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It has been found that magneto-rheological (MR) devices can produce large controllable force/torque while consuming little power. In this research, an MR actuator that can function as a clutch or a brake is developed, in order to be applied to an assistive knee brace. The torque capability and dynamic characteristics of the MR actuator are evaluated. The relationship between the torque output and the applied coil current is given. The response time is also measured. Experimental results show that the MR actuator can provide enough torque for normal activities with sufficiently fast response. IP control and adaptive control are proposed to control the MR actuator. Experiments under these controls are carried out. With anti-windup strategies, both controls achieve good performances. However, adaptive control would be more promising since it can adapt to parameter variations and maintain good performance. An assistive knee brace that contains this MR actuator and a DC motor is developed. In order to study the performances of the knee brace before applied to human body, experiments are conducted for evaluation under a custom-built testing structure. IP-based state control and adaptive control are used to control both the MR actuator and DC motor. Experimental results demonstrate that the MR actuator and DC motor work well together to provide assistance as expected. Compared with that without MR actuator, the evaluation results show that the knee brace with MR actuator is more energy efficient during normal walking, while having better force controllability and safety. / by Chen, Jinzhou. / Adviser: Liao Wei Hsin. / Source: Dissertation Abstracts International, Volume: 73-01, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 140-151). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

In this research, a novel magnetorheological (MR) fluids based multifunctional actuator for assistive knee braces is designed. To decrease the dimension of the actuation device while enhancing its perfonnances, a motor and MR fluids are integrated into a single device. With MR fluids, the actuator possesses multiple functions as motor, clutch, and brake while meeting the requirement of nonnal human motion as well. In this thesis, design details and operating principle of the actuator are illustrated, and possible configurations of the motor part and clutch/brake part are discussed. Finite element method is utilized to analyze the magnetic circuits, influence of pennanent magnet on MR fluids, and magnetic flux distribution. Different clutch/brake parts with various inner coils are compared and analyzed, followed by a design optimization to improve the output torque. Prototypes of the multifunctional actuator are fabricated and tested, and characteristics of each function are investigated. As the actuator has multiple functions, modeling is developed for different functions, and system identification is carried out to determine the parameters. Adaptive control is utilized to control the actuator for torque and speed tracking. A smart joint using such a multifunctional actuator is designed, and its prototype is fabricated and tested. Power consumptions of knee brace using the smart joint are investigated during normal walking cycle. The results show that the developed actuator and smart joint are promising to be used in assistive knee braces. / Guo, Hongtao. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 154-158). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Han, Zuoyan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 43-46). / Abstracts in English and Chinese. / Abstract (Chinese) --- p.i / Abstract (English) --- p.ii / Acknowledgements --- p.iv / Glossary --- p.vi / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Physics parameter viscosity --- p.1 / Chapter 1.2 --- PDMS microfluidics device --- p.4 / Chapter Chapter 2 --- PDMS viscometer for microliter Newtonian fluid / Chapter 2.1 --- Introduction --- p.5 / Chapter 2.2 --- Configuration of the PDMS Viscometer --- p.8 / Chapter 2.3 --- Mechanism of passive pumping --- p.10 / Chapter 2.4 --- Theory of the PDMS viscometer --- p.11 / Chapter 2.5 --- Viscosity Measurement in PDMS Viscometer --- p.15 / Chapter 2.5.1 --- Preparation of Blood Plasma --- p.16 / Chapter 2.5.2 --- Measurements of Glycerol Solutions --- p.16 / Chapter 2.5.3 --- Measurements of Protein Solution and Blood Plasma --- p.19 / Chapter 2.5.4 --- Measurements of Organic Solvents --- p.19 / Chapter 2.6 --- Data Analysis --- p.21 / Chapter 2.7 --- Dynamic Contact Angle --- p.22 / Chapter 2.8 --- Conclusions --- p.23 / Chapter Chapter 3 --- PDMS viscometer for microliter Non-Newtonian fluid / Chapter 3.1 --- Introduction --- p.25 / Chapter 3.2 --- Configuration of the PDMS viscometer --- p.29 / Chapter 3.3 --- Theory for non-Newtonian fluid --- p.31 / Chapter 3.4 --- Viscosity Measurement of non-Newtonian fluids --- p.35 / Chapter 3.4.1 --- Preparation of Blood Plasma --- p.36 / Chapter 3.4.2 --- Measurement of starch solutions --- p.36 / Chapter 3.5 --- Data analysis --- p.37 / Chapter 3.6 --- Conclusion --- p.41 / References --- p.43

While rheological and microstructural complexities have posed tremendous challenges to researchers in developing first principles models and simulation techniques that can accurately and robustly predict the dynamical behaviour of polymeric flows, the past two decades have offered several significant advances towards accomplishing this goal. These accomplishments include: (1). Stable and accurate formulation of continuum-level viscoelastic constitutive models and their efficient implementation using operator splitting methods to explore steady and transient flows in complex geometries, (2). Prediction of rheology of polymer solutions and melts based on micromechanical models as well as highly parallel self-consistent multiscale simulations of non-homogeneous flows. The main objective of this study is to leverage and build upon the aforementioned advances to develop a quantitative understanding of the flow-micro-structure coupling mechanisms in viscoelastic polymeric fluids and in turn predict, consistent with experiments, their essential macroscopic flow properties e.g. frictional drag, interface shape, etc. To this end, we have performed extensive continuum and multiscale flow simulations in several industrially relevant bulk and free surface flows. The primary motivation for the selection of the specific flow problems is based on their ability to represent different deformation types, and the ability to experimentally verify the simulation results as well as their scientific and industrial significance.

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