Development of methods for the estimation of the parameters of the sensor oscillation for testing automobile shock absorbes
Despite the fact that the domestic and foreign industry offers a wide range of motion and vibration sensors, built on various physical principles, the problem of creating such sensors, the most adapted to the specific test bench conditions of the suspension elements and vibration protection of cars, is relevant. When developing the vibration sensor, the following requirements were determined: the use of strain gauges in the sensing element; ensuring high accuracy of measuring the movements of the shock absorber rod (error not more than 3%); the ability to measure movements in the range from 0.1 to 150 mm in magnitude and from 0 to 10 Hz in frequency of change; ensuring high sensitivity and stability of readings throughout the measurement range; the ability to measure other linear and angular movements in a given frequency range; convenience and ease of installation on the tire and hydraulic pulsation stands; minor impact on the natural frequency of the object of measurement; simplicity and reliability of the design. To meet these requirements, it was necessary to theoretically justify methods for assessing the design parameters of the sensor, namely: the size of the sensing element and the cam, the stiffness of the coil spring. The geometric dimensions of the sensitive element (elastic cantilever beam of equal cross section) were determined from the condition of ensuring sufficient sensitivity when measuring small displacements and eliminating residual deformations with maximum deflection of the free end of the beam. As a result, a relation was derived with respect to any of the three parameters (length and thickness of the beam, place of the stick of the strain gauge), depending on what conditions are imposed on their limitations when developing the sensor. The cam profile was carried out according to the law of the Archimedes spiral, which provides a directly proportional relationship between the angle of rotation of the cam and an increase in its radius, therefore, direct proportionality between the normal deflection of the free end of the sensing element (beam) and the angle of rotation of the cam. The coefficient of rigidity of the coil spring and, consequently, its size is determined by the co-location of the natural frequency of the dynamic system of the sensor with the frequency of the measured oscillations. The developed oscillation sensor was implemented in metal and showed in the process of experimental studies the high accuracy of measuring shock absorber parameters.