Output characteristics analysis of pendulum type triboelectric nanogenerators considering nonlinear electromechanical coupling effects

In this study, output characteristics analysis of pendulum type triboelectric nanogenerators (P-TENG) considering nonlinear electromechanical coupling effects is conducted. Based on the analysis of power generation mechanism, an equivalent capacitance model is proposed. Combined with the energy principle and equivalent circuit method, an electromechanical coupling model considering the nonlinear variation of pendulum angle is established. Using the harmonic balance method (HBM) and alternated frequency/time domain technique, the steady-state output of the P-TENG is solved analytically, and the stability of the results is determined. Numerical integration and dynamic tests are used to verify the accuracy of HBM results. By comparing the changes in the P-TENG output performance with and without the nonlinear effect, it is shown that the model proposed in this study can effectively avoid the underestimation of the operation bandwidth (a relative increment of 83%) and significantly improve the accuracy of the P-TENG performance estimation. Based on these results, the influence of the design parameters (including excitation amplitude, damping ratio, gap length, and electrode angle) on the dynamic output characteristics of the system is discussed. The output performance of the P-TENG can be improved by increasing the excitation amplitude, reducing the damping ratio, and minimizing the electrode angle. In the actual design, the gap length and friction amplitude should be comprehensively considered to maintain the P-TENG output performance in a better state. Various fitting models have been proposed to model the relationship between the design parameters and output performance. The fitting coefficients obtained from the parameter influence discussion can be used as the basis for the P-TENG output performance design.