Multisensor piezoelectric balances are increasingly used in wind tunnel tests requiring high dynamic performance, due to their flexible structure, easy fabrication, high stiffness, and excellent dynamic performance. However, superimposed manufacturing and assembly errors degrade their force-measuring performance. To address this issue, this article proposes a novel assembly method for such balances based on a complex statically indeterminate structure. The method controls the preload of connecting bolts using a digital torque wrench and optimizes sensor height via three approaches, leveraging coordinate measuring machine data and copper sheets’ high plasticity. Mechanical and mathematical models were established, followed by simulations to analyze error impacts, and a six-component force calibration system was built for static/dynamic tests. Results show that placing copper sheets on sensors’ top/bottom (with uniform bolt preload) significantly reduces force imbalance; top-placed sheets improve static performance. Natural frequency tests confirm no negative impact on dynamic performance, verifying the method’s effectiveness and feasibility.

The aero vector engine is the core backbone for the high agility, post-stall maneuverability, and short takeoff/ landing capabilities of next-generation fighter aircraft. During its development and finalization phases, precise measurement of the generated vector thrust parameters is indispensable to establish the correlation between thrust magnitude, angle, and control parameters-this precise measurement ensures the accurate execution of the fighter's tactical maneuvers. To overcome the limitation of inadequate dynamic response in traditional strain-based distributed measurement methods, this study proposes a high-dynamic vector thrust distributed testing system for aero engines, with piezoelectric sensors as force-sensitive elements. To achieve high-precision measurement, the research follows a logical workflow: first, the influence of different spatial arrangements of piezoelectric force-sensitive units (PFSU) on test performance was investigated, and a theoretical mechanical model was established to correlate the system's overall force with the three-dimensional force outputs of individual PFSUs; based on the theoretical model, ANSYS was utilized for static and modal simulation analysis to confirm that the system's structural strength and natural frequency meet design requirements; after validating the feasibility via simulation, three-way orthogonal experiments were conducted using a calibration loading device to obtain the calibration coefficient matrix and decoupling compensation matrix; finally, single/double vector angle simulation loading experiments are performed to verify the reliability of the system's performance. Experimental results show that the AE-VTTS exhibits excellent static and dynamic performance, with good linearity and repeatability. The measurement error of force and angle in each direction is <= 1.5%, and the firstorder natural frequency reaches 20.02 Hz (higher than the 10 Hz of the strain-based system in the laboratory). This study provides an innovative solution for the high-precision static and dynamic measurement of aero engine vector thrust.

The main transmission system of a helicopter is a core component that transmits engine power to the rotor, and its mechanical characteristics directly affect the safety and reliability of the helicopter. The rotor force measuring instrument is a key device for measuring the aerodynamic loads of the rotor. Among the existing force measuring instruments, the strain force measuring instrument is suitable for most rotor load measurement scenarios due to its high precision (0.1-0.3 %) and moderate dynamic response. However, the integral type has errors in strain force measuring instrument bonding and high cost, while the combined type has advantages such as flexible structure and low cost. In this paper, a 4-2-1 layout strain rotor force measuring instrument is designed for the aerodynamic load and wind tunnel test requirements of a certain type of helicopter. By establishing a mechanical model to clarify the relationship between input and output forces, the structural design and analysis (including the performance of the flexible rod and the strength check of the bolts) are completed, and static finite element simulation is carried out. A six-dimensional force calibration system is built to conduct static calibration tests, and performance is optimized through decoupling compensation. The average measurement errors in each direction are 0.03 %, 0.032 %, 0.006 %, 0.142 %, 0.076 %, and 0.0436 %, respectively. Theoretical, simulation and experimental verification show that this force measuring instrument has good force measurement performance and practical application feasibility.

