Segmented Prosthetic Arm with Harmonic Drive and Compliance
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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, and provide limited degrees of freedom, making it difficult for users to perform finer tasks or move in a realistic manner.
Innovation Solution
A prosthetic device with a compliant structure incorporating multiple joints, including a shoulder flexion joint, humeral rotator, elbow flexion joint, wrist rotation joint, and wrist flexion joint, equipped with motors, gear systems, potentiometers, and compliance sensors, allowing for increased range of motion and tactile capabilities, and featuring a hand assembly with opposition movement capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing prosthetic arm designs are used, then the device structure is simple, but the range of motion and degrees of freedom are limited
Solution Approach 1:
The prosthetic arm is divided into multiple functional segments including shoulder assembly with flexion and abduction joints, elbow assembly with flexion joint, wrist assembly with rotation and flexion joints, and hand assembly. Each segment is independently controllable, providing multiple degrees of freedom and realistic movement capabilities while maintaining modular construction
Solution Approach 2:
The prosthetic arm incorporates dynamic compliance through spring elements in the shoulder and elbow assemblies, allowing the structure to adapt its stiffness characteristics. The compliant structure enables natural movement patterns and absorbs shocks, enhancing versatility without requiring overly complex rigid mechanisms
2Adaptability or versatility
If existing prosthetic hand designs are used, then the device is simple to manufacture, but the tactile capabilities and movement realism are limited
Solution Approach 1:
The hand assembly incorporates force sensors that detect contact forces and tactile interactions with objects. This feedback is transmitted to the control system, enabling closed-loop control of grip strength and finger positioning, which enhances tactile capabilities and realistic movement while managing manufacturing complexity through integrated sensing
3Ease of operation
If prosthetic devices with limited movement are used, then the device complexity is reduced, but the ability to perform finer tasks is impaired
Solution Approach 1:
The prosthetic arm is divided into multiple functional segments including shoulder assembly with flexion and abduction joints, elbow assembly with flexion joint, wrist assembly with rotation and flexion joints, and hand assembly. Each segment is independently controllable, providing multiple degrees of freedom and realistic movement capabilities while maintaining modular construction
Solution Approach 2:
The control system integrates multiple functions into a unified control architecture that manages all joint actuators, force sensors, and compliance mechanisms. This universal control approach enables coordinated movement across all segments, allowing users to perform diverse tasks from gross motor movements to fine dexterous manipulations
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 device provides improved range of motion, increased comfort, and enhanced tactile feedback, enabling users to perform complex tasks with greater ease and precision, reducing reliance on manual positioning.
Implementation Method 1
The harmonic drive gearing system 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
The exterior rim of the circular spline additionally accommodates stationary reactor elements and series elastic elements. 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 via the reactor movement in relation to the stationary magnet. In this manner, the compliance is built into the shoulder flexion joint and works to absorb energy when the joint is subjected to a load or an unexpected shock.
Implementation Method 3
The clutch has an input cage, an output hex, and a clutch race, or ground. 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.
Data Source
AI summary
A prosthetic arm apparatus including 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 prosthetic support apparatus 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.