WO2020034145A1 - 腹腔微创外科机器人虚拟手术方法 - Google Patents

腹腔微创外科机器人虚拟手术方法 Download PDF

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WO2020034145A1
WO2020034145A1 PCT/CN2018/100822 CN2018100822W WO2020034145A1 WO 2020034145 A1 WO2020034145 A1 WO 2020034145A1 CN 2018100822 W CN2018100822 W CN 2018100822W WO 2020034145 A1 WO2020034145 A1 WO 2020034145A1
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force
surgical
point
simulation
virtual
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PCT/CN2018/100822
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English (en)
French (fr)
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张峰峰
吴昊
陈军
孙立宁
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苏州大学张家港工业技术研究院
苏州大学
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Publication of WO2020034145A1 publication Critical patent/WO2020034145A1/zh

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/10—Computer-aided planning, simulation or modelling of surgical operations
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/10—Computer-aided planning, simulation or modelling of surgical operations
    • A61B2034/101—Computer-aided simulation of surgical operations
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/10—Computer-aided planning, simulation or modelling of surgical operations
    • A61B2034/101—Computer-aided simulation of surgical operations
    • A61B2034/102—Modelling of surgical devices, implants or prosthesis
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/10—Computer-aided planning, simulation or modelling of surgical operations
    • A61B2034/101—Computer-aided simulation of surgical operations
    • A61B2034/105—Modelling of the patient, e.g. for ligaments or bones

Definitions

  • the invention relates to a virtual surgery method of a minimally invasive surgical robot for abdominal cavity.
  • Virtual reality technology is a computer simulation system that can create and experience a virtual world. It takes computer technology as the core and combines a variety of related technologies to generate an interactive environment with high myopia in sight, hearing, and touch. It provides users with an immersive feeling and can observe in a three-dimensional space without restrictions. Things.
  • Virtual surgery is a typical application of virtual reality technology in the medical field. As a new research direction, it is a new research area that integrates many disciplines such as biomechanics, mechanics, medicine, robotics and so on.
  • Virtual surgery is a surgical system that starts from medical image data, establishes a virtual surgical environment in a computer, then builds a human tissue model, and interacts with it using force-tactile interaction equipment. Doctors can use the information in the virtual surgery environment for surgical planning, surgical training, surgical rehearsal, and guided surgery during actual surgery.
  • Minimally invasive surgical robots have become a research hotspot in the field of medical robots. It combines traditional medical equipment with information technology and robotics to enable surgical diagnosis and treatment to be minimally invasive, miniaturized, intelligent and digital. Compared with traditional surgery, minimally invasive surgical robots have significant advantages: minimally invasive robotic surgery can improve the doctor's working mode, making doctors more dexterous, more convenient, more accurate when performing surgery, and even allows surgery in two different fields The doctor performs two related operations at the same time; in addition, even if the operation is performed for a long time, the minimally invasive surgical robot will not tremble because of exhaustion like a human hand, which greatly improves the quality of the operation and prolongs the professional life of the surgeon; minimally invasive surgery The robotic surgical wound is only about 1 cm, which greatly reduces the blood loss and postoperative pain of the patient, and the patient recovers quickly. The wound of the large intestine and stomach only needs five to seven days to heal, and the wound of the skin is only one or two days.
  • an object of the present invention is to provide a virtual surgery method of a minimally invasive surgical robot for abdominal cavity.
  • a virtual surgery method for a minimally invasive surgical robot for abdominal cavity which includes the following steps:
  • a Set up a virtual surgery simulation platform, including designing a robot model with a parallelogram telecentric positioning mechanism, performing kinematic analysis on the robot model, solving the forward and inverse kinematics of the telecentric positioning mechanism, and applying force feedback equipment to the virtual robot. Operational control
  • the suture simulation process of the surgical object is realized.
  • the robot model includes a frame and at least one robotic arm, and each robotic arm includes a first slider connected to the frame vertically through a first sliding joint, and is rotated with the first slider through a first rotary joint.
  • a first lever member connected, a second lever member connected to the first lever member through a second rotation joint, a third lever member connected to the second lever member through a third rotation joint, and a fourth rotation joint A pivot member pivotally connected to the third lever member, a first link rotationally connected to the pivot member through a fifth rotation joint, and a second link rotationally connected to the first link through a sixth rotation joint
  • the lever, the second link, and the third link constitute a parallelogram mechanism.
  • setting up a virtual surgery simulation platform in step a further includes adding at least one camera in the virtual surgery environment, and controlling the position and orientation of the camera through mouse operation to realize the movement and rotation of the virtual surgery environment; adding control buttons on the control panel It realizes the switching of the perspective and resets the position of the visual point.
  • step b the force balance calculation method is determined according to the distribution law of the particles. First, it is determined whether the particles meet the stress conditions, and then the distance from the end of the surgical instrument to each particle in the area is calculated. The force feedback during the compression deformation of the surgical object is realized to realize the simulation operation and force interaction of the compression deformation of the surgical object.
  • a physical model of the surgical object is established using the mass point spring method.
  • the single-point force balance calculation method performs calculations to determine whether the adhesion point has reached the force equilibrium state; when the adhesion point has reached the force balance state, the calculation is performed by the single-point force balance calculation method to determine whether the mass around the adhesion point has reached The state of force balance; when the surrounding mass points are in their respective single-point force equilibrium states, the resultant forces of the adjacent points at these points are obtained.
  • the system is in a state of force balance; then, a force feedback calculation is performed, and the position information of the contact point of the clamping tool vertex and the soft tissue surface of the surgical object and the actual position information of the clamping tool vertex are collected.
  • the clamping tool is performing a clamping operation on the simulation model.
  • the adhesion point moves with the clamping tool, and the surgical object model is deformed.
  • the calculation method of the single-point force balance includes: b1. Assuming that the mass point around the point is fixed, calculate the resultant force of the neighboring points, and then obtain the magnitude of the displacement of the point under the action of the force, At this time, calculate the resultant force of the adjacent points of the adhesion point again. If the magnitude of the force is within the allowable error range of the single-point force balance, it is considered that the point has reached the state of force equilibrium; b2.
  • step c the straight line where the two cutting edges on the surgical tool are projected onto the plane where the triangular patch is located in the grid model, to obtain the cutting line segment at the current moment, and through the simultaneous linear equation of space and each triangular patch
  • step d the method of tracking the control points is used to track the trajectory of the line to realize the motion simulation of the line model.
  • the virtual surgical method of the abdominal minimally invasive surgical robot of the present invention establishes a three-dimensional model of the main organs and organs of the abdominal cavity, constructs a virtual surgical environment, sets up a virtual surgery simulation platform, designs a abdominal surgical robot, and It performed kinematic analysis, established a biomechanical model of the internal tissues of the abdominal cavity for minimally invasive surgery, and performed virtual surgery simulation studies such as compression, clamping, cutting, and suture. It can simulate the entire process of the surgery with high accuracy.
