JP2019051894A - Travel control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a traveling control device for a vehicle capable of preventing lane deviation due to excessive steering override in a process of shifting to LKA degeneracy control when an ACC function is lost. SOLUTION: When there is no other vehicle in front in the own vehicle traveling lane, the vehicle travels at a constant speed according to the target vehicle speed, and when there is another vehicle in front, the ACC function performs follow-up driving while maintaining a predetermined distance between vehicles, and the target route. The LKA function that maintains driving in the vehicle's driving lane by follow-up control, the steering override function that stops the LKA function by the driver's steering intervention, and the driver that stops and takes over the LKA function when the ACC function fails. In the driving control device of the vehicle having the function of controlling the contraction of the LKA function, the steering torque or steering angle override threshold value (T1d), which is a criterion for steering intervention to stop the LKA function when the ACC function is lost, is used. , T2d) has a function of changing to a value (T1e, T2e) larger than that during normal operation of the ACC function. [Selection diagram] FIG. 7

Description

  The present invention relates to a vehicle travel control device, and more particularly to a steering override function in a partially automatic traveling system in a lane.

  Various technologies aimed at reducing the burden on the driver and assisting safe driving, for example, an inter-vehicle distance control system (AdaptiveCruiseControlSystem: ACCS), a lane keeping assist system (LaneKeepingAssistanceSystem: LKAS), and the like have been put into practical use. Furthermore, the “Partially Automated In-lane Driving System (PADS)” based on these is being put to practical use and international standardization.

  Such a travel control system has an override function for switching to manual operation by the driver's forced intervention during operation. For example, Patent Document 1 includes control gain setting means for variably setting a control gain when performing steering control based on the steering target control amount, and the value of the control gain when the driver intervenes in the driving operation is determined as non-driving operation. A travel control device is disclosed in which the value is set smaller than the value at the time of intervention, and the value of the control gain at the time of own vehicle turning at the time of driving operation intervention is set to be larger than the value at the time of non-turning of the own vehicle. .

JP, 2006-97827, A

  By the way, as shown in FIG. 4, when a function failure occurs in the ACC system due to a failure or abnormality of the device during the PADS operation (61), the ACC function is stopped at the same time as the failure occurs. The driver is notified of a steering takeover request for stopping the LKA function (62), and is set to shift to the LKA degeneration control mode. After several seconds from the notification, the LKA degeneration control is started (63), the LKA degeneration control is terminated, and the steering is handed over to the driver (64).

  In such a system, for example, if a malfunction occurs in the ACC system during automatic steering on either the left or right side to follow the route to the lane center 51c by the LKA function, the LKA function is stopped before the LKA function is stopped. Since the degeneracy control mode is entered, there is a risk that excessive forward steering may be performed if the driver applies correction steering such as turning the steering wheel during LKA degeneration control.

  Furthermore, there is a possibility that the driver who has been informed of the function stop / takeover request notification performs excessive steering (steering override). In addition, there is a possibility of repeating excessive steering override and correction steering for steering.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vehicle travel control device that can prevent excessive steering override in the transition process to LKA degeneration control when the ACC function is lost. There is to do.

In order to solve the above problems, the present invention provides:
An environmental state estimation unit including a surrounding recognition function for recognizing the own vehicle traveling lane and other vehicles traveling in the traveling lane, and a function for acquiring the own vehicle motion state;
A route generation unit that generates a target route based on information acquired by the environmental state estimation unit;
A vehicle control unit that performs speed control and steering control so that the vehicle follows the target route;
A vehicle travel control device comprising:
An ACC function that performs constant speed traveling according to the target vehicle speed when there is no preceding other vehicle in the own vehicle traveling lane, and performs follow-up traveling while maintaining a predetermined inter-vehicle distance when there is a preceding other vehicle;
An LKA function for maintaining driving in the vehicle lane by following control to the target route;
A steering override function for stopping the LKA function by a driver's steering intervention;
A function of notifying the driver of the stop of the LKA function and the handover of the steering when the ACC function fails, and performing a degeneration control of the LKA function;
In what has
A function of changing an override threshold value of a steering torque or a steering angle, which is a determination criterion of the steering intervention for stopping the LKA function when the ACC function fails, to a value larger than that during normal operation of the ACC function; It is characterized by.

