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A high-precision long-range cooperative radar system for gantry rail crane distance measurement
Abstract
We present the implementation of a cooperative radar system on a gantry rail crane for distance measurements in an industrial environment. The measurement approach is based on the dual-ramp frequency-modulated continuous-wave principle, using identical sensor-nodes at the endpoints of the range of interest. Pseudo-range information is exchanged via a dedicated data-link between these stations. At the sensor-node a flexible high-performance signal processing and remote management engine is implemented. The system setup is controlled by a single host-PC, which is used as a man–machine interface for configuration of the remotely controlled measurement stations, system surveillance, and visualization of the measurement data. Indoor characterization of the developed hardware is sufficient for an efficient calibration of the system, minimizing distance offsets. On-site measurements at distances up to 1000 m with an accuracy better than 2 cm confirm the performance of the ranging system. Furthermore, the results are verified by simulation.
... The received signal at each station is downconverted with a copy of the local transmit (TX) signal from the other station. The range information then can be calculated from the combined information of the participating sensor nodes, thus presuming a data-link [6]. ...
... Constant phase-terms have been summarized by w + 0,IF , w − 0,IF , and w 0,R . The frequency f R is the relevant signal component for the ranging system [6] with ...
... A fact that also should be taken care of is the possibility of different chirp rates caused by independent crystal oscillators for the generation of the ramp as well as the communication signal. Even if the difference is in the region of some ppm, which is typical for industrial crystal oscillators, the difference can cause a drift of the carrier frequency during the chirp of the order of several 10 kHz as it could be shown in [6]. The bandwidth of the BPF is therefore slightly extended to cover this drift. ...
We present the realization of a cooperative radar system for ranging applications with integrated data-transmission capability. The simultaneous transmission is performed by the radar-hardware without the necessity of additional components or an auxiliary data-link. Therefore, the data are directly embedded in the transmitted chirp of a frequency-modulated continuous-wave radar sensor. A second station, acting as receiver, uses an identical, but unmodulated chirp for down-conversion. The resulting signal then is processed by a non-coherent demodulator setup, extracting the communication data. Measurement results from transmission of messages with different bit-rates are shown. By utilizing existing radar-hardware a transmission rate of up to 256 kbps is possible, without the need of a dedicated transceiver. Additionally, a method to optimize the ranging results by variable distribution of the available signal power between distance-measurement and communication system is presented.
The GPS data received by a receiver, embedded into a moving vehicle, encounter the distance inaccuracy due to close-in multipath of reflected signals of adjacent moving vehicles. The said inaccuracy cause a failure of sub-lane detection of the vehicle that pass through a specific lane. Increasing the sensitivity level of the received signals, the inaccuracy can be controlled up to a great extent. In this paper we are interested in finding out the best condition to enhance the sensitivity level of received symbols. This is achieved through up-gradation of probability of detection of the received signals. Similarly, the process is refined up to a great extent by selecting the best discriminator function response (DFR) for the purpose of decreasing root mean square error (RMSE). Moreover, the best DFR is selected in order to increase the convergence rate for a certain discriminator which results in increase of sensitivity level of the received GPS symbols. The best optimized solution provides up to 4cm accuracy in selected DGPS receiver.
For the successful design of low-cost and high-performance radar systems accurate and efficient system simulation is a key requirement. In this paper we present a new versatile simulation environment for frequency-modulated continuous-wave radar systems. Besides common hardware simulation it covers integrated system simulation and concept analysis from signal synthesis to baseband. It includes a flexible scenario generator, accurate noise modeling, and efficiently delivers simulation data for development and testing of signal processing algorithms. A comparison of simulations and measurement results for an integrated 77-GHz radar prototype shows the capabilities of the simulator on two different scenarios.
We present the implementation of a cooperative radar system on a rail crane for distance measurements in an industrial environment. The measurement approach is based on the dual-ramp frequency-modulated continuous-wave prinicple, using identical sensor-nodes at the endpoints of the range of interest. Pseudo-range information is exchanged via a dedicated data-link between these stations. At the sensor-node a flexible high-performance signal processing and remote management engine is implemented. The system setup is controlled by a single host-PC, which is used as a man-machine interface for configuration of the remotely controlled measurement stations, system surveillance, and visualization of the measurement data. On-site measurements at distances up to 1000 m with an accuracy better than 2 cm confirm the performance of the ranging system. Furthermore the results are verified by simulation.
