplier is slightly larger than the latter, it has fewer scalable control matrix types and stronger spatial and segmental shape adaptation capabilities. Actual measurements show that the sensor’s own noise in a tandem differential layout is less than 20 nm, which meets the requirements for future segmented co-phase maintenance. This layout type can potentially be applied to future small and medium-sized segmented splices.

show abstract

Advances in edge sensors for the Thirty Meter Telescope primary mirror

Cited by 12 publications

References 8 publications

Edge sensor based real-time calculation method for active panel position of QTT

Edge sensor based real-time calculation method for active panel position of QTT

In-plane effects on segmented-mirror control

A Novel Tandem Differential Edge Sensor Layout for Segmented Mirror Telescopes

Contact Info

Product

Resources

About