ADAPTIVE MECHANICAL FILTER FOR PIEZOELECTRIC ACCELEROMETER

When conducting dynamic tests, when simulating shock effects, the measurement system - from the sensor to the data acquisition unit is subject to significant overloads. In this circuit, the accelerometer is the most vulnerable link. Therefore, piezoelectric accelerometers have become widely used in measuring shocks as more reliable and durable, but they also have a number of disadvantages. Thus, under broadband vibration effects, excitation in the region of mechanical resonance is observed. That is, the material of the sensor crystal may not have an excessive mechanical load, but generate a large amount of output charge due to the resonance of the sensor. This increases the electrical signal and can lead to saturation or, in many cases, damage to the signal shapers and amplifiers following the sensor. The result of such modes of operation is the loss of data due to the displacement of direct current over time. There is often a shift of the zero level of the output signal. When piezoelectric elements are in resonance, there may be a relative displacement of the sensing element. This state of overload leads to the appearance of parasitic output charges, which leads to a change in the generated charge in a short period of time. Due to mechanical overload, under the action of high-intensity shocks, physical destruction of the sensor is also possible. In many cases, the use of mechanical filters made of viscoelastic materials, which are placed between the object of measurement and the piezoelectric accelerometer (sensor), prevents the undesirable consequences of these shortcomings and improves the process of measuring shocks. The use of mechanical filters made of viscoelastic materials makes it possible to significantly reduce the amplitude of oscillations of the piezoelectric accelerometer (over -12 dB) and shift its resonant frequency towards higher frequencies. That is, the use of mechanical filters significantly reduces the mechanical load on the sensor, which makes the process of measuring vibration (especially shock) more predictable.

A Theoretical and Empirical Investigation of Design Characteristics in a Pb(Zr,Ti)O3-Based Piezoelectric Accelerometer

A theoretical and experimental study on the design-to-performance characteristics of a compression-mode Pb(Zr,Ti)O3-based piezoelectric accelerometer is presented. Using the metamodeling to approximate the relationship between the design variables and the performances, the constituent components were optimized so that the generated electric voltage, representing sensitivity, could be maximized at different set values of the resonant frequency (25–40 kHz). Four kinds of optimized designs were created and fabricated into the accelerometer modules for empirical validation. The accelerometer modules fabricated according to the optimized designs were highly reliable with a broad range of resonant frequency as well as sufficiently high values of charge sensitivity. The fixed (or mounted) resonant frequency was between 16.1–30.1 kHz based on the impedance measurement. The charge sensitivity decreased from 296.8 to 79.4 pC/g with an increase of the resonant frequency, showing an inverse relation with respect to the resonant frequency. The design-dependent behaviors of the sensitivity and resonant frequency were almost identical in both numerical analysis and experimental investigation. This work shows that the piezoelectric accelerometer can be selectively prepared with best outcomes according to the requirements for the sensitivity and resonant frequency, fundamentally associated with trade-off relation.

THREE-DIMENSIONAL PIEZOELECTRIC ACCELEROMETER FOR MEASURING DYNAMIC PARAMETERS OF MOVING OBJECTS

Analysis of structural construction of existing three-dimensional accelerometers is carried out, in which due to the opposite direction of sensitivity vectors and direction of measured inertial force, they allow to measure only linear inertia and accelerations varying in relatively small limits. On the other hand, due to the presence of elements in them that create electromagnetic fields, their construction is somewhat complicated. In addition, in known accel-erometers, due to the absence of a measurement object position sensor and an electronic control circuit, the func-tionality of the accelerometer is limited, Due to lack of integrator for acceleration integration, speed measurement is not provided, Due to rigid attachment of piezoelectric sensing elements through their bases, during measurement they generate interference signals, The amplitude of which exceeds the amplitude of the useful signal, which does not ensure reliability of the measured acceleration or speed and due to the presence of sensitive piezoelectric ele-ments, Having higher rigidity and requiring relatively large mechanical forces for generation of signals during mo-tion of acceleration and speed measurement object in automatic mode, which reduces sensitivity of accelerometer. Invention proposes new design and control scheme of three-dimensional piezoelectric accelerometer for measure-ment of dynamic parameters of moving objects in automatic mode. Wherein providing the position sensor of the moving measurement object with a three-axis signal detection unit to determine a direction of motion with meas-urement of acceleration or linear velocity when the measurement object moves along the coordinate axis; With the help of differential operational amplifiers through pulse generators and integrators, Speed measurement is provided by damping piezoelectric elements when the measurement object moves along one of the coordinate axes; Across the other two axes, the generated interference signals by amplitude are significantly reduced by their redemption; Having a piezoelectric element in the structure in the form of two-layer flat plates with an excitation section and a sensor section; Which generates signals at fast-changing acceleration and speed of moving object, amplitude of signal and sensitivity increases in 4-5 due to generation of signal by sensitive elements in vibration excitation mode created in accelerometer. Mathematical basis for accelerometer control circuits, mathematical model of its functioning is developed, applica-tion of which increases sensitivity of measurement of linear accelerations and speeds of moving objects and expands functional capabilities.

Improvement of the Vibratory Analysis by Enhancement of Accelerometer Characteristics

In this work, the mathematical model suitable for the operating principle of the piezoelectric accelerometer is extracted then this model which connects the accuracy and the measurement error according of the frequency ration and the damping rate is validated by simulation. The model developed makes it possible to improve the performances of the accelerometer such as precision, sensitivity and reliability as well as to propose a new conception of the latter. A comparative study is made to show the importance of our results compared to literature, these results have showed that a suitable and appropriate choice of damping ratio develops the accelerometer parameters and enhances the vibratory analysis technique.