doc. Ing. Jan Roháč, Ph.D.

A common approach for nding the direction of ocean waves is to use the phase-time-path-differences (PTPDs) between a static array of various types of sensors mounted on either the sea surface or seabed. However, some practical drawbacks of such arrays are that they tend to be expensive, dicult to install, and xed in location. We show that the PTPD approach can be generalized to a portable shipboard array of spatially distributed sensors rendering it more practical. In this respect, we derive a nonlinear PTPD model for shipboard sensor arrays and prove that the wave direction and wave number can be resolved from a minimum of three noncollinear sensors using observability analysis. Moreover, based on our PTPD model, we propose an unscented Kalman lter algorithm for online estimation of the wave direction and wave number, which offers a convenient framework for adding multiple measurements and incorporating uncertainties. Our experimental results from model basin testing with a model ship equipped with several inertial measurement units (IMUs) conrm that the wave direction and wave number can be estimated from the wave-induced motions of a surface vessel with a minimum of three noncollinear IMUs. In this study, we consider parameter estimation for regular waves and assume a dynamically positioned surface vessel with small roll and pitch angles.

Nowadays, one of the most promising areas in the motor industry is the production of BLDC motors, which are used in a wide range of applications and products—from power tools to electrical vehicles. The windings of BLDC motors are connected according to the Delta or Star circuits. However, such circuits (Delta or Star) do not allow dynamically changing the parameters of the BLDC motor during operation and thus reducing the overall motor efficiency. This paper deals with and proposes an electronic switch of the BLDC motor windings, which brings an advantage in having a capability of dynamically switching the windings during operation and thus increasing the efficiency of the BLDC motor performance.

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.

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.

With advanced control, estimation and simulation requirements in unmanned aerial systems comes the need for sophisticated aerodynamic models. This paper reviews two common means for establishing such models; numerical design tools and wind tunnel testing, by presenting strengths and potential problems, in a ”lessons learned”-manner. As a case study throughout the paper, a six degrees-of-freedom aerodynamic model of the Skywalker X8 fixed-wing unmanned aerial vehicle is presented.

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.

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.

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.

ELEKTRON I je reaktivní nosič určený pro výuku aerodynamiky a ověřování elektroniky, měřících a řídících algoritmů na létajících prostředcích s vysokou dynamikou pohybu.

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.

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.

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.

MEMS (micro-electro-mechanical system)-based inertial sensors, i.e., accelerometers and angular rate sensors, are commonly used as a cost-effective solution for the purposes of navigation in a broad spectrum of terrestrial and aerospace applications. These tri-axial inertial sensors form an inertial measurement unit (IMU), which is a core unit of navigation systems. Even if MEMS sensors have an advantage in their size, cost, weight and power consumption, they suffer from bias instability, noisy output and insufficient resolution. Furthermore, the sensor’s behavior can be significantly affected by strong vibration when it operates in harsh environments. All of these constitute conditions require treatment through data processing. As long as the navigation solution is primarily based on using only inertial data, this paper proposes a novel concept in adaptive data pre-processing by using a variable bandwidth filtering. This approach utilizes sinusoidal estimation to continuously adapt the filtering bandwidth of the accelerometer’s data in order to reduce the effects of vibration and sensor noise before attitude estimation is processed. Low frequency vibration generally limits the conditions under which the accelerometers can be used to aid the attitude estimation process, which is primarily based on angular rate data and, thus, decreases its accuracy. In contrast, the proposed pre-processing technique enables using accelerometers as an aiding source by effective data smoothing, even when they are affected by low frequency vibration. Verification of the proposed concept is performed on simulation and real-flight data obtained on an ultra-light aircraft. The results of both types of experiments confirm the suitability of the concept for inertial data pre-processing.

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.

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.

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.

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.

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).

In this paper two novel modifications of Weighted Least Square Method (WLSM) of frequency estimation suitable for evaluation of rapid changes of frequency occurring in resonance sensors are introduced and experimentally verified. The efficiency of the WLSM methods is compared to the nano-counting approach representing a substantial improvement of well-known start-stop methods of frequency measurement and estimation.

