WO2015008590A1

WO2015008590A1 - Lane keeping assist apparatus

Info

Publication number: WO2015008590A1
Application number: PCT/JP2014/066755
Authority: WO
Inventors: Hidenobu KINUGASA
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2013-07-19
Filing date: 2014-06-18
Publication date: 2015-01-22
Also published as: JP2015020633A; JP5796607B2

Abstract

Abstract A lane keeping assist apparatus is disclosed, which includes: a lane detecting part that detects a lane in which a vehicle travels; an actuator that generates a force for changing an orientation of the vehicle; and a controller that performs a lane keeping assist control by operating the actuator such that the vehicle travels within the lane, wherein the controller restricts, under a situation where the actuator is operated by the lane keeping assist control, the lane keeping assist control when a steering operation of a driver is not detected and a steering angle speed is greater than or equal to a predetermined speed.

Description

Title of the Invention

LANE KEEPING ASSIST APPARATUS

Technical Field

The disclosure is related to a lane keeping assist apparatus. Background Art

A lane departure prevention apparatus is known which applies a steering force to a steering mechanism for preventing a departure from a traveling lane of a host vehicle (see Patent Document 1, for example) . The lane departure prevention apparatus detects a coefficient of friction of a road and reduces the pulse-like steering force to be applied to the steering mechanism as the coefficient of friction decreases. It is noted that Patent Document 1 discloses only a way of detecting the coefficient of friction using a given vehicle motion model and various parameters such as a vehicle speed, a steering wheel angle, a yaw rate, etc.

[Patent Document 1] Japanese Laid-open

Patent Publication No. 2010-023605

Disclosure of Invention

Problem to be Solved by Invention

However, according to the way of detecting the coefficient of friction using a given vehicle motion model and various parameters such as a vehicle speed, a steering wheel angle, a yaw rate, there is a problem that the detection way is complicated and the process load is great.

Therefore, an object of this disclosure is to provide a lane keeping assist apparatus that can easily and precisely detect a situation where it is not appropriate to continue a lane keeping assist control .

Means to Solve the Problem

According to one aspect of the disclosure, a lane keeping assist apparatus is provided, which includes :

a lane detecting part that detects a lane in which a vehicle travels;

an actuator that generates a force for changing an orientation of the vehicle; and

a controller that performs a lane keeping assist control by operating the actuator such that the vehicle travels within the lane, wherein

the controller restricts, under a situation where the actuator is operated by the lane keeping assist control, the lane keeping assist control when a steering operation of a driver is not detected and a steering angle speed is greater than or equal to a predetermined speed.

The object and advantages of the embodiment will be realized and attained by means of the elements and combinations particularly pointed out in the claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. Advantage of the Invention

According to one aspect of the disclosure, a lane keeping assist apparatus can be obtained which can easily and precisely detect a situation where it is not appropriate to continue a lane keeping assist control.

Brief Description of Drawings

Fig. 1 is a diagram for illustrating a configuration of a lane keeping assist apparatus 100 according to an embodiment.

Fig. 2 is a block diagram for illustrating an example of a control calculating part 15.

Fig. 3 is a flowchart for illustrating an example of an unsuited circumstance determination process performed by an abnormality determining part 18.

Fig. 4 is a flowchart for illustrating another example of the unsuited circumstance determination process performed by the abnormality determining part 18.

Fig. 5 is a flowchart for illustrating an example of the unsuited circumstance determination process performed by an EPS-ECU 21.

Fig. 6 is a diagram for expanding an example of a way of setting a predetermined threshold Th3' .

Description of Reference Symbols

10 LKA-ECU

21 EPS-ECU

22 torque sensor

24 steering sensor 26 steering actuator

34 main switch

100 lane keeping assist apparatus Best Mode for Carrying Out the Invention

In the following, embodiments are described in detail with reference to appended drawings.

Fig. 1 is a diagram for schematically illustrating a configuration of a lane keeping assist apparatus 100 according to an embodiment.

The lane keeping assist apparatus 100 includes a LKA (Lane Keeping Assist) -ECU (Electronic Control Unit) 10. The LKA-ECU 10 may be formed by a microcomputer or the like.

