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| 1 | Finite-Time Neural Funnel Control for Motor Servo Systems with Unknown Input Constraint显示文摘In this paper, a finite-time neural funnel control(FTNFC) scheme is proposed for motor servo systems with unknown input constraint. To deal with the non-smooth input saturation constraint problem, a smooth non-affine function of the control input signal is employed to approximate the saturation constraint, which is further transformed into an affine form according to the mean-value theorem. A fast terminal sliding mode manifold is constructed by using a novel funnel error variable to force the tracking error falling into a prescribe boundary within a finite time. Then, a simple sigmoid neural network is utilized to approximate the unknown system nonlinearity including the saturation.Different from the prescribed performance control(PPC), the proposed finite-time neural funnel control avoids using the inverse transformed function in the controller design, and could guarantee the prescribed tracking performance without knowing the saturation bounds in prior. The effectiveness and superior performance of the proposed method are verified by comparative simulation results. | CHEN Qiang TANG Xiaoqing NAN Yurong REN Xuemei | 2017 | Journal of Systems Science & Complexity2017，30，3： | 9 |
| 2 | FINITE-TIME TRACKING CONTROL FOR MOTOR SERVO SYSTEMS WITH UNKNOWN DEAD-ZONES显示文摘A finite-time tracking control scheme is proposed in this paper based on the terminal sliding mode principle for motor servo systems with unknown nonlinear dead-zone inputs.By using the differential mean value theorem,the dead-zone is represented as a time-varying system and thus the inverse compensation approach is avoided.Then,an indirect terminal sliding mode control(ITSMC)is developed to guarantee the finite-time convergence of the tracking error and to overcome the singularity problem in the traditional terminal sliding mode control.In the proposed controller design,the unknown nonlinearity of the system is approximated by a simple sigmoid neural network,and the approximation error is diminished by employing a robust term.Comparative experiments on a turntable servo system are conducted to show the superior performance of the proposed method. | CHEN Qiang YU Li NAN Yurong | 2013 | Journal of Systems Science & Complexity2013，26，6： | 9 |
| 3 | Full-Order Sliding Mode Control for High-Order Nonlinear System Based on Extended State Observer显示文摘In this paper, a full-order sliding mode control based on extended state observer(FSMC+ESO) is proposed for high-order nonlinear system with unknown system states and uncertainties.The extended state observer(ESO) is employed to estimate both the unknown system states and uncertainties so that the restriction that the system states should be completely measurable is relaxed,and a full-order sliding mode controller is designed based on the ESO estimation to overcome the chattering problem existing in ordinary reduced-order sliding mode control. Simulation results show that the proposed method facilitates the practical application with respect to good tracking performance and chattering elimination. | CHEN Qiang TAO Liang NAN Yurong | 2016 | Journal of Systems Science & Complexity2016，29，4： | 7 |
| 4 | Dynamic Study on Water Stability of Soil Structure and Soil Characteristics of Several Types of Soils in Southwest China显示文摘Three suborder soils in southwest China were adopted,namely Ustic Vertisol,Stagnic Anthrosol and Ustic Ferrosol, so as to carry out the basic physical and chemical analysis respectively, to design a dynamic measuring method for water stability of soil structure and conduct the comparative study on the quality of the soil structure. The results indicated that ① The water stability dynamic characteristic of the soil structure could well reflect the maintaining capability of the soil structure as time goes on. ② The quality of several soil structures in southwest China was sequenced as follows:Stagnic Anthrosols ∨Ustic Vertisols ∨Ustic Ferrosols. ③ The water stability of soil structure is very positively correlated with the capillary porosity and the clay particle (D ∧0.002 mm) content (Cc), but is very negatively correlated with the silt (D is 0.05-0.002 mm) content (Csc), and ④ The dynamic functional equation of the water stability of soil structure in southwest China was established, so that the water stability characteristics of various soil structures could be quantitatively expressed and the quality of different soil structures can be quantitatively compared from each other. | SHEN Nan HE Yurong XU Xiangming | 2008 | Wuhan University Journal of Natural Sciences2008，13，3： | 2 |
| 5 | Soil Crevice Formation and Erosion in Yuanmou Dry-Hot Valley, Yunnan Province, China显示文摘The basic characteristics, X-ray analysis and micro-morphology of soil developed from the parent rubified soil is probed. Results show that there are similarities among different types of the rubified soils. The soil clay (D<0.002 mm) contents (Cc) are relatively higher between 29.16% and 80.03%. In addition, organic matter contents are lower between 2.2-6.6 g/kg. The clay minerals in the rubified soils have a high content of 2:1 type swelling minerals, e.g., smectite and vermiculite, which are the basic causes of formation of soil cracks and crevices. Soil micro-morphology characteristics show that microcosmic crevices uni-versally distributed within the tight and compact soil microstruc-ture are the microcosmic characteristics of crevices formation. The soil cracks and crevices change the erosion process. Obviously, well developed soil crevice carries a significant connection with strong soil erosion in Yuanmou, Yunnan province, China. The term 'soil crevice erosion' was coincided with the viewpoint put for-ward that soil crevice erosion plays a dominant role in regional and violent soil erosion in this area. | XU Xiangming HE Yurong SHEN Nan WANG Yanqiang | 2009 | Wuhan University Journal of Natural Sciences2009，14，1： | 0 |
| 6 | High-performance non-Fermi-liquid metallic thermoelectric materials显示文摘Searching for high-performance thermoelectric(TE)materials in the paradigm of narrow-bandgap semiconductors is hampered by a bottleneck.Here we report on the discovery of metallic compounds,TiFe_(x)Cu_(2x−1)Sb and TiFe1.33Sb,showing the thermopower exceeding many TE semiconductors and the dimensionless figure of merits zTs comparable with the state-of-the-art TE materials.A quasi-linear temperature(T)dependent electrical resistivity in 2–700 K and the logarithmic T-dependent electronic specific heat at low temperature coexist with the high thermopower,highlighting the strong intercoupling of the non-Fermi-liquid(NFL)quantum critical behavior of electrons with TE transports.Electronic structure analysis reveals a competition between the antiferromagnetic(AFM)ordering and Kondo-like spin compensation as well as a parallel two-channel Kondo effect.The T-dependent magnetic susceptibility agrees with the quantum critical scenario of strong local correlation.Our work demonstrates the correlation among high TE performance,NFL quantum criticality,and magnetic fluctuation,which opens up directions for future research. | Zirui Dong Yubo Zhang Jun Luo Ying Jiang Zhiyang Yu Nan Zhao Liusuo Wu Yurong Ruan Fang Zhang Kai Guo Jiye Zhang Wenqing Zhang | 2023 | npj Computational Materials2023，，1： | 0 |
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