The paper is dealing with an environmental strong-vibration impact on inertial sensors' output. In our case we measured data on the ultra-light aircraft ATEC 321, which did not have damped cockpit panel, and we recorded the data for post-processing. The main contribution of this paper is in frequency spectrum analyses of measured data, their validation, and filtering to ensure acceptable behavior of navigation systems relying on these data. The data suffered from strong vibration, which had big impact and thus it had to be removed before estimation of navigation parameters was performed. One example of navigation systems is an artificial horizon. Generally, it performs the aircraft attitude estimation just based on accelerometers and angular rate sensors data, and therefore the correctness and efficiency of data filtering as well as consecutive data processing plays a key role.

Humanitarian de-mining missions are activities in which an operator safety and time consumption are key issues. To increase a discrimination ability of ATMID metal detector, which we have been using, we extended the capability of the detector with mounting Inertial Measurement Unit (IMU) supplemented by two optical distance sensors on the detector head. That enabled us to perform dead reckoning based on accelerations and angular rates measured by IMU in all three axes. Optical distance sensors have been used for compensation purposes and an initial distance measurement. Our main aim was to interconnect magnetic imprint sensed by the detector with precise localization of its head, which led to imprint size estimation as well as its position. Due to low-cost MEMS (Micro-Electro-Mechanical System) based IMU implementation we have had to deal with unstable dead reckoning outcomes. For this reason we used our designed Complex Magnetic Markers (CMMs) which demarked a searched area plus provided us with precise positioning at its both edges. The main contribution of this paper is in the study and identification of CMM magnetic imprints characteristics and their differences related to various aspects of CMM usage during de-mining procedure and its conditions. The characteristics of CMMs have been studied and analyzed according to several laboratory experiments and results are presented.

The paper is focused on the overview of inertial sensors supplemented by their development, plus it provides advanced algorithms and methodology concerning navigation systems predominantly using MEMS based inertial sensors and aiding measuring systems. It describes a complex design and development of aided navigation systems. Thus, it deals with principles of navigation, methods of system parameters estimation, and signal/data processing. The paper presents particular solutions and their direct impact on the system performance and its accuracy.

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.

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.

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.

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.

This paper describes a novel type of metal markers for eddy current metal detection systems using precise positioning information. The new design for metal markers which are compounded by an ordered array of metal plates with different magnetic parameters has three fundamental advantages: 1. the markers are sensed directly by the metal detector, and no additional hardware is required; 2. the signatures are sharp; 3. not only the position but also the speed of the detector head can be evaluated. In the case of a stand-alone inertial navigation system for evaluating the position of the detector, the precision would be low due to the sensor noise and its integration. However, knowledge of the relative positions and potentially of the detector head speed over the markers can be used as auxiliary information, and so the eddy-current mapping system will be capable of determining the size of the magnetic imprint of a detected metal object and its position relative to the markers. This increases the reliability of the object discrimination during humanitarian demining, and decreases the numbers of false alarms, which nowadays constitute 99.9% of all alarms emitted by an ordinary mine detector.

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.

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.

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.

An artificial horizon is a basic instrument for attitude indication. In case of small aircrafts this kind of instrument generally uses inertial sensors, i.e. accelerometers and angular rate sensors, manufactured with MEMS technology. Even if it has many advantages, such as low price, size, and low power consumption, it also has parameters which hardly satisfy requirements for precise navigation purposes. Without means of attitude corrections the system would have unbound growing error. This paper presents a method which uses data from angular rate sensors fused with accelerometers and thus it provides correction feedback to constrain the growing error in indicated attitude. Convectional data fusion in navigation applications uses Kalman filtering approach. In case of very noisy environment caused by vibrations there is necessary to apply low-pass prefiltering with very low cut-off frequency. Therefore, Kalman filtering is in this case not necessary.

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.

Data processing of low-cost inertial sensors has been and still is a big issue for many engineers. Inertial sensors compose a measurement unit used as the basis of navigation systems. These systems can be found almost everywhere; it does not matter if it is in pharmaceutics, robotics, automotive industry, aerospace etc. However, there is always a need to specify under which conditions the systems are supposed to operate. This paper deals with the processing of inertial sensor data measured in an environment with strong vibrations on the ultra-light aircraft ATEC 321. It was a great challenge to process the data in such a way as to ensure the acceptable behavior of the artificial horizon system. Because the system should rely only on acceleration and angular rate sensing, the correctness and efficiency of data filtering as well as consecutive data processing play a key role. Results regarding data analyses and comparisons of different approaches are presented.