Accurate monitoring of high-frequency upset force during friction stir welding (FSW) is a critical step for optimizing welding process parameters and ensuring joint quality. However, traditional platform-type force gauges cannot measure the upset force in the bobbin tool FSW (BT-FSW) process, which poses a technical challenge. To resolve this issue, a high-frequency spindle-integrated rotational piezoelectric testing system (SIR-PTS) mounted on the equipment spindle was designed. This system uses piezoelectric sensors as measuring elements and comprises a force gauge, a built-in signal conditioning circuit, and monitoring software. First, a theoretical mechanical model under rotational conditions was established to determine the dimensional parameters of the piezoelectric quartz wafers. Subsequently, an ANSYS finite element simulation was utilized to analyze the static structural characteristics and dynamic response of the testing system. Meanwhile, a modular hardware circuit integrating charge conversion, filtering, and wireless transmission functions was developed. A series of verification experiments was conducted to evaluate the system's performance. The experimental results demonstrate that the system exhibits a static linearity error of 0.64% and a repeatability error of 0.34%. Its main direction natural frequency is 2082.52 Hz, which meets the requirements of high-frequency dynamic testing. These results confirm that the system can realize high-precision, real-time dynamic monitoring of upset force in BT-FSW processes.

In wind tunnel tests of large-scale rotorcraft (with a dead weight of 200 kN class), the superposition of initial load and six-dimensional aerodynamic loads requires the measurement system to adopt sensors with a wider range, which sacrifices the accuracy of aerodynamic parameter acquisition. To address this issue, this paper innovatively proposes a multi-dimensional force measurement method based on load balancing. By separating the measurement processes of initial gravity and aerodynamic loads, high-precision measurement of aerodynamic loads is achieved after balancing the model weight. Based on this method, a scaled verification prototype of the Load-Balanced Force Measurement System (LBFMS) is developed, which consists of a Load Balancing System (LBS) and a Force Measurement System (FMS). Its six-dimensional force measurement ranges are F-x = 20 kN, F-y = 10 kN, F-z = 20 kN, M-x = 12 kN & centerdot;m, M-y = 18 kN & centerdot;m, and M-z = 7 kN & centerdot;m. The LBS adopts a composite design of hydrostatic support and low stiffness springs to realize heavy load balancing above 20 kN while minimizing load sharing interference. The FMS ensures the uniqueness of force transmission through a six-point statically determinate layout. Simulation and experimental results show that the load fluctuation of the LBS in the lift direction is only 0.0065 % FS. In the three-direction force calibration, the output difference of the sensitivity coefficient between LBFMS and FMS is <0.64 %FS, and the maximum difference of nonlinearity and repeatability errors is <0.23 %. Under six-dimensional force composite loading, the output difference of the sensitivity coefficient in each dimension is within 0.30 %FS, and the maximum difference of nonlinearity and repeatability errors is <0.12 %, indicating highly consistent measurement performance between the two systems. This study achieves multi-dimensional force measurement under 20 kN load balancing without sacrificing the accuracy of the original system. It verifies the feasibility of the proposed method and provides an important technical solution for high-precision force measurement in wind tunnel tests of large-scale rotorcraft.

