To possess sufficient compliance while keeping an acceptable stiffness level for manipulation with precision, transoral robotic surgery (TORS) demands a flexible robotic system with variable stiffness (VS) as presented in this paper. In our study, a flexible three-prismatic-universal parallel mechanism employs superelastic nickel-titanium rods to achieve compliant movements beyond the conventional rigid-body parallel mechanisms. With a compact structure and flexible-shaft transmission, the adjustable tube-based VS mechanism allows the stiffness of the manipulator to be continuously tuned in real time according to the surgical requirements. A stiffness model is derived to evaluate the stiffness of the manipulator quantitatively. A parallel mechanism with three prismatic-revolute-spherical chains is adopted as the master device, to improve the maneuverability and decrease the learning curve for less experienced surgeons. The TORS manipulators are characterized and verified in the laboratory and cadaveric trials, showing the VS and the execution of the master-slave teleoperated configuration. Furthermore, the cadaveric trials attested the effectiveness of the VS mechanism and the preclinical feasibility of the robotic system.

中文翻译：

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经口手术中可变刚度的柔性机器人

为了拥有足够的依从性，同时保持可接受的硬度水平以进行精确的操纵，经口机器人手术（TORS）需要具有可变硬度（VS）的灵活机器人系统，如本文所述。在我们的研究中，一种灵活的三棱柱通用并联机构采用超弹性镍钛棒实现了超越常规刚体并联机构的顺应运动。具有紧凑的结构和灵活的轴传动装置，基于管的可调式VS机构允许根据手术要求实时连续地调节机械手的刚度。推导了刚度模型以定量评估机械手的刚度。主装置采用三棱柱形旋转球面链的并联机构，对于缺乏经验的外科医生来说，可以提高可操作性并减少学习曲线。TORS机械手已在实验室和尸体试验中进行了表征和验证，显示了VS和主从遥控操作的执行情况。此外，尸体试验证明了VS机制的有效性以及机器人系统的临床前可行性。