xTS_CT原位加載系統

xTS – Mechanical Testing System In X-ray Tomography Imaging System

X射線斷層圖像系統的原位加載系統

Psylotech的xTS是一種設計用于X射線斷層成像系統內的原位加載機械測試系統。xTS在CT掃描過程中是載荷系旋轉而非框架本體，從而解決了傳統加載裝置存在的支撐柱干擾X射線的問題。通過旋轉載荷系還允許將探測器放置在盡可能靠近樣品的位置，對射線能量有更高的利用率。

該系統是基于Psylotech的運動控制平臺，是專門設計用來限制離面運動的系列儀器中的一款，著重于改善圖像捕捉質量。例如，在光學顯微鏡下，離面運動的標準偏差已被證明小于1微米。控制離面運動對于X射線斷層掃面描同樣很重要，因為它的分辨率可以達到2微米或更小。

Psylotech的加載框架設計通過：1/加載對稱、2/高加工精度和3/直接驅動絲杠作動器控制平面外運動，通過精度為0.005mm的公差基準面與設計對稱性相結合，有效控制額外的彎矩。關鍵的是，作動器實現了運動部件的最少化，伺服電機的轉子是螺母，絲杠隨著螺母的轉動而轉動。最少化的運動部件可減少誤差累積，保持精度。

Psylotech's xTS is mechanical testing system designed for use with x-ray tomography imaging systems. The xTS rotates the load train in the CT scanning process, thereby solving the problem of support columns interfering with x-rays. The rotating load train also allows the detector to be placed as close as possible to the specimen.

Built on Psylotech's motion control platform, it is part of a line of instruments specifically designed to limit out of plane motion, thereby improving image capture. For example, under optical microscopes, standard deviation of out of plane motion has been shown to be less than one micron. Controlling  out of plane motion is important for x-ray tomography, when resolution can be as fine as 2 microns.

Psylotech's patented load frame design controls out of plane motion through 1/loading symmetry, 2/high machining accuracy, and 3/a direct drive roller screw actuator. Precision 0.0002” tolerance reference surfaces combine with design symmetry to prevent extraneous out of plane forces. Crucially, the actuator implements the absolute minimum of moving parts. The servomotor’s rotor is the nut and the screw translates as the nut rotates. Minimizing moving parts reduces tolerance stack- up, maintaining precision.

直接驅動滾柱絲杠還有另一個重要的優點，相較于采用齒輪箱或皮帶傳動裝置的加載框架，沒有引入額外的彎矩，而這些力會導致框架的扭曲變形，會使樣品從初始加載平面偏離。 而Psylotech的xTS沒有變速箱， 它通過直接驅動消除了這種扭曲力。

與其他系統相比，直接驅動伺服還具有相當的速度優勢，因此每次斷層掃描可以在更短的時間內完成。此外，樣本旋轉的測量直接來自用于伺服反饋的26位編碼器。26位分辨率意味著xTS可以旋轉0.0000054度。

除了可以施加軸向載荷，xTS還具有扭轉試驗能力。同樣的，扭轉伺服執行器通過零齒隙的諧波驅動，而不會產生額外的扭轉力。這些伺服系統控制絲杠的旋轉，絲杠按比例從屬于螺母，以控制位移和角度位置。高剛性的結構和直接驅動載荷系減少了轉角測量的誤差。

最后，xTS還可以配置環境腔。該環境腔前后各有一個窗口，以允許X射線通過。為使內部體積最小化，可將該室旋轉90度，以容納軸向或梁彎曲樣品。減小體積可提高效率、簡化控制并提高溫度均勻性。

總之，Psylotech的xTS通過對稱性設計、精密的加工品質和直接驅動作動器的組合，獨特地控制了樣品在測試過程的離面運動。因為數字體相關的分辨率可以小到2微米，所以控制離面運動對于X射線斷層成像非常重要。xTS還提供26位的角度分辨率并保有未來增加環境腔的擴展潛力。

The direct drive roller screw has another substantial advantage. Alternative frames implement gear boxes or belt drive transmissions, introducing extraneous out of plane forces. These forces twist and contort the frame, moving samples away from the initial loading plane. Psylotech’s xTS has no gearbox. Its direct drive eliminates such twisting forces.

The direct drive servo also enables substantial speed compared to other systems, so each tomography scan can be completed in less time. Moreover, specimen rotation is measured directly with the same 26-bit encoder used for servo feedback. The 26-bit resolution means the xTS can resolve 0.0000054 degrees in rotation.

In addition to axial loading, the xTS implements torsion capabilities. Again, the torsion servo actuator implements a zero backlash harmonic drive that does not cause extraneous twisting forces. These servos control the rotation of the screw, which is ratiometrically slaved to the nut to control displacement and angular position. The rigid, direct drive load train reduces error between measurement and angle at the grip.

Finally, the xTS can be configured with a temperature chamber. The chamber would have a window  in front and back to allow x-ray pass through. To minimize internal volume, this chamber can be rotated 90 degrees in order to accommodate axial or beam bending samples. Minimizing volume improves efficiency, simplifies control and improves temperature uniformity.

In summary, Psylotech’s xTS uniquely controls out-of-plane motion though a combination of symmetry, precision machining and a direct drive actuator. Controlling out-of-plane motion is important for x-ray tomography, because digital volume correlation resolution can be as small as 2 microns. The xTS also offers 26-bit angular position resolution and future expansion potential with an environmental chamber.

規格/ Specifications

*minimum value, longer strokes available at expense of system height

**higher speeds available at expense of force capacity

***minimum value, system height easily increased

xTS在美國實驗力學學會 SEM 2020年會上的介紹