Moving obstacle detection system for a vehicle

• US 4,549,181 A
• Filed: 09/29/1982
• Issued: 10/22/1985
• Est. Priority Date: 10/31/1981
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Tachibana, Akira, Kiyoto, Masami
• Primary Examiner(s): Groody, James J.
• Application Number:
  US06/428,225
• Time in Patent Office: 1,119 Days
• Field of Search: 340/901-904, 340/53, 367/909, 367/112, 343/7 VM, 180/169
• US Class Current: 340/904
• CPC Class Codes: G01S 13/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• CPC Class Codes: G01S 13/62 Sense-of-movement determination G01S13/589 takes precedence
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 2013/932 using own vehicle data, e.g. ground speed, steering wheel direction
• CPC Class Codes: G01S 2013/9324 Alternative operation using ultrasonic waves
• CPC Class Codes: Y10S 367/909 Collision avoidance

Abstract

A moving obstacle detection system using a Doppler radar device for an automotive vehicle which detects and informs a vehicle driver that another vehicle (moving obstacle) approaches or moves away from the detecting vehicle, wherein there is provided a means for determining whether the rate of change of the period of a Doppler signal outputted from the Doppler radar equipment with respect to time exceeds a predetermined value so that an erroneous alarm in response to a pedestrian or another vehicle traversing the front detection area of the vehicle, e.g., when vehicle is at rest at in an intersection is inhibited. Consequently, more reliable detection of approach or departure of another vehicle can be achieved.

Claims

1. A moving obstacle detection system for a vehicle, comprising:

(a) a Doppler radar transceiver for transmitting an electromagnetic radiation signal of known frequency, receiving the reflected radiation from moving objects within a specified detection area exposed to the transmitted radiation, and outputting a Doppler beat signal comprising a linear function of the transmitted and received radiation signals;

(b) means responsive to said Doppler signal for indicating that an obstacle is moving towards or away from the vehicle when the rate of change of frequency of said Doppler signal exceeds a first predetermined value; and

(c) inhibiting means responsive to said Doppler signal for preventing operation of said indicating means when the rate of change of frequency of said Doppler signal exceeds a second predetermined value exceeding the first predetermined value.

2. The system of claim 1, further comprising an amplitude judging circuit for preventing operation of said indicating means when the average positive peak amplitude of said Doppler signal does not exceed a predetermined amplitude level.

3. The system of claim 1, further comprising a vehicle halt detector for preventing operation of said indicating means when the vehicle is detected to be at rest.

4. The system of any one of claims 1, 2, or 3, wherein said indicating means comprises a period-to-voltage converter which converts said Doppler signal into a converted signal (a) comprising a train of pulses, the width and amplitude of each of which corresponds to one frequency cycle of said Doppler signal, a voltage comparator for comparing the converted signal to the first predetermined value and outputting an alarm signal when the converted signal level exceeds the first predetermined value, and an alarm circuit for broadcasting an alarm to the occupant of the vehicle in response to the alarm signal.

5. The system of claim 4, wherein said inhibiting means comprises means for converting the converted signal into a differentiated signal comprising a train of pulses, the amplitude of each of which is indicative of the difference in amplitude between two sequential pulses of the converted signal, and checking means for comparing the differentiated signal to the second predetermined value and outputting a high-level signal when the differentiated signal does not exceed the second predetermined value, and wherein said indicating means further comprises gating means for preventing the conduction of the alarm signal to the alarm circuit in the absence of the high-level signal from said comparing means.

6. The system of claim 5, wherein said gating means comprises an AND gate, the output terminal of which is connected to the alarm circuit, and the input terminals of which are connected to the output terminals of at least said checking means and the voltage comparator of said indicating means.

7. The system of claim 5, wherein said checking means comprises a second voltage comparator.

8. The system of claim 5, wherein said checking means comprises a second voltage comparator outputting a high-level signal when the differentiated signal exceeds the first predetermined value, a third voltage comparator for outputting a high-level signal when the differentiated signal exceeds the second predetermined value, an AND gate, one input terminal of which is connected to the second voltage comparator and an inverting input terminal of which is connected to the third voltage comparator, and an R-S flip-flop, the set terminal of which is connected to the output terminal of said AND gate, the reset terminal of which is connected to the third voltage comparator, and the Q-output terminal of which is connected to said gating means.

