JP4696720B2 - Automatic steering control device - Google Patents

Description

  The present invention relates to an automatic steering control device that performs automatic steering so that a host vehicle travels along a reference route.

2. Description of the Related Art Conventionally, as an automatic steering control device, a device has been proposed in which a vehicle position is measured by GPS positioning and automatic steering control is performed based on the positioning result. Also, when GPS positioning becomes impossible, such as when radio waves from GPS satellites can no longer be acquired, the driver is notified that GPS positioning is not possible and stops, and the driver is automatically Proposals have been made to request switching from steering to manual steering, or to automatically switch to manual steering when GPS positioning is disabled (see, for example, Patent Document 1).
JP 2003-256038 A

  As described above, in the automatic steering control device that switches from automatic steering to manual steering when GPS positioning is disabled, the driver travels along the reference route when GPS positioning is disabled. It is necessary to start manual steering promptly from the state where automatic steering is being performed. Here, the more the automatic steering control is performed so as to reduce the travel error when traveling along the reference route, the more the position control is emphasized, the more difficult the steering intervention by the driver is. Become. For this reason, when switching from automatic steering to manual steering in a state where the driver is difficult to perform steering intervention in this way, the steering torque due to automatic steering is applied and the driver is difficult to perform steering intervention. Especially when there is a large correction rudder amount due to automatic steering, etc., and the driver needs to perform a steering operation to travel along the reference route. However, there is a problem that the driver feels uncomfortable when switching from automatic steering to manual steering, and the steering load of the driver after switching to manual steering increases.

  In addition, since automatic steering is switched to manual steering when GPS positioning is disabled, automatic steering and manual steering are switched every time GPS positioning is disabled, and GPS positioning is disabled. If this situation occurs frequently, switching between automatic steering and manual steering also frequently occurs, which may give the driver a feeling of annoyance.

  To avoid this, when GPS positioning becomes impossible, the current position of the vehicle is estimated by dead reckoning based on detection signals such as vehicle speed, yaw rate, and lateral acceleration detected by the autonomous sensor. Based on this, on the premise that automatic steering is continued, a method of delaying the timing for canceling automatic steering has been proposed. However, if GPS positioning does not return, automatic detection by dead reckoning is proposed. Since automatic steering is canceled when steering becomes impossible, the load on the driver at the time of switching to manual steering also increases in this case, especially when GPS positioning becomes impossible. If the section in which automatic steering is performed by reckoning is a curved road, the driver immediately starts steering intervention when automatic steering is released and runs on the curved road. It is necessary to perform a steering order to perform, there is a problem that the driver of the burden is large at the time switched to manual steering.

  Therefore, the present invention has been made paying attention to the above-mentioned conventional unsolved problems, and prevents the driver from feeling uncomfortable when switching from automatic steering to manual steering, and increases the load on the driver. It aims at providing the automatic steering control device which can be controlled.

In order to achieve the above object, the automatic steering control device according to the present invention is based on the vehicle position detected by the vehicle position detection unit when the vehicle position detection unit can detect the vehicle position. Thus, steering control is performed by fully automatic steering control means that prioritizes steering position control over disturbance input such as driver steering operation so that the host vehicle travels along the reference route. Then, when there is a lost section on the reference route ahead of the host vehicle in which it is difficult to detect the host vehicle position by the host vehicle position detecting means, the vehicle is detected at a preset timing before the host vehicle enters the lost section. Instead of the automatic steering control means, the semi-automatic steering control means for performing the steering control so that the host vehicle travels along the reference route while allowing the driver's steering intervention is operated.

According to the automatic steering control device of the present invention, the position control is prioritized by the fully automatic steering control means so that the own vehicle travels along the reference route based on the own vehicle position detected by the own vehicle position detection means. When the lost section is detected on the reference route ahead of the host vehicle while the steering control is being performed, the driver switches to the semi-automatic steering control means at a preset timing before the host vehicle enters the lost section. Steering control is performed so that the vehicle travels along the reference route while allowing the steering intervention of the vehicle, and automatic steering is performed with emphasis on cooperation between automatic steering and manual steering by the driver. Therefore, when switching to manual steering, the driver is already steering or ready to steering, so the driver switches from automatic steering to manual steering. By Rukoto, it is possible to shift to manual steering smoothly without having to remember or discomfort or feel the load.

Embodiments of the present invention will be described below.
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.
In FIG. 1, 1FL, 1FR, 1RL and 1RR are the left front wheel, the right front wheel, the left rear wheel and the right rear wheel, respectively. The rear wheels 1RL and 1RR are driven by the engine 2 with the automatic transmission 3 and the propeller shaft. 4, drive wheels that are transmitted through the final reduction gear 5 and the axle 6 in this order.

  The front wheels 1FL and 1FR are steering wheels connected to a steering wheel 9 via a steering gear 7 and a steering shaft 8, and a steering actuator 10 composed of an electric motor is connected to the steering shaft 8. . The steering actuator 10 is configured to control the steering direction, the steering angle, and the steering speed of the front wheels 1FL and 1FR according to a steering control amount Sδ output from a controller 20 described later.

Further, wheel speed sensors 11FL to 11RR that output wheel speeds Vfl to Vrr having a frequency corresponding to the rotational speed of the wheels are disposed on the wheels 1FL to 1RR, respectively. Further, the vehicle includes a longitudinal acceleration sensor 12 that detects longitudinal acceleration Xg, a lateral acceleration sensor 13 that detects lateral acceleration Yg, a yaw rate sensor 14 that detects yaw rate φ, and a steering angle sensor 15 that detects steering angle δ. And are provided.
The vehicle is also provided with a GPS 16 that receives satellite radio waves transmitted from an artificial satellite and detects the current vehicle position, and a storage medium such as a CD-ROM or DVD-ROM that stores road map information in a predetermined area. The storage unit 17 is mounted.

  The wheel speeds Vfl to Vrr detected by the wheel speed sensors 11FL to 11RR, the longitudinal acceleration Xg detected by the longitudinal acceleration sensor 12, the lateral acceleration Yg detected by the lateral acceleration sensor 13, and the yaw rate sensor 14 are detected. Controller including a microcomputer, for example, a yaw rate φ, a steering angle δ detected by the steering angle sensor 15, the own vehicle position information detected by the GPS 16, and the road map information stored in the storage unit 17 20 is input. The storage unit 17 also stores information on a section (hereinafter referred to as a lost section) in which it is difficult to detect the position of the host vehicle because the GPS satellite radio waves cannot be acquired through a tunnel or the like.