  According to the vehicle travel control apparatus of the present invention, while the function stop and the steering takeover are notified when the ACC function is lost and the LKA function degeneration control is performed, the steering override threshold is changed to a value larger than that during normal operation. Therefore, it is possible to prevent the driver from over-steering, and to avoid lane departure and repeated correction steering due to the over-steering, which is advantageous for smooth steering handover.

It is the schematic which shows the traveling control system of a vehicle. It is a schematic top view which shows the external field sensor group of a vehicle. It is a block diagram which shows the traveling control system of a vehicle. It is a schematic plan view which shows LKA degeneracy control at the time of ACC function failure. It is a schematic plan view which shows the example of the over steering prevention control at the time of ACC function failure. It is a schematic plan view which shows the other example of the over steering prevention control at the time of ACC function failure. It is a flowchart which shows the over steering prevention control at the time of ACC function failure.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In FIG. 1, a vehicle 1 equipped with a travel control system according to the present invention performs recognition, determination, and operation on the vehicle side in addition to conventional automobile components such as an engine and a vehicle body. In addition, an external sensor 21 for detecting the surrounding environment of the vehicle, an internal sensor 22 for detecting vehicle information, a controller / actuator group for speed control and steering control, an ACC controller 14 for inter-vehicle distance control, and a lane keeping support control And an automatic operation controller 10 that controls the LKA controller 15 and performs path following control.

  The controller / actuator group for speed control and steering control includes an EPS (electric power steering) controller 31 for steering control, an engine controller 32 for acceleration / deceleration control, and an ESP / ABS controller 33. ESP (registered trademark; Electronic Stability Program) constitutes a stability control system (vehicle behavior stabilization control system) including ABS (anti-lock brake system).

  The external sensor 21 uses the dividing lines 5s and 5c on the road that demarcate the own lane 51 and the adjacent lane 52, the presence and relative distance of other vehicles, obstacles, and people around the own vehicle as image data and point cloud data. It consists of a plurality of detection means for inputting to the automatic operation controller 10.

  For example, as shown in FIG. 2, the vehicle 1 includes a millimeter wave radar (211) and a camera (212) as the front detection means 211 and 212, and a LIDAR (laser image detection as the front side detection means 213 and the rear side detection means 214. / Ranging), equipped with a camera (back camera) as the rear detection means 215, covering 360 degrees around the own vehicle, the position and distance of vehicles and obstacles, etc. within a predetermined distance in the longitudinal direction of the own vehicle, and the position of the marking line Can be detected.

  The internal sensor 22 is composed of a plurality of detection means for measuring a physical quantity representing the motion state of the vehicle, such as a vehicle speed sensor, a yaw rate sensor, and an acceleration sensor. As shown in FIG. , ACC controller 14, LKA controller 15, and EPS controller 31.

  The automatic operation controller 10 includes an environmental state estimation unit 11, a route generation unit 12, and a vehicle control unit 13, and is a computer for performing functions as described below, that is, a ROM storing programs and data. , A CPU that performs arithmetic processing, a RAM that reads the program and data, stores dynamic data and arithmetic processing results, and an input / output interface.

  The environmental state estimation unit 11 acquires the absolute position of the host vehicle using the positioning unit 24 such as GPS, and the host vehicle lane 51 and the adjacent vehicle are adjacent to each other based on the external data such as image data and point cloud data acquired by the external sensor 21. The lane line 52, the other vehicle position, and the speed are estimated. Further, the movement state of the host vehicle is acquired from the inner world data measured by the inner world sensor 22.

  The route generation unit 12 generates a target route from the vehicle position estimated by the environmental state estimation unit 11 to the arrival target. Further, with reference to the map information 23, the target destination point from the own vehicle position in the lane change is determined based on the lane marking position, the other vehicle position and speed of the adjacent lane estimated by the environmental state estimation unit 11, and the movement state of the own vehicle. Generate a target route to

  The vehicle control unit 13 calculates a target vehicle speed and a target rudder angle based on the target route generated by the route generation unit 12, and transmits a speed command for constant speed traveling or inter-vehicle distance maintenance / following traveling to the ACC controller 14. Then, a steering angle command for path following is transmitted to the EPS controller 31 via the LKA controller 15.

