A Study on the Development of Surgical-Operation-By-Wire (SOBW) for Advanced Surgical Robot System

학위논문 (박사)-- 서울대학교 대학원 : 협동과정 바이오엔지니어링전공, 2015. 8. Sungwan Kim.기존의 개복 수술에 비해 최소 침습 수술은 많은 장점이 있다. 하지만 기존 복강경 도구를 이용한 최소 침습 수술의 한계를 극복하고자 로봇을 이용한 복강경 수술이 널리 시행되고 있다. 하지만 대표적인 복강경 수술 로봇인 다빈치 로봇의 경우 엔드이펙터의 집게가 다양한 자세에서 균일한 힘을 내지 못하는 것이 다른 연구진에 의해 밝혀졌다. 본 연구에서는 이를 가설로 두고 이를 구체적인 실험으로 규명하였으며, 문제의 원인이 금속 줄로 제어되는 엔드이펙터 때문임을 증명하였다. 이를 위해 엔드이펙터의 집는 힘, 자세에 따른 커넥터 각도, 전달 토크를 새로이 고안한 토크전달시스템으로 측정하였다. 측정 결과 의사의 균일한 의도에도 불구하고 27가지 자세에서 세가지 엔드이펙터가 모두 다른 힘을 내었으며 최소 1.84배에서 최대 3.37배의 차이가 나는 것을 확인하였다. 이러한 단점을 극복하고자 본 연구에서는 두 가지 측면에서 해결책을 제시하였다. 첫째로, 다빈치의 엔드이펙터 내부 메커니즘을 분석하여 엔드이펙터의 다양한 자세에서 균일한 힘을 내기 위한 보상 힘을 제시하는 모델을 개발하였다. 모델에서 계산되는 값과 실제 값을 비교하여 검증하였다. 토크전달시스템을 통해 얻은 파라미터로부터 10.69-16.25%의 오차 범위 내에서 예측 집는 힘을 계산하는 결과를 도출하였다. 본 모델을 이용하면 기존 다빈치 시스템의 구조적 문제를 소프트웨어적으로 극복하는데 도움을 줄 수 있다. 또한 의사는 엔드이펙터 집게에 작용하는 실제 힘에 대한 정보를 얻을 수 있으며, 마스터 인터페이스에 압력 센서 등이 구비되면 집는 힘을 원하는 대로 조정할 수도 있어서 수술 도중 발생할 수 있는 사고를 미연에 방지 할 수 있다. 둘째로, 다빈치 시스템의 구조적 문제를 근본적으로 해결하기 위하여 새로운 수술 로봇 엔드이펙터 시스템, Surgical-Operation-By-Wire (SOBW)를 개발하였다. 6축 로봇팔을 사용하여 새로운 엔드이펙터와 함께 수술에 쓰일 수 있는 추가의 자유도를 갖추었다. 제안된 수술 로봇 시스템은 항공우주공학기술에 널리 쓰이는 Hands-On-Throttle-And-Stick (HOTAS)을 활용하여 6축 힘/토크 센서가 추가된 iHOTAS 인터페이스를 통해 제어된다. 집게의 반응시간이 0.2초로 계산되었고, 본 시스템을 처음 접하는 참가자가 술기 테스트에서 평균 176초안에 수행하여 300초 컷오프 타임안에 수행할 수 있게 시스템이 잘 구성되었음을 확인하였다. 또한 시스템의 동작 범위는 11,157.0 cm3으로 계산되었다. 다양한 검증을 통해 제안된 수술 로봇 시스템이 실제 수술에 충분히 쓰일 수 있음을 확인하였다.Abstract i List of Tables iv List of Figures vi Contents x 1. Introduction 1 1.1. Robotic Laparoscopic Surgery 1 1.2. End-effectors and Master Interfaces in Robotic Laparoscopic Surgery 8 1.3. Objectives and Scope 12 1.3.1. Gripping Force Measurement for Various Postures and Mathematical Compensation Model 17 1.3.1.1. Torque Transfer System (TTS) 18 1.3.1.2. Calibration of the Sensors 21 1.3.1.3. Force Measurement with Respect to the EndoWrists Posture 23 1.3.2. Novel End-effector and Mater Interface 31 ? 2. Materials and Methods 34 2.1. EndoWrist Inner Mechanism Model 34 2.2. Development of the Laparoscopic Robot 37 2.2.1. Overview 40 2.2.2. External Arm 40 2.2.3. End-effector (KS-4) 42 2.2.3.1. Pneumatic Gripper System 48 2.2.4. Forward Kinematics of the System 53 3. Results 58 3.1.Prediction of the Compensation Force for EndoWrists 58 3.1.1. EndoWrists Gripping Force 58 3.1.2. Prediction Results and Validation 60 3.2. Pneumatic Type of End-effector (KS-4) and Novel Master Interfaces 63 3.2.1. End-effectors Gripping Force 63? 3.2.1.1. Gripping Force System Setup 63 3.2.1.2. Relationship between Compressors Pressure and Gripping Force 66 3.2.1.3. Reaction Time 68 3.2.1.4. Durability Test 71 3.2.2. Simple Peg Task 72 3.2.3. Workspace 76 3.2.4. System Specification 77 4. Discussion 80 5. Conclusion 89 References 90 Abstract in Korean 100Docto

