Measuring Time-of-Flight in an Ultrasonic LPS System Using Generalized Cross-Correlation

Bubbly flows are commonly used in various applications and their measurement is an important research topic. The ultrasound pulse-echo technique allows for the detection of each bubble and the measurement of the position of its surface. However, so far it has been used only to measure single bubbles. This paper investigates whether the pulse-echo technique can be applied for measuring multiple bubbles concurrently. The ultrasonic transducer wavelength and diameter were selected based on expected bubble diameters so that each bubble produced a strong reflection. The pulse-echo was implemented to obtain good accuracy without sacrificing the signal processing speed. A tracking technique was developed for the purpose of connecting detected reflections to trajectories. The technique was tested experimentally by measuring the horizontal position of rising air bubbles in a water tank. The results show that the pulse-echo technique can detect multiple bubbles concurrently. The pulse-echo technique detected almost the same number of bubbles as a high-speed video. For average void fractions up to around 1% (and instantaneous void fraction reaching 5.3%), the rate of bubbles missed by the pulse-echo and the rate of noise trajectories both stayed less than 5%. The error rate increased with the void fraction, limiting the technique’s application range.

Section: Methodsmentioning

confidence: 99%

Ultrasound Pulse-Echo Coupled with a Tracking Technique for Simultaneous Measurement of Multiple Bubbles

Povolny

Kikura

Ihara

2018

“…The synchronization algorithm proposed here for a Wavelet-OFDM receiver is based on the use of multi-level complementary sequences or Zadoff-Chu sequences as pilot signals, since they provide suitable correlation properties and a flexible length, which allow the proposal to be adapted to the number of available subcarriers for transmission. Both types of sequences have been already used in numerous sensory systems described in previous works due to these correlation properties [ 29 , 30 ].…”

Section: Proposed Synchronization Algorithmmentioning

confidence: 99%

Efficient Implementation of a Symbol Timing Estimator for Broadband PLC

Nombela

García

Mateos

et al. 2015

Self Cite

Broadband Power Line Communications (PLC) have taken advantage of the research advances in multi-carrier modulations to mitigate frequency selective fading, and their adoption opens up a myriad of applications in the field of sensory and automation systems, multimedia connectivity or smart spaces. Nonetheless, the use of these multi-carrier modulations, such as Wavelet-OFDM, requires a highly accurate symbol timing estimation for reliably recovering of transmitted data. Furthermore, the PLC channel presents some particularities that prevent the direct use of previous synchronization algorithms proposed in wireless communication systems. Therefore more research effort should be involved in the design and implementation of novel and robust synchronization algorithms for PLC, thus enabling real-time synchronization. This paper proposes a symbol timing estimator for broadband PLC based on cross-correlation with multilevel complementary sequences or Zadoff-Chu sequences and its efficient implementation in a FPGA; the obtained results show a 90% of success rate in symbol timing estimation for a certain PLC channel model and a reduced resource consumption for its implementation in a Xilinx Kyntex FPGA.

“…In this particular case, the GRPLS is composed of five beacons and the LRLPS of four beacons (so the GRLPS has more redundancy). Because of the performances achieved with the actual LPS used in real tests [ 9 ], we will suppose that for all of the LPSs, the coverage area is a circle on the ground with a radius of five meters.…”

Section: Statement Of the Problem And Definitionsmentioning

confidence: 99%

Locally-Referenced Ultrasonic – LPS for Localization and Navigation

Gualda¹,

Ureña²,

García³

et al. 2014

Self Cite

This paper presents a flexible deployment of ultrasonic position sensors and a novel positioning algorithm suitable for the navigation of mobile robots (MRs) in extensive indoor environments. Our proposal uses several independently-referenced local positioning systems (LPS), which means that each one of them operates within its own local reference system. In a typical layout, an indoor extensive area can be covered using just a reduced set of globally-referenced LPS (GRLPS), whose beacon positions are known to the global reference system, while the rest of the space can be covered using locally-referenced LPSs (LRLPS) that can be distributed arbitrarily. The number of LRLPS and their position can be also changed at any moment. The algorithm is composed of several Bayesian filters running in parallel, so that when an MR is under the GRLPS coverage area, its position is updated by a global filter, whereas when the MR is inside the LRLPS area, its position is updated using position increments within a local filter. The navigation algorithm has been tested by simulation and with actual data obtained using a real set of ultrasonic LPSs.