  • doctors can repeatedly perform surgical training on surgical patients in a virtual surgery environment, saving the cost of doctor training, shortening the time for surgical training, and improving the proficiency of surgeons in surgery.
  • the establishment of a virtual surgery simulation system can provide doctors with a preview of the surgery and prolong the professional life of the doctor. It can also realize remote assistance and simulation to determine the surgical plan.
  • the virtual operation method of the abdominal cavity minimally invasive surgical robot has great theoretical and practical significance for the operation of the abdominal cavity robot.
  • FIG. 1 is a partial schematic diagram of a virtual environment in a virtual surgery method of a minimally invasive surgical robot for abdominal cavity according to the present invention
  • FIG. 2 is a schematic diagram of a first structure of a robot model in a virtual surgery method of a minimally invasive surgical robot for abdominal cavity according to the present invention, in which only one robot arm is drawn for explanation;
  • FIG. 3 is a schematic diagram of a second structure of a robot model in a virtual operation method of a minimally invasive surgical robot for abdominal cavity according to the present invention, wherein only one robot arm is drawn for explanation.
  • a virtual operation method of a minimally invasive surgical robot for abdominal cavity uses 3DMAX to geometrically model a human abdominal cavity tissue model, a virtual surgical robot, a surgical instrument, and the like, and sets related models. Related parameters such as local coordinates; use Deep Exploration to add relevant information such as materials and textures to these models to increase their authenticity, and finally save and save in .3ds data format.
  • a virtual surgery simulation platform is built by combining the software and hardware equipment involved in the virtual surgery of the abdominal cavity.
  • a robot model with a parallelogram telecentric positioning mechanism which includes a frame and at least one robot arm 100 connected to the frame.
  • Each robot arm 100 includes a position adjustment mechanism and a telecentric mechanism that can be controlled by a control device.
  • Each robot arm 100 has a total of nine joints and nine degrees of freedom.
  • the robot arm 100 includes a first slider 111 that is connected to the frame 300 through a first sliding joint to move up and down, and is rotatably connected to the first slider 111 through a first rotary joint.
  • the fourth rotation joint is pivotally connected to the third lever member 114 by a pivoting member 115, the first link 116 is rotationally connected with the pivot member 115 through a fifth rotation joint, and the first link is connected through a sixth rotation joint
  • Block 119 the surgical instrument 200 is connected to the second slider 119, and the first link 116, the second link 117, and the third link 118 constitute a parallelogram mechanism.
  • the X-axis, Y-axis, and Z-axis form a spatial rectangular coordinate system.
  • the rotation axis of the first link 116, the rotation axis of the second link 117, and the rotation axis of the third link 118 are all along the X axis.
  • the direction of movement of the second slider 119 is along the Z-axis direction
  • the pivot axis of the pivoting member 115 is set along the Y-axis direction. More specifically, the Y-axis is the axis line of the pivoting member 115.
  • the pivoting range of the pivoting member 115 is ⁇ 70 ° along the center line along the Z-axis direction
  • the pivoting range of the first link 116 is from -30 ° to 60 ° along the center line along the Z-axis direction.
  • the moving distance range of the second slider 119 is 250 mm
  • the moving distance range of the first slider 111 is 900 to 1550 mm
  • the rotation range of the first lever 112 is -120 ° to 20 °
  • the rotation of the second lever 113 is The range is ⁇ 120 °
  • the rotation range of the third rod member 114 is ⁇ 100 °
  • the length of the first rod member 112 is 670 ⁇ 20mm
  • the length of the second rod member 113 is 625 ⁇ 20mm.
  • the robot in this embodiment has four robot arms, of which three robot arms are connected with a surgical instrument 200.
  • the fourth robot arm generally does not participate in surgical operations and is reserved for backup.
  • the above-mentioned surgical instrument 200 includes a clamping tool (ie, a clamp for deformation deformation of a surgical object), a surgical rod (for compression deformation of the surgical object), and a scalpel (for cutting of the surgical object).
  • a clamping tool ie, a clamp for deformation deformation of a surgical object
  • a surgical rod for compression deformation of the surgical object
  • a scalpel for cutting of the surgical object
  • the kinematics analysis of the laparoscopic surgical robot is performed to solve the forward and inverse kinematics of the telecentric positioning mechanism, and the operation and control of the virtual robot through force feedback equipment.
  • This embodiment uses Force Dimension's Omega 7.0 force feedback device.
  • Omega 7.0 can realize translational movements in three directions of the x, y, and z axes and rotations about the three axes of x, y, and z.
  • the position and posture of each joint of the telecentric mechanism can be determined by the end position of the surgical instrument.
  • the end position of the surgical instrument can be used to determine the position and posture of each joint through an inverse solution algorithm.
  • the force feedback device Omega7.0 has seven degrees of freedom: three translational degrees of freedom, three rotational degrees of freedom, and one clamping degree of freedom.
  • the translational degrees of freedom, the rotational degrees of freedom, and the clamping degrees of freedom are decoupled. They are not related to each other, so the three translational degrees of freedom of Omega 7.0 are used to control the end position of the surgical instrument.
  • the position and attitude of each component of the telecentric mechanism are reversed to realize the operation control of Omega 7.0 on the virtual surgical robot.
  • a modified physical point spring method is used to establish a physical model of the surgical object, and an axial bounding box (AABB) algorithm is used as a collision detection algorithm between the surgical instrument 200 and the surgical object.
  • the physical model of the surgical object is divided into a free point and a fixed point.
  • the adhesion point free point
  • the specific method is: b1. Assuming that the particles around the adhesion point are fixed, Calculate the resultant force of the adjacent points on the adhesion point, and then find the magnitude of the displacement of the adhesion point under the action of the force. At this time, calculate the resultant force of the adjacent points on the adhesion point again.
  • the point is considered to have reached the force balance state; b2. If it is not within the allowable error range, it is also required to take the displacement of the adhesion point under the combined force, and then move the point along the direction of the combined force Move the corresponding displacement, repeat b1 again, until the magnitude of the resultant force at this point is within the allowable error range, then the point reaches the state of force equilibrium.
  • the single-point force balance calculation method calculate the magnitude and displacement of the resultant force on the particles around the adhesion point, and determine whether the particles around the adhesion point have reached the force equilibrium state; when the surrounding particles are in their respective After the single-point force balance state, calculate the resultant forces of the neighboring points at these points.
  • the system is considered to be in the state of force balance; then Force feedback calculation, collecting the position information of the contact point between the clamping tool vertex and the soft tissue surface of the surgical object and the actual position information of the clamping tool vertex.
