Powered Knee Prosthesis Control Across Stairs and Uneven Terrain
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Solution Overview
Problem
Conventional passive prostheses are slow, inefficient, and unstable, particularly when navigating environmental barriers like ramps, stairs, and uneven terrain, limiting mobility and independence for individuals with above-knee amputations.
Innovation Solution
A unified volitional controller for powered knee prostheses that adapts to walking, stair ascent, and stair descent without explicit activity classification, using sensors to continuously adjust the prosthesis behavior based on user movements and ground interaction, incorporating a finite-state machine to determine contact states and calculate target knee torque through biarticular and damping torques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional passive prostheses are used, then the device structure is simple, but the ambulation speed and efficiency are slow and inefficient
Solution Approach 1:
The patent replaces passive mechanical prosthetic structures with an active powered system that uses electrical motors to generate knee joint torque. The controller system substitutes simple mechanical linkages with electronic control architecture that processes sensor data and generates actuation signals, enabling active compensation for gravitational and inertial forces to improve ambulation speed and efficiency.
Solution Approach 2:
The patent dynamically changes the torque parameter at the knee joint based on real-time sensor measurements of thigh orientation, knee orientation, and knee velocity. The controller adjusts the magnitude and direction of knee torque continuously during the gait cycle, transitioning from fixed mechanical properties to variable active control parameters that adapt to different phases of movement.
2Reliability
If conventional passive prostheses are used, then the device is easy to operate, but the stability is poor, particularly when navigating environmental barriers
Solution Approach 1:
The patent implements a closed-loop feedback control system that continuously measures thigh orientation, knee orientation, and knee velocity using sensors, compares these measurements to desired values, and adjusts the knee joint torque accordingly. This feedback mechanism provides active stabilization during ambulation and when navigating environmental barriers such as ramps and stairs.
Solution Approach 2:
The patent transitions from static passive mechanical structures to dynamic active control that continuously adapts to changing conditions. The controller modifies knee torque in real-time based on measured state variables, enabling the prosthesis to actively respond to environmental barriers and maintain stability during complex movements like stair climbing or walking on uneven terrain.
3Adaptability or versatility
If activity-specific controllers are used for different ambulation activities, then the control precision for each activity is improved, but the device complexity and switching requirements increase
Solution Approach 1:
The patent implements a single universal controller that handles all ambulation activities including level walking, stair ascent, and stair descent without requiring activity classification or controller switching. The controller uses the same feedback control algorithm with torque equations that adapt to different activities based on real-time sensor measurements of thigh orientation, knee orientation, and knee velocity, eliminating the need for multiple specialized controllers.
Data Source
AI summary
Disclosed are prosthetic systems comprising a powered knee prosthesis and a volitional controller configured to provide control of the prosthesis to the user. The prosthetic system may be configured to enable a user to walk on smooth and/or uneven terrain and to ascend and/or descend stairs. The volitional controller may be configured in a contact state when the prosthesis is in contact with a ground surface and a no contact state when the prosthesis is lifted from the ground surface. When in the contact state, the controller may output a knee torque signal for controlling the powered knee of the prosthesis. The knee torque signal may be based on a target knee torque determined by the knee orientation and the torque measured at the ankle of a prosthetic foot. When in the no contact state, the controller may output a knee torque signal based on a desired knee position.