Lane-keeping emergency steering assistance when braking

Abstract

Lane-keeping emergency steering assistance system for keeping a motor vehicle moving at a speed in a lane during a braking event, the system comprising: an object sensor for detecting the presence of an object at a distance from the motor vehicle on a current path of the motor vehicle from which the distance from the object to the motor vehicle can be determined, the object sensor transmitting a signal in response to the presence of the object in front of the motor vehicle and providing data from which the distance from the object to the motor vehicle is determined; a speed sensor that sends a signal and provides data from which the speed of the motor vehicle is determined; a control unit communicating with the object sensor and the speed sensor, wherein the control unit calculates a time to collision (Time To Contact, TTC) with the detected object; and a steering system responsive at least in part to actuation by the control unit; wherein, if the calculated TTC is less than a predetermined TTC, the controller provides a control input during the braking event to shorten a linear distance traveled by the motor vehicle from a predetermined path in the lane.

Description

The present invention relates generally to a system and method for shortening the effective stopping distance on which a moving motor vehicle approaching an object located within the current path of the motor vehicle is to be decelerated, preferably to a standstill. More particularly, the present invention relates to a system for inducing a lateral steering input to effectively shorten the linear path travelled by the motor vehicle during the braking event as compared to a predetermined in-lane path, and a method for accomplishing this.During operation of a motor vehicle, certain unrecognized and unexpected events, such as the sudden appearance of an animal or pedestrian or the sudden deceleration of a preceding motor vehicle located in front of the primary motor vehicle, may result in situations where an immediate response is desirable to avoid a collision. Recently, on-board sensors are increasingly used to provide a signal to a vehicle control unit indicating the presence of objects located ahead in the travel path of the motor vehicle and thereby alert the driver.The prior art relating to collision avoidance systems is disclosed, for example, in documents DE 10 2012 214 990 A1 and U.S. Pat. No. 8 527 172 B2.Using the forward speed of the vehicle and the measured distance to the forward object, a time to contact (TTC) with the detected object may be calculated using the vehicle controller. In some cases, the calculated TTC may be insufficient for the braking system of the motor vehicle to stop the motor vehicle in the current lane. In such driving situations, a solution for the driver or the steering system operated by the vehicle control unit, if present, was to generate an abrupt steering input and thereby attempt to steer around the object ahead in the path of travel of the motor vehicle. Since such abrupt steering maneuvers tend to cause the motor vehicle to shear out of its current lane, such maneuvers are undesirable. Therefore, a solution which addresses this problem would be advantageous.The solution disclosed herein is a system and method for increasing effective TTC with a detected object. In combination with the application of steering assist capability, a system and method are disclosed herein wherein lateral steering input is induced with or without driver input to the steering of the motor vehicle. The lateral steering input may be a side-to-side oscillatory steering input expressed as a lateral steering maximization such as a sine wave modulated within a defined range of frequencies and amplitudes, thereby shortening the linear distance travelled by the motor vehicle in the lane from a predetermined path in the lane.Thus, the solution provided by the present system and method that increases the effective TTC for a motor vehicle body is a relatively inexpensive solution that improves the ability to stop a motor vehicle in a shorter effective path.According to one aspect of the present disclosure, a lane-keeping emergency steering assist system for keeping a motor vehicle in a lane during a braking event includes an object sensor for detecting the presence of an object on a current path of the motor vehicle from which the distance from the object to the motor vehicle can be determined, wherein the object sensor transmits a signal and provides data from which the distance from the object to the motor vehicle is determined in response to the presence of the object in front of the motor vehicle. A speed sensor sends a signal and provides data from which the forward speed of the motor vehicle is determined. A controller communicating with the object sensor and the speed sensor calculates a TTC with the detected object. A steering system responds at least in part to actuation by the controller. If the calculated TTC is less than a predetermined TTC, the controller provides a lateral steering input during the braking event to shorten the linear distance travelled by the motor vehicle from a predetermined in-lane path.Yet another