Mechanical properties of litchi stem for harvesting robots

To provide a basis for the design and control in litchi harvesting robot clamping and cutting device, effect factors test of cutting and clamping properties and bending test were carried out. The results showed that: the peak cutting force and cutting intensity decreased with the increasing of cutting speed and decreasing of cutting degree; the peak cutting force and cutting intensity with concave and convex blades were smaller than that with flat blade; It is easy to see that, except the diameter of stem, the factors significant on peak cutting force and cutting intensity were followed by cutting angle, edge forms and cutting speed; When the cutting angle reduced one degree, the peak cutting force and cutting intensity would reduce 4.45 N and 0.16 MPa; Compared with the flat blade, the convex edge were reduced 166.90 N and 2.11 MPa in peak cutting force and cutting intensity while the concave edge were reduced 167.39 N and 4.21 MPa. The friction between litchi stem and gripping material would increase with the addition of clamping force. When the gripping material was rubber, the friction reached maximum. And the clamping force effect was greater than the clamping material; In the test range, the maximum friction can reach to 44.54 N. The litchi stem has strong anti- deformation ability, and its average elastic modulus was 867.15 MPa; in the test range, the average of the maximum bending force was 118.95 N while its bending strength was 56.03 MPa. The study can provide a theoretical basis for the optimized design and control in litchi harvesting robots clamping and cutting device.