Lightweight design and encoderless control of a miniature direct drive linear delta robot

This paper presents the design, integration and experimental validation of a miniature light-weight delta robot targeted to be used for a variety of applications including the pick-place operations, high speed precise positioning and haptic implementations. The improvements brought by the new design contain; the use of a novel light-weight joint type replacing the conventional and heavy bearing structures and realization of encoderless position measurement algorithm based on hall effect sensor outputs of direct drive linear motors. The description of mechanical, electrical and software based improvements are followed by the derivation of a sliding mode controller to handle tracking of planar closed curves represented by elliptic fourier descriptors (EFDs). The new robot is tested in experiments and the validity of the improvements are verified for practical implementation

Controling interactions in motion control systems

Design of motion control systems should take into account (a) unconstrained motion performed without interaction with environment or other systems, (b) constrained motion performed by certain functional interaction with environment or other system. Control in both cases can be formulated in terms of maintaining desired system configuration what makes essentially the same structure for common tasks: trajectory tracking, interaction force control, compliance control etc. It will be shown that the same design approach can be used for systems that maintain some functional relations like parallel robots

SMC framework in motion control systems

Design of a motion control system should take into account both the unconstrained motion performed without interaction with environment or other system, and the constrained motion where system is in contact with environment or has certain functional interaction with another system. In this paper control systems design approach, based on siding mode methods, that allows selection of control for generic tasks as trajectory and/or force tracking as well as for systems that require maintain some functional relation like bilateral or multilateral systems, establisment of virtual relation among mobile robots or control of haptic systems is presented. It is shown that all basic motion control problems - trajectory tracking, force control, hybrid position/force control scheme and the impedance control - can be treated in the same way while avoiding the structural change of the controller and guarantying stable behavior of the system In order to show applicability of the proposed techniques simulation and experimental results for high precision systems in microsystems assembly tasks and bilateral control systems are presente

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

An observer based approach to force reflecting bilateral teleoperation

Bilateral teleoperation systems are an active area of research with possible applications in healthcare, remote surveillance and military, space and underwater operations, allowing human operators to manipulate remote systems and feel environment forces to achieve telepresence. The physical distance between the local and remote systems introduces delay to the exchanged signals between the two and cause instability in the bilateral teleoperation. With the advent of the internet, possible applications of bilateral teleoperation systems have proliferated, growing the interest and amount of research in the field. The delay compensation method for stable and force reflecting teleoperation proposed in this thesis is based on utilization of three different types of observers: A novel predictor observer that estimates the undelayed states of the remote system based on a nominal model, disturbance observers that eliminate internal and external disturbances and linearize the nonlinear dynamics of the two systems, and reaction torque observers that estimate the net external forces on the two systems. The controller for the remote system is placed at the local site, along with the predictor observer and the control input is sent to the remote system through the communication channel. Force reflection is achieved using a modified version of the 4-channel architecture where control input and position of the remote system and the environment force estimations are exchanged between the two systems. Performance of the proposed method is tested with Matlab/Simulink simulations and compared to two other methods in the literature. Real-time experiments under variable communication delay are also performed where the delay is both artificially created using Matlab/Simulink blocks and obtained via the internet by bouncing signals off a remote computer outside the Sabancı University campus. Both the simulations and experiments are executed on a pair of 1-DOF robot arms and a pair of 2-DOF pantograph robots. The results show that stable and force reflecting teleoperation is achieved with successful tracking performances of the remote system