  The controller 20 sets the steering control amount Sδ for the steering actuator 10 described above by executing the automatic steering control process of FIG. 2 in a preset cycle, and the steering angle changes due to disturbance such as the steering operation of the driver. In order to avoid this, and perform fully automatic steering control giving priority to position control over driver steering operation so that the position of the vehicle by GPS positioning becomes the target position on the reference route, it is impossible to acquire GPS satellite radio waves. When the vehicle approaches the lost section, it switches from fully-automatic steering control to semi-automatic steering control at a timing according to the travel difficulty of the lost section, allowing steering intervention by the driver and allowing automatic steering and manual steering. Semi-automatic steering control that emphasizes the cooperation of The controller 20 starts this automatic steering control process when GPS positioning is possible, and thereafter executes it at a predetermined cycle.

  Specifically, in the automatic steering control process, first, in step S1, the road map information stored in the storage unit 17 is read in accordance with the vehicle position detected by the GPS 16, and the node data (X , Y), as shown in FIG. 3, a range (X0, Y0) to (Xn, Yn), which is a predetermined distance before and after the vehicle position (Xown, Yown), is always held in the buffer. Here, the distance on the front side is, for example, either a value obtained by multiplying the vehicle speed Vc by a predetermined time t1 (= Vc · t1), a multiplication value of the vehicle speed Vc and the predetermined time t1, or a preset specified value. Set to the larger one. Further, information indicating whether or not it is a lost section where GPS positioning is impossible (1 or 0) accompanying the node data (X, Y) read from the storage unit 17 is read. Further, after reading the wheel speeds Vfl to Vrr output from the various sensors, the longitudinal acceleration Xg, the lateral acceleration Yg, and the yaw rate φ, the process proceeds to step S2.

In step S2, the average value of the wheel speeds Vfl to Vrr read in step S1 is calculated, and this is set as the vehicle speed Vc.
Next, the process proceeds to step S3, and among the nodes read in step S1, the corresponding node (Xlost, Ylost) at the start point of the lost section where radio waves cannot be acquired from the GPS 16 is detected.

If there is no lost point in front of the host vehicle, the process proceeds from step S3a to step S9, which will be described later. If there is a lost section in front of the host vehicle, the process proceeds from step S3a to step S4. In this step S4, a distance D2lost between the lost start point and the current vehicle position (Xown, Yown) is calculated from the following equation (1).
D2lost = {(Xown-Xlost) ² + (Yown-Ylost) ² } ^1/2
...... (1)

  In addition, the infrastructure for notifying the lost start point is arranged on the traveling road side, and road-to-vehicle communication means for performing road-to-vehicle communication with the infrastructure is mounted on the host vehicle, and the road-to-vehicle communication means Road-to-vehicle communication may be performed between the infrastructure and the host vehicle, and information on a point where the lost start point and a GPS satellite can be acquired again from the infrastructure may be acquired. Similarly, inter-vehicle communication means for performing inter-vehicle communication with other vehicles is mounted on the host vehicle, and inter-vehicle communication is performed with other vehicles by the inter-vehicle communication means, and the lost start point and GPS satellite radio waves are acquired again. You may make it acquire the information of the point which becomes possible.

Next, in step S5, the travel difficulty Diff of the reference route of the host vehicle after GPS lost is calculated.
Specifically, first, the lost section distance Dlost is calculated. The lost section distance Dlost is the distance between sections where the acquisition of radio waves from the GPS satellites is impossible, the satellite acquisition impossible section distance Dgpslost, and the acquisition of the radio waves from the GPS satellites is restored and high-precision position measurement is resumed. It is calculated as the sum of the return section distance Drec until.

The satellite unacceptable section distance Dgpslost can be obtained again from the lost start point node (Xlost, Ylost) at which the acquisition of the radio wave from the GPS satellite detected in step S3 is impossible, and the radio wave from the GPS satellite. Based on the node (Xrec, Yrec) of the point to be calculated from the following equation (2).
Dgpslost = {(Xlost−Xrec) ² + (Ylost−Yrec) ² } ^1/2
(2)
The return section distance Drec is calculated from the following equation (3) based on the time Trec (for example, about 7 seconds) required for the return of position measurement and the vehicle speed Vc.
Drec = Trec × Vc (3)

Then, based on the following equation (4), the lost section distance Dlost is calculated based on the satellite acquisition impossible section distance Dgpslost and the return section distance Drec calculated by the expressions (2) and (3).
Dlost = Dgpslost + Drec (4)
Based on the lost section distance Dlost calculated in this way, the travel difficulty Diff is calculated. This travel difficulty Diff is an index indicating the likelihood of error in dead reckoning, and is based on, for example, lost section distance Dlost, lost section road curvature, lost section curvature change value, lost section road width, etc. To set.

  The travel difficulty Diff indicates that the greater the value is, the higher the difficulty is. For example, when setting based on the lost section distance Dlost, as shown in the characteristic diagram of FIG. The longer the distance Dlost, the higher the travel difficulty Diff. In FIG. 4A, the horizontal axis represents the lost section distance Dlost [m], and the vertical axis represents the travel difficulty Diff.

Further, when the travel difficulty Diff is set based on the road width of the lost section, for example, as shown in FIG. 4B, the travel difficulty Diff increases in inverse proportion to the road width. Set as follows. In FIG. 4B, the horizontal axis represents the road width [m], and the vertical axis represents the travel difficulty. The road width may be acquired from the road map information.
Further, when the travel difficulty Diff is set based on the road curvature of the lost section, as shown in the characteristic diagram of FIG. 4C, the travel difficulty Diff becomes higher as the road curvature is smaller, and The smaller the road curvature is, the larger the change in the travel difficulty Diff with respect to the change in the road curvature is set. In FIG. 4C, the horizontal axis represents the road curvature [m], and the vertical axis represents the travel difficulty Diff. Moreover, what is necessary is just to acquire the road curvature of a lost area from road map information.

  Further, when the travel difficulty Diff is set based on the road curvature change value of the lost section, the road curvature change value can be regarded as equivalent to the steering angle change. 4, the steering angle change in the lost section is predicted. As shown in FIG. 4D, the travel difficulty Diff becomes higher as the steering angle change is larger and the change amount of the steering angle change is larger as the steering angle change is larger. It sets so that the variation | change_quantity of driving difficulty Diff may become large. In FIG. 4D, the horizontal axis represents the change in steering angle per unit time [rad / s], and the vertical axis represents the travel difficulty Diff.

  Note that the travel difficulty Diff may be set based on various parameters as described above, and a plurality of travel difficulty levels calculated based on the various parameters are weighted to correspond to the plurality of parameters. The travel difficulty Diff may be calculated by adding the travel difficulty. Further, the travel difficulty Diff calculated in this way is further corrected in accordance with the road friction coefficient μ, and the travel difficulty Diff becomes higher as the road friction coefficient μ is smaller. In addition, the travel difficulty Diff may be corrected to be higher as the change in the road gradient is larger.

