Research On The Teleoperation Motion Control Strategy For A Master-slave Minimally Invasive Surgical Robot

In recent years, the minimally invasive surgical (MIS) robot has become a hot topic in themedical robotics research field. Owing to its special mechanism and the using of advancedrobotic technology, MIS robots can overcome the deficiencies of traditional MIS instruments,significantly enhance the ability of the surgeon and assist them carry out surgery with higherquality and safety. Besides, MIS robots can bring the advantages of minimally invasive surgeryinto full play and enable the application of the MIS technology in more precise surgery. Hence,it is receiving more and more attention and will have a wider application prospect in the future.Usually, a master-slave MIS robot consists of a master control console and several slaverobot manipulators, on the end of which different surgical instruments can be mounted. Duringrobot-assisted minimally invasive surgery, the surgeon controls the motion of the slave surgicalmanipulator insides the patient through teleoperation technology, that means the surgeon onlyneeds to sit by the master console and performs different operation actions with the inputhandles, the instruments on the slave manipulator will move in the same direction as thesurgeons’ hands. Every movement of the surgeon’s hands will be completely and faithfullyreproduced by the slave manipulator during the entire surgery. Supplemented with the real-timeimage of the surgical anatomy, the surgeon can perform various operation actions remotely. Fora MIS robotic system, the master-slave control system directly determines its user experience’squality. Hence, the design of the master-slave teleoperation control system is of greatimportance to the development of a MIS robotic system.This dissertation mainly focuses on the degisn of a teleoperation system for a master-slaveMIS robotic system. Studies and researches are conducted targeting at some major issuesconcerned, such as the real-time feature, the naturality (the intuitiveness), the safty andreliability of the teleoperation system. Based on which, a complete set of design methodology for the master-slave medical teleoperation system is formed and introduced. Furthermore, asoftware and a hardware platform are designed and developed to verify the effectiveness of theproposed methods. The specific contents of this dissertation are listed as follows:(1) In order to realize a real-time telemanipulation of a common isomeric master-slave MISrobotic system, first its kinematic models, including the master and slave surgical manipulator’skinematic model, are obtained respectively. Based on which, all the explicit analyticalexpressions of the kinematic solutions can be solved. Among them, it’s relatively complex toget the explicit analytical solution of the slave surgical manipulator since its structure doesn’tmeet the the Pierper Principle. In consideration of the MIS robot’s special structure, a two-stepsapproximation algorithm is proposed, by which only few simple calculations are needed to getall the approximate analytical solutions to the slave manipulator’s IK problem. Combining withthe error compensation method, we can easily realize precisely and real-time control of anyMIS slave manipulators, whose structure doesn’t meet the the Pierper Principle.(2) To realize a natural and intuitive telemanipulation of a common isomeric master-slaveMIS robotic system, how to design the translational and the orientational movementrelationship between the master and slave manipulators is discussed. For different MIS roboticsystems, their master consoles varies from each other (with different kinds of layout). Hencefirst, we build a universal abstract model that can describe the tele-manipulation process usingdifferent master consoles. Then based on this model, we propose a hand-eye-coordinationprinciple based master-slave motion aligning method, which can maximally ensure the hand-eye-coordination of the operator (to realize “How You Move Is What You See”) and try to givethe surgeon the same feeling as carrying out an open surgery, which is crucial to the comfortnessof the surgical telemanipulation.(3) Due to lack of tactile feedback in most robot-assisted MIS systems, the surgeon canonly get limited visual information of the pathological area. Sometimes, especially when theoperating volume area is very narrow, the surgeon might unconsciously move the surgical instrument excessively, which might lead to unexpected collisions between the slavemanipulator and the vulnerable organs around the lesion and cause damage to them, in severecases even life-threatening. To prevent this from happening, a new virtual fxture based solutionis proposed, which is more convenient and easy-to-use compared to the traditional methods.The surgeon can easily define some virtual fixtures as needed before or even during surgery.These generated virtual fixtures will be used to constrain the robot’s spatial motion to preventany unexpected collision (and damage). In this way, those important organs/tissues near thepathological area can be well protected during the entire surgical operation, which makes therobot-assisted minimally invasive surgery safer and more reliable.(4) A virtual simulation and a hardware experiment platform of the MIS robot are built.The above introduced methods are packaged into different function modules and applied in theexperiment platforms. Some manipulation tasks are conducted to verify the effectiveness of theproposed methods. The experiment results show that the realized master-slave teleoperationsystem works as expected.This dissertation’s research on the precisely, real-time control of a MIS robot and its master-slave motion aligning method basically covers the major key technical issues related to thedesign of a MIS robot’s master-slave teleoperation control system. In addition, the customizablevirutual fixtures based spatial motion constrained method can further improve the safty andreliability of robot-assisted minimally invasive surgery. Based on these research results, we candesign and develop a real-time, intuitive and safe teleoperation system for any isomeric master-slave MIS robots. Moreover, the herein proposed methods can also be conveniently applied toany other existing MIS robotic systems.