aspect of the present disclosure relates to a lane keeping emergency steering assist system in which the lateral steering input is a side-to-side pendulum steering input expressed as an oscillating wave modulated within a defined range of frequencies and amplitudes.Yet another aspect of the present disclosure relates to a lane keeping emergency steering assist system wherein the steering input for a swing motion from side to side is expressed as a sine wave modulated within a range of frequencies and amplitudes.Yet another aspect of the present disclosure relates to a lane keeping emergency steering assist system wherein the steering input for a rocking motion from side to side is expressed as a plurality of superimposed curves.Another aspect of the present disclosure relates to a lane keeping emergency steering assist system wherein the steering system is electronically operated.Yet another aspect of the present disclosure relates to a lane keeping emergency steering assist system wherein the steering system is hydraulically actuated.An additional aspect of the present disclosure relates to an emergency steering assist lane keeping system, wherein the object sensor is a forward facing camera for determining the distance and a rate of change of the distance to the object.Yet another aspect of the present disclosure relates to a lane keeping emergency steering assist system wherein the object sensor is a forward radar based transmitter and receiver for determining the distance and a rate of change of the distance to the object.Yet another aspect of the present disclosure relates to a lane keeping emergency steering assist system further comprising a manually operated brake system, wherein if the calculated TTC is less than a predetermined TTC, the controller provides the lateral steering input and the brake system is manually engaged.Another aspect of the present disclosure relates to a lane keeping emergency steering assist system, further comprising a brake system that responds at least in part to actuation by the controller, wherein if the calculated TTC is less than a predetermined TTC, the controller provides a brake input to the brake system in addition to the lateral steering input.Yet another additional aspect of the present disclosure relates to a lane keeping emergency steering assist system wherein the steering input for side-to-side rocking motion expressed as a sine wave modulated within a defined range of frequencies and amplitudes is a function of the group consisting of one or more of the road surface coefficient of friction, ambient temperature, road curvature, current lane recognition capability of the vehicle, forward speed of the vehicle, lateral speed of the vehicle, yaw rate of the vehicle, roll rate of the vehicle, pitch rate of the vehicle, and current TTC.Another aspect of the present disclosure relates to a lane keeping emergency steering assist system wherein the steering input for side to side rocking motion expressed as a sine wave modulated within a defined range of frequencies and amplitudes is also a function of the group consisting of human physiology considerations including lateral acceleration and deceleration.Yet another aspect of the present disclosure relates to a lane keeping emergency steering assist system wherein the steering input for a side-to-side rocking motion, expressed as a sine wave modulated within a defined range of frequencies and amplitudes, allows a driver to maintain overall steering control.Yet another additional aspect of the present disclosure relates to a lane keeping emergency steering assist system wherein the side-to-side pendulum steering input expressed as a sine wave modulated within a defined range of frequencies and amplitudes is obtained by a drive-by-wire system that decouples the side-to-side pendulum steering input from a driver's steering wheel.An additional aspect of the present disclosure relates to a lane keeping emergency steering assist system, wherein the steering system includes a front wheel steering assembly and the lateral steering input is directed to the front wheel steering assembly.Another aspect of the present disclosure relates to a lane keeping emergency steering assist system, wherein the steering system includes a rear wheel steering assembly and the lateral steering input is directed to the rear wheel steering assembly.Yet another aspect of the present disclosure relates to a lane keeping emergency steering assist system, wherein the steering system comprises a front wheel steering assembly and a rear wheel steering assembly, and the lateral steering input is directed to the front wheel steering assembly and / or the rear wheel steering assembly.Another aspect of the present disclosure relates to a steering assist system for a motor vehicle, comprising a sensor for detecting the presence of an object and its distance from the motor vehicle, a speed sensor, a control unit communicating with the sensor and the speed sensor, and a steering system responsive to the control unit, the control unit selectively providing a lateral steering input to shorten the linear distance travelled by the motor vehicle.Yet another additional aspect of the present disclosure relates to a method of