PurposeThe six-component rotor balance is a core force-measuring component for evaluating rotor mechanical properties and advancing helicopter aerodynamics research. To meet the specific aerodynamic design requirements of a certain helicopter model, this study aims to develop a high-performance piezoelectric six-component rotor balance that addresses the demands of high rigidity and dynamic response in helicopter rotor tests, and to systematically verify its measurement reliability under complex working conditions.Design/methodology/approachThis paper adopts a theoretical modeling-finite element simulation-experimental validation integrated approach. First, based on the point hypothesis and rigid body hypothesis, the mechanical model of the piezoelectric rotor balance was simplified to clarify its fundamental force-measuring principle and force transmission mechanism. A three-component piezoelectric sensor (TPS), designed and fabricated using the piezoelectric effect, was used as the core measurement unit. A 3D model of the balance was established for finite element analysis (FEA), focusing on static performance under full load, natural frequency characteristics and force-measuring stability across different environmental temperatures. Subsequently, a dedicated six-dimensional force static calibration test bench was constructed to conduct static performance calibration. Furthermore, composite loading tests and temperature variation tests (223-323 K) were carried out to validate the balance's performance under simulated complex rotor test conditions.Findings FEA results demonstrate that the first-order natural frequency of the developed balance reaches 1,072.3 Hz, confirming its excellent dynamic performance, and its force-measuring characteristics exhibit high stability with temperature variations. Static calibration tests show that the balance meets all test requirements, with a maximum linear error of only 0.55%. Under composite loading conditions, the balance maintains high measurement accuracy, with a maximum deviation of 1.2%. Temperature variation tests verify the FEA results: the maximum measurement error is 0.31% at 223 K and 0.17% at 323 K. Collectively, the balance achieves stable working status and reliable force-measuring performance within the temperature range of 223-323 K.Research limitations/implicationsThis study contributes a novel piezoelectric six-component rotor balance tailored specifically for helicopter aerodynamic experiments, which features superior rigidity and dynamic performance compared to conventional alternatives. The originality lies in the design of a TPS as the core measurement module, combined with a rigorous theoretical and experimental framework that validates the balance's performance under extreme temperature and composite loading conditions. The proposed balance fills the gap in high-dynamic-performance force-measuring devices for helicopter rotor tests and provides a reliable experimental basis for the aerodynamic design and optimization of the target helicopter model.Practical implicationsThe helicopter piezoelectric rotor balance can be directly applied to helicopter rotor test benches, meeting high-precision, high-stability force-measuring needs, reducing test equipment maintenance costs and providing references for high-precision force-measuring device development in aerospace, with engineering transformation and commercial potential. Social implicationsIt helps improve helicopter aerodynamic design and safety, indirectly ensuring flight safety, promoting technological upgrading in the aerospace industry, supporting technical innovation in related fields and driving the development of high-precision sensor and test equipment industrial chains.Originality/valueA six-component piezoelectric helicopter rotor balance test system is proposed. The effect of ambient temperature on the performance of rotor balance is studied. The helicopter rotor balance can work stably under compound loading conditions. Six-way static calibration test of rotor balance is carried out on the test system. Nonlinear/repeatability error and interphase interference all meet test requirements.

In order to tackle the difficulties of force measurement in long-domain loads of transmission shafting, as well as the challenges of simultaneously measuring multi-dimensional forces, static forces, and dynamic forces, an eight-measuring-point piezoelectric force-measuring instrument for force sensing in large ship transmission shaft systems is put forward. This represents a novel measurement approach. The force-measuring instrument is serially connected between the bearing pedestal and the fixed base. All forces generated by the transmission shaft system will be transmitted to the force-measuring instrument, and the static and dynamic six-dimensional forces are monitored in real-time by the force-sensing elements. Firstly, a new multi-support mechanical model based on the theory of elasticity is proposed, which offers a reliable theoretical foundation for the design and fabrication of the force-measuring instrument. Secondly, three-dimensional simulation models are established according to two different structural plans of the force-measuring instrument, and static mechanical analyses are carried out. In light of the structure and measurement range requirements of the force-measuring instrument, a static/dynamic calibration system for the force-measuring instrument is designed. Finally, a feasibility analysis and effectiveness test are performed on this new configuration. Through static/dynamic calibration experiments, the static and dynamic performance of force-measuring instruments with different structures (linear errors in each direction, repeatability errors, and natural frequencies) are obtained. By comparing the experimental results of force-measuring instruments with two different structures, the optimal configuration is selected for decoupling compensation, so as to achieve the best force-measuring ability of the force-measuring instrument. The linear error of the force-measuring instrument is less than 0.426%, and the repeatability error is less than 0.857%. The maximum improvement effect of decoupling compensation on measurement accuracy can reach 97.03%, the maximum measurement accuracy is 1.627%, and the minimum is 0.066%. Moreover, a series of calibration tests under complex working conditions were carried out to obtain the all-round static performance of the force-measuring instrument, with a linear error of less than 0.108%. The experiments have verified the practical feasibility and effectiveness of the force-measuring instrument, providing a new perspective for the force measurement of the long-span transmission shaft system.

