Eveline Gottzein

Paper: Control aspects of a tracked magnetic levitation high speed test vehicle

The paper deals with the control system of the high speed test vehicle KOMET. The control hardware configuration consisting of digital computer, interface, sensors, magnet drivers and magnets is described. Control system synthesis is performed based on the state space approach and the classical approach of the z-transform. It leads to various control concepts, which are evaluated with regard to their responses to guideway irregularities, external forces and their sensitivity to plant parameter variations. The measurements used to reconstruct the state vector are magnet gaps, vehicle accelerations and/or magnet currents. To be efficient, the magnets have to be operated on small magnet gaps. This demands a fast system response to external disturbances and guideway inputs. This in turn may lead to the excitation of the elastic modes of the system. The higher order modes of vehicle and guideway are therefore included in the control synthesis. The speed range of the KOMET extends to 400 km/hr. Results from high speed testing are evaluated with regard to system responses, power requirements, and loss in magnetic force due to eddycurrents.

Modernized Spaceborne GNSS Receivers

The further development of navigation receivers has to go hand in hand with the advances in the constellations for Global Navigation Satellite Systems (GNSS). As more and more features will be provided by the services of modernized GPS, GLONASS and the upcoming Galileo and COMPASS, the functions and performance of spaceborne GNSS receivers have to be extended as well. Today, the MosaicGNSS Receiver is operating in space using only the GPS L1 civil signal. Its successor, the LION Navigation Receiver, is currently under development for using all open civilian signals of GPS, Galileo and COMPASS.

Feasibility of GNSS receivers for satellite navigation in GEO and higher altitudes

GPS is successfully used for spacecraft navigation in low Earth orbits. This paper investigates the feasibility of Global Navigation Satellite System (GNSS) receivers for spacecraft navigation in GEO, GTO, and higher orbits. The study is based on the experience gained at EADS Astrium from developing GNSS receivers for satellites as well as the requirements and feedback from satellite manufacturers and operators. The performance results are computed using the onboard navigation core algorithms of the MosaicGNSS receiver and the LION Navigator.

New applications for navigation receivers in space

The further development of navigation receivers has to go hand in hand with the advances in the constellations for Global Navigation Satellite Systems (GNSS). As more and more features will be provided by the services of modernized GPS, GLONASS and the upcoming Galileo and Compass, the functions and performance of spaceborne GNSS receivers have to be extended as well. Today, the MosaicGNSS Receiver is operating in space using only the GPS L1 civil signal. Its successor, the LION Navigator, is currently under development for using all open civilian signals of all GNSS constellations.

Commercial Use of GNSS Signals in GEO

Abstract Geostationary orbit determination using GNSS (GPS/GLONASS) signals is an attractive option compared to existing ground based orbit determination techniques. This paper addresses the commercial application of GNSS receivers for geostationary navigation. The major issues of geostationary GNSS navigation are weak signal-ta-noise-density ratio and poor geometrical satellite distribution and visibility. The investigations and system trade-offs presented here are based on the MosaicGNSS receiver (EADS Astrium GmbH) and the ARN GEO receiver (NPO-PM). The receiver hardware is outlined and a review of the properties of a geostationary mission with respect to GNSS applications is given.

Control Aspects of a Tracked Magnetic Levitation High Speed Test Vehicle

Summary The paper deals with the control system of the high speed test vehicle KOMET. The control hardware configuration consisting of digital computer, interface, sensors, magnet drivers and magnets is described. Control system synthesis is performed based on state space approach and the classical approach of z-transform. It leads to various control concepts, which are evaluated with regard to their responses to guideway irregularities, external forces and their sensitivity to plant parameter variations. The measurements used to reconstruct the state vector are magnet gaps, vehicle accelerations and/or magnet currents. To be efficient, the magnets have to be operated on small magnet gaps. This demands a fast system response to external disturbances and guideway inputs. This in turn may lead to the excitation of the elastic modes of the system. The higher order modes of vehicle and guideway are therefore included in the control synthesis. The speed range of the KOMET extends to 400 km/h. First results from high speed testing are evaluated with regard to system responses, power requirements, and loss in magnetic force due to eddycurrents.

Experimental Evaluation of the Micro-Tech.-Sensor for Attitude and Orbit Determination

Abstract In the frame of ESAs Technology Flight Opportunity the MTS-AOMS sensor for autonomous attitude and orbit determination of satellites was flown on the Italian microsatellite platform MITA (Melf and Manhart, 2000). The system is characterized by a beamsplitter, which provides two non-collinear lines-of-sight so as to be used in a “sextant-mode”. The detector is based on active pixel technology. Additionally, the unit flown included a Magnetic Field Sensor (MFS) as well as an Angular Rate Sensor (ARS) in such a way that the sensors complement each other to form a multifunctional micro-systems-technology device for an attitude and orbit measurement system. The paper is concerned with an initial evaluation of performance based on various algorithms and experiments.

Effectiveness of Different Optimum Filtering Techniques for the Particular Example of Radio Guidance of the Third Stage of Europa 1 Carrier Vehicle

Summary For the particular example of the radio guided third stage of EUROPA 1 carrier vehicle two different optimum filtering techniques have been compared: The augmented state version actually implemented in the downrange guidance computer (formulated in ref. 3) and a measurement differencing type filter (ref. 4 and 5). The problem is nonlinear and the noise superimposed on state components and measurements is assumed to be sequentially correlated. Six downrange guidance station measurements (two short base interferometer-, two long base interferometer-, range- and range rate measurements) are used to update the state information once in a second (continuous time-discrete data problem). Identical random sample functions have been used in both cases to drive the noise models of the system, allowing for a comparison of the estimation errors and covariances at individual instances. The two filter versions are equivalent as for the final estimation accuracy of vehicle position- and velocity components, the transient behaviour, however, is different. For the nonlinear problem under discussion, the implementation of the measurement differencing filter does not save computation time as compared to the augmented state version, since the time gained in processing the reduced state vector and covariance matrix is used up again by additional computations required.