  The vehicle speed is also input to the EPS controller 31 and the ACC controller 14. Since the steering torque changes depending on the vehicle speed, the EPS controller 31 transmits a torque command to the steering mechanism 41 with reference to the steering angle-steering torque map for each vehicle speed. By controlling the engine 42, the brake 43, and the steering mechanism 41 by the engine controller 32, the ESP / ABS controller 33, and the EPS controller 31, the longitudinal and lateral movements of the vehicle 1 are controlled.

(Outline of partially automated driving system in the lane)
Next, an outline of the in-lane partially automated driving system (PADS) will be described on the assumption that the vehicle travels in a single lane while following the preceding vehicle on the highway.

  The partially automatic traveling in the lane (PADS traveling) can be executed in a state where the ACC controller 14 constituting the ACCS and the LKA controller 15 constituting the LKAS are operated together with the automatic operation controller 10.

  Simultaneously with the operation of the partially automatic driving system in the lane, the automatic driving controller 10 (route generation unit 12) obtains external environment information (lane, own vehicle position, own vehicle driving lane and A single lane target route and a target vehicle speed are generated on the basis of the other vehicle position and speed traveling in the adjacent lane and the inner world information (vehicle speed, yaw rate, acceleration) acquired by the inner sensor 22.

The automatic operation controller 10 (vehicle control unit 13) determines the vehicle position and vehicle motion characteristics, that is, the front wheel steering angle δ generated when the steering torque T is applied to the steering mechanism 41 during traveling at the vehicle speed V. From the relationship between the yaw rate γ generated by the motion and the lateral acceleration (d ² y / dt ² ), the vehicle speed, posture, and lateral displacement are estimated after Δt seconds, and the steering angle command is such that the lateral displacement becomes yt after Δt seconds. Is sent to the EPS controller 31 via the LKA controller 15 and a speed command to give the speed Vt after Δt seconds is given to the ACC controller 14.

  During partial automatic traveling in the lane, the external sensor 21 recognizes the preceding vehicle ahead of the own lane and the lane division line of the own lane, and constantly monitors so that the own vehicle follows the generated target route.

(Relationship with ACC, EPS, ESP / ABS, LKA, engine control)
Although the ACC controller 14, the LKA controller 15, the EPS controller 31, the engine controller 32, and the ESP / ABS controller 33 operate independently of automatic steering, the operation of the partially automatic driving function (PADS) in the lane is performed. During operation, operation is possible even by command input from the automatic operation controller 10.

  The ESP / ABS controller 33 that has received the deceleration command from the ACC controller 14 issues a hydraulic pressure command to the actuator and controls the braking force of the brake 43 to control the vehicle speed. Further, the engine controller 32 that receives the acceleration / deceleration command from the ACC controller 14 controls the actuator output (throttle opening), thereby giving a torque command to the engine 42 and controlling the driving force to control the vehicle speed. .

  The ACC function (ACCS) functions by a combination of hardware and software such as the millimeter wave radar 211 as the external sensor 21, the ACC controller 14, the engine controller 32, and the ESP / ABS controller 33.

  In other words, when there is no preceding vehicle, the vehicle runs at a constant speed with the cruise control set speed as the target vehicle speed, and when it catches up with the preceding vehicle (when the preceding vehicle speed is lower than the cruise control set speed), it matches the preceding vehicle speed. The vehicle follows the preceding vehicle while maintaining the inter-vehicle distance corresponding to the set time gap (inter-vehicle time = inter-vehicle distance / own vehicle speed).

  The LKA function (LKAS) detects the lane line and the vehicle position by the environmental state estimation unit 11 of the automatic operation controller 10 based on the image data acquired by the external sensor 21 (cameras 212 and 215), and detects the center of the lane. Steering control is performed by the LKA controller 15 and the EPS controller 31 so that the vehicle can travel.

