This paper investigates a type of systems controlled over a communication network that can only accommodate a subset of actuators at any time. The medium-access status of actuators is event driven by ...a stochastic process modeled as a Markov chain. A methodology of analysis and control synthesis is established using theories in time-delay systems and Markovian jumping systems. Specifically, in the context of asymptotic mean-square stability, a state feedback control approach is derived by transforming the vector system into a scalar representation first and then using on it a stability criterion provided for scalar linear time-delay systems. The results are given in terms of a delay-dependent scalar inequality and a simple matrix inequality based on a couple of scalar decision variables, which are easily solvable using the newly proposed quasi-convex optimization algorithm. The corresponding results for uncertain linear systems are also given. Meanwhile, a design approach in the sense of stochastic stability in probability is presented using a Lyapunov-like method, with the mode-dependent results being given in the form of a set of coupled matrix differential inequalities and a martingale probability inequality. Numerical examples have shown the usefulness of the proposed results.
This paper investigates control design for the platoon of automated vehicles whose sensors have limited sensing capability. A novel hybrid platoon model is established, in which actuator delay (e.g., ...the fueling and braking delay) and the effect of sensing range limitation are involved. Based on the new model, a framework of guaranteed-cost controller design is presented, which can robustly stabilize the platoon of vehicles with a given level of disturbance attenuation. The obtained controller is complemented by additional conditions that were established to guarantee string stability and zero steady-state spacing error, yielding a useful string-stable platoon control algorithm. The effectiveness and advantage of the presented methodology is demonstrated by both numerical simulations and experiments with laboratory-scale Arduino cars.
This paper is concerned with the problem of vehicular platoon control in vehicular ad hoc networks subject to capacity limitation and random packet dropouts. By introducing binary sequences as the ...basis of network access scheduling and modeling random packet dropouts as independent Bernoulli processes, we derive a closed-form methodology for vehicular platoon control. In particular, an interesting framework for network access scheduling and platoon control codesign is established based on a set of priority rules for network access control. The resulting platoon control and scheduling algorithm can resolve network access conflicts in vehicular ad hoc networks and guarantee string stability and zero steady-state spacing errors. The effectiveness of the method is demonstrated by numerical simulations and experiments with laboratory-scale Arduino cars.
This paper investigates sampled-data cooperative adaptive cruise control (CACC) of vehicles with sensor failures. A novel switched sampled-data CACC system model is established, in which the effect ...of sensor failure is involved. Based on the new model, a design method of state feedback controllers that can robustly stabilize the CACC system is presented via the switched system approach. The obtained controller is complemented by additional conditions that are established for guaranteeing string stability and zero steady-state velocity error, which yields a useful string stable CACC algorithm. Several quantitative relations of parameters, including the sensor complete-failure rate, the system decay rate, and sampling period, are also derived. The effectiveness and advantage of the presented methodology are demonstrated by both numerical simulations and experiments with laboratory-scale Arduino cars.
Emerging evidence shows allergic diseases, such as atopic dermatitis and asthma, are risk factors of heart failure. However, the causal relationship between allergic diseases and heart failure is not ...clear. We performed a two-sample Mendelian randomization analysis between allergic diseases and heart failure using summary statistics of genome-wide association studies from large GWAS consortia, with total sample size of 1.2 million. Independent instrumental variables for asthma and atopic dermatitis (P<1x10.sup.-5) were used as the exposure. We applied five models for the Mendelian randomization analysis. Finally, we performed the sensitivity analyses to assess the robustness of the results. We have identified 55 independent single nucleotide polymorphisms (SNPs) for asthma 54 independent SNPs for atopic dermatitis as our instrumental variables. The inverse variance-weighted (IVW) analysis showed asthma was significantly associated with increased risk of heart failure (OR.sub.IVW = 1.04, 95% CI, 1.01-1.07, P = 0.03). The Mendelian randomization analysis using the other four models also showed consistent results with the IVW analysis. Similarly, atopic dermatitis was also significantly associated with an increased risk of heart failure (OR.sub.IVW = 1.03, 95% CI, 1.01-1.06, P = 0.01), consistent with the other four models. The sensitivity analysis showed no evidence of horizontal pleiotropy or results were driven by single SNPs. Our study identified asthma and atopic dermatitis as a causal risk factor for heart failure and suggest inflammatory pathogenesis as a key factor contributing to the underlying mechanism. These findings emphasize the importance of asthma and allergy control in the prevention and management of heart failure.