providing lane keeping emergency steering assist for keeping a motor vehicle within a lane during a braking event, the method comprising the steps of: detecting the presence of an object on a current path of the motor vehicle and providing data from which the distance from the object to the motor vehicle can be determined; transmitting a signal responsive to the presence of the object in front of the motor vehicle and transmitting data to a control unit from which the distance from the object to the motor vehicle is determined; transmitting a signal and transmitting data to the control unit from which the forward speed of the motor vehicle is determined; calculating a TTC with the detected object; and selectively actuating a steering system at least partially in response to actuation by the controller, wherein if the calculated TTC is less than a predetermined TTC, the controller provides a lateral steering input expressed as an oscillating curve modulated within a defined range of frequencies and amplitudes during the braking event to shorten the linear distance travelled by the motor vehicle from a predetermined path in the lane.Yet another aspect of the present disclosure relates to a method further comprising the step of selectively actuating a brake system at least in part in response to actuation by the controller, wherein if the calculated TTC is less than a predetermined TTC, the controller provides a brake input to the brake system and the controller provides a steering input for a lateral to lateral movement to shorten the linear distance travelled by the motor vehicle from a predetermined path in the lane.These and other aspects, objects, and features of the present disclosure will become apparent and apparent to those skilled in the art upon studying the following specification, claims, and accompanying drawings.In the drawings, there are shown: FIG. 1 is a perspective view of a motor vehicle incorporating the emergency steering assist lane-keeping system for keeping a motor vehicle in a lane during a braking event according to the present disclosure; FIG. 2 is a top view of a motor vehicle incorporating the emergency steering assist lane keeping system for keeping a motor vehicle in a lane during a braking event according to the present disclosure; FIG. 3 is a schematic view of a motor vehicle in which the emergency steering assist lane keeping system is used to keep a motor vehicle in a lane during a braking event according to the present disclosure; FIG. 4 shows a graphical representation of the steering angle of the front wheel arrangement as a function of time during a simulated emergency stop of a motor vehicle according to the prior art; FIG. 5 shows a graphical representation of the distance covered as a function of time during a simulated emergency stop of a motor vehicle according to the prior art; FIG. 6 shows a graphical representation of the transverse acceleration as a function of time during a simulated emergency stop of a motor vehicle according to the prior art; FIG. 7 shows a graphical representation of the lateral offset with respect to the longitudinal direction of travel during a simulated emergency stop of a motor vehicle according to the prior art; FIG. 8 is a graph of steering angle of the front wheel assembly versus time during simulated emergency stop of a motor vehicle utilizing the emergency steering assist lane keeping system and method for keeping a motor vehicle within a lane during a braking event in accordance with the present disclosure; FIG. 9 is a graph of distance traveled versus time during a simulated emergency stop of a motor vehicle utilizing the emergency steering assist lane-keeping system and method for keeping a motor vehicle within a lane during a braking event, in accordance with the present disclosure; FIG. 10 is a graph of lateral acceleration versus time during a simulated emergency stop of a motor vehicle utilizing the emergency steering assist lane-keeping system and method for keeping a motor vehicle within a lane during a braking event in accordance with the present disclosure; and FIG. 11 is a graphical representation of lateral offset with respect to the longitudinal direction of travel during simulated emergency braking of a motor vehicle utilizing the in-lane emergency steering assist system and method of maintaining a motor vehicle within a lane during a braking event in accordance with the present disclosure.For purposes of description herein, the terms "upper(r / s)", "lower(r / s)", "right(r / s)", "left(r / s)", "rear(r / s)", "front(r / s)", "vertical(r / s)", "horizontal(r / s)", and their derivatives refer to the orientation of the invention as in FIG. 1. It is also to be understood that the specific devices and methods illustrated in the accompanying drawings and described in the following description are simply exemplary embodiments of the inventive concepts defined in the appended claims. Therefore, certain dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.The motor vehicle 10 suitable for use in connection with the system and method of the present disclosure is illustrated in FIGS. 1 and 2 and includes various relevant features. These features include an automotive steering system 12, an