Bridge Output Research Articles

Three-dimensional reconstruction and damage localization of bridge undersides based on close-range photography using UAV

Abstract Damage inspection on the undersides of bridges is an important and challenging part of routine bridge inspections. A method for 3D reconstruction and damage localization of bridge undersides based on close-range photography by unmanned aerial vehicle (UAV) and stereo vision combined with deep learning algorithms is proposed, the specific contributions include: (1) proposing a close-range photography method for acquiring high-resolution images from multiple perspectives of the bridge underside by UAVs, serving as the data source for damage analysis; (2) applying a deep learning-assisted segmentation method to optimize the multi-view geometry-based 3D reconstruction method, improving the efficiency of three-dimensional reconstruction, and defining the projection direction from the 3D reconstruction results to obtain ultra-high-resolution panoramic images of the bridge underside; (3) addressing the issue of detecting minor damages in large panoramic images by using a slice-assisted reasoning module and a lightweight convolutional YOLO v8 network to identify exposed steel bars corroded due to concrete damage in the panoramic images, and defining a coordinate system to localize the damages on the bridge underside. The proposed method was applied to damage detection and localization on the underside of a 160 m span main span of an in-service concrete bridge. The results demonstrate that the proposed method can quickly and accurately identify exposed steel bar corrosion on the bridge underside and output reports, proving the practicality of the proposed method.

A method for evaluating the design scheme of continuous measuring bridge of the instrumented wheelset

This paper proposes a method for evaluating the design scheme of continuous measuring bridge of the instrumented wheelset, based on the theory of continuous measurement of wheel-rail forces, Finite Element Analysis, and Levenberg-Marquardt algorithm. The elastic strain at each placement point of the strain gauge on the web surface of the wheel is expanded into Fourier series, and the general mathematical expressions of the output signals for each symmetric component, each bridge, and the synthesized bridge are provided. Nine typical measuring bridge schemes of strain gauge arrangement on the wheel web surface and seven typical measuring bridge schemes of strain gauge arrangement inside the measuring holes are given. The finite element model of the wheel is established using software ABAQUS, and the moving force is applied to the rolling surface of the wheel for simulation calculations. The output signals of 16 typical measuring bridges are then obtained. By utilizing the mathematical formulas of the bridge outputs and the simulation results, a matrix expression describing the relationship between amplitudes of all harmonics and the bridge output is given, and the amplitudes of all the former 20 orders harmonics of the bridge signal are obtained by applying Levenberg-Marquardt algorithm. Based on the analysis results of the harmonic amplitudes, a method is proposed to quantitatively evaluate the output signals of a single bridge (which can be either harmonic or triangular wave) and the synthesized bridge. The mathematical expressions of the evaluation indicators are provided within the range of 0 to 1. Finally, the analysis results of the evaluation indicators for 16 typical measuring bridges are presented and compared. The proposed method is not only applicable to the bridge design of the instrumented wheelset but also to the evaluation of signals from channels of the data collector when the instrumented wheelset is being calibrated on the test rig.

Wattmeter based on tunnel-effect magnetoresistance sensor.

This work shows how the tunnel-effect based magnetoresistance (TMR) technology can be used as a competitive sensing method in electrical current and power processors. The sensor is arranged in a Wheatstone bridge topology, and each magnetoresistance was composed of a series connection of 360 magnetic tunnel junction elements with the following structure (thickness in nm): 100 SiO2/5 Ta/15 Ru/5 Ta/15 Ru/5 Ta/5 Ru/20 IrMn/2 CoFe30/0.85 Ru/2.6 CoFe40B20/1.2 MgO/2 CoFe40B20/0.21 Ta/4 NiFe/0.20 Ru/6 IrMn/2 Ru/5 Ta/10 Ru. First, the electrical and thermal characteristics of the sensor were evaluated by analyzing its response to DC current sweeps at various temperatures, controlled using a climatic chamber. Nominal values of current sensitivity S (0.324 mV/A), bridge output offset voltage Vo,s,o (-37.1 mV), bridge input resistance Rinp,bridge (0.958 kΩ), and their thermal behavior were obtained (0.0036 mV/A°C, 0.079 mV/°C, and -0.31 Ω/°C). Second, an instrumentation system is introduced to characterize the sensor, measuring its sensitivity to AC line currents from the mains up to 10Arms. Finally, an electronic wattmeter was developed showing the relevant quantities of its design. The circuit is able to interface a TMR Wheatstone bridge to an analog processor. Power and current measurements were obtained from a 150Vrms AC mains 1.5 kW load with resistive and capacitive components, achieving less than 1% deviation over the expected values. The circuit shown can be used to interface these signals to more complex smart digital engines with active or reactive energy processing capabilities, while providing inherent high voltage isolation, thanks to its TMR measurement technology.