  • the clamping tool is controlled by the physical master hand.
  • the simulation model performs the clamping operation.
  • the adhesion point moves with the clamping tool, and the surgical object model deforms.
  • the vector of the position of the particle before deformation and the position of the particle after deformation can obtain the deformation of the spring.
  • the coefficient can calculate the magnitude and direction of the virtual force feedback.
  • a simulation algorithm for clamping deformation of the surgical object is designed to realize the surgery. Like the clamping and deformation of the haptic simulation operation.
  • a mesh model of the surgical object In the process of establishing the geometric model of the surgical object in 3DMAX, the number of vertices and the density of the mesh must be strictly controlled, and then exported and saved as a .3ds data format; the .3ds data model is imported into Deep In Exploration, the model is then subjected to a separate mesh process. Under the premise of ensuring that the model is real, smooth and flat, those unnecessary vertices are deleted and the number of triangular patches is reduced. It also uses the axial bounding box (AABB) algorithm as the collision detection algorithm for surgical instruments and surgical objects.
  • AABB axial bounding box
  • the surgical object mesh model has a large number of triangular patches, if it traverses all the triangular patches during collision detection, Will lead to a large number of calculations, affecting the real-time nature of virtual simulation.
  • an orderly search method of adjacent triangular patches is adopted, and the search speed is increased by establishing a triangular patch cutting search tree, thereby improving the efficiency of collision detection.
  • the cutting point of the surgical knife on the surgical object in order to avoid new small units and affect the simulation effect, set a threshold d on both sides of the cutting line; first determine whether there is a vertex within the threshold, and if so, move the A new vertex is formed from the vertex to the cutting point; if not, a new cutting intersection is generated at the intersection of the cutting line and the edge of the triangular patch; after all the intersections are determined, the old patch is removed to form a new triangular surface Slice; then calculate the normal of the tool plane, copy the cutting intersections, divide all cutting intersections into two groups according to the positive and negative directions of the normal, and then translate the two groups of intersections according to the positive and negative directions of the normal.
  • the translation distance can
  • the spring model is used to establish the suture, and the follower control point (follow the leader (FTL)) method is used to track the trajectory of the line to realize the motion simulation of the line model; because the suture itself is a slender flexible body, it is not too large
  • the traditional method of collision response and methods similar to penetration depth are not suitable for collision detection of line models. Therefore, the present invention adopts a method of simulating the force to achieve the collision response; by simulating the pulling in the knotting process Stretching force, repulsive force and curvature force realize the knotting simulation process of suture.
  • the suture needle penetrates the tissue and organs to create a small hole.
  • the suture thread passes through this small hole. Due to the friction, the suture slides on the one hand and pulls the nearby soft tissue along with it. Move and finally stitch the two separate pieces of soft tissue together by tying a knot.
  • an external force is applied to the soft tissue, which triggers the surface tension of the soft tissue.
  • the surface tension generated by the spring is greater than the maximum surface tension it can withstand, penetration occurs and the spring mass of the soft tissue is pulled by friction.
  • the particles on the soft tissue are also constrained by other particles.
  • this embodiment uses the gallbladder as a surgical object, and provides a specific virtual surgery simulation implementation process, including the following steps:
  • the main window includes two parts: display window and control panel.
  • the window display is mainly used to update and display the image of the virtual surgery environment;
  • the control panel is mainly used for user input to complete the initialization of the system and achieve the positioning of the telecentric point at the incision of the patient's abdominal cavity surface. It also provides controls such as adjusting the position of the viewpoint and restoring the initial position of the robot arm.
  • the program enters the motion simulation thread, first determines the parameters of the drive-free joint control to achieve the positioning of the telecentric positioning mechanism at the incision of the patient's abdominal cavity surface; then initializes the force feedback device to obtain the position information of Omega 7.0 in the virtual coordinate system, Establish the corresponding relationship between the force feedback device Omega 7.0 and the telecentric mechanism of the abdominal surgical robot; finally, use Omega 7.0 control to drive and control the movement of the joints, so that the telecentric positioning mechanism of the robotic arm completes the corresponding position.
  • the virtual slave in the virtual environment has five degrees of freedom, and the micromachine slides and moves around the telecentric point of the parallelogram mechanism to realize the telecentric positioning movement of the robot.
  • the program enters the virtual surgery simulation cycle.
  • the physical master hand must be initialized, obtain the position information of the end of the physical master hand in the fourth joint coordinate system of the virtual surgical robot, establish the correspondence relationship between the physical master hand and the virtual surgical instrument, and realize the force-sense interactive device. Telecentric motion control of surgical instruments. Start the gallbladder compression deformation simulation experiment, set up the bounding box of the gallbladder and its ancillary circuits and micro instruments, and enable collision detection.
  • the virtual surgical instrument does not collide with the gallbladder and continue to control the movement of the main hand; if a collision occurs , The virtual micro-device collides with the gallbladder, and the corresponding mass point on the physical model of the gallbladder moves under the action of external force, which causes the position to change, causing the gallbladder to deform.
  • the program calculates the gallbladder's force feedback to the virtual instrument and outputs it to the Omega 7.0 force sensor device, so that the operator can sense the tactile feedback in the gallbladder compression deformation simulation experiment.
  • the role of the gallbladder in the virtual spring is to restore the original state, and the gallbladder deformation disappears.
  • the program calculates the force feedback of the gallbladder on the virtual instrument and outputs it to the Omega 7.0 force sensor device, so that the operator can sense the tactile feedback in the gallbladder compression and clamping simulation experiment.
  • the clamp of the clamp tool is separated, the clamp tool is separated from the gallbladder, and the role of the gallbladder in the virtual spring is to restore the original state, and the deformation of the gallbladder disappears.
  • the gallbladder cutting simulation experiment was started, and the Omega 7.0 force sensor was operated to control the movement of the virtual surgical instrument.
  • the surgical tool collision model collides with the gallbladder model, obtain the triangular patch that collides with the tool, calculate the projection of the cutting model on the triangular patch, determine whether the cutting line segment intersects the three sides of the triangle, and determine whether the intersection point On the sides of the triangle. If the intersection is on the edge of the triangle, set a threshold to determine whether there are vertices within the threshold range. If there are vertices, move the vertices to the cutting intersection to form a new intersection; if there are no vertices, generate new vertices at the cutting intersection. Then subdivide the triangles. Find the normal direction of the tool plane, copy the cutting vertices, and translate the two sets of intersection points according to the positive and negative directions of the normal. Update the mesh model and geometric model of the surgical object to form an incision.
