| Ultrasonic crosstalk is one of the main causes of false distance measurements that reduce the work efficiency of sonar sensors in mobile robots. To enhance the real-time performance of sonar systems, chaotic pulse position-width modulation (CPPWM) sequences are proposed to construct short digital transmission sequences to trigger ultrasonic transducers. Thanks to their properties of sharp autocorrelation and flat cross-correlation, chaotic series are used to modulate both pulse position and width. To obtain the better echo correlation properties and the larger echo energy, the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is adopted to optimize the pulse periods and pulse duty ratio. Real experiments using Polaroid 600 series instrument-grade electrostatic transducers validate the suitability of the proposed method. |