The ability to differentiate between metal garbage and unexploded ordnance is the key point of the newest metal detectors development. This paper describes the methodology of the differentiation which would improve currently used mine detector performance. The ability relies on the metal detector output phase and amplitude evaluation.

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.

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.

The paper is focused on a multi-functional wide-field star tracker (WFST) idea description and the description of the current state-of-the-art in this field. The idea comes from the proposal handed in to ESA at the beginning of 2011. Star trackers (STs) usually have more than one object-lens with small Field-of-View. They provide very precise information about the attitude in space according to consecutive evaluation of star positions. Our idea of WFST will combine functions of several instruments together, such those as ST, horizon sensor, and all-sky photometry camera. WFST will use fish-eye lens. In the present technology there is not any similar product on market. Nowadays, spacecrafts have to carry more instruments for mentioned applications, which increases weight and thus decreases weight intended for a payload.

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.

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.

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.

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.

The paper describes use of a differential air pressure sensor in an aerometric aircraft system. The differential sensor is operated by a pressure switch controlled by an electric signal. This lay-out is used for altitude difference measurement corresponding to a pressure difference range of the used sensor. The atmosphere temperature is measured simultaneously with the pressure difference. The measured altitude is then given as a sum of individual altitude sectors corresponding to switch-over of the pressure switch. This method of altitude measurement is suitable for small altitudes so that the resulting error given as a sum of errors by measurements of individual sectors is small. An example is use of an unmanned aerial vehicle (UAV) when the altitude difference from a starting point does not exceed 1 000 m. The difference switch with pressure switch-over together with time interval measurement may be also used for vertical speed measurement.

Tento článek popisuje možné využití inerciálních senzorů při humanitární odminování. Jako zdroj dat pro algoritmus mechanizace slouží levná inerciální měřicí jednotka (IMU) obsahující tříosý senzor úhlových rychlostí spolu s tříosým senzorem zrychlení. Na rozdíl od klasického využití inerciálních senzorů pro navigaci letadel nebo mobilních robotů je v tomto článku prezentováno využití v kombinaci s profesionálním detektorem kovů. Takovéto využití poskytne nejen informaci o orientaci detekční hlavy detektoru kovů, ale v kombinaci s doplňkovými senzory poslouží jako informační zdroj definující aktuální pozici v průběhu procesu odminování. Informace o pozici v součinnosti se signálem z detektoru dále může poskytnout zásadní informaci pro určení detekovaného předmětu.

Introduction of principles of navigation and suitable sensors; applicability inertial sensors, MEMS introduction; sensor parameters estimation methods; INS aiding systems and principles of data fusion

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.

This paper deals with the GPS usage for the attitude determination. GPS system is widely used as the source of position, velocity, and time information; however there is also other possibility of its usage which is the attitude determination capability. Several possible methods to determine GPS based attitude are presented after an introduction. The method explanation goes from simplest one with an easy usage of independent receivers' position calculation, followed by a pseudorange differential positioning, and carrier phase measurement ends up the list. The last method is closely described with an appropriate hardware equipment. The experimental measurement results are also presented and a potential usage of the method determining the attitude is mentioned.

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 Kalman Filter. 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.

A signal processing plays a crucial role in each field of engineering. In case of navigation, where there is very popular to use MEMS inertial sensors in low-cost applications, the adaptive signal processing, for instance Kalman filtering (KF), is a necessity to ensure even the basic functionality. Standard navigational data include the position, velocity, and attitude and are based on acceleration and angular rate measuring in 3D orthogonal frame. Measured quantities have to be preprocessed and denoised before the mechanization of navigational equations and KF take place. This denoising provides smaller data variance and increases the precision of estimated position, velocity, and attitude. This paper deals with Allan variance analysis and its applicability in denoising procedures. An overview of applied method and its results are presented.

