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In this paper, the dynamics of an electrohydraulic servo system is analyzed. It is difficult to achieve the precise force tracking control due to its high nonlinearities and parameter uncertainties. For the accurate force tracking control, a sliding mode control algorithm with radial basis function (RBF) neural network compensation was proposed. The theory verifies that the algorithm is globally asymptotically stable. The experimental results show that the proposed algorithm is not only effective and better than the PID control in the force tracking control, but also robust to external uncertain disturbances. [ABSTRACT FROM AUTHOR]

This paper presents a power assist lower extremity exoskeleton and a fuzzy sliding mode compensation controller. First, the mechanical design of this exoskeleton and the control configuration are introduced. Second, the dynamics of lower extremity exoskeleton is analyzed and the sliding mode controller with fuzzy compensation algorithm under uncertainties for exoskeleton joints is proposed. The theoretical proof shows that it is globally stable in the sense of Lyapunov. The experiments indicate that the proposed control scheme is effective; not only it ensures the control accuracy but also is robust to external uncertainties compared with PID control. [ABSTRACT FROM AUTHOR]

This paper presents a hydraulic actuator and tendon drive system that was specifically designed for a lower-limb exoskeleton to provide high power and low inertia. The dynamics of the actuator-tendon system were analyzed based on the exoskeleton system and an adaptive sliding-mode trajectory tracking controller was designed for the drive system. The stability proof indicates that the controller is globally stable. The experimental results demonstrated that the controller provides high tracking accuracy and is robust to external disturbances and unmodeled nonlinearities. Moreover, the controller has less errors than the conventional PID controller. Further tests that included the joints of the exoskeleton were conducted to verify the performance of the controller. [ABSTRACT FROM AUTHOR]

In view of the electro-hydraulic position servo system with parameter uncertainty and bounded disturbances, an improved adaptive sliding mode control scheme is proposed. The mathematical model of the valve-controlled system is first constructed with consideration of the external disturbance, matched and mismatched unknown parameters. Then, the parametric adaptive estimation laws are established by Lyapunov technique to estimate the generalized uncertainty parameters, and the discontinuous projection algorithm is used to ensure the boundedness of parameter estimation. In order to eliminate the chattering phenomenon in sliding mode control, the saturation function is designed to replace the sign function and the gain coefficient is adjustable on the sliding surface. Finally, the comparative experimental results clarify that the proposed control scheme has better control performance than the PID controller and the SMC controller. [ABSTRACT FROM AUTHOR]

Two major defects of the exoskeleton's single-axis knee joint were exposed in human-machine coordination experiments, which are chattering of hip and knee joints and pull-feeling at ankle joint. In order to analyze and solve these issues, human gait experiments were conducted to obtain the human gait data, and a kinematic model of the exoskeleton was established. Kinematics analysis of the exoskeleton based on the human's hip and knee joint angles indicated the obvious human-machine ankle joint movement error; inverse kinematics analysis of the exoskeleton according to the human ankle joint trajectory reflected the abrupt angle changes of exoskeleton's hip and knee joints. According to these analysis results, kinematics differences between the exoskeleton's single-axis knee joint and human's trochlea knee joint were regarded as the primary cause of the defects observed in human-machine coordination experiments. The exoskeleton's knee joint was optimized in four-bar linkage type to imitate the kinematics characteristics of human's knee joint. Kinematics simulation results of the optimized exoskeleton showed that human-machine ankle joint movement error and abrupt angle changes of the exoskeleton's hip and knee joints have been both significantly reduced, thus the effectiveness of the exoskeleton's knee joint optimization for improving the human-machine coordination could be confirmed. [ABSTRACT FROM AUTHOR]

Hepatic fibrosis is defined as a pathological process, and activation of hepatic stellate cells (HSCs) is believed to be the key event of liver fibrosis. Additionally, activated HSCs may participate in the formation of the tumor microenvironment. Polaprezinc, a protector of the gastric mucosa, has been recently demonstrated to be an inhibitor of liver fibrosis in a mouse model. Proliferation and colony formation assays were performed to determine the inhibitory effects of polaprezinc on the growth of LX‑2 and hepG2 cells. A migration assay was used to evaluate the change in mobility of LX‑2 cells and quantitative polymerase chain reaction was performed to detect the expression levels of key markers of fibrosis. Finally, a gene chip assay for polaprezinc‑treated hepG2 cells was performed to evaluate the effect of polaprezinc on the hepG2 gene expression profile. The proliferation assay indicated that polaprezinc may inhibit the LX‑2 cell proliferation and the migration assays confirmed the inhibition of mobility. The expression levels of fibrotic markers such as collagen I, fibronectin and α‑smooth muscle actin were downregulated following polaprezinc treatment. The proliferation activity of polaprezinc‑treated hepG2 cells was reduced and the gene chip assay indicated that series of gene expression changes associated with cancer migration, cell skeletal organization and proliferation had occurred. In conclusion, polaprezinc treatment mayinhibit the proliferation of hepatocellular carcinoma cells and reverse liver fibrosis by deactivating HSCs. The present findings suggest that polaprezinc provides a novel treatment for patients with gastritis complicated with cirrhosis. [ABSTRACT FROM AUTHOR]

The article reports on a study outlining a metal gate integration scheme for attaining an accurate threshold voltage (VT) control. It mentions the challenges of maintaining electrical conductivity and its demand for high performance complementary metal oxide semiconductors (CMOS). An overview of its essential role in ultra-large-scale integration (ULSI) fabrication towards optimal performance and consumption of energy is also presented.