The LKA-ECU 10 is connected to an EPS (Electric Power Steering) system 20 via an appropriate bus such as a CAN (controller area network), etc. The EPS system 20 includes an EPS- ECU 21. The EPS-ECU 21 is connected to a torque sensor 22 for detecting a steering torque (referred to as "driver steering torque" hereinafter) applied to a steering shaft by a driver, and a steering sensor 24 for detecting a steering angle of a steering shaft (or a steering wheel) by the driver.

Further, the EPS-ECU 21 is connected to a steering actuator 26. The EPS-ECU 21 generates, in response to a steering assist demand torque from the LKA-ECU 10, a control torque output to control the steering actuator 26. In this way, a steering torque according to the steering assist demand torque from the LKA-ECU 10 is generated.

The steering actuator 26 may include an arbitrary configuration for generating the steering torque (steering force) . The steering actuator 26 may be a motor that is used for an assist control for adding an assist torque in the steering direction of the driver. For example, the steering actuator 26 may be provided in a steering gear box such that the steering actuator 26 is coaxial with a steering rack (not illustrated) . In this case, the steering actuator 26 may be engaged with the steering rack via a ball screw nut. In this case, the steering actuator 26 assists a movement of the steering rack with a driving force thereof.

The LKA-ECU 10 is connected to the torque sensor 22 and the steering sensor 24 via an appropriate bus such as a CAN. The LKA-ECU 10 directly obtains information about the driver steering torque and the steering angle from the torque sensor 22 and the steering sensor 24. It is noted that the information about the driver steering torque and the steering angle may be indirectly , obtained via the EPS-ECU 21.

The LKA-ECU 10 is connected to a vehicle speed detector 30, a forward camera 32, a main switch 34, etc.

The vehicle speed detector 30 may be a wheel speed sensor, for example. It is noted that the vehicle speed may be calculated based on the rpms of an output shaft of a transmission, a history of vehicle position measurements from a GNSS (global navigation satellite system) receiver, etc.

The forward camera 32 may be a single camera or a stereo camera that captures a scene around the vehicle that mainly includes a predetermined region in front of the vehicle. Photoelectric conversion elements of the forward camera 32 may be CCDs (charge-coupled devices) , CMOSs (complementary metal oxide semiconductors) , etc. The forward camera 32 may output image data, which is obtained by capturing the scene in front of the vehicle, to the LKA-ECU 10.

The main switch 34 is to be operated by a user. The main switch 34 may be provided at any location within a cabin. The main switch 34 may be a mechanical switch or a touch switch. The main switch 34 is an interface with which the user inputs an intention whether to perform the lane keeping assist control described hereinafter to the lane keeping assist apparatus 100. As an example, it is assumed hereinafter that the main switch 34 is turned on when the user expresses an intention to perform the lane keeping assist control. It is noted that a display for informing an ON/OFF status of the main switch 34 (i.e., an ON/OFF status of the lane keeping assist control) may be output in a meter (not illustrated) .

The LKA-ECU 10 may recognize a lane boundary sign from the image data of the forward camera 32 to generate road information. The lane boundary sign represents a road surface sign for delimiting (defining) a traveling lane. For example, the lane boundary sign is a line-shaped sign formed by applying paint which can be recognized from a road surface, such as white paint, in line shape along the road. Further, there is a white line formed in a chromatic color such as yellow or orange, depending on a road rule or a nation. Further, the lane boundary sign includes, in addition to a line- shaped sign, a dotted line or a broken line which has portions in which paint is not applied at a predetermined interval. Further, when the traveling lane is delimited by a three-dimensional object such as bots dots in the United State of America, instead of the paint, such a three-dimensional object is also included in the lane boundary sign. Further, when the traveling lane is delimited by arranging light emitting objects such as lamps or cat's eye along the road, these objects are also included in the lane boundary sign.

Further, the road information may include an angle (yaw angle) φ between a direction of the traveling lane of the vehicle and a forward and backward direction of the vehicle; a lateral displacement X from the center of the traveling lane to the center of the vehicle; and a curvature β of the traveling lane. It is noted that the curvature β of the traveling lane may be derived by scanning luminance information in a horizontal direction on a predetermined interval basis of the imaged data in the vertical direction, detecting horizontal edges with strength greater than a predetermined value, and applying curve fitting (a least squares method or the like) to positions of the detected edges.

