Adaptive Finite-Time Model Estimation and Control for Manipulator Visual Servoing using Sliding Mode Control and Neural Networks

The image-based visual servoing without models of system is challenging since it is hard to fetch an accurate estimation of hand-eye relationship via merely visual measurement. Whereas, the accuracy of estimated hand-eye relationship expressed in local linear format with Jacobian matrix is important to whole system's performance. In this article, we proposed a finite-time controller as well as a Jacobian matrix estimator in a combination of online and offline way. The local linear formulation is formulated first. Then, we use a combination of online and offline method to boost the estimation of the highly coupled and nonlinear hand-eye relationship with data collected via depth camera. A neural network (NN) is pre-trained to give a relative reasonable initial estimation of Jacobian matrix. Then, an online updating method is carried out to modify the offline trained NN for a more accurate estimation. Moreover, sliding mode control algorithm is introduced to realize a finite-time controller. Compared with previous methods, our algorithm possesses better convergence speed. The proposed estimator possesses excellent performance in the accuracy of initial estimation and powerful tracking capabilities for time-varying estimation for Jacobian matrix compared with other data-driven estimators. The proposed scheme acquires the combination of neural network and finite-time control effect which drives a faster convergence speed compared with the exponentially converge ones. Another main feature of our algorithm is that the state signals in system is proved to be semi-global practical finite-time stable. Several experiments are carried out to validate proposed algorithm's performance.Comment: 24 pages, 10 figure

A Novel Uncalibrated Visual Servoing Controller Baesd on Model-Free Adaptive Control Method with Neural Network

Nowadays, with the continuous expansion of application scenarios of robotic arms, there are more and more scenarios where nonspecialist come into contact with robotic arms. However, in terms of robotic arm visual servoing, traditional Position-based Visual Servoing (PBVS) requires a lot of calibration work, which is challenging for the nonspecialist to cope with. To cope with this situation, Uncalibrated Image-Based Visual Servoing (UIBVS) frees people from tedious calibration work. This work applied a model-free adaptive control (MFAC) method which means that the parameters of controller are updated in real time, bringing better ability of suppression changes of system and environment. An artificial intelligent neural network is applied in designs of controller and estimator for hand-eye relationship. The neural network is updated with the knowledge of the system input and output information in MFAC method. Inspired by "predictive model" and "receding-horizon" in Model Predictive Control (MPC) method and introducing similar structures into our algorithm, we realizes the uncalibrated visual servoing for both stationary targets and moving trajectories. Simulated experiments with a robotic manipulator will be carried out to validate the proposed algorithm.Comment: 16 pages, 8 figure

Development Of Structural-functional Integrated Energy Storage Concrete With Innovative Macro-encapsulated PCM By Hollow Steel Ball

Phase change materials (PCMs) have great potential for applications in energy efficient buildings. In this study, an innovative method of macro-encapsulation of PCM using hollow steel balls (HSB) was developed and the thermal and mechanical performance of PCM-HSB concrete was examined. The macro-encapsulation system (PCM-HSB) was attached with a metal clamp (c) for better mechanical interlocking with the mortar matrix. The latent heat of PCM-HSB-c that can be acquired is approximately 153.1 J/g, which can be considered to rank highly among PCM composites. According to the self-designed thermal performance evaluation, the PCM–HSB-c concrete panel is capable of reducing and deferring the peak indoor temperature. The indoor temperature of the room model using PCM-HSB-c panels was significantly lower than the ones with normal concrete panels by a range of 3–6%. Furthermore, the test room using a higher PCM-HSB-c content demonstrated a greater ability to maintain a lower indoor room temperature for a longer period of time during heating cycles. In consideration of the mechanical properties, thermal performance and other aspects of cost factors, 50% and 75% PCM-HSB-c replacement levels are recommended in producing concrete

Assessment of Hypoxia Inducible Factor Levels in Cancer Cell Lines upon Hypoxic Induction Using a Novel Reporter Construct

Hypoxia Inducible Factor (HIF) signaling pathway is important for tumor cells with limited oxygen supplies, as it is shown to be involved in the process of proliferation and angiogenesis. Given its pivotal role in cancer biology, robust assays for tracking changes in HIF expression are necessary for understanding its regulation in cancer as well as developing therapies that target HIF signaling. Here we report a novel HIF reporter construct containing tandem repeats of minimum HIF binding sites upstream of eYFP coding sequence. We show that the reporter construct has an excellent signal to background ratio and the reporter activity is HIF dependent and directly correlates with HIF protein levels. By utilizing this new construct, we assayed HIF activity levels in different cancer cell lines cultured in various degrees of hypoxia. This analysis reveals a surprising cancer cell line specific variation of HIF activity in the same level of hypoxia. We further show that in two cervical cancer cell lines, ME180 and HeLa, the different HIF activity levels observed correlate with the levels of hsp90, a cofactor that protects HIF against VHL-independent degradation. This novel HIF reporter construct serves as a tool to rapidly define HIF activity levels and therefore the therapeutic capacity of potential HIF repressors in individual cancers

A nonlinear analytical model of composite plate structure with an MRE function layer considering internal magnetic and temperature fields

