The aim of this project is to attempt to resolve problem of stair climbing for above-knee amputees by developing a new type of intelligent prosthesis. By resolving the stair climbing problem, many other problems that the amputees are facing in everyday life (e.g.: stepping over any obstacle) would be resolved at the same time.
The basic idea of our project is to incorporate additional linear initiators into an existing prosthesis. It is intended that such initiators, by using the power from an outside source, support a disabled person during stair climbing.
The biggest problem for above–knee amputees is lack of their own knee, including the lack of muscles that enable climbing. The forces normally generated in the knee during climbing are among the largest exerted in the human body. That is the reason why outside power source is necessary.
This work is intending to define a hydraulic system and an appropriate control system with an independent source of power supply.
Existing above-knee prosthesis has only one DOF (degree of freedom). Mechanism of a new type of above - knee prosthesis will have two DOF. It will have rotation in the knee and rotation in the ankle. Optimal actuators for that type of mechanism will be hydraulic linear actuators. It will be possible by two hydraulic linear initiators (one in the knee and other in the ankle). Figure shows the principal of design mechanism of this type of prosthesis.
Mechanism of the new above - knee prosthesis will move continuously, without impacts. Speed of moving will be adjustable. It will be safe in all positions. Hydraulic component for this stage of research would be standard components currently available on the market.
The next step will be optimization of hydraulic and control systems with two linear hydraulic initiators and with mobile power supply. Hydraulic system must include appropriate control system and regulative elements for directing fluid as well as its distribution towards hydraulic actuators.
Requirements for control system:
• to collect data of the flexion and extension angles at the knee and ankle
• to identify a force/pressure during the contact a prosthesis has with the ground
• to predict the leg motion/gait during the stairs climbing based on the sensors input
Sensors interact with physical variables in their environments and produce signals that represent the states of those variables. The result generally is given in terms of a varying voltage, resistance, inductance or capacitance. Sensor measurement is essential since the control can be only as good as the accuracy of the signal we measure.
Development, testing and implementation of a power prosthesis control system would include the following:
• Selection of sensors to report the angles at the knee and ankle;
• Selection of force sensors to report the contact with the ground and confirm the gait phase;
• Develop the simulation software to predict the leg motion and gait cycle during the stair climbing based on the sensors input.