This work presents a novel rolling driving principle (RDP) for stick-slip actuators to achieve high motion consistency, inspired by the rack-and-pinion mechanism. This RDP utilizes a symmetrical driving structure and tangential contact to realize the pure rolling motion between the stator and the slider, requiring just a single lead zirconate titanate (PZT). This configuration ensures a consistent bidirectional driving process with a constant contact force, which improves both motion consistency and linearity. Based on this RDP principle, a linear stick-slip actuator incorporating an isosceles trapezoidal flexible mechanism (ITFM) has been implemented. The corresponding driving principle, operating principle, and the RDP’s advantages have been analyzed and revealed. Design optimization was performed to investigate the optimal structural parameters of the ITFM. The superior performance of the proposed RDP-type actuator was experimentally verified across both high- and low-frequency ranges. The results indicate that the presented design exhibits forward and reverse output speed values of 0.410 and 0.417 mm/s at 10 Hz with linear correlation coefficients of 0.99969 and 0.99962, indicating an excellent motion consistency with a velocity difference ratio of 1.96%. When working at 560 Hz, the presented actuator reaches 37.73 and 34.99 mm/s for the forward and reverse output speed, yielding high linearity values of 0.99999 and 0.99999 due to the tiny speed fluctuation, and maintains a reasonable motion consistency with a velocity difference ratio of 7.54%. Finally, an RDP-type actuator-based magnetic resonance imaging (MRI)-compatible microsurgical instrument was proposed and prototyped, which enables opening–closing motions and cutting motions for intraoperative MRI surgical applications.

Continuum manipulators can conform to curvilinear paths and manipulate objects in complex environments, which makes it emerging to be applied in minimally invasive surgery (MIS). However, different and controllable operating stiffness of the continuum manipulator is required during different stages of surgery to achieve safe access or stable and precise operation. This work proposes an operating stiffness controller (OSC) for the typical tendon-driven continuum manipulator based on the variable impedance control method with Lagrangian dynamic modeling. This controller can adjust the operating stiffness by modifying the driving forces along the driving tendons of the continuum manipulator without changing its material or structure. The proposed OSC converts the damping and stiffness matrices of the impedance control into variable parameters. This merit allows it to dynamically adjust the operating stiffness of the continuum manipulator according to the desired constant or time-varying stiffness. Furthermore, the OSC stability can be proven based on a Lyapunov function, and its stiffness control performances have been analyzed and evaluated in both simulations and experiments. The OSC controller generated average relevant error values of 7.82% and 3.09% for the operating stiffness control experiments with constant and time-varying desired stiffness, respectively. These experimental results indicate that the OSC has high accuracy, stability, and strong robustness in the operating stiffness control tasks.

This work presents a novel electromagnetic driving system that consists of eight optimized electromagnets arranged in an optimal configuration and employs a control framework based on an active disturbance rejection controller (ADRC) and virtual boundary. The optimal system configuration enhances the system’s compatibility with other ophthalmic surgical instruments, while also improving its capacity to generate magnetic force in the vertical direction. Besides, the optimal electromagnet parameters provide a superior comprehensive performance on magnetic field generation capacity and thermal power. Hence, the presented design achieves a stronger capacity for sustained work. Furthermore, the ADRC controller effectively monitors and further compensates the total disturbance as well as gravity to enhance the system’s robustness. Meanwhile, the implementation of virtual boundaries substantially enhances interactive security via collision avoidance. The magnetic and thermal performance tests have been performed on the electromagnet to verify the design optimization. The proposed electromagnet can generate a superior magnetic field of 2.071 mT at a distance of 65 mm with an applied current of 1 A. Moreover, it demonstrates minimal temperature elevation from room temperature (25 °C) to 46 °C through natural heat dissipation in 3 h, thereby effectively supporting prolonged magnetic manipulation of intraocular microsurgery. Furthermore, trajectory tracking experiments with disturbances have been performed in a liquid environment similar to the practical ophthalmic surgery scenarios, to verify the robustness and security of the presented control framework. The maximum root mean square (RMS) error of performance tests in different operation modes remains 35.8 μm, providing stable support for intraocular microsurgery.