一种新型自适应康复外骨骼机构及重力平衡优化

New Type of Self-adapting Rehabilitation Exoskeleton and Gravity Balance Optimization

针对上肢运动功能障碍患者,康复外骨骼机构在肩、肘关节康复训练中的应用越来越多,由于盂肱关节的浮动属性及难以避免的穿戴误差,人机对应关节的轴线难以始终保持对齐,致使人-机连接界面处产生较大的附加力/矩,严重影响训练效果及穿戴舒适度。为消除产生的附加力/矩,提出一种4R3P2R型自适应上肢康复外骨骼机构,并对其进行位置逆解及重力平衡优化。该型上肢康复外骨骼在肩、肘关节处采用PPRRRP和PRRR构型,支链PPRRRP与肩关节构成3-DOF恰约束人机闭链。同理,支链PRRR与肘关节构成平面2-DOF的恰约束人机闭链。在该外骨骼构型的基础上,建立人机闭链运动学模型,求其位置逆解,推导出任意位姿下外骨骼重力势能与上肢各关节转角间的函数关系。通过构型分析,可知外骨骼机构的第二主动关节主要完成肩关节前屈/后伸的康复训练,该关节受重力矩影响最为显著,因此,需对该主动关节进行重力平衡。在给定的上肢运动空间内,在外骨骼中添加零初长弹簧单元,以总势能波动最小为目标,建立重力平衡模型,对弹簧参数进行优化分析。进一步,对重力平衡模型进行数值仿真,结果表明零初长弹簧单元对外骨骼机构具有较好的平衡效果。

For patients with the upper limb dyskinesia,the rehabilitation exoskeletons are applied in the rehabilitation training of shoulder and elbow joint.Because of the floating property of the glenohumeral joint and the inevitable wear error,it is difficult to keep the axes of the exoskeleton aligning with human axes in real time.Besides,the additional forces/moments caused in the connection interface reduce the training effect and the wear comfort.To eliminate the additional forces/moments,an adaptive rehabilitation exoskeleton with the configuration 4R3P2R is proposed,and relevant inverse position analysis and the gravity balance optimization are completed for the exoskeleton.The configurations PPRRRP and PRRR are adopted in the exoskeleton for the glenohumeral joint and the elbow joint,respectively.The sub-chain PPRRRP and the glenohumeral joint form a 3-DOF human-machine chain with proper DOFs.Similarly,the sub-chain PRRR and the elbow joint form a plane 2-DOF human-machine chain.Based on the exoskeleton configuration,the kinematics model of the human-machine chain is established and the results of the inverse position are solved.The function relationship between the gravitational potential energy of the exoskeleton and the rotation angles of the upper extremity is derived at the any posture.The configuration analysis shows that the flexion/extension of the glenohumeral joint is driven by the second active joint.The driven torque of this active joint is dominated by the gravities of the rest joints.Hence,the gravity balance should be applied to the second active joint.In the given work space of the upper limb,a zero-free-length spring is added into the exoskeleton.The gravity balance model of the spring is established and the relevant parameters are optimized on account of the minimum change of the total potential energy in the exoskeleton.Furthermore,a numerical simulation of the gravity balance model is completed and the results show that the exoskeleton possesses better balance ability.