面向机器人采摘的荔枝果梗力学特性

Mechanical properties of litchi stem for harvesting robots

为了给荔枝采摘机器人夹持与切割器的设计和控制提供依据,对荔枝果梗分别进行了切割性能和夹持性能的影响因素试验以及弯曲试验。试验结果表明:峰值切割力和切割强度随着切割速度增加而减小,随着切割角度的减少而减少,凹刃和凸刃的峰值切割力和切割强度都比平刃小;除果梗直径因素外对峰值切割力和切割强度影响显著的因素均依次为切割角度、刃口形式和切割速度;切割角度每减少1,峰值切割力和切割强度分别减少4.45N和0.16MPa;相比平刃的峰值切割力和切割强度,凸刃分别减少166.90N和2.11MPa,而凹刃分别减少167.39N和4.21MPa。随着夹持力增加,荔枝果梗与夹持物间摩擦力增加,夹持物为橡胶时,摩擦力最大,夹持力对摩擦力的影响大于夹持材料;试验范围内,最大摩擦力为44.54N。荔枝果梗具有较强的抵抗变形的能力,平均弹性模量为867.15MPa;试验范围内,最大弯曲力的平均值为118.95N,抗弯强度的平均值为56.03MPa。该研究为荔枝采摘机器人的夹持与切割机构的优化设计和控制提供了理论依据。

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.