Adaptive Viscous Coupling for Exoskeleton Stiffness Control
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Solution Overview
Problem
Robotic exoskeletons face challenges in providing optimal user comfort and safety due to the transmission of excessive forces during operation, which can lead to discomfort or injury, and the need for tactile feedback is compromised by isolation from environmental forces.
Innovation Solution
The integration of a viscous coupling system with a fluid of variable viscosity, controlled by a responsive control system, to adaptively modify the physical interface between the user and the exoskeleton, allowing for dynamic adjustment of stiffness based on operating conditions and user commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the exoskeleton uses rigid structural members and actuators to provide motive force, then the exoskeleton can exert sufficient force to increase user strength and mobility, but excessive forces are transmitted to the user causing discomfort or injury
Solution Approach 1:
A viscous coupling device is introduced as an intermediary element between the actuator and the user interface. This device contains a viscous fluid that can dynamically adjust its stiffness to selectively transmit or isolate forces. When high forces are detected, the viscous coupling becomes stiffer to transmit force; when low forces are detected, it becomes softer to isolate the user from excessive forces, thus resolving the contradiction between providing sufficient motive force and preventing excessive force transmission.
Solution Approach 2:
The viscous coupling device changes its physical parameter (stiffness/viscosity) dynamically based on operating conditions. By adjusting the viscosity of the fluid in response to sensed forces or control signals, the system can adaptively modulate force transmission characteristics, allowing the exoskeleton to provide high force when needed while protecting the user from excessive forces during other operation phases.
2Object-affected harmful factors
If the exoskeleton isolates the user from environmental forces to prevent injury, then user safety is improved, but tactile feedback is compromised reducing control and interaction quality
Solution Approach 1:
The viscous coupling acts as a smart intermediary that selectively transmits forces based on their characteristics. It allows beneficial tactile feedback forces (lower magnitude, informative) to pass through to the user while blocking harmful excessive forces. This selective force transmission maintains tactile feedback for control purposes while preventing injury from excessive forces, resolving the information loss problem.
Solution Approach 2:
The coupling device transitions from a static isolation approach to a dynamic, adaptive approach. By continuously adjusting its stiffness based on real-time force sensing and control algorithms, the system can dynamically determine which forces to transmit and which to isolate, enabling both safety and tactile feedback simultaneously through time-varying mechanical properties.
3Adaptability or versatility
If the exoskeleton uses a fixed stiffness interface, then the structure is simple and reliable, but it cannot adapt to different operating conditions and user needs
Solution Approach 1:
The viscous coupling device incorporates self-regulating characteristics where the viscous fluid automatically adjusts its effective stiffness in response to applied forces or control signals. This self-adjusting behavior reduces the need for complex external control mechanisms while still achieving adaptive stiffness, as the fluid's inherent rheological properties provide the adaptation capability with minimal additional system complexity.
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 enhances user comfort, control, and safety by providing optimal tactile feedback and reducing the risk of injury through adaptive stiffness adjustment, ensuring effective interaction with the environment while minimizing excessive force transmission.
Implementation Method 1
The viscous coupling is comprised of a fluid having a viscosity that is selectively variable responsive to viscosity control signals from the control system
Data Source
Figure 1
Figure 2A~2B
Figure 2C
AI summary
A system for preventing discomfort to a user of a robotic exoskeleton (200) determines the existence of an exoskeleton operating condition which has the potential to cause at least one of a discomfort or an injury to a user (204) when the exoskeleton is being worn by the user. Responsive to the determining, an exoskeleton control system (224) selectively controls at least one viscous coupling (208, 210) disposed at an interface location (201, 203) of the exoskeleton where a physical interaction occurs between a portion of the user and a portion of the exoskeleton when the exoskeleton is in use. The control system selectively varies a viscosity of a fluid (216) comprising the viscous coupling to control the stiffness of the interface.