When the travel difficulty level Diff is calculated in this way, the process proceeds to step S6, and the steering control change distance Da2LK that determines the timing for switching from the fully automatic steering control to the semi-automatic steering control is set.
Specifically, the steering control change distance Da2LK is calculated by multiplying the vehicle speed Vc and a predetermined time set in advance, and the predetermined time is set to become longer as the travel difficulty Diff is higher. Thus, as shown in the characteristic diagram of FIG. 5, the steering control change distance Da2LK is set to be larger as the travel difficulty Diff is larger. In FIG. 5, the horizontal axis represents the travel difficulty Diff, and the vertical axis represents the steering control change distance Da2LK.

Next, the process proceeds to step S7, and the node (Xn, Yn) corresponding to the point immediately before the steering control change distance Da2LK calculated in step S6 is changed from the node (Xlost, Ylost) at the lost start point to the steering control change start point Zs. Set as.
Next, the process proceeds to step S8, and it is determined whether or not the host vehicle has reached a node corresponding to the steering control change start point Zs set in step S7. If the host vehicle has not reached the steering control change start point Zs, the process proceeds to step S9, and fully automatic steering control is performed, which is steering control that places importance on position control over driver steering operation.

  In this fully automatic steering control, the influence of disturbance due to the driver's steering intervention on the steering wheel is minimized, and the steering control is performed so that the vehicle travels along the reference route without requiring the driver's steering intervention. . For example, a steering angle equivalent value capable of controlling the current position of the host vehicle to a target position for traveling along the reference route is given to the steering mechanism as a steering control amount Sδ, and steering is performed by a position control system with high servo rigidity. Take control.

  Specifically, as shown in the flowchart of FIG. 6, first, in step S31, a forward gazing point P1 ahead of the gazing point distance D1 for detecting an error from the reference route is set. As shown in FIG. 7A, the front gazing point distance D1 is set so that the position of the front gazing point P1 becomes a more forward position from the host vehicle as the vehicle speed Vc is higher. In addition to the forward gazing point P1 set at a point ahead of the host vehicle by the forward gazing point distance D1, the second forward gazing point P2 for predicting the future steering amount is set as the second forward gazing point from the host vehicle. In the case of an automatic steering control device that is set to a point ahead by a distance D2 and performs automatic steering control with two types of forward gazing points, as shown in FIG. 7B or FIG. Set the gaze point distance separately. Hereinafter, the case where the forward gazing points P1 and P2 are used will be described. When only the forward gazing point P1 is used, steering control may be performed by a known procedure.

Next, in step S32, a curvature radius ρ for predicting a future steering amount at the second forward gazing point P2 is calculated.
As shown in FIG. 8, a line segment P2P _R to the nearest node in the point taken a predetermined distance Ds back and forth second forward fixed point P2 as the center and P _F and P _R, connecting the P2 and P _R, an angle θ, which forms with a line segment P2P _F connecting the P2 and P _F, and a distance d P _F and P _R are calculated. Here, the predetermined distance Ds is calculated by multiplying the vehicle speed Vc by a fixed time t2 of, for example, about 1 second (Ds = Vc × t2).

In order to suppress the predetermined distance Ds from becoming extremely short, a minimum value D _MIN is provided, and the larger one of the values calculated according to the minimum value D _MIN and the vehicle speed Vc is calculated as the predetermined distance Ds. May be.
Then, the center O of the arc through the P _F, P2 and P _R has a vertical bisector A which passes through the middle point a line segment P2P _F, bisector perpendicular through the midpoint b of the line segment P2P _R and the intersection of is B, the angle θ which forms with the line segment P2P _R and the line segment P2P _F, equal to ∠aOb formed by the vertical bisectors a and B. Further, since the ∠P _F OP _R is twice the AOB, based on the angle θ and the distance d is calculated the radius of curvature ρ based following equation (5).
ρ = d / 2 · sin θ (5)

Next, in step S33, a lateral deviation Y _E with respect to the reference route of the host vehicle is calculated at the forward gazing point P1 for detecting an error. The lateral deviation Y _{E with} respect to the reference route is calculated by adding the lateral deviation Y _S obtained from the vehicle attitude of the host vehicle and the lateral deviation Y _P obtained from the vehicle turning state (Y _E = Y _S + Y _P ).
Specifically, first, the slip angle θs of the vehicle is calculated. The slip angle θs is calculated from the following equation (6) based on the longitudinal acceleration Xg and the lateral acceleration Yg.
θs = tan ⁻¹ (Yg / Xg) (6)

Further, as shown in FIG. 9, the yaw angle of the host vehicle on the reference coordinates is ε ₁ , and the reference path with respect to the reference coordinates at the intersection Q between the straight line C passing through the forward gazing point P1 and perpendicular to the speed vector V and the reference path is shown. When the deviation angle is ε _T , the yaw angle ε _R of the host vehicle with respect to the reference route is expressed by the following equation (7).
ε _R = ε _T −ε ₁ (7)
Furthermore, if the lateral deviation between the reference route and the vehicle position in the initial state is Y _U , the lateral deviation Y _S corresponding to the vehicle posture is the lateral deviation Y _U , the forward gazing distance D1, the yaw angle ε _R, and the slip angle. It is calculated from the following equation (8) based on θs.
Y _S = Y _U + D1 · tan (ε _R + θs) (8)

Next, assuming that the vehicle is making a steady circular turn, the slip rate can be ignored, so the lateral deviation Y _P obtained from the vehicle turning state is expressed by the following equation (9).
Y _P = D1 · tan β (9)
Note that β = 1/2 · sin ⁻¹ (D1 · ε1 / Xg).
Then, based on the lateral deviation Y _S and lateral deviation Y _P calculated by the equations (8) and (9), the lateral deviation Y _E with respect to the reference route is calculated.

Next, in step S34, the first steering amount δ1 is calculated from the following equation (10) based on the lateral deviation Y _E with respect to the reference route passing through the forward gazing point P1.
δ1 = k1 · Y _E + k2 · (dY _E / dt) (10)
Note that k1 and k2 in the equation (10) are coefficients, and it is desirable to obtain an optimum value from an experiment so that the following error does not increase with respect to disturbance during straight running.
Next, in step S35, the second steering amount δ2 is calculated based on the curvature radius ρ calculated in step S32 and the wheel base L of the vehicle.
δ2 = L / ρ (11)

Next, the process proceeds to step S36, and the own vehicle along the reference route is calculated from the following equation (12) based on the first steering amount δ1 calculated in step S34 and the second steering amount δ2 calculated in step S35. The target steering angle δc necessary for traveling is calculated.
δc = δ1 + δ2 (12)
Next, in step S37, a steering torque required to control the actual steering angle to the target steering angle δc calculated in step S36 is calculated and output to the steering actuator 10 as a steering control amount Sδ. Then, the timer interrupt process is terminated and the process returns to a predetermined main program.

