Adaptive cruise control system with speed based mode

A controller for an adaptive cruise control system having a speed based mode includes an input for receiving a signal indicative of a detected target object, an input for receiving the speed of the host vehicle and control logic. The control logic is capable of transmitting messages to maintain the vehicle at a preset time gap from the target object upon receiving the signal indicative of a target object and transmitting messages to set the vehicle at a predetermined following distance from the target object in response to the speed of the host vehicle being less than or equal to a minimum speed.

BACKGROUND

The present invention relates to embodiments of an adaptive cruise control system with speed based modes. Typical adaptive cruise control systems maintain the host vehicle in a time to target mode. If the target vehicle is moving slowly for long periods of time, such as through heavy traffic, the adaptive cruise control system allows the host vehicle to get closer and closer to the target vehicle as long as the time to the target vehicle is kept the same. Finally, if the target vehicle stops, the host vehicle in a time to target mode will brake aggressively. Additionally, the vehicle may release the brakes as soon as the target vehicle is no longer detected, causing the vehicle to jerk. Some drivers will disable the adaptive cruise control in slow traffic situations for this and other reasons. However, there is a desire for an adaptive cruise control system that is able to operate effectively regardless of the speed of the target vehicle.

SUMMARY

Various embodiments of a controller for a host vehicle having adaptive cruise control comprise an input for receiving a signal indicative of a detected target object; an input for receiving the speed of the host vehicle; and control logic. The control logic is capable of transmitting messages to maintain the vehicle at a preset time gap from the target object upon receiving the signal indicative of a target object; and transmitting messages to set the vehicle at a predetermined following distance from the target object in response to the speed of the host vehicle being less than or equal to a minimum speed.

In accordance with another aspect, various embodiments of a method for controlling a host vehicle having an adaptive cruise control system comprise receiving a signal indicative of a target object; receiving the speed of the host vehicle; and transmitting messages to at least one of an engine controller, a retarder and a brake controller to maintain the vehicle at a predetermined time gap from the target object upon receiving the signal indicative of a target object. The method includes transmitting messages to at least one of the engine controller, the retarder and the brake controller to set the vehicle at a predetermined following distance from the target object in response to the speed of the host vehicle being less than a minimum speed.

DETAILED DESCRIPTION

FIG. 1illustrates an adaptive cruise control system (ACC)10. The ACC10includes a radar controller14. The radar controller14transmits and receives radar signals, which are electromagnetic waves used to detect an object's presence, longitudinal distance, lateral distance, speed and direction with respect to the host vehicle. The radar controller14can detect multiple stationary or moving objects within a wide range to the front and sides of the host vehicle. The radar and control functions may be in a single controller or the radar function may be in a separate sensing device. The radar controller14may be of the type used in the Bendix® Wingman® Fusion™ Driver Assistance System from Bendix Commercial Vehicle Systems LLC of Elyria Ohio.

The radar controller14includes a processor with control logic20for receiving and transmitting messages to control the ACC10. The control logic20may include volatile, non-volatile memory, solid state memory, flash memory, random-access memory (RAM), read-only memory (ROM), electronic erasable programmable read-only memory (EEPROM), variants of the foregoing memory types, combinations thereof, and/or any other type(s) of memory suitable for providing the described functionality and/or storing computer-executable instructions for execution by the control logic20.

The control logic20may be configured in a speed mode, a time gap mode or a following distance mode. When the calculated time to an object is below a predetermined time to an object, a following alert is transmitted as a threat of a possible collision with the object exists due to the longitudinal distance, lateral distance and relative velocity of the object with respect to the host vehicle. The control logic20may also intervene automatically by transmitting messages to decelerate the vehicle in order to maintain the preset time gap.

The ACC10includes at least one camera controller16. The camera controller16uses video signals to detect an object's presence, size, longitudinal distance and lateral distance with respect to the host vehicle. The camera controller16can detect multiple stationary or moving objects within a wide range to the front and sides of the host vehicle. The camera controller16may be of the type used in the Bendix® Wingman® Fusion™ Driver Assistance System from Bendix Commercial Vehicle Systems of Elyria Ohio.

The ACC10includes a proprietary vehicle communications bus26for communications between the radar controller14and the camera controller16. The control logic20is capable of receiving the video signals from the camera controller16on the proprietary communications bus26. The radar controller14may also transmit the radar signals on the proprietary communications bus26. The information from the radar signals and video signals is used by the control logic20to determine the longitudinal difference and lateral offset of the detected object from the host vehicle.

