Agonist-Antagonist Artificial Joints with Series Elasticity
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Solution Overview
Problem
Current prosthetic and robotic joint systems fail to efficiently mimic the adaptive stiffness, damping, and nonconservative motive power of biological joints, leading to limited operational time, high power consumption, and inadequate energy addition during movement.
Innovation Solution
The development of an agonist-antagonist actuator design incorporating series elastic structures and active elements, which allows for independent control of joint position, stiffness, and energy storage and release, mimicking the behavior of biological joints through the use of motors, springs, and variable dampers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional actuators are used in prosthetic and robotic joint systems, then the system can provide motive power, but the power consumption is high and operational time is limited
Solution Approach 1:
The patent employs periodic action by utilizing the natural oscillatory motion of walking gait to drive the energy storage and release mechanism. The spring-based system stores energy during the stance phase and releases it during the swing phase, synchronizing with the periodic nature of human locomotion to minimize active power consumption while extending operational time
Solution Approach 2:
The system implements self-service through passive energy storage and release mechanisms that automatically regulate joint stiffness and damping without requiring continuous active control. The spring elements and friction-based dampers provide adaptive mechanical assistance that reduces the power burden on active actuators, enabling the system to sustain operation for extended periods
2Power
If traditional actuators are used in prosthetic and robotic joint systems, then the system can provide motive power, but the weight increases and power efficiency decreases
Solution Approach 1:
The patent replaces traditional high-power electric actuators with a hybrid mechanical system comprising springs, friction dampers, and passive elements. This mechanical substitution provides the necessary motive power through elastic energy storage and friction-based damping, significantly reducing system weight while maintaining adequate power output for prosthetic and robotic applications
Solution Approach 2:
The system utilizes parameter changes by varying the mechanical properties of spring elements and friction dampers to adapt joint stiffness and damping characteristics. This allows the lightweight mechanical system to provide variable motive power output suitable for different gait conditions and terrain requirements without increasing overall system weight
3Adaptability or versatility
If traditional actuators are used in prosthetic and robotic joint systems, then the system can provide motion control, but the adaptive stiffness and damping capability is insufficient
Solution Approach 1:
The patent implements self-service through passive adaptive mechanisms where spring elements automatically adjust joint stiffness based on loading conditions, and friction dampers provide velocity-dependent damping without active control. This self-adjusting behavior enables the system to adapt to varying gait conditions and terrain while maintaining relatively simple device architecture
Solution Approach 2:
The system achieves adaptive stiffness and damping through parameter changes in mechanical components - spring stiffness varies with compression, and friction damper characteristics change with velocity and normal force. These passive parameter variations provide biologically realistic joint behavior without requiring complex active control systems
4Loss of energy
If traditional actuators are used in prosthetic and robotic joint systems, then the system can provide motion, but the ability to store and release energy efficiently is limited
Solution Approach 1:
The patent employs periodic action by synchronizing energy storage in spring elements with the stance phase of gait and energy release with the swing phase. This periodic energy management recovers and reuses mechanical energy throughout the gait cycle, minimizing energy loss and improving overall energy efficiency of the prosthetic or robotic system
Solution Approach 2:
The system converts harmful energy losses into beneficial stored energy by capturing kinetic energy that would otherwise be dissipated during deceleration phases of gait. The spring elements store this recovered energy and release it during acceleration phases, transforming energy waste into useful mechanical assistance and improving energy 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
This design achieves a lightweight, power-efficient, and biologically realistic joint system capable of varying stiffness and damping, storing and releasing energy efficiently, thereby extending operational time and reducing power consumption.
Implementation Method 1
employing an electric motor for supplying positive energy to and storing negative energy from an artificial joint or limb, as well as elastic elements such as springs
Implementation Method 2
controllable variable damper components, for passively storing and releasing energy and providing adaptive stiffness
Data Source
AI summary
Artificial limbs and joints that behave like biological limbs and joints employ a synthetic actuator which consumes negligible power when exerting zero force, consumes negligible power when outputting force at constant length (isometric) and while performing dissipative, nonconservative work, is capable of independently engaging flexion and extension tendon-like, series springs, is capable of independently varying joint position and stiffness, and exploits series elasticity for mechanical power amplification.