Robust phase-based control of prosthetic feet and biologically inspired joint coupling

人体运动是人体力学、致动器动力学和神经控制系统之间复杂而迷人的相互作用的结果。在下肢丧失的情况下，截肢者遭受其被动假肢的功能降低和有限的发电。为了克服这些局限性，近年来研究者们开发了动力假肢来模拟非截肢者的关节运动，目前的研究表明，动力假肢能够再现人体踝关节在行走和跑步时的自然运动范围和力量。关于假脚的控制，需要进一步研究，以便尽可能多地识别和支持日常生活活动。基于相位的控制被认为是用于动力假肢脚的特别鲁棒的控制方法。它们依赖于人类运动的不变轨迹，从中推导出用户状态和步态相位之间的可逆关系。然后可以使用步态相位来计算致动器的参考信号。因此，基于相位的方法可以对不规则运动和变化的步态参数做出反应。存在用于站立、水平行走和跑步的动力假脚的基于相位的方法。本研究项目的第一个目的是开发一种基于相位的控制器，包括站立和水平行走以及爬楼梯和这些运动类型之间的安全过渡。在装有仪器的楼梯上进行的人体实验将为设想中的步行者提供所需的输入数据。最近对BiOM假足的研究表明，尽管踝关节得到了改善，但近端关节的应力增加和不对称性仍然存在。作者认为，由于器械的单关节（单关节），使用主动足不可能恢复正常步态运动学和动力学。双关节耦合存在于人类通过腓肠肌，但没有考虑到在目前的假肢脚的实施。因此，除了基于相位的控制，这个项目的第二个目的是设计一个新的仿生启发假肢的原型，其中，除了单关节比目鱼肌，还具有双关节腓肠肌的功能。与现有的单关节假体相比，该概念更符合生物腿。新原型应用于获得水平行走的最佳步态。因此，只有恒定速度的实验将被考虑，重点将放在确定和应用的最佳致动器的力量。

Human locomotion is the outcome of a complex and fascinating interaction between body mechanics, actuator dynamics and the neural control system. In the case of lower limb loss, amputees suffer from reduced functionality and limited power generation of their passive prosthetic limbs. To overcome such limitations, in recent years, researchers have developed powered prostheses to emulate the joint motions similar to non-amputees.Current studies show that powered prosthetic can reproduce natural human ankle range of motion and power in walking and running. Regarding the control of prosthetic feet further research is necessary in order to recognize and support as many activities of daily living as possible. Phase-based controls are considered particularly robust control approaches for powered prosthetic feet. They rely on invariant trajectories of human locomotion, from which an invertible relation between the user`s states and gait phase is derived. The gait phase can then be used to compute reference signals for the actuators. Hence phase-based approaches can react on irregular movements and changing gait parameters. Phase-based approaches for powered prosthetic feet exist for standing, level walking and running. The first aim of this research project is the development of a phase-based controller which includes standing and level walking as well as stair climbing and safe transitions between these motion types. Human experiments on an instrumented stairway will provide the required input data for the envisioned controller.A recent study with the BiOM prosthetic foot shows that, despite improvements in the ankle, increased stress and asymmetry remain in proximal joints. The authors argue that the restoration of normal gait kinematics and kinetics was not possible using the active foot due to the uni-articulation (mono-articulation) of the device. Bi-articular coupling exists for humans through the gastrocnemius muscle, but is not taken into account in the implementation of current prosthetic feet.Thus, in addition to the phase-based control, the second aim of this project is to design a prototype for a new bionically inspired prosthesis, which, in addition to the mono-articular soleus muscle, also features the function of the biarticular gastrocnemius muscle. The concept is more consistent with the biological leg than existing monoarticular prostheses. The new prototype shall be used to obtain optimal gait for level walking. Therefore, only experiments with constant speeds will be considered and focus will be placed on determination and application of optimal actuator forces.