The rotor system is a crucial component in the design and manufacture of helicopters. The accurate measurement of the output aerodynamic forces of the rotor system is indispensable to ensure high maneuverability and stability of the aircraft during service. To overcome the challenge of measuring the high-frequency harmonic loads on rotor blades due to their rotation, this article presents a rotor balance based on the piezoelectric measurement principle for precise the measurement of rotor dynamic loads. This device adopts a planar four-point support structure, featuring high precision, high rigidity, and fast response speed. By establishing a theoretical mechanical model of the piezoelectric balance and analyzing and decoupling its force state, the main factors influencing its performance variations are obtained. Second, in response to the uneven height issue existing in the assembly process of piezoelectric components, ANSYS simulation software was utilized to conduct overall parameter optimization and investigate the influence of assembly errors. Additionally, modal and static simulation analyses were carried out to finalize the overall optimization plan for the measurement device. Additionally, a self-developed three-direction force calibration device is employed to conduct static calibration and exploration of the natural frequency of four piezoelectric elements and the balance system. The static and dynamic performance of the rotor vector measurement system has been verified through experiments, and it meets the test requirements. The linearity and repeatability errors of all forces and moments are less than 1.00%, and the natural frequency is higher than 900 Hz. This device can offer theoretical basis and reference for subsequent high-precision measurement of rotor systems and the design of balances.

The effective functioning of a vanadium redox flow battery (VRFB) is heavily dependent on the consistency of its electrolyte distribution. Ultrasound technology has been recognized as a promising method for enhancing the mixing and reaction rates of electrolytes by leveraging acoustic thermal, acoustic cavitation, and acoustic streaming effects. However, previous research on ultrasonic impact on batteries often combined multiple acoustic effects, making it unclear how specifically acoustic streaming affects battery performance. In this study, we introduce localized acoustic streaming to improve electrolyte uniformity in VRFB. By isolating the thermal effect from other ultrasonic effects, we demonstrate that acoustic streaming alone can boost cell energy efficiency by 2.9 %. Additionally, electrolyte uniformity in the negative electrode significantly increases from 0.22 to 0.53, marking a 141.0 % enhancement ratio. This effectively reduces concentration polarization within the battery, thereby enhancing its voltage efficiency. In addition, the energy consumption of an intermittent ultrasonic application strategy is reduced by 90 % when compared to continuous ultrasonic application. The study provides a new paradigm to promote the localized uniformity of electrolytes, leading to potential impacts in enhancing battery performance.

Energy harvesting technology plays a remarkable role in enabling self-powered wireless electronics, sensor networks, and the Internet of Things. One of the key issues hindering the application of existing piezoelectric rotational energy harvesters is how to enhance their structural robustness and environmental adaptability. Here, a tunable rotational energy harvester with a stress-uniform piezoelectric vibrator utilizing an air-solid coupling chamber was proposed. The energy harvester introduces an air-solid coupling chamber to transform the excitation force into air pressure to provide uniform stress on the piezoelectric vibrator, which can effectively avoid the damage of stress concentration. A combination of theoretical, numerical, and experimental approaches was employed to validate the structural feasibility and operational principles of the energy harvester. Results demonstrate that the peak voltage and effective frequency can be regulated by the combination of excitation ratio, chamber height, and excitation distance. A peak output power of 8.53 mW was obtained from the energy harvester at a load resistance of 18 k Omega. The 220 mu F, 470 mu F, and 1000 mu F capacitors were saturated at 7.73 V, 7.55 V, and 6.99 V during 25 s, 50 s, and 100 s, respectively. Furthermore, the energy harvester successfully demonstrated sustainable power generation capabilities by continuously illuminating an array of 250 LEDs and simultaneously powering both a light strip and a digital thermometer.

