Abstract:Aiming at the problem that the end-effector picking force is poorly matched with fruits and vegetables,resulting in a high damage rate and low versatility,a contact force optimization method for non- destructive grasping of spherical fruits and vegetables based on dexterous hands was proposed. The separation scheme of spherical fruit and vegetable picking was analyzed, and a frictional non-destructive point contact model was established. Peaches in the picking period were taken as the research object,and the static friction coefficient and non-destructive contact parameters between the fingertip material and peaches were experimentally determined. The kinematic model and Jacobian matrix of the multi-finger dexterous hand were established based on the screw theory, the force balance constraint of fruit and vegetable picking was analyzed,and the force-position mapping model of joint contact point fruit and vegetable was constructed. A grasping planning method for dexterous hands based on minimum force was proposed,and the solution analysis was carried out using the picking of peaches as an example,and the optimal solution of the planning model was obtained based on the NSGA II algorithm. Field peach picking experiments showed that this method can achieve stable grasping and picking of peaches with a radius of 2.6 ~ 8 cm,effectively avoiding damage to fruits and vegetables during the picking process. The average absolute contact force error between the actual measured value and the theoretical calculated value was 0.39 N, the picking success rate was 92% , the non-destructive rate was 97.8% , and the average picking time was 10.3 s,which met the needs of dexterous hands for non-destructive and stable picking.
