Automated Manipulation Of Microparticles Using A Robotically Controlled Electromagnetic Coil System

Electromagnetically steering microparticles exhibit great potential for various biomedical applications because of their minimally invasive capability and accessibility in intricate microenvironments.Autonomous research on electromagnetic manipulation of microparticles has been performed over the past several decades.Existing manipulation methodologies are designed under ideal conditions without considering system uncertainties or only addressed specified uncertainty issues.In reality,microparticles are steered in a complex environment with multifarious uncertainties.In this thesis,a uniform robust control approach is developed to precisely manipulate microparticles actuated by a robot-aided electromagnetic coil system while maintaining the stability of the entire system.This study is performed in the three following perspectives.First,this research work proposes an approach that utilizes an electromagnetic coil system to automatically manipulate the microparticles for trajectory tracking.Fe304 nanoparticle polymer microbeads coated with hydrophilic agarose polymer are used because of their superparamagnetism and biocompatibility.The electromagnetic coil system is employed as a micromanipulator to track the magnetic microbeads in the fluid environment.This method can be potentially used for precise delivery of the targeted materials in the in vivo environment.Experiments on tracking microparticles along a desired trajectory are also performed to demonstrate the effectiveness of the proposed approach.Second,a uniform robust control scheme is developed to manage diverse system uncertainties is developed.The "input-to-state stability"(IS S)theory is incorporated into the backstepping design,such that the controlled system can satisfy ISS.This method is successfully applied to control the microparticles to follow the desired trajectories while maintaining stability in the entire system,even under unknown environmental disturbances.A fault-tolerant ISS-based control is further developed to address the problem of insufficient magnetic driving force due to magnetic loss in the coil system.This study is among the first works to develop a robust closed-loop controller,which incorporates ISS theory into the backstepping design to manage diverse system uncertainties for magnetic manipulation of microparticles.Third,a nonlinear high-gain observer is designed for velocity estimation of the robotically controlled electromagnetic coil system.In the nonlinear-observer,a higher gain is used to suppress the estimation error,and a lower gain is utilized to reduce the steady state error.The combination of the ISS theory and the observer-based control allows the proposed control approach,which does not rely on direct measurement of velocity,to achieve the control objective under system uncertainties and measurement noise.Simulations and experiments are performed to demonstrate the effectiveness of the proposed control approach.In summary,the proposed electromagnetic coil-based manipulation system provides a useful tool for the study of microparticle steering.The proposed uniform robust control scheme solves the challenging problem of ubiquitous system uncertainties which may significantly degrade the control performance.Velocity estimation avoids the difficulty of measuring particle velocity via visual feedback.This study provides a basis for precise motion control with high throughput in applications of the targeted material delivery.