  • the suture needle When the needle model pierces the soft tissue (the suture needle is not drawn here, but the first node in the suture model can be used as a needle to control the movement of the thread model), check whether the suture has collided with the surface of the soft tissue model . If there is no collision, the suture continues to move under the control of Omega 7.0 without any deformation of the soft tissue; if a collision is detected, various forces begin to be generated, including the static friction between the soft tissue model and the suture. The spring mass in the soft tissue is subjected to force, causing displacement changes and deformation. When this static friction force is greater than the maximum static friction force of the tissue, the tissue will be penetrated.
  • the spring particle in the soft tissue biomechanical model slides to the next node of the current suture node. After multiple penetrations, the spring mass of the soft tissue injury is not much drawn under the action of the line, thereby simulating the effect of the incision being sutured.

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Abstract

一种腹腔微创外科机器人虚拟手术方法，包括以下步骤：a.搭建虚拟手术仿真平台，包括设计具有平行四边形远心定位机构的机器人模型，通过力反馈设备对虚拟机器人的操作进行控制；b.建立手术对象的物理模型，进行力平衡计算，实现手术对象按压变形和夹持变形的仿真操作和力觉交互；c.建立手术对象的网格模型，手术对象切割仿真；d.利用弹簧模型建立缝合线，实现缝合线打结模拟；e.通过分析缝合线在与软组织交互过程中所涉及到的摩擦力和张力，实现了手术对象的缝合模拟过程。该腹腔微创外科机器人虚拟手术方法，能够对手术进行全程模拟仿真，精确度高，实时性强。

Description

腹腔微创外科机器人虚拟手术方法 技术领域
本发明涉及一种腹腔微创外科机器人虚拟手术方法。
背景技术
虚拟现实技术是一种可以创建和体验虚拟世界的计算机仿真系统。它以计算机技术为核心，结合多种相关技术，生成一个在视觉、听觉以及触觉等高度近视的交互式环境，给使用者提供一种身临其境的感觉，可以没有限制的观察三维空间内的事物。
虚拟手术是虚拟现实技术在医学领域的一个典型应用。它作为一种新的研究方向，是一种集生物力学、机械学、医学、机器人等诸多学科为一体的新型研究领域。虚拟手术是从医学影像数据出发，在计算机中建立一个虚拟手术环境，然后构建人体组织模型，并利用力触觉交互设备与之进行交互操作的一种手术系统。医生可以利用虚拟手术环境中的信息进行手术规划、手术培训，手术预演以及在实际手术过程中引导手术等。
微创外科手术机器人已经成为医疗机器人领域的研究热点，它把传统医疗器械与信息技术、机器人技术结合在一起，使外科诊断与治疗达到了微创化、微型化、智能化和数字化。与传统手术相比，微创手术机器人具有显著的优势：微创机器人手术能够改善医生的工作模式，让医生在进行手术时更灵巧、更方便、更精准，甚至能让两个不同领域的外科医生同时进行两个相关的手术；另外，即使长时间的手术操作，微创手术机器人也不会像人手那样因为疲惫而颤抖，大大提高了手术质量，延长了外科医生的职业寿命；微创外科机器人手术 创口仅在1厘米左右，大大减少了患者的失血量及术后疼痛，且病人复原快，大肠和胃脏的伤口愈合只需五至七天，皮肤的伤口则一两天就好，胆囊在手术后的愈合速度更快。以上优点使得机器人成为医生最好的助手。
尽管如此，当前的外科机器人手术与传统的微创手术相比还是存在一些明显的缺陷。医生不能直接观察手术区域的环境，只能通过内孔镜获取病灶信息，并根据内窥镜反馈的信息，控制手术器械对病灶进行手术操作。与传统微创手术相比，手术器械的活动区域有限，医生只能控制外科手术机器人在很小的区域内进行手术操作，这些都对外科医生提出了更高的要求。因此外科医生若想熟练掌握这种新型的手术方式，必须经过长期的培训，目前除了动物和尸体外，没有更好的训练对象。但是运用动物作为手术训练对象，一方面，动物和人体的解剖结构不同，另一方面也会受到动物保护协会的谴责；而人的尸体又不能重复使用。
虚拟手术系统的研究正是致力于解决这些问题，为特殊的手术操作提供一个理想的训练工具。因此虚拟手术仿真的研究具有十分重要的意义。
发明内容
为了解决以上技术问题，本发明的目的在于提出一种腹腔微创外科机器人虚拟手术方法。
为了达到上述目的，本发明提供了一种技术方案：腹腔微创外科机器人虚拟手术方法，它包括以下步骤：
a.搭建虚拟手术仿真平台，包括设计具有平行四边形远心定位机构的机器人模型，对机器人模型进行运动学分析，求解远心定位机构正运动学和逆运动学，通过力反馈设备对虚拟机器人的操作控制；
b.建立手术对象的物理模型，利用轴向包围盒算法作为手术器械与手术对象之间的碰撞检测算法，进行力平衡计算，实现手术对象按压变形和夹持变形的仿真操作和力觉交互；
