A pose graph optimization method employing nonlinear factor recovery was created in order to accomplish high-precision vehicle pose estimation in urban road situations. This method successfully incorporates vision, inertial information, and global navigation satellite system (GNSS) data inside the factor graph framework. To address the issue of unclear covariance estimation in previous pose graph optimization algorithms, the nonlinear factor recovery algorithm extracts the required information from the dense prior factors generated by marginalization, replacing the prior factors with relative pose factors and conducting optimal estimates for the covariance matrices of these factors. A procedure utilizing visual-inertial odometry for the active detection of GNSS signal anomalies has been designed, capable of adaptively adjusting the covariance matrix of GNSS signals. Throughout the pose graph optimization process, these strategies guaranteed consistency of factor information. Tests conducted on datasets and in real road environments indicate that this approach significantly improves the fusion efficiency of multisource asynchronous signals, providing robust and globally consistent high-precision pose estimation results.

An integrated boost impeller can effectively improve the suction performance of an aircraft hydraulic pump (AHP). It must be designed very carefully; however, few studies thus far have investigated boost impellers. To explore the effect of the boost impeller, this study developed a three-dimensional computational fluid dynamics (CFD) model for an AHP based on the k-ε turbulence model and full cavitation model. The results of verification tests demonstrated that the model is reliable for simulating the delivery characteristics of piston pumps and the boost capacity of the inlet impeller. Steady-state simulations reveal that the boost impeller can remarkably improve the suction performance and mitigate the cavitation damage due to insufficient fluid filling while only consuming a small proportion of the total input power. Transient-state simulations show that the pump with an impeller is more capable of catching up with a sudden increase in flow demand, and it has a lower suction flow ripple and impact. However, such a boost impeller also has some limitations such as magnifying the suction pressure fluctuation and having little effect on mitigating the cavitation caused by the back-flow jet.