Distinguishing of mines from scrap metal is a difficult task that provides challenge when seeking an ultimate solution. An eddy-current imaging feature added to standard handheld metal detector is an option for such discrimination. Our metal detector was enhanced by an inertial measurement unit aided by velocity information, measured by optic flow sensor. It lead to further improvement of the proposed procedure by means of position and orientation tracking. The achieved accuracy of mine signal localization is 1 cm in 1x1m scanning area.

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.

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.

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.

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 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.

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.

Angular rate sensing is one of basic functions of Inertial Measurement Units (IMU) that are used in Inertial Navigation Systems (INS). These systems can be generally used in any king of transportation where navigation functions are needed, even in aeronautical field. These systems, sensors included, have recorded significant progress since the beginning of 20th century when the first gyrocompass was patented by Dr. Anschutz (1904). Since that time the technology has changed a lot and systems performance has begun to be much more precise and reliable. Thus this paper deals with a description of new kind of angular rate sensors and gyroscopes and their usage in aircraft attitude evaluation. Measured performance of some angular rate sensors will be presented.

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.

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.

There exist many projects and articles dealing with inertial navigation units using low-cost sensors. However, they mostly establish that low-cost sensors are not suitable to use in inertial navigation units in a case of no other data source presence. A main reason is of course sensors' drift, sensitivity and their noise. The inertial navigation units generally use three accelerometers and three angular rate sensors orientated into the aircraft framework to provide navigational data. Of course, there are many techniques in sensing and in evaluation of angular rates and acceleration, but mentioned principle is the basic one. The paper concerns a technique that utilizes different configuration of accelerometers sensing axes to enable attitude evaluation based on acceleration and not on angular rates integration. The paper also deals with a design of shaping filters for a sensor modeling made based on Power Spectral Density and Fast Fourier Transformation methods.

The attitude represents basic navigational data that determine the relationship between an aircraft framework and a reference Earth framework. For the attitude evaluation there is commonly used inertial measurement unit. In case of usage low-cost sensors, the evaluation is affected by error that is caused by sensor's drift, noise and resolution. The error due to the used integration is openended, which is a main disadvantage. One of possible method for error restriction in attitude evaluation is a usage of GPS satellite navigation, GPS receivers respectively. The advantage is that the inaccuracy is not open-ended. However, its output data can be influenced by not only aircraft motion itself but also by actual operational conditions. Even if those disadvantages exist, GPS system can be useful means to increase precision of low-cost inertial navigation unit by data fusion. This paper, therefore, deals with attitude evaluation based on GPS data, its methods, and its precision.

This article describes design of an aircraft engine control system which is based on a distributed network of sensors and actuators. The IEEE1451 standard is described and used for sensors and actuators interconnection. The IEEE1451 implementations of a sample senor and an actuator device are also described. Time differences in the sample data acquisition are described in details.

This document concerns processing and data transfer of angular rate sensors signals. It should give the reader a background of angular rate sensors, describe how the signal processing and data transfer were solved. Main aim of this project was to design, realize and verify system that will find use for calibration of a three-axis system of angular rate sensors using Kalman filter. Nowadays, hand in hand with the progress on the field of electronic components it is easier to design and realize own measuring systems than it was in the past. Such a system is then a priceless tool for further laboratory work, because it suits well the desired application. Due to low price and availability of high-performance digital signal processors and other electronic components it was possible to create such a system.

Due to its universal estimation character the Kalman filter (KF) is a versatile mathematical tool usable almost in any area adherent to navigation in any way. A current trend in an inertial navigation uses KF for GPS/INS integration, i.e. for sensor outputs fusion, to obtain better estimation results and enhance the precision of the INS/GPS navigation. One of main influences on the precision and reliability of the GPS/INS system is the selection of subsystem-level sensors. Nowadays, cost of these sensors is the crucial issue and decisive factor for the desired application. Therefore, this article concerns low cost inertial sensors and suggests the methodology for sensor selection, modelling, evaluation and implementation into the Kalman filter design.

