Active-sensing Approach Research Articles

Localization With Reconfigurable Intelligent Surface: An Active Sensing Approach

Localization With Reconfigurable Intelligent Surface: An Active Sensing Approach

Experimental Evaluation of Wearable Piezo Ring for Bolted Connection Monitoring Using the Active Sensing Approach

As a safe and reliable connection, bolted connection is widely used in various structural systems. Monitoring the bolted connection is beneficial to ensure the safety of the whole structure. In this study, a wearable piezoelectric ring based on piezoelectric material is designed and it can be easily integrated into the bolt connection as a washer. To verify the feasibility of wearable piezoelectric ring, single-bolt looseness experiment based on wearable piezoelectric ring was carried out. Firstly, the wearable piezoelectric ring was installed on the bolted joint, acting as a piezoelectric sensor, and multiple piezoelectric actuators were installed in different location of the plate surface. Then, different torque level was applied to the bolt and the stress wave signals were obtained by piezoelectric active sensing technique. Finally, the recursive analysis method was introduced to extract nonlinear recursive features of the stress wave signals. The experimental results showed that the change of the bolt looseness could be qualitatively characterized by the phase space trajectory and the recurrence plots. Moreover, the recursive entropy could quantitatively characterize the bolt looseness, showing a bright prospect in monitoring the bolt looseness using the wearable piezoelectric ring.

A Multi-Task Learning for 2D Phase Unwrapping in Fringe Projection

Phase unwrapping is a challenging task in signal processing, spanning its applications in optical metrology, SAR interferometry, and many other signal reconstruction tasks. Fringe Projection Profilometry is a popular active-sensing approach for generating high-resolution three-dimensional (3D) surface information in which phase unwrapping is a crucial step. This letter proposes a multi-task learning-based phase unwrapping method for simultaneous denoising and wrap-count prediction in fringe projection. The proposed network, referred to as TriNet, has nested pyramidal architecture with a single encoder and two decoders, all connected through skip connections. The proposed approach does not require any pre-processing for noise removal like the conventional methods or any post-processing such as smoothing, like in existing deep learning methods but results in a quite accurate phase unwrapping. The proposed method outperforms the existing and state-of-the-art methods for the 3D reconstruction task in Fringe Projection by a significant margin even in the presence of very high noise.

Feasibility Study of an Active Sensing Approach to Detect Soil Slope Interlayer Slide Using Piezoceramic Buzzers

For soil slope, interlayer slide along the soil-rock interface is the precursor and cause of large-scale landslide disasters. Deep stability status in the slope body is crucial and has always been highly valued in geotechnical engineering. Real-time monitoring of soil-rock interface and early warning of landslide disaster is of great importance for landslide disaster prevention, mitigation and relief. In order to explore the evolution process of the soil-rock interface from stability to slippage, a physical model test at conventional gravitational acceleration condition was performed in laboratory. In this study, an innovative active sensing approach based on four piezoceramic buzzers that attached on an aluminum bar was proposed to detect the soil slope interlayer slide. Among the four buzzers, one was employed as an actuator to generate stress wave, while other three were acted as sensors to receive the propagated signals. The installation of transducers, fabrication of the slope model and monitoring system were presented in detail. During the test, a horizontal thrust was applied on the trailing edge of the slope model using a hydraulic jack. The interlayer slide behavior was then carefully monitored by the propagated stress waves. It was found that the measured stress waves in both time and frequency domain had a negative correlation with the slope sliding distance. It can be attributed to that the interlayer slide attenuates wave energy and then decreases the signal intensity. Additionally, a wavelet packet analysis was employed to develop a slope slide index to evaluate the soil-rock interlayer slide. Experimental results demonstrated that the proposed method is novel yet effective for soil slope interlayer slide monitoring.

Interface Debonding Detection of Precast Segmental Concrete Beams (PSCBs) Using Piezoceramic Transducer-Based Active Sensing Approach

An active sensing approach using piezoceramic induced stress wave is proposed to provide monitoring and early warning for the development of interface debonding damage of precast segmental concrete beams (PSCBs). Three concrete specimens with toothed interfaces were fabricated and bonded with high-strength epoxy resin adhesive to form PSCBs. Smart aggregates (SAs) embedded in concrete specimens are used as actuators and sensors. The PSCBs are subjected to periodic loading with hydraulic jack to test the different degrees of debonding damage. The experimental results of time-domain and frequency-domain analysis clearly show that the amplitude of the signal received by the piezoceramic sensor is reduced when debonding crack occurs. The energy analysis and damage index based on wavelet packet can be used to determine the existence and severity of interface debonding damage in PSCBs. The experimental research validates the feasibility of monitoring the interface debonding damage in PSCBs using SA transducers based on active sensing technique.