Force Sensing Surgical Scissor Blades using Fibre Bragg Grating Sensors

This thesis considers the development and analysis of unique sensorised surgical scissor blades for application in minimally invasive robotic surgery (MIRS). The lack of haptic (force and tactile) feedback to the user is currently an unresolved issue with modern MIRS systems. This thesis presents details on smart sensing scissor blades which enable the measurement of instrument-tissue interaction forces for the purpose of force reflection and tissue property identification. A review of current literature established that there exists a need for small compact, biocompatible, sterilisable and robust sensors which meet the demands of current MIRS instruments. Therefore, the sensorised blades exploit the strain sensing capabilities of a single fibre Bragg grating (FBG) sensor bonded to their surface. The nature and magnitude of the strain likely to be experienced by the blades, and consequently the FBG sensor, while cutting soft tissue samples were characterised through the use of an application specific test-bed. Using the sensorised blades to estimate fracture properties is proposed, hence two methods of extracting fracture toughness information from the test samples are assessed and compared. Investigations were carried out on the factors affecting the transfer of strain from the blade material to the core of the FBG sensor for surface mounted or partially embedded arrangements. Results show that adhesive bond length, thickness and stiffness need to be carefully specified when bonding FBG sensors to ensure effective strain transfer. Calibration and dynamic cutting experiments were carried out using the characterisation test-bed. The complex nature of the blade interaction forces were modelled, primarily for the purpose of decoupling the direct, lateral, friction and fracture strains experienced by the bonded FBG sensor during cutting. The modelled and experimental results show that the approach taken in sensorising the blade enables detailed cutting force data to be obtained and consequently leads to a unique method in estimating the kinetic friction coefficient for the blades. The forces measured using the FBG are validated against a commercial load cell used in the test-bed. This research work demonstrates that this unique approach of placing a single optical fibre onto the scissor blades can, in an unobtrusive manner, measure interblade friction forces and material fracture properties occurring at the blade-tissue interface

Characterization of soft tissue cutting for haptic display: experiments and computational models

Real-time medical simulation for robotic surgery planning and surgery training requires realistic yet computationally fast models of the mechanical behavior of soft tissue. This work presents a study to develop such a model to enable fast haptics display in simulation of softtissue cutting. An apparatus was developed and experiments were conducted to generate force-displacement data for cutting of soft tissue such as pig liver. The force-displacement curve of cutting pig liver revealed a characteristic pattern: the overall curve is formed by repeating units consisting of a local deformation segment followed by a local crack-growth segment. The modeling effort reported here focused on characterizing the tissue in the local deformation segment for fast haptic display. The deformation resistance of the tissue was quantified in terms of the local effective modulus (LEM) consistent with experimental forcedisplacement data. An algorithm was developed to determine LEM by solving an inverse problem with iterative finite element models. To enable faster simulation of cutting of a threedimensional (3D) liver specimen of naturally varying thickness, three levels of model order reduction were studied. Additionally, the variation of the LEM with cutting speed was determined. The values of LEM decreased as the cutting speed increased. This thesis also includes the characteristic response of soft tissue to the growth of a cut (cracking) with a scalpel blade. The experimentally measured cut-force versus cut-length data was used to determine the soft tissue’s resistance to fracture (resistance to crack extension) in scalpel cutting. The resistance to fracture of the soft tissue is defined as the amount of mechanical work needed to cause a cut (crack) to extend for a unit length in a soft-tissue sample of unit thickness. The equipment, method, and model are applicable for all soft tissue.Finally, the method of determining the property of the pig liver tissue during cutting was verified. Dual C-arm fluoroscopes were used to obtain the motion of the beads embedded inside the specimen during cutting. The experimentally measured displacement field was compared to the displacement field obtained through finite element model based on the LEM values at each localized area.Ph.D., Mechanical Engineering and Mechanics -- Drexel University, 200

Variational methods for modeling and simulation of tool-tissue interaction

Ph.DDOCTOR OF PHILOSOPH

Measurement, Analysis and Display of Haptic Signals during Surgical Cutting

The forces experienced while surgically cutting anatomical tissues from a sheep and two rats were investigated for three scissor types. Data were collected in situ using instrumented Mayo, Metzenbaum, and Iris scissors immediately after death to minimize post-mortem e#ects. The force-position relationship, the frequency components present in the signal, the significance of the cutting rate, as well as other invariant properties, were investigated after segmentation of the data into distinct task phases