Study On Rejecting Ultrasonic Crosstalk Based On Chaotic Pulse Sequence Width Modulation

Ultrasonic crosstalk, which seriously affects the precision of range and reduces the work efficiency, often occurs when multiple transducers work simultaneously. To eliminate the phenomenon of ultrasonic crosstalk, many studies have been done. Such methods are classified into two categories, one is heuristics based soft-processing method which includes error eliminating rapid ultrasonic firing (EERUF) and rapid obstacle sensing using mobile robot sonar (ROSUM), and another is hardware based code method, which includes pseudo-random code, chaotic code and so on.After analyzing these methods synthetically and studying the character of Polaroid 600 electrostatic transducer deeply, a lot of experiments based on the TMS320F2812 DSP hardware platform have been implemented in this paper. From the experiments, it is found that the transmitted sequence by the ultrasonic transducer is almost the same as the triggering sequence sent out from the DSP if the triggering sequence consists of single frequency of pulses. Because of the structure design, application range, limit condition of work principle and material's physics characteristic of transducing elements, the work frequency of transducers can not follow the frequency of the triggering sequence quickly. This means that transducers have the vibrating inertia.To adapt to the intrinsic inertia property of electrostatic ultrasonic transducers, on the basis of analyzing the correlation and randomness of chaotic sequences, the chaotic pulse sequence width modulation (CPSWM) is put forward. Simulation and experiments demonstrate that the CPSWM method can reject the phenomenon of ultrasonic crosstalk very well.