The ACC10may include a display18in the cab of the host vehicle. The display18may be an input device for a driver to set the preset time gap. The display18may show the distance of the host vehicle from the detected object and a preset time gap to object. The display18may show the status of the ACC10or other systems on the host vehicle.

The ACC10also communicates using a public vehicle communications bus22connected to the radar controller14, the camera controller16, the display18, and other controllers on the vehicle. The radar controller14may transmit a braking control signal on the vehicle communications bus22. The radar controller14can also transmit a braking activity indicator, a distance to the detected object and a status signal to the vehicle communications bus22.

A braking system controller12communicates with the ACC10via the vehicle communications bus22. The braking system controller12receives braking control signals and controls the service brakes of the host vehicle. The braking system controller12may also communicate the speed of the host vehicle on the vehicle communications bus22. The braking system controller12includes an output for communicating with at least one brake control device24. The brake control device24may be an electro-pneumatic device that provides air to the service brakes on a wheel end in response to control signals from the braking system controller12when the host vehicle is an air-braked commercial vehicle. The braking system controller12may be of the type used in the Bendix® ABS-6 Advanced with ESP® System from Bendix Commercial Vehicle Systems of Elyria Ohio.

A retarder28communicates with the ACC10via the vehicle communications bus22. The retarder28receives deceleration messages and assists in slowing the vehicle in response to the deceleration messages. An engine controller30communicates with the ACC10via the vehicle communications bus22. The engine controller30is capable of receiving deceleration messages and slows the vehicle in response. The engine controller30also receives acceleration messages and propels the vehicle in response. The engine controller30may also transmit the speed of the host vehicle on the vehicle communications bus22. When a target vehicle is detected, the ACC10transmits messages to one or more of the braking system controller12, the engine retarder28and the engine controller30to maintain the host vehicle at a preset time gap (e.g., 3 seconds or the like) behind the target vehicle.

An other controller32may also communicate with the ACC10via the vehicle communications bus22. The other controller32may be a dash controller or chassis controller that may communicate vehicle speed on the vehicle communications bus22. The other controller32may be a controller having several switch inputs so that the driver can set the predetermined time gap and/or disable the ACC10.

Therefore, a controller for a host vehicle having adaptive cruise control comprises an input for receiving a signal indicative of a detected target object, an input for receiving the speed of the host vehicle and control logic. The control logic is capable of transmitting messages to maintain the vehicle at a preset time gap from the target object upon receiving the signal indicative of a target object and transmitting messages to set the vehicle at a predetermined following distance from the target object in response to the speed of the host vehicle being less than or equal to a minimum speed.

FIG. 2illustrates a method40of implementing the transition from a time gap mode of the ACC10to a following distance mode according to one example of the invention. In step42, the driver of the host vehicle enables the ACC10to maintain a set speed, 55 miles per hour for example.

In step44, the radar controller14and/or camera controller16determine if a target vehicle is in front of the host vehicle. If no target vehicle is in front of the host vehicle, the method40returns to step42. If a target vehicle is detected, the method40goes to step46. In step46, the radar controller14will set the ACC10in a time gap mode. When the ACC10is normally enabled, a time gap mode is the default mode when a target vehicle is detected. The time gap mode setting can be preset by the vehicle manufacturer or can be adjustable by the driver of the vehicle. Normally the time gap is set between 1.8 seconds and 3.5 seconds. The preset time gap is representative of the time that would be required by the host vehicle to travel forward and reach the target vehicle's current location.

In one example, the time gap may be preset by the vehicle operator or the fleet manager at 2.8 seconds. Therefore, the radar controller14will transmit deceleration and acceleration commands to the braking controller12, retarder28and/or engine30to maintain the host vehicle behind the target vehicle such that there would be 2.8 seconds for the host vehicle to brake before potentially colliding with a suddenly stopped target vehicle. The preset time gap may be adjusted by the driver of the host vehicle in some configurations of ACC, but normally a driver would not be allowed to set the time gap below a minimum time gap of 1.8 seconds.

