Research On Bio-inspired Control Method Of Adaptive Active Lowerlimb Prostheses

Referencing to the research results in biological and neurology fields in recent years, many new ideas are put forward to control the prosthesis. The study find that many movement such as respiratory, gait walking, heartbeat, etc., are not controlled directly by the organism’s brain, instead are controlled directly by the Central Pattern Generator(CPG), which is located in lower nerve center. In this article, the biological control method based on CPG is used to control the prosthesis. The main contents of could be presented as follows:1. By introducing the layered motion control system of human, then the bio-inspired control method based on CPG is make used to the control of lower limb prosthetic, and the self-excited oscillator is used to simulate the signal produced by the neuron, which can be used to control the prosthesis. There are several common oscillator models such as Hopf oscillator, the Rayleigh oscillator and the Matsuoka oscillator. After compared with each other, the Hopf oscillator is selected as the basic unit of the CPG network.2. Because the self-excited Hopf oscillator can only generate the signal with fixed frequency, and cannot adapt to the external training signal, until introduce the Dynamic Hebbian Learning algorithm to the training, in which the frequency of the training signal can be learned based on the change of angular frequency from a constant to a state variable.3. By constructing the CPG network with several improved and self-adapted Hopf oscillators, the coupling model is achieved between the oscillators. Introducing feedback to the CPG oscillatory network can be used to adjust the value of the amplitude, the angular frequency and the phase of the oscillators. The normal lower limb gait information is used to train the oscillatory network. After that, the oscillatory network with the oscillators that have different amplitude, angular frequency and phase, can reproduce the training signal, which can be used to control the AK prosthsis.4. A prosthetic experimental platform was used in Labview to validate the simulation results. The output from CPG controller for AK prosthesis is very close to the joint trajectory of human body. The experiment result prove that use the bionic method based on CPG to control the prosthetic is feasible.