RESUMO
This paper proposes a novel robust differential game scheme to solve the collision avoidance problem for networked multi-agent systems (MASs), subject to linear dynamics, external disturbances and limited observation capabilities. Compared with the existing differential game approaches only considering obstacle avoidance objectives, we explicitly incorporate the trajectory optimization target by penalizing the deviation from reference trajectories, based on the artificial potential field (APF) concept. It is proved that the strategies of each agent defined by individual optimization problems will converge to a local robust Nash equilibrium (R-NE), which further, with a fixed strong connection topology, will converge to the global R-NE. Additionally, to cope with the limited observation for MASs, local robust feedback control strategies are constructed based on the best approximate cost function and distributed robust Hamilton-Jacobi-Isaacs (DR-HJI) equations, which does not require global information of agents as in the traditional Riccati equation form. The feedback gains of the control strategies are found via the ant colony optimization (ACO) algorithm with a non-dominant sorting structure with convergence guarantees. Finally, simulation results are provided to verify the efficacy and robustness of the novel scheme. The agents arrived at the targeted position collision-free with a reduced arrival time, and reached the targeted positions under disturbance.
RESUMO
It is of great significance to clarify the influence of soil temperature and moisture on soil respiration rate and its characteristics in ecologically fragile regions under the background of climate change for the accurate assessment and prediction of carbon budgets in this region. The average CO2 concentration and soil temperature and moisture at different soil depths (10, 50, and 100 cm) were measured using a CO2 analyzer and temperature and moisture sensors. The soil respiration rate was calculated using Fick's first diffusion coefficient method. The dynamic characteristics of soil temperature, soil moisture, and soil respiration rate in different soil depths were explored, and the response of soil respiration rate to soil temperature and moisture were further analyzed. The results showed that the diurnal variation in soil respiration rate decreased significantly with the increase in soil depth (P<0.05), and the peak time lagged behind. Soil respiration rate in adjacent soil depths (10, 50, and 100 cm) lagged 1 h from top to bottom. The monthly variation in soil respiration rate was a multi-peak curve, in which the maximum soil respiration rates of 10, 50, and 100 cm soil depths were on July 25th, August 6th, and August 10th, reaching 13.96, 2.96, and 1.47 µmol·(m2·s)-1, respectively. The effect of soil temperature on soil respiration rate decreased with the increase in soil depth. Soil temperature at 50 cm and below had no significant effect on soil respiration rate (P>0.05). The fitting index of 10 cm soil depth was the best (R2=0.96), but the fitting indexes of 50 cm and 100 cm soil depths were poor (R2=0.00 and R2=0.01, respectively). The temperature sensitivity coefficient Q10 decreased with the increase in soil depth. Soil moisture in different soil depths had significant effects on soil respiration rate (P<0.05), and the quadratic fitting indicated that 50 cm (R2=0.35)>10 cm (R2=0.22)>100 cm (R2=0.31). The combined effects of soil temperature and moisture in different soil depths could explain 96%, 6%-50%, and 22%-24% of soil respiration rate, respectively. In summary, the effects of soil temperature and moisture at different soil depths of the Caragana korshinskii plantation in the loess-hilly region on soil respiration rate differed. The soil respiration rate of the 10 cm soil depth was affected by the comprehensive effect of soil temperature and moisture; however, the relative contribution of soil temperature was higher, and soil moisture at and below a soil depth of 50 cm was the key factor. These results could help improve predictions on the impact of future climate change on the carbon cycle of terrestrial ecosystems in the region and provide a theoretical basis for greenhouse gas regulation in the future.
