Prosthetic Joint Actuator Decoupling for Battery Autonomy
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Solution Overview
Problem
Existing prosthetic devices face challenges with high weight, size, battery autonomy, and inefficiency due to constant engagement of the actuator and damper, leading to increased consumption and noise, and lack of anthropomorphic alignment, which affects user comfort and reliability.
Innovation Solution
A prosthetic device with a mechanical engagement element that allows the actuator assembly to be decoupled from the damper assembly, using a strain wave reduction gearbox and hydraulic damper, controlled by sensors and a control unit to adjust engagement based on user activity, ensuring efficient energy use and reduced size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the actuator assembly and damper assembly are constantly engaged, then the prosthetic device can provide active power for demanding activities, but the weight, size, and energy consumption increase
Solution Approach 1:
The patent implements a dynamic engagement mechanism where the actuator assembly can be selectively coupled or decoupled from the distal portion based on activity requirements. During low-demand activities like walking, the actuator is decoupled to reduce weight and energy consumption. During high-demand activities like standing up or climbing stairs, the actuator is engaged to provide active power assistance.
Solution Approach 2:
The prosthetic device is segmented into functionally independent modules: the actuator assembly, the damper assembly, and the distal portion. The mechanical engagement element allows these segments to be selectively connected or disconnected, enabling the system to operate with only the necessary components engaged at any given time, thereby reducing overall system weight and energy requirements.
2Power
If the actuator assembly is constantly engaged, then active power can be provided for demanding activities, but battery autonomy is reduced due to high consumption
Solution Approach 1:
The actuator assembly operates in periodic cycles rather than continuously. The control system monitors activity levels and engages the actuator only during periods when active power is needed (standing up, climbing stairs). During normal walking periods, the actuator remains decoupled and inactive, allowing the battery to conserve energy and extend autonomy.
Solution Approach 2:
The system dynamically adjusts its power consumption profile by transitioning between engaged and decoupled states. This dynamic operation mode allows the battery to discharge only during brief periods of high demand rather than maintaining a constant high-power state, significantly extending battery autonomy while still providing necessary active assistance when needed.
3Power
If the actuator assembly is constantly engaged, then active power can be provided, but noise increases at all times of operation
Solution Approach 1:
The actuator assembly operates periodically rather than continuously, engaging only during activities that require active power assistance. During normal walking phases, the actuator remains decoupled and silent. This periodic engagement pattern significantly reduces overall noise levels while maintaining the capability to provide active power when needed.
Solution Approach 2:
The actuator assembly is extracted from the continuous operational chain and selectively engaged only when necessary. By removing the actuator from the always-engaged configuration and instead coupling it only during demanding activities, the system eliminates unnecessary noise generation during normal walking, improving user comfort while preserving active assistance capability.
4Ease of manufacture
If the standard pyramidal coupling element is used, then connection is simplified, but alignment with the natural joint axis cannot be achieved for all patients
Solution Approach 1:
The coupling system incorporates adjustable alignment features at the joint interface while maintaining a standardized pyramidal coupling element for manufacturing simplicity. The articular portion includes adjustable components that can be locally modified to match each patient's specific anatomical alignment requirements, allowing the standardized coupling element to work with customized alignment configurations.
Solution Approach 2:
The system allows adjustment of alignment parameters (angular orientation, axial position) at the articular portion while keeping the basic pyramidal coupling geometry standardized. This enables the same standardized coupling element to accommodate different patient anatomies by changing the alignment parameters of the connected components, thus achieving both manufacturing simplicity and patient-specific adaptability.
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 device achieves reduced weight and size, improved battery autonomy, and enhanced comfort by optimizing energy use, allowing for a wide range of activities with minimal consumption and noise, while maintaining anthropometric dimensions.
Implementation Method 1
using a strain wave reduction gearbox
Implementation Method 2
A damper assembly is also provided, connected to said articular portion and adapted to absorb energy when a torque is applied between said proximal portion and said distal portion
Data Source
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AI summary
Prosthetic device, suitable to replace at least in part the limb of a user, comprising a proximal prosthetic portion (1) suitable to be coupled to a segment of the user's limb and a distal prosthetic portion (2). The proximal prosthetic portion (1) and the distal prosthetic portion (2) are inter-connected by an articular portion (3) comprising an articular actuator assembly (5) for rotatably actuating said distal portion (2) with respect to said proximal portion (1) about an axis of rotation (30). A damper assembly (4) connected to said articular portion (3) is provided and adapted to absorb energy when a torque is applied between said proximal portion (1) and said distal portion. The articular actuator assembly (5) is provided with a removable mechanical engagement element (6) such that the actuator assembly (5) can be switched from a coupled condition in which it rotatably drives said distal portion (2) with respect to said proximal portion (1) to a decoupled condition in which said distal portion (2) is only coupled to said damper assembly (4) for a predetermined rotation angle. The articular actuator assembly (5) includes an electric motor (50) and a reduction gearbox (51), which reduction gearbox (51) is connected in input with the motor (50) and in output with said engagement element (6). The engagement element (6) comprises an actuating part connected to the output of the reduction gearbox (51) and an actuating part integral with the distal portion (2). The actuating part and the actuated part are respectively provided with abutment and reciprocal fitting surfaces arranged on radial planes with respect to said rotation axis (30), which abutment surfaces are respectively provided on at least one protrusion of the actuating part (60) and on at least one protrusion of the actuated part (61 ). Said protrusions (60, 61) have angular extensions such that in the said decoupled condition the protrusion of the actuating part (60) is positioned angularly, spaced from the protrusion of the actuated part (61) so as to constitute an end stop for the extension of the distal portion (2) and thus allow the free flexion of the distal portion (2) for a predetermined angular amplitude, while in the said coupled condition the protrusions of the actuating part (60) and of the actuated part (61 ) are in abutment with each other so as to actuate the relative rotation of the distal portion (2) with respect to the proximal portion (1) in extension.