Controlling Powered Prosthesis Joint Impedance Over Continuous Stance Transitions Between Walking and Stair...

Area of Science:

• Biomedical Engineering
• Robotics
• Biomechanics

Background:

• Level-ground walking and stair negotiation are crucial for daily mobility.
• Transfemoral amputees often face challenges performing continuous transitions with passive prostheses.
• Existing powered prostheses use discrete control, not mimicking continuous joint biomechanics.

Purpose of the Study:

• To develop and evaluate a phase-based hybrid kinematic impedance controller for seamless transitions between walking and stairs.
• To enable transfemoral amputees to perform continuous transitions with powered prostheses.
• To provide biologically-inspired knee and ankle impedance during these transitions.

Main Methods:

• A phase-based hybrid kinematic impedance controller was designed.
• An offline analysis with 12 participants compared the new controller to discrete switching strategies.
• Pilot experiments were conducted with two K4 transfemoral amputee participants using a powered knee-ankle prosthesis.

Main Results:

• The continuous stance transition modeling approach significantly outperformed discrete switching strategies in offline analysis.
• Experimental implementation used a common thigh-based phase variable for user control.
• Pilot studies demonstrated biomimetic kinematic/kinetic features during stair transitions without subject-specific tuning.

Conclusions:

• The proposed controller facilitates continuous, biologically-inspired stance-phase transitions for transfemoral amputees.
• This approach enhances mobility by allowing smoother integration of level-ground walking and stair locomotion.
• The controller shows promise for improving the functionality of powered prosthetic limbs.