Monitoring of Bolt Looseness-Induced Damage in Steel Truss Arch Structure Using Piezoceramic Transducers

In this paper, we develop a stress wave-based active-sensing approach using piezoceramic transducers to detect the bolt looseness-induced damage in steel truss arch structures. A specimen of a steel tress arch structure was designed and fabricated. The structure consisted of top chords, bottom chords, Web members, and gusset plates, which were all connected by bolted connections. To implement the active sensing approach, the lead zirconate titanate (PZT) transducer bonded on the gusset plate was used as an actuator to generate stress waves, and the PZT transducers mounted on the other parts, such as top chords, bottom chords, and Web members, were used as sensors to detect the propagated stress waves. Based on the tightness of the bolts, the specimen had three different states: the healthy state, damage state I, and damage state II. The signals received by the PZT sensors were analyzed using the wavelet packet analysis. In addition, the structure stiffness was also considered as a comparative approach in this paper. The experimental results illustrate that when the initial looseness-induced damage occurs, the structure stiffness is not significantly reduced while the wavelet packet energy changes significantly, revealing the advantage of the proposed approach over the stiffness-based method. These research results demonstrated that the developed piezoceramic-based active-sensing approach has potentials to identify the initial bolt looseness occurrence for steel truss arch structures.

Study of Impact Damage in PVA-ECC Beam under Low-Velocity Impact Loading Using Piezoceramic Transducers and PVDF Thin-Film Transducers.

Compared to conventional concrete, polyvinyl alcohol fiber reinforced engineering cementitious composite (PVA-ECC) offers high-strength, ductility, formability, and excellent fatigue resistance. However, impact-induced structural damage is a major concern and has not been previously characterized in PVA-ECC structures. We investigate the damage of PVA-ECC beams under low-velocity impact loading. A series of ball-drop impact tests were performed at different drop weights and heights to simulate various impact energies. The impact results of PVA-ECC beams were compared with mortar beams. A combination of polyvinylidene fluoride (PVDF) thin-film sensors and piezoceramic-based smart aggregate were used for impact monitoring, which included impact initiation and crack evolution. Short-time Fourier transform (STFT) of the signal received by PVDF thin-film sensors was performed to identify impact events, while active-sensing approach was utilized to detect impact-induced crack evolution by the attenuation of a propagated guided wave. Wavelet packet-based energy analysis was performed to quantify failure development under repeated impact tests.

Feasibility Study of Interlayer Slide Monitoring Using Postembedded Piezoceramic Smart Aggregates

Utilizing embedded transducers is an effective approach to monitor a landslide. However, for existing structures, sensors can only be postembedded, which involves drilling and grouting, and may change the original state of the structure, which calls for the need to study the effectiveness of postembedded transducers. The main focus of this paper is the feasibility study of the interlayer slide detection using postembedded piezoceramic smart aggregates (SAs). In this study, a small landslide structure that involves a weak layer is studied and two pairs of SAs were embedded in predetermined positions inside the structure. To study the difference, one pair of transducer was preembedded and the other pair was postembedded. Within each pair, one SA was employed as an actuator to generate stress waves, and another SA used as a sensor to detect wave responses. Active-sensing approach was developed to perform continuous monitoring during structural loading that was used to induce an interlayer slide. The occurrence of interlayer slide attenuates wave energy and decreases signal intensity. A wavelet-packed index was proposed to detect the occurrence and development of interlayer slide. Experimental results demonstrated that SA installation through postembedding process is an innovative yet effective approach to monitor interlayer slide.

Integrating passive- and active-sensing techniques using an L-shaped sensor array for impact and damage localization

This article presents a technique for detecting structural impact and damage by integrating passive and active-sensing approaches. An L-shaped piezoelectric sensor array was used to detect and localize impacts by measuring the response of structures. It was found that since this method does not require prior knowledge of structures such as the direction-dependent wave velocity profiles, accurate results could be achieved even on anisotropic structures. This sensor array was then extended to include an active-sensing approach, and the same sensor array was used for damage detection by measuring scattering and reflected waves. A series of experiments was carried out to demonstrate the proposed techniques. The superior capability of the proposed techniques was experimentally demonstrated.

