This paper deals with the adaptive sliding-mode control problem for nonlinear active suspension systems via the Takagi-Sugeno (T-S) fuzzy approach. The varying sprung and unsprung masses, the unknown ...actuator nonlinearity, and the suspension performances are taken into account simultaneously, and the corresponding mathematical model is established. The T-S fuzzy system is used to describe the original nonlinear system for the control-design aim via the sector nonlinearity approach. A sufficient condition is proposed for the asymptotical stability of the designing sliding motion. An adaptive sliding-mode controller is designed to guarantee the reachability of the specified switching surface. The condition can be converted to the convex optimization problems. Simulation results for a half-vehicle active suspension model are provided to demonstrate the effectiveness of the proposed control schemes.
This paper presents the problem of finite-time stabilization for vehicle suspension systems with hard constraints based on terminal sliding-mode (TSM) control. As we know, one of the strong points of ...TSM control is its finite-time convergence to a given equilibrium of the system under consideration, which may be useful in specific applications. However, two main problems hindering the application of the TSM control are the singularity and chattering in TSM control systems. This paper proposes a novel second-order sliding-mode algorithm to soften the switching control law. The effect of the equivalent low-pass filter can be properly controlled in the algorithm based on requirements. Meantime, since the derivatives of term with fractional power do not appear in the control law, the control singularity is avoided. Thus, a chattering-free TSM control scheme for suspension systems is proposed, which allows both the chattering and singularity problems to be resolved. Finally, the effectiveness of the proposed approach is illustrated by both theoretical analysis and comparative experiment results.
In this paper, the event-triggered robust filtering problem is investigated for a class of network-based state-dependent uncertain systems in the sense of finite-time boundedness, considering network ...transmission delay. By resorting to a generalized performance index, the H ∞ and L 2 - L ∞ filtering problems can be solved in a unified framework. An event-triggered scheme is also utilized to sift out the sampled signals so that both the communication resources and the network bandwidth can be saved as much as possible. By means of an appropriate Lyapunov-Krasovskii functional and the delay system approach, sufficient conditions guaranteeing the filtering error system being finite-time bounded with extended dissipativity are deduced. Based on the convex optimization, an explicit expression of the desired finite-time robust filter is derived. Finally, two numerical examples are provided to illustrate the effectiveness of the developed methods.
This paper investigates the problem of H ∞ filtering for polynomial-fuzzy-model-based discrete-time networked systems under an event-triggered scheme. A polynomial fuzzy filter is designed to ...estimate the control output. In order to reduce the data size transmitted in a network, signal quantization is managed via a logarithmic quantizer. A novel method is designed to guarantee a filtering error system to be asymptotically stable and to satisfy the desired performance. Furthermore, sufficient conditions developed via the method are represented as a sum of squares, which can be solved by SOSTOOLS. A simulation example is provided to demonstrate the effectiveness of the proposed results.
•Reduced terrestrial deposition in the Sunda Shelf since the last glaciation.•Remarkable mangrove peaks during meltwater pulse (MWP) events in Sunda Shelf.•Increased mangrove deposition and pCO2 ...during the strong MWP events 1A and 1B.
Mangroves have received increasing attention in recent years for their high carbon storage capacity. The effects of sea-level change during the last glacial period on terrestrial deposition and coastal mangrove ecosystems were investigated using various organic lipid proxies in marine sediment cores from the Sunda Shelf in the southern South China Sea (SCS). The gradual reduction in the content of long-chain n-alkanes and n-alkanols, BIT index, and increasing δ13Corg trend from the last glacial to the Holocene indicated that the depocenter moved landward from the studied location during the deglacial sea-level rise. Remarkable peaks in the mangrove proxy (Taraxerol/n-C28 alcohol ratio) occurred during meltwater pulse (MWP) events in the Sunda Shelf area, associated with the drowning and destruction of mangroves that could not withstand the rapid sea-level rise. The decomposition of carbon-rich mangrove deposits may have contributed to atmospheric CO2 concentration during two strong MWP events in Sunda Shelf. Our results suggest the vulnerability of mangrove systems upon rapid sea level change with positive feedback for global warming.