Current trend in aircraft navigation tends slowly but surely towards autonomous aircraft navigation system which would be no longer dependant on air traffic control center and ground navigation systems. Inertial navigation systems are in this case a solution for the future. To ensure requested precision and reliability inertial navigation system has to be based on precise and reliable data from accelerometers and angular rate sensors updated by corrections made by navigational computer. The question is if low-cost sensors supported by advanced filtration methods may be used for such purposes. A measurement of navigation system characteristics and an investigation of suitable calibration methods are the first step. To do so, it is firstly necessary to design and realize precise measuring system.

This article concerns the design and realization of a universal DSP board (including user interface for PC) for measuring low-cost angular rate sensors signals as well as for verificating and validating adaptive filtration algorithms. Adaptive filtration algorithms are used for enhancing the sensors parameters in order to increase their precision and hence enable their application in low cost strapdown inertial navigation systems. This paper deals with the application of Kalman filter on these sensors.

Příspěvek se zabývá popisem metody, která umožňuje měření úhlového zrychlení pomocí speciálně rozmístěných akcelerometrů na stěnách krychle. Takto měřené úhlové zrychlení je možno dále použít pro zpřesnění údajů o úhlových rychlostech pohybu tělesa, které jsou měřeny pomocí senzorů úhlových rychlostí.

The paper concerns a technique that utilizes different configuration of accelerometers sensing axes to enable attitude evaluation based on acceleration and also deals with the unit framework calibration that is used to increase a unit precision.

V současné době existuje mnoho projektů zabývajících se oblastí inerciální navigace, obzvlášť snižováním nákladů navigačních jednotek. Nicméně, při klasické konfiguraci inerciálních senzorů jsou tyto levné jednotky využívány jen jako doplňkový systém, který by sám osobě dlouhodobě nedosahoval požadovaných přesností. Tento fakt je způsoben využíváním levných variant senzorů. Tento příspěvek se zaměřuje na popis postupů kalibrace jednotky umělého horizontu, která i přesto, že využívá levné inerciální senzory, dosahuje dlouhodobé stability a požadovaných přesností v určování podélného sklonu a příčného náklonu.

V příspěvku je proveden rozbor parametrů tenzometrického a kapacitního diferenčního senzoru tlaku vzduchu pro jejich využití k měření kalibrované rychlosti letu letadla. Rozbor vychází z naměřených závislostí výstupních signálů na tlaku vzduchu s uvažováním teplotní závislosti, tlakové hystereze a dlouhodobé stability snímačů. Dále je popsána konstrukce rychloměru s kapacitním snímačem Vegabar 14. V závěru jsou uvedeny výsledky měření na realizovaném funkčním vzorku.

Obsahem sedmé kapitoly jsou primární snímače používané v navigaci.

The paper describes a method that enables a usage of low-cost inertial sensors, such as angular rate sensors and accelerometers, in a system of aircraft attitude evaluation. The method depicts a suitability of using accelerometers to restrict an influence of angular rates' integration on a precision of the attitude assessment. The method was verified with a simulation in MATLAB-Simulink environment and with various measurements. The method principles, simulation and measurement results are presented.

The paper describes a method that enables a usage of low-cost angular rate sensors in an aircraft attitude evaluation. The method depicts a suitability of using accelerometers to restrict an influence of angular rate integration on a precision of the attitude assessment. The method was verified with a simulation in MATLAB-Simulink environment. The method principle and its simulation results are presented.

The paper describes a method that enables a usage of low-cost inertial sensors, such as angular rate sensors and accelerometers, in an aircraft attitude evaluation system. The method depicts a suitability of using accelerometers to restrict an influence of angular rates' integration on a precision of the attitude assessment. The method was verified with a simulation in MATLAB-Simulink environment. The method principal and its simulation results are presented.

Presentace se věnuje metodice využívající akcelerometry, jejichž soustava neodpovídá hlavním osám letadla, pro detekci náklonů letadla.

Příspěvek popisuje systém generující signály selsynu či rozkladače, který je vhodný pro testování programů v moderních systémech LCD zobrazování.

Publikace se věnuje metodice vyhodnocování dat z akcelerometrů a senzorů úhlových rychlostí, která umožňuje provádění korekcí náklonů letadla během letu.

Příspěvek se věnuje způsobu generování signálů odpovídajících výstupům selsyny či rozkladače, a tak umožňuje ověření funkce softwaru zobrazovací jednotky.