Research On Generation And Control System Of Magnetic Driving Force Of Micro-nano Operation Robot

As the potential of micro-robots in the field of biomedicine has been developed,such as drug delivery,targeted therapy,minimally invasive surgery,etc.The wireless drive of micro-robots has also attracted the attention of scholars.In addition,the electromagnetic field drive is harmless to the organism,can penetrate deep tissues,and generate a real-time controlled dynamic magnetic field by changing the input current.Therefore,the electromagnetic coil drive has been widely used in the drive control of miniature magnetic robots.In order to be successfully applied in the field of biomedicine,a magnetic drive system with fast response and high accuracy is essential.The coil inductance of the magnetic drive system causes a delay in the input current of the coil,which affects the response performance.At the same time,the sampling interval of the visual feedback of the closed-loop control system is too long,so the unknown position between frames will cause oscillation.In view of the above problems,the electromagnetic coil drive system adopted in this paper is improved to improve the performance of the magnetic drive system,which has important research significance and value.This article mainly does the following work:Firstly,analyze the basic theory of the magnetic drive system and the electromagnetic coil model used in this article.Two typical coils,Helmholtz coil and Maxwell coil,are used to generate a uniform magnetic field and a uniform gradient magnetic field in space,respectively to achieve two basic motion modes of magnetic particles in the magnetic field.The two coil models are analyzed and the combined coil model is built.The micro-robot is dynamically modeled and the mapping matrix of input current,output magnetic field and magnetic field gradient is analyzed.Finally,the combined coil model of the magnetic drive system is built in the multiphysics simulation software COMSOL,and the generated magnetic field and magnetic field gradient are subjected to finite element simulation and the related mathematical model is verified.Secondly,for the problem of electromagnetic coil drive delay,a full state feedback controller based on auto disturbance rejection technology is proposed.A circuit board based on a power inverter is used to control the voltage applied to the coil,and the problems existing in the conventional controller are analyzed.A full-state feedback controller is designed based on auto-disturbance rejection technology,and simulation analysis is performed in MATLAB software.At the same time,compared with the traditional PID control and open-loop control,the step response,sinusoidal response,and impulse response are simulated separately to verify that the designed controller can achieve two important purposes: 1)the output magnetic field and magnetic field gradient can converge reference point;2)The best transient response possible.Thirdly,the closed-loop control scheme of the magnetically driven micro-robot system is proposed.The Hough transform is used to detect the micro-robot,as to realize the position feedback of the micro-robot in the closed-loop control.The control system has respectively designed a direction control module and a position control module.The direction control module uses direction closed loop,and the position control module uses position,velocity,acceleration three closed loop control.In view of the problem that the sampling frequency in visual feedback is slow and the real-time position cannot be fed back to the control system,a Kalman filter algorithm is used to predict the position between frames.Finally,build an experimental platform for experimental analysis.For the electromagnetic coil system proposed in this paper,several experiments were carried out: 1)the gaussmeter was used to verify the uniformity of the designed combined coil magnetic field;2)the rotation experiment was performed on the micro robot to verify the performance of the rotating magnetic field,so the micro robot verification of directional control;3)Micro-robot drive experiments under open-loop control,PI control,and auto-disturbance control,respectively,to verify the performance of the auto-disturbance controller proposed in this paper;4)Close-loop drive control experiment of micro-robot,drive the robot to move along the given square and "S" path respectively,and compare the trajectory and error of the micro robot with or without Kalman filter,to verify the excellent performance of the position error compensation algorithm proposed in this paper.