The radar controller14receives the speed of the host vehicle from the braking controller12or the engine30. In step48, the radar controller14compares the host vehicle speed to a predetermined minimum speed. In one example, the predetermined minimum speed is between about three (3) miles per hour and about ten (10) miles per hour. In another example, the predetermined minimum speed is about five (5) miles per hour. If the speed of the host vehicle is greater than the predetermined minimum speed, the method40returns to step46. If the speed of the host vehicle is less than or equal to the predetermined minimum speed, the method40proceeds to step50.

In step50, the radar controller14sets the ACC10in a following distance mode. In a following distance mode, the preset time gap is no long used and a predetermined distance between the target vehicle and host vehicle is maintained. In one example, the predetermined distance is about twenty (20) feet. Therefore, the radar controller14will transmit deceleration and acceleration commands to the braking controller12, retarder28and engine30to maintain the host vehicle behind the target vehicle such that there is consistently about twenty (20) feet between the fender of the host vehicle and the bumper of the target vehicle.

In one example, the following distance may be set using the preset time gap. If the preset time gap was 2.8 seconds, the following distance would be set at 20.5 feet because 20.5 feet is the distance the vehicle would be when the host vehicle was traveling at five (5) mph. If the preset time gap was 1.8 seconds, the following distance would be set at 13.2 feet. In yet another example, the following distance is set based on the speed the host vehicle was traveling when the ACC10is set in the following distance mode. For example, if the time gap was 2.8 seconds and the ACC10is set in following distance mode at eight (8) mph, the following distance would be set at 32.9 feet.

This following distance allows for the host vehicle to brake gradually well before potentially colliding with a suddenly stopped target vehicle. When the host vehicle is a tractor trailer or other large commercial vehicle, the distance required to come to a complete stop once braking is initiated is generally longer than for a small car or motorcycle. It is desired to have fewer and less aggressive brake applications for driver comfort. If the preset time gap was maintained as the host vehicle was slowing down, the distance to the target vehicle may in turn become infinitely small, as will be shown onFIG. 3.

In step52, the radar controller14and camera controller16determine if the target vehicle is still present. If the target vehicle is still present, the radar controller14and camera controller16continue to monitor the target vehicle in step54. From step54, the method40goes to step50to remain in the following distance mode.

If the target vehicle has moved out of range of the host vehicle, by speeding up or leaving the roadway and no other target vehicle is detected by the radar controller14and/or camera controller16in step52, the radar controller14will return the host vehicle to the regular cruise control mode by returning to step42. Any brake application will be released gradually as the vehicle is allowed to return to the speed mode. The method40will remain in the speed mode until another target vehicle is identified.

Therefore, a method for controlling a host vehicle having an adaptive cruise control system comprises receiving a signal indicative of a target object, receiving the speed of the host vehicle and transmitting messages to at least one of an engine controller, a retarder and a brake controller to maintain the vehicle at a predetermined time gap from the target object upon receiving the signal indicative of a target object. The method includes transmitting messages to at least one of the engine controller, the retarder and the brake controller to set the vehicle at a predetermined following distance from the target object in response to the speed of the host vehicle being less than a minimum speed.

FIG. 3is a graphical representation60of the difference between the time gap mode, illustrated by line62, and the following distance mode, illustrated by line64. Speed in miles per hour is shown on the X-axis and a distance to a detected target vehicle in feet is shown on the Y-axis.

If the time gap is set at 2.8 seconds, then the distance to a target would be about forty (40) feet when the host vehicle is traveling at ten (10) miles per hour, as shown on line62. At about five miles per hour, the distance to the target vehicle is about twenty (20) feet. However, at four miles per hour, the distance is reduced to about sixteen (16) feet, which may not be enough space to brake comfortably in order to avoid a collision if the target vehicle were to suddenly stop. At two (2) miles per hour, which is a feasible speed for slow traffic, the distance would be reduced to about eight (8) feet in the time gap mode.

However, if the radar controller14as described is programmed to transition ACC10to a following distance only mode at a predetermined low speed, such as about five (5) miles per hour, the distance to the target would remain at about twenty (20) feet as long as the speed of the host vehicle was about five (5) miles per hour or less, as shown by line64. The twenty (20) feet represents the ACC10transitioning to the following distance mode at about five (5) miles per hour when the time gap was set at 2.8 seconds.

Systems that use engine only modes instead of braking to deceleration in response to a detected object also benefit from this invention.