Vehicle control method and vehicle control device

Abstract

In this vehicle control method, a controller (18) executes: a process (S3) for determining whether or not a vehicle (1) has stopped when braking has been applied to the vehicle (1); and processes (S8–S12) for stopping the vehicle (1) in a state in which the ground longitudinal acceleration of the heads (21a, 21b) of the occupants of the vehicle (1) has been reduced, by temporarily causing the vehicle (1) to move forward from the time when it was determined that the vehicle (1) had stopped.

Description

Vehicle control method and vehicle control device

[0001] The present invention relates to a vehicle control method and a vehicle control device.

[0002] The braking control device described in Patent Document 1 listed below reduces the braking force on the front wheels and increases the braking force on the rear wheels immediately before the vehicle is stopped by braking, thereby reducing the vehicle body sway back after stopping.

[0003] Japanese Patent Application Laid-Open No. 2020-019409

[0004] The comfort of an occupant is affected by the forward and backward movement of the head that accompanies the vehicle behavior. The present invention aims to suppress the forward and backward movement of the occupant's head when the vehicle is stopped by braking.

[0005] In one aspect of the vehicle control method of the present invention, a controller executes a process of determining whether the vehicle has stopped when braking the vehicle, and a process of stopping the vehicle in a state in which the longitudinal acceleration of the heads of the vehicle occupants relative to the ground is reduced by temporarily moving the vehicle forward from the point in time when it is determined that the vehicle has stopped.

[0006] According to the present invention, forward and backward movement of an occupant's head can be suppressed when a vehicle is stopped by braking. The objects and advantages of the present invention will be realized and attained by means of the elements and combinations set forth in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not intended to be limiting of the invention as claimed.

[0007] 1 is a schematic diagram illustrating an example of a vehicle control device according to an embodiment. (a) to (d) are schematic diagrams illustrating an example of a vehicle control method according to an embodiment. (a) is a time chart of longitudinal acceleration of a vehicle during braking, (b) is a time chart of the pitch angle of the vehicle body after the vehicle first stops during braking, and (c) is a time chart of the ground longitudinal acceleration of an occupant's head after the vehicle first stops during braking. (c) is a graph illustrating the relationship between the pitch angle of the vehicle body at the time of stopping due to braking and the maximum value of the ground longitudinal acceleration generated in the occupant's head thereafter. (a) is a time chart that schematically illustrates the ground longitudinal acceleration generated in the occupant's head after stopping due to braking, (b) is a time chart that schematically illustrates a longitudinal acceleration pattern that is generated in the vehicle to offset the ground longitudinal acceleration of (a), and (c) and (d) are time charts that schematically illustrate the longitudinal speed and forward movement amount when the longitudinal acceleration pattern of (b) is generated. (b) is a flowchart illustrating an example of a vehicle control method according to an embodiment.

[0008] (Configuration) FIG. 1 is a schematic configuration diagram of an example of a vehicle control device according to an embodiment. The vehicle 1 includes a vehicle control device 10 that controls the driving of the vehicle 1. For example, the vehicle control device 10 may execute driving assistance control that assists the driving of the vehicle 1 when the driver is manually driving the vehicle. For example, the vehicle 1 may be a manually driven vehicle that drives in accordance with manual driving by the driver. Furthermore, for example, the vehicle control device 10 may execute autonomous driving control that automatically drives the vehicle 1 without the involvement of the driver, based on the driving environment around the vehicle 1. In other words, the vehicle 1 may be an autonomously driven vehicle with an autonomous driving function. For example, the vehicle 1 may be an autonomously driven vehicle that can switch between a manual driving mode in which the vehicle 1 is driven manually by the driver and an autonomous driving mode in which the vehicle 1 is driven using an autonomous driving function.

[0009] The vehicle control device 10 includes an object sensor 11, a vehicle sensor 12, a positioning device 13, a map database (map DB) 14, an actuator 17, and a controller 18. The object sensor 11 includes a camera 11a mounted on the vehicle 1 to capture images of the surroundings of the vehicle 1. The camera 11a may be, for example, a stereo camera. The object sensor 11 may also include a plurality of different types of object detection sensors that detect objects around the vehicle 1, such as laser radar, millimeter-wave radar, or LIDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging).

