This paper describes the concept of a multilayer brushless DC motor which is suitable for use on unmanned aerial vehicles (UAVs) and capable of carrying a heavy payload. The paper deals with a unique multilayer structure, using three standard stators placed in parallel with a single rotor body, to increase the torque even under low-speed conditions. In this solution, nine inner windings can use different star/delta interconnections to optimize the performance of the BLDC motor on demand. The proposed multilayer BLDC motor solution utilizes the main advantages of BLDC motors, ensuring highly reliable operation, and thus enabling a BLDC motor to be applied to UAVs. This paper gives an overview of the design, assumes an extension with an electronic inner winding switching capability, and provides practical details about realization, testing, and experimental verification. Practical measurements and obtained data are utilized to confirm the approach.
A low-cost aerometric sensor system for sport aviation
The paper deals with the concept, the design and an experimental prototype of a low-cost aerometric sensor system for sport aviation. The performance of an experimental prototype of the sensor system is compared with the performance of a standard system. The possible further development of the system is also mentioned. The system presented here originates from and extends earlier basic work on an aerometric system for general aviation. The extension implements and focuses general designs from the earlier system for real use of the current system in the category of sport airplanes and gliders. The objective of the system is to reduce the cost of aircraft instrumental equipment, and to provide improved measurement performance of the aerometric system using an innovative approach of altitude measurements. In the experimental system, altitude is still determined based on the classic barometric principle. However, for measurements of atmospheric pressure, the differential pressure sensor is used primarily in combination with a low-cost absolute pressure sensor, which also measures in a differential mode.
V čase rozšiřování využívání GNSS systémů v široké oblasti aplikací a to i v rámci strategické infrastruktury vyvstává potřeba systému detekujícího případné rušení tohoto signálu za účelem snížení provozuschopnosti dané infrastruktury. Příspěvek popisuje systém detektoru rušení GNSS signálu GIDeLoc (GNSS Interference Detector and Localizer), jeho funkce a složení. Současně popisuje proceduru zastaničení, která slouží pro inicializaci systému před jeho nasazením, způsob synchronizace mezi jednotlivými měřicími stanovišti a postupy výpočtů relevantních k požadovaným výstupům ze systému.
Příspěvek popisuje proceduru zastaničení systému detektoru rušení GNSS signálu GIDeLoc (GNSS Interference Detector and Localizer). Celá procedura zastaničení se dá rozdělit na tři části a to sice: i) určení orientace anténního pole, ii) určení délek základen a jejich azimutů vzhledem k zeměpisnému severu a iii) určení absolutních pozic měřicích stanovišť. První část je řešena pomocí dvou anténního systému Tersus BX316D (ověřena i s µBlox NEO-M8P), µBlox přijímač je využíván i v dalších fázích s využitím RTKlib a rozdílových měření mezi jednotlivými stanovištěmi (druhá fáze) či se srovnáním s referenčními GNSS stanicemi sítě CZEPOS.
Návrh a realizace bezpilotního prostředku typu kvadrokoptéra
Příspěvek popisuje návrh a realizaci bezpilotního prostředku typu kvadrokoptéra. Bezpilotní prostředek je založen na jednodeskovém PC Arduino Nano, ke kterému je připojen modul s magnetického kompasu, teplotní a tlakový senzor a inerciální měřicí jednotka MPU-6050. Komunikace s PC je zajištěna pomocí Bluetooth rozhraní a veškeré bloky jsou spojeny přes Arduino Nano shield, který rovněž zabezpečuje napájení všech dílčích komponent. Rám kvadrokoptéry byl navržen a vytisknut na 3D tiskárně.
Systém pro odhalování nezákonného rušení GNSS sign álu
V čase stálého rozšiřování využívání GNSS systémů v široké oblasti aplikací, a to i v rámci strategické infrastruktury vyvstává potřeba systému detekujícího případné rušení GNSS signálu ohrožující provozuschopnost dané infrastruktury. Tento příspěvek popisuje systém, který je schopen odhalovat takovéto rušení typu „jamming“ a „spoofing“. Systém poskytuje uživateli informaci o spolehlivosti a integritě GNSS signálu a lokalizaci zdroje rušení. Zamezí tak případným nehodám či hrozbám vedoucím ke snížení bezpečnosti provozu infrastruktury, která využívá informace o poloze a času získané z GNSS.
