Powered Prosthesis Running Control With Absorption-Propulsion Gait
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Solution Overview
Problem
Existing lower limb prostheses, both passive and powered, fail to replicate the biomechanics of healthy running, particularly in transfemoral amputees, due to the inability to generate net positive power at both the knee and ankle joints, and lack of a double float phase during running.
Innovation Solution
A control algorithm for powered lower limb devices, incorporating a powered knee and ankle joint, that transitions between absorption and propulsion states based on real-time sensor information, using a finite state model to emulate healthy running gait, including passive impedance during absorption and power generation during propulsion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive prostheses are used, then device complexity is reduced, but the ability to generate net positive power at knee and ankle joints is lost
Solution Approach 1:
The prosthesis is divided into functionally independent powered knee and ankle joints, each capable of independent power generation and control. This segmentation allows each joint to be optimized for its specific biomechanical function while maintaining overall system manageability despite the added complexity of active power generation.
Solution Approach 2:
The prosthesis transitions from a static passive structure to a dynamic active system with real-time power generation at both knee and ankle joints. The powered joints dynamically adjust power output based on gait phase detection and biomechanical requirements, enabling the device to adapt to varying running conditions and replicate healthy gait patterns.
2Reliability
If powered knee and ankle joints are incorporated, then biomechanically healthy running gait is restored, but device complexity increases
Solution Approach 1:
The powered knee and ankle joints are integrated into a unified control system that manages both joints simultaneously. The finite state machine controller coordinates power delivery across both joints based on detected gait phase, enabling complex running biomechanics to be achieved through coordinated action of multiple powered components rather than treating them as separate systems.
Solution Approach 2:
The control system continuously monitors gait phase and biomechanical parameters through sensors, using this feedback to dynamically adjust power generation at both knee and ankle joints. This closed-loop control ensures that the powered prosthesis accurately replicates healthy running gait characteristics by responding to real-time mechanical conditions and transitioning between absorption and propulsion states as needed.
3Productivity
If real-time sensor information and finite state model are used for control, then transition between absorption and propulsion states is optimized, but control system complexity increases
Solution Approach 1:
The control system uses a finite state machine that periodically transitions between defined gait states (absorption and propulsion) based on detected biomechanical events. This periodic state-based control approach simplifies the management of complex power generation requirements by breaking the continuous control problem into discrete, repeating gait cycle phases with predetermined power delivery patterns.
Solution Approach 2:
The control algorithm dynamically changes power generation parameters at the powered joints based on detected gait phase and biomechanical conditions. During absorption states, the powered joints operate in energy-dissipating mode, while during propulsion states, they switch to power-generating mode. This parameter switching between operational modes optimizes gait efficiency without requiring continuously complex control calculations.
Data Source
AI summary
Systems and methods for a running controller for a lower limb device including at least a powered knee joint are provided. The method includes collecting real-time sensor information for the lower limb device and configuring the lower limb device to a first state in a finite state model for an activity mode including the running mode. The method further includes, based on the sensor information, transitioning the lower limb device from a current state to a subsequent state in the finite state model for the detected mode when a pre-defined criteria for transitioning to the subsequent state is met, and repeating the transitioning until the activity mode changes. In the system and method, the finite state model includes at least one stance state and at least one swing state, where the at least one stance state includes at least one absorption state and at least one propulsion state.