automotive brake system 14, an automotive drive system 16, and a vehicle control unit 18.As shown, the motor vehicle steering system 12 preferably includes a drive-by-wire steering system having an electrical or electronic control interface for communicating steering inputs from a steering wheel 20 to the vehicle control unit 18. However, other steering systems, such as an electro-hydraulic steering system or an electro-mechanical steering system, may also be used in connection with the present disclosure. The motor vehicle steering system 12 preferably includes a front wheel steering assembly 22 and an electrically-driven steering gear assembly 24 mechanically coupled to the front wheel steering assembly 22. The steering wheel 20 is arranged in the passenger compartment 26 of the motor vehicle 10 and is actuated by the driver of the motor vehicle 10. The steering wheel 20 also preferably includes an electrical or electronic control interface for communicating with the vehicle control unit 18, wherein steering input signals from the driver are transmitted, processed, and used to generate output signals to the electrically-driven steering gear assembly 24 to actuate the front wheel steering assembly 22 via the steering wheel 20. Here, it is further conceivable that a rear wheel steering assembly 28 is combined with or used independently of the front wheel steering assembly 22 according to the present disclosure.The motor vehicle brake system 14 similarly preferably includes a brake-by-wire (electronic brake system) having an electrical or electronic control interface for communicating with the vehicle control unit 18. However, other braking systems, such as an electro-hydraulic braking system or an electro-mechanical braking system, may also be used in conjunction with the present disclosure. In such a preferred embodiment, the motor vehicle brake system 14 includes an electric brake 34 disposed on a front wheel driven assembly 36 on either side of the motor vehicle 10. Actuation of a brake pedal 30 in the passenger compartment 26 of the motor vehicle 10 by the driver of the motor vehicle actuates a sensor 32, which in turn generates a brake input signal that is communicated to, processed, and used with the vehicle control unit 18 to generate output signals to the electric brake 34, which in turn actuates a friction surface that is pressed against a corresponding rotating surface on the front wheel driven assembly 36. Although the motor vehicle steering system 12 and the motor vehicle braking system 14 discussed above preferably rely on the use of digital signals to control steering and braking as illustrated, the steering system 12 and the motor vehicle braking system 14 may also use analog signals.The motor vehicle propulsion system 16 preferably includes an internal combustion engine 38 controlled by the vehicle control unit 18. Alternatively, a separate engine control unit may be used. The internal combustion engine 38 is preferably controlled in a conventional manner by the use of an accelerator pedal 40 in combination with an air and fuel metering system, such as a fuel injection system, carburetor or other internal combustion engine fuel delivery system. The motor vehicle propulsion system 16 may alternatively include an electric motor (not shown), either alone or in combination with the internal combustion engine 38. The motor vehicle propulsion system 16 preferably includes a transmission 44 for transmitting engine torque to the front wheel driven assembly 36. However, within the scope of this disclosure, it is conceivable to consider a system that uses an electric motor (not shown) disposed on each front wheel driven assembly 36, either as a battery powered system or in combination with an internal combustion engine. In such a motor vehicle 10, it is further conceivable that the operation of the electric motor on each front wheel driven assembly 36 may be reversed to generate or increase the braking force discussed above and to recover energy for recharging the motor vehicle battery, if any.The vehicle control unit 18 preferably includes a data processor 46 and a data storage device 48 for processing data relating to the forward speed of the motor vehicle 10 (by a speed sensor 50), ambient temperature (by a temperature sensor 52), current lane detection capability (by each of a pair of lane monitoring sensors 54), lateral speed of the vehicle (by a lateral speed sensor 56), yaw rate of the vehicle (by a yaw accelerometer 58), roll rate of the vehicle (by a roll accelerometer 60), and pitch rate of the vehicle (by a pitch accelerometer 62). The lane monitoring sensors 54 are used to detect the lateral distance allowed for the motor vehicle 10 to travel in a lane L. Other driving factors such as the friction coefficient of the road surface may be calculated from the above data.A forward facing sensor 64 is provided to detect the presence of an object O on the current forward travel path P of the motor vehicle 10 and, in combination with the vehicle control unit 18, determine the distance from the object O to the motor vehicle 10 and the rate of change of that distance. The forward sensor 64 may be a forward camera for determining the distance and rate of change of