[0010] The vehicle sensors 12 are mounted on the vehicle 1 and detect various information (vehicle signals) obtained from the vehicle 1. The vehicle sensors 12 include, for example, a vehicle speed sensor that detects the vehicle speed of the vehicle 1, a wheel speed sensor that detects the rotational speed of the tires of the vehicle 1, an acceleration sensor that detects the acceleration and deceleration of the vehicle 1, a steering angle sensor that detects the steering angle of the steering wheel, a steering angle sensor that detects the steering angle of the steered wheels, a torque sensor that detects the steering torque applied to the steering wheel, a gyro sensor that detects the angular velocity of the vehicle 1, a yaw rate sensor that detects the yaw rate, an accelerator sensor that detects the accelerator opening of the vehicle 1, a brake sensor that detects the amount of brake operation (for example, a brake pedal sensor that detects the amount of brake pedal operation), and a pitch angle sensor that detects the pitch angle θ of the body of the vehicle 1.

[0011] The positioning device 13 includes a Global Navigation System (GNSS) receiver and receives radio waves from multiple navigation satellites to measure the current position of the vehicle 1. The GNSS receiver may be, for example, a Global Positioning System (GPS) receiver. The positioning device 13 may be, for example, an inertial navigation system. The map database 14 stores road map data. For example, the map database 14 may store high-precision map data (hereinafter simply referred to as "high-precision map") suitable as map information for autonomous driving.

[0012] The actuator 17 drives the steering mechanism, driving force source, and brake device of the vehicle 1 in response to control signals from the controller 18, thereby generating vehicle behavior of the vehicle 1. The actuator 17 includes a steering actuator, an accelerator actuator, and a brake actuator. The steering actuator applies a steering assist force to the steering mechanism of the vehicle 1 in response to control signals from the controller 18, or controls the steering direction and steering amount of the steering mechanism of the vehicle 1. The accelerator actuator controls the driving force and regenerative braking force generated by the driving device, which is an engine or a drive motor, in response to control signals from the controller 18. The brake actuator controls the braking operation of the brake device of the vehicle 1 in response to control signals from the controller 18.

[0013] The controller 18 is an electronic control unit that controls the driving of the vehicle 1. The controller 18 includes a processor 18a and peripheral components such as a storage device 18b. The processor 18a may be, for example, a CPU or an MPU. The storage device 18b may include a semiconductor storage device, a magnetic storage device, an optical storage device, or the like. The storage device 18b may include memories such as a register, a cache memory, and a ROM and a RAM used as a main storage device. The functions of the controller 18 described below are realized, for example, by the processor 18a executing a computer program stored in the storage device 18b. Note that the controller 18 may also be formed by dedicated hardware for executing each of the information processes described below.

[0014] When vehicle 1 is driven manually by the driver, controller 18 calculates a steering assist force based on the steering torque of the steering wheel detected by the torque sensor and outputs a control signal to the steering actuator to generate the calculated steering assist force. When a steering-by-wire system is adopted in which the steering wheel and steered wheels are mechanically separated, controller 18 sets a target steering angle of the steered wheels based on the steering angle of the steering wheel detected by the steering angle sensor and outputs a control signal to the steering actuator to cause the actual steering angle to follow the target steering angle. Controller 18 also calculates a vehicle speed command value for vehicle 1 based on the amount of accelerator pedal operation detected by the accelerator sensor or the amount of brake pedal operation detected by the brake sensor, and outputs control signals to the accelerator actuator and brake actuator to generate driving force and braking force for traveling in accordance with the vehicle speed command value.

[0015] When the vehicle 1 travels under autonomous driving control, the controller 18 generates a route space map representing the route around the vehicle 1 and the presence or absence of objects, and a risk map quantifying the risk of the driving area, based on the positions and postures of objects around the vehicle 1 detected by the object sensor 11 and the high-precision map in the map database 14. The controller 18 generates a driving action plan for the vehicle 1 to automatically travel along the planned driving route, based on the planned driving route set by a navigation system (not shown) or the like, the route space map, and the risk map. The controller 18 generates a target driving trajectory and a vehicle speed command value for the vehicle 1, based on the driving action plan, the motion characteristics of the vehicle 1, and the route space map. The controller 18 outputs a control signal to a steering actuator to control the steering angle of the steered wheels so that the vehicle 1 travels along the target driving trajectory. The controller 18 outputs control signals to an accelerator actuator and a brake actuator to generate driving force and braking force for traveling in accordance with the vehicle speed command value.

