Interconnected Observers for Robust Decentralized Estimation with Performance Guarantees and Optimized Connectivity Graph

Motivated by the need of observers that are both robust to disturbances and guarantee fast convergence to zero of the estimation error, we propose an observer for linear time-invariant systems with noisy output that consists of the combination of N coupled observers over a connectivity graph. At each node of the graph, the output of these interconnected observers is defined as the average of the estimates obtained using local information. The convergence rate and the robustness to measurement noise of the proposed observer's output are characterized in terms of $\mathcal{KL}$ bounds. Several optimization problems are formulated to design the proposed observer so as to satisfy a given rate of convergence specification while minimizing the $H_\infty$ gain from noise to estimates or the size of the connectivity graph. It is shown that that the interconnected observers relax the well-known tradeoff between rate of convergence and noise amplification, which is a property attributed to the proposed innovation term that, over the graph, couples the estimates between the individual observers. Sufficient conditions involving information of the plant only, assuring that the estimate obtained at each node of the graph outperforms the one obtained with a single, standard Luenberger observer are given. The results are illustrated in several examples throughout the paper.Comment: The technical report accompanying "Interconnected Observers for Robust Decentralized Estimation with Performance Guarantees and Optimized Connectivity Graph" to be published in IEEE Transactions on Control of Network Systems, 201

A new secondary instability phenomenon of parametric sloshing

This paper reports on a new secondary instability phenomenon of parametric sloshing. Faraday first experimentally discovered the (1/2 sub-harmonic) parametric sloshing phenomenon in 1831. The parametric instability starts from a small disturbance on the free fluid surface, and then the sloshing amplitude of fluid increases exponentially and finally reaches a steady-state limit cycle oscillation. This parametric instability is called the first (linear) instability. The parametric sloshing experiment of this study discovers that in the case of the parametric excitation unchanged, the free fluid surface that is in a limit cycle oscillation might undergo a secondary instability. Under this circumstance, the sloshing amplitude of free surface increases sharply. The consequence is catastrophic – the fluid is splashed out of the tank. During the secondary instability, the sloshing mode (or energy) is transferred from the third mode to the first mode. The secondary instability, which is different from the first instability, is a nonlinear unstable process. The mechanism of the secondary instability is needed a further study

Recent progress on molecular breeding of rice in China

Molecular breeding of rice for high yield, superior grain quality, and strong environmental adaptability is crucial for feeding the world’s rapidly growing population. The increasingly cloned quantitative trait loci and genes, genome variations, and haplotype blocks related to agronomically important traits in rice have provided a solid foundation for direct selection and molecular breeding, and a number of genes have been successfully introgressed into mega varieties of rice. Here we summarize China’s great achievements in molecular breeding of rice in the following five traits: high yield, biotic stress resistance, abiotic stress resistance, quality and physiology. Further, the prospect of rice breeding by molecular design is discussed

Observers with performance guarantees and robustness to measurement noise for linear systems

This dissertation focuses on a class of observer designs for linear-time invariant (LTI) systems, where the state variables are typically not directly measurable or may be too expensive to completely measure. Designing an observer with both fast convergence rate and robustness to noise is a well-know challenge, yet it is an essential task in many applications. To relax the generic tradeoff between fast convergence rate and robustness to perturbations in observer design with static gains, three main scenarios are considered in this thesis. With the assumption that information is accessible continuously (discretely), the first case focuses on interconnected observers over a network. It is shown to have significant advantages when comparing to a Luenberger observer. The second scenario is when the rate of convergence is prioritized. A robust observer that exhibits both continuous and impulsive behaviors is developed. With proper choice of parameters, such an observer generates estimates that converge to the state of LTI in finite-time and is robust to small perturbations. The third scenario is when measurements and information over networks are only accessible intermittently. A hybrid distributed state observer framework is established to achieve global exponential stability of the zero estimation error set. Its robustness with respect to measurement, communication noise and unmodeled dynamics is characterized in terms of input-to-state stability (ISS). In addition to providing sufficient conditions to guarantee stability and robustness of these observers, the problem of determining parameters are characterized by Linear Matrix Inequalities (LMIs) in this thesis. Constructive LMIs based on Lyapunov methods are given to efficiently design these observers. Advantages and unique properties of these observers are illustrated in many examples throughout the thesis

The Bit Selection Research on LS101

The well LS101 has a deep subject reservoir. The ROP is low and drill bits are changed frequently because of high formation hardness and high rock abrasiveness. Rock breaking mechanism of PDC bit and cone bit is analyzed in this paper. The main factors which affect rock breaking efficiency of bits are provided. LS101 deep formation data provided by REED Hycalog and well logging information are analyzed and Lithological features of LS101 deep formation are gained. Referred to the realistic behavior of each drill bit in this well, the results of bits selection on LS block are recommended, and have the model significance for the future drilling in the same formation of this block

Notions, Stability, Existence, and Robustness of Limit Cycles in Hybrid Systems

This paper deals with existence and robust stability of hybrid limit cycles for a class of hybrid systems given by the combination of continuous dynamics on a flow set and discrete dynamics on a jump set. For this purpose, the notion of Zhukovskii stability, typically stated for continuous-time systems, is extended to the hybrid systems. Necessary conditions, particularly, a condition using a forward invariance notion, for existence of hybrid limit cycles are first presented. In addition, a sufficient condition, related to Zhukovskii stability, for the existence of (or lack of) hybrid limit cycles is established. Furthermore, under mild assumptions, we show that asymptotic stability of such hybrid limit cycles is not only equivalent to asymptotic stability of a fixed point of the associated Poincar\'{e} map but also robust to perturbations. Specifically, robustness to generic perturbations, which capture state noise and unmodeled dynamics, and to inflations of the flow and jump sets are established in terms of $\mathcal{KL}$ bounds. Furthermore, results establishing relationships between the properties of a computed Poincar\'{e} map, which is necessarily affected by computational error, and the actual asymptotic stability properties of a hybrid limit cycle are proposed. In particular, it is shown that asymptotic stability of the exact Poincar\'{e} map is preserved when computed with enough precision. Several examples, including a congestion control system and spiking neurons, are presented to illustrate the notions and results throughout the paper.Comment: 26 pages. Version submitted for revie

How and Why Digital Generation Teachers Use Technology in the Classroom: An Explanatory Sequential Mixed Methods Study

While teachers’ conservative attitude toward technology has been identified as a barrier to effective technology integration in classrooms, it is often optimistically assumed that this issue will resolve when the digital generation enters the teaching profession (Morris, 2012). Using a mixed methodology approach, this study aimed to examine the current technology usage of digital generation student teachers and the impact of possible internal and external barriers (such as self-efficacy, risk taking, and technology access and support) on their use of technology. Seventy-one student teachers first responded to an online survey regarding their technology use in classrooms. Afterwards, six participants were purposefully selected, based on their survey responses, to participate in follow-up interviews about their attitudes toward technology and challenges of integrating technology to teaching. Findings of the study suggested that digital generation student teachers’ use of technology in the classroom was significantly correlated with their self-efficacy, perceived computer skills, and technology access and support. However, the participants’ perceived level of risk taking was not related to their use of technology in the classroom. Findings of the study suggest that digital native student teachers have not necessarily become more comfortable keeping pace with the fast rate of change in technology. Implications of findings are discussed