Validation of nonlinear integrated navigation solutions
There exist numerous navigation solutions already implemented into various navigation systems. Depending on the vehicle in which the navigation system is used, it can be distinguished in most cases among; navigation, tactical, and commercial grade categories of such systems. The core of these systems is formed by inertial sensors, i.e. accelerometers and angular rate sensors/gyros. Navigation and tactical grade systems commonly rely on fiber optic/ring laser gyros and servo/quartz accelerometers with high resolution, sensitivity, and stability. In the case of cost-effective navigation systems, for example piloted light and ultralight aircraft, usually use commercial grade sensors, where the situation differs. The sensor outputs are less stable and sensitive, and suffer from manufacturing limits leading to temperature dependency, bias instability, and misalignment which introduces non-negligible disturbances. These conditions commonly limit the applicability of the navigation solution since its stand-alone operation using free integration of accelerations and angular rates is not stable. This paper addresses a cost-effective solution with commercial grade inertial sensors, and studies the performance of different approaches to obtain navigation solution with robustness to GNSS outages. A main goal of this paper is thus comparison of a nonlinear observer and two extended Kalman filter solutions with respect to the accuracy of estimated quantities and their sensitivity to GNSS outages. The performance analyses are carried out on real flight data and evaluated during phases of the flight when the solutions are challenged by different environmental disturbances.
Modified Biaxial Accelerometer Framework in G-sensing Mode
This paper deals with an acceleration measuring unit, which uses two biaxial accelerometers, and compares its performance with a typical triaxial framework. In cases of small aircrafts, UAVs, robots, or terrestrial vehicle navigation units utilizing sensors manufactured by a MEMS technology are preferred due to their cost-effectiveness. In order to suppress imperfections of the measuring system (noise, drift, nonlinearities, small sensitivity) a solution based on the difference configuration of accelerometers is proposed.
Navigační systém pro bezpilotní prostředky a ultralehká letadla
Tento příspěvek popisuje kompletní návrh a vývoj navigační jednotky pro ultralehká letadla a bezpilotní prostředky. Jednotka se skládá z MEMS inerciálních senzorů, magnetometru, snímače statického tlaku a přijímače družicové navigace. Příspěvek popisuje vývoj potřebné elektroniky a SW zajišťující fungování dané jednotky. Dále popisuje návrh a vývoj algoritmů rozšířeného Kalmanova filtru pro odhad pozice a orientace. Pro zlepšení kvality odhadu navigačních dat byla jednotka také nakalibrována. Ověření parametrů navigační jednotky bylo provedeno při skutečných letových experimentech.
Validation and Experimental Testing of Observers for Robust GNSS-Aided Inertial Navigation
This chapter is the study of state estimators for robust navigation. Navigation of vehicles is a vast field with multiple decades of research. The main aim is to estimate position, linear velocity, and attitude (PVA) under all dynamics, motions, and conditions via data fusion. The state estimation problem will be considered from two different perspectives using the same kinematic model. First, the extended Kalman filter (EKF) will be reviewed, as an example of a stochastic approach; second, a recent nonlinear observer will be considered as a deterministic case. A comparative study of strapdown inertial navigation methods for estimating PVA of aerial vehicles fusing inertial sensors with global navigation satellite system (GNSS)-based positioning will be presented. The focus will be on the loosely coupled integration methods and performance analysis to compare these methods in terms of their stability, robustness to vibrations, and disturbances in measurements.
Calibration of a multi-sensor inertial measurement unit with modified sensor frame
Calibration of the inertial measurement units (IMU) used in navigation systems are crucial for ensuring accuracy of a navigation solution. It is common to discuss what calibration means, techniques, and algorithms can be utilized and implemented. For cost-effective measurement units it is desirable to use calibration means and approaches which are not expensive yet capable of providing sufficient accuracy. This paper thus focuses on multi-sensor inertial measurement unit which utilizes a modified sensor frames. Unlike the common IMUs which consist of 3-axial accelerometer and gyroscope frames, the proposed concept of the multi-sensor unit consists of ten modified accelerometer frames supplemented by an unmodified gyro frame. The modified frames of accelerometers are optimized for differential analogue signal processing in order to increase signal-to-noise ratio and hence overall sensing precision. Since the proposed concept of the measurement unit includes higher number of sensing frames it is required to develop a novel “easy to do and implement” calibration method which is the contribution of this paper. The proposed calibration approach was experimentally verified and results confirmed its usability.
Calibration of the Low-cost Triaxial Inertial Sensors
Proper calibration is a key step in development of inertial sensors. Calibration equipment is often expensive in comparison with the cost of low-cost inertial systems. This work presents an alternative solution in the form of an All-In-One calibration platform that allows accelerometers and gyroscopes calibration without specific requirements on having precise and thus expensive calibration means. The calibration platform consists of a manually driven rate table, referential system comprising a precise fiber optic gyroscope and dual-axis inclinometer, and a gimbal structure allowing 3D rotation of a sensor being calibrated. This paper describes a calibration process using the calibration platform as well as full calibration of two commercial MEMS inertial measurement units, where the scale factors, axis misalignment/non-orthogonalities, and offsets are determined. All results are also compared with the ones obtained from an independent laser beam pointing device.