LabVIEW-based rotary balance data synchronization acquisition system design

Abstract To solve the problem that many high-precision rotating balance bridge output signals and angular phase signals need to be measured synchronously in wind tunnel force measurement experiments, a rotating balance data synchronization acquisition system is designed based on LabVIEW and NI PXIe acquisition board. LabVIEW graphical programming is applied, combined with STM32F407VET6 processor embedded development of the timing divider, using the equal interval method to obtain the required synchronization trigger signals and use them as the digital trigger signals of the NI PXIe acquisition card. In addition, multi-threaded programming technology is used to develop the upper computer software to realize the storage, display, and analysis of the collected data. The test proved that the system has high testing accuracy, a short development cycle, embedded visualization development is easy to debug, stable operation, and real-time and reliable data synchronization acquisition.

Design, fabrication and experimental analysis of piezoresistive bidirectional acoustic sensor

PurposeIdentification of the direction of the sound source is very important for human–machine interfacing in the applications such as target detection on military applications and wildlife conservation. Considering its vast applications, this study aims to design, simulate, fabricate and test a bidirectional acoustic sensor having two cantilever structures coated with piezoresistive material for sensing has been designed, simulated, fabricated and tested.Design/methodology/approachThe structure is a piezoresistive acoustic pressure sensor, which consists of two Kapton diaphragms with four piezoresistors arranged in Wheatstone bridge arrangement. The applied acoustic pressure causes diaphragm deflection and stress in diaphragm hinge, which is sensed by the piezoresistors positioned on the diaphragm. The piezoresistive material such as carbon or graphene is deposited at maximum stress area. Furthermore, the Wheatstone bridge arrangement has been formed to sense the change in resistance resulting into imbalanced bridge and two cantilever structures add directional properties to the acoustic sensor. The structure is designed, fabricated and tested and the dimensions of the structure are chosen to enable ease of fabrication without clean room facilities. This structure is tested with static and dynamic calibration for variation in resistance leading to bridge output voltage variation and directional properties.FindingsThis paper provides the experimental results that indicate sensor output variation in terms of a Wheatstone bridge output voltage from 0.45 V to 1.618 V for a variation in pressure from 0.59 mbar to 100 mbar. The device is also tested for directionality using vibration source and was found to respond as per the design.Research limitations/implicationsThe fabricated devices could not be tested for practical acoustic sources due to lack of facilities. They have been tested for a vibration source in place of acoustic source.Practical implicationsThe piezoresistive bidirectional sensor can be used for detection of direction of the sound source.Social implicationsIn defense applications, it is important to detect the direction of the acoustic signal. This sensor is suited for such applications.Originality/valueThe present paper discusses a novel yet simple design of a cantilever beam-based bidirectional acoustic pressure sensor. This sensor fabrication does not require sophisticated cleanroom for fabrication and characterization facility for testing. The fabricated device has good repeatability and is able to detect the direction of the acoustic source in external environment.

A piezoelectric-driven nanoindentation system for scanning electron microscope with improved analog compensation method.

This paper presents a novel piezoelectric-driven nanoindentation system for a scanning electron microscope (SEM) with an improved analog compensation (IAC) method. This system mainly consists of a piezoelectric-driven indenter head, a rectangle-shaped transducer, and a nanopositioner module. Compared with the state-of-the-art piezoelectric-driven nanoindentation system with a circle-shaped transducer, the proposed nanoindentation system is capable of multi-direction operation inside a SEM with a rectangle-shaped transducer. Self-matched semiconductor strain gauges are selected as the position sensor for the piezoelectric-actuator. The Wheatstone bridge output voltage cannot achieve a zero temperature coefficient because the temperature coefficients of self-matched semiconductor strain gauge pairs become significantly different from each other after installation in practice. An IAC method is proposed to compensate the temperature coefficients further. Compared with the existing analog compensation method, the IAC method solves the problem of amplifier saturation and improves the sensitivity of the self-matched semiconductor strain gauge pairs position sensor by 27%. The multi-direction operation results inside a standard SEM HITACHI SU5000 validate the advantage of the developed nanoindentation system.

