Driving assistance system, driving assistance method, and driving assistance program

Abstract

The present invention provides a driving assist system capable of ensuring stability of a vehicle and suppressing reduction in lateral displacement amount. The driving assist system causes a processor to perform, in order to assist driving of a host vehicle (Vh), planning a target trajectory of the host vehicle (Vh), and controlling movement of the host vehicle (Vh) in accordance with the target trajectory by adjusting, with respect to a reference longitudinal direction X, front wheel steering angles (δ f ) and rear wheel steering angles (δ r ) respectively imparted to front wheel portions (60f) and rear wheel portions (60r) from a steering manipulation actuator. Also, in a case where the host vehicle (Vh) is decelerated in association with lateral displacement, a target trajectory that generates a body slip angle (β) and a yaw rate (γ) is calculated, the body slip angle (β) being a body slip angle generated by controlling the front wheel steering angles (δ f ) and the rear wheel steering angles (δ r ) in phase with respect to the reference longitudinal direction (X), and the yaw rate (γ) being a yaw rate generated by a difference between the front wheel steering angles (δ f ) and the rear wheel steering angles (δ r ).

Description

Technical Field

[0001] This disclosure relates to driver assistance technologies for assisting the driving of vehicles. Background Technology

[0002] In the vehicle behavior control system disclosed in Patent Document 1, the steering of the rear wheels is controlled while decelerating to avoid an obstacle. The vehicle behavior control system increases the lateral movement of the vehicle by steering the rear wheels in the opposite direction to the direction of avoidance.

[0003] Patent Document 1: Japanese Patent No. 5988171

[0004] In the driving assistance technology disclosed in Patent Document 1, when a large braking force is generated, there is a possibility that the lateral force of the rear wheel being steered in the opposite direction cannot be fully utilized, and the amount of lateral movement based on yaw motion is reduced. In addition, because the lateral force of the tire generated by the rear wheel steering angle in the opposite direction exceeds the limit of the friction circle, there is also a possibility that the slippage in the longitudinal direction will increase, and the vehicle will become unstable. Summary of the Invention

[0005] The purpose of this disclosure is to provide a driving assistance system, driving assistance method, and driving assistance program that can ensure vehicle stability and suppress the reduction of lateral movement.

[0006] To achieve the above objectives, one disclosed method is a driving assistance system for assisting the driving of a main vehicle, having at least one processor. The system is configured such that at least one processor performs the following processes: planning a target trajectory for the main vehicle; and adjusting the front wheel steering angle and rear wheel steering angle respectively assigned to the front and rear wheels by steering actuators relative to a reference longitudinal direction within the main vehicle to control the movement of the main vehicle according to the target trajectory. Planning the target trajectory includes: calculating a target trajectory that generates a vehicle slip angle and a yaw rate while the main vehicle decelerates due to lateral movement. The vehicle slip angle is generated by controlling the front wheel steering angle and rear wheel steering angle in phase relative to a reference longitudinal direction. The yaw rate is generated by the difference between the front wheel steering angle and the rear wheel steering angle.

[0007] Another disclosed method is a driving assistance method executed by at least one processor to assist in driving a master vehicle. This method includes: planning a target trajectory for the master vehicle; and adjusting the front wheel steering angle and rear wheel steering angle, respectively, applied to the front and rear wheels by steering actuators relative to a reference longitudinal direction within the master vehicle, to control the movement of the master vehicle according to the target trajectory. Planning the target trajectory includes: calculating a target trajectory that generates a vehicle slip angle and a yaw rate while the master vehicle decelerates due to lateral movement. The vehicle slip angle is generated by controlling the front wheel steering angle and rear wheel steering angle in phase relative to a reference longitudinal direction, and the yaw rate is generated by the difference between the front wheel steering angle and the rear wheel steering angle.

[0008] Another disclosed method is a driving assistance program stored in at least one storage medium for assisting the driving of a master vehicle. The driving assistance program stored in at least one storage medium includes commands that cause at least one processor to execute: planning a target trajectory (Td) for the master vehicle; and adjusting the front wheel steering angle and rear wheel steering angle respectively assigned to the front and rear wheels by the steering actuators relative to a reference longitudinal direction in the master vehicle to control the movement of the master vehicle according to the target trajectory. Planning the target trajectory includes: calculating the target trajectory to generate a body slip angle and a yaw rate while decelerating the master vehicle with lateral movement. The body slip angle is generated by controlling the front wheel steering angle and rear wheel steering angle in phase relative to a reference longitudinal direction. The yaw rate is generated by the difference between the front wheel steering angle and the rear wheel steering angle.