This paper focuses on the H ∞ fault detection (FD) problem for spring-mass systems (SMSs) over networks with distributed state delays, random packet losses, sensor saturation as well as ...multiplicative noises via unreliable communication channels. The output measurements are affected by sensor saturation which is described by sector-nonlinearities. The multiplicative noises are described as a form of Gaussian white noises multiplied by the states. A series of stochastic variables are introduced to describe the randomly occurring distributed state delays. Random packet losses are also introduced in unreliable communications. The purpose of this paper is to design an FD filter such that: 1) The FD dynamic system is exponentially stable in the mean square. 2) The error between the fault signal and the residual signal is controlled to the minimum. 3) The optimal H ∞ filtering performance index is achieved. A sufficient condition for the FD filter design is derived in terms of the solution to a linear matrix inequality (LMI). When the LMI has a feasible solution, the explicit parameters of the desired FD filter can be obtained. Finally, a simulation experiment is illustrated to show the effectiveness and application of the designed method.
This paper investigates a fixed-time leader-following formation control method for a set of autonomous underwater vehicles (AUVs) with event-triggered acoustic communications. First, an ...event-triggering communication strategy is developed to govern the communications between leader AUV and follower AUVs. Then, using a fixed-time control theory and a Lyapunov functional method, a compensator-based command filtered formation control algorithm is proposed, with which the follower AUVs can track the leader AUV in a given fixed time. Namely, the control method can guarantee all the signals in the formation control system to be globally fixed-time stabilized. With the presented fixed-time control scheme, the predesignated AUVs formation can be achieved within a fixed settling time under arbitrary initial system states, which is otherwise impossible under any existing methods including finite-time control. Furthermore, the compensator-based command filtered control technique makes the designed formation control law simple and easy to implement in practice. Simulation results demonstrate the effectiveness of the method.
This paper discusses the innovation and teaching evaluation of oral expression courses in the context of new media. Through literature review and empirical research, we found that oral expression ...teaching in the context of new media needs to combine the application of new media technologies to broaden teaching content and methods in order to improve students’ oral expression and practical application abilities. At the same time, the evaluation of oral expression courses should consider students’ performance in various aspects and practical application abilities. Future development of oral expression teaching in the context of new media requires a focus on cultivating students’ application and innovation abilities, combining virtual reality, artificial intelligence and other technologies for innovation. This paper also provides examples of some universities’ practices in oral expression course innovation, which provide some inspiration and ideas for oral expression teaching. We believe that with joint efforts from all parties, oral expression teaching in the context of new media will make better progress and development.
In rodents, the naïve early epiblast undergoes profound morphogenetic, transcriptional and epigenetic changes after implantation. These differences are maintained between blastocyst-derived embryonic ...stem (ES) cells and egg cylinder-derived epiblast stem cells (EpiSCs). Notably, ES cells robustly colonise chimaeras, whereas EpiSCs show little or no contribution. ES cells self-renew independently of mitogenic growth factors, whereas EpiSCs require fibroblast growth factor. However, EpiSCs retain the core pluripotency factors Oct4 and Sox2 and the developmental barrier dividing them from unrestricted pluripotency can be surmounted by a single reprogramming factor. This provides an opportunity to identify molecules that can reset the naïve state. We undertook a forward genetic screen for effectors of EpiSC reprogramming, employing piggyBac transposition to activate endogenous gene expression at random and selecting for undifferentiated colonies in the absence of growth factor signalling. Three recovered clones harboured integrations that activate the closely related orphan nuclear receptor genes Nr5a1 and Nr5a2. Activity of Nr5a1 and Nr5a2 was confirmed by direct transfection. Reprogrammed colonies were obtained without transgene integration and at 10-fold higher frequency than with other single factors. Converted cells exhibited the diagnostic self-renewal characteristics, gene expression profile and X chromosome activation signature of ground state pluripotency. They efficiently produced adult chimaeras and gave germline transmission. Nr5a receptors regulate Oct4 transcription but this is insufficient for reprogramming. Intriguingly, unlike previously identified reprogramming molecules, Nr5a receptors play no evident role in ES cell self-renewal. This implies a different foundation for their capacity to reset pluripotency and suggests that further factors remain to be identified.
This paper is concerned with the problem of vertical attitude estimation of a two-degree-of-freedom quarter-car suspension system by designing a distributed filtering network, where several ...distributed filters estimate vehicle heave motion cooperatively under consideration of external disturbance, network channel noises, and measurement error. The sampled data are transmitted through wireless networks. In order to reduce network traffic load and save communication resources, a novel periodic event-triggered sampling scheme is proposed, under which data are transmitted only when the proposed triggering condition is violated. Codesign of event-triggered and distributed filters is derived to guarantee well H ∞ robustness to the system noises considered above. Finally, the experiments are given to show the effectiveness of the proposed filtering system.
PDF
