This paper presents a method using the Global Positioning System (GPS)-measured course angle to improve the accuracy of the vehicle attitude estimation for low-cost inertial navigation system/GPS (INS/GPS) integration. Observability properties of the error states in the low-cost integration navigation system are first analyzed, indicating that the attitude estimation is severely affected by vehicle maneuvers, particularly the yaw angle. The pitch and roll angles are strongly observed; hence, the observability of these two angles is nearly free of influence caused by vehicle maneuvers, and these two angles can be accurately estimated. To improve the yaw-angle estimation, we propose a cascaded Kalman filter to deal with the yaw angle separately with the aid of the GPS-measured course angle. Additionally, two switching rules are established to remove the influence caused by the sideslip angle and GPS noise. The experimental results validate the observability analysis of the low-cost INS/GPS system and show that the proposed attitude estimation method can effectively improve the accuracy of the vehicle attitude estimation, suggesting that this technique is a viable candidate for many control applications used in cars.

In this paper, we develop a low-cost method to determine the vehicle attitude for vehicle-mounted satellite-communication (satcom)-on-the-move (SOTM) using a micro inertial measurement unit (MIMU) and a two-antenna global positioning system (GPS). An adaptive Euler-angle-based unscented Kalman filter (UKF) is utilized to fuse these sensors to guard against the effects induced by GPS outages and vehicle accelerations. When the two-antenna GPS can provide the vehicle yaw angle, the vehicle accelerations that introduce large errors to the accelerometer-measured gravitational acceleration can be corrected by the GPS-measured velocity and sideslip angle. When the two-antenna GPS fails to provide the yaw angle and needed information, the yaw angle is estimated only by integrating gyroscopes. The estimation of the pitch and roll angles is adaptively controlled by the vehicle acceleration detection rules. These rules make full use of the gyroscope output and the filtering results, which are more compatible with vehicle use than conventional accelerometer norm-based rule. The proposed method is verified with driving tests, suggesting that this technique is a viable candidate for low-cost SOTM.

This study proposes an asymmetric mapping method to design sparse planar arrays with multiple constraints including the aperture, number of elements and minimum spacing between adjacent elements. Benefiting from two different mapping functions, which are established in this paper, this approach allows one to overcome the limitations of the existing matrix mapping method in terms of flexibility and performances. The numerical validation points out that the proposed method outperforms the matrix mapping method and modified real genetic algorithm in the design of array arrangements.

Introduction: 2,5-Diketopiperazines (DKPs) are cyclic dipeptides from two amino acids with or without further structural modifications in DKP nucleus. These DKPs demonstrated attractive bioactive diversity and potential in drug discovery. Areas covered: This review summarized those bioactive DKPs in patents, and provided the analysis of the structure types (N-substitution, secondary cyclization, isopentenylation, S-substitution, dehydrogenation, and dimerization) and bioactivities including anti-tumor, neuroprotective, immune and metabolic regulatory, oxytocin inhibitory and anti-inflammatory effects, antibiotic activity, PAF inhibition, inhibition of plasminogen activator and T-cell mediated immunity, and insecticidal activity, etc. Expert opinion: Though DKPs did not show very complicated chemical structures, their rigid structure, chiral nature and varied side chains led to their various medicinal applications.