The Research And Experiments Of A Micro Robot System For Gastrointestinal Diseases Diagnoses And Treatments

The diseases of the digestive tract became a significant problem in humanhealthcare. Nowadays, the actively locomotive diagnoses and treatment systemon the gastrointestinal (GI) tract is one of the focus points in the research of thebiotechnology worldwide. In the funding of the national, provincial andministerial-level projects, by the technology of micro mechanism, micro actuator,micro sensing and micro electronics, the intestinal micro robot system whichfaces the clinical application is researched.According to the working environment of the intestinal micro robot, firstly,the specific physiological environment and biomechanical features are analyzed,and the gait of anchoring and extending is proposed. The motion of this robotmainly consists of two parts, extending in axial direction and anchoring in radialdirection. Secondly, the motions are analyzed in following aspects: the dampingand friction between the robot and the intestinal inner wall; the anchoring abilitybecause of the support of legs in the radical direction; the locomotion conditionof the robot; and the locomotion efficiency due to the elasticity of the intestinaltissues. Based on the above analyses, combining the hyper elastic model whichdescribes the stress-strain relation of the intestinal, a mathematical model thatdescribes the relationship between the robot parameters and critical step isdeduced. To obtain some key parameters in the critical step model, a robotsimulation model is used in in-vitro experiments, and the relation between themodel speed and the resistance force is acquired. Finally, the results in theexperiments are used to solve the critical step model and the range of some keyparameters and some guidelines in robot design processes are deduced.With the optimized parameters range, micro direct current motor is selectedas robot actuator, and the mechanical system and its control system is designed and fabricated. By the discussion of principle of machinery and the calculationof mechanical property, the anchoring mechanism is designed in three forms andthe extending mechanism is in two forms. Meanwhile, the robot control systemis designed in two parts, on-board motion control and external console, and thehardware of on-board system is realized by the micro electronic technique, thecontrol algorithm and the human interface is programmed. Third generation ofthe robot prototype measures13mm in diameter,90mm in length and22g inweight, and by these parameters, the robot kinetic characteristic is analyzed, theload characteristic is calculated.To increase the locomotion efficiency and reduce the GI tract damageprobability, a vision based robot steering system is proposed and researched.According to the real endoscopy image, a dark zone navigation method isproposed. The algorithm is consistsed of brightness feature extraction, imagesegmentation and dark zone center calculation. The steering vector in the imagespace, which is calculated by the algorithm, can be mapped into the controlledvariable space and forms a close loop control of the visual navigation system.By using real endoscopy image in the small intestine, details of the algorithm isdescribed. The accuracy and the speed of the navigation algorithm are tested byusing a small intestine endoscopy image database.The mechanical feature of the micro intestinal robot prototype is tested, andthe prototype is used in an in-vitro experiment. Firstly, the relation between theanchoring leg length and the stall force, and the extending speed and the outputforce of robot prototypes are tested. Secondly, while the performance of eachmechanism fulfills the requirements, the robot was tested in both horizontal andvertical simulation tube for the relation of its load and speed. Thirdly, the robotis tested in in-vitro experiments by using the pig’s small intestine. The resultsshowed that the performance in diameter adaptability of the robot is the same asthe design, and the robot is locomotive in the intestinal model, which simulatesthe intestine is well supported by the mesentery.As mentioned above, this thesis proposes critical step model based on ahyper elastic model for the GI robot firstly. Under the direction of the model, the mechanical system and the control system is designed and fabricated, the kineticcharacteristic is analyzed. Meanwhile, to make the robot working safely andeffectively in GI tract, a vision based navigation system, which using dark zoneextraction, is designed and discussed. Finally, the prototypes are tested and theentire design and fabrication is verified in experiments. The gait of anchoringand extending is tested in in-vitro experiments.