Research On Capsule Robot Veering Dynamic Behavior

Active drive and control of oral capsule robot, which can reduce diagnosis and healing time and alleviate patient's suffering, is becoming a research hotspot and leading edge in minimally invasive or noninvasive treatment both at home and abroad.Based on previous research, this paper proposed the utilize of space universal rotating magnetic field (SURMF) to drive and control robot non-contact steering in curved pipe filled with viscous fluid. A magnetic field control strategy of discrete approximation is proposed and steering kinetic equations are established, aiming at providing theory basis for selecting optimal magnetic parameters by analyzing robot's kinetic motion to realize its active steady steering.A new capsule robot is proposed and its structure is presented in this paper. Firstly, the principles of SURMF generation and robot's steering drive are elaborated. When rotating axis of SURMF is not parallel to that of robot, magnetic driving moment component, produced by SURMF coupling with robot's inner actuator, emerges in the direction perpendicular to robot's rotating axis, which drive robot to turn.In this paper non-stationary motion Reynolds equation is given, and the finite difference method and flow control at the side of spiral ribs are used to solve Reynolds equation, the later solve the problem that Reynolds equation with complicated thickness function of hydrodynamic film can't be directly solved.As a result of operating lag caused by coil inductive impedance of SURMF generating device, which determined the rotating direction of SURMF can't be continuously changed, a discrete control strategy is proposed to control robot's walk path so that to be approximated to pipe's diametral curve. Based on the control strategy, Resal coordinate system is introduced to determine robot's posture.On the basis of coupling theory of space magnetic vectors, model of magnetic driving moment acting on robot in any posture by SURMF coupling with inner actuator is established, and whose component that perpendicular to robot's rotating axis induces robot to turn and swing. Robot's pose and kinetic motion influence on the moving fluid in pipe. The hydrodynamic film formed by flow in pipe respectively creates damping effect and resistant effect in response to robot's swig and change of its pose. Based on the both effects, model of fluid moment acting on robot by hydrodynamic film is established.On the basis of gyrodynamics and Euler dynamic equations of robot rotating about a fixed point, and combining with the moment models mentioned above, robot steering kinetic equations are derived. Robot kinetic equations are solved with the use of Simulink toolbox provided by MATLAB, and robot kinetic motion is simulated and analyzed. Follow-up effect of robot is proved in analyzing the moment's response curve. Influence of magnetic field control parameters on robot steering motion is analyzed and discussed.