Parameter Optimization for Vibratory Harvesting of Wolfberry Branches Based on Dual Low-Frequency Vibration Excitation and Singular Value Spectrum

Abstract

To overcome empirical and discrete parameter selection and severe energy attenuation in wolfberry (Lycium barbarum L.) harvesting using single-source vibration, in this study, a dual-source low-frequency excitation method is proposed. Using ‘Ningqi No.7’ branches and a two-point synchronous excitation device, the effects of the amplitude (28 to 80 mm) and phase (-180° to 180°) of the upper and lower vibration sources (UVS and LVS) on the detachment percentages of the middle section, lower section, and the total detachment (TD) were investigated via response surface methodology. Singular value spectrum analysis of the acceleration signals extracted the maximum singular value (MSV) to quantify the overall branch vibration energy. Two main low-frequency modes near 4 Hz and 8 Hz with high damping were identified. The MSV was strongly correlated with TD (r = 0.751), confirming its reliability for effectiveness evaluation. The optimal parameters found were a UVS of 80 mm, LVS of 68 mm, and phase of 135°, yielding a TD of 85.9% in validation. This demonstrates that the synergistic control of amplitude and phase at a low frequency enhances the harvest efficiency, offering a new approach for intelligent parameter optimization based on vibration monitoring.