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，被截肢者的被动假肢功能下降，发电有限。为了克服这些限制，近年来，研究人员开发了动力假肢来模拟类似于非截肢者的关节运动。目前的研究表明，动力假肢可以再现人类踝关节的自然运动范围和行走和跑步的力量。关于假肢脚的控制，有必要进一步研究，以识别和支持尽可能多的日常生活活动。相位控制被认为是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。步态相位可以用来计算执行器的参考信号。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。基于阶段的动力假肢脚存在于站立、水平行走和跑步中。本研究项目的第一个目标是开发一种基于阶段的控制器，该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转换。在仪表楼梯上的人体实验将为设想的控制器提供所需的输入数据。BiOM假肢脚最近的一项研究表明，尽管脚踝有所改善，但近端关节的压力和不对称仍然增加。作者认为，由于该装置的单关节（single -articulation），使用活动足不可能恢复正常的步态运动学和动力学。人类通过腓肠肌存在双关节耦合，但在目前的假肢脚实施中没有考虑到这一点。因此，除了基于相位的控制，这个项目的第二个目标是设计一个新的仿生仿生假体的原型，除了单关节比目鱼肌外，还具有双关节腓肠肌的功能。这个概念比现有的单关节假肢更符合生物腿。新的原型应使用，以获得最佳的步态水平行走。因此，只考虑恒速实验，并将重点放在最优执行器力的确定和应用上。

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.