## 4 Experimental Validation  
To validate the reliability of the theoretical research and achieve the optimized design of the device, an energy management circuit and the coupled rotating energy-harvesting structural model are created. The experimental platform is established to test the device performance at different rotational speeds. The rotary platform, based on the 5D120 GU DC speed-regulating motor of Guangdong Xinxie Electric Appliance Technology Corporation (Maoming, China), achieves adjustable speeds ranging from 10 to 700 rpm, with real-time speed detection using the TM680 high-precision non-contact stroboscope tachometer of Dongguan Sanliang Precision Measuring Instruments Corporation (Dongguan, China). The energy management circuit, based on the LTC3588-1 of Linear Technology Corporation (Singapore) or high-voltage components, provides voltage step-down and regulation protection for piezoelectric or electrostatic components, along with threshold detection, to continuously output a voltage of 3.7 V to the energy storage elements. Based on the structural and dimensional design of theoretical and simulation model, the rotating energy-harvesting-testing platform is shown in Figure 12.  
Figure 12: Non-contact electret–piezoelectric rotational energy-harvesting coupling structure experimental platform. The experiment employed the unipolar electret with charges only on the upper sur-face. To perform the comparative experiment, the piezoelectric components can be replaced with both uniform and non-uniform cross-section cantilever beams, the electrostatic components can also be substituted with alternating polarities and only positive polarity electret. To protect the piezoelectric components, permanent magnets adhered to the white electret support utilize ferrite with an adhesion force approximately 1/8 that of strong neodymium-iron-boron magnets, rather than using the latter. The chemically inert insulated support forms a reliable and stable support for the electret, working together with the copper electrode plates to constitute the electrostatic component. And in the experimental platform, the drive power supply is used to drive a variable-speed rotating motor, replacing the original wind blades drive of the structural design. This facilitates more precise control of the rotor speed for testing the electrical output performance and optimization effects of the device. The speed range of the motor is selected based on the characteristic of the device being driven by wind power for rotation, with the testing range of 100 to 700 rpm. Both theoretical and simulation models indicate that the frequency of change in the open-circuit voltage of the electret electrostatic component is positively correlated with the rotational speed, demonstrating the potential for inversion analysis to extract rotational speed and wind speed information from the output signals of paired electrodes. One pair of electrodes is connected to a high-resistance load for voltage division, and the output signal from the electret component is tested first and shown in Figure 13.  
Figure 13: The alternating polarities electret electrostatic component outputs signals in pairs of plates during operation, exhibiting a positive correlation with rotational speed \(\omega_{r}\) (**a**) rotating at 100 rpm, (**b**) at 175 rpm, and (**c**) at 250 rpm. The experiment employed the unipolar electret with charges only on the upper surface, with arrangement of alternating-polarities electrets in this test. The output signal of the electret component, in comparison to the output of the piezoelectric component performing irregular intermittent vibrations effected by multiple interfering factor, shows a strong and brief positive correlation with rotational speed. The results suggest the potential for inverse analysis to extract information about rotational or wind speed from the output while confirming the correctness of both the theoretical and simulation models.