MDS 2015 - Měření, diagnostika, spolehlivost palubních soustav letadel. Brno: Univerzita obrany, Fakulta vojenských technologií, 2015, pp. 211-218. ISBN 978-80-7231-434-8. Available from: http://www.unob.cz/fvt/struktura/k206/Stranky/MDS_PSL_Aktualni.aspx
V současnosti je přesné určení úhlů náklonu vyžadováno v mnoha aplikacích jako například v geodetických aplikacích, v avionice, pro stabilizaci kamer, atd. Výsledná přesnost určení náklonů je přímo úměrná ceně použitého systému. Z tohoto důvodu je v současné době velkou výzvou vývoj přesných systémů pro měření náklonů při co nejnižší ceně.
Tento článek popisuje precizní systém pro měření úhlů náklonu a současně i pro měření kurzu. Systém se skládá z dvouosého analogového inklinometru HCA528T (Rion Technology) s proudovým výstupem a tříosým digitálním kompasem HMC5883L (Honeywell). Dvouosý senzor je použitý pro měření úhlů náklonů, HMC5883L je použitý pro určení kurzu, který společně se znalostí GPS pozice slouží pro dodatečné korekce vedoucí ke zvýšení přesnosti. V tomto článku popisujeme hardwarovou realizaci měřicího systému, zpracování dat a výslednou analýzu přesnosti určení náklonu.
Using Carrier-Phase Measurements of GPS Signals and RTK in Enhanced Positioning
MDS 2015 - Měření, diagnostika, spolehlivost palubních soustav letadel. Brno: Univerzita obrany, Fakulta vojenských technologií, 2015, pp. 194-203. ISBN 978-80-7231-434-8. Available from: http://www.unob.cz/fvt/struktura/k206/Stranky/MDS_PSL_Aktualni.aspx
GPS or, generally, GNSS based navigation is nowadays a common way to determine position, velocity, and time. The accuracy of such quantities strongly depends on a receiver and connected antenna. This paper deals with just a customer-grade receivers and antennae, namely with a uBlox NEO-6P and a Taoglas A.40.A.301111. This kind of receiver provides a 50 channel tracking capability on the GPS L1 frequency with C/A code and SBAS corrections. The accuracy of such a receiver is about 2.5 m (CEP) without corrections and with SBAS corrections it reaches about 2.0 m (CEP). Nevertheless, when a precise mode is switched on with SBAS corrections the accuracy can go down to less than 1.0 m (CEP). The contribution of this paper lies then in studying the accuracy of the positioning capability with such a receiver and antenna under different modes of operation. Enhanced performance is further reached by u usage of RTK (Real-Time Kinematic) capability of GPS which can provide cm-level accuracy even with a customer-grade means. RTK-GPS positioning relies on carrier-phase measurements of GPS signals and as such the receiver ought to provide raw binary data messages. RTK-GPS has been originally used in applications like geodetic survey; however, applications have recently expanded widely for instance to mobile mapping system, precise vehicles navigation, construction machine control, and precision agriculture. The study of the positioning accuracy is in the paper supported by in-field experiments.
Proceedings of 2014 PEGASUS-AIAA Student Conference. Praha: České vysoké učení technické v Praze, 2014, ISBN 978-80-01-05459-8. Available from: http://measure.feld.cvut.cz/groups/lis/StudentConference.php
This paper introduces the development of two Inertial Navigation Systems (INS) with different performances . First one, a tactical grade INS uses accurate inertial sensors, such as fiber optic gyroscopes DSP-3100 (KVH) and quartz accelerometers INN-204 (Innalabs). Hence, the task lies in its development and realization of the hardware part, and design and implementation of the algorithms needed for attitude and position determination, that do not rely on other sensor aiding for a short period of time. For this purpose, it is necessary to implement complex navigation equations without any simplifications, which allow getting close to accuracy of precise and expensive industrial navigation solutions. The second INS uses a low-cost inertial measurement unit MPU-9150 (InvenSense).
Modular Navigation System for Unmanned Aerial Vehicles
This paper describes a modular navigation system for precise attitude (pitch, roll, and yaw angles) and position determination. The system consists of an inertial measurement unit, GPS receiver, magnetometer, electrolytic tilt sensors, and pressure sensors. Raw data from all sensors were compensated for deterministic errors, pre-processed, and used for attitude and position determination, which was done onboard an unmanned aerial vehicle. The data were also stored for post-processing. In both real-time and offline methods the evaluation of navigation performance was based on Kalman filtering algorithms. The navigation system was tested using the UAV Bellanca Super Decathlon XXL. The accuracy of the evaluation as well as the performance was evaluated with respect to a precise multi-antenna GPS system.
