Medical robot is one of the most active and invested directions in the field of robot research abroad at present, and its development prospect is very promising. In recent years, medical robot technology has attracted great attention from academic circles in the United States, France, Germany, Italy, Japan and other countries, and the research work has been vigorously carried out. Since 1990s, the International Advanced Robotics Program (IARP) has held many seminars on medical surgical robots, and DARPA has been approved to carry out surgical research based on remote operation for simulation surgery, surgical training and anatomy teaching. The European Union and French National Research Center also take robot-assisted surgery and virtual surgery simulation system as one of the key research and development projects. In developed countries, medical surgical robots have appeared in the market, and a large number of clinical case studies have been carried out. With the development of science and technology, especially computer technology, people pay more and more attention to the role of medical robots in clinic. As the third eye of the surgeon, the surgical assistant navigation system can let the surgeon see the internal structure of the surgical site, avoid the surgical mistakes caused by the doctor's inexperience, make the operation safer, more reliable, more accurate and more scientific, and has a very broad application prospect. It has been successfully used in neurosurgery, plastic surgery, urology, spine, otolaryngology, ophthalmology, knee replacement, laparoscopy and other fields. Therefore, with the assistance of medical images, micro-devices, sensors, computers and robots, it has changed from an open and complete manual operation to assisting doctors in minimally invasive surgery. In addition, doctors have also benefited a lot in choosing the best surgical path, performing complex surgery and improving the success rate of surgery. Minimally invasive surgery technology rose in the 1980s, which is commonly referred to as interventional surgery. With the help of various visual imaging equipment and advanced and dexterous surgical instruments and equipment, surgical instruments enter the human body through small incision for treatment or diagnosis. Compared with traditional open surgery, minimally invasive surgery has many advantages, such as less trauma, relieving patients' pain, rapid postoperative recovery, improving the quality of surgery and reducing medical and social costs. Therefore, it is an inevitable trend of surgical development to be widely welcomed by doctors and patients. As a representative of minimally invasive surgery, laparoscopic minimally invasive surgery is a major change to traditional open surgery. However, laparoscopic surgery also has some problems. For example, when a doctor operates an instrument before the operating table, the distance between the doctor's hand and the end of the operated instrument is generally 400~500mm. Grasping surgical instruments accurately for a long time will make doctors feel very tired. In addition, the error transmitted to the end of the instrument due to the trembling of the doctor's hand will also increase. Using robot technology can solve the above problems well. Because of the accurate positioning of the robot, the work intensity is greatly reduced, and the fibrillation can be eliminated by software programming, thus improving the surgical accuracy. Compared with traditional industrial robots, the system of minimally invasive surgical robots is more targeted, and usually one structure is only suitable for one operation. For the master-slave robot, the surgeon's decision is transmitted to the slave hand through the master hand during the operation. By monitoring the movement of the slave hand, adjusting or correcting the control, the expected effect can be achieved and minimally invasive surgery can be realized. Because the hand system directly affects the patient, its performance directly affects the performance of the whole system, the quality of surgery, the safety of the system and so on. With the continuous development of computer technology, microcomputer can meet the requirements of surgical navigation system in terms of calculation speed and storage capacity. In China, it will be a development trend to develop a miniaturized, low-cost and high-precision surgical navigation system based on microcomputer. 1, literature review 3. 1 Compared with other robots, medical robots have the following characteristics: ① their working environment is generally in hospitals, streets, families and non-specific occasions, with the ability of moving, navigating, recognizing and avoiding, and with intelligent human-computer interaction interface. In the case of manual control, you also need to have remote control ability. ② The working objects of medical robots are people, human body information and related medical devices, which need comprehensive knowledge of engineering, medicine, biology, medicine and sociology to carry out research projects. ③ The material selection and structural design of medical robot must be based on the premise of easy disinfection and sterilization, safe and reliable, and free from radiation. (4) The performance of the medical robot with human as the working object must meet the requirements of adaptability to changing conditions, flexibility in work, safety against danger and adaptability to human body and spirit. ⑤ There are or reserved universal docking interfaces between medical robots and between medical robots and medical instruments, including information communication interface, human-computer interaction interface, clinical auxiliary equipment interface and patient transport interface. Technically, the development of medical robots is based on the following basic technologies: mechanical design and manufacturing technology, sensor application technology, automatic control technology, driving technology and human-computer interaction technology. Medical robots can be roughly divided into rescue robots, surgical robots, transport robots and rehabilitation robots according to their uses. Surgical robot not only has the basic characteristics of robot, but also has its own characteristics, such as accurate position selection, fine movement, and avoiding infection of patients. In vascular suture surgery, it is difficult to suture blood vessels thinner than 1 mm by hand. If surgical robots are used, the accuracy of vascular suture surgery can be less than 0.1mm; Using surgical robots to perform surgery avoids direct contact between doctors and patients' blood and greatly reduces the risk of infection of patients. Commercial surgical robots first appeared in 1994, which was developed by American Computer Sports Company. In essence, it is an automatic "hand-holding mirror" of voice-controlled laparoscopy, named Aesop. 