Sonars with high noise and clutter rejection for use with adaptive robots
Abstract
The goal of this thesis is to develop an ultrasonic ranging system capable of providing range and azimuth information on targets buried in noise and clutter. The information is to be usable by adaptive robots. The two methods selected for research are frequency-modulated, continuous wave (FMCW) ranging, and pseudo-random binary sequence(PRBS) ranging. An experimental FMCW tracking system is designed, tested, and found able to provide useful tracking information under adverse noise conditions. The research is then directed towards PRBS correlation systems, which offer theoretically unlimited noise reduction. However, the basic correlation function is not ideal for control purposes. Two methods are developed which produce modified correlation functions more suitable for control. These methods, phase and time-shift modulation, are also used to move the transmitted spectrum to an area more usable by the transducers. The first experimental PRBS ranging system proves incapable of providing the desired cross-correlation function due to transducer bandwidth limitations and the link between bandwidth and frequency of operation. The second experimental PRBS ranging system uses double like sideband modulation and asynchronous demodulation. It cross-correlates the received signal with two time-shift modulated reference signals, and is capable of producing the desired correlator output and passing high-noise tests. The PRBS system is further modified to include target range and azimuth tracking capabilities. The system proves capable of tracking selected targets under conditions of high noise and clutter.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1984
- Bibcode:
- 1984PhDT........21G
- Keywords:
-
- Robots;
- Sonar;
- Sound Ranging;
- Tracking (Position);
- Ultrasonics;
- Azimuth;
- Clutter;
- Conditions;
- Continuous Radiation;
- Cross Correlation;
- Demodulation;
- Frequency Modulation;
- Noise Reduction;
- Phase Modulation;
- Signal Processing;
- Target Recognition;
- Transducers;
- Communications and Radar