Analyses of Electronic Inclinometer Data for Tri-axial Accelerometer's Initial Alignment
This paper deals with the usage of a dual-axis electronic inclinometer EZ-TILT-2000-008 to improve an initial alignment of a tri-axial accelerometer, which forms a part of the inertial measurement unit ADIS16405. There were performed several measurements under various initial conditions with the usage of a precise Rotational-Tilt Platform as a reference. Based on measured data the alignment procedure accuracy, null repeatability, stability of initial null angle, hysteresis, and cross-axis dependence were analyzed and the results of these analyses are presented.
Analyses of Triaxial Accelerometer Calibration Algorithms
This paper describes three tri-axial accelerometer calibration algorithms using mathematical model of nine parameters and the fact that the sum of sensed acceleration should be always equal to gravity vector under stationary conditions. The advantage of proposed algorithms is that the process does not require precise platform or special calibration equipment. The sensor error model (SEM) of tri-axial accelerometer consists of three scale-factor errors, three non-orthogonality angles, and three offsets. Three different algorithms were tested - Levenberg-Marquardt and Thin-Shell algorithm, and algorithm based on Matlab function fminunc. The proposed calibration process and its algorithms were experimentally verified on five accelerometers. We performed various analyses of proposed algorithms and proved that the proposed algorithms were capable to estimate the parameters of SEM without a need of precise equipment usage, which was the main aim of our investigation.
Comparison of Electrolytic Tilt Modules for Attitude Correction
In this paper there are analyzed and compared performances of different electrolytic tilt
modules (ETMs) from static and dynamic characteristics point of view. For a correct
determination of attitude (roll and pitch angles) evaluated from angular rates by integration,
it is generally required to have attitude compensation sources which limit unbound error
in this evaluation process and thus they play a key role for a proper function of navigation
systems. We analyzed five ETMs with different electrolyte viscosity: EZ-TILT-2000-045
with standard viscosity and with the viscosity of 50% higher (EZ-TILT-2000-008),
EZ-TILT-2000-045 with viscosity of 15% and 30% higher than the standard (all types from
Advanced Orientation Systems Inc.), and Micro 50-D70 with standard electrolyte viscosity
from Spectron Glass and Electronics Inc. The transfer characteristics, hysteresis and settling
time on fast angle changes, were measured and analyzed and the results will be presented.
Improvement of Electronic Compass Accuracy Based on Magnetometer and Accelerometer Calibration
This paper describes the process used for an electronic compass compensation according to accelerometer based tilt evaluation. Tilt angles have to be estimated first for sensed magnetic vector components to be aligned and horizontal components evaluated. Therefore the precision of accelerometer based tilt angles plays a key role in this whole process as well as the magnetometer characteristics. Hence accelerometers plus magnetometers have to be calibrated to improve the accuracy of a tilt and an azimuth angle evaluation. The calibration uses Thin-shell method to determine sensor error models. Both the effect of calibration and precision of estimated error models have been observed and are presented. The electronic compass consisted of tri-axial magnetometer and tri-axial accelerometer contained in the Inertial Measurement Unit ADIS16405 from Analog Devices manufacturer.
Inertial Reference Unit in a Directional Gyro Mode of Operation
This paper deals with a cost effective inertial reference unit design providing both MEMS based navigation unit calibration means and an attitude and heading measurement system in a directional gyro mode of operation.
A main contribution of this paper is a novel design of such
a universal system not primary relying on a magnetometer (MAG) or GPS aiding. Generally, without this aiding Attitude and Heading Reference Systems (AHRSs) are not directionally stable. Also, having precise reference in a calibration process is crucial and in most cases the solution is expensive. We thus replaced an expensive solution of both applications with the cost effective one suiting mentioned purposes using only one single axis fiber optic gyro supported by an inertial MEMS based aiding system. We also proposed a calibration procedure and blended solution to provide both stable and reliable navigation data with accuracy better than 5 deg/h specified by the TSO-C5e.
Modular Navigation System for Unmanned Aerial Vehicles - Flight Data Monitoring and Recording
Precise attitude and position determination is one of main tasks in a navigation procedure.
Nowadays, there is a possibility to navigate military Unmanned Aerial Vehicles (UAVs)
accurately. But such a precise navigation system based on inertial sensors is not only
expensive, but also large-sized and it has high power consumption for the proper
functionality. Therefore, in the case of small UAV navigation many research teams all around
the world evaluate lightweight, low-cost solution based on inertial sensors aided by
complementary sensors together with advance algorithms and adaptive filtering methods.
This paper describes such an inertial-based modular navigation system with aiding systems
(GPS, tilt sensors, magnetometer, and pressure sensors) and its capability to transmit and
store flight data.
