Study on Deformation and Contact Force Stability of a Novel Flexible Self-Adaptive Picking Manipulator

Fruit harvesting is an important progress of the agricultural production. A pneumatic flexible self-adaptive manipulator with finger and wrist structure is proposed for achieving nondestructive fruit harvesting. The finger and wrist are manufactured by 3D printing technology, and the material is thermoplastic urethane and polylactic acid respectively. Flexible deformation is used to grasp fruit that ensures the integrity of fruit. Structure of the manipulator is designed based on the deformation range. Kinematics model of the flexible wrist was built and deformation law of the flexible finger was established. Further, the flexible finger simulation was set up for the deformation and stable contact force experiment, and the change of minimum contact force was taken as the optimization of objective target. The prototype of improved flexible manipulator was made based on the optimization results. The stable contact force is verified through the manipulator test by using the improved prototype. The results show that an optimized structure is obtained, and it has a minimal change in contact force. Moreover, the flexible manipulator has a favorable self-adaptive function based on the structural design. In addition, the complexity of the feedback and control systems is reduced.