果蔬采摘欠驱动机械手爪设计及其力控制

Design and Force Control of an Underactuated Robotic Hand for Fruit and Vegetable Picking

为了实现果蔬的无损采摘,采用欠驱动原理设计出一种结构更简单、通用性更强的末端执行器。欠驱动机构是指驱动器数目少于机构本身自由度数目的机构,基于欠驱动原理设计的机械手结构简单可靠,抓取物体时具有形状自适应能力,手指可完全包络物体,可以通过最大接触力的闭环力反馈控制来实现无损采摘。基于这一设计思想设计出仅靠一个电动机驱动三个手指的机械手爪,通过理论分析、手爪机构设计与建模、结构参数优化,确定设计尺寸制出机械手爪,设计控制电路结合力反馈控制进行抓取试验。试验结果表明该手爪能实现期望的抓取与最大接触力控制功能,并具有控制简单可靠、抓取稳定、不损伤果实等特点。

To achieve non-destructive fruit and vegetable picking, an end-actuator with a simpler and more versatile structure is designed based on underactuated principle. The underactuated mechanism refers to machine that has fewer drivers compared with the number of degrees of freedom. The robotic hand designed by adopting the underactuated principle is simpler and more reliable. Due to simple structure and better adaptability to shape of objects, the robotic hand can fold the object completely with its fingers. Non-destructive harvesting is achieved by using a closed-loop force-feedback control algorithm which controls the maximum contact forces. Based on this design idea, a three-finger gripper which is driven by only one motor is designed. Through theoretical analysis, mechanism design and modeling, and structural optimization, the final model size is determined and physical production is completed. A control circuit combined with force-feedback control is designed for grasping experiments. The experimental results show that the robotic hand can achieve the desired grasping function, maximum contact force control and has such features as simple and reliable control, stable grasping and non-damaging.