c.建立手术对象的网格模型，利用轴向包围盒算法作为手术刀具与手术对象的碰撞检测算法，并在进行碰撞检测时采用临近三角面片有序搜索方法，通过建立三角面片切割搜索树进行搜索，实现手术对象的切割仿真；
d.利用弹簧模型建立缝合线，进行线模型的运动仿真，采用模拟受力的方法实现碰撞响应，通过模拟打结过程中的拉伸力、排斥力和曲度力，实现了缝合线的打结模拟过程；
e.通过分析缝合线在与手术对象软组织交互过程中所涉及到的摩擦力和张力，实现了手术对象的缝合模拟过程。
进一步地，机器人模型包括机架和至少一条机械臂，每条机械臂包括通过第一滑动关节上下移动地连接在机架上的第一滑块、通过第一旋转关节与第一滑块相转动连接的第一杆件、通过第二旋转关节与第一杆件相转动连接的第二杆件、通过第三旋转关节与第二杆件相转动连接的第三杆件、通过第四旋转关节与第三杆件相枢转连接的枢转件、通过第五旋转关节与枢转件相转动连接的第一连杆、通过第六旋转关节与第一连杆相转动连接的第二连杆、通过第七旋转关节与第二连杆相转动连接的第三连杆、通过第二滑动关节与第三连杆相移动连接的第二滑块，第二滑块连接手术器械，第一连杆、第二连杆、第三连杆构成平行四边形机构。
进一步地，步骤a中搭建虚拟手术仿真平台，还包括在虚拟手术环境中添加至少一个摄像机，通过鼠标操作控制摄像机的位置和方向，实现了虚拟手术环境的移动旋转；在控制面板上添加控制按钮实现了视角的切换以及重置视觉 点的位置。
进一步地，步骤b中，根据质点分布规律，确定力平衡计算方法，首先判断质点是否满足受力条件，进而计算手术器械末端到该区域内各质点的距离，然后计算各个质点的力，再计算出手术对象按压变形过程中的力反馈，实现手术对象按压变形的仿真操作和力觉交互。
进一步地，步骤b中，采用质点弹簧法建立手术对象的物理模型，当夹持工具与手术对象接触并处于夹持状态时，判断粘附点是否与夹持工具一起运动，如果运动，则通过单点力平衡计算方法进行计算判断该粘附点是否达到力平衡状态；当该粘附点达到力平衡状态后，再通过单点力平衡计算方法进行计算判断该粘附点周围的质点是否达到力平衡状态；当周围的质点都处于各自的单点力平衡状态后，再求取这几个点此时所受的邻点合力，如果这几个点都在整体力平衡允许误差范围内，则认为该系统处于力平衡状态；然后进行力反馈计算，采集夹持工具顶点与手术对象软组织表面接触点的位置信息和夹持工具顶点的实际位置信息，在手术对象夹持变形操作仿真时，夹持工具在对仿真模型进行夹持操作，粘附点随夹持工具运动，手术对象模型发生变形，通过变形前质点的位置与变形后质点的位置构成的矢量，得到弹簧的形变量，根据设置的弹簧系数计算出虚拟力反馈的大小和方向，实现手术对象夹持变形的仿真操作和力觉交互。
更进一步地，单点力平衡计算方法包括：b1.假设该点周围的质点固定不动，计算该点受到的邻点合力，然后求取在该力的作用下，该点移动位移的大小，此时再次计算该粘附点受到的邻点合力，如果该力的大小在单点力平衡允许的误差范围内，则认为该点达到了力平衡状态；b2.如果不在允许误差范围内，则还要求取该合力下该点的位移，再将该点沿合力方向移动相应位移，并重复步 骤b1，直到该点在某处受到合力的大小在允许误差范围内，则该点达到力平衡状态。
进一步地，步骤c中，将手术刀具上两条刀刃所在的直线投影到网格模型中三角面片所在的平面上，得到当前时刻的切割线段，通过联立空间直线方程和三角面片每条边所在直线的方程，得到手术刀具在手术对象上的切割点；在切割线的两侧设定一个阈值d；首先判断在该阈值内是否存在顶点，如果有，则移动该顶点到切割点的位置，形成新的顶点；如果没有，则在切割线和三角面片的边线交点处产生新的切割交点；确定所有交点后，移除旧的面片，形成新的三角面片；然后计算刀具平面的法线，复制切割交点，将所有的切割交点按照该法线的正负方向分为两组，然后按照法线的正负方向将这两组交点平移一定距离，交点与同法线方向的顶点形成一新的三角面片；最后更新网格模型和手术对象的几何模型，形成切口。
进一步地，步骤d中，采用跟踪控制点的方法追踪线的轨迹，实现线模型的运动仿真。
进一步地，虚拟缝合操作中，针头穿刺手术对象软组织时，对软组织施加了一个外力，引发了软组织的表面张力，当弹簧产生的表面张力大于所能承受的最大表面张力时，穿透发生，并且通过摩擦力拉动软组织的弹簧质点，由于该质点本身受到其它质点的约束，当该质点偏离原来的位置太远时，该质点受到其它质点的作用力将大于摩擦力，则滑动发生。
由于采用上述技术方案，本发明腹腔微创外科机器人虚拟手术方法，建立了腹腔主要器脏组织的三维模型，构建了虚拟手术环境，搭建了虚拟手术仿真平台，设计了腹腔外科手术机器人，并对其进行了运动学分析，建立了面向腹腔微创手术的腹腔内部组织的生物力学模型，进行了按压、夹持、切割、缝合 等虚拟手术仿真研究，能够对手术进行全程模拟仿真，精确度高，实时性强，医生可以对虚拟手术环境中的手术病患重复进行手术训练，节约了医生培训的成本，缩短了手术训练时间，提高了外科医生手术的熟练程度。建立虚拟手术仿真系统，可以为医生提供手术预演，延长医生的职业寿命，也可以实现远程协助和模拟，确定手术方案。本腹腔微创外科机器人虚拟手术方法对腹腔外科机器人手术具有重大的理论和实际意义。
上述说明仅是本发明技术方案的概述，为了能够更清楚了解本发明的技术手段，并可依照说明书的内容予以实施，以下以本发明的较佳实施例并配合附图详细说明如后。
附图说明
附图1为本发明腹腔微创外科机器人虚拟手术方法中虚拟环境的部分示意图；
附图2为本发明腹腔微创外科机器人虚拟手术方法中机器人模型的第一结构示意图，其中，只画出一条机械臂以进行说明；
附图3为本发明腹腔微创外科机器人虚拟手术方法中机器人模型的第二结构示意图，其中，只画出一条机械臂以进行说明。
图中标号为：
100、机械臂；
111、第一滑块；112、第一杆件；113、第二杆件；114、第三杆件；115、枢转件、116、第一连杆；117、第二连杆；118、第三连杆；119、第二滑块；
121、第一滑动关节；122、第一旋转关节；123、第二旋转关节；124、第三旋转关节；125、第四旋转关节；126、第五旋转关节；127、第六旋转关节； 128、第七旋转关节；129、第二滑动关节；
200、手术器械；
300、机架；
400、手推车；500、显示器。
具体实施方式
