Michal Dub

DC motor experimental parameter identification using the Nelder-Mead simplex method

Mathematical model of separately excited DC motor is featured by transfer function. Searched parameters are motor gain coefficient and motor time constants. Offline identification algorithm is based on minimization of criteria function where searched variables are parameters of the mathematical model. The minimization algorithm is the Nelder-Mead simplex search method of the MATLAB program.

Concept of a complex navigation signal generator

The paper presents a concept and the first experimental results of a complex navigation signal generator (CNSG). The generator forms a signal of a predefined radio-navigation beacon received at a specific aircraft position. Recently the beacon is represented by a GNSS satellite and its movement is incorporated. The CNSG consists of the two main parts. The first is the DSP part which physically generates the resulting signal and is based on the FPGA device followed by a suitable DA converter. The second part of the CNSG is a software simulator of the navigation situation. A numerical model of a fixed wing aircraft which is suitable to simulate relative position of an aircraft with respect to the beacon is continually resolving the vector aircraft-beacon. That vector and its time derivatives are then transformed into the resulting amplitude, Doppler shift and phase shift of the signal. The aircraft model is based on a description of dynamic characteristics in form of the equations of motion with respect of the fundamental control forces. The main idea is to keep the model as simple as possible. Therefore only those relevant influences are incorporated.

Possibilities of COTS ultrasonic fuel quantity measurement

The article deals with possibilities of utilization of modern industrial sensors for aircraft fuel quantity measurement. The purpose of the fuel quantity measurement in aircraft with either stationary or rotary wings is to provide information about the total amount of fuel and fuel variations under all aircraft attitudes and with all types of fuel. In aircraft technology, there are especially two basic methods of fuel quantity measurement used that are based on measurement of fuel level. Both methods are contact measurement methods and the fuel gauge is always in contact with fuel. The older, easier and cheaper method is based on float level sensors. Modern and more precise method is based on capacitance level sensors. The measured fuel level is then converted to volume or weight of the fuel and displayed on a fuel indicator in the cockpit. Both methods have some limitations and for that reason another fuel level measurement methods have been introduced onboard. Our practical experiments deal with possibilities of COTS ultrasonic sensors utilization for fuel gauging inside small aircraft fuel tank. Ultrasonic fuel level measurement is based on reflecting sound energy at an interface of liquid and air. Tested operating conditions include influence of aircraft attitude changes, mechanical forces changes and temperature changes on whole measuring systems. Fuel volume is also measured by reference capacitance fuel gauge during practical experiments. Experimental results lead to error quantification of COTS ultrasonic fluid level measurement and following technical measures to minimization of systematic errors.

Some aspects of COTS ultrasonic fuel level measurement

The paper focuses on utilization of modern level sensors for measuring fuel volume in aviation. Ultrasonic principles of fuel quantity measurement have been introduced onboard aircraft to replace float level and capacitance level sensors. The principle of ultrasonic measurement of the fuel level is based on the reflection of sound waves at an interface of fuel and air. The fuel quantity can be calculated from fuel level if the shape of the tank is known. Specific electronic circuits were designed to employ ultrasonic transceivers operating at higher frequencies. Presented experiments compare characteristics of different ultrasonic sensors for installation in the aircraft fuel quantity measuring system. Tested operating conditions of several COTS ultrasonic sensors are focused on simulation of aircraft attitude changes.

Electronic starting control unit for small jet engine

The article deals with small aircraft turbine engine ignition and electrical system. Theoretical part describes design of electronic control unit based on analysis of engine starting process. Experimental part presents construction of second prototype of electronic control unit. Experimental results are discussed including graphical presentation of engine parameters.

Concept of experimental EHAS power pack design

EHAS (Electro Hydrostatic Actuation System) is progressive technology used in the design of advanced aircraft hydraulic systems. This paper describes the design process of an experimental EHAS power pack, which is suitable for already built fourth generation inherently unstable combat aircraft. The power pack is going to be modified to fit in available commercial parts uncertified for aviation, for instance power relays, ultra capacitor cells, control blocks, sensors, etc. Still, relevant results for an optimal power ratio between the power source, EAU[7] (Electronic Accumulator Unit), and the hydraulic accumulator determination are expected. Due to better energy distribution control, it will be possible to set the power pack to several operation modes, such as economic, normal, high performance and emergency modes. It is intended to perform series of measurements to make clear if several power pack operation modes are as beneficial as expected. Verification of the EAU capabilities is another part of the intended experiment. Moreover, it is planned to measure ultra capacitor heat generation and to observe behaviour of the power pack during simulated EAU malfunctions.

Parameter Identification - The random initial estimation issue

Experimental offline identification algorithm is based on minimization of criteria function considering the unknown mathematical model variables. We often use software support of various computing programs to find the minimum of a scalar function of several variables. However, operator has to know initial estimation of the searched parameters to get proper results. If operator sets bad initial estimation, the identification process would find another local minimum or would diverge. This paper is focused on random approach to initial estimation of simple mathematical model using basic MATLAB software support.

Complex navigation signal generator

Working design of the GNSS signal generator Xilinx Spartan 3MB platform — DA 12bit @ 125 MSPS Complex Air Navigation Geometry Simulator Simulated airplane movement Acquired and transformed real flight data GPS satellite movement model Signal parameters provided

Some aspects of aircraft electrical component dependability

This paper deals with operating conditions of aircraft electrical components and shows what effect these conditions have on the dependability of particular components and systems. Two aviation incidents are described and their reasons and results are presented. The mechanical design of a difference minimal relay DMR-400 and its influence on a power electrical system of Aero L-39C Albatros aircraft and L-159A Alca aircraft is also described. The DMR-400 is used as a main contactor of the DC generator and the main DC bus.