The LKA-ECU 10 performs, in cooperation with the EPS-ECU 21, the lane keeping assist control based on the road information. The lane keeping assist control may include an alert control via an information output device such as a buzzer or the meter, and an intervention control for changing an orientation of the vehicle via the steering actuator 26. Alternatively, the lane keeping assist control may include the intervention control. It is noted that it is assumed that the intervention control is a LKA (Lane Keeping Assist) that supports a driver's steering operation such that the vehicle travels to keep the traveling lane; however, the intervention control may be a LDW (Lane Departure Warning) that is operated when the departure from the traveling lane is detected or the like. According to the LKA, the steering torque is constantly assisted according to the lateral displacement with respect to the target traveling line (traveling lane center) , the yaw angle, etc., and, when the departure tendency is detected, the departure reduction with the steering torque is performed. According to the LDW, when the departure tendency is detected, the departure reduction with the steering torque is performed. It is noted that at the time of performing the intervention control the steering torque and a yaw moment with a brake actuator (not illustrated) may be generated or only the steering torque may be generated.

The LKA-ECU 10 may output a steering assist demand flag and a steering assist demand torque to the EPS-ECU 21, as illustrated in Fig. 1. An ON state of the steering assist demand flag corresponds to an ON state of a lane keeping assist function where the LKA-ECU 10 outputs an operation demand (the steering assist demand torque) to the EPS-ECU 21. An OFF state steering assist demand flag corresponds to an OFF state of the lane keeping assist function, that is to say, a system stop state The EPS-ECU 21 may generate the steering torque according to the steering assist demand torque when the EPS-ECU 21 receives the steering assist demand torque under a situation where the steering assist demand flag is in its ON state.

The LKA-ECU 10 includes a control calculating part 15 and an abnormality determining part 18, as illustrated in Fig. 1.

Fig. 2 is a block diagram for illustrating an example of the control calculating part 15. In the example illustrated in Fig. 2, the controlling part 15 includes a departure determining part 121, a target trace line generating part 122, a target lateral acceleration calculating part 123 and a ' target steering torque calculating part 124.

The departure determining part 121 determines whether the vehicle departs from the traveling lane. The departure determination may be implemented by any methods. For example, a departure prediction time is calculated based on the lateral displacement X of the vehicle and detects the departure tendency (departure) if the departure prediction time becomes less than or equal to a threshold.

The target trace line generating part 122, if it is determined that the vehicle departs from the traveling lane, generates the target trace line for reducing the departure. The target trace line may include two lines of a first line and a second line. In this case, the first line is used for the departure reduction and the second line is used for modifying the direction of the vehicle after the departure reduction. The second line may be set substantially straight at the exit of the curve. The target lateral acceleration calculating part 123, if it is determined that the vehicle departs from the traveling lane, calculates a target lateral acceleration such that the vehicle travels along the target trace line. For example, the target lateral acceleration may be calculated as follows, for example.

Target lateral acceleration Gx = GlxV²xp + G2xcp + G3*X

Gl is a feed-forward operator (gain) , G2 is a feedback operator and G3 is a feed-back operator. It is noted that the described calculation method is just one example. The target lateral acceleration may be calculated from the lateral displacement X and the yaw angle φ only, or a speed is included in the feed-back term of the yaw angle cp. Further, as a simple example, the target lateral acceleration may be read from a map in which the target lateral acceleration Gx is associated with the lateral displacement X and the yaw angle cp.

The target steering torque calculating part 124 calculates a target steering torque according to the target lateral acceleration. For example, the target steering torque calculating part 124 determines a gain K according to the vehicle speed, and calculates the target steering torque based on the target lateral acceleration and the gain K with the following formula.

Target steering torque ST = KxGx

The gain K is a function of the vehicle speed considering the fact that the steering torque need to trace the target trace line varies according to the vehicle speed. The target steering torque thus calculated by the target steering torque calculating part 124 is output as the steering assist, demand torque to the EPS-ECU 21.