[0016] Next, an example of a vehicle control method according to an embodiment using the controller 18 will be described with reference to Figures 2(a) to 2(d). Reference numerals 20a and 20b indicate occupants of the vehicle 1, and reference numerals 21a and 21b indicate the heads of the occupants 20a and 20b, respectively. In the following description, the occupants 20a and 20b may be collectively referred to as "occupant 20," and the heads 21a and 21b of the occupants 20a and 20b may be collectively referred to as "occupant head 21." Figure 2(a) shows the vehicle 1 traveling normally in a straight line, with the occupant 20 in a normal seated position.

[0017] FIG. 2B shows the situation at the moment when the vehicle 1 stops due to a braking operation (i.e., the moment when the vehicle speed becomes zero). When the situation in FIG. 2A transitions to a braking operation, the body of the vehicle 1 generally assumes a forward tilt position due to the braking force 50 generated by the wheels. Reference symbol θ indicates the pitch angle of the vehicle body at the moment when the vehicle 1 stops due to the braking operation. In this specification, the sign of the pitch angle when the vehicle body is in a forward tilt position (i.e., the pitch angle in the direction in which the front end of the vehicle body is lowered) is defined as "positive," and the sign of the pitch angle when the vehicle body is in a backward tilt position (i.e., the pitch angle in the direction in which the front end of the vehicle body is raised) is defined as "negative." The magnitude of the pitch angle θ is determined depending on the deceleration pattern up to the moment when the vehicle speed becomes zero due to braking.

[0018] Furthermore, the moment the vehicle speed reaches zero, the occupant's head 21 assumes a forward tilted position, as indicated by arrow 51 in Figure 2(b). The extent to which the occupant's head 21 tilts forward also depends on the deceleration pattern up until the moment the vehicle speed reaches zero due to braking. After the vehicle 1 comes to a stop, the occupant 20 attempts to return the occupant's head 21 to its normal position (Figure 2(a)). This causes a rearward ground longitudinal acceleration 52 to be generated in the occupant's head 21, as shown in Figure 2(c). The occupant 20 feels discomfort due to the swinging back of the occupant's head 21 as a result of sensing the ground longitudinal acceleration 52 generated in the occupant's head 21.

[0019] Therefore, the controller 18 temporarily moves the vehicle 1 forward from the point at which the vehicle 1 is first stopped by braking. Specifically, the moment the vehicle 1 is first stopped by braking, the brakes are temporarily released and a driving force 53 is generated in one or both of the front and rear wheels so as to cancel out the longitudinal acceleration 52 of the occupant's head 21 relative to the ground, thereby generating a longitudinal acceleration 54 in the entire body of the vehicle 1. As a result, the forward movement of the vehicle 1 assists the occupant 20 in returning the occupant's head 21, which has been tilted forward by braking, to its original position, thereby reducing the longitudinal acceleration 52 of the occupant's head 21 relative to the ground.

[0020] Since the swing-back movement of the occupant's head 21 is largely damped, in a normal seated position, the occupant's head 21 is unlikely to tilt further forward after the rearward ground longitudinal acceleration 52 occurs, and the movement of the occupant's head 21 converges when it returns to its original position (FIG. 2(a)). FIG. 2(d) shows the state when the change in the ground longitudinal acceleration of the occupant's head 21 converges to zero, and at this point the controller 18 again activates the braking function to completely stop the vehicle 1.

