## 3 Test and Verification
### Test System Parameter Design
#### 3.1.2 Test System Parameter Design  
According to the aforementioned testing methods, we have developed a dual-variable relative angle thermal deformation angle measurement system, which includes a laser spot detection unit, a biplane reflector unit, a post-processing unit, and a condition guarantee unit, the specific composition of which is shown in Figure 10. Among them, the biplane reflection unit and the laser spot detection unit are used for detecting deformation laser spot displacement changes, and the thermal control unit is used for the heating operation of the support frame. Figure 8: Schematic diagram of temperature conditions. Figure 9: Schematic diagram of changes in thermal deformation angle. For laser spot displacement detectors, we choose position sensitive detector (PSD) devices [23]. This is because PSDs have the following advantages [24]: (1) the shape of the light spot does not affect the measurement of the displacement change value of the light spot by the PSD; (2) the PSD target resolution is extremely high and has achieved 1 \(\upmu\)m resolution; (3) the PSD has a high sampling frequency, which can output the spot coordinate value in real time, which is conducive to the development of test automation equipment in the later stage. Therefore, PSDs are widely used in non-contact rapid measurement of displacement and distance [25]. Meanwhile, with the further evolution and optimization of PSDs, the measurement accuracy of PSDs will become more precise. For example, the 3 CSiC/Si hetero structure proposed by [PERSON], [PERSON] et al. may be a position-sensitive detector [26], which is a promising choice in harsh environments (such as highly corrosive environments). Therefore, choosing PSDs in this study is more conducive to the later promotion and application of the testing plan. Therefore, choosing PSD devices is more conducive to the promotion and application of this scheme. Finally, we select Shanghai Ou-guang Company's S2-0003-2L10-SU24 two-dimensional PSD and its controller [27]. Its resolution is 1 \(\upmu\)m, effective photosensitive surface is 10 \(\times\) 10 mm, spectral response range is 380-1000 nm. The composition of the entire testing system is shown in Figure 11. The laser passes through two reflection cycles and lands on the PSD, with two planar mirrors spaced at a distance of H of 3435 mm. According to the biplane reflection principle mentioned earlier, the parameters of the above testing system are brought into Equation (16), and the testing resolution of the testing system is 0.015\({}^{\prime\prime}\), which can achieve angle testing accuracy of bivariate angles in super-sub-arc. Figure 10: Layout diagram of testing system. Due to the thickness of the bottom plate of the support frame reaching 32 mm, under the condition of slow thermal conductivity of the frame material, there may be inconsistencies in the temperature values of the front and rear surfaces at the same position. For this purpose, heating plates and temperature measurement points are set on the front and back of the support frame bottom plate, and each is independently controlled for temperature. The coverage and thermal coating of the heating element implemented by the thermal control of the support frame are shown in Figure 12, and the distribution of the thermistor is shown in Figure 13. The temperature measurement accuracy of the thermistor used is \(\pm\)0.1 \({}^{\circ}\)C, and the appearance is shown in Figure 14.  
Figure 11: Principle sketch for the experiment. Figure 12: Thermal control implementation; (**a**) Pasting heating pads; (**b**) Thermal coating. The target reflector is connected to the support frame through an adapter plate and leads out in the normal direction of the installation surface of the support frame, as is shown in Figure 15a.