Wind tunnel balances are essential force measuring equipment for aerospace and other high-end equipment in wind tunnel test, which not only needs excellent static performance, but also needs good high-frequency response ability. An assembled wind tunnel balance and its calibration test system based on four triaxial-force piezoelectric sensors were designed according to the aerodynamic test requirements of an aircraft. The overall test system mainly consists of an assembled wind tunnel balance, calibration platform, vertical loading mechanism, lateral loading mechanism, standard force transducer and charge amplifier, data acquisition card, computer and acquisition software. The assembled wind tunnel balance consists of four high-stiffness triaxial-force piezoelectric sensors, upper/down plates and erection bolts. In response to the assembly issues of wind tunnel balances, the proposition was put forward that the preload torque of erection bolts would impact the measurement performance of the assembled wind tunnel balance. It is hoped to seek an effective approach to enhance the measurement performance of the wind tunnel balance starting from the structure itself. Based on this expectation, the measurement theoretical model and simulation three-dimensional model of wind tunnel balance were constructed, and the modal and static simulation analysis were also carried out. The performance calibration of four triaxial-force piezoelectric sensors was carried out, the overall scheme design of the measurement system was completed, and the test system of the assembled wind tunnel balance was built for the balance performance research. The influence of preload torque of different erection bolts on the measurement performance of the preload wind tunnel balance was studied, and the best preload torque suitable for the balance was explored to make the force measurement performance of the preload wind tunnel balance optimal. The static and dynamic performance of the test system meet the test requirements, with excellent linearity and repeatability, and the best combination of preload torque of the erection bolt was determined. The linear error of axial force was less than 0.258 %, and the linear error of torque was less than 0.562 %. The test proves that adjusting the preload torque of the erection bolts can effectively improve the static performance of the wind tunnel balance from the structure itself, which provides an effective new idea for scholars to study how to improve the performance of the wind tunnel balance. And, the first natural frequency of the wind tunnel balance was 1062 Hz, which was only 8.4 % different from the simulation result. It can realize the accurate measurement of the aerodynamics of the aircraft.

Wind tunnel tests are crucial for evaluating aerospace vehicle performance during development. However, existing force measurement systems struggle with large-scale, high-load test models. This study proposes a large, high-stiffness wind tunnel dynamometer using dual multipoint distributed force-measurement units. A mechanical model based on point-support theory was established to derive input-output force/torque relationships, enabling calculation of structural dimensions and sensor ranges. A 3-D simulation model validated the system's structural strength through static analysis. Independent calibration of each unit ensured reliable force measurement, reducing errors. A custom six-dimensional calibration device was designed, verified via finite element analysis, and used for unidirectional force calibration and dynamic testing. The dynamometer achieved static performance meeting design specifications (linearity error <= 0.3% for forces, <= 0.6% for torques; repeatability error <= 1% ), with a maximum linearity error of 0.335% . Decoupling compensation further enhanced six-dimensional force/torque measurement accuracies to 0.086% -1.627%, demonstrating up to 92.65% improvement. Experiments confirmed the model's theoretical validity, simulation accuracy, and applicability to large-scale, high-load, and high-frequency scenarios. This solution addresses critical gaps in modern wind tunnel testing for large aircraft models.