[0021] In the following description, the first stop of the vehicle 1 after braking of the vehicle 1 is initiated may be referred to as the "first stop," and the time when the vehicle 1 first stops after braking of the vehicle 1 is initiated may be referred to as the "first stop time." When determining whether the vehicle 1 has first stopped, the controller 18 may determine whether the vehicle 1 has stopped based on whether the vehicle speed detected by the vehicle speed sensor or the wheel speed sensor has become zero. Alternatively, the controller 18 may determine whether the vehicle 1 has stopped based on whether the vehicle speed indicated by the vehicle speed command value calculated by the controller 18 has become zero. Furthermore, the vehicle 1 may be determined to have stopped when the vehicle speed detected by the vehicle speed sensor or the wheel speed sensor or the vehicle speed indicated by the vehicle speed command value reaches a state that can be considered to be zero (for example, when the vehicle speed falls below a small stop determination threshold that is not zero).

[0022] Furthermore, the control that reduces the ground longitudinal acceleration 52 of the occupant's head 21 by temporarily moving the vehicle forward from the point at which the vehicle 1 is first stopped due to braking may be referred to as "head acceleration suppression control." The controller 18 may execute the head acceleration suppression control when the vehicle 1 is braked by manual driving by the driver. That is, the head acceleration suppression control may be executed when the vehicle 1 is stopped by the driver manually operating the braking mechanism (for example, by depressing the brake pedal). The controller 18 may also execute the head acceleration suppression control when the vehicle is braked and stopped by autonomous driving control.

[0023] Next, an example of the movement of the vehicle body and occupant 20 that can be normally assumed when the vehicle 1 is stopped by braking will be described. Figure 3(a) is a time chart of the longitudinal acceleration of the entire vehicle body of the vehicle 1 when braking is performed from a certain predetermined speed (e.g., 20 km / h). In Figures 3(a) to 3(c), the dashed lines show the waveform over time when a gentle braking operation is performed, and the solid lines show the waveform over time when a more abrupt braking operation is performed compared to normal driving. In both cases, the length of the period from the start of braking to the stop of the vehicle 1 is the same, and period R shows a predetermined length (e.g., 2 seconds) starting from the initial stop.

[0024] 3B is a time chart showing an enlarged view of the vehicle pitch angle θ during a period R after the initial stop. When a gentle braking operation is performed (dashed line), the vehicle pitch angle θ is approximately zero at the initial stop. On the other hand, when a sudden braking operation is performed (solid line), a large fluctuation in the pitch angle θ occurs at the initial stop. Thus, the vehicle pitch angle θ at the initial stop depends on the steepness of the braking operation up to the initial stop.

[0025] 3C is a time chart showing an enlarged view of the longitudinal ground acceleration of the occupant's head 21 during a period R after the initial stopping point. When a gentle braking operation is performed (dashed line), the longitudinal ground acceleration of the occupant's head 21 becomes negative immediately before the initial stopping point, causing the occupant's head 21 to swing back toward its original position, but the magnitude of the longitudinal ground acceleration itself is small. On the other hand, when a sudden braking operation is performed (solid line), the swing back of the occupant's head 21 becomes greater, and the longitudinal ground acceleration of the occupant's head 21 increases in the negative direction immediately after the initial stopping point, causing an increased movement of the occupant's head 21 to return to its original position.

[0026] 4 is a graph showing the relationship between the pitch angle θ of the vehicle body at the time of the initial stop and the maximum value of the longitudinal ground acceleration of the occupant's head 21 after the initial stop, which was calculated based on the pitch angle θ of the vehicle body shown in FIG. 3B and the longitudinal ground acceleration of the occupant's head 21 shown in FIG. 3C. The magnitude of the pitch angle θ at the time of the initial stop represents the steepness of the braking operation. A steep braking operation results in the occupant's head 21 tilting forward significantly, which results in a large rebound of the occupant's head 21 to return to its original position. Therefore, a relationship is observed in which the larger the magnitude of the pitch angle θ at the time of the initial stop, the larger the maximum value of the longitudinal ground acceleration that occurs in the occupant's head 21 thereafter.

[0027] Therefore, a time series pattern of the forward movement amount for moving the vehicle 1 forward from the initial stopping point is defined as a basic pattern so that when the vehicle 1 is braked and stopped with a certain deceleration pattern, the forward movement amount for moving the vehicle 1 forward from the initial stopping point is offset to cancel the longitudinal acceleration relative to the ground of the occupant's head 21. Then, by estimating the pitch angle θ that occurs at the initial stopping point when the vehicle 1 is actually braked and correcting the magnitude of the basic pattern in proportion to the estimated pitch angle θ, it is possible to generate a time series pattern of the forward movement amount for moving the vehicle 1 forward so as to offset the longitudinal acceleration relative to the ground that occurs in the occupant's head 21 after the initial stopping point.

