Design and Control of a Compact Electromagnetically Driven Laser Scanner for Robotic-Assisted Endoscopic Microsurgeries

摘要

The fiber-guided laser scanner has been widely adopted in endoscopic microsurgeries due to its outstanding precision, swiftness, and dexterity for incision, ablation, and photocoagulation of some difficult-to-reach tissues, e.g., the laryngeal, respiratory, and alimentary sites. However, fabricating and actuating such precision surgical instruments are challenging, considering the strictly limited workspace and the high-performance requirements. This article proposes a compact fiber-guided laser scanner with two rotational degrees of freedom (DOFs), one of which is actuated with the stepper motor and the other controlled by electromagnetism. The novel design of the electromagnetically driven system allows the laser scanner for a more compact radial dimension while maintaining high precision in trajectory tracking tasks. In addition, we develop a robust control strategy based on visual feedback to achieve autonomous detecting and tracking of the trajectory targets. In vitro tests are subsequently performed to validate the efficacy and accuracy of our proposed system. The experimental results reveal that the average tracking error of our laser steering system is as low as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ {279.29~{\mu~{\mathrm {m}}}}$ </tex-math></inline-formula>, which is deemed satisfactory in practical endoscopic microsurgeries. Note to Practitioners—This article is motivated by the unmet needs of in vivo laser endoscopic microsurgery in an automated fashion, and simultaneously the proposed methodology can be applied to other laser scanning-related scenarios. Existing solutions to in vivo laser scanning generally are associated with complex micro-electromechanical systems (MEMS), and hence high costs and relatively bulky footprint. Moreover, existing manual control schemes cannot enable high-precision laser scanning in an automated fashion. This article demonstrates a novel approach incorporating mechanism and electromagnetism to actuate the laser scanner, whereby achieving a highly compact design at low costs. Further, a closed-loop control strategy is developed for such an electromagnetically driven laser scanner, enhancing its scanning accuracy and reliability. This article theoretically analyzes the mechanics and electromagnetics of the laser scanner. Subsequently, it proposes a closed-loop control scheme through endoscopic visual feedback, allowing the laser scanner for autonomous target tracking. The pilot in vitro experiments demonstrate the feasibility and reliability of this holistic approach. Ultimately, the design and control of the electromagnetically driven laser scanner would be further optimized and validated for its laser ablation performance on ex vivo tissues or animal models in the future.