下面结合附图和实施例，对本发明的具体实施方式作进一步详细描述。以下实施例用于说明本发明，但不用来限制本发明的范围。
参照附图1至附图3，本实施例中的腹腔微创外科机器人虚拟手术方法，利用3DMAX对涉及到的人体腹腔组织模型、虚拟手术机器人、手术器械等进行几何建模，并设置相关模型的局部坐标等相关参数；利用Deep Exploration对这些模型添加材质、纹理等相关信息，增加其真实性，最后导出保存为.3ds数据格式。结合腹腔外科虚拟手术所涉及到的软、硬件设备搭建虚拟手术仿真平台。在虚拟手术环境中添加一个摄像机，通过鼠标操作控制摄像机的位置和方向，实现了虚拟手术环境的前移、后退、上升、下降、旋转；在控制面板上添加控制按钮实现了视角在前后左右方向的切换以及重置视觉点的位置，达到了虚拟手术场景漫游的效果。
设计具有平行四边形远心定位机构的机器人模型，它包括机架和连接在机架上的至少一条机械臂100，每条机械臂100均包括位置调整机构和能够通过控制装置进行控制的远心机构。每条机械臂100一共有九个关节，九个自由度。如附图2和附图3所示，机械臂100包括通过第一滑动关节上下移动地连接在机架300上的第一滑块111、通过第一旋转关节与第一滑块111相转动连接的第一杆件112、通过第二旋转关节与第一杆件112相转动连接的第二杆件113、通 过第三旋转关节与第二杆件113相转动连接的第三杆件114、通过第四旋转关节与第三杆件114相枢转连接的枢转件115、通过第五旋转关节与枢转件115相转动连接的第一连杆116、通过第六旋转关节与第一连杆116相转动连接的第二连杆117、通过第七旋转关节与第二连杆117相转动连接的第三连杆118、通过第二滑动关节与第三连杆118相移动连接的第二滑块119，手术器械200与第二滑块119相连接，第一连杆116、第二连杆117、第三连杆118构成平行四边形机构。具体地，设X轴、Y轴、Z轴构成空间直角坐标系，则第一连杆116的转动轴线、第二连杆117的转动轴线、第三连杆118的转动轴线均沿着X轴方向设置，第二滑块119的移动方向为沿着Z轴方向，枢转件115的枢转轴线沿着Y轴方向设置，更为具体地，Y轴为枢转件115的轴心线。本实施例中，枢转件115的转动范围为以沿着Z轴方向的中心线±70°，第一连杆116的转动范围为以沿着Z轴方向的中心线-30°～60°，第二滑块119的移动距离范围为250mm，第一滑块111的移动距离范围为900～1550mm，第一杆件112的转动范围是-120°～20°，第二杆件113的转动范围为±120°，第三杆件114的转动范围为±100°，第一杆件112的长度为670±20mm，第二杆件113的长度为625±20mm。
本实施例中的机器人有四条机械臂，其中三条机械臂连接有手术器械200，第四条机械臂一般不参与手术操作，留作备用。
上述的手术器械200包括夹持工具(即夹钳，用于手术对象的夹持变形)、手术棒(用于手术对象的按压变形)、手术刀(用于手术对象的切割)。
对腹腔外科机器人进行运动学分析，求解远心定位机构正运动学和逆运动学，通过力反馈设备对虚拟机器人的操作控制。本实施例中采用的是Force Dimension公司的Omega 7.0力反馈设备，Omega 7.0可实现沿x、y、z轴3个 方向的平移运动和绕x、y、z 3个轴的转动，并有一个持自由度。可以提供x、y、z轴3个方向的反馈力和一个夹持力。由于设计的腹腔外科手术机器人的末端手术器械实现的是远心运动，远心点位于腹腔体表切口处，远心机构各个关节的位置和姿态可以通过手术器械的末端位置确定，所以只需得到手术器械的末端位置，就可以通过逆解算法确定各个关节的位置和姿态。力反馈设备Omega7.0拥有七个自由度：三个平移自由度、三个旋转的自由度以及一个夹持的自由度，其中平移自由度和旋转自由度以及夹持自由度是解耦的，它们之间互不相关，所以利用Omega 7.0的三个平移自由度去控制手术器械末端位置，最后反解远心机构各个部件的位置和姿态，实现Omega 7.0对虚拟手术机器人的操作控制。
采用改进的质点弹簧法建立手术对象的物理模型，利用轴向包围盒(AABB)算法作为手术器械200与手术对象之间的碰撞检测算法。根据质点分布规律，确定力平衡计算方法，首先判断质点是否满足受力条件，进而计算手术器械球到该区域内各质点的距离，然后计算各个质点的力，这种方法避免了影响力较小的自由点以及非自由点的计算，降低了计算量，提高了仿真速度。在此基础上计算出手术对象按压变形过程中的力反馈，实现手术对象按压变形的仿真操作和力觉交互。
结合手术对象的物理模型，进行力平衡计算，手术对象的物理模型中分为自由点和固定点，当夹持工具与手术对象模型接触并处于夹持状态时，判断粘附点(自由点)是否与夹持工具一起运动，如果运动，则通过单点力平衡计算方法进行计算判断该粘附点是否达到力平衡状态，具体方法为：b1.假设该粘附点周围的质点固定不动，计算该粘附点受到的邻点合力，然后求取在该力的作用下，该粘附点移动位移的大小，此时再次计算该粘附点受到的邻点合力，如 果该力的大小在单点力平衡允许的误差范围内，则认为该点达到了力平衡状态；b2.如果不在允许误差范围内，则还要求取该合力下该粘附点的位移，再将该点沿合力方向移动相应位移，再次重复b1，直到该点在某处受到合力的大小在允许误差范围内，则该点达到力平衡状态。按照该单点力平衡计算方法，分别计算该粘附点周围的质点所受合力的大小和发生的位移，判断该粘附点周围的质点是否达到力平衡状态；当周围的质点都处于各自的单点力平衡状态后，再求取这几个点此时所受的邻点合力，如果这几个点都在整体力平衡允许误差范围内，则认为，该系统处于力平衡状态；然后进行力反馈计算，采集夹持工具顶点与手术对象软组织表面接触点的位置信息和夹持工具顶点的实际位置信息，在手术对象夹持变形操作仿真时，夹持工具在物理主手的控制下对仿真模型进行夹持操作，粘附点随夹持工具运动，手术对象模型发生变形，通过变形前质点的位置与变形后质点的位置构成的矢量，就可以得到弹簧的形变量，根据设置的弹簧系数就可以计算出虚拟力反馈的大小和方向；最后设计手术对象夹持变形仿真算法，实现手术对象夹持变形的仿真操作和力觉交互。