As a result, the steering actuator 10 rotates the steering shaft 8 according to the designated steering control amount Sδ, and the steering angle δnow is controlled to become the target control angle δc. Thus, the fully automatic steering control ends.
On the other hand, if the host vehicle has reached the steering control change start point Zs set in step S7 in step S8, the process proceeds to step S10, and it is determined whether or not the GPS lost state in which the radio wave from the GPS satellite is lost. to decide. That is, when the position measurement with high accuracy is impossible based on the radio wave from the GPS satellite, the GPS lost state is determined, and the process proceeds to step S11.

In step S11, the current position of the host vehicle is estimated by dead reckoning. In this dead reckoning, the current position of the host vehicle is estimated by a known procedure based on the values of wheel speeds Vfl to Vrr, lateral acceleration Yg, yaw rate φ, etc. detected by various sensors. In the GPS lost state, the road map information ahead of the host vehicle is read from the storage unit 17 based on the current position information estimated by dead reckoning.
If the current position is estimated by dead reckoning, the process proceeds to step S21 described later.

On the other hand, if the host vehicle is not in the GPS lost state in the process of step S10, the process proceeds to step S12, and it is determined whether or not the state is shifted from the GPS lost state to a state where highly accurate position measurement can be performed. to decide. Then, when the vehicle has passed through the lost section, such as when it has returned from the GPS lost state, the process proceeds to step S9, and the above-described fully automatic steering control is performed.
If it is determined in step S12 that the GPS lost state is not returned to a state where GPS positioning is possible, that is, if the lost section is to be entered, the process proceeds to step S21.

  In step S21, it is determined whether or not the elapsed time after the host vehicle reaches the steering control change start point Zs set in step S7 has reached a predetermined time t11 set in advance. This elapsed time is measured by starting a timer when the host vehicle reaches the steering control change start point Zs in step S8. The predetermined time t11 defines a duration for which semi-automatic steering control, which will be described later, is executed. The predetermined time t11 is a time that can ensure the accuracy of the vehicle position by dead reckoning. When switching from manual steering to manual steering, the time is set so as to avoid giving the driver a sense of incongruity due to a sudden steering load on the driver.

If the predetermined time t11 has not elapsed since the host vehicle reached the steering control change start point Zs, the process proceeds to step S22 to perform semi-automatic steering control.
This semi-automatic steering control secures the cooperation between the automatic steering and the steering operation of the driver, and performs the automatic steering control so that the steering intervention by the driver becomes easy. For example, a steering force equivalent value that can be controlled to a target position for traveling along the reference route from the current position of the host vehicle is given to the steering mechanism as the steering control amount Sδ, and steering control is performed by the force control system.

Specifically, the processing is performed according to the procedure shown in FIG. In FIG. 10, the processing from step S31 to step S35 is the same as the processing in the above-described fully automatic steering control, and the forward gazing points P1 and P2 are set (step S31), and the curvature radius ρ at the front gazing point P2 is calculated. Then, a lateral deviation Y _E with respect to the target route of the vehicle at the forward gazing point P1 is calculated (step S33), and a first steering amount δ1 corresponding to the lateral deviation Y _E is calculated (step S34). Further, the second steering amount δ2 is calculated based on the curvature radius ρ (step S35).

If the first steering amount δ1 and the second steering amount δ2 are calculated in this way, the process proceeds to step S36a, and the first steering amount δ1 calculated in step S34 and the second steering amount δ2 calculated in step S35. Based on the above, the target steering torque Tδ that is finally output to the steering is calculated.
Specifically, first, a deviation Δδ between the current steering angle δnow and the target steering angle δc is obtained. The target steering angle δc is the sum (δc = δ1 + δ2) of the first steering amount δ1 and the second steering amount δ2.

The deviation Δδ is multiplied by a preset gain Kstr, and the target steering torque Tδ is calculated from the following equation (13).
Tδ = Kstr × Δδ (13)
The gain Kstr is a value that changes the deviation Δδ to a torque that allows steering intervention by the driver and can control the steering angle so as to coincide with the target steering angle δc, and is calculated by experimentation or the like. The

When the target steering torque Tδ is calculated in this way, the process proceeds to step S37, and the target steering torque Tδ calculated in step S36a is output to the steering actuator 10 as the steering control amount Sδ. Then, the timer interrupt process is terminated and the process returns to a predetermined main program.
As a result, the steering actuator 10 controls the steering angle to coincide with the target steering angle δc by generating the target steering torque Tδ and applying it to the steering shaft.

Also, in the semi-automatic steering control, a process for notifying the driver of an alarm for notifying the driver that the automatic steering is released, the time until the automatic steering is released, etc. is performed with the passage of the lost section, Encourage the driver to manually steer. Thus, the semi-automatic control process ends.
On the other hand, if the predetermined time has elapsed since the host vehicle reached the steering control change start point Zs in step S21, the process proceeds to step S23, in which the driver is holding the steering wheel, that is, the steering wheel It is determined whether the operation is being performed or the steering is being performed.

This determination is made, for example, by detecting whether or not torque exceeding a preset threshold value is applied to a torque sensor built in the steering column.
When it is determined that the driver does not hold the steering wheel, the process proceeds to step S25, where both the semi-automatic steering control ends. That is, it is difficult to ensure sufficient control accuracy by automatic steering control based on the vehicle position by dead reckoning, and the automatic steering control processing itself is terminated at this point. Thereafter, when the GPS positioning is enabled again, the automatic steering control process is started. At this time, for example, a countermeasure for generating an alarm for notifying the driver of the end of the automatic steering control is taken and the process ends. If it is determined in step S23 that the driver is not gripping the steering wheel, the automatic steering control process is terminated by taking measures such as decelerating or stopping.

  On the other hand, when it is determined in step S23 that the driver is gripping the steering wheel, the process proceeds to step S24, and the traveling distance of the host vehicle from the control change start point Zs set in step S8 is a preset threshold. It is determined whether or not the value LKd2 has been reached. When the travel distance from the control change start point Zs has not reached the threshold value LKd2, the process proceeds to step S22 to perform semi-automatic steering control.

