Acceleration compensation of a novel piezoelectric balance for the short duration impulse measurement: a time series analysis approach

A novel piezoelectric balance was developed to measure the six-component forces for the complex aircraft scaled model in the impulse combustion wind tunnel at a short duration airloads Mach number of 5. The piezoelectric balance using four triaxial piezoelectric load cells yields the high stiffness, sensitive and good dynamic response characteristics. The dynamic model-balance system was built to analyze the vibration characteristic. The time series analysis approach was developed on the basis of the system transfer function and the natural frequency, and the accelerated forces which induce the airloads overshooting oscillations had been obtained by the second order derivatives function. The experimental results have shown that the problem of overshooting oscillations effect of the impulse can be effectively solved by the acceleration compensation technology for the complex test model with the novel piezoelectric balance

A Novel Strategy to Eliminate the Influence of Water Adsorption on Quartz Surfaces on Piezoelectric Dynamometers

Piezoelectric dynamometers are out of use in high humidity. Experimental results showed that piezoelectric coefficients measured by the force-induced charges method initially fluctuated in a small range and then was unstable, and they could not be measured at high relative humidity (RH). The traditional shielding method-insulation paste was not quiet convenient, and it even added the weight of piezoelectric dynamometers. In this paper, a novel strategy that eliminates the influence of water adsorption with quartz surfaces on piezoelectric dynamometers was proposed. First, a water-quartz model was developed to analyze the origin of the RH effect. In the model, water vapor, which was adsorbed by the quartz sheet side surface, was considered. Second, equivalent sheet resistor of the side surface was researched, while the relationship of the three R’s (Roughness, RH, and Resistor) was respectively discussed based on the adsorption mechanism. Finally, fluorination technology was skillfully adapted to each surface of quartz sheets to shield the water vapor. The experiment verified the fluorination strategy and made piezoelectric dynamometers work in high humidity up to 90%RH successfully. The results showed that the presented model above was reasonable. In addition, these observations also drew some useful insights to change the structure of piezoelectric dynamometers and improve the properties

A Novel Dynamic Method to Improve First-order Natural Frequency for Test Device

It is important to improve the natural frequency of test device to improve measurement accuracy. First-order frequency is basic frequency of dynamic model, which generally is the highest vibration energy of natural frequency. Taking vector force test device (VFTD) as example, a novel dynamic design method for improving first-order natural frequency by increasing structure stiffness is proposed. In terms of six degree-of-freedom (DOF) of VFTD, dynamic model of VFTD is built through the Lagrange dynamic equation to obtain theoretical natural frequency and mode shapes. Experimental natural frequency obtained by the hammering method is compared with theoretical results to prove rationality of the Lagrange method. In order to improve the stiffness of VFTD, increase natural frequency and meet the requirement of high frequency test, by using the trial and error method combined with curve fitting (TECF), stiffness interval of meeting natural frequency requirement is obtained. Stiffness of VFTD is improved by adopting multiple supports based on the stiffness interval. Improved experimental natural frequency is obtained with the hammering method to show rationality of the dynamic design method. This method can be used in improvement of first-order natural frequency in test structure

Research on Dynamic Calibration of Piezo-two-dimensional Force Sensor

Abstract: Based on the piezoelectric effect of piezoelectric quartz crystal, a two-dimensional force sensor with good dynamic characteristics is designed, whose sensitive component is single-cut piezoelectric quartz wafers, and it realizes the measurement of force by measuring the charge which is generated by piezoelectric quartz crystal. This paper analyzes measurement principle of the sensor based on the mechanics of materials and gives structure of the sensor. Dynamic calibration system of the sensor is designed, and the curves between sensor output and input are obtained by dynamic calibration experiment and data analysis. This article provides a new way of thinking for in-depth study in dynamic calibration of the sensor and accurate measurement. Copyright © 2013 IFSA

Research on the Structure and Signal Transmission of Rotary Piezoelectric Dynamometer

Cutting force real-time monitoring has become an increasing prominent role in high precision mechanical parts processing. A new type of cutting force dynamometer which is able to be mounted on the spindle of machine tool is proposed in this paper. At first, it is proved theoretically that the charge quantity can be obtained through measuring the induced charge quantity generated by electrostatic induction. Then the feasibility of this method is verified by an experiment. X0°-cut wafer and Y0°-cut wafer of α piezoelectric quartz are analyzed by ANSYS software separately and the distribution regularity of the polarized charge when piezoelectric quartz wafer surface is subjected to force or torque is obtained. On the basis of the above analysis, a kind of piezoelectric three-component dynamometer is designed. It can measure cutting depth resistance, feed resistance and torque with only two X0°-cut quartz wafers and two Y0°-cut quartz wafers

Research on the Dynamic Error and Acceleration Compensation for the Piezoelectric Sensor

Piezoelectric force sensors are used in more and more industries and areas for the monitoring of the production process or testing products' performance. In some high-precision testing fields, the dynamic measurement performances of the test system itself have to be examined. Based on the dynamic response mathematical model of test system itself, this paper studies the dynamic measuring acceleration error compensation method. Firstly, according to the motion differential equation of the test system, the dynamic response transfer function is built and the root cause of the test system dynamic testing error is studied. Then the modal parameters of the system are obtained using the experimental modal analysis method and a deterministic response transfer function is established. The acceleration impact item is separated out by the method of separation of variables and weight coefficient method. Combining numerical differentiation, the expression used to calculate the acceleration is achieved. Finally, acceleration compensation experiment is done

Piezoelectric Sensor of Control Surface Hinge Moment

Based on the theory of piezoelectricity, a new sensor of control surface hinge moment with high linearity which uses piezoelectric quartz crystal as sensitive element is studied. It realizes the measurement of force by measuring the charge which is generated by piezoelectric quartz crystal that is integrated inside of sensor. In order to simulate the interaction between airfoil and airflow under the steady state, ANSYS is used to analyze the stress of airfoil in the air. ANSYS is also used to analyze potential distribution and electric field intensity distribution of piezoelectric quartz crystal which is under the action of force and moment, respectively. The measuring principle and design process of sensor are given in this paper, and the linearity and repeatability of sensor are obtained on the basis of experimental research and data analysis. The new sensor offers a new thinking for lucubrating and accurate measurement of hinge moment sensor

Study on a Method of Dynamic Response Function for the Piezoelectric Measurement System

Abstract: Some important areas use more and more piezoelectric force test systems, due to their high sensitivity and natural frequency. To study the dynamic testing performance of the system in the conditions of high natural frequency, one of the effective methods is establishing the mathematical model of dynamic response of test system. By improving specific algorithm of the conventional nonlinear modal fitting method, algorithm of transfer function which is aiming at this test system is deduced, and the transfer function of dynamic response is obtained by using amplitude and phase frequency response curve which is measured by using a piezoelectric test device and the curve is compared with the measured amplitude and phase frequency curve. The rise time, peak time and the overshoot of the step response of the test apparatus is obtained with the inverse Laplace transform. This paper provides a basis of objective evaluation for the dynamic performance of the test device. Copyright © 2013 IFSA