Abstract:This paper focused on the special collision phenomenon of fruit gripping with its own characteristics of continuous energy input and restrained deformation. The gripping collision process was divided into three stages: constant-speed loading, collision decelerating and stress relaxation, and a three-stage gripping collision model was put forward under the conditions of constant static loading capacity and constant speed control mode, which was based on the stage dynamic characteristic of gripping collision process and viscoelastic Burger`s model of fruits. It was proved by test that the prediction of the peak collision force was feasible, and the predicton error under initial gripping speed of 19.2mm/s was 1.12%. By calculating with this model, it was found that time needed to grip fruit in different ripe period under initial speed of 6mm/s was 0.62~1.24s, and further raising the initial speed might have very limited effectiveness to improve the gripping efficiency. The peak collision force and fruit deformation were proportional and approximately proportional to initial gripping speed, respectively. Probability of skin rupture increased greatly with initial gripping speed. When initial gripping speed was under 20mm/s, probability of skin rupture of green ripening stage and early red ripening stage were the greatest and the least, respectively. This three-stage gripping collision model may provide helpful reference to discover the special law of gripping collision and to achieve high-speed safe gripping of fruits.