仿生变刚度关节设计与试验

Design of Bionic Variable Stiffness Joint

变刚度关节是一种具有本质柔顺性的机器人机构,能够提高机器人与人交互作用时的安全性。本文设计了一种采用弹簧片的机械式仿生变刚度关节,利用差动轮系实现关节位置与刚度的独立控制。基于弹簧片大挠度变形,在关节中采用的2种弹簧片末端施力结构对刚度特性的影响进行分析,仿真结果表明,末端施力结构对偏转时的刚度变化有较大影响。对变刚度关节样机的刚度性能进行试验,试验结果与仿真结果一致,表明该关节具有较大的刚度变化范围,并且2种末端施力结构可以分别满足持续高刚度和碰撞安全性的应用要求。

Variable stiffness joints are a kind of compliant mechanism to improve the safety of physical human-robot interaction,which has attracted much attention in recent years. Elastic elements are used in the internal kinematic structures of variable stiffness joints. A new mechanically bionic variable stiffness joint using leaf springs was designed. The joint stiffness was adjusted by changing the effective length of leaf springs. By controlling the relative motion of the differential gear train,the position and stiffness of variable stiffness joint can be controlled respectively. Two structures were used in the new joint to exert external forces on the ends of the leaf springs. Based on the elliptic integral solution to large deflection problems of cantilever beams,the effects of two force exertion structures on the joint stiffness property were studied. The simulation results showed that the force exertion structure of the end had great effect on the stiffness during the joint deflection. The joint stiffness was decreased as the increase of joint deflection angle when the force exertion structure was that the external force point was fixed to the joint arm. The stiffness was increased with the increase of deflection angle when the force exertion structure was that the external force point moved relative to the joint arm. The physical experiments of the prototype were conducted to verify the validity of the analysis results. The experimental results showed that the changing range of the joint stiffness was larger. And two force exertion structures can meet the requirements of continuous high stiffness and collision safety respectively.