  That is, the EPS controller 31 that has received the steering angle command from the LKA controller 15 refers to the vehicle speed-steering angle-steering torque map and issues a torque command to the actuator (EPS motor), and the steering mechanism 41 is the target. Gives the front wheel rudder angle.

  In the lane partially automatic driving function (PADS), the longitudinal control (speed control, inter-vehicle distance control) by the ACC controller 14 and the lateral control (steering control, lane keeping traveling control) by the LKA controller 15 are performed as described above. Implemented by combining.

(Override function)
The driver can override either the longitudinal control system (ACCS) or the lateral control system (LKAS) during operation of the partially automatic driving function (PADS) in the lane.

  The vertical control system (ACCS) is overridden when the engine torque request by the driver's accelerator pedal operation or the deceleration request by the brake pedal operation is greater than or equal to the respective override threshold. These override thresholds are set according to the acceleration / deceleration characteristics of the vehicle and the running state.

  The lateral direction control system (LKAS) is overridden when the steering torque of the driver's manual steering 34 is greater than or equal to the override threshold. The override threshold value due to the steering intervention is set according to the steering characteristics of the vehicle and the running state.

  Steering override is when the steering wheel is given steering torque that is judged to have been steered with the intention of changing the course or avoiding obstacles, or steering with the intention of contradicting LKA control (reverse steering). , LKA control is stopped, and the vehicle shifts to traveling by manual steering by the driver.

  By the way, as shown in FIG. 4, when an ACCS malfunction occurs due to a failure of the forward detection millimeter-wave radar or abnormal ESP / ABS during operation of the partially automatic driving function (PADS) in the lane ( 61) The ACC function is stopped simultaneously with the occurrence of the failure, the LKAS shifts to the degeneration control mode, and the driver is notified of the LKA function stop and the steering takeover request (takeover request) (62) for several seconds (for example, 4 After the second), LKA degeneration control is started (63), and when the steering torque becomes 0 (Nm), the LKA function is stopped and the driver takes over the steering (64).

  The LKA degeneration control is set for the purpose of smoothly shifting to manual steering by gradually decreasing the steering torque command value input to the EPS controller 31 to 0 (Nm) with a predetermined inclination.

  As described above, when a malfunction of the ACCS occurs during the operation of the partially automatic driving function in the lane, the ACC function and the LKA function are stopped, and the vertical direction control and the horizontal direction control are taken over by the driver. However, as described above, there is a risk of excessive steering (steering override) by the driver who has been informed of the function stop / handover request notification.

(Oversteering prevention function in case of ACCS function failure)
Therefore, in the automatic driving controller 10 according to the present invention, an ACCS function failure occurs during the operation of the partially automatic driving function in the lane, and the ACC function and the LKA function are stopped and the driver of the vertical control and the horizontal control is operated. When taking over the vehicle, from the partially automatic driving function stop in the lane (ACC function stop / LKA function stop notification) to the LKA function stop (for example, 4 seconds after notification-LKA degeneration control start-LKA degeneration control end) Is provided with an oversteering prevention function for changing the steering override threshold to a value larger than that during normal operation.

  When the ACCS malfunctions, the steering override threshold value is made larger than that during normal operation, so that even if an excessive steering torque is input to the EPS controller 31 by the driver's manual steering 34, the override state is not achieved and the LKA control is performed. Is continued, and the vehicle can travel while maintaining the lane.

(Steering override threshold during normal operation)
The steering override threshold value during normal operation of the ACCS is based on the vehicle speed V, the lateral acceleration limit value (for example, 1 m / s ² ), and the lateral movement distance yt for reaching the lane center position (1a) from the current position after t seconds. The value obtained by converting the steering angle calculated from the virtual lateral displacement y′t (= yt + α) and the vehicle motion characteristic into the steering torque (the vehicle speed−the steering angle−the steering torque calculated from the steering torque map) is set as the override threshold T1d. Is done.

  Specifically, it corresponds to a steering angle at which the virtual lateral displacement y′t for reaching the virtual lateral position (1d) after t seconds becomes yt + α (where α is a constant determined based on the vehicle speed). The steering torque is set to the forward steering override threshold T1d.