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Observations have shown that seeds collected by harvester ants are less likely to mold. Based on evolutionary analysis and other research, it was hypothesized that harvester ants could apply ...actinomycetes to protect seeds, similar to the protection of mutualistic fungi by leafcutter ants. Two actinomycetes were successfully isolated from the harvester ant Messor orientalis. The taxonomic status of the actinomycetes was determined by 16S rRNA sequence analysis and biochemical experimental observations. Their inhibitory effects on plant pathogens were measured. One of the bacteria was identified as Brachybacterium phenoliresistens and denoted as B. phenoliresistens MO. The other belonged to the genus Microbacterium. It was named Microbacterium sp. Growth rate determination and coculture experiments were performed to explore the inhibitory effect of actinomycetes on indicator plant pathogens. The inhibition rates of the actinomycetes toward Peronophythora litchii and Rhizoctonia solani were 100% in media containing 30% or more fermentation broth, and they also showed an inhibitory effect on Colletotrichum siamense. The coculture experiment supported this result by showing that the growth of P. litchii and R. solani was inhibited in the presence of actinomycetes. Therefore, the results of this study show the agricultural application potential of these bacteria and may provide a reference for research on the symbiosis of harvester ants with actinomycetes.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This paper introduces a co-design approach for fault detection and time-varying formation control for a series of nonlinear leader-following multi-agent systems under stochastic switching directed ...topology. The random environmental fluctuations are described by a Markov chain. Utilizing relative output information, fault detection observers are developed not only to estimate system states but also to construct a robust residual signal, capable of detecting multiple faulty agents simultaneously in the presence of external perturbations. The paper provides sufficient conditions to guarantee the uniform ultimate boundedness in probability of the formation error and the H∞ performance for fault detection. Precise identification of potential faulty agents is achieved by evaluating the residual signal and logical reasoning. The effectiveness of formation control and the efficiency of the proposed joint design approach are demonstrated by a set of tailless fighter airplanes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper concentrates on the estimation of system states and the reconstruction of disturbances in a class of nonlinear systems considering stateless situation. The disturbances are coupled with ...time-varying parameters. The sliding mode observer approach is utilized to solve these two issues. Firstly, a descriptor model is presented by transforming the coupled disturbances into the decoupled form. Secondly, the sliding mode observer is designed to estimate the decoupled disturbances and system states of nonlinear systems. The coupled disturbance can be reconstructed hereafter. The detailed methods of designing the observer, together with the sufficient condition to guarantee the existence of the observer are also given. Finally, a simulation and a robot manipulator experiment are provided to examine the validity of the proposed design approach.
By Markov jump systems (MJSs) modeling, this article investigates event-triggered asynchronous fault detection (FD) for quarter-car suspension system (QCSS) via zonotopic residual evaluation (RE). To ...save communication resources, a stochastic dynamic event-triggered scheme (DETS) is developed to transmit necessary sampled signals while considering deception attacks (DAs) during signal transmission. By means of the hidden Markov model (HMM) with partially accessible mode information, the asynchronization phenomenon between the original system and the FD filter (FDF) as well as the event generator is fully characterized. In such a framework, a mixed <inline-formula><tex-math notation="LaTeX">l_{1}/H_{\infty }</tex-math></inline-formula> asynchronous FDF design criterion is derived to guarantee the resultant residual system is sensitive to system fault while being robust to amplitude-bounded exogenous disturbances and measurement noise. Compared with existing results, the proposed approach avoids the mode synchronization limitation and the requirement of ideally known probability information in the transformed probability matrix and conditional probability matrix, and thus can be better applied to practical engineering while covering some previous works as special cases. Moreover, for the first time, a novel zonotope-based dynamic threshold evaluation approach is developed for FD in MJSs instead of the traditional constant threshold scheme for RE. Such an algorithm is designed to effectively avoid inappropriate human empirical threshold selection, which can both shorten the FD time and avoid false alarms hence ensuring satisfactory FD performance. Finally, a quarter-car suspension system is utilized to demonstrate the effectiveness of the proposed design strategy.
This paper presents a practical discrete-time fractional order terminal sliding mode (DFOTSM) control strategy for high-precision tracking tasks based on a linear motor. In particular, the practical ...parametric uncertainties involving sliding friction, uncertain payload, and disturbance in tracking tasks are considered in this paper. Combining Grünwald-Letnikov fractional order definition and terminal sliding mode technique, the proposed method synthesizes a novel DFOTSM control law to drive the sliding mode dynamics into the stable region in finite steps theoretically, even though the system is suffering from uncertainties and disturbances, and the motion on the surface can guarantee higher tracking precision than the conventional discrete-time terminal sliding surface by selecting suitable controller parameters. The theoretical analyses give out the guideline of parameter selection, and experiments are carried out on the linear-motor-based test platform to demonstrate that the proposed controller is easily implemented and can achieve high-precision tracking, fast response, and considerable robustness to uncertainties.
