Abstract
Abstract
Introduction
Back pain affects 80% of the population at some stage in their life with significant costs to society. Mechanisms and causes of pain have been investigated by studying the behaviour of functional spinal units (FSUs) subjected to displacement- or load control protocols in 6 degrees of freedom (DOF). Load control allows specimens to move physiologically in response to applied loads whereas displacement control constrains motion to individual axes. The displacement control system of the Bath University six-axis spine simulator has been validated and the load control system is in the process of iterative development.
Objectives
The objective was to build a computational model of the spine simulator to develop a complete 6 DOF load control system to enable accurate specimen testing under load control.
Methods
SolidEdge part files of the simulator assembly exported to MATLAB Simulink® were used to generate a full model of the simulator. Results from displacement tests using a helical spring specimen in the simulator were used to validate the performance of the simulator model in displacement control. The model was then used to develop a 6 DOF load control system including matrix transformations to ensure correct load tracking.
Results
Model results for displacement control matched the physical test data within 12% and replicated coupling loads. The developed load control model demonstrated good control in all 6 axes, maintaining zero-commanded loads. Furthermore, peak-to-peak errors in non-zero-commanded loads and moments were below 10% and 15% respectively.
Conclusions
The computational model proved a valuable tool in understanding the assembly and functioning of the spine simulator. The in-silico development and validation of the 6 DOF load control system will allow seamless implementation of load control within the spine simulator. The ultimate outcome of this will be the ability to assess the behaviour of FSUs subjected to biofidelic loading conditions.
