A Path-Planning Strategy for Unmanned Surface Vehicles Based on an Adaptive Hybrid Dynamic Stepsize and Target Attractive Force-RRT Algorithm

It is well known that path planning has always been an important study area for intelligent ships, especially for unmanned surface vehicles (USVs). Therefore, it is necessary to study the path-planning algorithm for USVs. As one of the basic algorithms for USV path planning, the rapidly-exploring random tree (RRT) is popular due to its simple structure, high speed and ease of modification. However, it also has some obvious drawbacks and problems. Designed to perfect defects of the basic RRT and improve the performance of USVs, an enhanced algorithm of path planning is proposed in this study, called the adaptive hybrid dynamic stepsize and target attractive force-RRT(AHDSTAF-RRT). The ability to pass through a narrow area and the forward speed in open areas of USVs are improved by adopting the AHDSTAF-RRT in comparison to the basic RRT algorithm. The improved algorithm is also applied to an actual gulf map for simulation experiments, and the experimental data is collected and organized. Simulation experiments show that the proposed AHDSTAF-RRT in this paper outperforms several existing RRT algorithms, both in terms of path length and calculating speed

An Improved Lexicographic MO-MPC Based on Linear Decomposition

A computational efficient multiobjective model predictive control (MO-MPC) scheme with prioritized objectives is proposed for linear time-invariant system with state and input constraints. The terminal states are decomposed into several auxiliary decision variables and then the traditional terminal control law is parameterized by using the several corresponding controller gains. According to the priorities of multiple objectives, the MO-MPC problem is reformulated as a multi-layer single objective one. Moreover, by establishing the conditions on the most important objective, the recursive feasibility and asymptotic stability properties of the designed MO-MPC are proved by the method of the triplet of the terminal constraints, terminal penalty functions and local state feedback laws. Finally, the advantages of the new MO-MPC are illustrated by a numerical example in terms of the enlargement of terminal set and the low computation loads

Phase Residual Estimations for PCVs of Spaceborne GPS Receiver Antenna and Their Impacts on Precise Orbit Determination of GRACE Satellites

AbstractIn-flight phase center systematic errors of global positioning system (GPS) receiver antenna are the main restriction for improving the precision of precise orbit determination using dual-frequency GPS. Residual approach is one of the valid methods for in-flight calibration of GPS receiver antenna phase center variations (PCVs) from ground calibration. In this paper, followed by the correction model of spaceborne GPS receiver antenna phase center, ionosphere-free PCVs can be directly estimated by ionosphere-free carrier phase post-fit residuals of reduced dynamic orbit determination. By the data processing of gravity recovery and climate experiment (GRACE) satellites, the following conclusions are drawn. Firstly, the distributions of ionosphere-free carrier phase post-fit residuals from different periods have the similar systematic characteristics. Secondly, simulations show that the influence of phase residual estimations for ionosphere-free PCVs on orbit determination can reach the centimeter level. Finally, it is shown by in-flight data processing that phase residual estimations of current period could not only be used for the calibration for GPS receiver antenna phase center of foretime and current period, but also be used for the forecast of ionosphere-free PCVs in future period, and the accuracy of orbit determination can be well improved

Do Electronic Coupon-Using Behaviors Make Men Womanish? The Effect of the Coupon–Feminine Stereotype

Why are men less likely to use electronic coupons than women? Previous studies have explained the gender difference in coupon usage by exploring roles within the household and personality traits of the sexes. However, this research offers a novel explanation for this phenomenon, that men’s reluctance to use e-coupons may derive from the prevalent stereotype that e-coupon users are feminine. Because of the feminine stereotype associated with e-coupon usage, acquiring and using e-coupons are inconsistent with men’s gender identity. Five studies combining real data analysis, an online survey and experiments are used to support the previous notion. Using e-coupon acquisition data from a platform, study 1 tests whether females are more likely to acquire and use e-coupons than males in the real world. Study 2 experimentally tests the coupon–feminine stereotype. Study 3 explores the mediation effect of gender identity threat. Study 4 and study 5 consider two boundary conditions under which male consumers may be motivated to use e-coupons: when male consumers’ masculine identity is affirmed, and when the association between e-coupons and femininity is weakened. The results explain the gender difference in e-coupon usage from the novel lens of the coupon–feminine stereotype, offering a new and important perspective to explore the effect of gender identity on coupon use. Practical implications such as breaking the coupon–feminine stereotype, adopting a masculine design and communicating an affirmation of gender identity are further discussed

Integer phase clock method with single-satellite ambiguity fixing and its application in LEO satellite orbit determination

Fixing single-satellite GPS carrier phase ambiguity could significantly improve the orbit accuracy of low earth orbit (LEO) satellite. Currently, the CNES/CLS,Wuhan University and CODE have published GPS integer phase clock products applied to single-satellite ambiguity fixing. In this paper,the integer phase clock method is used for single-satellite ambiguity fixing, and it is applied to the precise orbit determination of LEO satellite. Then, the application performances of integer phase clock products provided by different agencies in single-satellite ambiguity fixing and LEO satellite orbit determination are compared and analyzed. For GRACE-FO formation satellites, about 94% ambiguities could be fixed based on different products provided by the three agencies.Orbit solutions generated using the products from the three agencies can achieve an RMS of around 0.9 cm checked by satellite laser ranging data.Compared with ambiguity-float orbit solutions, the accuracy of absolute orbit determination with single-satellite ambiguity fixing is improved by about 30%.After fixing single-satellite ambiguities using the different products provided by CNES/CLS, WHU and CODE, respectively, the RMS of K-band ranging validation residuals for relative orbit solutions are reduced from 5.7、 5.4 and 5.3 mm to 2.1、 2.0 and 1.5 mm, respectively. The results show that the integer phase clock products provided by different agencies have similar performances in the single-satellite ambiguity fixing and orbit determination of GRACE-FO satellite