Control System for Non-Gait Ankle Motion in Prostheses
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Solution Overview
Problem
Prosthetic and orthotic devices currently focus primarily on gait-related activities, leaving a gap in effectively managing non-gait movements, which are common in daily life, resulting in unnatural and attention-drawing motions during activities like sitting, standing, dancing, or sporting, as users expend more energy and struggle to appear natural.
Innovation Solution
A control system integrated into active lower limb prostheses, utilizing sensors and actuators to measure and replicate natural kinematic and loading states, allowing for continuous adaptation and control of ankle and foot movements during non-gait activities, mimicking biological motion without an artificial appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If control systems focus primarily on gait-related activities, then gait performance is improved, but non-gait activities appear unnatural and draw attention
Solution Approach 1:
The control system is designed to handle multiple types of activities (gait and non-gait) through a single unified architecture. The system uses sensors to detect user intent and categorize activities, then applies appropriate control strategies for each type, enabling the prosthesis to function naturally across diverse scenarios rather than being optimized solely for gait cycles
Solution Approach 2:
The control system dynamically adapts its behavior based on the detected activity type. During gait activities, it applies gait-optimized control parameters, while during non-gait activities (such as sitting, standing, or dancing), it switches to different control parameters that prioritize natural appearance and user comfort, allowing seamless transition between functional modes
2Ease of operation
If prosthetic devices are designed for natural motion, then appearance is improved, but energy expenditure increases
Solution Approach 1:
The system continuously monitors user motion through sensors and provides real-time feedback control. By detecting actual user intent and comparing it with desired motion trajectories, the control system adjusts actuator commands to achieve natural appearance while minimizing the energy required from the user, creating a closed-loop system that optimizes both aesthetics and efficiency
Solution Approach 2:
The control system dynamically changes operational parameters (such as actuator force, joint stiffness, and motion velocity) based on the detected activity type and user intent. This allows the prosthesis to operate in an energy-efficient manner during gait while switching to parameters that prioritize natural appearance during non-gait activities, optimizing the trade-off between energy consumption and natural motion
3Ease of operation
If control systems use sensors and actuators for continuous adaptation, then natural motion is achieved, but device complexity increases
Solution Approach 1:
The control system is segmented into distinct functional modules: sensor input processing, activity classification, control parameter selection, and actuator output generation. This modular architecture allows each component to be optimized independently and simplifies the overall system design by breaking down the complex control task into manageable stages, making the system more tractable while maintaining natural motion capability
Data Source
AI summary
A human assistance device has a rate gyro, first accelerometer, and second accelerometer disposed on a mobile body for sensing a physical state of the mobile body to provide a physical state measurement. The human assistance device can be a prosthetic, orthotic, and robotic device. An ATAN2 function is performed on an output of the first accelerometer and an output of the second accelerometer. An output of the rate gyro and an output of the ATAN2 function is filtered to provide a filtered physical state measurement. The filtered physical state measurement is applied to a reference function to generate a reference command to control a non-gait motion of an actuator in the human assistance device. The reference command controls the human assistance device, for example to provide a shifting foot position while seated, with a natural, biological motion, without an artificial or mechanical appearance.