Magnetic Microrobot Locomotion in Vascular System Using A Combination of Time Delay Control and Terminal Sliding Mode Approach

This thesis deals with designing a control law for trajectory tracking. The target is to move a microrobot in a blood vessel accurately. The microrobot is made of a ferromagnetic material and is propelled by a magnetic gradient coil. The controller combines time delay control (TDC) and terminal sliding mode (TSM) control. TDC allows deriving a control law without prior knowledge of the plant. As the system is a nonlinear function which also includes uncertainties and unexpected disturbance, TDC gives a benefit of less effort needed compared to model-based controller. Meanwhile, TSM term adds accuracy which it compensates TDC estimation error and also adds robustness against parameter variation and disturbance. In addition, anti-windup scheme acts as a support by eliminating the accumulated error due to integral term by TDC and TSM. So, the proposed controller can avoid actuator saturation problem caused by windup phenomenon. Simulations are conducted by copying a realistic situation. Accuracy and robustness evaluations are done in stages to see how each terms in a control law give an improvement and to see how an overall controller performs. ⓒ 2014 DGISTI. INTRODUCTION 1 -- 1.1. BACKGROUND 1 -- 1.2. RELATED RESEARCH 3 -- 1.3. OBJECTIVE 4 -- 1.4. SPECIFICATION 4 -- 1.5. SCOPE 5 -- 1.6. OVERVIEW 5 -- II. METHOD 6 -- 2.1. TIME DELAY CONTROL 6 -- 2.2. TERMINAL SLIDING MODE 9 -- 2.3. ANTI-WINDUP SCHEME 11 -- 2.4. PRACTICAL APPROACH 14 -- 2.4.1. FEEDBACK SIGNAL 14 -- 2.4.2. CONTROLLER GAIN SELECTION 15 -- 2.4.3. MEASUREMENT NOISE 16 -- 2.5. ADVANTAGES AND DRAWBACKS 16 -- III. RESULTS 17 -- 3.1. SIMULATION SETUP 17 -- 3.1.1. PLANT MODELING 18 -- 3.1.2. ACTUATOR AND POSITION SENSOR MODELING 20 -- 3.1.3. TRAJECTORY 21 -- 3.1.4. SIMULATION PARAMETER 21 -- 3.1.5. CONTROLLER TARGET 24 -- 3.2. ACCURACY AND ROBUSTNESS EVALUATION 24 -- 3.3. ANTI-WINDUP SCHEME EVALUATION 32 -- 3.4. SOLUTION FOR MEASUREMENT NOISE 35 -- 3.5. 2D SIMULATION 46 -- CONCLUSION AND FUTURE WORK 49 -- REFERENCES 50 -- 요 약 문(ABSTRACT IN KOREAN) 52이 논문은 경로 추적을 위한 컨트롤 법을 설계한 것이다. 목표는 혈관 내에서 정확하게 마이크로 로봇의 움직이는 것이다. 마이크로 로봇은 강자성체 물질로 만들어져 있고 자기장에 의해서 추진 된다. 컨트롤러는 시간지연제어기법(time delay control)과 terminal sliding 컨트롤을 함께 사용하였다. TDC는 플랜트에 대한 선행 지식 없이 적용할 수 있다. 시스템이 불확실함과 예상치 못한 외란을 포함하고 있는 비선형 일 때 TDC는 모델 기반의 컨트롤러에 비해 적은 노력이 드는 장정이 있다. 한편, TSM은 정확도를 더하여 TDC의 주정에러를 보상하고 또한 매개변수의 변화와 외란에 반한 견고함을 더한다. 게다가 안티 와인드 업은 TDC와 TSM의 적분 때문에 축적되는 에러를 제거하는 역할을 한다. 제안한 컨트롤러는 와인드업 현상에 의한 작동기의 포화현상을 피할 수 있다. 시뮬레이션은 실제 현상을 따라 시행되었다. 정확도와 견고함 평가는 전체적인 컨트롤러가 어떻게 수행하는가를 보는 것과 각각 컨트롤 방법이 주는 개선점을 보는 단계로 실시하였다. ⓒ 2014 DGISTMasterdCollectio

Adaptive Backstepping and MEMS Force Sensor for an MRI-Guided Microrobot in the Vasculature

International audienceA microrobot consisting of a polymer binded aggregate of ferromagnetic particles is controlled using a Magnetic Resonance Imaging (MRI) device in order to achieve targeted therapy. The primary contribution of this paper is the design of an adaptive backstepping controller coupled with a high gain observer based on a nonlinear model of a microrobot in a blood vessel. This work is motivated by the difficulty in accurately determining many biological parameters, which can result in parametric uncertainties to which model-based approaches are highly sensitive. We show that the most sensitive parameter, magnetization of the microrobot, can be measured using a Micro-Electro-Mechanical Systems (MEMS) force sensor, while the second one, the dielectric constant of blood, can be estimated on line. The efficacy of this approach is illustrated by simulation results