  In the case of reverse steering, with respect to a value (steering torque target value) obtained by converting the steering angle calculated from the target lateral movement distance yt to reach the target position (1a) after t seconds and the kinematic characteristics of the vehicle into the steering torque. Thus, the value is set to a value T2d that is applied in the direction of decreasing the steering torque and that can be determined as not being minute (determined by the steering angle, the steering angular velocity, etc.). Since reverse steering can be regarded as a driver's intention to cancel LKA control, it is overridden when detected as reverse steering.

  For example, it is assumed that a vehicle having a vehicle width of 1.7 m is traveling on an LKAS on a highway having a lane width of 3.5 m. As shown in FIG. 5, if the vehicle 1 is running near the right end of the lane 51 (a little extreme for easy understanding), the center G in the lateral direction of the vehicle is the right lane section. The LKAS is located near 0.9m from the line 5c, and the left automatic steering sets the position near the lane center 51c, that is, near 1.75m from the right lane marking line 5c. Therefore, the lateral displacement after t seconds is 1.75- Steering torque corresponding to the steering angle at which 0.9 = 0.85 m and α = 0.43 m and the lateral displacement after t seconds is 1.28 m (0.85 + 0.43) is normal steering during normal operation It is set as the override threshold T1d.

  On the other hand, the reverse steering override threshold T2d is set in accordance with the vehicle speed of the sensing steering torque X′Nm (X ′ <X) applied in the direction of decreasing the steering torque XNm. Therefore, the virtual lateral displacement as in the case of forward steering does not appear in FIG.

(Steering override threshold in case of malfunction)
A value obtained by adding a steering torque (vehicle speed-steering angle-steering torque map and vehicle motion characteristics to the forward steering override threshold T1d during normal operation of the ACCS) such that the lateral movement distance by the driver's additional steering becomes a predetermined value or more. Set in consideration). If the steering torque is such that the lateral movement distance by the driver's follow-up steering is less than a predetermined value, it is not overridden.

Specifically, based on the vehicle speed V, the lateral acceleration limit value (for example, 1 m / s ² ), and the lateral movement distance yt to reach the lane center position (1a) from the current position, the virtual lateral position ( 1e ₁ ) is a virtual lateral displacement y ″ ₁ t (= yt + β, where β> α, β = 2α in the illustrated example) and a steering angle calculated from the vehicle motion characteristics is converted into a steering torque. It is set as the forward steering override threshold T1e.

  For example, a case where a vehicle having a vehicle width of 1.7 m is traveling on an LKAS on a highway having a lane width of 3.5 m is assumed as described above. As shown in FIG. 5, if the vehicle 1 is traveling near the right end of the lane, the lateral movement distance yt for reaching the center position (1a) of the lane 51 from the current position after t seconds is 1.75. -0.9 = 0.85m, but at the time of malfunction, β = 0.85m and the steering angle is such that the virtual lateral displacement after t seconds is 1.75m (= 0.9 + 0.85). The corresponding steering torque is set as the forward steering override threshold T1e. Even if the actual lateral displacement is set to 1.75 m, it is possible to maintain traveling in the lane.

On the other hand, the reverse steering override threshold T2e approximates the virtual lateral displacement corresponding to the reverse steering override threshold T2d during normal operation to the lateral movement distance yt to reach the lane center position (1a) from the current position. Based on this, the virtual lateral displacement for reaching the virtual lateral position (1e ₂ ) after t seconds is y ″ ₂ t (= yt−γ, where γ is larger than the lateral displacement corresponding to the steering torque X′Nm. In the example shown, γ = α) and a value obtained by converting the steering angle calculated from the motion characteristics of the vehicle into the steering torque is set as the reverse steering override threshold T2e.

In this case, as shown in FIG. 5, the steering torque corresponding to the steering angle is such that γ = 0.43 m and the lateral displacement after t seconds is 0.42 m (= 0.85−0.43). The reverse steering override threshold T2e is set. As is clear from FIG. 5, traveling in the lane can be maintained even in the virtual lateral position (1e ₂ ).

(Other setting examples of steering override threshold in case of functional failure)
FIG. 6 shows another setting example of the steering override threshold when the ACCS function is lost. In this example, the vehicle 1 having a vehicle width of 1.7 m travels LKAS around the center of the highway having a lane width of 3.5 m. It is assumed that you are.

