MR Fluid Clutch Control with Slippage and Lock Mode Switching
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Solution Overview
Problem
Current distributed power devices rely on hydraulic or electromagnetic actuation, which face limitations such as dynamic response, efficiency, and maintenance issues, while magnetorheological (MR) fluid clutch apparatuses can enhance performance but are prone to property changes due to energy dissipation during torque transmission.
Innovation Solution
A control system for MR fluid clutch apparatuses that switches between controlled slippage and lock modes based on movement parameters, using a clutch driver, motor driver, and mode selector module to manage slippage and torque transmission, reducing energy dissipation and property changes over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If MR fluid clutch apparatus transmits torque with angular speed difference between input and output, then torque transmission capability is improved, but energy dissipation increases causing property changes over time
Solution Approach 1:
The system dynamically switches between two operational modes: lock mode (minimal slippage, low energy dissipation) and controlled slippage mode (higher slippage, high torque transmission). This dynamic mode switching allows the system to adapt to varying operational requirements, achieving high torque transmission when needed while minimizing energy dissipation during normal operation.
Solution Approach 2:
The system changes the operational parameters of the MR fluid clutch by adjusting the magnetic flux density applied to the MR fluid. By varying the magnetic field strength, the system can control the yield shear stress of the MR fluid, thereby controlling the amount of slippage and balancing torque transmission capability with energy dissipation.
2Reliability
If hydraulic actuation is used for distributed power devices, then reliability against mechanical jam is improved, but dynamic response and efficiency are limited
Solution Approach 1:
The system replaces traditional hydraulic actuation with magnetorheological fluid-based actuation. The MR fluid clutch apparatus uses magnetic field control to transmit torque, eliminating the need for hydraulic fluid and mechanical linkages that are prone to jamming. This substitution provides both the reliability of mechanical jam resistance and the fast dynamic response of magnetic field control.
3Speed
If electromagnetic actuation is used for high dynamic applications, then dynamic performance is improved, but device weight increases due to direct-drive motors
Solution Approach 1:
The system introduces an intermediary mechanism - the MR fluid clutch apparatus - between the motor and the load. This allows the use of lighter motors while maintaining high dynamic performance, as the MR fluid clutch can provide torque multiplication and control without the weight penalty of oversized direct-drive motors.
4Weight of moving object
If reduction gearboxes are used with electromechanical actuators, then device weight is reduced, but output inertia, friction and backlash diminish dynamic performance
Solution Approach 1:
The system replaces traditional reduction gearboxes with an MR fluid clutch apparatus for torque transmission. This substitution eliminates mechanical gears, reducing output inertia, friction, and backlash while maintaining the weight benefits of using smaller motors. The magnetic field-based torque transmission provides smoother and more responsive control.
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 system improves dynamic performance and reduces energy dissipation in MR fluid clutch apparatuses, enhancing the efficiency and reliability of torque transmission while minimizing exposure to property changes, thus addressing the limitations of existing actuation methods.
Implementation Method 1
Magnetorheological fluid is known to permanently change properties over time. These changes may include, non-exhaustively, a change in viscosity, a change in the ability to transmit a shear stress in function of the magnetic flux density in the MR fluid
Implementation Method 2
a clutch driver configured to drive the at least one MR fluid clutch apparatus between a controlled slippage mode, in which slippage between a clutch input and the clutch output of the MR fluid clutch apparatus varies, and a lock mode, in which said slippage between the clutch input and the clutch output is maintained below a given threshold
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A control system is provided for controlling movements of an end effector connected to a clutch output of at least one magnetorheological (MR) fluid clutch apparatus. A clutch driver is configured to drive the at least one MR fluid clutch apparatus between a controlled slippage mode, in which slippage between a clutch input and the clutch output of the MR fluid clutch apparatus varies, and a lock mode, in which said slippage between the clutch input and the clutch output is maintained below a given threshold, the clutch output transmitting movement to the end effector. A motor driver is configured to control a motor output of at least one motor, the motor output coupled to the clutch input. A mode selector module is configured to receive signals representative of at least one movement parameter of the end effector, the mode selector module selecting a mode between the controlled slippage mode and the lock mode of the clutch driver based on the signals, and switching the selected mode based on the signals. A movement controller controls the clutch driver and the motor driver to displace the end effector based on at least one of the selected mode and on commanded movements of the end effector for the end effector to achieve the commanded movements. A method for controlling movements of an end effector connected to the MR fluid clutch apparatus is also provided.