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PhD Preliminary Examination

I gave my prelim presentation this past January, recapping my work with Prof. Zinn on Interleaved Continuum-Rigid Manipulation. The presentation went well and I enjoyed the audience’s and committee’s questions, most of which centered on things that would be very fun to look at given infinite time. As I hope to graduate soon, I’ll only be able to look into a few of the most fundamental questions, saving others for later students. With that, here are links to my document and narrated slides, followed by the prelim’s abstract:

Preliminary Thesis [45MB PDF]

Slides [6.1MB PDF]

Prelim Presentation from Ben Conrad on Vimeo. (and on YouTube)


Continuum manipulator compliance enables operation in delicate environments at the cost of challenging actuation and control. In the case of catheter ablation of atrial fibrillation, the compliance of the continuum backbone lends an inherent safety to the device. This inherent safety frustrates attempts at precise, accurate, and fast control, limiting their use to simple, static positioning tasks. This preliminary work develops Interleaved Continuum-Rigid Manipulation, by which the hysteretic nonlinearities encountered in tendon-actuated continuum manipulators are compensated by discrete rigid joints located between continuum sections. The rigid joints introduce actuation redundancy, which an interleaved controller may use to avoid continuum nonlinearities and dynamic excitations, or to prefer particular configurations that may improve task accuracy, permit greater end-effector forces, or avoid environment obstacles. Two experimental systems explore the potential of these joints to 1) correct for actuation nonlinearities and enhance manipulator performance and 2) increase the manipulator’s dexterous workspace. These experiments also expose important design and control observations that were not apparent in the general robotic and continuum literature.

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