Tomato’s Mechanical Properties Measurement Aiming for Auto-harvesting

Freshly-eating tomato's auto-harvesting is urgently needed to replace labor-costly manual harvesting. And a feasible picking end-effector is a key part for mechanical harvesting, as the irregular-sized and soft fruits should be reliably separated from the plant. In this paper, the mechanical properties of "Jiali 14" tomato was measured and analysed to support the design of picking end-effector. The methods and devices for measuring a series of force parameters were researched, including fruit/stalk friction coefficient, fruit pressure resistance, stalk cutting force, and abscission-layer breakage force. Through measuring the pressure and maximum static-friction force between the fruit/stalk and the contrast material, the friction coefficients between fruit/stalk and stainless steel, PVC and rubber was calculated. The pressure resistance of fruit also was evaluated by measuring the extreme pressure on the test samples, and the influences from the fruit's maturity and the pressure direction also were analysed. The stalk cutting force, with the single and double blade, both was measured and compared. The breakage force of the calyx abscission-layer and the tie abscission-layer also was measured, and the force value variation with its anisotropy and the fruit maturity was analysed. The measurement and analysis result in this paper was supposed as a necessary reference for developing the tomato's auto-harvesting machine.