Precision Real-time Ultrasonic Ranging Study

Probed into the problem of how to realize real-time ultrasonic distance measurement with high precision under the bad environment, this paper describes the component of ultrasonic ranging system and the time delay estimate algorithm.Firstly, the working mechanization of ultrasonic transducer is studied. A driving circuit for medium and low power transducers is presented by accurate derivation. According to the ultrasonic attenuation characteristic, automatic gain control circuit is designed. This circuit can extend the dynamic range of echo signal and improve ranging precision. Based on a system-on-a-chip microprocessor, the hardware platform of ultrasonic ranging system is set up. Experiments show that this system can reject noise signals strongly and improve the range coverage of transducers to a certain extent.Secondly, conventional ranging algorithm on adaptive time delay estimate is studied. The relative merits of the algorithm are discussed in detail. After finding the conformity characteristic of echo envelope, the paper presents a LMSTDE algorithm based on echo envelope. Computer simulation of this algorithm is done and performance analysis is made. The results of actual experiments accord with the theoretic analysis.Finally, the relation between convergence procedure of an adaptive filter and its weight coefficient is discussed. Then a new fast algorithm about adaptive time delay estimate is proposed. It is proved to be effective by experiments on the ultrasonic ranging system.