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A teleoperation robot system is connected through a network. However, stochastic delay in such a network can affect its performance, or even make the system unstable. To solve this problem, this paper proposes a teleoperation robot system control method based on fuzzy sliding mode. In the proposed method, a delay generator generates variable delay conforming to a shift gamma distribution designed to simulate actual network delay. In addition, a proposed fuzzy sliding mode controller based on switching gain adjustment is used to rectify the chattering phenomenon in the sliding mode controller of the teleoperation robot system. In the controller, the master hand uses impedance control and realizes feedback from the slave hand. Controller simulation comparison results show that the proposed fuzzy sliding mode controller effectively eliminates the sliding mode control chattering phenomenon as the slave hand stabilizes the tracking velocity of the master hand. Consequently, the system exhibits improved dynamic performance.

Eutrophication and exotic species invasion are key drivers of the global loss of biodiversity and ecosystem functions in lakes. We selected two exotic plants (Alternanthera philoxeroides and Myriophyllum aquaticum) and two native plants (Myriophyllum spicatum and Vallisneria spinulosa) to elucidate the effect of eutrophication on exotic plant invasiveness. We found that (1) elevated nutrient favored invasion of exotic species and inhibited growth of native plants. Species combinations and plant densities of native plants had limited effects on the resistance to invasion of the exotics. (2) A. philoxeroides featured the tightest connectivity among traits, which is consistent with its high competitive ability. Although eutrophication caused physiological stress to A. philoxeroides, it could effectively regulate enzyme activity and alleviate the stress. (3) M. aquaticum possessed strong tolerance to habitat disturbance and was highly disruptive to the surrounding plants. Eutrophication will exacerbate the adverse effects of M. aquaticum on the littoral ecosystem. (4) Nutrient enrichment reduced the biomass and relative growth rates of V. spinulosa and lowered phenolics and starch contents of M. spicatum, thereby making them more susceptible to habitat fluctuations. Overall, our study highlights how eutrophication alters the invasiveness of exotic plants and the resistance of native plants in the littoral zone, which is of relevance in a world with intensified human activities.

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