An accurate compact ultrasonic 3D sensor using broadband impulses requiring no initial calibration

Abstract

A compact 3D ultrasonic sensor for scene analysis is presented in this paper. A centered transmitter emits a broadband ultrasonic impulse which is reflected by obstacles in the environment. Reflected waves, if propagated back to the sensor, are then received by four identical ultrasonic microphones. These signals are used to provide polar-and azimuth information based on time difference of arrival and in addition, by using a novel method presented in this paper, sub wavelength accurate distance measurements are possible as well. The used algorithm does not rely on the actual shape of the signal but only on its statistical properties. This is a great achievement because commercially available broadband ultrasonic transducers are typically piston membrane types which exhibit a strong frequency dependent radiation pattern. If measurements are performed outside of the main lobe, not only the signal amplitude is greatly reduced requiring algorithms capable of dealing with a low SNR but also the phase of the signal is affected yielding simple pulse compression techniques useless. The article includes a description of the problem, a comparison to existing systems, a theoretical treatment of the system configuration and experimental results demonstrating the performance of our sensor.

Intelligent Wavelet Based Pre-Filtering Method for Ultrasonic Sensor Fusion Inverse Algorithm Performance Optimization

“…Previously, some articles have already calculated the positions of the measured objects from multiple sensor measurements, but instead of calculating the absolute position of the objects, the angles were determined. This also gives the required information, even though the sensors can not distinguish from which object the signal is emitted if multiple objects are measured [18][19][20]. Therefore, another correlation needs to be used.…”

A Self-Contained and Self-Checking LPS with High Accuracy

“…One problem faced during system design was the coverage area as the broadband transducers have a frequency dependent radiation pattern. Signals resulting from directions outside the mainlobe are heavily changed in phase/amplitude and correlation can drop by more than 50% [25]. For this reason a small cone has been attached to the sensors similar to [26].…”

“…This variance is closely related to the DOP as it just defines the spread of the points at each position. (23) (24) Finally the single value for the combined standard uncertainty is (25) Results are reported as (26) Reporting results as in Equation (14) is necessary as the positions are 3-dimensional quantities but the distance is only a scalar. A possible extension for the formalism applied here would be to define all equations in all three dimensions.…”