Development of a telescopic elastic-tooth chili pepper harvester: design and field optimization

A high damage rate of chili peppers and poor removal of bottom fruits are common problems for current mechanical harvesters. To address these limitations, we designed a self-propelled telescopic elastic-tooth pepper harvester that employs horizontally extending telescopic teeth to reduce the picking angle between the harvesting unit and the ground, thereby improving the net harvesting rate of peppers. The structure and contact mode of the teeth were analyzed, and the feasible range of spindle speed and the key factors affecting picking quality were preliminarily determined through kinematic and contact mechanics analysis. A three-factor, three-level Box-Behnken response surface experiment was conducted using forward speed, spindle speed and telescopic elastic-tooth angle as factors, and picking rate and damage rate as evaluation indices. A quadratic regression model was established and used to optimize the operating parameters with Design-Expert. The optimal combination was a forward speed of 58 m·min⁻¹, spindle speed of 201 r·min⁻¹ and telescopic elastic-tooth angle of 4°, under which the model predicted a picking rate of 94.0% and a damage rate of 4.5%. A field verification test at 60 m·min⁻¹ forward speed, 200 r·min⁻¹ spindle speed and 4° telescopic elastic-tooth angle yielded a picking rate of 90.2% and a damage rate of 6.6%, with relative errors below 5%. These results demonstrate that the proposed telescopic elastic-tooth picking unit can effectively improve pepper harvesting performance while maintaining a low fruit damage rate.