distance to the object. Alternatively, the forward sensor 64 may be a forward radar-based transmitter and receiver for determining the distance and rate of change of distance to the object. Other potential forward-facing sensors may use laser technology or ultrasound technology. In particular, in the event that a camera is used as the forward-facing sensor 64, the forward-facing sensor 64 may preferably also provide information to the vehicle control unit 18 that determines the road curvature in front of the motor vehicle 10.Upon detection of an object O on the current forward path of travel of the motor vehicle 10, the forward sensor 64 sends a signal to the vehicle controller 18 which, depending on the type of forward sensor 64, processes the signal to determine the distance from the motor vehicle 10 to the object O, the rate of decrease of the distance between the motor vehicle 10 and the object O, and the calculated available stopping distance within which the motor vehicle 10 can be brought to a full standstill within the current lane L of the motor vehicle 10. That is, the vehicle control unit 18 calculates a TTC with the object O. The vehicle control unit 18 then compares the calculated TTC with the object O with the available stopping distance within which the motor vehicle 10 can be brought to a full standstill within the current lane L of the motor vehicle 10, or the safe stop distance (SSD).Based on the forward speed of the motor vehicle 10, the road surface coefficient of friction, and the other factors taken into account in the calculation of the available stopping distance corresponding to the safe stopping distance SSD, if the distance from the motor vehicle 10 to the object O is greater than the safe stopping distance SSD, the vehicle control unit 18 generates a warning signal for the driver so that the driver can depress the brake pedal 30 to activate the brake system 14 and bring the motor vehicle 10 to a complete stop within the current lane L of the motor vehicle before a collision with the object O. Alternatively, if the vehicle is equipped with such a function and activated, the vehicle controller 18 may directly generate a signal to activate the brake system 14 and bring the motor vehicle 10 to a full standstill within the current lane L of the motor vehicle 10 prior to a collision with the object O.However, if the TTC with the object O is below the predetermined safe stopping distance value SSD, meaning that the distance from the motor vehicle 10 to the object O is less than the calculated available stopping distance within which the motor vehicle 10 may be brought to a full standstill within the current lane L of the motor vehicle 10 before a collision with the object O, the vehicle control unit 18 implements the system and method of the present disclosure. As before, the vehicle control unit 18 preferably generates a warning signal to the driver so that the driver can depress the brake pedal 30 to activate the brake system 14 of the motor vehicle and begin to reduce the forward speed of the motor vehicle 10 prior to colliding with the object O to minimize the severity of a possible impact. Alternatively, even in this case, if the vehicle is equipped with such a function and is activated, the vehicle control unit 18 may directly generate a signal to activate the brake system 14 and start reducing the forward speed of the motor vehicle.Additionally, if the TTC with object O is below a predetermined value for the safe stopping distance SSD, the vehicle controller 18 generates a curve function and sends a signal to the motor vehicle steering system 12 to cause a lateral steering input during the braking event that actually extends over the total distance LD that is actually traveled by the motor vehicle 10. Since the total travel LD has a substantial transverse component, the linear travel travelled by the motor vehicle 10 is shortened compared to a predetermined travel P in the lane. The predetermined path P is typically preferably the center path within the lane width W of the lane, but curvatures of the lane L in front of the vehicle may require departure from this center path. As discussed below, the lateral steering input may be a side-to-side oscillating steering input and may also be a sine wave modulated within a defined range of frequencies and amplitudes depending on the TTC and the available calculated safe stopping distance SSD. That is, if more aggressive application of the present system and method is required due to a significant difference between the TTC and the calculated safe stopping distance SSD, the frequency and amplitude of the curve function may be maximized within the safety limits of known capabilities and behavior of the motor vehicle 10. If opposite conditions are present, a more moderate frequency and amplitude may be selected.For example, FIGS. 4-11 show comparative simulated applications of the concept disclosed herein during a simulated emergency braking event. At both events, the speeds of the motor vehicle 10 are decreased from 60 km / h to 0 km / h within about 4 seconds, with an input pressure of the motor vehicle brake system 14 corresponding to a brake pressure of 3 MPa, which is equivalent to a full brake