Design and Fabrication of Piezoresistive Strain-Gauges for Harsh Environment Applications

Maximum operating temperature is usuallyone of the limiting factors for using of conventional sensors and other electronic devices. High-temperature sensors and electronics are required in some special applications e.g. measurement of deformations, stresses and pressures inside power generators. The design methodology of the some piezoresistive sensors utilizing FEM simulations is presented. Piezoresistive sensors based on thin-film metal sputtered layers, silicon-on-insulator (SOI) and nanocrystalline diamond layers (NCD) were successfully designed, fabricated and measured. The fabricated sensors are able to operate at temperatures up to 250 °C. Extensive study of sensor parameters e.g. deformation sensitivity, edge and contact resistances, temperature dependences gauge factor, bridge output voltage was performed. The measured values and investigated findings can be used for calibration of simulation software and in prospective design of more complex sensor structures.

Model Reference Adaptive Control of SPS-Based Dual Active Bridge Converter with Constant Power Loading

Abstract This paper presents a new model reference adaptive-based control (MRAC) for a single-phase shift-modulated dual active bridge DC-DC converter (SPS-DAB) with constant power loading (CPL). The non-linear control algorithm, developed based on the reduced order model of the converter, is subjected to a thorough stability and convergence analysis. The efficacy of the proposed control strategy is verified through simulations conducted on MATLAB R2023a and PLECS 4.5.6, demonstrating its capability to counteract the destabilising effects of the CPL, while ensuring precise tracking of the dual active bridge (DAB) output voltage, even amidst parameter variations. Comparative analysis highlights the superior robustness and performance of the proposed approach over the conventional proportional-integral (PI) controllers.

Design and Optimization of Wheatstone Bridge Adjustment Circuit for Resistive Sensors

A novel Wheatstone bridge adjustment circuit with both rough-tuning and fine-tuning functions is designed for balancing Wheatstone bridge in this paper. Firstly, the parametric circuit structure is constructed to facilitate the design of rough-tuning and fine-tuning sub-circuit parameters; Secondly, the quantitative index of Wheatstone bridge imbalance is defined, and the parameter design flow of the rough-tuning sub-circuit, which consists of two sets of series-parallel-resistor (SPR) structures that are respectively connected in parallel with the two branches of one half-bridge, is given to directly weaken the initial bridge imbalance in the manufacturing stage. Theoretical analysis results show that the SPR structure can effectively approach any expected value and reduce the number of fixed resistor types. Thirdly, parameters of the fine-tuning sub-circuit, which consists of a resistor and a digital-to-analog converter (DAC), are optimized based on any expected adjustable range. By adjusting the DAC input to seek the middle value of an analog-to-digital converter output, indirectly eliminate the additional bridge imbalance caused by mechanical assembly stress, gravity, ambient temperature, and etc. in the application stage. Then the influence of the fine-tuning parameters on linear fitting coefficients of the output vs. input of the Wheatstone bridge is analyzed theoretically. The results show that the DAC output voltage only has a significant linear impact on the intercept coefficient, while its impact on the scale coefficient is negligible. Finally, the effectiveness of the adjustment circuit is verified on a six-axis force/torque sensor that is developed for an Experimental Module Manipulator in the Chinese Space Station.

Focus on software, data acquisition, and instrumentation

Focus on software, data acquisition, and instrumentation

Flattop Modulation Technique for a Low-Device Count Single-Stage AC-DC DAB Converter to Improve Its Overall Efficiency

This article proposes a flattop modulation technique for a single-stage, single-phase bidirectional ac-dc dual-active-bridge (DAB) converter for achieving a flattopped DAB inductor current. The flattopped DAB inductor current has a low root mean square (rms) value, and it improves the soft-switching performance of the converter. The novelty of the proposed technique is that it guarantees flattopped DAB inductor current throughout the ac line cycle and has direct control over the ac current. In this technique, sinusoidal pulse width modulation (PWM) is performed at the ac side bridge for direct ac current control. Sinusoidal phase shift modulation is performed at the dc side to generate a bridge output voltage with a pulsewidth identical to the ac side bridge. The high-frequency (HF) transformer turns ratio is appropriately selected to match the voltages at the DAB inductor’s ends. Thereby, flattop DAB inductor current is achieved throughout the line cycle. The proposed modulation technique ensures a regulated dc bus at the ac side and provides a ripple-free ac current by interleaving. The operation of the converter under the flattop modulation technique is analyzed in detail, and parameter design guideline is provided. Experimental results from a 2-kW converter prototype support the theoretical claims.