Azimuth Determination Based on Magnetometer Measurements
MDS - Měření, diagnostika, spolehlivost palubních soustav letadel 2011 - Sborník příspěvků z 11.mezinárodní vědecké konference. Brno: Univerzita obrany, Fakulta vojenských technologií, 2011, pp. 11-17. ISBN 978-80-7231-828-5.
The paper describes the methodology of an azimuth evaluation based on Earth magnetic field measurements. For this purpose tri-axial fluxgate magnetometer were used. Fluxgate magnetometers are the most precise sensors in comparison with magnetoresistive or AMR alternatives. They can be found with both analogue and digital outputs. The described methodology relies on analogue sensors output processing which included the designs of a pass-band filter and an output voltage phase detector. For the design analyses we compared performances of the designed filter and FFT.
Development of Platform for Measurement and Signal Processing of Navigation and Aerometric Data
POSTER 2011 - 15th International Student Conference on Electrical Engineering. Praha: České vysoké učení technické v Praze, Fakulta elektrotechnická, 2011, pp. 1-5. ISBN 978-80-01-04806-1. Available from: http://radio.feld.cvut.cz/conf/poster2011/
Attractive education and quality research results based on real-world conditions depend on the equipment, instrumentation and sensors which are available for students' bachelor thesis, diploma thesis, dissertations, individual and team projects. The main aim of this paper is the realization of mobile aeronautical platform for measurement of sensors data in real-world conditions; mainly navigation data (GPS, magnetometer, INS) and aerometric data (static and dynamic pressures). This platform allows evaluation of the signal processing methods using real measured data, and evaluation of devices developed by bachelor, master, and postgraduate students in real-world conditions. This mobile aeronautical platform is used for real data acquisition, innovation of laboratory courses curriculum, promotion of the project results and importance of modern data processing in aviation.
Improvement of Electronic Compass Accuracy Based on Magnetometer and Accelerometer Calibration
This paper describes the improvement of Electronic Compass (EC) accuracy using mathematical algorithm Thin-Shell for triaxial sensor calibration. The EC consists of triaxial magnetometer and accelerometer contained in Inertial Measurement Unit (IMU) ADIS16405 (Analog Devices). The EC algorithm, sensor error models (SEMs), SEM estimation, and the influence of applied SEMs on EC accuracy will be presented and discussed.
Laboratorní systém pro ilustraci principu stabilizace kosmických prostředků
MDS - Měření, diagnostika, spolehlivost palubních soustav letadel 2011 - Sborník příspěvků z 11.mezinárodní vědecké konference. Brno: Univerzita obrany, Fakulta vojenských technologií, 2011. pp. 145-164. ISBN 978-80-7231-828-5.
Tento článek popisuje konstrukci a princip činnosti zařízení, které jednoduchým způsobem ilustruje funkci stabilizace hmotného tělesa v prostoru na základě změny momentu vyvozovaného reakčním kolem - gyroskopem. Tento princip je možné použít i v gravitačním poli Země na objektu zavěšeném na struně. Jedná se o stabilizaci v jedné ose. Článek popisuje konstrukci zařízení, jednotlivých elektronických modulů, jeho funkci a použití jako laboratorní úlohy za účelem rozvoje zájmu studentů o kosmické technologie.
Modular System for Attitude and Position Determination
Precise attitude and position determination is one of main tasks in navigation procedure. Nowadays, there is possibility to navigate military Unmanned Aerial System (UAS) accurately also in case of its flight on other side of the Earth. But such precise navigation system based on inertial sensors (angular rate sensors and accelerometers) is not only expensive, but also large-sized and it has high power consumption for proper functionality. Costs, power consumption and size together with area restriction limit usage of such system especially in military application. This paper describes such a modular system based on low-cost inertial sensors with aiding sensors (distance sensors, pressure sensors, and tilt sensors). Described modular system finds its utilization not only as navigation system of small UAS, but also as part of intelligent metal detector equipped as added discrimination ability or in robot and indoor navigation.
Modular System for Attitude and Position Estimation
Estimation of position and attitude of the object in a certain area has wide applicability in many industrial fields and in light of development it is a crucial part of aeronautics, astronautics, and also robotics. Nowadays, there already exist technologies for precise determination of the position and attitude with the accuracy of 0.01 m in position and 0.01 deg. in attitude. Sensors used for precise positioning with requirements of long time functionality are very expensive, big-sized, and have high power consumption. Based on these aspects these sensors are unsuitable for mobile application. Furthermore, many sensors are area restricted and so for non-army application unavailable. Therefore, there is an effort of many research centers to develop methods to reach sufficient precision with readily available means. This effort requires an innovative approach in the field of both complex algorithms for data acquisition and the composition of sensors.
