University of Macau

About: University of Macau is a education organization based out in Macao, Macau, China. It is known for research contribution in the topics: Population & Control theory. The organization has 6636 authors who have published 18324 publications receiving 327384 citations. The organization is also known as: UM & UMAC.

Anti-liquid-Interfering and Bacterially Antiadhesive Strategy for Highly Stretchable and Ultrasensitive Strain Sensors Based on Cassie-Baxter Wetting State

Abstract: As a large number of strain sensors are put into practical use, their stability should be considered, especially in harsh environments containing water or microorganisms, which could affect strain sensing. Herein, a novel strategy to overcome liquid interference is proposed. The strain sensor is constructed with a sandwich architecture through layer-by-layer (LBL) spray-coating of a 3-(aminopropyl)triethoxysilane (APTES) bonding layer and multi-walled carbon nanotubes/graphene (MWCNT/G) conductive layers on an elastomeric polydimethysiloxane (PDMS) substrate, and is further decorated with silver (Ag) nanoparticles and the (heptadecafluoro-1,1,2,2-tetradecyl) trimethoxysilane (FAS, F in short) to obtain a F/Ag/MWCNG/G-PDMS (FAMG) strain sensor. The superhydrophobicity and underwater oleophobicity of the outer cover layer causes this FAMG strain sensor surface to exhibit stable strain sensing resistant to liquid interference upon stretching in the Cassie−Baxter wetting state, and resistance to bacterial adhesion (Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli)). The sensor attains ultrasensitivity (with a maximum gauge factor of 1989 in the condition of liquid interference), broad strain range (0.1–170%), fast response time (150 ms), and stable response after 1000 stretching–releasing cycles. The ultrasensitivity is provided by propagation of cracks in MWCNT/G conductive layers and terminal fracture of the intermediate separating layers (APTES/MWCNT/G). The microbridge effect of MWCNTs and slippage of APTES/MWCNT/G provide a large strain range. The FAMG strain sensor is successfully used to monitor a series of human activities and an electronic bird under artificial rain and bacterial droplets, indicating the potential use of this sensor in complex environments.

Adaptive least squares support vector machines filter for hand tremor canceling in microsurgery

Abstract: One of the main problems for effective control of a minimally invasive surgery (MIS) is the imprecision that caused by hand tremor. In this paper, a novel adaptive filter, the least squares support vector machines adaptive filter (LS-SVMAF), is proposed to overcome this problem. Compared with traditional methods like multi layer perceptron (MLP), LS-SVM shows a superior performance of nonlinear modeling with small scale of data set or high dimensional input space. With the LS-SVMAF, we can model and predict the hand tremor more effectively and improve the precision and reliability in the master–slave robotic system for microsurgery. Simulation results demonstrate the effectiveness of the proposed filter and its superior performance over its competing rivals.

Adaptive Fuzzy Control for a Class of Stochastic Pure-Feedback Nonlinear Systems With Unknown Hysteresis

Abstract: This paper addresses the problem of adaptive fuzzy control for a class of stochastic pure-feedback nonlinear systems with unknown direction hysteresis. Compared with the existing researches on hysteresis problem, the stochastic disturbances and the unknown hysteresis are simultaneously considered in the pure-feedback systems. In addition, the hysteresis parameters as well as the direction of hysteresis are unknown. By introducing an auxiliary virtual controller and employing the new properties of Nussbaum function, the major technique difficulty arising from the unknown direction hysteresis is overcome. Based on the fuzzy logic system's online approximation capability, a novel adaptive fuzzy control scheme is presented via the backstepping technique. It is shown that the proposed control scheme guarantees that all the signals of the closed-loop system are semiglobally uniformly bounded in probability, and the tracking error converges to a neighborhood of the origin in the sense of mean quantic value. Finally, simulation results further demonstrate the effectiveness of the proposed control scheme.