Topology optimization for the design of a 3D-printed rotating shaft balance

Rotating shaft balances (RSBs) are devices that are used to measure rotor blade forces and moments of wind tunnel models during wind tunnel tests. The design of an RSB can be challenging, because it has to comply with many and sometimes contradicting requirements such as high stiffness and high strain gauge bridge outputs. The manufacturing of a conventional RSB consists of different subsequent steps, which can be time consuming, expensive and associated with many risks. Therefore, in this work, the authors investigate if a RSB can be designed by topology optimization and manufactured by 3D printing. A topology optimization method was developed with as design objective the minimization of strain energy with constraints for the volume of the RSB’s midsection, defined stresses at strain gauge locations used for the measurement of axial force and torque and an overhang constraint for additive manufacturing. The optimal preliminary design found by topology optimization was translated into a final printable design with the highest bridge sensitivity for axial force and torque, sufficient output for in-plane forces and moments and an acceptable safety factor on strength for combined loads. After adding extra supports required for printing, the RSB was successfully printed in metal by the laser powder bed fusion process, resulting in a product without external defects. The same topology optimization and manufacturing method can potentially be used for other balance types, leading to a reduction in total lead time and manufacturing costs while increasing the design freedom.

Drilling scheme analysis and output prediction of instrumented wheel-set based on Finite Element Method and LSTM

Based on the Finite Element Method and wheel-rail force measurement theory, the effects of different drilling schemes and parameters on the output of the measuring electrical bridge are analyzed, and the optimal parameters are determined. The finite element model of a metro instrumented wheel-set is established by software ABAQUS. The effects of drilling radius, hole size and wheel-rail contact point on the strain of measuring points are calculated and analyzed, and the measuring bridge outputs of two different drilling schemes are compared. The output of the wheel-rail forces is predicted based on LSTM long short memory network. The results show that: (1) the optimal drilling position is on the middle surface of the wheel, (2) The drilling scheme of eight-hole is better than that of four-hole, (3) LSTM neural network can realize decoupling of bridge signal and high precision prediction of wheel-rail forces.

Novel method for load acquisition for the shock absorber upper strut mount of an automotive suspension system

A novel method for loads acquisition to the shock absorber upper strut mount by two three-component column-type sensor and spring sensor is proposed in this research. The strain gauge configuration and the decoupling balanced bridge circuit of the proposed column-type sensor are designed and analyzed theoretically. In order to verify the theoretical analysis of the measurement bridge output, simulations, and experimental tests were performed. It was shown that the measurement bridge outputs from the theoretical analysis, simulations and experiments were basically consistent. Then, the calibration of the designed sensors was conducted according to the SAE J2570 standard specification requirements, which were then employed to measure the lateral and impact force of the shock absorber upper strut mount. Taking the loads acquired on pothole road as an example, the signal of each sensor was described and the lateral and impact force loads on the upper strut mount is finally calculated.

Control strategy for DC series-connected wind farm without energy curtailment

With lower construction costs and power losses, the DC wind farm (DCWF) based on series-connected DC wind turbines (DCWT) is a potential collection scheme for large-scale offshore wind power. However, energy curtailment caused by unequal wind speed exists in DCWTs and results in energy waste, weakening the advantages of DCWTs. The energy curtailment mechanism is analyzed for DCWF, where single active bridge (SAB) is used as DC/DC converter in DCWTS and a full-bridge modular multilevel converter (FB-MMC) as the receiving end converter. The linear relationship between input and output of single active bridge (SAB) is interpreted, and a novel coordinate control strategy for DCWF is proposed to solve the wind energy curtailment caused by unequal wind speed. In addition, an auxiliary control strategy for receiving end converter is proposed to reduce the loss on HVDC link. A complete DCWF is built in PSCAD/EMTDC software package, and the results show that the proposed control strategy makes DCWF can operate well without energy curtailment under unequal wind speeds.

Development of a Flexible MEMS Sensor for Subsonic Flow.

Detection and control of flow separation is a key to improving the efficiency of fluid machinery. In this study, we developed a flexible MEMS (microelectromechanical systems) sensor for measuring the wall shear stress and flow angle in subsonic airflow. The developed sensor is made of a flexible polyimide film and a microheater surrounded by three temperature sensor pairs. The sensor measures the wall shear stress from the heater output and the flow angle from the temperature gradient around the heater. The geometry and design of the heater and temperature sensors were determined based on numerical simulations. To evaluate the validity of the sensor, we conducted an experiment to measure the wall shear stress and the flow angle in a wind tunnel in different velocities ranging from 30 m/s to 170 m/s, equivalent to Mach numbers from 0.1 to 0.5. The heater output was proportional to one-third power of the wall shear stress. Additionally, the bridge output correlating the temperature difference between two opposing temperature sensors showed sinusoidal variation depending on the flow angle. Consequently, we have clarified that the developed sensor can measure both the wall shear stress and flow direction in subsonic flow.