Interlayer Slide Detection Using Piezoceramic Smart Aggregates Based on Active Sensing Approach

Interlayer slide is a common type of damages in geological and civil engineering. Interlayer slide damage is an internal cause of landslide and collapse, which may further result in catastrophic losses. It is desirable to develop a real-time monitoring system that is able to detect this kind of damage. In this paper, an experimental feasibility study on interlayer slide detection using piezoceramic smart aggregates based on the active sensing approach was performed. A mortar specimen, sandwiched with a weak interlayer, was fabricated before conducting the loading test. Two pairs of smart aggregates were installed at specific positions inside of the formwork before pouring the mortar. With the embedded piezoceramic patch transducers, the smart aggregates possess both the actuation and sensing functions. Two smart aggregates were employed as actuators, which generated the stress wave to propagate through the weak interlayer. The other two smart aggregates were used as sensors to receive the wave responses. In addition, a wavelet packet analysis was applied to develop a damage index to assess the initiation and development of the interlayer slide. Experimental results show that the proposed method was able to detect the interlayer slide damage.

Multiple Cracks Detection in Pipeline Using Damage Index Matrix Based on Piezoceramic Transducer-Enabled Stress Wave Propagation.

Cracks in oil and gas pipelines cause leakage which results in property damage, environmental pollution, and even personal injury or loss of lives. In this paper, an active-sensing approach was conducted to identify the crack damage in pipeline structure using a stress wave propagation approach with piezoceramic transducers. A pipeline segment instrumented with five distributed piezoceramic transducers was used as the testing specimen in this research. Four cracks were artificially cut on the specimen, and each crack had six damage cases corresponding to different crack depths. In this way, cracks at different locations with different damage degrees were simulated. In each damage case, one piezoceramic transducer was used as an actuator to generate a stress wave to propagate along the pipeline specimen, and the other piezoceramic transducers were used as sensors to detect the wave responses. To quantitatively evaluate the crack damage status, a wavelet packet-based damage index matrix was developed. Experimental results show that the proposed method can evaluate the crack severity and estimate the crack location in the pipeline structure based on the proposed damage index matrix. The sensitivity of the proposed method decreases with increasing distance between the crack and the mounted piezoceramic transducers.

Cyclic Crack Monitoring of a Reinforced Concrete Column under Simulated Pseudo-Dynamic Loading Using Piezoceramic-Based Smart Aggregates

Structural health monitoring is an important aspect of maintenance for bridge columns in areas of high seismic activity. In this project, recently developed piezoceramic-based transducers, known as smart aggregates (SA), were utilized to perform structural health monitoring of a reinforced concrete (RC) bridge column subjected to pseudo-dynamic loading. The SA-based approach has been previously verified for static and dynamic loading but never for pseudo-dynamic loading. Based on the developed SAs, an active-sensing approach was developed to perform real-time health status evaluation of the RC column during the loading procedure. The existence of cracks attenuated the stress wave transmission energy during the loading procedure and reduced the amplitudes of the signal received by SA sensors. To detect the crack evolution and evaluate the damage severity, a wavelet packet-based structural damage index was developed. Experimental results verified the effectiveness of the SAs in structural health monitoring of the RC column under pseudo-dynamic loading. In addition to monitoring the general severity of the damage, the local structural damage indices show potential to report the cyclic crack open-close phenomenon subjected to the pseudo-dynamic loading.

A New Signal Structure for Active Sensing in Cognitive Radio Systems

This paper presents a new signal structure for spectrum sensing under active cognitive radio (CR) transmission (i.e., active sensing). Specifically, the known pilots used for the base station of primary users (PU) are duplicated and reallocated in the CR transmission signal properly so that there is no overlap between the reallocated pilot subcarriers and the original subcarriers. Given the CR signal structure, the signal received by a spectrum sensor of the CR system becomes correlated on the subcarriers when PU reoccupation occurs during the data-transmission periods, which makes it easy to detect PU activities by computing the spectral correlation function of the received signal. Both theoretical analyses and simulation results are given to demonstrate the effectiveness of the proposed active-sensing approach. The proposed method attains a detection probability of 0.99 and a false-alarm probability of 0.01 within 170 orthogonal frequency-division multiplexing symbols under a signal-to-noise ratio of -25dB and a signal-to-interference ratio of -20dB. The performance would be degraded under practical conditions, but is acceptable in most cases if the carrier frequency offset is less than 0.3. Compared with traditional cyclostationary feature detection, the proposed approach requires only about half the sensing time to achieve the same sensing accuracy, at about a 3% loss of throughput.

