*2.3. Test Acquisition Method*

The welding material used in the test is an 2A14-T6 aluminum alloy plate with the same size and simulation. The 2A14 aluminum alloy is a high-strength aerospace aluminum alloy. The internal material composition is shown in Table 3 [36]. The tool shoulder diameter is 16.3 mm, the tool cone angle is 15◦, and the overall size is consistent with the simulation model parameters. The welding process is completed on a self-developed high-precision friction stir welding robot. During the welding process, the spindle speed is 900 r/min, the welding speed is 100 mm/min, and the tool shoulder is plunged against the workpiece surface by 0.2 mm. The welding inclination angle is 2.5◦, after the tool needle is pressed down to a certain amount, it will dwell and rotate for 10 s. The overall welding parameters are consistent with the simulation parameters.

**Table 3.** Chemical composition of 2A14 Aluminum Alloys.


The axial force and torque in the welding process are collected by electromagnetic coupling technology, and wireless power transmission is adopted, as shown in Figure 5. Most scholars use the method of setting the mechanical sensor at the bottom of the workpiece for data acquisition. However, since the measurable area of the sensor is limited, when the welding center deviates from the center of the sensor, the accuracy of the test method will be greatly reduced; thus, it is difficult to track and collect long welds.

**Figure 5.** Signal acquisition method.

In the magnetic coupling resonant radio energy and signal transmission system, the primary side uses the amplitude shift keying (ASK) method to load the signal into the power transmission channel for a synchronous transmission, and uses the non-coherent demodulation method to extract and recover the signal on the secondary side. The schematic diagram of the acquisition method is shown in Figure 6. The power and signal synchronous transmission method can reduce the inverter link, reduce the loss and improve the quality of the advancing signal transmission.

**Figure 6.** Schematic diagram of electromagnetic coupling signal transmission.
