Semi-Active Robotic Joint for Exoskeleton Locomotion
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Solution Overview
Problem
Current modular knee exoskeleton technologies are either costly and limited in functionality as fully passive systems or expensive and complex as powered systems, lacking a cost-effective and functionally versatile solution that can provide appropriate resistance and flexibility for locomotion.
Innovation Solution
The development of energetically passive robotic joints that use mechanical hardware to embed functionality, reducing the burden on microcontrollers and sensors, allowing for resistance during flexion and free motion during extension, mimicking the stance and swing phases of human locomotion without external power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fully passive systems are used, then cost is reduced, but functionality is limited
Solution Approach 1:
The system is divided into passive mechanical components (spring, damper, locking mechanism) that handle basic locomotion functions, while a microcontroller handles advanced control. This segmentation allows the system to achieve low cost through passive components while maintaining functionality through modular electronic control.
Solution Approach 2:
The robotic joint is designed to perform multiple functions: it provides passive resistance during flexion, allows free extension, enables locked stance phase, and permits swing phase motion. A single device thus achieves both cost-effectiveness and functional versatility by integrating mechanical passive elements with microcontroller control.
2Adaptability or versatility
If powered systems are used, then functionality is enhanced, but cost and size increase
Solution Approach 1:
The system uses passive mechanical components (spring and damper) that automatically provide resistance and motion control without requiring external power sources. The microcontroller only needs to manage switching between states, not generate continuous power, thereby reducing cost while maintaining functionality.
Solution Approach 2:
The system dynamically switches between passive mechanical operation and microcontroller-controlled operation. During stance phase, the locking mechanism engages for stability; during swing phase, the system transitions to free motion. This dynamic behavior provides full functionality without requiring continuously powered actuators.
3Adaptability or versatility
If microcontroller controlled resistive knees are used, then functional diversity is improved, but system impedance to motion increases and cost rises
Solution Approach 1:
The control system is segmented so that basic resistive functions are handled by passive mechanical components (spring and damper), while the microcontroller only manages state switching. This reduces the computational burden and sensor requirements, lowering complexity and cost while maintaining functional diversity.
Solution Approach 2:
Complex electronic control is replaced with simple mechanical passive elements for the resistive functions. The spring provides elastic resistance, the damper provides viscous resistance, and the locking mechanism provides mechanical constraint. This substitution reduces system impedance and complexity while maintaining functional diversity.
Data Source
AI summary
A robotic joint comprises a first link, a middle link, a torque generator, a second link, and a locking mechanism. Different ends of the middle link are rotatably coupled to the first link and the second link. The torque generator is coupled to the first link and the middle link and is configured to produce torque between these links. The locking mechanism is switchable between a locking state and an unlocking state. In the unlocking state, the locking mechanism allows free rotation of the second link relative to the middle link in the first and second rotation directions. In the locking state, the locking mechanism is configured to impede rotation of the second link relative to the middle link in the first rotation direction and to allow rotation of the second link relative to the middle link in the second rotation direction opposite of the first rotation direction.