Active Ankle Prosthesis with Gear Motor for Gait Adaptation
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Solution Overview
Problem
Existing prostheses for above-knee amputees face challenges such as stumbling due to inadequate toe clearance, difficulty in realigning the tibia with the femur, inability to adjust gait speed, and issues with energy efficiency and posture mimicry, leading to increased metabolic consumption and potential orthopedic problems.
Innovation Solution
A prosthesis with an ankle joint featuring a gear motor and microprocessor-controlled actuator, position transducers, and n-dimensional curves that replicate natural gait cycles, allowing for dynamic damping, energy recovery, and adaptive stiffness, enabling improved toe clearance, gait speed adjustment, and natural posture mimicry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a passive ankle joint with stiff articulation is used, then the prosthesis structure is simple, but toe clearance is insufficient causing stumbling
Solution Approach 1:
The ankle joint transitions from a passive stiff structure to an actively controlled dynamic system. The actuator adjusts the ankle angle in real-time during the gait cycle, enabling the foot to clear the ground during swing phase while maintaining stability during stance phase, thus resolving the contradiction between structural simplicity and toe clearance reliability.
2Device complexity
If a passive ankle joint is used, then the prosthesis is simpler, but natural gait reproduction and posture mimicry are insufficient
Solution Approach 1:
The control system uses feedback from sensors detecting gait phase and ground contact to dynamically adjust the ankle joint angle. This feedback mechanism enables the prosthesis to reproduce natural gait patterns and adapt to different walking conditions, resolving the contradiction between structural simplicity and gait adaptability.
Solution Approach 2:
The ankle joint angle parameter is dynamically changed based on gait phase and walking conditions. The actuator adjusts this parameter to match natural human gait characteristics, enabling the prosthesis to adapt to various terrains and speeds while maintaining a relatively simple overall structure.
3Use of energy by moving object
If no active control is provided, then energy consumption is lower, but gait speed adjustment and response to obstacles are impossible
Solution Approach 1:
The actuator provides active control only during critical phases of the gait cycle where adjustment is needed, such as swing phase for toe clearance and transition phases for speed adaptation. This partial action approach enables gait speed adjustment and obstacle response while minimizing energy consumption compared to continuous active control.
Data Source
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AI summary
A prosthesis for lower- limb amputees comprises a foot segment (10) and a tibial segment (12) pivotally connected to each other about an articulation axis (17) that perform an ankle joint (13) of a leg/foot prosthesis. The leg- foot prosthesis comprises a gear motor (70) whose axis coincides with the axis (202) of the tibia (12).The gear motor (70) can be associated with a microprocessor (70 ') that is adapted to control the movement of the ankle joint (13).A position transducer (17a) provides a position signal to program means residing in the microprocessor (70 ') that calculate the relative angular speed of the foot (10) with respect to the tibia (12) and generate two-dimensional position - angular speed curves that reproduce the gait cycle. The microprocessor causes the gear motor to belong to one of the curves for characterizing a predetermined gait or posture condition.