Optimization and experimental study on structural parameters of bio-inspired tarsus compliant end-effector to reduce the risk of fruit sliding out from end-effector for cherry tomato harvesting

Abstract

High success rate of fruit picking is part of key technologies for robotic cherry tomato harvesting, which is closely related to the structure of end-effector. In order to prevent the fruit slipping from the end-effector for a high success rate of fruit picking during picking process, this paper presents a compliant end-effector with bio-inspired tarsus compliant gripper inspired by the structure and mechanics of the tarsal chain in the Serica orientalis Motschulsky. An experimental study to confirm the effect of the key structural parameters of the compliant end-effector on the angle (ESGA) formed by the extended segment tarsomere of two bio-inspired tarsus compliant grippers. Experiments were designed according to response surface methodology—box Behnken design by maintaining three levels of four process parameters—length of the offset segment tarsomere (OSL), angle of the inclined segment tarsomere (ISA), thickness of the extended segment tarsomere (EST), and length of the extended segment tarsomere (ESL). Results showed that ISA is the most important parameter, and ESL has little effect on ESGA, and ESGA was found within the range of 4.2°–17.5°. Results also revealed that the desired ESGA (12°) was obtained by the optimum conditions of OSL of 2.4 mm, ISA of 18°, EST of 4.9 mm, and ESL of 18 mm. Besides, the key structural parameters of the bio-inspired tarsus compliant end-effector are optimized by the expectation function. The reliability and feasibility of the constructed model are verified by validation experiments.