Microscale Precision Control of a Computer-Assisted Transoral Laser Microsurgery System

Abstract

In a recent advance in surgery, a computer-assisted laser microsurgery system has demonstrated its suitability for transoral operations. Thanks to its motorized micromanipulator setup, surgeons can perform delicate operations on lesions in the larynx using an intuitive user interface. The major hurdle to ensure surgical quality is to guarantee $\mu$ m-scale precision in the control of the laser beam (spot diameter 110–250 $\mu$ m), because the mechanism includes inherent discontinuous nonlinearities such as Coulomb friction and stiction and unavoidable modeling uncertainties. To this end, in this article, a precise position controller directly creating a voltage command is newly proposed by amalgamating two robust control concepts—a generalized super-twisting algorithm (GSTA) and a model-free compensation method called time-delay estimation (TDE). Fast convergence in finite time is proved in the Lyapunov sense. The experimental results verify that the proposed controller can satisfy the precision requirement of 55 $\mu$ m, while the efficacy is validated by comparisons with respective GSTA- and TDE-based controllers. As a practical performance–safety guideline for users, we benchmark the tracking precision of the proposed controller with respect to operation speeds.