Method and means for avoiding collision between a motor vehicle and obstacles

• US 5,343,206 A
• Filed: 01/06/1993
• Issued: 08/30/1994
• Est. Priority Date: 07/05/1990
• Status: Expired due to Term

• Current Assignee: Fiat Auto S.p.A. (Stellantis NV)
• Original Assignee: Fiat Auto S.p.A. (Stellantis NV)
• Inventors: Re Fiorentin, Stefano, Saroldi, Andrea, Ansaldi, Ermanno
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/001,395
• Time in Patent Office: 601 Days
• Field of Search: 342/70, 342/71, 342/72, 342/176, 342/179
• US Class Current: 342/70
• CPC Class Codes: G01S 13/723 by using numerical data
• CPC Class Codes: G01S 13/89 for mapping or imaging
• 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 2013/9322 using additional data, e.g. driver condition, road state or weather data
• CPC Class Codes: G01S 2013/9329 cooperating with reflectors or transponders

Abstract

The method for avoiding collision between a motor vehicle and obstacles placed in the path of the vehicle comprises the stages of forming a radar map of the area in front of the vehicle, reconstructing the geometry of the road, identifying its edges, detecting the position and speed of the vehicle with respect to the road, determining the presumed path of the vehicle on the basis of the road geometry and the manoeuvre being carried out by the vehicle at that instant, detecting objects on the radar map found lying in the presumed path of the motor vehicle and displaying the map found in a perspective representation, ignoring objects which are off the road and indicating objects in the path of the vehicle in a different manner according to their hazard and if appropriate generating alarms of an acoustic type.

Claims

1. In a method for avoiding collision between a human driven motor vehicle and at least one obstacle comprising the stages of:

searching for at least one obstacle (120) in an environment in front of the motor vehicle (100) along a presumed path (119) for the motor vehicle, calculating the distance (d_obst) and the relative speed (V_obst) of the obstacle, and indicating the obstacle with an indication of its hazard level, these stages being repeated cyclicly, the improvement in that the stage of searching for the obstacle comprises;

generating a map (115) of the environment in front of the motor vehicle (100) by scanning the environment;

reconstructing the geometry of a road (116) on the basis of the map (115);

reconstructing the presumed path (119) of the motor vehicle on the basis of the reconstructed geometry of the road; and

searching for the obstacle (120) within the reconstructed presumed path.

2. A method according to claim 1, characterised in that it also includes the stages of detecting the manoeuvre being performed by the motor vehicle (100) with respect to the road (116), and of amending the presumed path (119) of the motor vehicle on the basis of the manoeuvre detected.

3. A method according to claim 1, characterised in that the said scanning is performed by means of a microwave radar.

4. A method according to claim 1, characterised in that the said stage of generating a map (115) comprises scanning of the environment in front of the motor vehicle (100) within a predetermined scanning angle centred on the longitudinal axis of the vehicle (100), with subdivision of the environment in front of the vehicle into a plurality of sectors, and storing a matrix which includes the findings calculated on the basis of the corresponding sector and the distance found.

5. A method according to claim 1, characterised in that it includes the stages of measuring the angle (θ

) of the steering wheel of the motor vehicle (100), measuring the speed (v) of the vehicle and determining the condition, wet or dry, of the road surface.

6. A method according to claim 5, characterised in that the radius (R_V) and the curvature (C_0V =l/R_V) of the path travelled by the vehicle (100) at that instant is calculated on the basis of the said steering wheel angle (θ

) and the safe distance (dds) of the motor vehicle is calculated on the basis of the formula;

space="preserve" listing-type="equation">dds=v*Tr+v.sup.2 /(2*A.sub.max)

where Tr is a fixed value and A_max represents the maximum deceleration by sharp braking and is stored in the memory as a function of the speed of the vehicle and the road condition.

7. A method according to claim 1, characterised in that the said stage of reconstructing the road geometry includes calculation of the following parameters:

the heading angle (Φ

) of the motor vehicle (100) and its distance from the edges of the road (L_s, L_d), and the curvature (C_0s) and spatial derivative (C_1s) of the road curvature (116).

8. A method according to claim 7, characterised in that values of the said parameters (Φ

, L_s, L_d, C_0s and C_1s) which maximise the value F in the function ##EQU4## where i=1 . . . n, where n is equal to the number of obstacles found in the map, d is the geometrical distance between an obstacle having the coordinates (x_i, y_i) and the edge of the road, identified from the abovementioned five parameters, and α

is a multiplying coefficient of a predetermined value, are sought.

9. A method according to claim 8, characterised in that the value F of the said function is compared with a reference threshold (F₀) and when it is less than the said threshold the curvature (C₁) of the presumed path (119) is determined on the basis of the angle (θ

) of the steering wheel, and if this is not the case the manoeuvre being performed by the motor vehicle (100) is determined.

