Purpose <p>Based on the Timoshenko beam theory, this paper investigates the energy harvesting performance of an asymmetric tri-stable piezoelectric energy harvester (RATPEH) under rotational motion.</p> Methods <p>A nonlinear dynamic model of the RATPEH system is established using Hamilton’s variational principle. The harmonic balance method is employed to derive an analytical solution for the electromechanically coupled equations of motion. Combined with numerical simulations in MATLAB, the effects of magnet offset distance, beam width, and metal layer material on the dynamic response of the RATPEH are systematically studied, and a comparative analysis with the Euler–Bernoulli beam model is also conducted.</p> Results <p>The results demonstrate that the peak power and operational rotational speed range predicted by the Timoshenko beam model are significantly higher than those obtained from the Euler–Bernoulli beam model. However, the discrepancy between the two models diminishes as the beam width decreases. This indicates that the influence of geometric dimensions on the dynamic response cannot be neglected in the design of piezoelectric energy harvesters under low-speed rotational conditions. Furthermore, the asymmetric potential well configuration leads to improved energy harvesting performance. When d0 = 4 mm, the displacement and output power peaks increase by 41.3% and 37.8%, respectively, compared to the symmetric structure (d0 = 0), and the peak responses shift toward lower rotational speeds. Although increasing the beam width improves the output power, it narrows the effective operational speed range.</p> Conclusions <p>A trade-off between power gain and bandwidth loss must be considered in the design of piezoelectric energy harvesters. Additionally, appropriate selection of the metallic layer material can substantially improve the energy harvesting efficiency of the system.</p>