Loveless, Amy L
(2003)
DELINEATION OF IN-VITRO SPINAL KINETICS USING A ROBOTICS-BASED TESTING SYSTEM.
Master's Thesis, University of Pittsburgh.
(Unpublished)
Abstract
Delineation of the load-displacement characteristics of osteoligamentous spinal specimens has become fundamental to the investigation of spinal biomechanics. Traditionally, in-vitro kinetic parameters of the spine have been obtained through flexibility tests employing open or closed loop "load control" methods, or stiffness tests employing "displacement control" methods-each control method having attendant advantages and disadvantages. On the other hand, the combination load control and displacement control methods into a new, "hybrid control" method have advantages over load control or displacement control alone. Further, physical evidence such as presence of certain receptors suggests that the human body may employ a type of hybrid control method in the control of spinal movements.In the present study, a robotics-based spine testing system with hybrid control was developed to delineate the in-vitro kinetics of lumbar spine specimens. The testing system was validated experimentally using a physical rigid-body-spring model of a spine specimen, as well as analytically by computer simulations in Matlab. For systematic study, the two components making up a hybrid control algorithm were analyzed separately: the outer "displacement control" loop, and the inner "load control" loop. The outer loop applies a rotation (e.g., flexion/extension) to the specimen, while the inner loop minimizes unwanted coupled forces (e.g., anterior/posterior shear and axial tension/compression).The performance of existing standard hybrid control algorithms was tested in terms of a number of parameters, including peak force, work done to a specimen, and number of iterations. Based on these tests, a number of proposed changes to improve algorithm performance were identified. Updating the user-defined center of rotation (COR) to reflect a specimen's COR was found to improve performance of the displacement control part of the hybrid control algorithm, while using a more completely populated stiffness matrix improved performance of the load control part. The re-combination of the displacement control and load control loops into the fully constituted hybrid control algorithm revealed interesting interactions between these control components that suggest a basis for spinal dysfunction.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
| Title | Member | Email Address | Pitt Username | ORCID |
|---|
| Committee Chair | Gilbertson, Lars G | larss@pitt.edu | LARSS | | | Committee Member | Kang, James D | | | | | Committee Member | Smolinski, Patrick J | | | | | Committee Member | Cham, Rakie | | | |
|
| Date: |
3 September 2003 |
| Date Type: |
Completion |
| Defense Date: |
22 July 2003 |
| Approval Date: |
3 September 2003 |
| Submission Date: |
7 August 2003 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Bioengineering |
| Degree: |
MSBeng - Master of Science in Bioengineering |
| Thesis Type: |
Master's Thesis |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
rigid body kinematics |
| Other ID: |
http://etd.library.pitt.edu:80/ETD/available/etd-08072003-120101/, etd-08072003-120101 |
| Date Deposited: |
10 Nov 2011 19:57 |
| Last Modified: |
15 Nov 2016 13:48 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/8956 |
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