[0028] In the following description, the time series pattern of the forward movement amount that moves the vehicle 1 forward so as to offset the ground longitudinal acceleration that occurs in the occupant's head 21 after the initial stopping point may be referred to as the "forward movement pattern ΔL(t)." The forward movement pattern ΔL(t) is a function of the elapsed time t from the initial stopping point, and indicates the forward movement amount of the vehicle 1 at each time t from the point where the vehicle 1 first stopped.

[0029] The basic pattern may be defined, for example, by simulation, or by an experiment in which the vehicle 1 carrying a human or a dummy is braked. In this case, the basic pattern may be set so as to cancel out the longitudinal ground acceleration occurring in the head 21 of a specific occupant 20, or the basic pattern may be set so as to cancel out the longitudinal ground acceleration occurring in the head 21 of an average (standard) occupant 20.

[0030] 5A to 5D are schematic diagrams of the control of the controller 18 after the initial stopping point. FIG. 5A is a time chart schematically illustrating the ground longitudinal acceleration that occurs in the occupant's head 21 after the initial stopping point when head acceleration suppression control is not performed. Ground longitudinal acceleration occurs in the occupant's head 21 during period T1, and the maximum value of the ground longitudinal acceleration is α1. Therefore, during this period T1, acceleration that moves the vehicle 1 forward is generated so as to offset the ground longitudinal acceleration that occurs in the occupant's head 21. Note that because the swing-back motion of the occupant's head 21 is significantly damped, it is assumed that the ground longitudinal acceleration is zero during the period indicated by the dashed line 60 after period T1.

[0031] FIG. 5( b) is a time chart that schematically illustrates a longitudinal acceleration pattern that is generated in the vehicle 1 to offset the longitudinal ground acceleration of FIG. 5( a). The solid line in period T1 indicates the acceleration that moves the vehicle 1 forward to offset the longitudinal ground acceleration that occurs in the occupant's head 21. Because the vehicle 1 must be stopped after accelerating, deceleration is generated in the vehicle 1 during period T2 following period T1. The dashed line in FIG. 5( b) indicates the deceleration that is generated in the vehicle 1. In order to suppress the longitudinal ground acceleration that occurs in the occupant's head 21 due to the deceleration during period T2, the maximum deceleration value α2 during period T2 may be set smaller than the maximum acceleration value α1 during period T1. Therefore, the length of period T2 during which the vehicle 1 is decelerated may be set longer than the length of period T1 during which the vehicle 1 is accelerated. For example, the maximum value α2 of deceleration in period T2 may be equal to or less than half the maximum value α of acceleration in period T1, and the length of period T2 during which vehicle 1 is decelerated may be equal to or greater than twice the length of period T1 during which vehicle 1 is accelerating. The length of the travel distance traveled by vehicle 1 while decelerating in period T2 may be equal to or greater than twice the length of the travel distance traveled by vehicle 1 while accelerating in period T1.

[0032] FIG. 5(c) is a time chart that schematically shows the longitudinal speed when the longitudinal acceleration pattern of FIG. 5(b) is generated. When the longitudinal acceleration pattern of FIG. 5(b) is generated, the vehicle speed of vehicle 1 reaches a maximum speed V at the end of period T1. FIG. 5(d) is a time chart that schematically shows the amount of forward movement when the longitudinal acceleration pattern of FIG. 5(b) is generated. The time chart of FIG. 5(d) corresponds to the above-mentioned forward movement pattern ΔL(t). By the end of period T2 (when head acceleration suppression control ends and vehicle 1 stops again), vehicle 1 moves forward by a total movement amount L from the stop position at the initial stop time and stops.

