Research On Modeling Of Spatial Composite Gradient Magnetic Field Generation And Control Strategy For Microrobot 3D Drive

So far,the operation of microrobots on micro-nano scale is an emerging research.This technology has great application potential in the field of biomedicine.microrobots can be used as a carrier for targeted drug delivery,or as a surgical tool for minimally invasive treatment and diagnosis.Among the various driving modes of microrobots,magnetic field driving technology is widely used in the driving control of microrobots due to its nondestructive effect on organisms,strong penetration and remote controllability.After more than ten years of development,the research on magnetically driven microobots has changed from two-dimensional to three-dimensional,from open-loop control to closed-loop control,and from single control to group control.However,microrobots will be subject to various disturbances in complex environment,which bring great challenges to the precise motion control of microrobots.At the same time,how to ensure that a relatively large working space can produce a strong magnetic gradient is a problem that the existing three-dimensional electromagnetic drive system needs to solve.Therefore,this paper firstly proposes a robust control method to solve the problem that the motion of microrobots is easily disturbed in the plane space.Then,based on the research of the two-dimensional electromagnetic drive system,a three-dimensional electromagnetic drive system of microrobots with strong magnetic field gradient is developed and verified by experiments.The main work of this paper is as follows:(1)Firstly,the motion control of microrobot in plane space is studied.Microrobot is vulnerable to various disturbances in complex environment,which will affect the control accuracy of microrobot.So this paper proposes a robust motion control method for microrobot based on extended state observer(ESO),and carries out experimental verification in the complex environment of simulating vascular structure.Firstly,a two-dimensional electromagnetic drive system for planar motion of microrobot is briefly introduced,and then the magnetic force model and dynamic model of microrobot are analyzed.Based on this model,an extended state observer is designed to estimate the total disturbances and uncertainties of the system.At the same time,a path tracking controller is designed combining sliding mode control(SMC)and disturbances compensation.Finally,the experiments of microrobot tracking paths in a planar gradient magnetic field drive system are carried out.The experimental results show that the robust control method proposed in this paper can realize the path tracking control of microrobot in a complex environment,and shows stronger anti-interference ability and robustness compared with other control method.(2)Then,on the basis of the two-dimensional electromagnetic drive system,the end structure of the iron core is improved to produce a nearly uniform gradient magnetic field in the three-dimensional space.The finite element method is used to optimize the parameters at the end of the core so that the magnetic field gradient,magnetic flux density,magnetic field uniformity and working space meet the requirements.A three-dimensional electromagnetic drive system with strong magnetic field gradient is established,and the system has a considerable working space.The magnetic field of the designed three-dimensional electromagnetic drive system is analyzed,including the magnetic field consistency analysis of six iron core coils,the magnetic field simulation and experimental comparison analysis,the verification of the linear relationship between the magnetic field distribution and the current,and the magnetic field simulation analysis in three-dimensional space.Finally,a magnetic microrobot is designed to operate in three-dimensional space,and then the three-dimensional dynamic model of the microrobot is analyzed.(3)Finally,three-dimensional closed-loop motion control of microrobot is carried out.Firstly,the hardware platform and software platform for the three-dimensional closed-loop control experiments of the microrobot are designed.After the basic experimental conditions are prepared,the drive experiments of microrobot are carried out.The experiments prove that the microrobot can be driven effectively in the three-dimensional liquid environment.Aiming at the problems existing in the three-dimensional driving experiments of the microrobot and the three-dimensional force analysis of the microrobot,the gravity compensation method is proposed to eliminate the influence of gravity and simplify the three-dimensional motion control of the microrobot.The gravity compensation experiment verifies the effectiveness of the method.Finally,the three-dimensional path tracking experiments of the microrobot are carried out in the three-dimensional electromagnetic drive system,which verifies that the designed three-dimensional electromagnetic drive system can realize the three-dimensional closed-loop motion control of the microrobot.