High-resolution signal-in-space measurements of VHF omnidirectional ranges using UAS

In this paper, we describe measurement results of the signal-in-space of very high frequency (VHF) omnidirectional range (VOR) facilities. In aviation VOR are used to display the current course of the aircraft in the cockpit. To understand the influence of wind turbines (WT) on the signal integrity of terrestrial navigation and radar signals, the signal content and its changes, respectively, must be investigated. So far, only numerical simulations have been carried out on the frequency-modulation (FM) part of the Doppler-VOR (DVOR) signal to estimate the influence of WT on DVOR. Up to now, the amplitude-modulated (AM) part of the DVOR was not assessed at all. In 2016, we presented an unmanned aerial system (UAS) as a carrier for state-of-the-art radio-frequency (RF) measurement instrumentation (Schrader et al., 2016a, c; Bredemeyer et al., 2016), to measure and to record the true signal-in-space (both FM and AM signal) during the flight. The signal-in-space (which refers to time-resolved signal content and field strength, respectively) is measured and sampled without loss of information and, furthermore, synchronously stored with time stamp and with precise position in space, where the measurements were taken

Position Acquisition and Control for Linear Direct Drives with Passive Vehicles

For combined processing and transportation of materials in industrial production lines, a long primary, linear synchronous drive with passive, lightweight vehicles, is being designed and experimentally tested. This thesis concentrates on position acquisition and motion control of the proposed system. In order to allow a high degree of independency in the movement of the vehicles,the stator (primary) of the linear machine is divided into many segments. Each segment of the track is fed by a dedicated power stack, and control information is exchanged between all power stacks and all vehicle controllers via an Inverter Bus. A number of processing stations are spread along the track of the linear drive, being connected by transport sections. Inside the processing stations, high quality speed and position control of the vehicles is required. For this, precise and fast position measurement is necessary, so position sensors must be used. The passive vehicles impose additional challenges for the position acquisition system, as neither energy nor information must be transmitted to the moving parts. The evaluation of two position acquisition systems, which comply with this requirement, is presented in this thesis. The first system is based on a high-resolution optical encoder. For this application, the scale of the optical sensor is mounted at the vehicle and several active read-heads are installed along the track, such that at each position the scale covers at least one readhead. When the scale is passing from one read-head to the next one, the position information from both read-heads must be evaluated simultaneously and synchronised, so that a continuous position signal will result for the entire measuring length. The second position acquisition system uses a comparatively lower resolution capacitive sensor, and is intended as a simpler and cost effective alternative to the optical system. The principle of operation of a capacitive sensor is first analysed, and a model is determined. Then, based on this model, two methods of extracting the position information are presented: one uses instantaneous (sampling-based) demodulation, while the other is based on phase measurement. In the transport sections of the linear drive the requirements concerning the accuracy and dynamic of the position measurement are less demanding than in the processing stations. In this sections sensorless control, based on the evaluation of the electromotive force (EMF) is implemented. The distinctive parameters of the different stator segments are taken into consideration. Due to mechanical constraints, there are gaps in the winding arrangement between consecutive segments of the machine, which means that the EMF vectors of two consecutive segments can have an arbitrary phase difference, providing additional challenges, especially for the sensorless control. At the transition between processing stations and transport sections, a synchronisation procedure between the measured position and the estimated one is described and experimentally evaluated

Radar echoes of individual wind turbines measured in L, S and C band

In the project WERAN it is also aimed to determine the interaction of wind turbines (WT) with radar signals. The evaluate the strength of single a single WT reflecting radar transmissions, measurement campaigns with multicopters (UAS) have been carried out at various radar sites in the L (Air Defense), S (AD and ATC) and C band (Precipitation radar). The presentation focusses on radar echoes received at different UAS flight altitudes and distances to the scatterers. It is useful to analyse the radar return both in the time and frequency domain to detect static and time variant signal components. Some results will be shown and discussed. In the follow-up project WERAN plus there are some additional airborne vehicles in use to carry the measurement equipment. Some ideas of what can be expected from measurements at higher altitudes and moving at horizontal speed will be shared

Precision Signal-in-space Measurements of Terrestrial Navigation Systems using Multicopter

The project WERAN aimed to determine the interaction of wind turbines (WT) with signals of terrestrial navigation systems such as VHF omnidirectional radio ranges (VOR) and RADAR. One of the main goals of the project was to quantify the additional VOR bearing error caused by wind turbines by means of measurement and numerical simulations. In this presentation we will discuss the results of on-site measurements and compare those with numerical simulations. A remote- controlled multicopter with precision localization has been used as measurement platform. It carries a compact but capable high frequency instrumentation and integrated antennas to measure simultaneously both the AM reference signal and the FM signal of a Doppler VOR as true signal-in- space. Actual position, time stamp and measurement data are simultaneously stored at the platform. These measurements give insight into the signal content and signal integrity of VOR with and without WT. Furthermore, varying operational conditions of WT such as rotation vs idle state or angular movement of the nacelle may have different influence on the additional bearing error. During the follow-up project WERAN plus we will use the measurement data and simulation results to derive a model-based assessment tool. This will allow for prediction of the degree of interference (additional bearing error) of additional WT in the area around VOR with given topology