force. The first simulation is shown in FIGS. 4-7. As shown in FIG. 4, there is no steering input for side-to-side pendulum motion, and as shown in FIG. 6, there is no lateral acceleration during the braking event. As further illustrated in FIGS. 5 and 7, the total effective stopping distance is 33.3 linear meters in the longitudinal direction.In contrast, the second simulation is shown in FIGS. 8-11 to which the system and method of the present disclosure are applied. As shown in FIG. 8, the front wheel steering assembly 22 is supplied a side-to-side sinusoidal swing steering input at a frequency of about 20 Hz that causes significant lateral acceleration during the braking event, as shown in FIG. 10. As a result, the total effective stopping distance was calculated to be about 29 meters in the longitudinal direction as shown in FIGS. 9 and 11. The difference of 4.3 meters represents a shortening of the linear stopping distance of the motor vehicle 10 by 12%.However, the system and method of the present disclosure is not intended to be limited to any particular curve function, such as a sine wave or any particular oscillation frequency or amplitude. Although the use of a sine wave function has been considered a solution to modulate the lateral steering input, other curve functions may also be useful in modulating the lateral steering input. For example, a predefined map may be used to define a lateral steering input based on one or more of the following factors: road surface friction coefficient, ambient temperature, road curvature, current lane recognition capability of the vehicle, forward speed of the vehicle, lateral speed of the vehicle, yaw rate of the vehicle, roll rate of the vehicle, and pitch rate of the vehicle, and the currently calculated TTC.One result of these factors may be a lateral steering input that results in the motor vehicle 10 being easily driven in a large arc within the lane L, while another result may result in a lateral steering input that begins as a large arc in a first direction and ends with a small arc in the opposite direction. Yet another result may begin with a large arc (to avoid unnecessary rocking motion if the TTC is no longer significant or its significance diminishes) and continue with sinusoidal motions with gradually increasing frequency as the motor vehicle 10 approaches the object O. Also, although the use of 20 Hz has been considered a solution to modulate the lateral steering input in the model, the frequency may also be adjusted based on the factors set forth above, as well as factors from the group consisting of human physiology considerations, including human ability to tolerate lateral accelerations and decelerations.In addition, the frequency may depend on the desire to make the rocking movements as perceptible as possible to the driver of the motor vehicle, which has the advantage of allowing the driver to maintain overall control over the steering. For example, in the case of a full electric motor vehicle steering system 12 (steer-by-wire), the driver need not in any way feel the lateral steering input generated by the vehicle control unit 18 causing a swing motion via the steering of the driver steering wheel 20. Thus, one advantage of the drive-by-wire is that the lateral steering input is decoupled from the driver steering wheel 20 and from the driver. Additionally, it is contemplated that by using a rear steering assembly 28 in combination with the front steering assembly 22 with the driver steering inputs directed to the front steering assembly 22 and with the lateral steering input directed only to the rear steering assembly 28, a method may be provided that allows the driver to maintain control of the steering wheel 20 during operation of the system disclosed herein and execution of the method disclosed herein.The amplitude can also be modified depending on the same factors which determine the choice of the curve function and the frequency. Additionally, the amplitude may also be a function of the curvature of the track L or the total width OW of the track so that a partially sinusoidal rocking motion may be generated, wherein the motor vehicle 10 is controlled to the outermost curvature of the track L or partially traversing a track L (i.e., with a tire across the outer curvature of the track L) to achieve a maximum reduction in speed before TTC. The lateral amplitude may also begin with the greatest amplitude (also to minimize the rocking motion if the TTC is no longer significant or its significance diminishes) and decrease as the system-equipped vehicle approaches object O.Thus, the shape of the curve function and its frequency and amplitude may change depending on the TTC and the factors set forth herein. That is, the shape of the path of the motor vehicle 10 relative to the center of the lane L to the edge of the lane L, as well as the frequency and amplitude of the movement of the motor vehicle 10 to the left and right may vary within a range with defined limits determined by the predefined map. Similarly, multiple superimposed curve functions modulated within a range of frequencies and amplitudes may be applied to effectively extend the available stopping distance of the motor vehicle 10.In operation, the