Global Positioning System (GPS) localization has been attracting attention recently in various areas, including intelligent transportation systems (ITSs), navigation systems, road tolling, smart parking, and collision avoidance. Although, various approaches for improving localization accuracy have been reported in the literature, there is still a need for more efficient and more effective measures that can ascribe some level of accuracy to the localization process. These measures will enable localization systems to manage the localization process and resources to achieve the highest accuracy possible and to mitigate the impact of inadequate accuracy on the target application. The localization accuracy of any GPS system depends heavily on both the technique it uses to compute locations and the measurement conditions in its surroundings. However, while localization techniques have recently started to demonstrate significant improvement in localization performance, they continue to be severely impacted by the measurement conditions in their environment. Indeed, the impact of the measurement conditions on the localization accuracy in itself is an ill-conditioned problem due to the incongruent nature of the measurement process. This paper proposes a scheme to address localization accuracy estimation. This scheme involves two steps, namely, measurement condition disambiguation and enhanced location accuracy classification. Real-life comparative experiments are presented to demonstrate the efficacy of the proposed scheme in classifying GPS localization accuracy under various measurement conditions.
In this paper, a radar system for local positioning applications is presented. The system consists of frequency modulated continuous-wave (FMCW) stations operating in W-band that are loosely coupled using time-delayed ramp start signals. A centralized signal processing approach allows to relax the required synchronization accuracy between the stations and further leads to a cancellation of phase noise and phase distortions caused by imperfect FMCW ramps. All stations are equipped with an antenna array and multiple receivers. Thus, a signal processing approach is developed in this work that combines the positive effects from the centralized processing with the information from the antenna array in a digital-beamforming based approach to improve the multipath robustness of the overall system. The developed theory is confirmed in measurements carried out with a prototype system consisting of two stations. Various measurements in multipath environments confirm the improved robustness leading to a worst-case root-mean-square position error of 15 mm under strong multipath conditions which were simulated inside an anechoic chamber.
In recent years, cooperative frequency-modulated continuous-wave radar based ranging and positioning systems attained significant attraction. In this paper, we present a novel analysis approach of the performance of these incoherent systems, with a special focus set on phase noise effects. We show the behavior in different signal to noise ratio conditions and compare two competing evaluation concepts. The results are verified on real measurement data, taken with a prototype ranging system in the 5.8 GHz ISM band.
The vehicle positioning system is a key component in such functions as vehicle guidance, driver alert and assistance, as well as vehicle automation. Typical vehicle applications require high reliability, low cost and sufficient accuracy under all operation conditions. This paper explores the feasibility of a low-order vehicle positioning system functioning under urban driving environments. The equipped vehicle will have a mid-range differential GPS (DGPS) unit and a few relatively simple in-vehicle sensors. A low-order DGPS/INS integration is explored by considering only vehicle longitudinal, lateral and yaw motions. The characteristics of DGPS measurements under urban environment are investigated and novel DGPS noise processing techniques are proposed to address common DGPS problems such as blockage and multipath. A resulting 4th-order Kalman filter-based DGPS/INS integration is successfully implemented in the test vehicle to demonstrate the feasibility of the proposed design. Experimental results illustrate the ability of the system to meet the accuracy and robustness requirements under a typical urban driving environment
We present a frequency-modulated continuous-wave secondary radar concept to estimate the offset in time and in frequency of two wireless units and to measure their distance relative to each other. By evaluating the Doppler frequency shift of the radar signals, the relative velocity of the mobile units is measured as well. The distance can be measured with a standard deviation as low as 1 cm. However, especially in indoor environments, the accuracy of the system can be degraded by multipath transmissions. Therefore, we show an extension of the algorithm to cope with multipath propagation. We also present the hardware setup of the measurement system. The system is tested in various environments. The results prove the excellent performance and outstanding reliability of the algorithms presented.
In many applications the precise distance between different units has to be measured. The proposed measurement system operates with frequency modulated continuous wave (FMCW) radar sensors for distance measurement in a cooperative but unsynchronized way. Due to the missing synchronization a data transfer between the units is performed by means of the radar hardware. On the other hand, this principle could be easily implemented in communication systems. A prototype system in the 5.8-GHz ISM band has been built, and measurement results up to about 780 meters distance with accuracies of few centimeters are shown. Furthermore, the distance can be calculated at both transponder units.
Frequency modulated continuous wave (FMCW) radar uses a very low
probability of intercept waveform, which is also well suited to make
good use of simple solid-state transmitters. FMCW is finding
applications in such diverse fields as naval tactical navigation radars,
smart ammunition sensors and automotive radars. The paper discusses some
features of FMCW radar which are not dealt with in much detail in the
generally available literature. In particular, it discusses the effects
of noise reflected back from the transmitter to the receiver and the
application of moving target indication to FMCW radars. Some of the
strengths and weaknesses of FMCW radar are considered. The paper
describes how the strengths are utilised in some systems and how the
weaknesses can be mitigated. It also discusses a modern implementation
of a reflected power canceller, which can be used to suppress the
leakage between the transmitter and the receiver, a well known problem
with continuous wave radars