MR Fluid Clutch Exoskeleton Joints for High-Torque Bandwidth
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Solution Overview
Problem
Existing exoskeletons and prostheses face challenges with low bandwidth actuators that cause discomfort and inefficiency due to mechanical force distribution, leading to unnatural movement and potential human injury, as they fail to match the impedance of the human body and are not easily controllable.
Innovation Solution
Employing magnetorheological (MR) fluid actuators with variable torque transmission, connected through a clutch apparatus, to create a wearable device that adapts to human power, providing high bandwidth and compliant interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If electric motors with speed reducers are used to actuate joints, then torque output is increased, but bandwidth and dynamic response are reduced
Solution Approach 1:
The patent employs magnetorheological fluid clutches that can dynamically adjust their torque transmission characteristics in real-time based on control signals. This allows the actuator to provide high torque when needed while maintaining high bandwidth and fast response, resolving the contradiction between torque output and bandwidth that plagues traditional geared motor systems.
Solution Approach 2:
The invention replaces traditional mechanical speed reducers (gears, linkages) with magnetorheological fluid clutches that use magnetic field control to achieve torque multiplication. This substitution eliminates the mechanical friction, backlash, and inertia associated with gear systems while maintaining high torque output capability, thereby preserving bandwidth and dynamic response.
2Force
If mechanical force distribution is applied to soft tissues, then load transfer to human is achieved, but comfort is reduced due to ineffective power transfer
Solution Approach 1:
The magnetorheological fluid clutch allows dynamic adjustment of torque transmission parameters to match human impedance characteristics. By controlling the magnetic field strength, the system can modulate the stiffness and damping properties of the actuator, providing effective load transfer while maintaining comfort through compliant interaction with human tissues.
Solution Approach 2:
The system uses sensors to detect human motion and force characteristics, then feeds this information back to the controller which adjusts the magnetorheological clutch parameters in real-time. This feedback mechanism ensures that the mechanical force distribution adapts to human needs, achieving effective power transfer while minimizing discomfort.
3Force
If high inertia parts are used in the powertrain, then torque density is improved, but bandwidth is reduced due to opposition to speed change
Solution Approach 1:
The invention replaces high-inertia mechanical components (gears, linkages, brakes) with magnetorheological fluid clutches that achieve torque density through magnetic field control rather than mechanical mass. The MR fluid clutch has negligible inertia compared to geared systems, allowing high bandwidth while maintaining high torque density through controllable magnetic coupling.
Solution Approach 2:
The system changes the physical state and properties of the magnetorheological fluid through magnetic field application, allowing torque density to be adjusted without changing the physical mass of the actuator. This enables high torque density on demand while maintaining low inertia and high bandwidth for rapid speed changes.
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 MR fluid actuators enhance controllability and comfort by matching human impedance, allowing smooth movement and reducing torque-induced discomfort, making the system more transparent and natural to the user.
Implementation Method 1
at least one magnetorheological (MR) fluid clutch apparatus receiving torque from the at least one power source, the at least one magnetorheological clutch apparatus operable to generate a variable amount of torque transmission when subjected to a magnetic field
Data Source
AI summary
A system comprises one or more wearable devices including a first body interface adapted to be secured to a first bodily part. A second body interface is adapted to be secured to a second bodily part separated from the first bodily part by a physiological joint. One or more joints provide one or more degrees of freedom between the first body interface and the second body interface. A magnetorheological (MR) fluid actuator unit comprises one or more power sources. An MR fluid clutch apparatus receiving torque from the at least one power source, the at least one MR fluid clutch apparatus operable to generate a variable amount of torque transmission when subjected to a magnetic field. A transmission couples the MR fluid actuator unit to the wearable device for converting torque from the MR fluid actuator unit to relative movement of the body interfaces with respect to one another.