Powered Prosthetic Wrist Flexion Device Using Nested Planetary Drive
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Solution Overview
Problem
Individuals with upper-limb amputations face difficulties in orienting and positioning objects due to the lack of additional degrees of freedom in their prosthetic wrists, leading to uncomfortable compensatory body motions, as existing prosthetic devices often lack wrist flexion and rotation capabilities.
Innovation Solution
A powered prosthetic wrist flexion device (PWFD) with a series elastic element and two-stage friction planetary drive, combined with a microcontroller and brushless DC motor, provides two additional degrees of freedom through wrist flexion and rotation, enhancing the ability to orient objects and reduce awkward motions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a powered prosthetic wrist flexion device is added to provide additional degrees of freedom, then the ability to orient objects is improved, but the device complexity increases
Solution Approach 1:
The patent implements a two-stage friction planetary drive where the second stage planetary drive is nested within the first stage planetary drive. This nested configuration allows both drive stages to be integrated in a compact arrangement, providing the necessary two additional degrees of freedom (wrist flexion and rotation) while minimizing the increase in overall device complexity and size.
Solution Approach 2:
The patent combines multiple functions into integrated components. The series elastic element serves dual purposes: providing torque control and acting as an overload protection mechanism. The friction planetary drives combine gear reduction and torque multiplication in a single integrated system, reducing the number of separate components needed.
2Measurement precision
If series elastic element and friction planetary drive are used for torque control, then torque control precision is improved, but the device complexity increases
Solution Approach 1:
The series elastic element provides intrinsic compliance and automatic torque control without requiring complex electronic control systems. The elastic element naturally regulates torque through its mechanical properties, and simultaneously serves as an overload protection mechanism that passively limits maximum torque, reducing the need for active control systems.
Solution Approach 2:
The series elastic element acts as an intermediary between the motor and the load, providing mechanical compliance and torque regulation. This intermediate elastic element smooths out torque fluctuations and provides inherent damping, improving torque control precision while simplifying the overall control architecture.
3Ease of operation
If multiple degree-of-freedom wrists are implemented, then ease of operation is improved, but the weight of the prosthetic device increases
Solution Approach 1:
The nested planetary drive configuration allows both wrist flexion and rotation mechanisms to be integrated within a compact structure. By nesting the second stage planetary drive inside the first stage, the patent minimizes the overall volume and weight of the powered wrist assembly while still providing both additional degrees of freedom for improved ease of operation.
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 PWFD enables six degrees of freedom, allowing for precise object positioning and orientation, reducing the need for compensatory body motions and enhancing the usability of prosthetic devices by providing improved torque control, reduced noise, and overload protection.
Implementation Method 1
A powered prosthetic wrist flexion device (PWFD) with a series elastic element
Implementation Method 2
two-stage friction planetary drive
Data Source
AI summary
Technology is described to provide a powered prosthetic wrist flexion device or elbow device. This device helps individuals with upper-limb loss to orient and position grasped objects.