First, when the vehicle 1 is traveling 0.5 m to the right in the traveling direction from the lane center 51c, the lateral movement distance yt (= 0.5m) for reaching the lane center 51c from the current position after t seconds, t Assuming that the virtual lateral displacement y ″ ₁ t = yt + β is assumed to reach the allowable lateral position 1e ₁ that does not deviate from the left lane marking 5s from the current position in seconds, β = 3.5 / 2−1.7. Since /2=0.9 m, y ″ ₁ t = 1.4 m.

In this case, for example, the steering override threshold value Td1 during normal operation of the ACCS is ½ of the virtual lateral displacement that reaches the allowable lateral position 1e ₁ after t seconds, that is, y ′ ₁ t = (yt + β) / 2 = 0. The steering torque is set to 7 m, and the steering override threshold Te1 when the ACCS function is lost becomes the virtual lateral displacement y ″ ₁ t = yt + β = 1.4 m corresponding to the allowable lateral position 1e ₁ after t seconds. Such a steering torque is set.

The same applies to the case of reverse steering, and the virtual lateral displacement y ″ ₂ t = yt−β when it is assumed that the allowable lateral position 1e ₂ that does not deviate from the right lane marking 5c from the current position is reached after t seconds. Then, since β = 3.5 / 2−1.7 / 2 = 0.9 m, y ″ ₂ t = −0.4 m. In this case, the steering override threshold Td2 in the normal operation of the ACCS is t seconds. The steering torque is set such that ½ of the virtual lateral displacement that later reaches the allowable lateral position 1e ₂ , that is, y ′ ₂ t = (yt−β) /2=−0.2 m, and the ACCS function is lost. The steering override threshold Te2 at the time is set to a steering torque such that a virtual lateral displacement y ″ ₂ t = yt−β = −0.4 m corresponding to the allowable lateral position 1e ₂ after t seconds.

In this setting example, the vehicle 1 is steered so that the virtual lateral displacement y ″ ₁ t, y ″ ₂ t reaches the allowable lateral position 1e ₁ , 1e ₂ that does not deviate from the left and right lane markings 5s, 5c after t seconds. Since the steering override threshold values T1e and T2e when the ACCS function is lost are set based on the torque, it is possible to prevent oversteering while maintaining in-lane travel.

(Flow in case of ACCS malfunction)
Next, the flow at the time of ACCS function failure will be described with reference to FIG.

(1) Travel by partially automated driving system in the lane (PADS driving)
When PADS running is selected by the driver's operation, ACCS and LKAS are activated through a system check, and the fact that the PADS is running is displayed in the instrument panel or the like (step 100). In PADS traveling, ACCS and LKAS are linked to each other and maintain a single lane at the target speed (cruise set speed) or travel at a constant speed or follow a predetermined distance. In this case, the in-lane target route is set by a predetermined offset distance from the center of the lane (travel lane) or the left or right lane line.

(2) Determination of ACCS function failure During the PADS (ACCS / LKAS) traveling, the external sensor 21, the inner sensor 22, and the components including the actuator group are constantly monitored for failures and abnormalities to determine ACC function failure. Is performed (step 101).

(3) ACC function stop While running PADS (ACCS / LKAS), the components of the ACCS such as disconnection of the forward detection millimeter-wave radar 211 constituting the external sensor 21 and failure of the hydraulic system of the ESP / ABS controller 33 If a function failure is detected, the immediate ACC function is stopped (step 102) and an ACC function failure flag is set (step 103).

(4) Change of steering override threshold At the same time, the steering override threshold is changed from a steering override threshold during normal operation (forward direction T1d, reverse direction T2d) to a steering override threshold (forward direction T1e, reverse direction T2e) at the time of malfunction. It is changed (step 113). That is, a value obtained by converting the steering angle calculated from the lateral movement distance yt and the vehicle motion characteristic at this time into the steering torque is calculated, and the steering override threshold (forward direction T1e, reverse direction T2e) at the time of malfunction is set. Is done.

