Intelligent prosthetic ankle based on the finite state machine control

doi:10.3969/j.issn.2095-4344.2013.09.005

Abstract

Abstract:

BACKGROUND: At present, intelligent prosthesis only focuses on the function of knee joint, while ankle joint prosthesis is only used as the aid of prosthetic knee joint. So the normal gait cannot be realized according to the change of external environment and gait.
OBJECTIVE: To develop a reliable intelligent prosthetic ankle in order to improve the gait of amputees effectively.
METHODS: Based on the variable damping ankle-foot prosthesis, the control method of finite state machine was proposed. The ankle joint gait was planned in detail, and the relevant control strategy was developed.
RESULTS AND CONCLUSION: Results indicate that the intelligent prosthetic ankle based on the finite state machine control can effectively follow health limb lateral movement, and can adapt to different paces, which lays an experimental basement for later knee ankle coordinated movement.

Key words: bone and joint implants, artificial prosthesis, intelligent prosthesis, knee joint, finite state machine, intelligent controller, gait, amputation, prosthetic ankle-foot, knee and ankle movement, digital, intelligent, other grants-supported paper, photographs-containing paper of bone and joint implants

CLC Number:

R318

Yang Peng, Bai Jian, Wang Xin-ran, Geng Yan-li. Intelligent prosthetic ankle based on the finite state machine control[J]. Chinese Journal of Tissue Engineering Research, 2013, 17(9): 1549-1554.

Figures/Tables 9

跖屈控制相：开始于足跟接触地面，至脚底完全接触地面(即足平)结束，这一过程踝关节主要起到缓冲作用。背屈控制相：开始于跖屈控制相的末端，到踝关节最大背屈状态(即足跟即将离地时刻)结束。踝关节在背屈控制相阶段的主要作用是为下一相位提供身体向前向上的动力储存弹性能量。跖屈动力相：开始于背屈控制相的末端，到脚尖离地时结束。跖屈动力相阶段释放了踝关节作为扭矩源在背屈控制相阶段储存的能量，为人体前行提供动力。摆动相：开始于脚尖离地，到同侧足跟再次触地时结束。这一阶段踝关节使脚达到平衡状态，为足跟触地做好准备。 2.2 有限状态机控制方法有限状态机是表示有限个状态以及在这些状态之间的转移和动作的数学模型。有限状态机的下一个状态是确定的。系统状态的改变取决于系统的输入和当前系统的状态。采用有限状态机进行步态控制的前提是神经运动系统以某种固定的方式来运转。这在下肢行走方面影响不大，下肢受伤或部分残缺不会影响步行习惯的改变[20-21]。人体行走时具有重复运动的特性，即脚跟着地到同侧脚尖离地的支撑相约占整个步态周期的60%，脚尖离地到同侧脚跟着地的摆动相约占步态周期的40%，因此可将人体步态进行详细划分，利用有限状态机(FSM)的控制方法，在不同的运动阶段采用不同的控制策略。将踝关节的步态进行详细规划，典型事件包括：HC表示足跟着地，FF表示脚与地面完全接触(即足平)，TV表示小腿与地面垂直，MD表示最大背屈，TO表示足尖离地。典型步行状态包括：CP表示跖屈控制相，ECD表示背屈控制相前期，LCD表示背屈控制相后期，PP表示跖屈动力相，SW表示摆动相。有限状态机由变换函数和动作函数实现，变换函数为："

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