[0033] Here, when the estimated value of the pitch angle θ at the time of the initial stop is large compared to when it is small, the maximum value α1 of the ground longitudinal acceleration of the occupant's head 21 is large. Therefore, it is necessary to move the vehicle 1 forward with a large acceleration to offset the ground longitudinal acceleration of the occupant's head 21. Therefore, when the estimated value of the pitch angle θ is large compared to when it is small, the maximum value α1 of the acceleration that moves the vehicle 1 forward is larger, and the forward movement pattern ΔL(t) is set so that the total movement amount L becomes longer.

[0034] For example, the forward movement pattern ΔL(t) may be set so that the larger the estimated value of the pitch angle θ, the larger the maximum value α1 of the acceleration that moves the vehicle 1 forward and the longer the total movement amount L. For example, the forward movement pattern ΔL(t) may be set so that the total movement amount L is proportional to the estimated value of the pitch angle θ.

[0035] As described above, the vehicle 1 finally stops at a position that is forward by the total movement amount L from the stop position at the time of initial stopping. Therefore, when the vehicle 1 travels under autonomous driving control (for example, the vehicle is braked and stopped under autonomous driving control), the controller 18 may set an initial stop position at which the vehicle 1 is stopped at the time of initial stopping, depending on the forward movement distance L that the vehicle 1 is moved forward by after the time of initial stopping. For example, the initial stop position may be set at a position that is forward movement distance L before the stop position set for the stop position target (for example, a stop line or an obstacle ahead) at which the vehicle 1 is finally stopped under autonomous driving control.

[0036] (Operation) Figure 6 is a flowchart of an example of a vehicle control method according to an embodiment. In step S1, the controller 18 acquires the vehicle speed of the vehicle 1 from a vehicle speed sensor or a wheel speed sensor. In step S2, the controller 18 acquires the braking state, indicating whether the vehicle 1 is braking. For example, the controller 18 may acquire the braking state from a brake pedal sensor, or may acquire the braking state based on the operating state of a braking device under autonomous driving control.

[0037] In step S3, the controller 18 determines whether the vehicle 1 has stopped due to braking (for example, whether the vehicle 1 has stopped for the first time since braking began) based on the vehicle speed and braking state of the vehicle 1. If the vehicle 1 has not stopped due to braking (step S3: N), the process returns to step S1. If the vehicle 1 has stopped due to braking (step S3: Y), the process proceeds to step S4. In step S4, the controller 18 estimates the pitch angle θ of the vehicle body at the time of the initial stop based on the detection signal of the pitch angle sensor. In step S5, the controller 18 sets a forward movement pattern ΔL(t) whose size is adjusted in proportion to the magnitude of the pitch angle θ.

[0038] In step S6, the controller 18 acquires the vehicle speed of the vehicle 1 from the vehicle speed sensor or wheel speed sensor. Furthermore, the controller 18 acquires obstacle information ahead of the vehicle 1 from the object sensor 11. In step S7, the controller 18 determines whether or not there is no obstacle ahead and the vehicle 1 continues to be stopped. If there is an obstacle ahead or the vehicle 1 is not stopped (step S7: N), the controller 18 does not execute head acceleration suppression control and the process returns to step S1. If there is no obstacle ahead and the vehicle 1 continues to be stopped (step S7: Y), the process proceeds to step S8.

[0039] In step S8, the controller 18 sets a control period Δt for controlling the forward movement of the vehicle 1 in head acceleration suppression control. For example, the control period Δt may be a fixed value or a variable amount. For example, the controller 18 may dynamically set the control period Δt according to the estimated value of the vehicle body pitch angle θ. For example, a shorter control period Δt may be set when the estimated value of the vehicle body pitch angle θ is small compared to when it is small. The controller 18 also resets the time variable t to its initial value ("0"). In step S9, the controller 18 temporarily releases the braking of the vehicle 1 by the braking device.

[0040] In step S10, the controller 18 operates the driving force source or the braking device according to a forward movement pattern ΔL(t) corresponding to the time variable t, thereby generating a driving force in the vehicle 1 during period T1 in FIG. 4(b) and generating a braking force during period T2. In step S11, the controller 18 updates the time variable t (t = t + Δt). In step S12, the controller 18 determines whether the head acceleration suppression control has ended. If the head acceleration suppression control has not ended (step S12: N), the process returns to step S10. If the head acceleration suppression control has ended (step S12: Y), the process proceeds to step S13. In step S13, the controller 18 operates the braking device again to bring the vehicle 1 to a complete stop. The process then ends.