It is noted that the intervention control may be implemented with a braking force instead of or in addition to the steering assist demand torque. In this case, the control calculating part 15 may calculate a target cylinder pressure difference ΔΡί of the front wheel and a target cylinder pressure difference APr of the rear wheel based on the target lateral acceleration, for example.

APf = 2*Cfx (Gx-Th) /Tr

APr = 2xCrxGx/Tr

Tr is a tread length, and Cf and Cr are conversion factors when the lateral acceleration is converted to the wheel cylinder pressure. Further, Th is a coefficient for making the target cylinder pressure difference ΔΡί of the front wheel less than the target cylinder pressure difference APr of the rear wheel. In the case of the outward departure, the target wheel cylinder pressure of the outward front wheel (front left wheel in the case of the left curve) is made greater than the target wheel cylinder pressure of the inward front wheel by the target cylinder pressure difference ΔΡί, and the target wheel cylinder pressure of the outward rear wheel is made greater than the target wheel cylinder pressure of the inward rear wheel by the target cylinder pressure difference APr. With this arrangement, the yaw moment is generated in the inward direction and the departure can be reduced. Further, in the case of the inward departure, the target wheel cylinder pressure of the outward front wheel (front right wheel in the case of the left curve) is made greater than the target wheel cylinder pressure of the inward front wheel by the target cylinder pressure difference APf, and the target wheel cylinder pressure of the outward rear wheel is made greater than the target wheel cylinder pressure of the inward rear wheel by the target cylinder pressure difference APr. With this arrangement, the yaw moment is generated in the outward direction and the departure can be reduced.

Fig. 3 is a flowchart for illustrating an example of an unsuited circumstance determination process performed by_. an abnormality determining part 18. The process routine illustrated in Fig. 3 may be executed repeatedly every predetermined cycle during the steering assist demand torque is output (i.e., the intervention control is performed).

In step 300, the abnormality determining part 18 determines, based on the driver steering torque information from the torque sensor 22, whether the driver steering torque is less than or equal to a predetermined threshold Thl. The predetermined threshold Thl may be set in any manner. For example, the predetermined threshold Thl may correspond to a maximum value of a possible range of the driver steering torque when the driver does not substantially perform a steering operation. If the driver steering torque is less than or equal to the predetermined threshold Thl, the process routine goes to step 302. On the other hand, if the driver steering torque is not less than or equal to the predetermined threshold Thl, an abnormality time (described hereinafter) is reset to 0 (step 303) , and the process starts from step 300 at the next process cycle.

In step 302, the abnormality determining part 18 determines, based on the steering angle information from the steering sensor 24, whether the steering angle speed is greater than or equal to a predetermined threshold Th2. The steering angle speed is a change in the steering angle with time (a differential value, for example) . The steering angle speed may be a difference with respect to the previous value (or a value · obtained by dividing the difference by a detection cycle) or may be calculated based on the detection values at the latest three or more time points. The predetermined threshold Th2 may be set in any manner. For example, the predetermined threshold Th2 may correspond to a minimum value of a possible range of the steering angle speed when the intervention control is performed under a road circumstance unsuited for the intervention and in a status where the hands of the driver are substantially off the steering wheel, and may be adapted based on experiments or the like. The road circumstance unsuited for the intervention includes a low-μ road, a road with a steep cant, etc. The road circumstance unsuited for the intervention is merely referred to as an "unsuited circumstance" hereinafter. Further, the predetermined threshold Th2 may be a fixed value, or may be varied according to the steering assist demand torque that is currently output, for example. In the latter case, the predetermined threshold Th2 may be varied such that the smaller the steering assist demand torque becomes, the smaller the predetermined threshold Th2 becomes. If the steering assist demand torque is greater than or equal to the predetermined threshold Th2, the process routine goes to step 304. On the other hand, if the steering assist demand torque is not greater than or equal to the predetermined threshold Th2, the abnormality time (described hereinafter) is reset to 0 (step 303) , and the process starts from step 300 at the next process cycle.

