INSIGHT INTO SPATIAL ANALYSIS OF GPS BROADCAST ORBIT ERROR TOWARDS ORBITAL IMPROVEMENT

Broadcast orbits are compared against final orbit to get the error of broadcast orbit. The errors are analysed by presenting the error over space, especially longitude. The satellite trajectory is divided into three sector namely northern, southern, and transitional sectors. Spatial analysis show that the error is correlated with the latitude and longitude. Some consistency pattern can be observed from the distribution of the error in the spatial analysis. Standard deviation (SD) is used to quantify the consistency, providing more quantitative insights into the spatial analysis. Four patterns can be observed in the error distribution, namely consistency in northern and southern sector, consistency of transitional sector, changes after transitional sector, and correlation between ΔX component and ΔY component. The spatial analysis shows potential to be used in broadcast orbit error estimation and prediction. A model that uses this predicted broadcast orbit error as a correction will be designed in the future to improve the broadcast orbit accuracy.

Error Estimation of Measured Exhaust Gas Temperature in Afterburner Mode in an Aero Gas Turbine Engine

In a turbofan engine, thrust is a key parameter which is measured or estimated from various parameters acquired during engine testing in an engine testbed. Exhaust Gas Temperature (EGT) is the most critical parameter used for thrust calculation. This work presents a novel way to measure and correct the errors in EGT measurement. A temperature probe is designed to measure EGT in the engine jet pipe using thermocouples. The temperature probe is designed to withstand the mechanical and temperature loads during the operation. Structural analysis at the design stage provided a strength margin of 90% and eigenfrequency margin of more than 20%. Thermal analysis is carried out to evaluate maximum metal temperature. Errors are quite high in high-temperature measurements which are corrected using the available methodologies. The velocity error, conduction error, and radiation error are estimated for the measured temperature. The difference of 97 K between the measured gas temperature and calculated gas temperature from measured thrust is explained. The estimated velocity error is 1 K, conduction error is 3 K, and radiation error is 69 K. Based on the error estimation, the measurement error is brought down to 24 K. After applying the above corrections, the further difference of 24 K between measured and estimated value can be attributed to thermocouple error of +/-0.4% of the reading for class 1 accuracy thermocouple, other parameter measurement errors, and analysis uncertainties. The present work enables the designer to calculate the errors in high-temperature measurement in a turbofan engine.

A posteriori verification of the positivity of solutions to elliptic boundary value problems

The purpose of this paper is to develop a unified a posteriori method for verifying the positivity of solutions of elliptic boundary value problems by assuming neither $$H^2$$ H 2 -regularity nor $$ L^{\infty } $$ L ∞ -error estimation, but only $$ H^1_0 $$ H 0 1 -error estimation. In (J Comput Appl Math 370:112647, 2020), we proposed two approaches to verify the positivity of solutions of several semilinear elliptic boundary value problems. However, some cases require $$ L^{\infty } $$ L ∞ -error estimation and, therefore, narrow applicability. In this paper, we extend one of the approaches and combine it with a priori error bounds for Laplacian eigenvalues to obtain a unified method that has wide application. We describe how to evaluate some constants required to verify the positivity of desired solutions. We apply our method to several problems, including those to which the previous method is not applicable.

Reinforcement Learning Path Planning Method with Error Estimation

Path planning is often considered as an important task in autonomous driving applications. Current planning method only concerns the knowledge of robot kinematics, however, in GPS denied environments, the robot odometry sensor often causes accumulated error. To address this problem, an improved path planning algorithm is proposed based on reinforcement learning method, which also calculates the characteristics of the cumulated error during the planning procedure. The cumulative error path is calculated by the map with convex target processing, while modifying the algorithm reward and punishment parameters based on the error estimation strategy. To verify the proposed approach, simulation experiments exhibited that the algorithm effectively avoid the error drift in path planning.