Very early age concrete hydration characterization monitoring using piezoceramic based smart aggregates

Very early age (0–20 h) concrete hydration is a complicated chemical reaction. During the very early age period, the concrete condition dramatically changes from liquid state to solid state. This paper presents the authors’ recent research on monitoring very early age concrete hydration characterization by using piezoceramic based smart aggregates. The smart aggregate (SA) transducer is designed as a sandwich structure using two marble blocks and a pre-soldered lead zirconate titanate (PZT) patch. Based on the electromechanical property of piezo materials, the PZT patches function as both actuators and sensors. In addition, the marble blocks provide reliable protection to the fragile PZT patch and develop the SA into a robust embedded actuator or sensor in the structure. The active-sensing approach, which involved a pair of smart aggregates with one as an actuator and the other one as a sensor, was applied in this paper’s experimental investigation of concrete hydration characterization monitoring. In order to completely understand the hydration condition of the inhomogeneous, over-cluttering, high-scattering characteristics of concrete (specifically of very early concrete), a swept sine wave and several constant frequency sine waves were chosen and produced by a function generator to excite the embedded actuating smart aggregate. The PZT vibration induced ultrasonic wave propagated through the concrete and was sent to the other smart aggregate sensor. The electrical signal transferred from the smart aggregate sensor was recorded during the test. As the concrete hydration reaction was occurring, the characteristic of the electrical signal continuously changed. This paper describes the successful investigation of the three states (the fluid state, the transition state, and the hardened state) of very early age concrete hydration based on classification of the received electrical signal. Specifically, the amplitude and frequency response of the electrical signal were of main interest. Both the swept sine wave and the constant frequency sine wave excitation methods presented the same conclusion on the three concrete states during the hydration, which enhances the reliability of the active-sensing approach for very early age concrete hydration monitoring.

Proof-of-concept experimental study of damage detection of concrete piles using embedded piezoceramic transducers

This paper presents a proof-of-concept experimental study of an innovative active-sensing approach for damage detection of concrete piles by using embedded piezoceramic transducers. In the proposed active-sensing approach, one piezoceramic transducer is used as an actuator to generate a stress wave to propagate through the concrete pile and the other distributed piezoceramic transducers are used as sensors to detect the wave response. Cracks or damage inside the concrete structure act as stress relief in the wave propagation path. The amplitude of the wave and the transmission energy will decrease due to the existence of cracks or damage. Experiments were performed on two bored piles instrumented with embedded piezoceramic transducers. The experimental results demonstrate the effectiveness of the proposed approach for pile damage detection.

Smart-aggregate-based damage detection of fiber-reinforced-polymer-strengthened columnsunder reversed cyclic loading

Structural health monitoring is an important aspect of the maintenance of large civilinfrastructures, especially for bridge columns in areas of high seismic activity. In thisproject, recently developed innovative piezoceramic-based sensors were utilized to performthe health monitoring of a shear-critical reinforced concrete (RC) bridge column subjectedto reversed cyclic loading. After the column failed, it was wrapped with fiber reinforcedpolymer (FRP) sheets, commonly used to retrofit seismically damaged structures. TheFRP-strengthened column was retested under the same reversed cyclic loading pattern.Innovative piezoceramic-based sensors, called ‘smart aggregates’, were utilized astransducers for health monitoring purposes. On the basis of the smart aggregatesdeveloped, an active-sensing approach and an impact-hammer-based approachwere used to evaluate the health status of the RC column during the loadingprocedure. Wave transmission energy is attenuated by the existence of cracks duringthe loading procedure, and this attenuation phenomenon alters the curve of thetransfer function between the actuator and sensor. To detect the damage occurrenceand evaluate the damage severity, transfer function curves were compared withthose obtained during the period of healthy status. A transfer-function-baseddamage index matrix was developed to demonstrate the damage severity at differentlocations. Experimental results verified the effectiveness of the smart aggregates inhealth monitoring of the FRP-strengthened column as well as the unstrengthenedcolumn. The experimental results show that the proposed smart-aggregate-basedapproach can successfully detect damage occurrence and evaluate its severity.