In step 304, the abnormality determining part 18 counts up the abnormality time (abnormality duration) . The abnormality time corresponds to a period during which the steering assist demand torque is less than or equal to the predetermined threshold Thl and the steering angle speed is greater than or equal to the predetermined threshold Th2.

In step 306, the abnormality determining part 18 determines whether the abnormality time is greater than or equal to a predetermined threshold Th3. The predetermined threshold Th3 may be set in any manner. For example, the predetermined threshold Th3 may be adapted appropriately in term of detecting the unsuited circumstance as soon as possible as well as in term of increasing a robustness against noise or the like. If the abnormality time is greater than or equal to the predetermined threshold Th3, the process routine goes to step 308. On the other hand, if the abnormality time is not greater than or equal to the predetermined threshold Th3, the abnormality time is not rest and the process starts from step 300 at the next process cycle.

In step 308, the abnormality determining part 18 stops the lane keeping assist function (i.e., the system stops) . Specifically, the abnormality determining part 18 sets the steering assist demand flag to its OFF state and stops the output of the steering assist demand torque.

Under the road circumstance unsuited for the intervention such as a low-μ road, a road with a steep cant, etc., the steering angle speed may become great when the steering torque according to the steering assist demand torque is generated. On the other hand, even under an ordinary road circumstance where the intervention control is appropriately performed, such as a road with an ordinary coefficient of friction, etc., the steering angle speed may become great in the same manner if the driver operates the steering wheel by himself/herself (i.e., if the driver steering torque is applied to the steering wheel) .

In this connection, according to the process illustrated in Fig. 3, when the steering angle speed is greater than or equal to the predetermined threshold Th2 in a situation where the driver steering torque is less than or equal to the predetermined threshold Thl, the unsuited circumstance is detected, which stops the intervention control (output of the steering assist demand torque) . Thus, it becomes possible to precisely detect the unsuited circumstance under a situation where the driver does not perform the steering operation, and appropriately prevent the unsuited circumstance from being performed in such an unsuited circumstance. Further, the determination process can be simple, because the unsuited circumstance is determined based on the driver steering torque information and the steering angle information.

It is noted that if the lane keeping assist function is stopped in step 308 in Fig. 3, the stop status may be kept for a predetermined time afterward. In this case, if the determination result in step 300 or st.ep 302 becomes negative afterwards, the lane keeping assist function may be restored. However, the restoration is performed on the precondition that the main switch 34 is in its ON state.

It is noted that the process illustrated in Fig. 3 is executed by the LKA-ECU 10; however, it may be executed by the EPS-ECU 21 instead. In this case, in step 308, the EPS-ECU 21 may invalidate the steering assist demand torque from the LKA-ECU 10 to stop the lane keeping assist function. The invalidation may be implemented by any methods. For example, the invalidation may be implemented merely by not responding to the steering assist demand torque from the LKA-ECU 10 (not generating the control torque output, for example) . Alternatively, the EPS-ECU 21 may request, as the invalidation process, the LKA-ECU 10 to stop the output of the steering assist demand torque (and set the steering assist demand flag to its OFF state) by informing the LKA-ECU 10 of the fact that the unsuited circumstance is detected.

Further, the unsuited circumstance determination process illustrated in Fig. 3 may be performed independently by the LKA-ECU 10 and the EPS-ECU 21. With this arrangement, even if the LKA- ECU 10 cannot detect the unsuited circumstance due to some abnormality, the lane keeping assist function can be stopped by the EPS-ECU 21, which enhances a failsafe function.

Fig. 4 is a flowchart for illustrating another example of the unsuited circumstance determination process performed by the abnormality determining part 18 of the LKA-ECU 10. The process routine illustrated in Fig. 4 may be executed repeatedly every predetermined cycle during the steering assist demand torque is output (i.e., the intervention control is performed) . The unsuited circumstance determination process illustrated in Fig. 4 is suited for being performed by the LKA-ECU 10 in a configuration in which the unsuited circumstance determination process is performed separately and in parallel by the LKA-ECU 10 and the EPS-ECU 21. In this case, the EPS-ECU 21 may perform the unsuited circumstance determination process illustrated in Fig. 3.

