Radial vibration mode of the ultrasonic transducer

Modeling and experiment of ultrasonic transducer in the air medium, the frequency band of the ultrasonic sensor is generally narrow, which directly affects its detection performance for high-speed moving targets. In order to solve the narrow band of the ultrasonic sensor, a micro-miniature transducer can be used as an auxiliary receiver in the combined ultrasonic transducer to widen the receiving bandwidth of the combined transducer. The transducer is a flexural tension type of metal piezoelectric composite transducer, which is composed of two thin shape metal thin shells sandwiching a piezoelectric ceramic wafer (piezoelectric vibrator) polarized in the thickness direction. Under the excitation of the ultrasonic frequency alternating electric field, the high-impedance and small-radius stretching vibration of the piezoelectric vibrator is converted into a low-impedance, large-axis displacement of the thin metal shell cavity, and the ultrasonic wave is radiated to the air medium. Conversely, when the ultrasonic waves act on the transducer, the thin metal shell is deformed, which causes the piezoelectric vibrator to undergo radial stretching vibration and generate an alternating charge between the two electrodes. This is the basic working principle of the transducer as an ultrasonic generator and receiver. It is very suitable to make small displacement, light weight, large stroke micro-displacement drive and micro-small ultrasonic receiver with lower resonance frequency. An effects of the material and structural parameters of the ultrasonic distance transducer on its radial and longitudinal modes of vibration is a prerequisite for the design and fabrication of the transducer.

Radial vibration mode of the transducer

The radial vibration mode of the ultrasonic range finding sensor is closely related to the applied excitation electric field, the material and structural parameters of the piezoelectric vibrator between them is derived below. The piezoelectric vibrator is polarized along the Z-axis direction (ie, the axial direction), its radius is Ro, and its thickness is ho; the bottom of the rally is in the shape of a ring, its outer diameter is Ro, and its inner diameter is R, assuming alternating piezoelectricity field is applied to the two circular planes of the vibrator, and the stress vector T and the electric field strength vector E are independent variables, and the strain vector S and the electric displacement vector D are dependent variables, then the cylindrical coordinates ((r, 8, z) form The piezoelectric equation can be expressed where s is the elastic compliant constant matrix of the piezoelectric material under constant electric field conditions, d represents the piezoelectric strain constant matrix, and T is the free dielectric constant matrix of the piezoelectric material. The edge is bonded to the piezoelectric vibrator to form a metal piezo ceramic composite.it is axial resonant frequency of the transducer.

Since the height H of the housing is small, that is, the normal vibration of the ultrasonic distance measurement sensor can be studied approximately according to the symmetrical vibration of the circular thin plate sandwiched by the periphery. It is known that a circular thin plate is having a radius of R is symmetric about the Z axis, and the load applied to the boundary thereof is also symmetric about the Z axis, so the elastic curved surface of the thin plate must be symmetric about the Z axis. Therefore, analyzing the free vibration of the thin plate in the polar coordinate system can simplify this problem. Let the deflection of the circular thin plate at any instant t during the vibration process .then the free vibration differential equation is describing the peripheral sandwich type can be expressed.

Long range ultrasonic transducer

Ultrasonic transducer with physical properties