建立手术对象的网格模型，在3DMAX中建立手术对象几何模型的过程中，要严格控制顶点的数量和网格的密度，然后导出保存为.3ds数据格式；将该.3ds数据模型导入到Deep Exploration中，然后对该模型进行分离网格处理，在保证模型真实、光滑、平整的前提下，删除那些不必要的顶点，减少三角面片的数量。同样利用轴向包围盒(AABB)算法作为手术器械与手术对象的碰撞检测算法，由于手术对象网格模型中拥有大量的三角面片，在进行碰撞检测时，如果遍历所有的三角面片，就会导致大量的计算，影响虚拟仿真的实时性。为了满足仿真的实时性要求，采用邻近三角面片有序搜索方法，通过建立三角面片切割搜索树来提高搜索速度，进而提高碰撞检测的效率。将手术刀具上两条刀刃 所在的直线投影到网格模型中三角面片所在的平面上，得到当前时刻的切割线段，通过联立空间直线方程和三角面片每条边所在直线的方程，得到手术刀具在手术对象上的切割点；为了避免产生新的小单元，影响仿真效果，在切割线的两侧设定一个阈值d；首先判断在该阈值内是否存在顶点，如果有，则移动该顶点到切割点的位置，形成新的顶点；如果没有，则在切割线和三角面片的边线交点处产生新的切割交点；确定所有交点后，移除旧的面片，形成新的三角面片；然后计算刀具平面的法线，复制切割交点，将所有的切割交点按照该法线的正负方向分为两组，然后按照法线的正负方向平移这两组交点，平移的距离可以根据效果自行定义，交点与同法线方向的顶点形成一新的三角面片；最后更新网格模型和手术对象的几何模型，形成切口。
利用弹簧模型建立缝合线，采用跟踪控制点(follow the leader，简称FTL)的方法来追踪线的轨迹，实现了线模型的运动仿真；因为缝合线本身是一个细长的柔体，没有太大的深度，所以传统的碰撞响应的方法以及类似与穿透深度等方法并不适合于线模型的碰撞检测，于是本发明采用模拟受力的方法来实现碰撞响应；通过模拟打结过程中的拉伸力、排斥力和曲度力，实现了缝合线的打结模拟过程。
手术缝合过程中，缝合针刺穿组织器官产生一个小洞，同时缝合线穿过这个小洞由于摩擦力的作用，缝合线一方面在这个小洞中滑动，一方面拉动附近的软组织随它一起移动，最后通过打结将分开的两片软组织缝合在一起。虚拟缝合操作中，针头穿刺软组织时，对软组织施加了一个外力，引发了软组织的表面张力。当弹簧产生的表面张力大于所能承受的最大表面张力时，穿透发生，并且通过摩擦力拉动软组织的弹簧质点。但是软组织上的质点本身也受到其它质点的约束，当质点偏离原来的位置太远时，质点受到其它质点给它的作用力 将大于摩擦力，滑动发生。通过分析缝合线在与软组织交互过程中所涉及到的摩擦力和张力，实现了手术对象的缝合模拟过程。
根据上述的腹腔微创外科机器人虚拟手术方法，本实施例以胆囊作为手术对象，给出一种具体地虚拟手术仿真实施过程，包括以下步骤：
1、腹腔外科手术机器人的运动仿真
进入仿真程序，主窗口包括显示窗口和控制面板两个部分。窗口显示主要用来更新显示虚拟手术环境的图像；控制面板主要用于用户输入，完成系统的初始化工作，实现远心点在患者腹腔体表切口处的定位。并提供调整视点位置、恢复机械臂初始位置等控件。程序进入运动仿真线程，首先确定无驱动控制关节的参数，实现远心定位机构在患者腹腔体表切口处的定位；然后对力反馈设备进行初始化，获取Omega 7.0在虚拟坐标系下的位置信息，建立力反馈设备Omega 7.0和腹腔外科手术机器人远心机构的对应关系；最后利用Omega 7.0控制可驱动控制关节的运动，使机械臂远心定位机构完成相应的摆位。此时，虚拟环境中的虚拟从手具有五个自由度，微机械沿平行四边形机构的远心点滑动和绕其运动，实现机器人的远心定位运动。
2、按压胆囊变形仿真
程序进入虚拟手术仿真循环，首先要初始化物理主手，获取物理主手末端在虚拟手术机器人第四关节坐标系下的位置信息，建立物理主手与虚拟手术器械的对应关系，实现力觉交互设备对手术器械的远心运动控制。启动胆囊按压变形仿真实验，建立胆囊及其附属管路和微器械的包围盒，启用碰撞检测，若包围盒不相交，则虚拟手术器械未与胆囊发生碰撞，继续控制主手运动；若发生碰撞，则虚拟微器械与胆囊发生碰撞，胆囊物理模型上的相应质点在外力的作用下运动，进而引起位置的改变，致使胆囊发生形变。与此同时，程序计算 胆囊对虚拟器械的力反馈，输出到Omega 7.0力觉装置，使操作者感知胆囊按压变形仿真实验中的触觉反馈。当虚拟器械与胆囊分离时，胆囊在虚拟弹簧的作用在恢复原状，胆囊变形消失。
3、夹持胆囊变形仿真
启动胆囊夹持变形仿真实验，建立胆囊及其附属管路和微器械的包围盒，启用碰撞检测，若包围盒不相交，则夹持工具未与胆囊发生碰撞，继续控制主手运动；若发生碰撞，则夹持工具顶端两个夹子与胆囊发生碰撞，判断粘附点是否随手术器械运动，若粘附点未随夹钳工具运动，则胆囊未发生变形，若发生了运动，则与之相连的虚拟弹簧在外力的作用下，伸长或者缩短，带动周围的自由点发生运动，胆囊发生变形。与此同时，程序计算胆囊对虚拟器械的力反馈，输出到Omega 7.0力觉装置，使操作者感知胆囊按压夹持仿真实验中的触觉反馈。当夹钳工具的夹子分离时，则夹钳工具与胆囊分离，胆囊在虚拟弹簧的作用在恢复原状，胆囊的变形消失。
4、切割仿真实验
首先启用胆囊切割仿真实验，操作Omega 7.0力觉装置，控制虚拟手术器械移动。当手术刀具碰撞模型与胆囊模型发生碰撞时，获取与刀具发生碰撞的三角面片，并计算切割模型在该三角面片上的投影，判断切割线段是否与三角形的三个边相交，并判断交点是否在三角形的边上。如果交点在三角形的边上，设置阈值，判断阈值范围内是否拥有顶点，如果有顶点，则移动顶点到切割交点处，形成新的交点；如果没有顶点，则在切割交点处产生新的顶点，然后进行三角面片细分。求取刀具平面的法线方向，复制切割顶点，按照法线的正负方向平移两组交点。更新手术对象的网格模型和几何模型，形成切口。
5、缝合线打结仿真实验
初始化Omega 7.0设备，获取它在虚拟坐标系的位置信息，转化为线模型的运动控制信息，控制线模型的第一个结点运动，此时自碰撞检测算法将不断地对线模型进行自碰撞检测。若检测到两段线段发生碰撞且碰撞线段之间的距离超过了安全距离，则在相关线段的结点处强加排斥控制条件，从而产生一种排斥力，对线段间的运动产生“阻挠”，阻止缝合线穿透现象的发生，最终实现打结效果。
6、缝合仿真模拟
当针模型刺向软组织时(这里没有绘制出缝合针，但是可以将缝合线模型中的第一个结点当作针头，进而控制线模型运动)，检测缝合线是否与软组织模型表面是否发生碰撞。如果没有碰撞，则缝合线在Omega 7.0的操控下继续运动，软组织没有发生任何变形；如果检测到碰撞，则开始产生各种作用力，包括软组织模型与缝合线的静摩擦力等。软组织中的弹簧质点受力，发生位移变化，产生变形。当这个静摩擦力大于组织的最大静摩擦力时，组织将会被穿透，如图所示，软组织生物力学模型中的弹簧质点滑向当前缝合线结点的下一个结点。经过多次穿透后，软组织伤的弹簧质点在线的作用下不多被拉近，进而模拟出切口被缝合的效果。