Practical Usage of Allan Variance in Inertial Sensor Parameters Estimation and Modeling
This paper shows a time-domain approach to sensor parameters estimation via Allan VARiance analysis (AVAR). The aim of this paper is not to describe AVAR and its modifications in details, but to show its applicability and suitability for the estimation of inertial sensors parameters and consecutive usage of these parameters in sensors modeling. To prove the suitability of proposed sensor models there was used a composed model for Kalman filter which provided corrected angular rates and accelerations for attitude evaluation.
Sensors and Data Processing Methods Used in Navigation Systems
Navigation systems of civil aircrafts are used for vertical and horizontal situation estimation and indication. They provide information about position, velocity, and orientation of the aircraft in a reference framework. They commonly consist of Inertial Measurement Unit (IMU) and computation units. The IMU primary uses inertial sensors, such as accelerometers and angular rate sensors/gyros, which are sometimes supplemented by magnetometers. The vertical situation can be described by altitude and two Euler angles corresponding to roll and pitch. The third angle (yaw) defines the heading and with position it forms the information about the horizontal situation. The navigation systems can be divided into two groups such as Attitude and Heading Reference Systems (AHRS) and Inertial Navigation Systems (INSs). The accuracy of estimated Euler angles also affects the precision of estimated position gotten through two consecutive integrations of acceleration and velocity.
Small Satellite Systems Control for University Curriculum
This article describes an electro-mechanical laboratory model of a spacecraft dedicated to demonstrate selected principles currently used in space with special intent to attract people back to space technologies. The model represents part of a microsatellite that allows its stabilisation and controlled movement in one axis. With this microsatellite we are able to demonstrate: microsatellite stabilisation with help of reaction wheels, inertial measurement unit function with coordinate system transformations, data acquisition and wireless data transfer, control loop design, start tracker functionalities and algorithm development.
MDS - Měření, diagnostika, spolehlivost palubních soustav letadel 2011 - Sborník příspěvků z 11.mezinárodní vědecké konference. Brno: Univerzita obrany, Fakulta vojenských technologií, 2011, pp. 213-225. ISBN 978-80-7231-828-5. Available from: http://www.vojenskaskola.cz/skola/uo/fvt/struktura/k206/Stranky/MDS_PSL_2011_CZ.aspx
This paper describes a measurement system capable to test a vibration influence on navigation devices. The system consists of a signal generator, vibratory equipment, on which a reference sensor can be placed, and a PC. The system works with real flight acceleration data. A main idea of the system is to use original flight acceleration information from intervals with constant engine RPM, approximate it, and generate in the laboratory conditions. The approximation uses four strongest harmonics of the original acceleration evaluated by FFT analysis. The system for vibration tests is fully automatic and feed-forward, which allows analyze acceleration data, choose the acceleration magnitudes and frequencies based on FFT, and generate the flight vibration in the laboratory. The system enables automatic calibration of vibratory table. The system, the user interface, and the comparison between user selected data and measured data will be further presented and discussed.
Temperature Effects and Non-linearity Corrections of Pressure Sensors
This paper presents a method of correction temperature effects affecting pressure sensors used mainly for dynamic and static pressure measurements within air-data systems based on low-cost sensors. The principle uses an isochoric process (or a constantvolume
process) during which a thermodynamic changes cause pressure shift within the constant volume of a closed system. The closed system is presented here as a volume formed
from a blinded inlet of a pressure sensor whose output is used for measurement sensor output corrections. The article presents all the equations used for the temperature effects and nonlinearity corrections. The overall method of the environmental effects correction is presented on a test system and a prototype of an Air-Data Computer.
Usage of Electrolytic Tilt Sensor for Initial Alignment of Tri-axial Accelerometer
A precise initial alignment in navigation strongly depends on the accuracy of the initial static acceleration measurements and consecutive attitude evaluation. Therefore, the evaluation is affected by accelerometers' imperfection, which is in this case the initial bias. This paper deals with a usage of a dual-axis electrolytic tilt sensor EZ-TILT-2000-008 to improve the initial alignment done by accelerometers, which form a part of inertial measurement unit ADIS16405. There were performed several measurements under various initial conditions with a usage of a precise Rotational-Tilt Platform as a reference. Based on measured data alignment procedure accuracy, null repeatability, and stability of initial null angle were analyzed. The electrolytic tilt sensor can be used to estimate accelerometer's biases and thus it improves the accuracy of initial alignment, computed pitch and roll angles respectively.
Algorithms for Heading Determination using Inertial Sensors
This paper describes the results of comparison analysis regarding three algorithms for heading determination using low-cost inertial sensors: the stand-alone strapdown approach, magnetometer aiding approach, and strapdown approach with errors modelled, estimated and compensated using Kalman filtering. Experimental testing with precise rotational tilt platform was performed. Error analysis was carried out to qualitatively evaluate the best approach intended for implementation into unmanned aerial systems for navigation purposes.
