Design And Implementation Of Near Field Calibration Mechanical Scanning Control System

As the rapid growth of the underwater acoustic technology, various underwater acoustic transducer has shown up. Calibration would be needed after these transducer are produced.The calibration methods we use now need massive calibration area. Besides, it is difficult to test during calibration and inefficient. These methods are also susceptible to interference.This paper comes up with a new prospective for underwater acoustic transducer calibration. Using near acoustic holography to estimate the acoustic character of transducer in far field via the sound pressure data of the near-field transducer. To solve the problem of inaccuracy of spatial orientation during near field acoustic holography testing and long testing time, I designed the near field calibration mechanical scanning control system. This paper studies the basic principle of near field acoustic holography and deducts the simulation of the whole process to estimate the far field acoustic characters.This near field calibration mechanical scanning control system uses the servo motor of Delta and high precision screw and guide rail of THK, so that the mechanical scanning system could reach stepping precision. Acquire near-filed sound pressure data with data acquisition card of NI company. Using LabVIEW to design control interface, including using DLL dynamic link library technology to control the servo motor, designing collecting and storing through DAQmx, combining the two parts to accomplish a control interface which can measure sound pressure of all holography plane automatically. Setup of Motion control parameters and data acquisition of related parameters can be made on the control interface.The control interface can also show the motion status, waveform received and collected.Through testing the near field calibration mechanical scanning controlling system, using near acoustic holography to estimate the acoustic character of transducer in far-field via the sound pressure data of the near field transducer becomes possible. This proves the system meets the designing requirements and provides a reliable solution to calibrate near field transducers.