Evaluation concept for distance measuring processes

• US 6,259,515 B1
• Filed: 02/05/1999
• Issued: 07/10/2001
• Est. Priority Date: 02/07/1998
• Status: Expired due to Term

• Current Assignee: Valeo Schalter und Sensoren GmbH (Valeo SE)
• Original Assignee: ITT Manufacturing Enterprises, Inc. (ITT, Inc.)
• Inventors: Philipps, Werner, Benz, Jurgen, Grabmaier, Anton
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/245,514
• Time in Patent Office: 886 Days
• Field of Search: 356/5-1-, 342/134, 342/135
• US Class Current: 356/5.08
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 7/4866 by fitting a model or function to the received signal
• CPC Class Codes: G01S 7/4868 Controlling received signal intensity or exposure of sensor

Abstract

A process for determining the distance (D) between a distance sensor and an object. A transmitter sends wave pulses with a predetermined first frequency fb 1 and the wave pulses reflected by the object are received by a receiver and are directed in the form of an analog electrical incoming signal to an A-D converter. The latter scans the incoming signal with a second frequency f2 with f2>f1 and converts it into a digital signal Z(t) which is evaluated for determining a distance value (D) in the following manner:

a) Evaluation of the digital signal Z(t) for determining a first wave pulse propagation time (T1);

b) k-fold repetition of the step a) for determining the total k wave pulse propagation times (T1, T2, . . . , Tk);

c) Calculation of a mean wave pulse propagation time (T=(T1+T2+ . . . +Tk)/k); and

d) Calculation of the distance value (D) in accordance with D−v=T/2.

Claims

1. A process for determining the distance between a distance sensor and an object, wherein an electrical pulse signal with a predetermined first frequency (f1) is directed to one transmitter of the distance sensor, the transmitter transmits upon the occurrence of each electrical pulse a wave pulse, the wave pulses are reflected off the object, a receiver of the distance sensor receives the reflected wave pulses and puts out an analog electrical incoming signal, characterized by the steps of:

continuously scanning the analog electrical incoming signal by an A\D converter at a second frequency (f2) with f2>

f1, converting the scanned electrical incoming signal into a digital signal Z(t), and evaluating the digital signal Z(t), for the purpose of determining a distance value (D), by;

a) evaluating the digital signal Z(t), received with respect to one or several emitted wave pulses, for determining a first wave pulse propagation time (T1);

b) k-fold repeating step a) for determining total k wave pulse propagation times (T1, T2, . . . , Tk), wherein k is an integral number with k>

1;

c) calculating a mean wave pulse propagations time T (T1+T2+ . . . +Tk)/k;

d) calculating the distance value (D) in accordance with D=v*T/2, wherein v is the propagation speed of the wave pulses;

continuously entering the obtained distance values (D) in a memory; and

differentiating several distance values (D) with respect to time to continuously determine the relative speed between the object and the distance sensor.

2. The process in accordance with claim 1 characterized in that in step a) the digital signal Z(t) is evaluated with respect to a plurality of n wave pulses, wherein n is an integral number with n>

1, and further comprising the steps of;

a1) breaking down the digital signal Z(t) into signal sequences Z1(t), . . . , Zn(t) which are in n temporal order;

a2) forming a mean value via the n signal sequences, and calculating a mean digital signal <

Z(t)>

; and

a3) using the mean digital signal <

Z(t)>

for determining the first wave pulse propagations time (T1).

3. The process in accordance with claim 2 characterized in that n is between 10 and 100.

4. The process in accordance with claim 2 characterized in that the evaluation of the digital signal Z(t) in step a) and of the mean digital signal <

Z(t)>

in step 2a2) comprises steps;

calculating a correlation function F(τ

) of the type according to one of the equations;

$F<br><br>\left(\mathrm{\tau <br><br>}\right)=\underset{\mathrm{\tau <br><br>}-\mathrm{\infty <br><br>}}{\lim }<br><br>\frac{1}{2<br><br>T}<br><br>{\int <br><br>}_{-T}^{+T}\mid <br><br>Z<br><br>\left(t\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>R<br><br>\left(t-\mathrm{\tau <br><br>}\right)<br><br>\text{\hspace{1em}<br><br>}<br><br><br><br>t$$F<br><br>\left(\mathrm{\tau <br><br>}\right)=\underset{\mathrm{\tau <br><br>}-\mathrm{\infty <br><br>}}{\lim }<br><br>\frac{1}{2<br><br>T}<br><br>{\int <br><br>}_{-T}^{+T}\mid <br><br>\left(Z<br><br>\left(t\right)\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>R<br><br>\left(t-\mathrm{\tau <br><br>}\right)<br><br>\text{\hspace{1em}<br><br>}<br><br><br><br>t$

wherein R(t) is a predetermined, discretized reference signal with a temporal resolution which is higher by an order of m than Z(t) or <

Z(t)> and

wherein m is an integral number with m>

1 and the determination of the wave pulse propagation time T1 is the time at which the correlation function F(τ

) is maximum.

5. The process in accordance with claim 4 characterized in that the discretized reference signal R(t) is a Gauss function.

6. The process in accordance with claim 4 characterized in that m is between 2 and 10.

7. The process in accordance with claim 1 characterized in that the wave pulses are light pulses and the pulse propagation time is between 20 and 50 ns.

8. The process in accordance with claim 1 characterized in that f1 is between 1 kHz and 10 kHz.

9. The process in accordance with claim 1 characterized in that f2 is approximately 40 MHz.

10. The process in accordance with claim 2 characterized in that, from the mean digital signal <

Z(t)>

, the reflected total intensity and/or the maximum intensity and/or the signal-to-noise ratio is determined, at least one of which controls the amplification of an amplifier for amplifying the incoming signal.

11. A process for determining the distance between a distance sensor and an object, wherein an electrical pulse signal with a predetermined first frequency (f1) is directed to one transmitter of the distance sensor, the transmitter transmits upon the occurrence of each electrical pulse a wave pulse, the wave pulses are reflected off the object, and a receiver of the distance sensor receives the reflected wave pulses and puts out an analog electrical incoming signal, characterized by the steps of:

continuously scanning the analog electrical incoming signal by an A/D converter at a second frequency (f2) with f2>

f1, converting the scanned electrical incoming signal into a digital signal Z(t), and evaluating the digital signal Z(t), for the purpose of determining a distance value (D), by;

a) evaluating the digital signal Z(t), received with respect to a plurality of n wave pulses, wherein n is an integral number (n>

1), the evaluating step further including the steps of;

a1) breaking down the digital signal Z(t) (13) into signal sequences Z1(t), . . . , Zn(t) which are in n temporal order;

a2) forming a mean value via the n signal sequences, and calculating a mean digital signal <

Z(t)>

; and

a3) using the mean digital signal <

Z(t)>

for determining a first wave pulse propagation time (T1);

b) k-fold repeating step a) for determining total k wave pulse propagation times (T1, T2, . . . , Tk), wherein k is an integral number with k>

1;

c) calculating a mean wave pulse propagations time T (T1+T2+ . . . +Tk)/k;

d) calculating the distance value (D) in accordance with D=v*T/2, wherein v is the propagation speed of the wave pulses.