Joint Torque Augmentation via Compliant Actuator
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Solution Overview
Problem
Current load assistance structures disrupt users' gait, increasing metabolic cost and the likelihood of acute and chronic injuries, particularly in military personnel carrying heavy loads, due to interference with natural gait dynamics.
Innovation Solution
A wearable joint torque augmentation system that includes a linkage assembly, an actuator, and a sensor to provide torque assistance at specific phases of the gait cycle, allowing for unencumbered movement and reducing metabolic expenditure by applying forces during swing and stance phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If load assistance structures are used to support heavy loads, then the metabolic cost of gait is reduced, but the structures perturb the user's gait and interfere with natural gait dynamics
Solution Approach 1:
The patent introduces a compliant element (spring) as an intermediary between the actuator and the user's limb. This compliant element mediates the interaction by storing and releasing energy in phase with the gait cycle, providing assistance without disrupting the natural dynamics of movement. The spring acts as a buffer that adapts to the user's motion patterns.
Solution Approach 2:
The system dynamically adjusts the stiffness and damping parameters of the compliant element to match the user's gait characteristics. By changing these parameters in real-time, the system optimizes the balance between providing mechanical assistance and maintaining natural gait dynamics, resolving the contradiction between energy reduction and movement naturalness.
2Stability of the object's composition
If rigid support structures are used to carry loads, then stability is improved, but the structures increase metabolic expenditure by disrupting gait fluidity
Solution Approach 1:
The patent transitions from static rigid support structures to dynamic compliant structures that adapt to the user's movements. The compliant element with adjustable stiffness and damping allows the system to maintain stability while moving, rather than resisting movement. This dynamic approach reduces the metabolic cost by working with the user's gait rather than against it.
Solution Approach 2:
The system changes the mechanical parameters (stiffness, damping) of the support structure based on the phase of the gait cycle and user requirements. During stance phase, the structure provides rigid support for stability; during swing phase, it becomes more compliant to allow natural movement. This parameter modulation resolves the contradiction between stability and energy efficiency.
3Productivity
If active control systems are added to adjust support forces, then gait efficiency is improved, but the device complexity increases
Solution Approach 1:
The patent implements feedback control by sensing the user's gait parameters (velocity, acceleration, phase) and using this information to adjust the actuator output and compliant element characteristics. This feedback loop enables the system to optimize gait efficiency by providing precisely timed and sized assistance forces.
Solution Approach 2:
The compliant element with passive spring-damper characteristics provides self-regulating behavior that reduces the burden on the active control system. The passive elements automatically adapt to certain aspects of the user's movement, reducing the computational and control complexity while maintaining gait efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system reduces metabolic cost by up to 15% and enhances gait efficiency, minimizing fatigue and injury risk by providing assistive torque at optimal times, thus enabling longer distances with reduced energy expenditure.
Implementation Method 1
coupling a compliant element to the actuator
Data Source
AI summary
A joint torque augmentation system includes linkage assembly configured to couple to a user. Linkage assembly includes a unidirectional link and a device joint. The linkage assembly is worn by a user or is configured to couple to footwear. An actuator is coupled to the linkage assembly to provide a torque at a joint of the user. A sensor is coupled to the user to measure a position of the user. A control system is coupled to the sensor and actuator. A phase of gait for the user is determined by the control system based on the position measured by the sensor. The actuator produces a tension force on the linkage assembly during a first phase of gait. A compliant element is coupled between the actuator and linkage assembly. The compliant element is tuned based on a load carried by the user.