[0041] In the above embodiment, an example of head acceleration suppression control has been described in which the vehicle 1 is caused to move forward from the initial stopping point so as to offset the backward ground longitudinal acceleration that occurs in the occupant's head 21 after the initial stopping point. Similarly, when forward ground longitudinal acceleration occurs in the occupant's head 21 after the initial stopping point, the controller 18 may temporarily move the vehicle 1 backward so as to offset the forward ground longitudinal acceleration.

[0042] For example, when braking a reversing vehicle 1 to a stop, forward longitudinal acceleration relative to the ground may occur in the occupant's head 21 after the vehicle 1 first stops after braking has begun. In such a case, the vehicle 1 may be caused to reverse from the time of initial stoppage to offset the forward longitudinal acceleration relative to the ground that has occurred in the occupant's head 21. Furthermore, for example, after a forward-moving vehicle 1 is stopped by braking, if the momentum that returns the occupant's head 21 to its original position is too strong, the occupant's head 21 may tilt backward. In this case, forward longitudinal acceleration relative to the ground may occur as the occupant 20 tries to return to its original position. In such a case, the vehicle 1 may be caused to reverse from the time of initial stoppage to offset the forward longitudinal acceleration relative to the ground that has occurred in the occupant's head 21.

[0043] When the vehicle 1 is reversed so as to cancel out the forward longitudinal acceleration relative to the ground that has occurred in the occupant's head 21, the controller 18 may acquire obstacle information behind the vehicle 1 using the object sensor 11. When there is no rear obstacle and the vehicle 1 continues to be stopped, the controller 18 may temporarily reverse the vehicle 1 so as to cancel out the forward longitudinal acceleration relative to the ground that has occurred in the occupant's head 21.

[0044] (Effects of the embodiment) (1) The controller 18 executes a process of determining whether the vehicle 1 has stopped when braking the vehicle 1, and a process of temporarily moving the vehicle 1 forward from the point in time when it is determined that the vehicle 1 has stopped, thereby stopping the vehicle 1 in a state in which the longitudinal acceleration of the heads of the occupants of the vehicle 1 relative to the ground is reduced. This makes it possible to suppress longitudinal movement of the heads of the occupants when the vehicle is stopped by braking, thereby improving the comfort of the occupants during braking.

[0045] (2) The controller 18 may estimate the pitch angle of the vehicle body at the time when the vehicle 1 first stops due to braking of the vehicle 1, and may increase the distance by which the vehicle 1 temporarily moves forward after the initial stop when the estimated pitch angle is large compared to when the estimated pitch angle is small. For example, the controller 18 may set the forward movement distance to be proportional to the estimated pitch angle. When braking the vehicle 1, the pitch angle of the vehicle body at the time when the vehicle 1 stops and the longitudinal acceleration of the occupant's head change depending on the steepness of the braking of the vehicle 1. By setting the forward movement distance according to the pitch angle, it is possible to set the forward movement distance that offsets the longitudinal acceleration of the occupant's head.

[0046] (3) The forward travel distance may be set so as to cancel out the longitudinal ground acceleration occurring in the heads of an average occupant or a specific occupant immediately after the vehicle 1 stops when the vehicle 1 is braked. This allows the forward travel distance to be set so as to cancel out the longitudinal ground acceleration of the occupant's heads occurring after the vehicle 1 stops when the vehicle 1 is braked. (4) The controller 18 may accelerate the vehicle 1 over a first distance after the vehicle 1 is initially stopped by braking the vehicle 1, and then decelerate and stop the vehicle 1 over a second distance that is at least twice the first distance. This allows the vehicle 1 to move forward so as to cancel out the longitudinal ground acceleration occurring in the occupant's head, and then finally stop the vehicle 1 while suppressing the longitudinal ground acceleration of the occupant's head.

