Parallel Mechanism Prosthetic Joint with Compliant Actuation
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Solution Overview
Problem
Current prosthetic and orthotic devices are limited in their ability to mimic human muscle performance across a wide range of activities, with passive devices providing insufficient energy return and active devices being inefficient due to large motors or low peak power output, and are often restricted to specific activities.
Innovation Solution
The development of active compliant parallel mechanisms that couple springs and motors in a parallel kinematically redundant arrangement to create prosthetic joints that behave more like human muscles, allowing for a change in geometry based on load to optimize force and torque output across various activities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If passive spring-based mechanisms are used, then energy storage and return is achieved, but the energy return is limited to only what is put in by the user
Solution Approach 1:
The patent combines active motors with passive spring mechanisms in a hybrid parallel mechanism. The motor and spring work together in parallel to provide both active power input and passive energy storage/return, enabling the system to deliver peak power output exceeding what the spring alone could return while maintaining energy efficiency through the spring's passive contribution.
2Power
If active motors are used to increase power output, then peak power is improved, but device weight and complexity increase
Solution Approach 1:
The patent employs a parallel mechanism where the motor and spring dynamically share the power delivery task. The system can operate in different modes: the spring provides passive energy return during deceleration phases, reducing motor workload, while the motor provides active power during acceleration phases. This dynamic load sharing reduces the peak power requirement of the motor itself, allowing for a smaller, lighter motor while achieving high overall peak power output.
3Stability of the object's composition
If traditional rigid structures are used, then structural stability is maintained, but adaptability to different activities is limited
Solution Approach 1:
The patent utilizes a parallel mechanism with compliant elements that allow the structural parameters (stiffness, geometry) to change dynamically based on loading conditions and desired activity. The spring-motor parallel arrangement enables the system to adjust its effective stiffness and power delivery characteristics adaptively, providing stable support during weight-bearing activities while enabling high-speed motion during locomotion phases, thus achieving both stability and activity adaptability.
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
This solution enables prosthetic devices to achieve a higher range of force and speed output, reduce metabolic energy expenditure, and provide improved gait performance across different activities, including high velocities under low load and low velocities under high load, while maintaining a lightweight and efficient design.
Implementation Method 1
A spring is able to return only as much energy as is put into the spring
Data Source
AI summary
A parallel kinematically redundant device includes a base body portion and a movable portion. The movable portion includes first, second, and third joints. A first actuator is coupled to the first joint of the movable portion and to the base body portion. A second actuator is coupled in parallel with the first actuator between the second joint of the movable portion and the base body portion. A linking member is rotationally coupled to the third joint of the movable portion to provide an output for the first and second actuators. A housing is coupled to the base body portion and fits onto a user. A prosthetic joint device includes a base portion and a movable portion. An actuator is rotationally coupled to the movable portion and base portion. A compliant element is coupled in parallel with the actuator between the movable portion and base portion.