Shock absorber lateral and impact force measurement using a column-type sensor

A novel method for the lateral and impact force measurement of shock absorbers using a three-component column-type sensor is proposed in this study. The strain gauge configuration and the bridge connection were designed, and the outputs of each designed measuring bridge under both alignment and eccentric loading were theoretically analyzed. Simulations and experimental tests were conducted to validate the measuring bridge output of the theoretical analysis; the results from the theoretical analysis, simulation, and experiments agree well with one another. In accordance with the specifications put forth in the SAE J2570 standard, the designed sensor was calibrated to obtain its performance parameters and calibration coefficients, which were then applied to acquire the lateral and impact force of a shock absorber. The calibration results demonstrate that the maximum nonlinearity and hysteresis were 0.51% and 0.87% (full-scale), respectively, and the sensor had good linearity and weak coupling between dimensional characteristics.

Design and Implementation of the New Sensorless Rotor Position Estimation in Homopolar Salient-Pole Brushless DC Motor

This article presents a novel method for indirect sensing of the rotor position in a homopolar salient-pole brushless dc (BLDC) motor and driving the motor smoothly from a standstill using an inductance bridge. Based on the characteristic of the phase inductance variation, the rotor position can be determined by using the inductance bridge to estimate the inductance of unknown phases. The proposed technique uses the motor winding in Hay’s bridge, and it is adjusted to achieve a balanced condition in an unaligned position when the minimum inductance occurs. In a running mode, by rotating the rotor, an idle phase inductance is changed and Hay’s bridge goes into an unbalanced condition. Then, by injecting extra voltage pulses into idle phases, the bridge output state changes. It then continues to sense the rotor position, while the motor is running by applying the same procedure. Moreover, the proposed method does not have problems like those in previous researches such as mutual inductance effects, need of large memory for locking up of the data, and losing of the estimation accuracy by the change in the sampling rate. As the main salient features of the proposed method, load independent, simplicity in implementation, and flexibility in tuning can be pointed out. Finally, experimental tests have been carried out to confirm the feasibility and practicability of the proposed method.

Analysis of Unidirectional Secondary Resonant Single Active Bridge DC–DC Converter

A compact and highly efficient unidirectional DC–DC converter is required as a battery charger for electrical vehicles, which will rapidly become widespread in the near future. The single active bridge (SAB) converter is proposed as a simple and high-frequency isolated unidirectional converter, which is comprised of an active H-bridge converter in the primary side, an isolated high frequency transformer, and a rectifying secondary diode bridge output circuit. This paper presents a novel, unidirectional, high-frequency isolated DC–DC converter called a Secondary Resonant Single Active Bridge (SR–SAB) DC–DC converter. The circuit topology of the SR–SAB converter is a resonant capacitor connected to each diode in parallel in order to construct the series resonant circuit in the secondary circuit. As a result, the SR–SAB converter achieves a higher total power factor at the high frequency transformer and a unity voltage conversion ratio under the unity transformer turns ratio. Small and nonsignificant overshoot values of current and voltage waveforms are observed. Soft-switching commutations of the primary H-bridge circuit and the soft recovery of secondary diode bridge are achieved. The operating philosophy and design method of the proposed converter are presented. Output power control using transformer frequency variation is proposed. The effectiveness of the SR–SAB converter was verified by experiments using a 1 kW, 48 VDC, and 20 kHz laboratory prototype.

Closed loop analysis of Dual Bridge Converter with 4- levels

Abstract: A dual bridge (DB) LLC resonant converter for dc-dc conversion with closed loop is proposed in the system. The model is capable of delivering very low voltage, with a variable input dc fluctuations in the source side. The new PWM technique used helps the bridge output robust. The proposed model works only in 4 modes of operation. DB LLC converter uses different phase shift for each individual switches with different duty ratios. The model is simulated with 160V/200V DC input and 24V output with 20A i.e. 480W is provided to verify the operation. Keywords: Dual Bridge, LLC resonant converter, Closed loop operation, Boost converter.