To address the technical challenge of directly measuring the aerodynamic loads of large-sized and heavy aircraft models in hypersonic wind tunnel tests, this paper has developed a 2400 mm sealed piezoelectric gauge balance to meet the aerodynamic measurement requirements of large aircraft models. The piezoelectric gauge balance consists of two groups of force-sensitive elements (a total of 8), and adopts a sealed structure to protect the forcesensitive elements and avoid environmental damage, overcoming the problems of insufficient stiffness and susceptibility to temperature interference in traditional strain gauge balances. The 2400 mm large size fills the research gap of similar gauge balances. Based on the piezoelectric effect, a gauge balance structure composed of 8 three-component piezoelectric sensors is designed, and a piezoelectric coefficient matrix is established. Through simulation analysis, the structural strength of the piezoelectric gauge balance is evaluated. A calibration platform is built, and static and dynamic calibrations are carried out, analyzing performance such as linear error, repeatability, and inter-channel interference. Through decoupling matrix compensation, the inter-channel interference is reduced by up to 96.15 %. The measurement errors of the decoupled drag, lift and pitch moment directions are 0.015 %, 0.140 % and 0.065 %, respectively, and the maximum improvement effect reaches 106.5 %. Long-term effectiveness verification is conducted, and the life of the gauge balance is recalibrated after 9 years, proving that the piezoelectric gauge balance has long-term effectiveness. A largesized sealed piezoelectric gauge scheme is proposed, providing a new idea for wind tunnel force measurement of large aircraft models; the feasibility and long-term stability of the piezoelectric gauge balance in large-scale scenarios are verified, providing technical references for the development of related equipment.

According to the characteristics of the change of the mass/centroid and the testing requirements of thrust vector during the operation of solid rocket motor, a thrust vector control test platform based on a mass/centroid adjustable spoke engine model was proposed. The test bench is composed of a three- dimensional force calibration loading device, a vector force simulation loading device, an engine model with a mass/centroid adjustable structure and a multipoint combined piezoelectric dynamometer. The theoretical mechanical model of the test bench was established, and the mechanical analysis of the stress state of each piezoelectric sensor was carried out. By using finite element simulation, the stress simulation analysis of the key device structure in the test bench is researched, and the overall design of the test system was also completed. A horizontal thrust vector test system was built to simulate vector force loading experiments of centroid change. And, the least square method was used to estimate the error and calculate the linearity of the experimental data. According to the results of vector force deflection simulation loading experiment show that the static and dynamic performance of the thrust vector control test bench meet the experiment requirements. The thrust vector control test bench has good linearity and repeatability, the error is <1.00 %, and the interphase interference is <2.00 %, which can realize the high-precision measurement of the thrust vector of solid rocket motor. What’s more, in the case of simulating the change of mass/center of engine, the thrust vector test system can also maintain a good static performance in each direction, and the measurement error of X-direction is <0.5 %, Y-direction is <2.85 %, and Z-direction is <1.06 %.

PurposeThe purpose of this study is to address the progressively increasing accuracy requirements for force measurement in the manufacturing and operation of modern mechanical equipment as well as the development of high-end equipment. Focusing on the four-fulcrum dynamometer - a novel structure increasingly applied in critical force measurement scenarios - this research emphasizes that the configuration of its four force measurement units serves as a crucial factor affecting the dynamometer's force measurement performance.Design/methodology/approachA mechanical model was established based on the structure of the four-fulcrum dynamometer, and output performance calibration experiments were conducted. The sparrow search algorithm-backpropagation (SSA-BP) neural network was constructed using the existing experimental data and verified. The optimization objective was to minimize the output fluctuation of multipoint loading within the fixed loading area of the dynamometer. Relying on the favorable nonlinear optimization characteristics of the BP neural network, the SSA was adopted to optimize the weights and thresholds of the BP neural network, addressing the issue of the BP neural network getting trapped in local optima. The output model of the dynamometer under different spans and different point loadings was established, and enabling predictions across multiple spans.FindingsThe prediction results indicate that the output performance within the fixed loading area of the dynamometer gradually diminishes with the increase in the sensor span, and the output fluctuation reduces from a maximum of 241.9 N (4.8% FS) to 57.99 N (1.15% FS), signifying a remarkable enhancement in performance. The maximum error is 28 N, accounting for 0.57% of the full scale, which confirms the high accuracy and feasibility of the network. Consequently, on the condition of satisfying the structural stability of the dynamometer, the arrangement span of the sensor should be augmented. This approach shortens the experimental design process and saves a considerable amount of variable-span experimental procedures. The verification results of the network output confirm that the network accuracy satisfies the usage requirements, with the experimental results exhibiting high credibility.Originality/valueThis study provides a methodological foundation for the design of four-fulcrum dynamometers and the enhancement of force measurement accuracy.