method of providing lane keeping emergency steering assist for keeping a motor vehicle 10 within a lane L during a braking event begins with the step of detecting the presence of an object O on a current path of the motor vehicle 10 and the distance from the object O to the motor vehicle 10 using the forward facing sensor 64 The forward facing sensor 64 then sends a signal responsive to the presence of the object O in front of the motor vehicle 10 and transmits data to the vehicle control unit 18 from which the distance from the object O to the motor vehicle 10 is determined. A sensor 50 for monitoring the forward speed of the vehicle also sends a signal to the vehicle control unit 18, and it transmits data to the vehicle control unit 18, from which data the forward speed of the motor vehicle 10 is determined. The vehicle controller 18 then calculates a TTC with the detected object O. If the calculated TTC is less than a predetermined TTC, the vehicle controller 18 selectively actuates the front wheel steering system 22 or the rear wheel steering system 28 at least in part in response to actuation by the vehicle controller 18 to provide a lateral steering input expressed as an oscillating curve modulated within a defined range of frequencies and amplitudes during the braking event to shorten the linear distance travelled by the motor vehicle 10 from a predetermined path P in the lane L.The system and method disclosed herein thus provide lateral steering input to the motor vehicle steering system 12 with or without driver input. The cross-steering input is preferably expressed as a maximization of cross-steering, such as a sine wave modulated within a defined range of frequencies and amplitudes. Thus, the linear distance travelled by the motor vehicle 10 within the lane L may be shortened from a predetermined distance P in the lane L.It is to be understood that variations and modifications can be made to the system and method described above without departing from the concepts of the present invention, and it is further to be understood that these concepts are intended to be covered by the following claims unless these claims expressly state otherwise.

Claims

A lane-keeping emergency steering assist system for keeping a motor vehicle moving at a speed in a lane during a braking event, the system comprising: an object sensor for detecting the presence of an object at a distance from the motor vehicle on a current path of the motor vehicle from which the distance from the object to the motor vehicle can be determined, the object sensor transmitting a signal and providing data from which the distance from the object to the motor vehicle is determined in response to the presence of the object in front of the motor vehicle; a speed sensor transmitting a signal and providing data from which the speed of the motor vehicle is determined; a controller communicating with the object sensor and the speed sensor, the controller calculating a time to contact (TTC) with the detected object; and a steering system responsive at least in part to actuation by the controller; wherein if the calculated TTC is less than a predetermined TTC, the controller provides a lateral steering input during the braking event to shorten a linear distance travelled by the motor vehicle from a predetermined path in the lane.The emergency steering assist lane keeping system of claim 1, wherein the lateral steering input is a side-to-side rocking steering input expressed as an oscillating wave modulated within a defined range of frequencies and amplitudes.The emergency steering assist lane keeping system of claim 2, wherein the steering input for a swing motion from side to side is expressed as a sine wave modulated within a range of frequencies and amplitudes.The lane keeping emergency steering assist system of claim 2, wherein the steering input for a rocking motion from side to side is expressed as a plurality of superimposed curves.The emergency steering assist lane keeping system of claim 1, wherein the steering system is electronically operated.The lane keeping emergency steering assist system of claim 1, wherein the steering system is hydraulically actuated.The emergency steering assist lane keeping system of claim 1, wherein the object sensor is a forward facing camera for determining the distance and a rate of change of the distance to the object.The emergency steering assist lane keeping system of claim 1, wherein the object sensor is a forward radar based transmitter and receiver for determining the distance and a rate of change of the distance to the object.The emergency steering assist lane keeping system of claim 1, further comprising a manually operated brake system, wherein if the calculated TTC is less than a predetermined TTC, the controller provides the lateral steering input and the brake system is manually engaged.The emergency steering assist lane keeping system of claim 1, further comprising a brake system that responds at least in part to actuation by the controller, wherein if the calculated TTC is less than a predetermined TTC, the controller provides a brake input to the brake system in addition to the lateral steering input.

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