Relationship between mechanical property and damage of tomato during robot harvesting

The mechanical property and damage of tomato were studied by the loading-unloading orthogonal test in order to reduce the gripped damage during robot harvesting. The factors included loading position, probe type, finger material, compressibility and loading rate. The results showed that the compressibility had the most significant effect among five mechanical parameters. Additionally, it had correlation between the mechanical parameters. When the compressibility increased by 1%, the average value of strain energy, plastic strain energy, peak force and loading slope raised 26.16 mJ, 19.04 mJ, 4.62 N and 0.16 N/mm respectively while the average value of degree of elasticity decreased by 0.88%. The factors which had significant effects on the mechanical damage of tomato were ordered as compressibility, sphericity, loading position and rate. The average value of degree of mechanical damage raised 2.89% as the compressibility increased by 1%. The regression coefficient between the mechanical properties and the degree of mechanical damage of tomato was 0.7214. The peak force had the most significant relationship with the degree of mechanical damage. This will provide some theory evidences for the design of grip system and the implement of stable gripping-control strategy in harvesting robot.