Partial Observer Canonical Form Design Method for Single-output Affine Nonlinear System with Simple Validation Conditions

Haotian Xu,Jingcheng Wang 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.7

The problem concerning observer error linearization is to find a new state coordinate transformation (diffeomorphism) to transform the underlying nonlinear system into a Partial Observer Canonical Form (POCF). Since the complexity of the existing verification conditions associated with the existence of POCF, this paper develops a two-steps method for calculating POCF to simplify the verification conditions. This method also shows that POCF is equivalent to a compound diffeomorphism that consists of two coordinate transformations. One of them is a diffeomorphism which transforms the system into an observable canonical form based on maximum invariant distribution, and the other one is a diffeomorphism of transforming the observable subsystem into an observer linearization form. With the help of this method, a part of the original conditions are replaced by a group of new conditions that are easier to be verified, and another part of the original conditions are proved to be redundant and could not be verified anymore. At last, three examples are used to demonstrate the validity of this paper.

Twin Deterministic Policy Gradient Adaptive Dynamic Programming for Optimal Control of Affine Nonlinear Discrete-time Systems

Jiahui Xu,Jingcheng Wang,Jun Rao,Yanjiu Zhong,Shangwei Zhao 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.9

Recent achievements in the field of adaptive dynamic programming (ADP), as well as the data resources and computational capabilities in modern control systems, have led to a growing interest in learning and data-driven control technologies. This paper proposes a twin deterministic policy gradient adaptive dynamic programming (TDPGADP) algorithm to solve the optimal control problem for a discrete-time affine nonlinear system in a modelfree scenario. To solve the overestimation problem resulted from function approximation errors, the minimum value between the double Q network is taken to update the control policy. The convergence of the proposed algorithm in which the value function is served as the Lyapunov function is verified. By designing a twin actor-critic network structure, combining the target network and a specially designed adaptive experience replay mechanism, the algorithm is convenient to implement and the sample efficiency of the learning process can be improved. Two simulation examples are conducted to verify the efficacy of the proposed method.

Finite Horizon Robust Optimal Tracking Control Based on Approximate Dynamic Programming for Switched Systems with Uncertainties

Shangwei Zhao,Jingcheng Wang,Haotian Xu,Hongyuan Wang 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.4

In this paper, an approximate dynamic programming (ADP)-based approach is developed to handle the robust optimal tracking control problem for switched systems with uncertainties in the finite horizon. The switched systems with unknown matched uncertainties are formulated by virtue of system dynamics and reference trajectory, where the complicated tracking problem is converted to a stabilizing robust optimal control problem. To avoid the requirement of system dynamics knowledge, a neural network (NN)-based identifier is utilized to estimate the unknown switched systems dynamics. The actor-critic NNs are constructed to approximate the optimal control input and the corresponding performance index, where the weights are trained backward-in-time in an off-line manner. Benefiting from the Lipschitz continuous condition, the convergence of the proposed approach is proved, which illustrates the iteration approach will converge to the unique solution under a small enough sampling time interval. Finally, two numerical simulation cases are employed to verify the effectiveness of the proposed approach.

Phosphorus removal and recovery from wastewater by highly efficient struvite crystallization in an improved fluidized bed reactor

Bin Lu,Jingcheng Xu,Ming Zhang,Weihai Pang,Li Xie 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.11

Phosphorus is the crucial factor causing eutrophication in the aquatic ecology. The high phosphorus loading in water bodies may result from the direct disposal of untreated wastewater. In this study, a fluidized bed reactor (FBR) was specially developed to remove and recover phosphorus effectively and efficiently via struvite crystallization. Different physiochemical and hydraulic conditions, including hydraulic retention time (HRT), pH, and molar ratios of Mg : P, N: P and Ca :Mg, were explored to optimize the performance of this improved FBR. For the continuous operating trials, promising removal and recovery efficiencies were achieved at the phosphorus concentration of 25.0mg/L: >90% of phosphorus could be removed under the optimum condition (pH=9, HRT=12 h, Mg : P=1.25 and N : P= 7.5). Increasing the recycle flow rate and prolonging the contact time could also enhance the FBR efficiency. The crystal products obtained in FBR were analyzed in terms of composition and structure. Results indicated that almost pure struvite (>99%) was achieved at low calcium concentrations, which could be considered as a high quality fertilizer.