(5) Notification of ACC function failure / steering takeover At the same time, the occurrence of ACC function failure and steering takeover (LKAS is stopped via degeneration control) by the display and sound in the head-up display and the meter panel. (Step 104). At the same time, counting of a predetermined time (for example, 4 seconds) until the shift to the LKA degeneration control is started.

(6) Manual steering presence / absence determination At the same time, the presence / absence of manual steering 34 is determined by the torque sensor attached to the EPS controller 31 (step 105).

(7) Steering direction determination When it is determined that manual steering is present from the detected value of the torque sensor attached to the EPS controller 31, the steering direction of the manual steering 34 is determined (step 106).

  The determination of the steering direction is determined as forward steering when applied to the steering torque value calculated at step 113 in the direction of increasing the steering torque, and when applied in the direction of decreasing the steering torque. The reverse steering is determined.

(8) Override determination It is determined whether the steering torque of the manual steering 34 exceeds the override threshold.
(8-1) Forward Steering Override Determination When the steering direction is determined to be forward steering, the steering torque is compared with the forward steering override threshold T1e (step 107).
i) If the steering torque is greater than the forward steering override threshold value T1e, it is determined that the vehicle is overridden.
ii) If the steering torque is less than the forward steering override threshold T1e, the LKA travel is continued without overriding.

(8-2) Reverse Steering Override Determination When it is determined that the steering direction is reverse steering, the steering torque is compared with the reverse steering override threshold T2e (step 108).
i) If steering torque> reverse steering override threshold T2e, it is determined that the vehicle is overridden.
ii) If steering torque <reverse steering override threshold T2e, the LKA travel is continued without overriding.

(9) Judgment of Passing Elapsed Time When the LKA travel is continued, the counting of the predetermined time (4 seconds) after issuing the steering handing over notification in Step 104 is continued (Step 109), and the predetermined time (4 seconds) ) Starts LKAS degeneration control (step 110).

(10) LKAS degeneration control end / function stop / steering takeover When LKAS degeneration control for gradually decreasing the steering torque command value input to the EPS controller 31 to 0 (Nm) with a predetermined inclination is completed, the LKA function is stopped. Then, the steering is handed over to the driver (step 111), and a complete transition is made to manual steering (step 112).

  The override threshold change as described above can basically prevent over-steering when the ACC function is lost. However, in the above-described override determination (steps 107 and 108), if manual steering is greater than or equal to the override threshold, The LKA function will be overridden by manual steering.

  Therefore, when the override threshold is changed when the ACC function is lost (step 103), the steering torque or steering angle is set in the EPS controller 31 according to the vehicle speed (inversely proportional to the vehicle speed / decreasing as the vehicle speed increases). By making the upper limit value of the value lower than that during normal operation, it is possible to maintain in-lane travel even when overridden by manual steering.

  In addition, when the override threshold is changed when the ACC function is lost (step 103), the EPS controller 31 changes the steering gain of the manual steering to a small value so that the steering is overridden even if the steering is overridden by manual steering. The amount may be partially reflected in the steering torque.

(Action and effect)
As described above in detail, the vehicle travel control device according to the present invention is notified of the stop of the ACC function and the LKA function and the takeover of the vertical direction control and the horizontal direction control to the driver when the ACCS function is lost. Since the steering override threshold is changed to a value larger than that during normal operation while the degeneration control is performed, an excessive steering torque that leads to lane departure is given by the driver's steering operation. In such a case, the vehicle is not overridden and the LKA control is continued, so that traveling in the lane is maintained and overriding due to oversteering and lane departure due to the oversteering can be prevented.

  For example, even if a malfunction occurs in the ACCS during partial automatic driving function in the lane, and the driver applies corrective steering such as turning the steering wheel during LKA degeneration control, the steering override threshold is set to be large. Therefore, lane departure can be prevented without overriding. Furthermore, since steering override is not performed, it is possible to prevent repeated correction steering with respect to steering.

  Further, the steering override threshold applied when nine functions fail in the ACCS is maintained from the notification of function stop and steering takeover to the end of the LKA degeneration control, so that the steering assist by the LKA function is partially acting. Since it is possible to gradually take over the steering in the state, it is advantageous for smooth steering taking over.