The travel distance threshold LKd2 is longer than the travel distance LKd1 (= predetermined time t11 × Vc) when the elapsed time after reaching the control change start point Zs in step S21 is equivalent to the predetermined time t11. For example, it is set to a value calculated at a predetermined time t12 × Vc. In other words, automatic steering control based on the vehicle position by dead reckoning is difficult to ensure sufficient control accuracy, but the control accuracy of automatic steering control is somewhat reduced because the driver holds the steering wheel. The semi-automatic steering control is performed so that the automatic steering control can be continued. Accordingly, the threshold LKd2 for the travel distance is set to a travel distance that allows the automatic steering control to be continued based on the current position of the host vehicle by dead reckoning while the driver is holding the steering wheel.
On the other hand, when the travel distance from the control change start point Zs reaches the threshold value LKd2, the process proceeds to step S25, and even if the driver holds the steering wheel, it is difficult to perform further automatic steering control. finish.

Next, the operation of the first embodiment will be described.
When the host vehicle M is currently traveling on a travel path that can receive radio waves from GPS satellites satisfactorily, the host vehicle M detects the position of the host vehicle based on the received radio waves from the GPS satellites. Based on the current position of the host vehicle, road map information ahead of the host vehicle is acquired from the storage unit 17 (steps S1 and S2). If it is determined from the road map information that there is no lost section in the predetermined area in front of the host vehicle (step S3), the process proceeds from step S3a to step S9 to perform fully automatic steering control. Do. That is, a target steering angle that can be a target position for the current position of the host vehicle detected by GPS positioning to travel along a reference route obtained from road map information is calculated, and this target steering angle is realized. Thus, the steering actuator 10 is driven.

Thus, the host vehicle travels along the reference route without being affected by the driver's steering intervention or disturbance, and without requiring the driver's steering intervention.
From this state, based on the road map information in front of the host vehicle, there is a tunnel or the like ahead of the traveling path of the host vehicle. Therefore, when there is a lost section that is in the GPS lost state, the process starts at step S3. The point node is detected, and the distance to reach the lost start point is calculated (step S4). Further, the travel difficulty of the lost section is calculated from the road map information (step S5), and the steering control change distance Da2LK is set accordingly (step S6), and the steering control change start point Zs is set (step S6). S7). For example, as shown in FIGS. 4 (a) to 4 (d), when the distance of the lost section is longer, such as when the tunnel section is longer, the traveling difficulty is set to a larger value. When the width is narrower, the driving difficulty level is set to a larger value, and when the tunnel is curved and the curvature thereof is smaller, the driving difficulty level is set to a higher value. The driving difficulty level is set to a larger value as the vehicle is running.

At this time, for example, as shown in FIG. 11, when a tunnel Tu with a relatively short distance exists in front of the host vehicle and the vehicle travels on a straight road, the traveling difficulty is set to a relatively small value. The Conversely, as shown in FIG. 12, when the tunnel Tu is a tunnel having a relatively long distance, the traveling difficulty level is set to a relatively large value.
For this reason, as shown in FIG. 11, in the case of the tunnel Tu having a relatively short distance, the steering control change distance Da2LK is set to a relatively short value, so that the tunnel Tu before the entrance of the tunnel Tu is relatively A near point is set as the steering control change start point Zs. Conversely, as shown in FIG. 12, in the case of a tunnel Tu having a relatively long distance, the steering control change distance Da2LK is set to a relatively long value, so that it is relatively far from the tunnel Tu before the entrance of the tunnel Tu. The point is set as the steering control change start point Zs.

Then, until the host vehicle reaches the steering control change start point Zs, the process returns from step S8 to step S9 through step S9, and the host vehicle continues on the reference route based on the host vehicle position obtained by GPS positioning. Automatic steering is performed by fully automatic steering control that places importance on position control so as to travel along the road.
When the host vehicle reaches the steering control change start point Zs, the process proceeds from step S8 to step S10. However, when the vehicle is not in the lost GPS state, the process proceeds from step S10 to step S12 and step S21 to step S22. Based on the current position of the host vehicle detected by the above, automatic steering is performed by semi-automatic steering control with an emphasis on cooperation with the driver, and then the predetermined time t11 has elapsed since the host vehicle reached the steering control change start point Zs. Until the time elapses, that is, in the section shown in FIG. 11 until the travel distance from the steering control change start point Zs becomes LKd1, automatic steering by semi-automatic steering control is performed.

Therefore, when the driver recognizes that the vehicle is in the GPS lost state because the vehicle enters the tunnel and performs the steering operation by grasping the steering wheel, the driver performs the steering by the automatic steering while permitting the steering operation. It will be.
Since the length of the tunnel Tu is relatively short, the vehicle finishes passing through the tunnel Tu before the predetermined time t11 elapses, returns from the GPS lost state, and is highly accurate by GPS positioning at the point Zrec in FIG. When the vehicle position can be detected, the process proceeds from step S10 to step S12 through step S12 to perform fully automatic steering control. Therefore, after the point Zrec, the automatic steering by the fully automatic steering control is resumed, and the automatic steering control with an emphasis on position control is performed. Therefore, it is possible to travel along the reference route from the point Zrec without requiring the driver's steering intervention.

  As described above, when entering the tunnel Tu, the GPS lost state is entered. While in the GPS lost state, the automatic steering is continued by performing the automatic steering control by the semi-automatic steering control based on the position detection value by the dead reckoning. However, the steering operation of the driver is allowed. Accordingly, when the vehicle is temporarily in the GPS lost state, such as when traveling in a short tunnel as shown in FIG. 11, the automatic steering is continued by the semi-automatic steering control, so the GPS lost state is temporarily entered. Every time, it is possible to avoid switching to manual steering, and it is possible to avoid giving the driver the troublesomeness of performing manual steering.

  On the other hand, as shown in FIG. 12, the vehicle enters a relatively long tunnel Tu until the predetermined time t11 elapses after the host vehicle reaches the steering control change start point Zs, that is, as shown in FIG. If the GPS lost state does not return from the steering control change start point Zs until the distance LKd1 corresponding to the predetermined time t11 elapses, the process proceeds from step S21 to step S22 until the predetermined time t11 elapses. Thus, the semi-automatic steering control is continued by dead reckoning, but when the predetermined time t11 has elapsed, the process proceeds from step S21 to step S23. At this time, when it is predicted that the driver is in a GPS lost state by passing through the tunnel and it is predicted that the driver is willing to perform manual steering while holding the steering wheel, the process goes from step S23 to step S24 to step S22. Then, automatic steering is performed by semi-automatic steering control, and at a point Zd2 where a predetermined distance LKd2 has elapsed from the steering control change start point Zs, the process proceeds to step S25, where the automatic steering control process ends and switches to manual steering. . Here, at the switching point Zd2, the driver recognizes the switching to the manual steering, grasps the steering wheel, and is ready to perform steering to some extent. Therefore, even if the automatic steering is switched to the manual steering at the point Zd2, the driver does not feel a heavy load for performing the manual steering. Therefore, even if the vehicle is traveling on a road such as a curved road where a steering load is applied to the driver, the steering load on the driver does not increase greatly even when the automatic steering is switched to the manual steering.