The unsuited circumstance determination process illustrated in Fig. 4 differs from the unsuited circumstance determination process illustrated in Fig. 3 only in that the process of step 300 is omitted. With this arrangement, the LKA-ECU 10 can detect the unsuited circumstance earlier than the EPS-ECU 21. In this case, because the LKA-ECU 10 determines the unsuited circumstance without considering the driver steering torque, the unsuited circumstance may be detected even in the situation where the driver operates the steering wheel by himself/herself . In this connection, the EPS-ECU 21 may stop the lane keeping assist function only when the EPS-ECU 21 also detects the unsuited circumstance (i.e., when the LKA-ECU 10 and the EPS- ECU 21 detects the unsuited circumstance, respectively) .

Fig. 5 is a flowchart for illustrating an example of the unsuited circumstance determination process performed by the EPS-ECU 21. The unsuited circumstance determination process illustrated in Fig. 5 is performed by the EPS-ECU 21 in a configuration in which the unsuited circumstance determination process is performed separately and in parallel by the LKA-ECU 10 and the. EPS-ECU 21. In this case, the LKA-ECU 10 may perform the unsuited circumstance determination process illustrated in Fig. 3 or the unsuited circumstance determination process illustrated in Fig. 4.

In step 500, the EPS-ECU 21 determines, based on the driver steering torque information from the torque sensor 22, whether the driver steering torque is less than or equal to a predetermined threshold Thl' . The predetermined threshold Thl' may be set in any manner. For example, the predetermined threshold Thl' may be the same as the predetermined threshold Thl used in step 300 in Fig. 3; however, preferably, the predetermined threshold Thl' is less than the predetermined threshold Thl. If the driver steering torque is less than or equal to the predetermined threshold Thl' , the process goes to step 502, otherwise the process goes to step 512.

In step 502, the EPS-ECU' 21 determines, based on the steering angle information from the steering sensor 24, whether the steering angle speed is greater than or equal to a predetermined threshold Th2' . The predetermined threshold Th2' may be set in any manner. For example, the predetermined threshold Th2' may be the same as the predetermined threshold Th2 used in step 302 in Fig. 3; however, preferably, the predetermined threshold Th2' is greater than the predetermined threshold Th2. If the steering angle speed is greater than or equal to the predetermined threshold Th2', the process goes to step 504, otherwise the process goes to step 512.

In step 504, the EPS-ECU 21 counts up the abnormality time. The abnormality time corresponds to a period during which the steering assist demand torque is less than or equal to the predetermined threshold Thl' and the steering angle speed is greater than or equal to the predetermined threshold Th2' .

In step 506, the EPS-ECU 21 determines whether the abnormality time is greater than or equal to a predetermined threshold Th3' . The predetermined threshold Th3' may be set in any manner. For example, the predetermined threshold Th3' may be the same as the predetermined threshold Th3 used in step 306 in Fig. 3; however, preferably, the predetermined threshold Th3' is greater than the predetermined threshold Th3. An example of a way of setting the predetermined threshold Th3' is described hereinafter. If the abnormality time is greater than or equal to the predetermined threshold Th3', the process goes to step 508. On the other hand, if the abnormality time is not greater than or equal to the predetermined threshold Th3', the abnormality time is not rest and the process starts from step 500 at the next process cycle.

In step 508, the EPS-ECU 21 determines whether the EPS-ECU 21 receives the steering assist demand torque (greater than 0) from the LKA-ECU 10. If the EPS-ECU 21 receives the steering assist demand torque, the process goes to step 510, otherwise the process goes to step 512. It is noted that in step 508, the EPS-ECU 21 may determine whether the steering assist demand flag is in its ON state, instead of or in addition to determining whether the EPS-ECU 21 receives the steering assist demand torque from the LKA-ECU 10. In this case, if the EPS-ECU 21 receives the steering assist demand torque from the LKA-ECU 10 and the steering assist demand flag is in its ON state, the process goes to step 510, otherwise the process goes to step 512. Alternatively, in this case, if the EPS-ECU 21 receives the steering assist demand torque from the LKA-ECU 10 or the steering assist demand flag is in its ON state, the process goes to step 510, otherwise the process goes to step 512.