  In addition, the steering override threshold value when the ACC function is normal differs depending on whether the steering direction is forward steering or reverse steering with respect to the steering direction at the time of steering intervention. However, there is a difference between the case of forward steering and the case of reverse steering with respect to the steering direction at the time of steering intervention, so that it is possible to effectively prevent oversteering according to the running state of the vehicle when the ACC function is lost. There is.

  In LKAS, the vehicle is steered so that it travels in the center of the travel lane. Therefore, in the case of forward steering with respect to the steering direction at the time of steering intervention, there is a lot of excess space in the lateral movement direction of the vehicle. In the case of steering, since there is relatively little surplus space, an over-threshold can be effectively prevented by applying an override threshold that prioritizes traveling in the lane.

  The override threshold at the time of ACC function failure is set in the range of 50% to 100%, preferably 90% to 100% of the maximum lateral displacement not deviating from the driving lane. It is set in a range smaller than the override threshold at the time of function failure, for example, 50% or less, preferably in a range of 40% to 50%. In particular, the override threshold in the case of reverse steering with a relatively small surplus space described above is preferably set based on the maximum lateral displacement that does not deviate from the traveling lane.

  In the embodiment described above, the steering override threshold is set based on the steering torque. However, the steering override threshold may be set based on the steering angle (steering angle).

  Although several embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical idea of the present invention. I will add.

1 Vehicle (own vehicle)
5, 5c, 5d, 5s Dividing line 10 Automatic operation controller 11 Environmental state estimation unit 12 Path generation unit 13 Vehicle control unit 14 ACC controller 15 LKA controller 21 External sensor 22 Internal sensor 31 EPS controller 32 Engine controller 33 ESP / ABS controller 34 Manual steering (handle)
41 Steering mechanism 42 Engine 43 Brake 51, 52 Lane

Claims (5)

An environmental state estimation unit including a surrounding recognition function for recognizing the own vehicle traveling lane and other vehicles traveling in the traveling lane, and a function for acquiring the own vehicle motion state;
A route generation unit that generates a target route based on information acquired by the environmental state estimation unit;
A vehicle control unit that performs speed control and steering control so that the vehicle follows the target route;
A vehicle travel control device comprising:
An ACC function that performs constant speed traveling according to the target vehicle speed when there is no preceding other vehicle in the own vehicle traveling lane, and performs follow-up traveling while maintaining a predetermined inter-vehicle distance when there is a preceding other vehicle;
An LKA function for maintaining driving in the vehicle lane by following control to the target route;
A steering override function for stopping the LKA function by a driver's steering intervention;
A function of notifying the driver of the stop of the LKA function and the handover of the steering when the ACC function fails, and performing a degeneration control of the LKA function;
In what has
A function of changing an override threshold value of a steering torque or a steering angle, which is a determination criterion of the steering intervention for stopping the LKA function when the ACC function fails, to a value larger than that during normal operation of the ACC function; A vehicle travel control apparatus characterized by the above.   2. The vehicle travel control apparatus according to claim 1, wherein the override threshold at the time of failure of the ACC function is maintained from the stop of the LKA function and the notification of steering takeover to the end of the degeneration control.   The override threshold when the ACC function is normal differs depending on whether the steering is forward steering or reverse steering with respect to the steering direction at the time of the steering intervention, and the override threshold is changed when the ACC function is lost. 3. The vehicle travel control apparatus according to claim 1, wherein the vehicle travel control apparatus is different between a case where forward steering is performed and a case where reverse steering is performed with respect to a steering direction at the time of the steering intervention.   The override threshold at the time of the ACC function failure is set in a range of 50% to 100% of the maximum lateral displacement that does not deviate from the driving lane, and the override threshold at the time of the normal ACC function is the above-described override threshold at the time of the ACC function failure. The travel control device for a vehicle according to any one of claims 1 to 3, wherein the travel control device is set in a range smaller than the override threshold.   5. The apparatus according to claim 1, further comprising a function of lowering an upper limit value of a steering torque or a steering angle that is set according to a vehicle speed when the override threshold is changed when the ACC function is lost. Vehicle travel control device.

Images