Modeling And Simulation Of Non-crosstalk Ultrasonic Ranging Systems

Ultrasonic sensors have been widely used in the feild of mobile robotics for distance measurement with resonable cost and modest system's complexity. In order to provide mobile robots with more environmental information, normally a sensor ring with multiple ultrasonic transducers is required. Crosstalk phenomenon, which can result in erroneous distance measurement, often occurs among adjacent transducers on the sensor ring. Two different kind of methods have been used by researchers to eliminate ultrasonic crosstalk, which are called heuristics based soft-processing method and hardware based code method, respectively.The following work has been done in this thesis.1. The state of arts of eliminating of ultrasonic crosstalk is summarized. The cut-in point is found to solve the ultrasonic crosstalk problem.2. The ultrasonic transducer is excited by the circuit based on DC-DC module. The system oscillating time is effectively reduced, compared with the transformer based drive mode.3. The Mathematics model of the ultrasonic range system is built. The circuit characteristic is studied based on this model and different triggering methods are compared.4. Pulse width modulation, frequency modulation as wel as phase modulation are simulated by the system model. These modulating methods are analyzed and their correlation results are compared.5. By analyzing the correlation results of sequences with different length, the relationship between length and correlation value of sequences is presented. To overcome the unpredictability of short sequence correlations, the concept of correlation gridmap of short sequence is put forward.