Servo System Identification Based on Curve Fitting to Phase-Plane Trajectory

Many methods have been proposed to identify servo system parameters. However, problems still remain in widely applied offline identification methods, for example, the describing-function-based relay feedback method has the ineradicable approximation error, and acceleration information is indispensable for the least-squares method. In order to identify systems accurately and efficiently with less servo system information, this article proposes a novel method to identify servo system parameters through curve fitting to the phase-plane trajectory under the help of one optimization method. Specifically, the phase-plane trajectory expression of the single-degree-of-freedom system is derived; the process on how to convert the servo system identification problem to a curve-fitting optimization problem is described in detail; and the guidelines of the initial parameter setting are introduced. Simulations and experiments are carried out to verify the efficiency of the proposed method. Finally, a feed-forward control based on the identified parameters is designed to further validate the identification accuracy.

Fault Detection of a Reusable Rocket Engine using Phase Plane Trajectory of Feature Vectors

A bivariate time-series analysis based on the phase plane trajectory of feature vectors extracted by principal component analysis is developed for fault detection in a reusable liquid-propellant rocket engine. Static-firing test results of the reusable rocket engine obtained at the Japan Aerospace Exploration Agency are employed for demonstration of the present method. The present method successfully detected temperature sensor failure from 19 firing tests of 62 sensors, even in the deviation of the engine operational sequence between the static-firing tests. The present method was also able to detect the system failure from 23 firing tests. Furthermore, the ability to distinguish the system and sensor failure was demonstrated.

Examination of the Accuracy and Usefulness of Garmin and Suunto GNSS Devices during Navigation of the TS-11 “Iskra” Jet Aircraft

This study was designed and performed in order to determine the accuracy and usefulness of different modern Garmin and Suunto GNSS devices – mainly smartwatches – during a flight of TS-11 “Iskra” aircraft. The plane trajectory was determined using six different navigation devices placed in a cockpit of an aircraft. To calculate reference position – Thales Mobile Mapper with post-processing option and data from Polish ASG-EUPOS network was used. The obtained results show that the tested devices gave reasonable positioning accuracy and can be used on board of an aircraft traveling at high speeds. However, it must be emphasized that smartwatches can be only used as a supplementary navigation aid during any air operation.