In step 510, the EPS-ECU 21 determines that the LKA-ECU 10 is abnormal and generates (registers) diagnostic information that represents the abnormality of the LKA-ECU 10. Correspondingly, the EPS-ECU 21 invalidates the steering assist demand torque from the LKA-ECU 10 to stop the lane keeping assist function. The invalidation may be implemented by any methods. For example, the invalidation may be implemented merely by not responding to the steering assist demand torque from the LKA-ECU 10. Alternatively, the EPS-ECU 21 may request, as the invalidation process, the LKA-ECU 10 to stop the output of the steering assist demand torque (and set the steering assist demand flag to its OFF state) by informing the LKA-ECU 10 of the fact that the unsuited circumstance is detected.

In step 512, the EPS-ECU 21 determines that the LKA-ECU 10 is normal, and the process starts from step 500 at the next process cycle. At that time, if the current value of the abnormality time is greater than 0, the abnormality time is reset to 0.

According to the unsuited circumstance determination process illustrated in Fig. 5, because the unsuited circumstance is determined by the EPS- ECU 21 for redundancy, the lane keeping assist function can be stopped under the unsuited circumstance. In other words, the failsafe function is increased. Further, the EPS-ECU 21 can detect the abnormality of the LKA-ECU 10 and generates the diagnostic information.

In the case of a configuration in which the EPS-ECU 21 performs the unsuited circumstance determination process illustrated in Fig. 5 and the LKA-ECU 10 performs the unsuited circumstance determination process illustrated in Fig. 3 or the unsuited circumstance determination process illustrated in Fig. 4 separately and in parallel, it is necessary to prevent the diagnostic information from being registered by the process of step 510 when the LKA-ECU 10 is not abnormal.

Thus, in the example illustrated in Fig. 5, preferably, at least one of three conditions is met. The conditions includes a condition that the predetermined threshold Thl' is less than the predetermined threshold Thl used in step 300 in Fig. 3, a condition that the predetermined threshold Th2' is greater than the predetermined threshold Th2 used in step 302 in Fig. 3, and a condition that the predetermined threshold Th3' is greater than the predetermined threshold Th3 used in step 306 in Fig. 3. With this arrangement, such a situation where the process of step 510 is performed before the LKA- ECU 10 normally detects the unsuited circumstance can be reduced.

In this connection, a delay, such as a delay in the determination process of the LKA-ECU 10, a delay in communication to the EPS-ECU 21, a delay in the process of the EPS-ECU 21, etc., may be considered in setting the predetermined threshold Th3' .

Fig. 6 is a diagram for expanding an example of a way of setting the predetermined threshold Th3' . In Fig. 6, various delay factors are illustrated.

First, discontinuation in the communication may happen at the time of the transmission from the steering sensor 24 (and the torque sensor 22) to the LKA-ECU 10, via the CAN, for example. It is noted in Fig. 6 that the dotted arrows schematically illustrate the discontinuation. Thus, there is a delay of time Tl, which is equal to the product of a communication cycle and a permissible number of discontinuation, at this timing . Next, at the time of the calculation process of the LKA-ECU 10, there is a delay due to the number of determination (a time corresponding to the predetermined threshold Thl, for example) and other delay times (a delay due to a difference between a reception timing from the steering sensor 24 and the process cycle, illustrated in Fig. 6, for example) . Thus, there is a delay of time T2, which reflects these delay factors, at this timing.

Next, discontinuation in the communication may happen at the time of the communication from the LKA-ECU 10 to the EPS-ECU 21. It is noted that in Fig. 6 dotted arrows schematically illustrate the discontinuation. Thus, there is a delay of time T3, which is equal to the product of a communication cycle and a permissible number of discontinuation, at this timing.

Next, at the time of the calculation process of the EPS-ECU 21, there is a delay time (due to a difference between a reception timing from the LKA-ECU 10 and the process cycle, illustrated in Fig. 6, for example). Thus, there is a delay of time T4, which reflects these delay factors, at this timing .

