Prosthetic Leg Coupling Device With Torque-Position State Switching
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Solution Overview
Problem
Existing joint devices, such as prosthetic legs, struggle to perform appropriate control in both weighted and non-weighted states, particularly during activities like stair climbing and walking on flat ground.
Innovation Solution
A joint device with a coupling mechanism and an enlarging and reducing device that includes a power source, power transmission unit, and control unit, allowing transition between weighted and non-weighted states by controlling torque and position based on specific target values to manage the angle and power transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single control method is used for both weighted and non-weighted states, then the control system is simple, but the device cannot perform appropriate control in either state
Solution Approach 1:
The control system dynamically switches between torque control and position control modes based on the detected state (weighted or non-weighted). The control unit changes the control method according to real-time conditions, making the system adaptable without requiring completely separate control systems for each state.
Solution Approach 2:
The control parameters are changed based on the operational state. In weighted state, torque control with torque target values is used, while in non-weighted state, position control with position target values is used. This parameter switching enables appropriate control for each state while using a single unified control system.
2Force
If torque control is used in weighted state, then the device can support loads effectively, but control precision decreases in non-weighted state
Solution Approach 1:
The control mode is dynamically switched based on the operational state. Torque control is activated in weighted state to maximize load support capability, while position control is activated in non-weighted state to achieve precise position control. This dynamic switching resolves the trade-off between force capability and position precision.
3Measurement precision
If position control is used in non-weighted state, then control precision improves, but the device cannot effectively support loads in weighted state
Solution Approach 1:
The control parameter is changed from position target values to torque target values when transitioning from non-weighted to weighted state. This parameter change enables the system to prioritize load support capability when needed while maintaining position control precision when operating in non-weighted state.
4Speed
If power transmission is continuously connected, then the power source can respond quickly to control commands, but energy consumption increases
Solution Approach 1:
The power transmission is periodically connected and disconnected based on operational needs. The connection and disconnection mechanism connects power transmission when control action is required and disconnects it when not needed, creating a periodic action pattern that balances response speed with energy conservation.
Data Source
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AI summary
A control unit (10) of an electric prosthetic leg (1) controls a motor (M) based on a torque target value which is a target value of a torque related to a torque of an enlarging and reducing device (200), during a stance phase which is a weighted state, and controls the motor (M) based on a position target value which is a target value of a position of the enlarging and reducing device (200), during a swing phase which is a non-weighted state.