Autonomous cruise control

Abstract

A cruise control system for a vehicle includes a vehicle borne radar for determining range and closing rate of the vehicle relative to a target, such as another moving vehicle, ahead of the vehicle. The range and closing rate are used to determine a new set speed for the cruise control system which may be less than but is not greater than the speed entered in the cruise control by the driver of the vehicle. The new set speed is selected to prevent the vehicle from overtaking the target, and ideally reduces the closing rate to zero at a predetermined minimum distance from the target. In determining the new set speed, the system also determines incremental movements for the vehicle throttle using a selected gain boost and designed to minimize throttle jerk. If the target moves out of the path of the vehicle or speeds up, the system adjusts accordingly and eventually allows the vehicle to resume the originally entered speed when possible.

We claim: 
     
       1. A cruise control system for a vehicle including: a) cruise control means, coupled to a vehicle for controlling the speed of the vehicle at a desired speed selected by a driver of the vehicle;   b) means for determining an error distance;   c) means for validating a target by comparing the distance between the target and the vehicle and determining that the target is within a predicted range based upon a previous detection of the target, and only validating the target upon .[.three.]. .Iadd.a predetermined number of two or more .Iaddend.consecutive determinations that the target is within the predicted range; and   d) means responsive to the square root of the error distance for automatically adjusting the speed at which the cruise control system is set to prevent overtaking the target.   
     
     
       2. The cruise control system of claim 1, wherein the means responsive to the square root of the error distance is capable of both increasing and decreasing the speed of the vehicle. 
     
     
       3. The cruise control system of claim 2, wherein the means responsive to the square root of the error distance cannot adjust the speed at which the cruise control system is set to a speed greater than the desired speed selected by the driver. 
     
     
       4. The cruise control system of claim 1, wherein the means responsive to the square root of the error distance comprises a radar system mounted on the vehicle. 
     
     
       5. The cruise control system of claim 1, wherein the means responsive to the square root of the error distance is also responsive to the closing rate of the vehicle relative to the target. 
     
     
       6. The cruise control system of claim 5, wherein the means responsive to the square root of the error distance determines a new speed at which the cruise control is set, based on the error distance and the closing rate, and determines incremental movements of a throttle for the vehicle, based on the new speed. 
     
     
       7. The cruise control system of claim 5, wherein the means responsive to the square root of the error distance does not adjust the speed at which the cruise control system is set when the closing rate is determined to be zero. 
     
     
       8. A cruise control system for a vehicle including: a) means for setting the cruise control system at a desired speed for the vehicle selected by a driver of the vehicle;   b) means responsive to a target ahead of the vehicle for continuously determining distance of the target from the vehicle and closing rate of the vehicle on the target;   c) means for validating a target by comparing the distance between the target and the vehicle and determining that the target is within a predicted range based upon a previous detection of the target, and only validating the target upon .[.three.]. .Iadd.a predetermined number of two or more .Iaddend.consecutive determinations that the target is within the predicted range; and   d) means responsive to the distance and the closing rate for tracking the target and reducing the speed at which the cruise control system is set when the vehicle is closing on a valid target.   
     
     
       9. The cruise control system of claim 8, wherein the means responsive to a target comprises a radar system mounted on the vehicle. 
     
     
       10. The cruise control system of claim 8, wherein the means responsive to the distance and the closing rate is capable of increasing the speed at which the cruise control system is set up to a maximum equal to the desired speed for the vehicle selected by the driver when it is determined that the target is moving away from the vehicle. 
     
     
       11. The cruise control system of claim 8, wherein the means responsive to the distance and the closing speed comprises means for calculating an ideal closing rate at which the closing speed becomes zero at the minimum distance between the vehicle and the target, means for calculating a closing rate error using the ideal closing rate and the closing rate determined by the means responsive to a target, and means for calculating a new set speed for the cruise control based on the ideal closing rate and the closing rate error and by determining speed of the target. 
     