The wind tunnel test balance of hypersonic vehicles is a crucial force measurement component for facilitating the aerodynamic optimization design of the aircraft. In response to the operational requirements of large-area loading, significant load application, and high-frequency excitation, an eight-point distributed wind tunnel piezoelectric balance (ED-WTPB) structure and its static calibration system have been proposed. Eight three-component piezoelectric force-measuring units (PFUs) are horizontally distributed within a long and narrow rectangular surface area. According to the point hypothesis theory and the force/moment balance theory, the mechanical model of the ED-WTPB is simplified, obtaining the relationship between the component forces received by each piezoelectric force measurement unit and the input force value, and determining the fundamental force measurement principle of the ED-WTPB. A 3-D model of the ED-WTPB is established, and finite element simulation analysis is performed using simulation software to verify the basic structural strength and calculate the inherent frequency of the ED-WTPB, ensuring that the proposed ED-WTPB structure satisfies the requirements of the wind tunnel tests for hypersonic vehicle models. Simultaneously, a static/dynamic calibration system for the ED-WTPB is designed. Through static/dynamic calibration tests, the static/dynamic performance of the ED-WTPB is obtained. The maximum linear error is 0.117%, the maximum repeatability error is 0.513%, and the first-order inherent frequency is 456.54 Hz. Both the static and dynamic performances meet the design requirements. In addition, variable loading point tests in different directions are carried out to obtain the static performance of the ED-WTPB under different working conditions, evaluating its measurement reliability and stability. The feasibility of the ED-WTPB is demonstrated, providing novel ideas for the design and manufacturing of large-sized wind tunnel balances.

Harvesting energy from rotational motion using piezoelectric mechanism has attracted significant attention for powering wireless sensors over the past decade. To improve structural robustness and environmental adaptability of existing piezoelectric rotational energy harvesters (PREHs), an indirectly excited piezoelectric rotational energy harvester utilizing a flexible diaphragm to facilitate magnetic coupling (FD-PREH) was proposed. Unlike the traditional PREHs, the proposed FD-PREH introduces a flexible diaphragm to convert the excitation force into gas pressure acting uniformly on the surface of the piezoelectric transducer for electric output. This method reduced significantly the damage possibility of piezoelectric transducer under unexpected high-intensity impacts and torsions. The feasibility of the structure and principle of the FD-PREH was demonstrated through theoretical analysis, fabrication and experimentation. The results indicated the structural parameters of excitation ratio, radius ratio, and thickness ratio all had a remarkable influence on the peak voltage and effective rotational speed of the FD-PREH. With the increase in load resistance, there was an optimal load resistance of 18 k Omega at which the RMS power reach a maximum of 0.94 mW. Meanwhile, the energy harvester charged the 100, 220, 470, and 1000 mu F capacitors to the voltages of 6.92, 6.9, 6.35, and 6.01 V in about 10, 15, 20, and 25 s, respectively. More importantly, the FD-PREH could simultaneously and continuously power at least 250 LEDs and it also provides real-time power for calculators and thermometer, showing its potential for sustainable energy generation.

