LONG-TERM VARIABILITY OF THE ION RUNOFF OF LARGE RIVERS IN THE ARCTIC ZONE OF RUSSIA

Studies of river ion runoff and its temporal variability are important. It affects coastal waters and is interrelated with climatic changes in the Arctic region. Long-term data on the chemical runoff of macrocomponents (chlorides, sulfates, hydrocarbonates, calcium and magnesium ions) at the outlet sections of large Arctic rivers in Russia - Pechora, Usa, Yenisei, Ob, Pur, Taz, Lena, Yana and Kolyma are given. The values of volumes and modules of chemical runoff were calculated on the basis of long-term (1980-2018) hydrological and hydrochemical information from the state observation system of Roshydrom-et. It is shown that the change in the absolute values of the chemical runoff is consistent with the water inflow. Greatest contribution to the ionic runoff is made by hydrocarbonates. The intra-annual change in the water inflow and the macrocomponents runoff occurs synchronously. There is a decisive role of water runoff in the formation of chemical runoff from the catchments of large Arctic rivers. Comparison of the chemical runoff modulus indicator made it possible to classify them into low, medium or high ionic runoff rivers. It was found that the maximum runoff of macrocomponents occurs from the catchment of the Usa river. It is may be due to active processes of chemical denudation and climate change.

Formation Control of Unmanned Vessels with Saturation Constraint and Extended State Observation

This paper addressed the formation control problem of surface unmanned vessels with model uncertainty, parameter perturbation, and unknown environmental disturbances. A formation control method based on the control force saturation constraint and the extended state observer (ESO) was proposed. Compared with the control methods which only consider the disturbances from external environment, the method proposed in this paper took model uncertainties, parameter perturbation, and external environment disturbances as the compound disturbances, and the ESO was used to estimate and compensate for the disturbances, which improved the anti-disturbance performance of the controller. The formation controller was designed with the virtual leader strategy, and backstepping technique was designed with saturation constraint (SC) function to avoid the lack of force of the actuator. The stability of the closed-loop system was analyzed with the Lyapunov method, and it was proved that the whole system is uniformly and ultimately bounded. The tracking error can converge to arbitrarily small by choosing reasonable controller parameters. The comparison and analysis of simulation experiments showed that the controller designed in this paper had strong anti-disturbance and anti-saturation performance to the compound disturbances of vessels and can effectively complete the formation control.

Sliding Mode Control of the Vehicle Speed System Based on LMIs

Due to the nonlinear characteristics of the vehicle speed system, its stability is difficult to control. This paper analyzes the stability and traceability of the vehicle speed system under nonlinear characteristics. A sliding mode control method of the nonlinear system state observation based on linear matrix inequalities (LMIs) is proposed. In the proposed control method, Lyapunov function is used as the control function to track the position and speed of the vehicle speed system in real time. In the design process of the controller, the successive scaling method (SSM) is designed to improve the tracking accuracy. The simulation results demonstrate that the sliding mode control can effectively track the position of the vehicle speed system, which has better stability and traceability for the nonlinear vehicle speed system.