Single Drive Shaft Simulator for Multi-Axis Artificial Joint Testing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Commercially available simulators for testing artificial joints are complex, expensive, and suffer from synchronization issues in multi-axis motion, leading to inaccurate results and a lack of robustness, necessitating a more accurate, robust, and cost-effective solution that can apply various types of motion and forces while maintaining synchronous movement over extended cycles.
Innovation Solution
A single drive shaft simulator that allows up to four independent actions simultaneously, enabling motion about three orthogonal axes with dynamic or static compressive forces, adjustable amplitude and profile, and the ability to immerse specimens in saline or bovine serum at controlled temperatures, ensuring synchronization and durability through a mechanical system using pulleys and scotch yoke mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If servo-hydraulic units are used for simulating joint implants, then the simulator can provide multi-axis motion capability, but the device becomes very expensive and complex
Solution Approach 1:
The patent combines multiple motion control functions into a single integrated mechanism. The test apparatus uses one motor (150) that drives all three orthogonal axes of motion through a unified mechanical transmission system involving belts (138a, 138b, 138c) and pulleys (34a-d, 36a-d), eliminating the need for separate servo-hydraulic units for each axis and reducing overall system complexity while maintaining multi-axis capability
Solution Approach 2:
The single motor (150) and drive shaft (32) system performs multiple functions by controlling motion along three orthogonal axes (x, y, z) simultaneously. This universal drive mechanism replaces multiple specialized servo-hydraulic actuators, providing the same multi-axis motion capability through a simpler, more cost-effective unified system
2Ease of operation
If separate servo controls are used for different axes, then each axis can be controlled independently, but synchronization problems occur over extended test cycles
Solution Approach 1:
The patent merges all axis control functions into a single motor (150) driving a common shaft (32). This unified control system inherently synchronizes motion across all axes (x, y, z) because they share the same rotational reference, eliminating the synchronization drift problems that occur with separate servo controls during extended test cycles of one to ten million cycles
Solution Approach 2:
The system incorporates feedback mechanisms including encoders (148a, 148b) on the pulleys and a controller (145) that monitors and adjusts the position and motion of all axes. This feedback loop ensures that the single motor's rotational position is accurately translated to each axis, maintaining precise synchronization throughout the test duration
3Adaptability or versatility
If multiple input sources are used for driving different axes, then motion versatility is achieved, but the system becomes less robust and more prone to problems
Solution Approach 1:
The patent consolidates multiple drive sources into a single motor (150) that drives all motion functions through a mechanically robust transmission system. This single-point drive architecture eliminates the reliability issues associated with multiple independent input sources, as there is only one motor to maintain and one drive shaft (32) to fail, while still achieving full motion versatility through the mechanical belt and pulley system
Solution Approach 2:
The system segments the motion transmission into independent controllable paths from the single drive shaft (32) to each axis through separate belt-pulley assemblies (138a with pulleys 34a, 36a for x-axis; 138b with pulleys 34b, 36b for y-axis; 138c with pulleys 34c, 36c for z-axis). This segmentation allows each axis to be controlled independently through the unified drive, maintaining versatility while ensuring robustness through the simplicity of the single motor architecture
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 simulator provides accurate and robust testing of artificial joints under simulated loading conditions, maintaining synchronization and durability over millions of cycles, with adjustable motion and force profiles, and the ability to test at varying temperatures, offering a cost-effective solution for evaluating wear and integrity.
Implementation Method 1
The drive shaft may be provided with a plurality of pulleys and each driven pulley may be connected to a rotary to linear converter, such as a scotch yoke mechanism
Implementation Method 2
Each drive pulley may be connected to a corresponding driven pulley through an associated belt necessary for providing the drive force
Implementation Method 3
A cavity filled with a fluid for immersing the associated artificial joint implant. The fluid is preferably one of a saline or bovine serum
Implementation Method 4
The apparatus may include means for controlling a temperature of the fluid
Data Source
AI summary
A single drive shaft simulator and method is disclosed that allows up to four independent actions to be imposed on a test specimen such as an artificial joint specimen. These motions about mutually orthogonal axes are provided, and a constant compressive force and/or dynamic force may also be applied. The mechanical simulator is simple, accurate, and robust. The simulator assures synchronous movement where amplitude and profiles of the motion can be independently adjusted.