  At this time, after the predetermined time t11 has elapsed from the steering control change start point Zs, the accuracy of detection of the current position of the host vehicle due to dead reckoning decreases, but as described above, the driver pushes the steering wheel. Semi-automatic steering control is continued only when the hand is held. Therefore, although the detection accuracy of the current position of the host vehicle is reduced, the decrease in accuracy is compensated for by the driver's steering operation. Steering can be performed, that is, the duration of automatic steering can be further extended, and the steering load on the driver can be reduced accordingly.

On the other hand, if the driver does not hold the steering wheel when the predetermined time t11 has elapsed from the steering control change start point Zs, the process proceeds from step S23 to step S25, where the vehicle is decelerated or stopped to perform automatic steering control processing. Ends.
Therefore, since the automatic steering is released at the time when the detection accuracy of the current position of the host vehicle due to dead reckoning is reduced, it is possible to prevent the automatic steering from being continued based on the current position where the accuracy is reduced.

Further, at this time, as shown in FIG. 11, when the length of the tunnel is long compared to the case where the length of the tunnel is short, the distance of the lost section is long. The traveling difficulty Diff is set to a larger value. As shown in FIG. 5, the steering control change distance Da2LK is set to a longer distance as the travel difficulty level Diff is higher, and the steering control change start point Zs is set to a point before the tunnel entrance point. Therefore, when entering the lost section, the semi-automatic steering control is started at an earlier time as the travel difficulty Diff is higher, and the semi-automatic steering control is performed at a time closer to the lost section as the travel difficulty Diff is lower. Will be started.

  Therefore, when the travel difficulty Diff is low, such as when the lost section is relatively short, the semi-automatic steering control is started at a later time point, so that the semi-automatic steering control is continued until the later time point after entering the lost section. Become. For this reason, it is possible to avoid switching to manual steering during traveling in the lost section when the vehicle is temporarily in a lost GPS state, such as when passing through a short tunnel, and to the driver when switching to manual steering. It is possible to avoid giving annoyance.

  Conversely, when the travel difficulty Diff is high, such as when the lost section is relatively long, semi-automatic steering control is started at an earlier time, and the driver is prompted to switch to manual steering at an earlier time. While traveling on a high road, avoiding the automatic steering from continuing for a long time based on the vehicle position by dead reckoning, which is less accurate than the vehicle detection position by GPS positioning, and prior to entering the lost section, By allowing the driver to grip the steering wheel at an earlier point and directing the driver to perform manual steering from an earlier stage, it is possible to more reliably prepare for manual steering before the end of automatic steering. It is possible to improve safety.

Next, a second embodiment of the present invention will be described.
Since the second embodiment is the same as the first embodiment except that the processing procedure of the automatic steering control process executed by the controller 20 is different, the same parts are denoted by the same reference numerals. Detailed description is omitted.
FIG. 13 is an example of a processing procedure of automatic steering control processing executed in the second embodiment.

In the automatic steering control process in the second embodiment, the processes from step S1 to step S12 are the same as the automatic steering control process shown in FIG. 2 in the first embodiment.
In the second embodiment, as shown in FIG. 13, when position detection by dead reckoning is performed in step S11, or when it is determined that the return from the GPS lost state is not performed in step S12, step S41 is performed. Then, the steering correction integrated amount Er is calculated.

Specifically, an accumulation error of the current position of the host vehicle estimated by dead reckoning is estimated. The larger the accumulated amount of the feedback control amount for correcting the follow-up error, the larger the accumulated error that represents the difference between the actual current position of the own vehicle and the estimated position of the own vehicle. Calculated assuming that
First, in step S44, which will be described later, the target steering torque Tδ calculated in the fully automatic steering control executed in the same manner as the processing in step S9 in FIG. 2 is changed to the GPS lost state, and then position detection by dead reckoning is performed. Integration is performed from the start time, and an integrated value ΣTδ of the target steering torque Tδ is calculated.

Then, the integrated value ΣTδ of the target steering torque Tδ calculated in this way is multiplied by a preset gain K, and this is set as the steering correction integrated amount Er. The gain K is calculated by, for example, experiments.
When the steering correction integrated amount Er is calculated in this way, the process proceeds to step S42, and the travel difficulty Diff calculated in step S5 is corrected according to the magnitude of the steering correction integrated amount Er. Specifically, the travel difficulty Diff is corrected so as to increase according to the steering correction integrated amount Er, and is corrected so that the travel difficulty Diff becomes higher as the steering correction integrated amount Er increases. . Further, based on the corrected travel difficulty Diff, the steering control change distance Da2LK is calculated in the same procedure as the processing of Step S6 and Step S7, and a steering control change start point Zs ′ is newly set.

Then, the process proceeds to step S43, and it is determined whether the predetermined time t11 has elapsed since the host vehicle reached the steering control change start point Zs ′ based on the corrected travel difficulty Diff. Specifically, for example, a representative value of the vehicle speed such as the current vehicle speed Vc or an average value of the vehicle speed Vc in a predetermined period before the present time is set, and the representative value of the vehicle speed is multiplied by a predetermined time t11 to obtain a predetermined value. The distance traveled by the host vehicle at time t11 is calculated, and a point traveled from the newly set steering control change start point Zs ′ by this distance is specified. Then, it is determined whether or not the vehicle has reached this point.
If the host vehicle has not reached the position advanced from the corrected steering control change start point Zs ′ by a distance corresponding to the predetermined time t11, the process proceeds to step S44, and the same process as in step S22. Semi-automatic steering control is performed.

  On the other hand, if the host vehicle reaches a position advanced by a distance corresponding to the predetermined time t11, the process proceeds to step S45, and whether the driver is holding the steering wheel in the same procedure as the process of step S23 of FIG. Judging. If the steering wheel is not gripped, the process proceeds to step S47 and the automatic steering is terminated. If the steering wheel is gripped, the process proceeds to step S46. In step S46, it is determined whether or not the travel distance from the steering control change start point Zs ′ corrected in step S42 has reached a predetermined distance LKd2. If the travel distance has not reached the predetermined distance LKd2, the process proceeds to step 44. Subsequently, the semi-automatic steering control is performed, and when the predetermined distance LKd2 is reached, the process proceeds to step S47 and the automatic steering control process is terminated.

