| Capsule robot has become a hot research topic in the field of non-invasive and minimally invasive treatment. Wireless magnetic drive technology provid an effective way for non-contact as well as non-invasive driving method of the capsule robot, which can reduce the treatment cycle, relieve the pains of people and so on, has an inestimable practical value.Turning drive of the capsule robot in curved environment is a problem which has not been resolved for a long time, and also become the main technical bottleneck for the application of the capsule robot. The turning characteristics of the capsule robot has been researched in theoretical and experimental in this paperFirstly, for driving the capsule robot moving in any curved environment, we propose a technical scheme that three axis orthogonal square Helmholtz coils is employed to generate a spatial universal rotating uniform magnetic field by three harmonic currents with the same frequency and relevant amplitude and phase. A magnetic field generator and power source with three phase frequency conversions are developed, and demonstration experiments have been conducted successfully for verifying universal rotating magnetic field. Magnetic moment modeling is derived according to magnetic coupling mechanism, and based on Euler equation, swinging equation is derived, the relationship between follow-up moment and steering angle, as well as between spin moment and steering angle, have been studied, finally, the stability of capsule robot and effect on capsule robot influenced by magnetic moments have been analyzed.Then, based on position angles of Resal coordinate system attached to the robot, the stability of the capsule robot in curved environment is analyzed, then the film thickness equation and fluid dynamic pressure model in curved environment are established. According to the two-dimensional Reynolds equation and Navier-Stokes equation, the kinetic equation of the capsule robot is established, the general solution is derived employing the variational functional and rayleigh step bearing method. Finally, the dynamic characteristics of the capsule robot in curved environment is investigated, and compared with the capsule robot in straight environment, then analyzed the experimental parameters.According to the mathematical model and the equilibrium equation, using matlab and simulink toolbox to solve kinematics and dynamics equations of the capsule robot and then study the relevant motion characterristics. Based on the function curve and dynamic response, turn swimming characteristics of the capsule robot is analized.Finally, the experiments of turn driving of the capsule robot and the strength, uniformity of the magnetic field are implementated. The result show that the universal magnetic field generating device can produce a uniform rotating magnetic field, and the driving principle and strategies is feasible to achieve horizontal turning drive, tilt turning drive and vertical turning drive. At last, walking experiments of the capsule robot in vitro pig intestinal environment are finished, and achieved satisfactory results. |
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