以上所述仅是本发明的优选实施方式，并不用于限制本发明，应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明技术原理的前提下，还可以做出若干改进和变型，这些改进和变型也应视为本发明的保护范围。

Claims (9)

  1. 一种腹腔微创外科机器人虚拟手术方法，它包括以下步骤：
    a.搭建虚拟手术仿真平台，包括设计具有平行四边形远心定位机构的机器人模型，对机器人模型进行运动学分析，求解远心定位机构正运动学和逆运动学，通过力反馈设备对虚拟机器人的操作控制；
    b.建立手术对象的物理模型，利用轴向包围盒算法作为手术器械与手术对象之间的碰撞检测算法，进行力平衡计算，实现手术对象按压变形和夹持变形的仿真操作和力觉交互；
    c.建立手术对象的网格模型，利用轴向包围盒算法作为手术刀具与手术对象的碰撞检测算法，并在进行碰撞检测时采用临近三角面片有序搜索方法，通过建立三角面片切割搜索树进行搜索，实现手术对象的切割仿真；
    d.利用弹簧模型建立缝合线，进行线模型的运动仿真，采用模拟受力的方法实现碰撞响应，通过模拟打结过程中的拉伸力、排斥力和曲度力，实现了缝合线的打结模拟过程；
    e.通过分析缝合线在与手术对象软组织交互过程中所涉及到的摩擦力和张力，实现了手术对象的缝合模拟过程。
  2. 根据权利要求1所述的腹腔微创外科机器人虚拟手术方法，其特征在于：所述的机器人模型包括机架和至少一条机械臂，每条所述机械臂包括通过第一滑动关节上下移动地连接在所述机架上的第一滑块、通过第一旋转关节与所述第一滑块相转动连接的第一杆件、通过第二旋转关节与所述第一杆件相转动连接的第二杆件、通过第三旋转关节与所述第二杆件相转动连接的第三杆件、通过第四旋转关节与所述第三杆件相枢转连接的枢转件、通过第五旋转关节与所述枢转件相转动连接的第一连杆、通过第六旋转关节与所述第一连杆相转动连接的第二连杆、通过第七旋转关节与所述第二连杆相转动连接的第三连杆、通过 第二滑动关节与所述第三连杆相移动连接的第二滑块，所述第二滑块连接手术器械，所述的第一连杆、第二连杆、第三连杆构成平行四边形机构。
  3. 根据权利要求1所述的腹腔微创外科机器人虚拟手术方法，其特征在于：所述步骤a中搭建虚拟手术仿真平台，还包括在虚拟手术环境中添加至少一个摄像机，通过鼠标操作控制摄像机的位置和方向，实现了虚拟手术环境的移动旋转；在控制面板上添加控制按钮实现了视角的切换以及重置视觉点的位置。
  4. 根据权利要求1所述的腹腔微创外科机器人虚拟手术方法，其特征在于：所述步骤b中，根据质点分布规律，确定力平衡计算方法，首先判断质点是否满足受力条件，进而计算手术器械末端到该区域内各质点的距离，然后计算各个质点的力，再计算出手术对象按压变形过程中的力反馈，实现手术对象按压变形的仿真操作和力觉交互。
  5. 根据权利要求1所述的腹腔微创外科机器人虚拟手术方法，其特征在于：所述步骤b中，采用质点弹簧法建立手术对象的物理模型，当夹持工具与手术对象接触并处于夹持状态时，判断粘附点是否与夹持工具一起运动，如果运动，则通过单点力平衡计算方法进行计算判断该粘附点是否达到力平衡状态；当该粘附点达到力平衡状态后，再通过单点力平衡计算方法进行计算判断该粘附点周围的质点是否达到力平衡状态；当周围的质点都处于各自的单点力平衡状态后，再求取这几个点此时所受的邻点合力，如果这几个点都在整体力平衡允许误差范围内，则认为该系统处于力平衡状态；然后进行力反馈计算，采集夹持工具顶点与手术对象软组织表面接触点的位置信息和夹持工具顶点的实际位置信息，在手术对象夹持变形操作仿真时，夹持工具在对仿真模型进行夹持操作，粘附点随夹持工具运动，手术对象模型发生变形，通过变形前质点的位置与变形后质点的位置构成的矢量，得到弹簧的形变量，根据设置的弹簧系数计算出 虚拟力反馈的大小和方向，实现手术对象夹持变形的仿真操作和力觉交互。
  6. 根据权利要求5所述的腹腔微创外科机器人虚拟手术方法，其特征在于：所述的单点力平衡计算方法包括：b1.假设该点周围的质点固定不动，计算该点受到的邻点合力，然后求取在该力的作用下，该点移动位移的大小，此时再次计算该粘附点受到的邻点合力，如果该力的大小在单点力平衡允许的误差范围内，则认为该点达到了力平衡状态；b2.如果不在允许误差范围内，则还要求取该合力下该点的位移，再将该点沿合力方向移动相应位移，并重复步骤b1，直到该点在某处受到合力的大小在允许误差范围内，则该点达到力平衡状态。
  7. 根据权利要求1所述的腹腔微创外科机器人虚拟手术方法，其特征在于：所述步骤c中，将手术刀具上两条刀刃所在的直线投影到网格模型中三角面片所在的平面上，得到当前时刻的切割线段，通过联立空间直线方程和三角面片每条边所在直线的方程，得到手术刀具在手术对象上的切割点；在切割线的两侧设定一个阈值d；首先判断在该阈值内是否存在顶点，如果有，则移动该顶点到切割点的位置，形成新的顶点；如果没有，则在切割线和三角面片的边线交点处产生新的切割交点；确定所有交点后，移除旧的面片，形成新的三角面片；然后计算刀具平面的法线，复制切割交点，将所有的切割交点按照该法线的正负方向分为两组，然后按照法线的正负方向将这两组交点平移一定距离，交点与同法线方向的顶点形成一新的三角面片；最后更新网格模型和手术对象的几何模型，形成切口。
  8. 根据权利要求1所述的腹腔微创外科机器人虚拟手术方法，其特征在于：所述步骤d中，采用跟踪控制点的方法追踪线的轨迹，实现线模型的运动仿真。
  9. 根据权利要求1所述的腹腔微创外科机器人虚拟手术方法，其特征在于：虚拟缝合操作中，针头穿刺手术对象软组织时，对软组织施加了一个外力，引发 了软组织的表面张力，当弹簧产生的表面张力大于所能承受的最大表面张力时，穿透发生，并且通过摩擦力拉动软组织的弹簧质点，由于该质点本身受到其它质点的约束，当该质点偏离原来的位置太远时，该质点受到其它质点的作用力将大于摩擦力，则滑动发生。
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