Key Techniques And Experimental Research On Bionic Micro Robot System For Direct Respiration Parameters Monitoring

With the development of science and technology, a lot of attention has been paid to the research on a micro robotic system which can enter human's cavities to diagnose with minimal invasive or non-invasive by applying the bionics principle and MEMS technology. Under the support of the National High Technology Research and Development Program of China (863 PROGRAM:2004AA404013), this paper focuses on the research of a miniature bionic micro robotic system for medical purpose.The robot is to be capable of moving actively in human's respiratory system and monitoring respiration parameters directly and continuously in the inner microenvironment of a human's lung. Based on the knowledge of the physical structure characteristics of human's respiratory system and the maintenance of normal respiratory function, the key technical issues including, but not limited to, configuration of the robot, motion principle, robot control, robtot kinemics charateristis and the relationship between robot and inner respiratory environment have been discussed in this paper, and a series of experiments have been conducted. The aim is to develop a new and active robotic system for diagnosing of human's respiratory system with minimal invasive and to provide a new idea and reference for the design of robotic system for diagnosing of human's cavities. The main technologies are as follow:1. Based on the analysis of the research on direct tracheal monitoring and therapy methods throughout the world, by applying the bionics principle, the general system scheme is presented according to the physical structure and physiological characteristics of the human respiratory system.(1) Locomotion principleBy analysing the moving characteristics of the inchworm, the bionics locmotion principle was obtained. The robot was designed in the movement of inchworm-like. to the robot body is flexible structure, it is consistent of a middle actuating unit, a head holding unit and a rear holding unit, the actuating unit is used to drive the robot body in movements, and the holding units is used to hold the robot position in movements.(2) ActuatorA robot directly contact with the huaman body should be safe and flexible. After comparison of the actuation principle, control style and performance of several actuator types such as magnetic type, magnetic-piezo composite type, micro motor type and pneumatic pressure type, the pneumatic pressure was selected to be the supply power resource of the robot system. The robot is total pneumatic pressure actuating system. A new pneumatic artifical muscle rubber actuator was made of specialy. The actuator has three chambers with the same fan-shaped cross section. It can drive the robot in axis and in any bending direction by changing the air pressures in the three actuator chambers. Every holding unit is a plastics cylinder coverd with a thin elastic air chamer outside, it will hold tightly when pressurized.(3) Sensor mechanicsmThe micro sensors, micro CCD and other micro operation mechanisms can be equipped in the head holding unit.(4) Control systemAn outside electro- pneumitc pressure control system with man–machine interface was designed to control the robot moving, to collect and prosess data and so on. The control system is mainly made up of a computer, a data card, driving circuits, relays, magnetic valves, pressure sensors, high pressure generator and pressure regulators.The programs was designed to control the robot system by the control system.According to the above scheme, the prototype of the robot and an electro-pneumatic pressure experimental control system with interface was designed, and the experimental study on the moving characteristics of the prototype had been done in a pipe. The robot prototype could move smoothly and steadly with high speed and enough driving force.2. In order to have a further analysis on the kinemics characteristics of the robot, the dynamic characteristics of the robot system have been discussed in detail.(1) Driving characteristics of the pneumatic pressure atificial muscle actuator The driving models of the atificial muscle actuator had been set up and experimental researches had been done on the actuator. The axial and bending characteristis models the of the pneumatic pressure artificial muscle actuator were set up according to the energy conservation law and the infinitesimal deformation theory respectively, and simulation researches and experiments had been done for the characteristics of the actuator. (2) Pressure in holding chambersThe charged holding chambers must hold tightly in the movement process, so the pressure in holding chambers must be over some value to provide enough holding force. On the other hand, if it is very high, it will do harm to the inner wall tissues of the trachea.So the proper pressures in holding chambers had been discussed according to the pressure of the chamber in a trachral intivention tube.(3) Damp forcesThe robot with wires is designed to move in respiratory tract, so the damp forces are form wires and air fluid, the effect of the damp forces on the moving robot were discussed, that will be a base for the optimal robot structure and the moving in human respiratory tract for direct parasmers monitoring. Thus the kinemics equations of the robot had been obtained, and the load to the robot was discussed too.3. The movement control and control characteristics of the robot system(1) Movement controlBased on the FSM (Finite State Machine), the moving states of the robot in one step moving cycle were analyzed and defined, and the computer program were designed for high efficiency control. By the program and the interface of the control system the robot can be control effectively.(1) Control characteristics of the systemThe Non-linear robot system control model of the pneumatic pressure– position servo system was set up and studied. The fuzzy adapting PID control had been adopted, and the experimental simulation results indicate the system have good performances. In order to control the robot system more accurately, a fuzzy wavelet neural network swas proposed for the robot system, and the simulation results show that the network can be well applied to the robot system, it has better statatic and dynamic control performances, and also has the capability of anti-jamming.4. During mechanical ventilation, high airway resistance will affect the respiration fuction, so the airway resistance is one of the important monitoring parameters.The robot system in trachea will be of extra resistance, thus resistance characteristics of the robot in trachea were studied with hydrodynamics theory under different fliud states. Comparing to the total airway resistance, the predicted extra resistance of the robot is very small.5. As the swine respiration system and the humanrespiration syste are most similar, so the experimental research on the robot system had been done in a normal swine respiratory system during mechanical ventilation. The robot could move smoothly and steadly in the swine's trachea, and the pressures and the temperatures in the swine tracheal end were measured continuously by sensors equipped in the robot system. The results measured by the robot system shown the airway resitances were normal, and inner measurements are consistent with outside results shown by ventilator.Theoretical and experimental researches indicate that the bionics micro robot system is suitable to the inner hunman respiratory system. It can move smoothly in respiratory tract, and it is capable of monitoring respiratory parameters dynimicaly and continuously. The production of this dissertation affords a new idea and theory reference for the development of the robot system which can promote the development of practical miniature robot for medical purpose.