The calibration of angular rate sensors is a complex task, mainly due to the crucial role of defining the reference during the calibration process. Low-cost angular rate sensors, such as MEMS, cannot be used without calibration even in basic precision desired applications. The goal of calibration involves the estimation of the angular rate sensor deterministic error model. In this paper there is proposed a calibration process that does not require either a precise rotational platform or a precise positioning or other reference. The algorithm of tri-axial angular rate sensor calibration is based on a special procedure of angular rate measuring under different setting conditions, Cholesky decomposition, and LU factorization in the angle domain. This calibration algorithm was evaluated using two AHRS units 3DM-GX2 and AHRS M3. The calibration process and the deterministic sensor error analyses of angular rate sensors are presented.
Integration of Low-cost Inertial Navigation Unit with Secondary Navigation Systems
This paper concerns the development of a system that consists of a low-cost inertial
navigation unit and the 3-axial magnetometer, which will be used as a secondary navigation
system. The development includes measuring and testing of inertial sensors and a magnetometer, and the calibration of navigation sensors used for the following data fusion via
As a primary system for integration the Inertial Navigation System (INS) will be used.
The INS consists of 3-axial accelerometer and 3-axial angular rate sensor. Tri-axial
magnetometer will be used as the secondary system. All of these sensor outputs are disturbed
by errors which are a decisive factor for their implementation and verification of their
performance. The deterministic sensor error analyses of accelerometers, angular rate
sensors, and magnetometers are presented.
Introducing Students to Aerospace Board Information Systems Using an Embedded Graphics System Simulator
A graduate-level engineering course in airborne sensor and control systems taught at the Czech Technical University in Prague under the title Board Information Systems takes a novel systematic and comprehensive approach to teaching airborne digital avionics systems, together with system certification and life-cycle operations. The course brings together materials from various sources to cover practical aspects of avionics systems ranging from design, prototyping, testing, certification and production through to maintenance. It prepares students to deal with a wide range of the type of real-world problems that they will meet in thein professional careers. This is a required course offered in the 10th semester as a part of the study programme in Airborne Information and Control Instrumentation (AICI) by the Department of Measurement. The course was redesigned with new lecture content, practical exercises and field trips. The course evaluation survey results from 2008 and 2009.
Error Analyses of Attitude and Heading Reference Systems
This paper describes the results of error analyses of two low-cost Attitude and Heading Reference Systems (AHRS). These error analyses concern both random sensor errors identified by Allan variance method and deterministic errors estimated during a calibration procedure. The calibration procedure is based on the Levenberg-Marquardt algorithm used to solve non-linear least squares estimation problem. The main contribution of this paper is to present data necessary for further inertial sensors signal processing by means of Kalman filtering.
Flight Attitude Track Reconstruction Using Two AHRS Units under Laboratory Conditions
The paper describes a performance analysis of two low-cost AHRS (Attitude and Heading Reference Systems), calibration procedures, and the verification of INS (Inertial Navigation System) mechanization algorithm using dedicated automatic measurement system based on a real-time flight simulation. The measurement system included the flight simulation software FlightGear (FG) that offered a wide range of aircraft dynamics and track simulation possibilities. The FG output data were converted into the form suitable for a servocontrolled Rotational-Tilt Platform (RoTiP) which provided corresponding motion for two AHRS units mounted on it and reference information from optical sensors. The output data of the AHRS units were collected, processed and evaluated to verify the units accuracy and reliability. The metodology and results based on the performance analyses are presented.
Sensors of Air Data Computers - Usability and Environmental Effects
This paper compares static pressure sensors suitable for aircraft air data systems. Characteristics of selected sensors influenced by environmental effects are compared with regards to their price. The group of sensors was chosen in order to cover a wide range of sensor samples available on the market. The article compares characteristics of sensors manufactured by Freescale, the MPX series, Memscap SP82, Intersema MS5534, and samples from SensorTechnics and Honeywell. The measurement setup is also described in the article. Digital modules connected through the CAN bus and GPIB measurement instruments were used for data acquisition. The data was sampled through Matlab Data Acquisition System extended by our own CAN Aerospace Toolbox that is being developed at CTU in Prague. The article finally compares all tested sensors and presents possible calibration methods, in which temperature effects and non-linearity were taken into consideration.
