Bezvesilna O. M., Tkachuk A. H. INSTRUMENTAL ERRORS OF PIEZOELECTRIC SENSORS USED IN AUTOMATIC WEAPONS STABILIZER SYSTEM

 

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Bezvesilna O. M., doctor of technical sciences, professor

Tkachuk A. H., PhD, associate professor

National Technical University of Ukraine "Kyiv Polytechnic Institute named after Igor Sikorsky", Ukraine

Zhytomyr state technological University, Ukraine

 

INSTRUMENTAL ERRORS OF PIEZOELECTRIC SENSORS USED IN AUTOMATIC WEAPONS STABILIZER SYSTEM

 

Weapons stabilizer is an automatic control system that provides combat vehicles with weapon targeting and stabilization in the target fire direction during oscillation of a moving armoured vehicle (AV) [1, 4]. To increase the effectiveness of fire during movement in all modern tanks and other combat vehicles, the main armament is stabilized by a special device referred to as a weapons stabilizer. AV oscillations are random and never dampen in motion. The amplitude of angular oscillations and oscillation frequencies are quite high [2]. The accuracy of shooting is mostly influenced by AV oscillations in the longitudinal plane, changing the angle of gun elevation, and angular oscillations in the horizontal plane, changing the traverse [3]. This leads to a significant displacement of the aiming mark towards the target and does not allow the gunner to keep it on target even with the most advanced power drives.

To increase the effectiveness of fire on the move, all modern combat vehicles are equipped with a special automatic device referred to as a weapons stabilizer system (WSS) [1]. Providing the accuracy improvement of measuring the mobile object’s acceleration, such as those used in a weapons stabilization system (WSS), is a great challenge. WSS effectiveness is mostly dependent on the accuracy and performance of the sensitive stabilizer elements and accelerometers. The modern stabilization systems, using spring, string, quartz, magnetic, and gyroscopic accelerometers cannot provide the required speed of response and accuracy [1,3].

Therefore, the urgent scientific and technical challenge is to improve the accuracy and speed of response when measuring the acceleration values by experimental investigations of a piezoelectric sensor (PS) for the automatic weapons stabilization system.

To analyze the PS errors, the following classification should be introduced: by the error factors (the methodical factor, caused by an imperfect measurement method or a mismatched model, and the instrumental factor, caused by measuring device properties), by their effects (static and dynamic); by their repeatability (the random errors, varying randomly in sign and value during repeated measurements of the same value, and the systematic errors, remaining during the same measurements either constant or varying according to expectations) [13, 3].

The instrumental PS error is determined as the sum of errors of all values that directly affect the final output of accelerometer [2]. The basic working formula of converting acceleration to voltage is as follows:

                                                             (1)

where:  is the output PS voltage; gz is the gravitational acceleration (GA); dij is the piezoelectric modulus; m is the mass of PS and IM; CPS is the electric capacity of PS.

The true value of GA is determined by the formula:

                                                             (2)

The relative error of output signal equals to the sum of multiplications of relative parameter errors by parameter exponents:

                                                (3)

The error values were determined in [2] and summarized in Table 1.

Table 1. The PS instrumental errors

¹

Components of instrumental error value

Error value

1

Voltage variation,

1.1·10-4

2

Piezoelectric variation,

0.0059·10-4

3

PS electrical capacitance variation,

0.22·10-4

4

Mass variation,

1.3·10-4

Cumulative instrumental error

1·10-6

 

Conclusions

The research enables to solve a relevant and complex scientific and technical task that is paper identifies and examines the fundamental errors of piezoelectric accelerometers. Reduction of each type of error is suggested by certain measures (the instrumental error is 0.1×10−5 m/s2). The composition and structure of PS errors are defined. The main of them are considered and calculated. The instrumental error does not exceed 0.1×10−5 m/s2.

References:

1.       Bezvesilna Î. Corrected gyrocompass synthesis as a system with changeable structure for aviation gravimetric system with piezoelectric gravimeter / O. Bezvesilna, A. Tkachuk  // Aviation (Vilnius, Lithuania). – 2014. – ¹18(3). – Ð.134-140.

2.       Bezvesilna Î. Design of piezoelectric gravimeter for automated aviation gravimetric system / O. Bezvesilna, I. Korobiichuk, A. Tkachuk, R. Szewczyk,  M. Nowicki // Journal of Automation, Mobile Robotics & Intelligent Systems. –2016. – Vol. 10, Issue 1. – P. 43-47.

3.       Bezvesilna Î. Piezoelectric Gravimeter of the Aviation Gravimetric System / O. Bezvesilna, I. Korobiichuk, A. Tkachuk, R. Szewczyk,  M. Nowicki // Advances in Intelligent Systems and Computing. – 2016. – ¹440. – Ð.753-761.

4.       Bezvesilna Î. Stabilization system of àviation gravimeter / O. Bezvesilna, I. Korobiichuk, A. Tkachuk, M. Nowicki // International Journal of Scientific & Engineering Research. – 2015. – Vol.6. - Issue 8. – P. 956-959.