Research On Ejection Test System Based On GPS

Ejection seat is a device which rescues the pilot by taking him out of the danger in case of emergency. Plenty of tests must be done to validate every life-support performance before finalizing the design of ejection seat. Currently the ejection test relies on photo-graphic measurement and radio remote measurement. GPS-based position & velocity testing device is an advanced test technology. Integrated with advanced data processing technology, a new ejection test technology can be applied, and a powerful test system can be build. It is significative on theory and practicality for aviation test measurement.To convenience the definition and conversion of test result, time reference and space reference must be defined firstly on engineering test. There are some kinds of time-references and space-references involved in GPS-based test system. Firstly this dissertation defined time-reference and space-reference of ejection test system.GPS-based ejection test system consists of three parts, which includes ground GPS test base station, ground data process computer and airborne test station. The ground base station and airborne test station make of differential GPS position. Because the test result acquired by post data process, so there is no real-time process demand. There is no data link layer between ground base station and airborne test station. All test data must be stored into test device synchronously so it can be process after test.Proper position algorithm can improve the test performance effectively. According the dynamic characteristics of the testing target, this dissertation presents post-process algorithm of carrier phase to improve test performance. Post data process uses the raw measurements provided by the GPS-OEM receiver to acquire higher data rate. To avoid missing and losing message frame, it adopts slide-window algorithm to code the binary data stream and to acquire measurement data and ephemeris data. This dissertation adopts double-difference observe model between station and satellite to resolve carrier phase differential position.Because of weak correlativity between base station and airborne station, the test error introduced by random noise can not be eliminated or weakened by differential algorithm. It can be eliminated effectively by adjustment value and filtering. Redundancy of measurements is the pre-condition of adjustment value. Apply least square law to long-direction adjust the single epoch measurement to minish the observe error. The Kalman filter is the best optimal estimator. It can estimate the true state of the system from signals including noise. But the Kalman filter works effectively only in case of building an accuracy process model and measurement model. When the filtering model can not match the actual system, the filtering precision decreased, badly it can cause filtering diverging. Based on the characteristics of the testing target, this dissertation analyses and simulates the filtering effect under different system models; and adopted the current statistical models of acceleration and adaptive Kalman algorithm. The simulation results and actual test filtering results indicate that the testing precision be improved effectively.According plenty of test researches, it is feasible that apply GPS to ejection test; Proper position algorithm and filtering algorithm can acquire sub-meter precision. It must be resolved in engineering application that how to settle the lost-lock of the signal of satellites under the high dynamic test condition. Finally this dissertation discusses some ground enhanced systems that can be used in engineering application.The innovation works of the dissertation including:1. Introduced differential GPS position into ejection test, produced new test means, improved test proformance and test automatization.2. Integrated the post-process of static differential position and dynamic differential position, solved the problem of dynamic position and velocity measurement.3. Used the long-direction and lateral-direction adjustment filtering algorithm; built the current statistical model of acceleration and adaptive Kalman algorithm, improved the anti-jamming of post data process and test performance.In company with the project of GPS modernization and the construction of GLONASS and Galileo, satellite-position will play more important role on the ejection test.