To better exert the vibration suppression effect of magnetorheological elastomer (MRE) embedded into a composite structure with structural and functional integration advantage, this study proposes a nonlinear analytical model of such composite plate with an MRE function (MREF) layer, accounting for internal magnetic and temperature fields for the first time. Initially, a 9-layer fiber metal laminated (FML) plate with the MREF composites, consisting of two layers of metal protective skins, two layers of fiber-reinforced polymer (FRP) and one layer of MREF, is taken as an example to describe such a modelling method. Nonlinear expressions of elastic moduli of MRE and FRP involving thermal and magnetic fitting coefficients are also proposed, followed by derivation of the energy expressions of the constituent layers by the Rayleigh-Ritz method. After the free and forced vibrations are solved, the identification procedure of fitting coefficients is described and some literature results are employed to preliminarily validate this model without consideration of internal magnetic field or temperature field or both. Finally, dynamic experiments under different magnetic and temperature conditions are undertaken. The detailed comparison of the natural frequencies and resonant responses are conducted to provide a solid validation of the model developed. It has been found that enlarging the magnetic and temperature fields both facilitate the improvement of the anti-vibration performance. Also, by further increasing the shear modulus of MRE, the volume fraction of carbonyl iron particles or the thickness ratio of the MRE layer to the overall structure, a better vibration suppression capability can be obtained

Investigations on ORC radial inflow turbine three-dimensional geometry design and off-design performance prediction

Radial inflow turbine is a critical component in the ORC system, which not only influences the system's thermodynamic performance directly but also dominates the system investment cost. Besides, the ORC system is usually operated under off-design operating conditions. Therefore, the reasonable design of the radial inflow turbine and the effective prediction of turbine off-design performance are very important for the ORC system. So based on the authors' previous studies, approaches to designing the turbine's three-dimensional geometry and to predicting the turbine's off-design performance have been discussed in this paper. At first, the parametric modeling for the turbine rotor has been established and the influence of geometric control parameters on turbine performance has been investigated, then the reasonable three-dimensional geometry design of the turbine has been determined. After that, based on the suitable turbine geometry, the off-design performance of the turbine has been investigated. Through the polynomial fitting method, new turbine performance prediction models have been constructed. And the effectiveness of these models has been validated under different organic fluid conditions. This paper presents new perspectives on ORC turbine three-dimensional geometry design and off-design performance prediction, which aims to promote its standardization

Macrophage in Sporadic Thoracic Aortic Aneurysm and Dissection: Potential Therapeutic and Preventing Target

Thoracic aortic aneurysm and dissection (TAAD) is a life-threatening cardiovascular disorder lacking effective clinical pharmacological therapies. The underlying molecular mechanisms of TAAD still remain elusive with participation of versatile cell types and components including endothelial cells (ECs), smooth muscle cells (SMCs), fibroblasts, immune cells, and the extracellular matrix (ECM). The main pathological features of TAAD include SMC dysfunction, phenotypic switching, and ECM degradation, which is closely associated with inflammation and immune cell infiltration. Among various types of immune cells, macrophages are a distinct participator in the formation and progression of TAAD. In this review, we first highlight the important role of inflammation and immune cell infiltration in TAAD. Furthermore, we discuss the role of macrophages in TAAD from the aspects of macrophage origination, classification, and functions. On the basis of experimental and clinical studies, we summarize key regulators of macrophages in TAAD. Finally, we review how targeting macrophages can reduce TAAD in murine models. A better understanding of the molecular and cellular mechanisms of TAAD may provide novel insights into preventing and treating the condition

Surface Properties and HDN Activity of Mo2N

The effects of passivation and sulfidation on the bulk structure and surface properties of Mo2N were studied by using XRD, H-2-TPD and TPS methods. The characterization results of Mo2N combined with the pyridin HDN activity show that the surface properties of Mo2N are changed significantly after passivation or sulfidation in spite of the bulk structure unchanged. The H-2-TPD profile for passivated Mo2N is obviously different from that of the fresh one and the pyridin HDN activity over passivated Mo2N is much lower as well. According to the behavior of Mo2N in different passivating conditions and H-2-TPD results, we suggest that the passivation of Mo2N produces Mo-2 on the sample surface. Based on the H-2-TPD profiles and the pyridin HDN activity over Mo2N samples which either had been sulfidized or not and the TPS profiles, we conclude that the surface structure of molybdenum nitride has been changed to sulfide under sulfiding condition

Differential responses of neuronal and spermatogenic cells to the doppel cytotoxicity.

Although structurally and biochemically similar to the cellular prion (PrP(C)), doppel (Dpl) is unique in its biological functions. There are no reports about any neurodegenerative diseases induced by Dpl. However the artificial expression of Dpl in the PrP-deficient mouse brain causes ataxia with Purkinje cell death. Abundant Dpl proteins have been found in testis and depletion of the Dpl gene (Prnd) causes male infertility. Therefore, we hypothesize different regulations of Prnd in the nerve and male productive systems. In this study, by electrophoretic mobility shift assays we have determined that two different sets of transcription factors are involved in regulation of the Prnd promoter in mouse neuronal N2a and GC-1 spermatogenic (spg) cells, i.e., upstream stimulatory factors (USF) in both cells, Brn-3 and Sp1 in GC-1 spg cells, and Sp3 in N2a cells, leading to the expression of Dpl in GC-1 spg but not in N2a cells. We have further defined that, in N2a cells, Dpl induces oxidative stress and apoptosis, which stimulate ataxia-telangiectasia mutated (ATM)-modulating bindings of transcription factors, p53 and p21, to Prnp promoter, resulting the PrP(C) elevation for counteraction of the Dpl cytotoxicity; in contrast, in GC-1 spg cells, phosphorylation of p21 and N-terminal truncated PrP may play roles in the control of Dpl-induced apoptosis, which may benefit the physiological function of Dpl in the male reproduction system