Next, the operation of the second embodiment will be described.
Now, as shown in FIG. 14, it is assumed that the host vehicle travels on a straight road and a tunnel Tu exists in front of the vehicle.
In the own vehicle, as in the first embodiment, when the presence of the lost section is not detected in front of the own vehicle based on the road map information, the process proceeds from step S3a to step S9, and fully automatic steering control is performed. To eliminate the influence of the steering input to the steering mechanism due to the driver's steering intervention, etc., and perform the automatic steering control so that the current position of the own vehicle becomes the target position , without receiving the steering intervention of the driver of the own vehicle Both are in a fully automatic steering state where the vehicle travels along the reference route.

  From this state, when the presence of the lost section is detected in front of the host vehicle, the travel difficulty Diff of the lost section is calculated (step S5), and the steering control change start point Zs is set based on this (step S6, S7). When the host vehicle has not reached the steering control change start point Zs, the process proceeds to step S9 and the fully automatic steering control is continued. If the host vehicle has reached the control change start point Zs, the process proceeds from step S8 to step S9. The process proceeds to step S41 through S10 and S12. Since the steering correction integrated value Er is not calculated while not in the GPS lost state, the steering control change set based on the travel difficulty Diff according to the road information of the lost section set in the step S5. Semi-automatic steering control based on the starting point Zs is performed, but when the GPS lost state occurs and semi-automatic steering control based on the current position of the host vehicle by dead reckoning is performed, it is based on the current position of the host vehicle by dead reckoning. Calculation of the integrated value ΣTδ of the target steering torque Tδ in the semi-automatic steering control is started.

  Then, the steering correction integrated value Er is calculated based on the integrated value ΣTδ, the travel difficulty Diff is corrected accordingly, and the steering control change start point Zs ′ is calculated again according to the corrected travel difficulty Diff. (Step S42). Then, with reference to the corrected steering control change start point Zs ′, it is determined whether or not a predetermined time t11 has elapsed since the host vehicle reached the steering control change start point Zs ′.

  Here, in dead reckoning, the current position of the host vehicle is calculated based on the vehicle speed, yaw rate, lateral acceleration, etc. of the host vehicle, so, for example, when passing through a rut or road dimple during dead reckoning, etc. Depending on the state of the traveling road, the difference between the estimated position of the host vehicle due to dead reckoning and the actual current position may increase, and the detection accuracy of the current position of the host vehicle may decrease. In particular, when the lost section distance is long, automatic steering is performed based on the current position where the detection accuracy is reduced, and the control accuracy of automatic steering may be reduced.

  However, the travel difficulty Diff is corrected according to the steering correction integrated value Er that is an integrated value of the target steering torque Tδ in the semi-automatic steering control, and the target travel position of the host vehicle and the current position of the host vehicle due to dead reckoning are calculated. As the difference is predicted to be large, the travel difficulty Diff is corrected to be higher, and it is assumed that the steering control change start point Zs' is at a point farther from the lost section, before the lost section. The end point of the semi-automatic steering control is corrected so that the end point of the semi-automatic steering control becomes a more forward-pointing point by determining the end timing of the semi-automatic steering control with reference to the steering control change start point Zs ′ that has been brought forward.

  Therefore, when the estimation accuracy of the current position of the host vehicle is lowered due to the influence of the actual road surface condition or the like due to rutting or the like, the end point (Zd1) of the semi-automatic steering control based on the travel difficulty Diff set according to the road information , Zd2), the automatic steering control is terminated at points Zd1 'and Zd2' that are closer to the vehicle, so that the automatic steering is prevented from being continued based on the current position of the host vehicle whose estimated accuracy has decreased. It is possible to improve safety.

  At this time, the travel difficulty Diff is corrected according to the steering correction integrated value Er that is an integrated value of the target steering torque Tδ in the semi-automatic steering control, and the vehicle travels based on the actual control amount, that is, the actual error amount. Since the Difficulty Diff is corrected, the end point of the semi-automatic steering control can be moved forward by a distance corresponding to the influence of rutting or the like, and the end timing of the semi-automatic steering control can be changed to an accurate position. .

In the second embodiment, the case where the end timing of the semi-automatic steering control is advanced by correcting the steering control change start point Zs has been described. However, the present invention is not limited to this.
For example, the end timing may be advanced by shortening the predetermined time t11 and the predetermined distance LKd2 that define the end timing of the semi-automatic steering control in accordance with the corrected travel difficulty Diff.

  In this case, for example, at the predetermined time t11 and the predetermined time t12 that defines the predetermined distance LKd2, as shown in the control map of FIG. Multiplication is performed to correct these predetermined times t11 and t12, and semi-automatic steering is performed based on the predetermined distance LKd2 set in accordance with the corrected predetermined time t11 and the corrected t12 in the processing of steps S43 and S46 of FIG. What is necessary is just to judge whether control is complete | finished.

In the second embodiment, the case where the steering correction integrated value Er is calculated from the integrated value of the target steering torque Tδ has been described. However, the present invention is not limited to this. For example, the target steering angle δc and the current steering angle δc are calculated. A value corresponding to an estimation error of the current position of the vehicle due to dead reckoning, such as an integrated value of a difference Δδ with respect to the steering angle δnow, may be calculated.
In the second embodiment, the case where the travel control change start point Zs is corrected regardless of the magnitude of the steering correction integrated value Er has been described. For example, the steering correction integrated value Er is a threshold value. The travel control change start point Zs may be corrected when the value becomes greater than the value and it is determined that a certain amount of estimation error has occurred.

  Further, in each of the above embodiments, the case where the position information of the lost section is acquired from the road map information has been described. However, the present invention is not limited to this, for example, the inter-vehicle communication for performing inter-vehicle communication with other vehicles. Equipped with a communication device and road-to-vehicle communication device for performing road-to-vehicle communication with infrastructure equipment arranged on the roadside side, and position information of the lost section from other vehicles or the roadside side by vehicle-to-vehicle communication or road-to-vehicle communication You may make it acquire.

In each of the above embodiments, the case where the position of the tunnel is detected as the lost section has been described. However, the present invention is not limited to the tunnel, and for example, receives radio waves from GPS satellites due to topographical problems. A point where it is difficult to receive radio waves from a GPS satellite, such as a section where it cannot be performed, may be set as a lost section.
In each of the above embodiments, after the GPS lost state is reached, the current position of the host vehicle is estimated by dead reckoning, and semi-automatic steering control is continued for a predetermined period based on the estimated current position of the host vehicle. However, the present invention can be applied even when the automatic steering is terminated when the GPS lost state is reached without performing dead reckoning.

