Research On Key Technologies Of The Ophthalmic Surgical Instruments With Micro-force Sensing

Ophthalmic microsurgery needs to perform the precise and complicated operation on the fragile tissue of the eye within a narrow space.Moreover,partial surgical procedures are too complicated that exceeds the physiological limits of the surgeons.This causes that the high risk of ophthalmic microsurgery and the difficulty of partial surgical procedures.Integration of robotic technology into microsurgery brings a breakthrough opportunity for ophthalmic microsurgery.This thesis follows the international cutting-edge hotspots of ophthalmic microsurgery robots and conducts some research on key technologies and design theories of robot-assisted ophthalmic microsurgery.The main research contents of the thesis are as follows:1.Aiming at the problem that the operation force of ophthalmic microsurgery is too small for the surgeon to be felt,this thesis reports a miniature 3-DOF force sensing unit with an outer diameter of 1 mm.The miniature 3-DOF force sensing unit could detect both transverse and axial forces based on the FBG sensors.To improve the axial force sensitivity,a helical slots structure was adopted.Based on the static model of the force sensing unit,the relationship between the 3-D forces and the applied strain of FBG fibers was built.To reduce the temperature effect on force measurement,a force decoupling method with temperature compensation was devised.The experimental results showed that the miniature 3-DOF force sensing unit could achieve a resolution of 0.17 m N and 0.47 m N for transverse forces and axial forces,respectively.2.The miniature 3-DOF force sensing unit lacks a central channel,thus cannot integrate with the microneedle.This thesis presents a novel 3-DOF force sensing microneedle with a hollow channel.In this design,three fibers with dual FBGs were attached to the outer surface of the Nitinol tube,thus the central channel of the Nitinol tube could be kept for injection.Based on the novel FBG configuration,a new force computation methodology was devised to decouple the transverse forces and axial forces.Meanwhile,we proposed an improved temperature compensation method based on the idea of the different FBG’s temperature sensitivity is linearity.This temperature compensation algorithm provided a general analytic method for this type FBG configuration.The proposed force sensing microneedle had an outer diameter of 1.1mm.The experimental results showed that the force sensing microneedle could achieve a resolution of 0.124 and 0.74 m N for transverse forces and axial forces,respectively.3.Aiming at the problem that exists ophthalmic surgical instruments lack dexterity,this thesis reports a dexterous flexible continuum manipulator based on the notched superelastic Nitinol tube.This thesis presented a general design method of flexible continuum manipulator based on the notched Nitinol tube.The wire actuation system was also included in this thesis.Considering the friction and deformation of actuation wires as well as the fabrication tolerance of the flexible dexterous mechanism,a statistical model was used to describe the kinematic model of the dexterous manipulator.The dexterous manipulator had a length of approximately 5.6 mm and a diameter of1.2 mm.The maximum bending angle was more than 45°.Finally,we integrated the miniature 3-DOF force sensing unit into the dexterous manipulator to achieve both force sensing ability and dexterity.4.Aiming at the problem that the high costs and lack of surgeon’s intuition of the master-slave robot,a low-cost hand-held active tremor compensation instrument was proposed to reduce the hand physiological tremor.A fully 3D print flexure-based integrated parallel mechanism actuated by piezoelectric ceramics was proposed.The flexure-based structure has the advantage of avoiding backlash and enhancing motion accuracy.A customized BMFLC filter was used to inhibit the integral drift of the inertial sensing unit and calculate the physiological tremor motion.Bench test and hand-held test results showed that the magnitudes of physiological tremor had a significant reduction,which demonstrated the effectiveness of the active tremor compensation instrument.5.This thesis presents an isomorphic master-slave ophthalmic surgical robot that could detect the small operation forces during microsurgery and give force feedback to the surgeon.A hierarchical control strategy of master-slave motion control and force feedback control was proposed,which could effectively ensure the transparency of the control system.Experimental results showed that the response time of the master-slave surgical robot was approximately 120 ms,which met the requirement of the surgical robot.Membrane peeling experiment showed that the peak value of the operating force was significantly reduced when the force feedback function of the master-slave robot was ON.This thesis focuses on the key technologies of three degrees of freedom of force sensing,flexible manipulator and tremor compensation for ophthalmic surgical instruments,and the author developed a series of ophthalmic surgical instruments to help doctors break through the physiological bottlenecks and improve the surgical operation ability.Experimental results have demonstrated the performance of the proposed ophthalmic microsurgery instruments and it showed an excellent potential for large-scale clinical applications.