Design and energetic evaluation of a prosthetic knee joint actuator with a lockable parallel spring

Area of Science:

• Biomedical Engineering
• Rehabilitation Engineering
• Biomechanics

Background:

• Existing damping knee prostheses lead to asymmetric gait and increased metabolic cost in amputees.
• Current active knee prostheses often require substantial energy and large motors, limiting their practicality.

Purpose of the Study:

• To develop and test a novel semi-active actuator with a lockable parallel spring for prosthetic knee joints.
• To approximate healthy knee behavior during level walking and enhance functional tasks.
• To reduce energy consumption compared to existing active prosthetic knee designs.

Main Methods:

• Development of a novel semi-active actuator with a lockable parallel spring.
• Integration of a series-elastic actuator to cover the full gait cycle and functional tasks.
• Testing of the actuator's performance in approximating healthy knee behavior and energy consumption.

Main Results:

• The novel actuator approximates healthy knee behavior during most of the gait cycle in level walking.
• The actuator, expanded with series-elasticity, enables functional tasks like stair climbing and sit-to-stance.
• Reduced energy consumption was observed compared to compliant or directly-driven active prosthetic knees.
• Improved approximation of healthy knee behavior during level walking compared to passive or variable damping prostheses.

Conclusions:

• The developed semi-active prosthetic knee actuator offers a promising solution for improving amputee gait and reducing metabolic cost.
• The design enhances functional capabilities beyond level walking, including stair negotiation and sit-to-stand transitions.
• This novel actuator represents a significant advancement in prosthetic knee technology, offering improved performance and energy efficiency.