Adaptive Damping Control for Artificial Knee Joints
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Solution Overview
Problem
Existing methods for controlling the swing phase in artificial knee joints of orthoses, exoskeletons, and prostheses are inadequate for varying gait situations and speeds, often leading to premature reduction in flexion resistance and potential joint collapse, especially during slow walking.
Innovation Solution
A method that captures the load characteristic profile during stance phase, reducing flexion damping only after reaching the maximum load characteristic value, allowing adaptive swing phase triggering based on the load characteristic profile, eliminating the need for assumed step duration estimates and enabling flexible response to different gait patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If flexion resistance is reduced based on assumed step duration to trigger swing phase, then swing phase can be initiated, but premature reduction occurs during slow walking leading to joint collapse
Solution Approach 1:
The control unit continuously monitors the load characteristic profile from force sensors during the stance phase and uses this real-time feedback to determine when to reduce flexion resistance. Instead of relying on predetermined time intervals, the system waits for the actual load characteristic to reach its maximum value and then decline, ensuring the swing phase is triggered at the correct moment regardless of walking speed. This feedback mechanism prevents premature resistance reduction and joint collapse during slow walking.
Solution Approach 2:
The system dynamically adjusts the swing phase triggering criterion based on the actual load characteristic profile observed during each stance phase. By making the triggering condition adaptive rather than fixed, the system can accommodate varying walking speeds and gait patterns. The flexion resistance reduction is timed to the actual mechanical events (load maximum and decline) rather than a predetermined time schedule, making the system dynamic and responsive to real-time conditions.
2Device complexity
If standard step duration is used for swing phase triggering, then control is simplified, but it cannot adapt to varying gait speeds and situations
Solution Approach 1:
The control system uses the natural mechanical signature of the gait cycle itself (the load characteristic profile generated by the user's walking) to determine swing phase timing. Instead of requiring external input or complex algorithms to estimate gait parameters, the system lets the user's own movement pattern provide the triggering signal. The load characteristic naturally reaches a maximum and then declines during normal walking, and this self-generated signal is used to time the resistance reduction, making the system adaptive without adding significant complexity.
3Duration of action of moving object
If flexion resistance is reduced early during stance phase, then swing phase preparation begins, but unwanted flexion occurs and joint collapses
Solution Approach 1:
The control system prepares for swing phase by monitoring the load characteristic profile throughout the stance phase, but delays the actual resistance reduction until the load characteristic reaches its maximum and begins to decline. This preliminary monitoring without immediate action ensures that the joint remains stable during the critical period when load is increasing. The system is ready to trigger swing phase but waits for the optimal moment (after load maximum) to reduce resistance, preventing premature flexion and joint collapse while still preparing for the transition.
Data Source
AI summary
A method for controlling a damping modification in an artificial knee joint of an orthosis, an exoskeleton, or a prosthesis. The artificial knee joint has an upper part pivotally connected to a lower part. A resistance unit is secured between the upper part and the lower part in order to provide a resistance against a flexion or extension. The resistance unit is paired with an adjustment device to modify the resistance when a sensor signal of a control unit paired with the adjustment device activates the adjustment device. The flexion resistance is reduced for the swing phase. A curve of at least one load characteristic is detected when walking or standing; a maximum of the load characteristic curve when standing is ascertained; and the flexion damping is reduced to a swing-phase damping level during the standing phase when a threshold of the load characteristic below a maximum is reached.