The six-dimensional force measurement technology of aircraft models is of great significance to the development of aviation. Aiming at the testing requirements of large aspect ratio aircraft models and the limitations of the existing support methods, this paper proposes a rod-supported six-dimensional force measurement system for large aspect ratio aircraft models embedded with an image recognition method. Firstly, the principle of sixdimensional force measurement under the rod support method is derived. Then, a piezoelectric tension sensor was developed and its performance was tested to realize the accurate acquisition of the force value on the rod. Meanwhile, the optimal algorithm was determined to extract the spatial angle of the support rod by comparing different image recognition algorithms. Finally, the test system was built and the six-dimensional force test was performed on the aircraft model, and the decoupling compensation was performed on the test data. The experimental results show that the nonlinearity error of the piezoelectric sensor is lower than 0.3%, the repeatability error is lower than 0.4%, and the accuracy of the angle recognition algorithm reaches 0.01 degrees. In the model six-dimensional force calibration test, most of the nonlinear errors of each dimension are lower than 0.89%, and the repeatability errors are all lower than 0.46%. The test system can meet the static six-dimensional force test requirements of the aircraft model, and at the same time, it verifies the feasibility of the image recognition algorithm in the rod support system, which provides a new solution for the measurement of sixdimensional force of the aircraft model with large aspect ratio.

Harvesting energy from wind-induced vibration utilizing piezoelectric mechanism has attracted much attention for enabling energy-autonomous wireless sensor systems over the past decade. To offer a promising solution for low reliability, poor environmental adaptability and narrow operating bandwidth of existing piezoelectric wind energy harvesters, a wind-isolated galloping energy harvester with an embedded piezoelectric transducer (EPT-WGEH) is proposed in this paper. Unlike previous most directly-excited piezoelectric wind energy harvesters, the EPT-WGEH was characterized by an indirectly-excited shelter-structure, which isolates the embedded piezoelectric transducer (EPT) from the flow environment. Meanwhile, the horizontal swing of the hollow cylinder and the elastic pendulum beam is transformed into the vertical swing of the EPT mounted in the hollow cylinder under wind excitation. Therefore, this 2-DOF indirectly-excited EPT-WGEH could possess both high reliability and small volume. A CFD simulation model was established to analyze the influence of structural parameters on the vibration characteristics of EPT-WGEH. To verify the feasibility of the principle and design regarding the proposed EPT-WGEH, a prototype of the EPT-WGEH was fabricated and tested in terms of electrical output and operating bandwidth. The results showed that the length of elastic pendulum beam, proof mass, and wind speed brought significant effects on the electrical output, minimum working wind speed and operating bandwidth. The maximal output voltage increased with the decreasing length of elastic pendulum beam or the increasing proof mass. Meanwhile, there existed some optimal combinations of parameters to minimize the minimum working wind speed of EPT-WGEH. Besides, the optimal output power of EPT-WGEH could reach 2.4 mW at load resistance of 600 kΩ. The EPT-WGEH could light up 75 series-connection commercial blue LEDs simultaneously at the wind speed of 15 m/s and demonstrated its practical power supply capability by charging capacitors.

The accurate measurement of thrust vector is very important to improve the life and safety of aircraft engine. In order to meet the requirements of thrust vector test of a solid rocket engine and overcome the contradiction between large thrust (>50 kN) and high-frequency response (>> 30 Hz)/high precision measurement (<3%), a thrust vector control test system utilizing a four-point support piezoelectric dynamometer (FSPD) and a deflected flange structure was proposed. The test system mainly consists of a four-point support piezoelectric dynamometer and some vector force simulation loading devices. The theoretical mechanical model and the thrust vector control test system was set up to study the performance of solid rocket engine. Firstly, the piezoelectric elements and four-point support piezoelectric dynamometer were calibrated by the three-direction force calibration loading device. Secondly, the rationality and feasibility of the thrust vector control test system were proved by the simulated loading experiment. The research results show that the static and dynamic performance of the test system meet the test requirements, and it has good linearity and repeatability, errors are less than 1.00 %, and interphase interference is less than 2.00 %. The measuring system proposed in this paper provides a new idea for the accurate measurement of vector force with large load and high-frequency response.