Prosthetic Arm Segmented Joints and Compliance Mechanisms
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Solution Overview
Problem
Existing prosthetic arms have limited movement capabilities, particularly for individuals who have lost their entire arm from shoulder to hand, offering limited degrees of freedom and realistic motion, which hinders finer tasks and user comfort.
Innovation Solution
A prosthetic device incorporating a compliant structure with multiple joints, including shoulder flexion, abduction, humeral rotation, elbow flexion, wrist rotation, and wrist flexion joints, equipped with motors, harmonic drives, potentiometers, non-backdriving clutches, and compliance sensors, allowing for improved range of motion, tactile capabilities, and comfort through energy absorption and precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If existing prosthetic arms are designed with simple structure, then manufacturing cost is reduced, but range of motion and degrees of freedom are limited
Solution Approach 1:
The prosthetic arm is divided into multiple independent joint segments (shoulder flexion, shoulder abduction, elbow flexion, wrist rotation, wrist flexion), each with its own actuator and control system. This segmentation allows each joint to move independently, achieving comprehensive range of motion while maintaining modular structure that simplifies manufacturing and assembly.
Solution Approach 2:
Multiple joint mechanisms are nested within each other, with the elbow joint positioned within the shoulder joint structure, and the wrist joint nested within the elbow structure. This nested arrangement achieves complex multi-degree-of-freedom motion while minimizing overall device volume and structural complexity.
2Adaptability or versatility
If prosthetic hand is designed with single degree of movement, then device complexity is reduced, but capability for finer tasks is limited
Solution Approach 1:
The prosthetic hand is segmented into multiple independent fingers (thumb, index, middle, ring, pinky), each capable of independent movement with multiple degrees of freedom. This segmentation enables dexterous manipulation and fine motor tasks while maintaining modular construction that simplifies manufacturing.
Solution Approach 2:
The hand structure incorporates dynamic elements including compliant mechanisms and variable stiffness actuators that allow the fingers to adapt their movement characteristics based on task requirements. This dynamic design enables both gross motor movements and fine precision tasks without requiring overly complex rigid structures.
3Ease of operation
If prosthetic arm lacks compliance mechanism, then device complexity is reduced, but user comfort and energy absorption are limited
Solution Approach 1:
The prosthetic arm incorporates compliance mechanisms that dynamically adjust stiffness parameters based on operational conditions. Series elastic actuators and variable impedance joints change their mechanical properties in real-time, providing soft compliant interaction during contact tasks while maintaining rigid support during lifting tasks, thereby improving user comfort without requiring permanently complex structures.
Solution Approach 2:
Compliance sensors and force feedback mechanisms continuously monitor interaction forces between the prosthetic arm and the environment, feeding this information back to the control system. This feedback enables real-time adjustment of joint stiffness and damping characteristics, providing natural feel and energy absorption while maintaining simple base structure.
4Extent of automation
If prosthetic arm uses manual positioning, then device complexity is reduced, but reliance on user manual adjustment increases
Solution Approach 1:
The prosthetic arm incorporates intent detection sensors (EMG, IMU, force sensors) that automatically detect user movement intentions and initiate appropriate motor commands without manual intervention. The system self-adjusts joint positions and motor parameters based on detected intent, providing automatic positioning while maintaining relatively simple control architecture through direct sensor-to-actuator pathways.
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 prosthetic arm provides enhanced range of motion, increased comfort, and improved tactile feedback, enabling users to perform finer tasks with greater ease and independence from manual positioning, mimicking human arm functionality.
Implementation Method 1
The harmonic drive has an interior wave generator that corresponds with the flexible spline. The spline in turn engages the exterior circular spline, resulting in drastic reduction rates and driving the shoulder output flange
Implementation Method 2
Upon application of force, the position of the circular spline alters causing the series elastic elements to compress against the reactor elements. The movement of the reactor elements transmits the rotational displacement of the circular spline
Implementation Method 3
When the shoulder flexion joint is acted upon by an output force, the output hex is engaged in a friction lock with the clutch race and bearings lining the exterior of the output hex, preventing backward transfer of power through the clutch
Implementation Method 4
The electrically driven motor rotor drives the belt that is defined by two pulleys. The first pulley is magnetically driven by the motor rotor
Data Source
AI summary
A prosthetic arm apparatus comprising a plurality of segments that provide a user of the prosthetic arm apparatus with substantially the same movement capability and function as a human arm. The segments are connectable to one another and connectable to a harness mount that may be adorned by the user. Each segment of the plurality of segments provides a portion of the movement capability, enabling the plurality of connected segments connected to the harness mount to provide substantially the same movement capability as that lacking in the user.