[0047] (5) If the vehicle 1 is an autonomous vehicle, the controller 18 may set an initial stop position where the vehicle 1 first stops due to braking, depending on the distance the vehicle 1 is moved forward after the initial stop due to braking of the vehicle 1. This allows the vehicle 1 to be stopped at the desired stop position set by the autonomous driving control, even if the vehicle 1 is temporarily moved forward to reduce the longitudinal acceleration of the occupant's head relative to the ground. (6) If there is an obstacle ahead of the vehicle 1, the controller 18 may not execute the process of temporarily moving the vehicle 1 forward. This makes it possible to prevent the vehicle 1 from getting too close to the obstacle.

[0048] (7) The controller 18 may temporarily reverse the vehicle 1 after the initial stop of the vehicle 1 due to braking of the vehicle 1, thereby stopping the vehicle 1 in a state in which the forward longitudinal acceleration relative to the ground that occurs in the head of the occupant after the vehicle 1 has stopped is reduced. This makes it possible to suppress the forward movement of the head of the occupant that occurs when the vehicle 1 is stopped due to braking, thereby improving the comfort of the occupant during braking. (8) If there is an obstacle behind the vehicle 1, the controller 18 may not execute the process of temporarily reverse the vehicle 1. This makes it possible to suppress excessive approach to the obstacle.

[0049] All examples and conditional terms described herein are intended for educational purposes to aid the reader in understanding the present invention and the concepts provided by the inventor for the advancement of technology, and should be construed without limitation to the specifically described examples and conditions above, and the configuration of examples herein for illustrating the advantages and disadvantages of the present invention. Although the embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and alterations can be made thereto without departing from the spirit and scope of the present invention.

[0050] 1...vehicle, 10...vehicle control device, 11...object sensor, 12...vehicle sensor, 13...positioning device, 14...map database, 17...actuator, 18...controller, 18a...processor, 18b...storage device

Claims

1. A vehicle control method characterized in that a controller executes the following processes: determining whether the vehicle has stopped when the vehicle is braked; and stopping the vehicle in a state in which the longitudinal acceleration of the heads of vehicle occupants relative to the ground is reduced by temporarily moving the vehicle forward from the point in time when it is determined that the vehicle has stopped.

2. The vehicle control method according to claim 1, characterized in that the controller estimates a pitch angle of the vehicle body at the time when the vehicle is first stopped due to braking of the vehicle, and increases the distance by which the vehicle is temporarily moved forward after the first stop when the estimated pitch angle is large compared to when the estimated pitch angle is small.

3. The vehicle control method according to claim 2, wherein the controller sets a forward distance proportional to the estimated pitch angle.

4. A vehicle control method as claimed in claim 2 or 3, characterized in that the forward travel distance is set so as to offset the longitudinal acceleration with respect to the ground that occurs in the head of an average occupant or a particular occupant after the vehicle comes to a stop when braking the vehicle.

5. A vehicle control method as described in any one of claims 1 to 4, characterized in that the controller accelerates the vehicle over a first distance after an initial stop of the vehicle due to braking of the vehicle, and decelerates and stops the vehicle over a second distance that is at least twice the first distance.

6. A vehicle control method as claimed in any one of claims 1 to 5, characterized in that, when the vehicle is an autonomous vehicle, the controller sets an initial stop position where the vehicle is initially stopped due to braking, depending on a forward distance the vehicle is advanced forward after an initial stop of the vehicle due to braking of the vehicle.

7. A vehicle control method as described in any one of claims 1 to 6, characterized in that the controller does not execute a process to temporarily move the vehicle forward when an obstacle is present ahead of the vehicle.

8. A vehicle control method as claimed in any one of claims 1 to 7, characterized in that the controller temporarily reverses the vehicle after an initial stop of the vehicle due to braking of the vehicle, thereby stopping the vehicle in a state in which forward longitudinal acceleration relative to the ground generated in the head of the occupant after the vehicle has stopped has been reduced.

9. The vehicle control method according to claim 8, wherein the controller does not execute the process of temporarily moving the vehicle backward when an obstacle is present behind the vehicle.

10. A vehicle control device comprising a controller that executes a process of determining whether the vehicle has stopped when the vehicle is braked, and a process of stopping the vehicle in a state in which the longitudinal acceleration of the heads of the vehicle occupants relative to the ground is reduced by temporarily moving the vehicle forward from the point in time when it is determined that the vehicle has stopped.

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