9. The system of claim 5, wherein said converting means comprises a voltage differentiator.

10. The system of claim 5, wherein said converting means comprises a hold circuit for delaying the converted signal for a period of time substantially equal to the current period of the converted signal and a subtracting circuit for subtracting the converted signal from the delayed converted signal from the hold circuit and outputting a voltage corresponding to the absolute value of the difference between the converted signal and the delayed converted signal.

11. A moving obstacle detection system for an automotive vehicle, comprising:

(a) a Doppler radar module which directionally transmits a high-frequency wave in front of the vehicle, receives the reflected wave of the transmitted wave when an obstacle is present in the forward position of the vehicle, and outputs a Doppler signal having a beat frequency corresponding to the frequency difference between the transmitted and reflected waves and having an amplitude which changes according to the distance between the vehicle and obstacle;

(b) a first means responsive to the Doppler signal from said Doppler radar module for determining whether the average amplitude of the Doppler signal exceeds a first predetermined value representing a predetermined distance between the moving obstacle and the vehicle, said first means outputting a first signal when the amplitude exceeds the first predetermined value;

(c) a second means responsive to the Doppler signal from said Doppler radar module for converting the period of the Doppler signal into a corresponding voltage;

(d) a third means for comparing the output voltage from said second means to a predetermined level and outputting a second signal when the output voltage of said second means exceeds the predetermined level;

(e) a fourth means for detecting whether vehicle is at rest and outputting a third signal when the vehicle is stopped;

(f) a fifth means responsive to the output voltage of said second means for determining whether the rate of change of the period of the Doppler signal with respect to time exceeds a predetermined value and outputting a fourth signal when the rate of change of the period of the Doppler signal does not exceed the predetermined value; and

(g) an alarm circuit which produces an alarm for a vehicle driver when the duration of coincidence of the first, second, third, and fourth signals inputted thereinto exceeds a predetermined interval of time.

12. A moving obstacle detection system as set forth in claim 11, wherein said fifth means comprises:

(a) a differentiator which differentiates the output voltage from said second means for detecting the change in the period of the Doppler signal;

(b) a comparing circuit which compares the differentiated signal from said differentiator with a first predetermined threshold value, outputs a fifth signal when the differentatied signal level exceeds the first predetermined threshold value, simultaneously compares the differentiated signal with a second predetermined threshold value, and outputs a sixth signal when the differentiated signal exceeds the second predetermined threshold value, said second predetermined threshold value exceeding said first predetermined threshold value; and

(c) a flip-flop circuit having a first terminal which receives the fifth signal from said comparing circuit and a second terminal which receives the sixth signal from said comparing circuit, and which is set to continue output of the fourth signal to said alarm circuit when the sixth signal is not received at the second terminal thereof.

13. A moving obstacle detection system as set forth in claim 12, wherein said comparing circuit is so constructed that one comparator compares the differentiated signal from said differentiator with the first predetermined threshold value, the other comparator compares the differentiated signal with the second predetermined threshold value, and the output of the fifth signal from said one comparator is inhibited when the sixth signal is outputted from said other comparator.

14. A moving obstacle detection system as set forth in claim 12, wherein said flip-flop circuit is a set-reset flip-flop circuit of the reset-priority type.

15. A moving obstacle detection system as set forth in claim 11, wherein said fifth means comprises:

(a) a hold circuit responsive to the output voltage from said second means for holding the output voltage from said second means until the next change in the period of the Doppler signal;

(b) a subtractor which receives the hold output voltage from said hold circuit and output voltage of said second means and outputs a signal, the level of which corresponds to the absolute value of the difference in period between successive cycles of the Doppler signal; and

(c) a voltage comparator which compares the signal output from said subtractor to a predetermined level and outputs a signal which disables said alarm circuit, said signal from said comparator being the inversed level of said fourth signal, when the signal from said subtractor exceeds the predetermined level.