Robotic compensation of cerebellar ataxia

The cerebellum is believed to play a role in dynamic compensation in the human motor control system. When it is damaged, subjects make clumsy movements with reduced acceleration, increased overshoot, and swerving in multi-joint movements. These errors, which are referred to clinically as ataxia, are consistent with failing to compensate for the dynamics of the body, especially its inertia during high speed movements. We have developed a robotic system that is capable of dynamically canceling some of the inertial effects in order to reduce the severity of ataxia. This compensator is designed by modeling the closed loop behavior of a subject coupled to a robotic manipulandum. The model is used to solve for the controller needed to produce dynamics in which the inertia of the subject's limb is effectively reduced. The performance of the inertial compensator was tested on both real subjects and a mechanical model designed to reproduce the primary features the subjects' dynamics. The mechanical model provides known and consistent dynamics which facilitates analysis of the compensator performance. The mechanical model confirmed the functionality of the inertial compensator by demonstrating an increase in both the natural frequency and damping ratio of the mechanical model's mass-spring-damper like dynamics. The effect of the inertial compensator on subjects with cerebellar ataxia was measured by their performance on a timed tracing task. The subject with pure ataxia showed a significant improvement in tracing accuracy under inertial compensation, when compared with uncompensated motions.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2007

Author dc:creator

• Smith, Eric D., S.M. Massachusetts Institute of Technology

Advisor dc:contributor.advisor

• Steve G. Massaquoi.

• Mechanical Engineering.
• Electrical Engineering and Computer Science.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/42311

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/42311