10. A method according to claim 8, characterised in that the said stage of detecting the manoeuvre being performed includes calculation of the manoeuvre necessary to return the motor vehicle (100) to axial alignment with the road (116) at a predetermined distance (D).

11. A method according to claim 10, characterised in that calculation of the necessary manoeuvre includes calculation of the alignment manoeuvre (C_1a) in accordance with the relationship:

space="preserve" listing-type="equation">C.sub.1a =C.sub.1V =C.sub.1s +2*(C.sub.0s -C.sub.0V)/D-2*Φ

/D.sup.2

where C_1V represents the derivative of the spatial curvature of the path (119) of the motor vehicle (100), C_1s is the derivative of the spatial curvature of the road, C_0s is the spatial curvature of the road, C_0V is the spatial curvature of the vehicle'"'"'s path, Φ

is the heading angle and D represents the said predetermined distance.

12. A method according to claim 11, characterised in that the calculated value of the aligning manoeuvre (C_1a) is compared with a limit value (C_1amax) to determine whether the motor vehicle (100) is performing a manoeuvre aligning it with the road profile (119) or is performing a special manoeuvre.

13. A method according to claim 12, characterised in that when the value of the aligning manoeuvre (C_1a) lies below the said limit value (C_1amax) the spatial derivative (C₁) of the curvature of the presumed path (119) is determined on the basis of the said value of the aligning manoeuvre (C_1a), otherwise the spatial derivative (C₁) of the curvature of the presumed path (119) is calculated on the basis of the special manoeuvre being performed on the basis of the equation:

##EQU5## where C_0V (t) and C_0V (t-1) are the curvature of the vehicle'"'"'s path (100) at the instants when the present map (115) and the previous map respectively was determined, v is the speed of the motor vehicle (100) and t is the time between two successive detection cycles.

14. A method according to claim 1, characterised in that the said stage of searching for possible objects within the presumed path includes searching for obstacles (120) within a travel corridor (119) having a width equal to the width of the motor vehicle, a curvature equal to C_0s and a derivative of the curvature equal to C₁.

15. A method according to claim 14, characterised in that when the said stage of searching for obstacles (120) has a negative outcome a representation of the map (115) of the road situation is displayed.

16. A method according to claim 14, characterised in that when the said stage of searching for obstacles (120) has a positive outcome the identification of an obstacle (120) in the previous map (115) is verified.

17. A method according to claim 16, characterised in that when no obstacle is identified in the previous map (115) a representation of the map (115) of the road situation is displayed, and if this is not the case the relative speed (V_obst) of the obstacle found is calculated, the distance (d_obst) of the obstacle is compared with the safe distance (dds), when the relative speed (V_obst) of the obstacle is negative and the distance to the obstacle (dds) is less than the safe distance a serious alarm condition is generated, when the relative speed of the obstacle is positive and the distance to the obstacle is less than the safe distance an alarm condition is generated, and when the relative speed is negative and the distance to the obstacle is greater than the safe distance a prealarm condition is generated.

18. A method according to claim 1, characterised by the generation of a perspective representation of the map (115) of the environment in front of the motor vehicle showing the edges (124) of the road (116), the presumed path (119) of the motor vehicle (100) and objects (125, 126) located on the road, with a different identification according to hazard level.

19. In a system for avoiding collision between a human driven motor vehicle and at least one object, the system including a sensor (22) for monitoring an environment in front of the motor vehicle (100) to detect the presence of the object, means (47, 49) for calculating the distance (d_obst) and the relative speed (V_obst) of the object, and means (32, 34) for indicating the presence of the object with an indication of its hazard level, the improvement in that the sensor (22) is a scanning sensor for generating a map (115) of the environment in front of the motor vehicle (100) comprising means (39) for reconstructing the geometry of a road (116) on the basis of the map, means (15) for reconstructing a presumed path (119) for the motor vehicle on the basis of the reconstructed geometry of the road, and means (46) for searching for the object within the presumed path.

20. A system according to claim 19, characterised in that the said sensor (22) is a microwave radar.

21. A system according to claim 19, characterised in that it includes means (43) for detecting the manoeuvre being performed by the motor vehicle (100) with respect to the road (116) and means (45) for altering the presumed path (119) of the motor vehicle (100) on the basis of the manoeuvre found.

22. A system according to claim 19, characterised in that it includes means (17) for counting the positive findings obtained for a given distance within a plurality of sectors of predetermined angular size constituting the map (115) and means (18) for storing a matrix recording the number of findings calculated in relation to the corresponding sector and the distance found.