Unique self-assembly behavior of a triblock copolymer and fabrication of catalytically active gold nanoparticle/polymer thin films at the liquid/liquid interface

Shang, Ke,Geng, Yuanyuan,Xu, Xingtao,Wang, Changwei,Lee, Yong-Ill,Hao, Jingcheng,Liu, Hong-Guo Elsevier 2014 Materials chemistry and physics Vol.146 No.1

Fabrication of Composite Polymer Foam Films at the Liquid/Liquid Interface through Emulsion-Directed Assembly and Adsorption Processes

Geng, Yuanyuan,Liu, Mei,Tong, Kun,Xu, Jian,Lee, Yong-Ill,Hao, Jingcheng,Liu, Hong-Guo American Chemical Society 2014 Langmuir Vol.30 No.8

<P>The foam films of polystyrene-<I>b</I>-poly(acrylic acid)-<I>b</I>-polystyrene (PS-<I>b</I>-PAA-<I>b</I>-PS) doped with Cd(II) or Pb(II) species were fabricated at the planar liquid/liquid interfaces between a DMF/chloroform (v/v: 1/1) solution of the polymer and aqueous solutions containing cadmium acetate or lead acetate at ambient temperature. Optical microscopic observation shows the thin film is uniform on a larger length scale. Transmission electron microscopic (TEM) investigations reveal that the foam films are made up of microcapsules with the size of several hundreds of nanometers to micrometers. The walls of the microcapsules have a layered structure decorating with nanofibers and hollow nanospheres, where numerous inorganic fine nanoparticles are dispersed homogeneously. The film formation is a result of emulsion droplet-templated assembly and adsorption of the formed microcapsules at the planar liquid/liquid interface. Because of the miscibility of DMF with chloroform and water, DMF migrates to the aqueous phase while water migrates to the organic phase across the interface, resulting in the formation of a W/O emulsion, as revealed by optical microscopic observation, freeze fracture transmission electron microscopic (FF-TEM) observation, and dynamic laser scattering (DLS) investigation. The triblock copolymer molecules and the inorganic species adsorb and self-assemble around the emulsion drops, leading to the formation of the composite microcapsules. X-ray photoelectron spectroscopic (XPS) and FTIR spectroscopic results indicate that two kinds of Cd(II) or Pb(II) species, metal oxide or hydroxide, resulting from the hydrolysis of the metal ions and the coordinated metal ions to the carboxyl groups coexist in the formed thin films, which transform to metal sulfide completely after treating with hydrogen sulfide to get metal sulfide nanoparticle-doped polymer thin films.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2014/langd5.2014.30.issue-8/la500187d/production/images/medium/la-2014-00187d_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la500187d'>ACS Electronic Supporting Info</A></P>

Emulsion-directed liquid/liquid interfacial fabrication of lanthanide ion-doped block copolymer composite thin films

Hong, Ming,Geng, Yuanyuan,Liu, Mei,Xu, Yuan,Lee, Yong-Ill,Hao, Jingcheng,Liu, Hong-Guo Elsevier 2015 JOURNAL OF COLLOID AND INTERFACE SCIENCE - Vol.438 No.-

<P><B>Abstract</B></P> <P>An emulsion-directed assembly and adsorption approach has been used to fabricate composite films of polystyrene-b-poly(acryl acid)-b-polystyrene (PS-b-PAA-b-PS) and Eu<SUP>3+</SUP> and La<SUP>3+</SUP> ions at the planar liquid/liquid interface of the polymer DMF/chloroform (1:1, v/v) mixed solution (lower phase) and aqueous solutions of the corresponding salts (upper phase). The lower phase gradually transformed to a water-in-oil (W/O) emulsion via spontaneous emulsification due to the “ouzo effect”. Polymer molecules and the metal ions assembled around emulsion droplets that adsorbed at the planar liquid/liquid interface at last, resulting in formation of composite films. The film morphologies and structures depend on Ln<SUP>3+</SUP> ions: polymer/Eu<SUP>3+</SUP> composite films were foam films composed of microcapsules ranging in size from several hundreds of nanometers to micrometers, while polymer/La<SUP>3+</SUP> composite films were composed of hollow spheres several tens of nanometers in size. Fourier transform infrared (FTIR) spectra revealed that the coordination modes of carboxyl groups to Eu<SUP>3+</SUP> and La<SUP>3+</SUP> were bridging bidentate and ionic, respectively, in the two types of composites. These results indicate that stable microcapsules can be fabricated around droplets for polymer/Eu<SUP>3+</SUP> systems, while microcapsules of polymer/La<SUP>3+</SUP> are unstable. This leads to different film morphologies and structures. Compositions of these films were characterized using energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). In addition, foam films of polymer/Eu<SUP>3+</SUP>/2,2′-bipyridine (bpy) were fabricated using this approach, and their photoluminescence properties were investigated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Composite films of block copolymer/Ln<SUP>3+</SUP> were fabricated at liquid/liquid interfaces. </LI> <LI> Eu<SUP>3+</SUP> and La<SUP>3+</SUP> have great effects on morphologies and microstructures of the films. </LI> <LI> Polymer/Eu<SUP>3+</SUP> and polymer/Eu<SUP>3+</SUP>/bpy films exhibit good luminescent properties. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>