Research On Key Techniques Of Cranio-Maxillofical Plastic Surgical Robot

Craniomaxillofacial surgery makes partition movement of the craniomaxillofacial bone to achieve the purpose of correction of craniomaxillofacial deformity in terms of traction osteogenesis,osteotomy and repositioning bone transplantation and other methods.However,the difficulty of the surgery is mainly manifested in the complex anatomical regional structure,the vital surrounding vascular and nerves,stenosis or almost blind vision of the surgical field,physiological tremor and long-term operation of fatigue of the surgeon.The surgery is very dependent on the accuracy.Traditional surgical procedures are difficult to meet the accuracy requirements due to technical defects,making them relatively risky relative to other surgical procedures,and the technical threshold is relatively high.In this paper,we designed a novel craniomaxillofacial surgerical robotic system.The following research work is carried out.1.In view of the complex anatomical structure of craniomaxillofacial surgery,the surgical field is not easy to expose,prone to damage the nerve and blood vessels or other structures.Although the ordinary optical navigation system has a high positioning accuracy,but it needs to implant the optical markers into the patient,and this is invasive.Therefore,this paper presents a non-invasive way,that is,the use of dental occlusal markers builds a suitable AR navigation system for craniomaxillofacial surgery.The matching algorithm mathematical model(Lip ICP)between the three-dimensional virtual image information and the actual image is emphatically proposed,and the high matching accuracy of the model is verified combining with the simulation experiment by comparing with other ICP algorithms.2.For the reason of the results of plastic surgery depends on the doctor's clinical experience and skills,misuse caused by hand tremor of the surgeons and intraoperative damage to the important vascular nerves,this paper aims to develop a craniomaxillofacial surgical robotic system with force feedback,taking the mandibular plastic surgery as the starting point.Therefore,the first craniomaxillofacial surgical robot(CPSR-I)prototype was designed.Then,drilling and otestomy test of the dogs' mandible was performed with AR navigation system.The result shows that the design of CPSR-I system is reasonable and meets the accuracy requirements of the clinical mandibular plastic surgery.3.In order to achieve the precise surgical operation of complex plastic surgery,the second craniomaxillofacial plastic surgeical robotic(CPSR-II)system was developed on the basis of comprehensive analysis of CPSR-I robot structure design.Firstly,the design scheme of the whole robot is discussed in detail.The mechanism design,the degree of freedom design and the design of the end of the actuator is discussed in detail.The model experiment shows that the robot system realizes the operation of five degrees of freedom.The motion of the robot system is stable and accurate,and the force feedback can be monitored in real time,which enhances the safety of the operation.4.In order to achieve accurate robot motion control and ensure the accuracy and safety of plastic surgery,the robot coordinate system is established according to the DH theory.The forward kinematics and inverse kinematics of the robot are given,analyzed and verified,respectively.And then the motion space of the robot is calculated based on the kinematics equations.The trajectory of the robot is planned by cubic interpolation method and the simulation analysis is carried out.Based on the La-grange's equations,a multi-degree-of-freedom dynamic model of the robot is established,and the accuracy of the model is verified by MATLAB software.5.In order to meet the craniomaxillofacial surgery automatic and accurate drilling and osteotomy,the overall scheme of the robot control system is designed,that is,according to the preoperative planning trajectory to complete the default drilling and osteotomy.The force feedback control strategy can not only real-time monitoring the actual the force feedback information,but also to avoid excessive drilling or damage important vascular tissues.In addition,in order to achieve a stable and rapid-response control system,a force feedback algorithm was designed so that the doctor could monitor the real-time drilling force,which ensures high precision operation and safety.6.In order to comprehensively analyze the performance of the robot system,the experiment is analyzed,including the error analysis,the parameter calibration,the repeated positioning accuracy analysis and the absolute positioning accuracy analysis,which further improves the whole robot system.