Modal experiment analysis on blackcurrant branches

In order to investigate the movement characteristics of blackcurrant branches during harvesting operation, a series of experimental modal analysis were performed by using the stepping sinusoidal excitation, one-point excitation and multi-point acceleration response method based on the assumption of bush branches as cantilever structure fixed a support to match with the actual situation of the bush in the farm. And the least square complex exponent method was employed to fit the modal parameters of the branches. The results indicated there existed one or two resonance frequencies in the range of 4 to 30 Hz on the blackcurrant branches under natural frequency of 11.8±4.54 Hz. The wide distributions of data were shown in the damping ratio, the modal mass and the modal stiffness of the branches and the average value was 7.08%, 0.0686 kg and 394.8 N/m, respectively. These results provide design parameters and basis for the blackcurrants harvesting system.