Distance sensor and method for determining a distance

• US 8,670,289 B2
• Filed: 06/24/2008
• Issued: 03/11/2014
• Est. Priority Date: 08/21/2007
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Niemz, Volker
• Primary Examiner(s): PIHULIC, DANIEL T
• Application Number:
  US12/673,383
• Publication Number:
  US 20110259106A1
• Time in Patent Office: 2,086 Days
• Field of Search: 367/98
• US Class Current: 367/98
• CPC Class Codes: G01S 15/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurement G01S15/32
• CPC Class Codes: G01S 15/931 of land vehicles
• CPC Class Codes: G01S 2015/935 for measuring the contour, e.g. a trajectory of measurement points, representing the boundary of the parking space
• CPC Class Codes: G01S 2015/938 in the bumper area
• CPC Class Codes: G01S 7/527 Extracting wanted echo signals Doppler systems G01S15/50

Abstract

A distance sensor has an ultrasound transceiver for transmitting ultrasound pulses and for receiving reflected ultrasound pulses from an object. A discriminator unit is configured for determining a center of distribution of the received reflected ultrasound pulse on the basis of the received reflected ultrasound pulse exceeding a first threshold value and subsequently dropping below a second threshold value. A propagation time analyzer device, is designed for determining, based on the determined center of distribution, the distance to the object.

Claims

1. A distance sensor, comprising:

an ultrasound transceiver for transmitting ultrasound pulses and for receiving reflected ultrasound pulses from an object;

a discriminator unit for determining a center of distribution of the received reflected ultrasound pulses based on the received reflected ultrasound pulse exceeding a first threshold value and subsequently dropping below a second threshold value; and

a propagation time analyzer device for determining, based on the determined center of distribution, the distance to the object;

an estimator device for estimating a height of the object based on at least one of a pulse width of the reflected ultrasound pulses, a ratio of a number of reflected ultrasound pulses to a number of transmitted ultrasound pulses, and a distribution of the centers of distribution of reflected ultrasound pulses of an object; and

a correction unit for correcting the distance determined from the propagation time analyzer device as a function of the estimated height.

2. The distance sensor of claim 1, further comprising:

a noise analyzer device for determining a signal noise of the ultrasound transceiver; and

a threshold value determining device for establishing the first threshold value and the second threshold value as multiples of the determined signal noise.

3. A method for determining a distance to an object, the method comprising:

establishing an end of a propagation time measurement by a center of distribution of a reflected ultrasound pulse; and

determining the distance to the object based on the propagation time measurement of the reflected ultrasound pulse;

estimating a height of the object based on at least one of a pulse width of the reflected ultrasound pulses, a ratio of a number of reflected ultrasound pulses to a number of transmitted ultrasound pulses, and a distribution of the centers of distribution of reflected ultrasound pulses of an object; and

correcting the distance determined from the propagation time analyzer device as a function of the estimated height.

4. The method of claim 3, wherein the center of distribution is determined as a point in time which is located between a first point in time when the ultrasound pulse exceeds a first threshold value and a subsequent second point in time when it drops below a second threshold value.

5. The method of claim 4, wherein the center of distribution is determined as a weighted average of the first point in time and the second point in time.

6. The method of claim 3, wherein a height of the object is estimated based on a plurality of reflected ultrasound pulses, and wherein the distance determined by the propagation time measurement is corrected as a function of the estimated height of the object.

8. The method of claim 3, wherein a signal noise is determined and the first threshold value and second threshold value are established as multiples of the signal noise.

9. The method of claim 3, wherein the first threshold value and the second threshold value are established as a function of the ambient temperature.

7. A method for determining a distance to an object, the method comprising:

establishing an end of a propagation time measurement by a center of distribution of a reflected ultrasound pulse; and

determining the distance to the object based on the propagation time measurement of the reflected ultrasound pulse;

wherein a height of the object is estimated based on a plurality of reflected ultrasound pulses, and wherein the distance determined by the propagation time measurement is corrected as a function of the estimated height of the object; and

wherein the height of the object is determined from the plurality of reflected ultrasound pulses based on at least one of a pulse width of the reflected ultrasound pulses, the ratio of the number of reflected ultrasound pulses to the number of transmitted ultrasound pulses, and a distribution of the distances determined by propagation time measurement.