基于踝后足四关节时空力偶联机制的智能辅具仿生优化研究

The function of ankle hindfoot joints is exquisite and complicated during the human gait cycle. Currently, the foot and ankle intelligent assistive devices mainly control the dorsi/plantar flexion movement and still not bionic enough since they can't fit for the unaffected limb and achieve accurate motion servo. Therefore, pain and fatigue are commonly seen in the users. Through the previous work, we have improve the gait simulation technique and the dynamic image matching technique, and have found the spatial motion coupling mechanism of ankle hindfoot joints during gait. We found the ankle hindfoot joints are the most important structure serve for the kinematic function of foot and ankle and are the essential part to achieve high-precision bionic ankle. Based on these high-precision biomechanical techniques, the present project aiming to obtain the time-space force coupling data of the ankle hindfoot joints and surrounding tendons under different walking conditions as well as the joint damping coefficients of each joint. We will illustrate the correspondence between the kinematic mechanism and the kinetic mechanism of the ankle hindfoot joints. The nine groups of tendon forces around the ankle will be vectorized, and further be simplified to three vector directions. Based on these researches, we can create the optimized bionic model of foot and ankle which can also simulated human gait in six degree of freedom. Based on the optimized bionic model, we will modified the current ankle intelligent assistive device prototype, and verified its biomechanical validity. The researches of current project can further add coupling data of ankle hindfoot joints kinematics and tendon forces and provide clinical guidance to the surgery of ankle and hindfoot fusion as well as the tendon transfer. The establishment of optimized bionic model is the crucial basis for the high-precision bionic designs in future assistive devices of the foot and ankle.

踝后足四关节在人体步态中的运动非常精细复杂。目前足踝辅具基本都是背伸和跖屈的被动活动，不能实现运动精确伺服，更不能与健侧匹配。不符合人体生物力学特性的仿生容易导致疲劳和疼痛。我们前期优化了步态仿真技术及动态图像匹配技术，发现踝后足四关节在步态过程中存在空间运动偶联，是维持足踝部运动功能的最重要结构，是高精度仿生的关键。本项目基于前期优化的小关节运动与生物力学检测技术，获取不同工况步态环境下踝后足四关节每个骨块、每根肌腱的时间、空间和受力偶联数据及关节阻尼系数变化，将踝后足四关节各关节运动轴进行简化归并；将足踝部9组肌腱力矢量化，简化归并至3个矢量方向，建立能够实现六自由度步态仿真的足踝仿生模型；基于该优化模型改进目前足踝智能辅具并验证其生物力学有效性。研究内容可以丰富踝后足四关节及肌腱力的偶联数据，为足踝手术关节融合取舍、肌腱转位等提供优化方案，为具有简便性的高精度智能辅具仿生提供可能。

踝后足四关节在人体步态中的运动非常精细复杂。目前足踝辅具基本都是背伸和跖屈的被动活动，不能实现运动精确伺服，更不能与健侧匹配。不符合人体生物力学特性的仿生容易导致疲劳和疼痛。我们前期优化了步态仿真技术及动态图像匹配技术，发现踝后足四关节在步态过程中存在空间运动偶联，是维持足踝部运动功能的最重要结构，是高精度仿生的关键。本项目基于前期优化的小关节运动与生物力学检测技术，及足踝部双平面透视匹配技术，将该技术的精度进一步提高至0.3°及0.2mm以内。应用该技术我们首先获取了正常步态、上下楼梯、斜坡行走等不同日常工况下踝足四关节三维运动数据，分析了踝足四关节在空间各个运动方向上的联动关系，发现后足三关节之间存在着同步、同向性旋转，打破了传统观念所认为的中足关节反向运动锁定机制。本项目将运动学及表观力学数据导入Anybody计算机肌骨模型软件中进行逆向动力学分析，将足踝部9组肌腱力矢量化，简化归并至3个矢量方向，并通过图表反映了3足模拟矢量肌腱在足跟触底、全足着地及推理过程中均存在贯序收缩及拮抗收缩的力学机制。本项目进一步建立了足踝部高仿真有限元模型，将上述研究所获得的瞬时肌腱力导入有限元模型中，实现了通过对模型进行模拟驱动，进一步分析了简化肌腱驱动踝足模型的瞬时内部受力机制，阐述了踝足关节在步态过程中的关节阻尼系数变化规律，改模型也为后续智能辅具开发提供了基础。通过项目组前期开发的四维六自由度尸体足步态模拟系统，实现了通过控制四组肌腱，即胫前肌腱、胫后肌腱、腓骨肌腱及跟腱的贯序拮抗收缩模拟正常步态，验证了上述简化模型的正确性。基于该优化模型设计了足踝部智能假肢样机系统，已实现了通过简化模型数据进行假肢样机系统的仿生运动控制。本项目研究内容可以丰富踝后足四关节及肌腱力的偶联数据，为足踝手术关节融合取舍、肌腱转位等提供优化方案，为具有简便性的高精度智能辅具仿生提供可能。