SENSOR FOR PARKING AREA

• US 20100265118A1
• Filed: 04/01/2010
• Published: 10/21/2010
• Est. Priority Date: 04/01/2009
• Status: Active Grant

• Current Assignee: Elsag Datamat SPA (Leonardo S.p.A.)
• Original Assignee: Elsag Datamat SPA (Leonardo S.p.A.)
• Inventors: Desiderio, Alfonso, MERLI, Silvio
• Granted Patent: US 8,164,508 B2
• Time in Patent Office: Days
• US Class Current: 342/27
• CPC Class Codes: G01S 13/343 using sawtooth modulation
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 2013/9314 Parking operations
• CPC Class Codes: G01S 7/2927 by deriving and controlling a threshold value
• CPC Class Codes: G01S 7/4021 of receivers

Abstract

A proximity sensor for a parking area designed to detect the presence of an obstacle constituted by a parked vehicle, comprises a transmitting radar, designed to send electromagnetic pulses towards the obstacle, a receiving radar, designed to receive the pulses reflected by the obstacle, and a processing circuit, designed to compare samples detected in a certain condition of absence of an obstacle in a calibration step with those detected in a condition of detection of an obstacle to determine the presence/absence of the obstacle.

Claims

1. A proximity sensor (1) for a parking area designed to detect the presence of an obstacle constituted by a vehicle parked in the parking area, comprising:

a radar (5) provided with a transmitting section (3) designed to send electromagnetic pulses (Ir) towards the obstacle (4), and a receiving section (5) designed to receive the pulses reflected by the obstacle (4); and

processing means (22) for processing the signal generated by the receiving section (5),

calibration means (110, 120), designed to acquire and store a series of samples (A1, A2, A3, . . . , An) of pulses detected by the receiving section (5) in response to the electromagnetic pulses generated by the transmitting radar (3) in a condition of certain absence of obstacle (4);

measuring means (130), designed to acquire and store a series of samples (Ar1, Ar2, Ar3, . . . , Arn) of pulses detected by the receiving section (5) in response to the electromagnetic pulses generated by the transmitting section (3) in a condition of detection of an obstacle (4); and

comparison means (230), designed to compare the samples detected in the condition of certain absence of obstacles (4) with the ones detected in the condition of detection of an obstacle (4) for determining the presence/absence of the obstacle (4).

2. The sensor according to claim 1, wherein the calibration means (110, 120) are configured to perform the following operations:

sampling the signal that is generated by the receiving section (5) and represents the pulses received;

identifying on the sampled signal the amplitudes (A1, A2, A3, . . . , An corresponding to the various pulses received in the absence of an obstacle; and

adding together the values detected of the amplitudes (A1, A2, A3, . . . , An) to define a first threshold value (thr1), i.e., (thr1)=(A1+A2+A3+ . . . +An);

the measuring means (130) being configured to perform the following operations;

generating a pre-set number n of electromagnetic pulses that are received by the receiving section (5);

sampling the signal that is generated by the receiving section (5) and represents the pulses received;

identifying on the sampled signal the amplitudes (Ar1, Ar2, Ar3, . . . , Arn) corresponding to the various pulses received;

computing the absolute value of the difference between the respective amplitudes (A1, A2, A3, . . . , An) detected by the calibration means and the amplitudes detected by the measuring means (Ar1, Ar2, Ar3, . . . , Arn), i.e., Δ

1=(|A1−

Ar1|), Δ

2=(|A1−

Ar1|), Δ

3=(|A1−

Ar1|), . . . , Δ

n=(|An−

Arn|);

adding together the differences (Δ

1, Δ

2, Δ

3), . . . , Δ

n to calculate a sum of differences (sum-diff)=(Δ

1+Δ

2+Δ

3+ . . . +Δ

n);

the comparison means (230) being configured to compare the sum of differences sum-diff with a reference value calculated as a function of the first threshold value thr1.

