Off-Axis Spine Loading Fixture for Coupled Bending Compression
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Solution Overview
Problem
Conventional spine testing systems require extensive development time and mechatronics expertise, and fail to simulate the multi-axial loading and coupled motions that the spine experiences during physiological activities.
Innovation Solution
A multi-axial spine testing system mounted to a conventional uni-axial test frame, comprising a fixture with an upper and lower assembly that applies axial compression and bending moments, and an external transducer to collect data on primary motions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a custom-built multi-axial spine testing system is developed, then multi-axial loading capability is achieved, but development time and mechatronics expertise requirements increase significantly
Solution Approach 1:
The fixture is designed to provide multiple loading capabilities (axial compression, bending moments, and coupled loading) using a single device mounted on a conventional uni-axial test frame. The upper and lower assemblies with moment arms enable the system to apply multi-axial loads without requiring a completely custom-built system, thus achieving versatility while reducing development time
2Loss of time
If a conventional uni-axial test frame is used, then development time is reduced, but multi-axial loading capability is limited
Solution Approach 1:
The fixture is divided into separate upper and lower assemblies that can be independently configured. Each assembly includes moment arms and loading mechanisms that can be adjusted to provide different loading configurations. This segmentation allows the system to achieve multi-axial loading capability through modular components rather than requiring a completely integrated custom system
Solution Approach 2:
The fixture introduces moment arms that extend perpendicular to the primary loading axis, enabling the conversion of axial forces into bending moments. This dimensional extension allows a uni-axial test frame to generate multi-axial loading conditions by applying forces at offset distances, thus adding rotational loading capability without requiring additional actuators
3Adaptability or versatility
If custom-built testing systems are used, then multi-axial loading is achieved, but system complexity increases
Solution Approach 1:
The fixture serves multiple functions (applying axial compression, bending moments, and coupled loading) through a single integrated device. By mounting the fixture on an existing uni-axial test frame, the system leverages the frame's inherent capabilities while adding multi-axial functionality through the fixture's moment arms and loading mechanisms, thereby reducing overall system complexity
Data Source
AI summary
A multi-axial spine testing system includes a physiological motion unit (PMU); a uni-axial test frame having an input; and a fixture configured to be attached to the test frame and facilitates a plurality of primary motions of one or more of the PMU and the fixture. The plurality of primary motions includes a linear motion of the input and a rotational movement of an output. The fixture has an upper assembly directly or indirectly coupled to the input. The upper assembly transfers the linear motion (Tz) of the actuator to the rotational movement (Rx) of the output. The upper assembly and lower assembly apply a bending moment (MX) and an axial compression (Fz) to the PMU. An external transducer collects data related to or generated by at least the plurality of primary motions. The fixture simultaneously provides the bending motion and axial compression to the PMU.