     
       12. The cruise control system of claim 11, wherein the means responsive to the closing rate and a closing speed further comprises means for calculating speed error based on the new set speed and by determining speed of the vehicle, means for calculating ideal acceleration as a function of the speed error, means for calculating acceleration error based on the ideal acceleration and by determining actual acceleration of the vehicle, and means for controlling the cruise control based on the vehicle speed, the speed error and the acceleration error. 
     
     
       13. The cruise control system of claim 12, wherein the means for controlling the cruise control comprises means for calculating a speed gain factor based on the vehicle speed, means for calculating a gain boost based on the speed error, and means for calculating an incremental throttle movement for the vehicle based on the acceleration error, the speed gain factor and the gain boost. 
     
     
       14. The cruise control system of claim 11, wherein the means for calculating a closing rate error comprises means for subtracting the closing rate determined by the means responsive to a target from the ideal closing rate to determine the closing rate error, and the means for calculating a new set speed comprises means for adding the ideal closing rate, the closing rate error and the speed of the target to determine the new set speed. 
     
     
       15. The cruise control system of claim 12, wherein the means for calculating speed error comprises means for subtracting the vehicle speed from the set speed to determine the speed error, and the means for calculating acceleration error comprises means for subtracting the actual acceleration of the vehicle from the ideal acceleration. 
     
     
       16. A cruise control system for a vehicle including: a) cruise control circuit, coupled to a vehicle for controlling the speed of the vehicle at a desired speed selected by a driver of the vehicle, and responsive to a target ahead of the vehicle for automatically adjusting the speed at which the cruise control system is set to prevent overtaking the target; and   b) means for validating two or more targets by comparing the distance between each target and the vehicle and determining that each target is within a predicted range based upon a previous detection of each target, and only validating a target upon .[.three.]. .Iadd.a predetermined number of two or more .Iaddend.consecutive determinations that the target is within the predicted range.   
     
     
       17. A method of changing a set speed in a cruise control for a vehicle to .[.avios.]. .Iadd.avoid .Iaddend.a target ahead of the vehicle, comprising the steps of: a) determining range of the target from the vehicle;   b) validating a target by comparing the distance between the target and the vehicle and determining that the target is within a predicted range based upon a previous detection of the target, and only validating the target upon .[.three.]. .Iadd.a predetermined number of two or more .Iaddend.consecutive determinations that the target is within the predicted range;   c) determining an actual closing rate of the vehicle on the target; and   d) determining, based on the range and the actual closing rate, a set speed for the cruise control that will maintain a selected minimum distance between the vehicle and the target.   
     
     
       18. The method of claim 17, wherein the step of determining a set speed comprises the steps of: a) determining an ideal closing rate at which the actual closing rate is reduced to zero at the selected minimum distance of the vehicle from the target;   b) subtracting the actual closing rate from the ideal closing rate to determine closing rate error;   c) determining speed of the target; and   d) adding the speed of the target to the ideal closing rate to determine a new set speed for the cruise control.   
     
     
       19. The method of claim 18, comprising the further steps of: a) determining actual speed of the vehicle;   b) subtracting actual speed of the vehicle from the set speed to determine speed error;   c) calculating the ideal acceleration as a selected fraction of the speed error;   d) determining actual acceleration of the vehicle;   e) subtracting actual acceleration of the vehicle from the ideal acceleration to determine acceleration error; and   f) controlling a throttle of the vehicle based on actual speed of the vehicle, the speed error and the acceleration error.   
     
     
       20. The method of claim 19, wherein the step of controlling a throttle comprises the steps of: a) calculating a speed gain factor based on actual speed of the vehicle, to minimize throttle jerk;   b) calculating a gain boost based on the speed error; and   c) calculating an incremental throttle movement based on the acceleration error, the speed gain factor and the gain boost. .Iadd.   
     
     
       21.  The cruise control system of claim 1, wherein the predetermined number of consecutive determinations is equal to three..Iaddend..Iadd.22. The cruise control system of claim 8, wherein the predetermined number of consecutive determinations is equal to three..Iaddend..Iadd.23. The cruise control system of claim 16, wherein the predetermined number of consecutive determinations is equal to three..Iaddend..Iadd.24. The method of claim 17, wherein the predetermined number of consecutive determinations is equal to three..Iaddend.