3. The sensor according to claim 2, wherein the comparison means (230) detect the presence (240) of an obstacle (4) in the case where the sum of differences sum-diff exceeds by a certain percentage % the first threshold value thr1.

4. The sensor according to claim 1, wherein means are present designed to implement a stringent algorithm (260) configured for:

calculating (250) the mean value mean of the N amplitudes (A1, A2, A3, . . . , AN) corresponding to the various pulses received in the absence of an obstacle, i.e., mean=(A1+A2+A3 . . . +AN)/N;

calculating (260) the differences, in absolute value, between the amplitudes (A1, A2, A3, . . . , Δ

N) corresponding to the various pulses received in the absence of an obstacle and the mean value, i.e., |A1−

mean|, |A2−

mean|, |A3−

mean| . . . |AN−

mean|;

calculating (260) an adaptive threshold (thr_a1, thr_a2, thr_a3, . . . , thr_aN) for each sample on the basis of the respective difference;

calculating (270) the differences (Δ

1, Δ

2, Δ

3+ . . . +Δ

N) between the amplitudes (A1, A2, A3, . . . , AN) corresponding to the various pulses received in the absence of an obstacle and the respective amplitudes (Ar1, Ar2, Ar3, . . . , Arn) corresponding to the various pulses received during detection of an obstacle; and

comparing each difference calculated and the respective adaptive threshold, i.e., Δ

1 compared with (thr_a1), Δ

2 compared with (thr_a2), Δ

3 compared with (thr_a3), . . . Δ

N compared with (thr_aN); and

detecting an obstacle (240) in the case where a pre-set percentage of the differences Δ

1, Δ

2, Δ

3+ . . . +Δ

N exceeds its own adaptive threshold (thr_a1, thr_a2, thr_a3, . . . , thr_aN).

5. The sensor according to claim 4, wherein the adaptive threshold (thr_a1, thr_a2, thr_a3, . . . , thr_aN) is calculated as percentage of each respective difference;

i.e., it is obtained by multiplying each absolute value of the difference by a weight.

6. The sensor according to claim 1, wherein the transmitting section (3) of the radar (2) is configured for issuing electromagnetic pulses, the frequency of which varies as a function of a sawtooth driving signal (P) supplied on its input;

the proximity sensor (1) comprising an analog-to-digital converter (20), which is designed to sample the signal generated at output from the receiving section (5) on an edge, in particular the falling edge, of the driving sawtooth signal.

7. The sensor according to claim 6, wherein a single clock generator (16) concurs in creating the driving signal (P) and in synchronising the A/D converter (20).

8. The sensor according to claim 6, wherein:

a sawtooth-signal generator (8) is provided, comprising a programmable current generator (10) which charges a capacitor (12);

the voltage Vc across the capacitor (12) produces the driving signal (P); and

the signal generator (8) further comprises a switch device (14) set across the capacitor (12) and designed to shortcircuit periodically the capacitor itself (12) to form the falling edge of the sawtooth, the rising edge of which is formed during linear charging of the capacitor (12).

9. The sensor according to claim 8, wherein the programmable current generator (10) is configured for receiving at input a sequence of bits and generating at output a current proportional to the numerical value expressed by the sequence of bits.

10. The sensor according to claim 9, wherein the programmable current generator (10) produces a transfer function of the type:

(Iout)=(Imax)·

((BIT2/2)+(BIT1/4)+(PWM_OUT/64))

where;

(Iout) is the output current of the generator (10);

(Imax) is a current calculated on the basis of the supply voltage (VDD) of the current generator and of circuit parameters (Vemitter/R) of the current generator itself;

BIT2 is the most significant bit in the sequence of bits;

BIT1 is the bit having an immediately lower value of importance with respect to the most significant bit in the sequence; and

PWM_OUT is a square-wave signal with a variable duty cycle that is a function of the least significant bit in the sequence of bits.