1in March, 997, the surgical robot completed the first laparoscopic operation-cholecystectomy in St. Pierre Hospital in Brussels, Belgium. From 65438 to 0998, Zeus system developed by ComputerMotion Company, Da Vinci system developed by Intuitive Surgical Company and Laprotek system developed by endoVia Company were successful respectively. These three systems are composed of doctor's console, manipulator and endoscope device. Zeus system uses pure signal to control the manipulator from the doctor's console, and the transmission distance is not affected by video delay. In September 2006, Zeus system successfully realized the trans-Atlantic (new york, USA-Strasbourg, France) robotic laparoscopic cholecystectomy for the first time. At present, the surgical robot has not only completed general surgery, but also performed neurosurgery, heart repair, cholecystectomy, artificial joint replacement, urology and plastic surgery. Nevertheless, there are still many aspects of the surgical robot that need to be perfected and improved. By adding "artificial vision" system, the operating field can be monitored during the operation, which can assist the operator to make judgments and increase the safety of the operation. Using software to deal with the integration, segmentation and synthesis of tactile and visual images; Provide stable tactile control, identify different human tissues, and perform image recognition and image segmentation on key anatomical structures; Good tactile feedback and sense of position. The continuous development of MEMS technology provides technical support for micro-robots and even nano-robots. It can directly enter human organs to do work, and complete tasks that ordinary medical techniques and means can not accomplish, such as tissue sampling, blood vessel dredging, drug fixed-point placement, microsurgery, cell manipulation and so on. At present, foreign countries are developing microsurgical robots for autonomous walking in vivo, microsurgery in vivo and direct drug delivery in vivo. Doctors push the micro-robot into the human body with a syringe, and the microbial sensor carried by it detects human tissue. When the diseased tissue is found, the microsurgical robot performs direct surgery and drug injection treatment on the diseased tissue. The Institute of Robotics of Harbin Institute of Technology has successfully developed a nano-scale precision positioning system. The nano-scale high-precision micro-drive robot supported by the system can perform "microsurgery" on cells and chromosomes. Nano-robot can walk in the microscopic world of human body, remove all harmful substances in human body at any time, repair damaged genes, activate cell energy, and make people not only stay healthy, but also prolong their life. Medical robots apply robot technology to the medical field, which greatly promotes the development of modern medical technology and is one of the development directions of Modern China Medical Devices magazine. With the continuous updating of science and technology, the aging of society, the high-tech of modern warfare and the development of medical technology, various therapeutic robots and their auxiliary medical technologies will be deeply and widely studied and applied, which will promote the rapid development of medical robot technology. 3.2 Spatial positioning technology In the computer-aided navigation system, spatial positioning is the key to the whole system, which is directly related to the accuracy of the whole system and the success or failure of computer-aided surgery. Its function is to measure the spatial position and posture of surgical instruments in real time. According to the different positioning sensors, it can be divided into mechanical positioning, ultrasonic positioning, electromagnetic positioning and optical positioning. (1) Mechanical positioning Mechanical positioning is the original positioning mode of surgical navigation system, which belongs to passive positioning. The positioning manipulator must have at least 6 degrees of freedom, and each joint has an encoder. The position and rotation of the surgical instrument connected with the manipulator can be calculated by the geometric model of the manipulator and the instantaneous value of the joint encoder, and the typical accuracy is 2 ~ 3 mm The advantage of manipulator positioning is that it will not be blocked or blocked by obstacles, and the surgical instrument can be clamped or placed at a specific position. Disadvantages are that the operation is clumsy, the pressure exerted on the manipulator can change the data, and the fixing device and brake have displacement errors. Mechanical positioning is usually used for calibration and inspection of armless systems. (2) Ultrasonic positioning is to measure the distance between ultrasonic transmitter and receiver by measuring the propagation time of ultrasonic waves. By placing n (at least more than 3) transmitters on the surgical instrument, the position and posture of the surgical instrument can be calculated. The absolute accuracy of the system is generally 5 mm, and the main problems of ultrasonic positioning are the influence of temperature on ultrasonic, air displacement, air inhomogeneity and large emitter size. (3) Electromagnetic Positioning In the electromagnetic positioning system, each electromagnetic generating coil defines a spatial direction, and three coils determine three spatial directions, and then the spatial position of the target can be positioned according to the known relative position relationship. The accuracy of electromagnetic positioning system is 2mm. Electromagnetic positioning has high accuracy and belongs to non-contact positioning. However, the magnetic field of the system is very sensitive to the introduction of any metal objects in the workspace. (4) Optical positioning Optical positioning is the mainstream positioning mode in surgical navigation system at present. Using CCD camera as sensor, the measurement target is several infrared light-emitting diodes installed on surgical instruments, and the position and posture of surgical instruments can be calculated through the spatial position of infrared light-emitting diodes. According to the different cameras used, optical positioning can be divided into linear CCD and area CCD. The area array CCD measurement system consists of two table array CCD cameras. With a standard lens, each spot in the image defines a projection line in space. Two cameras in space can be used to calculate the intersection of the corresponding projection lines, thus obtaining the three-dimensional coordinates of the points. The linear CCD measurement system adopts cylindrical lens and consists of three linear CCDs with fixed relative positions. The vertical intersection between the measured point and the plane determined by the node axis of the lens and the sensitive element is the image of the measured point, and the spatial position of the measured point can be determined by the intersection of the three determined planes. Because the resolution of linear CCD can be very high (4096), its spatial resolution is very high. The accuracy of a typical linear CCD navigation system is 0. 5 mm, and the typical accuracy of area array CCD system is 1 mm ... The advantages of optical positioning system are high accuracy, flexible and convenient processing, but it is easily affected by hand occlusion, surrounding light and mirror reflection of metal objects during operation. 3.2 Virtual Reality technology, referred to as VR technology (English name is Virtual Reality). This term was put forward by Ranier, the founder of American VPL company, in the early 1980s, and translated by Qian Xuesen, a famous scientist in China, as "spiritual environment technology". It integrates simulation environment, vision system and simulation system, and uses sensing equipment such as helmet display, graphic glasses, data suit, stereo headphones, data gloves and pedals to connect the digital display and the digital display. Through the interaction between the sensor and the virtual environment, the operator can obtain a variety of senses such as vision, hearing and touch, and change the virtual environment according to his own wishes, which is called virtual reality.