  In the first embodiment, the GPS 16 corresponds to the vehicle position detection means, and the road map ahead of the vehicle from the storage unit 17 based on the vehicle position detected by the GPS 16 in the process of step S1 in FIG. The process of acquiring information corresponds to the reference route detection means and the lost information acquisition means, the process of step S3 corresponds to the lost section detection means, the process of step S5 corresponds to the travel difficulty level detection means, and the process of step S11 Corresponds to the vehicle position estimation means. 2 corresponds to the steering control unit, the processing of step S9 corresponds to the fully automatic steering control unit, and the processing of step S22 corresponds to the semi-automatic steering control unit. Further, the processing from step S4 to step S8, step S10 to step S21, and step S23 to step S25 in FIG. 2 corresponds to the steering control switching means, and the processing of step S23 corresponds to the steered state detection means.

  Further, in the second embodiment, the GPS 16 corresponds to the own vehicle position detecting means, and road map information ahead of the own vehicle from the storage unit 17 based on the own vehicle position detected by the GPS 16 in the process of step S1 in FIG. The process of acquiring S corresponds to the reference route detection means and the lost information acquisition means, the process of step S3 corresponds to the lost section detection means, the process of step S5 corresponds to the travel difficulty level detection means, and the process of step S11 It corresponds to the vehicle position estimation means. Further, the processing in step S9 and step S44 in FIG. 13 corresponds to the steering control means, the processing in step S9 corresponds to the fully automatic steering control means, and the processing in step S44 corresponds to the semi-automatic steering control means. Further, the processing from step S4 to step S8, step S10 to step S43, and step S45 to step S47 in FIG. 13 corresponds to the steering control switching means, the processing at step S45 corresponds to the steering holding state detecting means, The processing corresponds to the accumulated error detection means, and the processing in step S43 corresponds to the end timing adjustment means.

It is a schematic block diagram which shows an example of the automatic steering control apparatus in this invention. It is a flowchart which shows an example of the process sequence of the automatic steering control process performed with the controller of FIG. It is explanatory drawing which shows the structure of road map information. It is a map for setting a travel difficulty level. It is a map showing a response | compatibility with travel difficulty Diff and steering control change distance Da2LK. It is a flowchart which shows an example of the process sequence of the fully automatic steering control process of FIG.2 S9. It is a map for setting a forward gazing point distance. It is a figure explaining the calculation method of the road curvature radius in the 2nd front gaze point P2. It is explanatory drawing for demonstrating the calculation method of the lateral deviation Ye in the 1st front gaze point P1. It is a flowchart which shows an example of the process sequence of the semiautomatic steering control process of FIG.2 S22. It is explanatory drawing with which it uses for operation | movement description of the 1st Embodiment of this invention. It is explanatory drawing with which it uses for operation | movement description of the 1st Embodiment of this invention. It is a flowchart which shows an example of the process sequence of the automatic steering control process in 2nd Embodiment. It is explanatory drawing with which it uses for operation | movement description of 2nd Embodiment. It is a map showing the correspondence between the travel difficulty Diff and the correction coefficient.

Explanation of symbols

1FL to 1RR Left front wheel to right rear wheel 2 Engine 3 Automatic transmission 5 Final reduction device 8 Steering shaft 9 Steering wheel 10 Steering actuator 11FL to 11RR Wheel speed sensor 12 Longitudinal acceleration sensor 13 Lateral acceleration sensor 14 Yaw rate sensor 15 Steering angle sensor 16 GPS
17 Storage unit 20 Controller

Claims (9)

Own vehicle position detecting means for detecting the own vehicle position;
Reference route detection means for detecting a reference route on which the host vehicle travels;
In an automatic steering control device comprising: steering control means for performing steering control so that the host vehicle travels along the reference route based on the host vehicle position detected by the host vehicle position detection unit;
The steering control means is a fully automatic steering control means for performing steering control giving priority to position control for the host vehicle to travel along the reference route;
Semi-automatic steering control means for allowing steering intervention of a driver and performing steering control so that the host vehicle travels along the reference route;
A lost section detecting means for detecting a lost section on the reference route where the position of the own vehicle is difficult to detect by the own vehicle position detecting means;
When the vehicle position detection means can detect the vehicle position, the fully automatic steering control means is activated,
When the lost section is detected on the reference route ahead of the own vehicle by the lost section detecting means, the fully automatic steering control means is changed at a preset timing before the own vehicle enters the lost section. An automatic steering control device comprising: steering control switching means for operating the semi-automatic steering control means. Detecting the road situation of the reference route after the lost section detected by the lost situation detection means, comprising a travel difficulty detection means for detecting the travel difficulty of the host vehicle based on the road situation,
2. The automatic steering control apparatus according to claim 1, wherein the steering control switching means changes a switching timing to the semi-automatic steering control means according to the travel difficulty detected by the travel difficulty detection means.   3. The automatic steering control device according to claim 2, wherein the steering control switching means switches to the semi-automatic steering control means at a point closer to the front from the lost section as the travel difficulty level is higher.   The travel difficulty level detection means is configured to detect the travel difficulty based on at least one of a continuation distance of the lost section, a road width of the lost section, a road curvature of the lost section, and a road curvature change state of the lost section. The automatic steering control device according to claim 2 or 3, wherein the degree is detected. A vehicle position estimating means for estimating the vehicle position when it becomes difficult to detect the vehicle position by the vehicle position detecting means;
The said semi-automatic steering control means performs the said steering control based on the own vehicle position detected by the said own vehicle position detection means, or the own vehicle position estimated value estimated by the said own vehicle position estimation means. The automatic steering control device according to any one of claims 1 to 4. Comprising a steering state detection means for detecting whether the driver is holding the steering wheel;
The steering control switching means extends the control period of the semi-automatic steering control means when detecting that the driver is holding by the steering status detection means during the steering control by the semi-automatic steering control means. The automatic steering control device according to claim 5. The steering control switching means, during the steering control based on the vehicle position estimated value estimated by the vehicle position estimating means, accumulation error detection means for detecting an accumulation error of the vehicle position estimated value with respect to the reference route,
The automatic steering control according to claim 5, further comprising: an end timing adjusting unit that advances an operation end timing of the semi-automatic steering control unit according to the storage error detected by the storage error detecting unit. apparatus. The end timing adjustment means corrects the travel difficulty detected by the travel difficulty detection means according to the accumulation error,
8. The automatic steering control apparatus according to claim 7, wherein the steering control switching means sets the control period with reference to an operation start time of the semi-automatic steering control means specified by the corrected travel difficulty level. Comprising lost information acquisition means for acquiring lost section information representing the position of the lost section ahead of the host vehicle;
The automatic steering according to any one of claims 1 to 8, wherein the lost section detecting means detects the lost section based on lost section information acquired by the lost information acquiring means. Control device.

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