Verification of IEEE1588 Time Synchronization in NASA Agate Data Bus Standard
Time synchronization quality of measurement devices plays critical role under necessity of precise data sampling, e.g. for usage of the Kirchhoff Current Law. This article proposes new arrangement of aircraft inertial sensors, that are spread over an airplane construction and needs to be time synchronized. Generally a single signal wire is used for time synchronization for local networks or they rely on their internal timers. The IEEE standardized a time synchronization algorithm designed for packet network such Ethernet. In this paper we propose usage of IEEE1588 over the Agate data bus based on the CAN bus in order to synchronize group of inertial sensors. In addition precision of the time synchronization is measured and compared.
Advanced Implementations Techniques in Kalman Filtering
This paper deals with advanced implementation techniques in Kalman filtering regarding the computational complexity and filter numerical stability. Implementation techniques were validated using a conventional Kalman Filter that was developed on real data from Servo Hitec HS-5955TG. Servo's target application is as actuator in unmanned aerial vehicle (UAV) Manta, currently under prototype development by VTUL. Aim of this project was to enhance the servo's self validating process by Kalman Filter in a way to meet the DO178 development guides. The actual servo model was developed using response test measurements and load measurements followed by autoregressive modelling.
Over the last decades there was a remarkable increase in demand for low-cost inertial navigation systems to serve as car navigation, personal navigation or navigation for unmanned aerial vehicles. The technological advance in performance of micro-electro-mechanical sensors (MEMS) is the reason. However, low-cost inertial navigation systems do still experience a large position and attitude errors giving the opportunity for additional engineering insight. This paper deals with improved system performance of a low-cost attitude and heading reference system (AHRS). The improvement was achieved by de-noising rough inertial data using a wavelet multi-resolution analysis (WMRA) applied on real data acquired from a car navigation field test.
Over the last decades there was a remarkable increase in demand for low-cost inertial navigation systems to serve as a car navigation, personal navigation or navigation for unmanned aerial vehicles. A technological advance in the performance of micro-electro-mechanical sensors (MEMS) is the reason. However, low-cost inertial navigation systems do still experience a large position and attitude errors giving the opportunity for additional engineering insight. This paper deals with a method for improving the performance of a low-cost Attitude and Heading Reference System (AHRS). The improvement was achieved by de-noising rough inertial data using a wavelet multi-resolution analysis (WMRA) applied on real data acquired from a car navigation field test.
Levenberg-Marquardt Algorithm for Accelerometers Calibration
Sborník z 8. mezinárodní vědecké konference Měření, diagnostika a spolehlivost palubních soustav letadel. Brno: Univerzita obrany, Fakulta vojenských technologií, 2008. pp. 39-45. ISBN 978-80-7231-555-0.
This paper describes a method of tri-axial accelerometer calibration. The aim of this calibration is find the accelerometer error model: non-orthogonallities, scale factors and accelerometer bias. The Levenberg-Marquardt algorithm (LMA) is a proven method for such calibration. The LMA is an iterative procedure that locates the minimum of a non-linear function over a space of its parameters. In principle, the LMA interpolates between the results of Gauss-Newton Method (GNM) and the Method of Gradient Descent (MGD). The result of this calibration is the error model that is used for compensation of the above stated errors.
This article describes design of system for accurate measuring tilts. This system uses two dual axis electrolytic tilt sensors with different ranges which are used for measuring pitch and roll. The useable range for measuring angles of tilts is °20 degrees for the first electrolytic tilt sensor and °45 degrees for the second sensor. Measured data from sensors were processed in a computer and their deviations from right values were corrected. The cooperation of these sensors was mathematically solved by the Kalman filter.
Nowadays, systems for automatic measuring of tilt-angles are used in many technical applications eg testing and calibration of aircraft equipment, passenger boarding bridges etc. This paper describes the design and realization of such a system for accurate tilt-angles measuring. For this purpose two dual-axis electrolytic sensors with different ranges and dual-axis accelerometers were used. The measured data were processed in Matlab environment. Linearization of transfer characteristics by Lagrange interpolation and integration of these linearized data was performed by the means of Extended Kalman Filter (EKF) with appropriate shaping filters.
Turbulence Modelling for Attitude Evaluation Purposes
Sborník z 8. mezinárodní vědecké konference Měření, diagnostika a spolehlivost palubních soustav letadel. Brno: Univerzita obrany, Fakulta vojenských technologií, 2008. pp. 46-54. ISBN 978-80-7231-555-0.
This paper deals with modelling methods used to develop a suitable turbulence model for a conventional Kalman filter. The Kalman filter serves in this case as an estimator for aircraft attitude evaluation that is based on a new approach of gravitational acceleration sensing. Hence, the designed turbulence model was augmented with accelerometer noise models. These noise models were created according to power spectral density analysis of their output signals. The influence of turbulence on the accelerometer signal as well as the sensor bias and drift were successfully compensated to obtain the desired gravitational component of the acceleration. The signal was estimated with satisfactory precision and evaluated by the Kalman filter covariance analysis.