Tracking Control of Uncertain Nonholonomic Mobile Robots: Smooth Switching Approach

ABSTRACT Backstepping based adaptive tracking control of nonholonomic mobile robots in the presence of both kinematic and dynamic parametric uncertainty is presented. The major challenge is the possible singularity phenomenon due to the approach of zero of the estimated input vector field entering the denominator of the control input, a common drawback of adaptive linearization-based schemes. A hybrid control approach, which switches between an adaptive and a robust control schemes, is developed for solving such a problem. It retains the advantage of an adaptive control approach to a greatest extent while avoiding the possible blowup of the torque inputs simultaneously. A case study on a specific Type (2; 0) mobile robot is provided in the final to verify the usefulness of the proposed design

Women with endometriosis have higher comorbidities: Analysis of domestic data in Taiwan

AbstractEndometriosis, defined by the presence of viable extrauterine endometrial glands and stroma, can grow or bleed cyclically, and possesses characteristics including a destructive, invasive, and metastatic nature. Since endometriosis may result in pelvic inflammation, adhesion, chronic pain, and infertility, and can progress to biologically malignant tumors, it is a long-term major health issue in women of reproductive age. In this review, we analyze the Taiwan domestic research addressing associations between endometriosis and other diseases. Concerning malignant tumors, we identified four studies on the links between endometriosis and ovarian cancer, one on breast cancer, two on endometrial cancer, one on colorectal cancer, and one on other malignancies, as well as one on associations between endometriosis and irritable bowel syndrome, one on links with migraine headache, three on links with pelvic inflammatory diseases, four on links with infertility, four on links with obesity, four on links with chronic liver disease, four on links with rheumatoid arthritis, four on links with chronic renal disease, five on links with diabetes mellitus, and five on links with cardiovascular diseases (hypertension, hyperlipidemia, etc.). The data available to date support that women with endometriosis might be at risk of some chronic illnesses and certain malignancies, although we consider the evidence for some comorbidities to be of low quality, for example, the association between colon cancer and adenomyosis/endometriosis. We still believe that the risk of comorbidity might be higher in women with endometriosis than that we supposed before. More research is needed to determine whether women with endometriosis are really at risk of these comorbidities

Adaptive Fuzzy Sliding Mode Control of Omnidirectional Mobile Robots with Prescribed Performance

Adaptive fuzzy sliding-mode control design for omnidirectional mobile robots with prescribed performance is presented in this work. First, an error transformation which transforms the constrained variable into an unconstrained one is carried out. Next, a fuzzy logic system (FLS) for approximating the unknown dynamics is constructed. Based on such a model, a nominal adaptive linearizing controller incorporating a serial-parallel model (SPM)-based composite algorithm, which improves the tracking performance of the overall closed-loop system, is synthesized. To solve the so-called “loss of controllability” problem, a smooth-switching algorithm is embedded which hands over the control authority to an auxiliary sliding-mode controller until the danger is safely bypassed. The proposed design ensures the semi-globally uniformly ultimately bounded stability of the closed-loop signals. Simulation works demonstrating the validity of the proposed design are presented in the final

Robust Adaptive Backstepping Control of Quadrotors With Unknown Input Gains

Robust adaptive tracking control design for quadrotors with unknown parameters, including the thrust and the drag factors, is presented. Firstly, the adaptive linearizing control approach is employed for conquering the issues of unknown input gains in both the outer- and inner-loop design steps. Secondly, based on the barrier Lyapunov function (BLF) method, a robust virtual controller is constructed in the intermediate design step for counteracting the coupling nonlinearity and speeding up the convergence at the same time. Thirdly, the dynamic surface control (DSC) technique is applied for alleviating the measurement of acceleration signals and explosion of complexity problem simultaneously. Last, the serial-parallel identification model (SPIM) based composite update algorithms are incorporated for further improving the tracking performance. In particular, the prediction errors are ensured to converge to the vicinity of zero without relying on the parameter convergence. Simulation studies demonstrating its validity are carried out in the final

Robust Composite Adaptive Control of Linearisable Systems With Improved Performance

Robust composite adaptive control designs for linearisable systems with known/unknown input gain functions are presented. They mainly consist of a standard adaptive linearizing controller and an immersion and invariance (I&I) based composite update algorithm, with the inclusion of a Lyapunov-based canceling term and a $\sigma$ -modification term for ensuring the practical stability and preventing the parameter-drift phenomenon at the same time. Next, the adding an integrator and the dynamic surface control (DSC) techniques are incorporated for preventing the algebraic-loop problem in the latter case. In particular, the proposed designs ensure the convergence of prediction errors to an order of the exogenous disturbance without relying on persistent excitation (PE), which in turn improves the tracking performance significantly

Lightning-induced high temperature and pressure microstructures in surface and subsurface fulgurites

Cloud-to-ground lightning causes both high-temperature and high-pressure metamorphism of rocks, forming rock fulgurite. We demonstrate that a range of microstructural features indicative of high temperatures and pressures can form in fulgurites at the surface and in fractures up to several meters below the surface. In comparison to a granite reference sample collected from a borehole at a depth of 138 m, microstructures in both the surface and fracture fulgurite are characterized by: (i) the presence of glass, (ii) a phase transformation in K-feldspar with the presence of exsolution lamellae of plagioclase, and (iii) high residual stresses up to 1.5 GPa. Since this is the first time that fracturerelated fulgurite has been described, we also carried out a 1-D numerical model to investigate the processes by which these can form. The model shows that the electric current density in fractures up to 40 m from the landing point can be as high as that on the surface, providing an explanation for the occurrence of fracture-related fulgurites. Our work broadens the near-surface environments in which rock fulgurite has been reported, and provides a detailed description of microstructures that can be compared to those formed during other types of extreme metamorphic events.The research was supported by the Taiwan ROC (Republic of China) Ministry of Science and Technology (MOST 110-2116-M-008-002-MY2) and Earthquake-Disaster & Risk Evaluation and Management Center (E-DREaM) from the Ministry of Education (MOE) to Li-Wei Kuo. Dennis Brown acknowledges funding (PGC2018-094227-B-I00) from the Spanish Ministry of Science, Innovation, and Universities, as well as a Chaired Professor stipend from the Department of Earth Sciences at National Central University. Steven Smith acknowledges funding from the Marsden Fund, administered by the Royal Society of New Zealand (project UOO1829)