In this case, the predetermined threshold

Th' 3 may correspond to a sum of the respective times (=T1 + T2 + T3 + T4) . With this arrangement, it becomes possible to appropriately reduce the problem that the diagnostic information is registered by the process of step 510 even though there is no abnormality in the LKA-ECU 10.

All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment ( s ) of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention. Further, all or part of the components of the embodiments described above can be combined.

For example, in the embodiments described above, the intervention control is implemented by using only the steering actuator 26; however, the intervention control may be implemented by using the brake actuator, instead of or in addition to the steering actuator 26. The unsuited circumstance for the intervention control with the brake actuator is substantially the same as the unsuited circumstance for the intervention control with the steering actuator 26. Thus, the unsuited circumstance determination process for a configuration in which intervention control with the brake actuator is performed alone or in combination may be the same as described above.

Further, in the embodiments described above, the presence or absence of the steering operation of the driver is determined using the driver steering torque; however, the presence or absence of the steering operation of the driver may be determined using other sensors (touch sensors provided on the steering wheel, an image sensor that captures a drive operations of the driver, for example) .

Further, in the embodiments described above, a lane detecting part is implemented by the forward camera 32 and the LKA-ECU 10; however, a lane may be detected by another apparatus such as a magnetic sensor, etc., if special infrastructural facilities are provided, for example.

Further, in the embodiments described above, the lane keeping assist control is restricted such that it is stopped when the unsuited circumstance is detected; however, the lane keeping assist control may be restricted in other manners. For example, when the unsuited circumstance is detected, a control target value of the intervention control may be reduced with respect to the same situation except for the fact that the unsuited circumstance is not detected. It is noted that the control target value may be the target lateral acceleration Gx, the target steering torque ST, etc., in the case of the example illustrated in Fig. 2, for example.

Further, in the embodiments described above, the abnormality time is considered; however, as an equivalent embodiment, the number of determinations may be considered. For example, in the example illustrated in Fig. 3, it may be determined in step 306 whether the number of the determination cycles (i.e., the number of the determinations) in which the determination results of step 300 and step 302 are simultaneously affirmative is greater than or equal to a predetermined threshold. The number of the determination cycles substantially represents the length of time, and thus considering the number of the determination cycles is equivalent to considering the abnormality time.

The present application is based on Japanese Priority Application No. 2013-150981, filed on July 19, 2013, the entire contents of which are hereby incorporated by reference.

Claims

Claim 1. A lane keeping assist apparatus, comprising :

a lane detecting part that detects a lane in which a vehicle travels;

Claim 2. The lane keeping assist apparatus of claim 1, wherein the steering operation of the driver is detected based on a driver steering torque detected by a torque sensor.

Claim 3. The lane keeping assist apparatus of claim 2, wherein the controller restricts, under the situation where the actuator is operated by the lane keeping assist control, the lane keeping assist control when the driver steering torque is less than or equal to a predetermined torque and a status in which the steering angle speed is greater than or equal to the predetermined speed continues for more than or equal to a predetermined time.

Claim 4. The lane keeping assist apparatus of claim 1, wherein the controller includes a first controller that outputs an operation demand for the actuator and a second controller that operates the actuator in response to the operation demand for the actuator,

the second controller invalidates, under a situation where the second controller receives the operation demand for the actuator from the first controller, the operation demand for the actuator from the first controller and determines that the first controller is in an abnormal state, when a predetermined second condition is met,

the first controller stops, under a situation where the first controller outputs the operation demand for the actuator to the second controller, the operation demand for the actuator when a predetermined first condition, which is more easily met than the second condition, is met.

Claim 5. The lane keeping assist apparatus of claim 4, wherein the predetermined first condition is met when the driver steering torque is less than or equal to a first predetermined torque and a status in which the steering angle speed is greater than or equal to a first predetermined speed continues for longer than or equal to a first predetermined time,

the predetermined second condition is met when the driver steering torque is less than or equal to a second predetermined torque and a status in which the steering angle speed is greater than or equal to a second predetermined speed continues for longer than or equal to a second predetermined time, and

the second predetermined torque is less than the first predetermined torque, the second predetermined speed is greater than the first predetermined speed, or the second predetermined time is longer than the first predetermined time.