Orthopedic Joint Actuator with Adjustable Self-Locking Transmission
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Solution Overview
Problem
Existing orthopedic joint devices, such as ankle and knee joints, face challenges in combining the benefits of self-locking and non-self-locking transmissions, leading to issues with stability, energy efficiency, and adjustability, especially in the event of actuator failure or varying heel heights and movement patterns.
Innovation Solution
A method where an electric control unit dynamically controls an active actuator to manage the movement of a joint's second part relative to its first part based on external forces, using a self-locking transmission with adjustable static and sliding friction, allowing for both free movement and controlled damping, and switching between modes to optimize energy use and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a self-locking transmission is used to prevent uncontrolled movement during actuator failure, then safety and stability are improved, but the joint cannot freely follow external forces during normal operation
Solution Approach 1:
The patent applies the dynamics principle by making the self-locking characteristic of the transmission adjustable rather than fixed. The control unit dynamically modifies the friction properties of the transmission elements based on operational requirements, allowing the system to switch between locked and free-moving states. This resolves the contradiction by enabling both safety (when locked) and ease of operation (when free to follow external forces) at different times.
Solution Approach 2:
The patent implements parameter changes by modifying the friction coefficient between transmission elements through controlled variation of normal force or surface properties. By changing these physical parameters, the transmission can transition between self-locking and non-self-locking states, allowing the system to adapt to different operational conditions and resolve the contradiction between safety and free movement.
2Ease of operation
If the actuator is actively controlled to enable frequent movements during walking, then natural gait is improved, but energy consumption and device weight increase
Solution Approach 1:
The patent applies the self-service principle by enabling the joint to automatically follow external forces applied to it during certain phases of operation. Instead of requiring continuous active actuator control, the passive transmission allows the joint to respond naturally to external forces, reducing energy consumption while maintaining functional performance.
Solution Approach 2:
The patent implements periodic action by alternating between active actuator control phases and passive following phases. The control unit determines when active control is necessary for natural gait and when passive operation is sufficient, creating a periodic pattern of control that reduces overall energy consumption while maintaining gait quality.
3Ease of operation
If a non-self-locking transmission is used to allow free movement during actuator failure, then ease of operation is improved, but uncontrolled movement and buckling occur
Solution Approach 1:
The patent applies the dynamics principle by making the transmission's locking characteristic dynamically adjustable rather than fixed. The control unit can activate self-locking when stability is required and deactivate it when free movement is needed, allowing the system to adapt to different operational states and resolve the contradiction between free movement and joint stability.
Solution Approach 2:
The patent implements feedback by using sensors to detect the operational state and external forces, then using this information to control the actuator and transmission locking state. The control unit continuously monitors conditions and adjusts the transmission characteristics accordingly, ensuring stability when needed while allowing free movement when safe.
4Manufacturing precision
If mechanical stops are used to define range of motion, then manufacturing precision is improved, but adaptability to different users and conditions is reduced
Solution Approach 1:
The patent applies the dynamics principle by replacing fixed mechanical stops with a dynamic control system that can adjust the range of motion limits programmatically. The control unit can modify the operational boundaries based on user-specific parameters and environmental conditions, providing both precision (through controlled actuation) and adaptability (through software configuration).
Solution Approach 2:
The patent implements mechanics substitution by replacing the mechanical stop system with an electronic control system. Instead of physical constraints that limit movement, the actuator and control unit enforce range of motion limits through controlled force application, allowing for flexible adjustment without mechanical modifications.
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 approach enhances the stability and energy efficiency of orthopedic joints by allowing controlled movement in response to external forces, preventing uncontrolled movements during actuator failure, and enabling adjustable range of motion without mechanical stops, thus improving user comfort and safety.
Implementation Method 1
A transmission is self-locking when it can be driven via the input shaft, but not via the output shaft... due to the self-locking effect of the transmission
Data Source
AI summary
The invention relates to a method for controlling a joint (2, 28) of an orthopedic device that comprises a first part (8), a second part (4), which is arranged on the first part (8) such that it can be pivoted about a pivot axis (12), an active actuator (42), a self-locking transmission (16, 50) and an electric control unit for controlling the actuator (42), the electric control unit controlling the actuator (42) during the method in such a way that the second part (4) moves according to forces acting on it externally.