[0009] In these methods, when the main vehicle decelerates due to lateral movement, the main vehicle is less prone to instability because the rear wheel steering angle is controlled in phase with the front wheel steering angle. Furthermore, since the yaw rate is generated based on the difference between the front and rear wheel steering angles after being steered in phase, the amount of lateral movement is easily ensured. Based on the above, even when the main vehicle decelerates due to lateral movement, the stability of the main vehicle can be ensured, and the reduction in the amount of lateral movement can be suppressed. Attached Figure Description

[0010] Figure 1 This is a block diagram showing an overall image of a driving assistance system according to one embodiment of the present disclosure.

[0011] Figure 2 This diagram illustrates the movement of the main vehicle in a scenario where driver assistance features are used to avoid pedestrians.

[0012] Figure 3 This is a graph showing the relationship between the lateral velocity of the main vehicle and the vehicle body slip angle during in-phase steering maneuvers.

[0013] Figure 4It is a diagram showing the relationship between the front-to-rear forces and the lateral forces of a tire.

[0014] Figure 5 It is a flowchart showing the details of the driving assistance methods performed by the driving assistance system.

[0015] Figure 6 It is a timing diagram showing the details of driving assistance methods.

[0016] Figure 7 This is a timing diagram showing the details of the deceleration adjustment process that begins in conjunction with steering control.

[0017] Figure 8 This is a diagram used to illustrate the margin of lateral tire force required for steering control.

[0018] Figure 9 It is a timing diagram used to illustrate the details of feedback control. Detailed Implementation

[0019] Figure 1 The driving assistance system 100 shown in one embodiment of this disclosure assists in driving a host vehicle Vh. At least a portion of the driving assistance system 100 is mounted on the host vehicle Vh. The host vehicle Vh to which the driving assistance system 100 is applied is capable of performing a manual driving task, for example, in the level of automated driving as specified in SAE J3016, where the automated driving task is accompanied by manual driving assistance from the operator. Such a host vehicle Vh is, for example, a road user such as a car, truck, or bus, and may also be referred to as the ego-vehicle. In summary, as the operator of the host vehicle Vh, the driving assistance system 100 assists the driver who is seated in the passenger compartment of the host vehicle Vh and capable of manual driving.

[0020] like Figure 2 As shown, assuming a traffic scenario in which the main vehicle Vh is traveling, there are at least one of the following as landmarks other than the main vehicle Vh: other road users and structures. Other road users are categorized by their vulnerability level as vulnerable road users and non-vulnerable road users. Vulnerable road users include, for example, pedestrians Pd, etc. Non-vulnerable road users include, for example, at least one vehicle in which people are passengers, such as cars, trucks, buses, motorcycles, and bicycles.

[0021] like Figure 1As shown, in the main vehicle Vh, an actuator assembly 40 is mounted together with at least a portion of the driver assistance system 100. The actuator assembly 40 is configured to control the driving actions of the main vehicle Vh based on control commands from the driver assistance system 100. The actuator assembly 40 includes a drive unit 41, a braking system 42, a front steering actuator 43, and a rear steering actuator 44. The drive unit 41 includes, for example, at least one powertrain actuator such as an internal combustion engine and an electric generator.

[0022] The braking system 42 includes, for example, at least one brake actuator such as a braking unit. Figure 2 As shown, in the main vehicle Vh, a front wheel section 60f including a right front wheel 60fr and a left front wheel 60fl, and a rear wheel section 60r including a right rear wheel 60rr and a left rear wheel 60rl are provided. Figure 3 As shown, the braking system 42 generates independent front wheel braking force Ff for the left and right front wheel portions 60f and independent rear wheel braking force Fr for the left and right rear wheel portions 60r. The braking system 42 independently adjusts the front wheel braking force Ff generated by each front wheel portion 60f and the rear wheel braking force Fr generated by each rear wheel portion 60r via hydraulic pressure. Thus, in the main vehicle Vh, the left-right distribution and front-rear distribution of braking force can be controlled.

[0023] Here, the magnitude of the front wheel braking force Ff can be the same on both sides or different on both sides. Similarly, the magnitude of the rear wheel braking force Fr can be the same on both sides or different on both sides. Furthermore, the magnitudes of the front wheel braking force Ff and the rear wheel braking force Fr can each have at least one side that is the same on both sides, or they can all be different. Moreover, the front wheel braking force Ff and the rear wheel braking force Fr are defined as follows: with the rearward direction in the forward / backward direction of the main vehicle Vh in a top-down view set as the negative direction (or, a completely opposite directional relationship).

[0024] The braking system 42 may also have ABS (anti-lock brake system) control functions to suppress excessive slip ratios of the front wheel 60f and rear wheel 60r, and to adjust the front wheel braking force Ff and the rear wheel braking force Fr. Alternatively, the front wheel braking force Ff and the rear wheel braking force Fr may be generated, for example, using a regenerative brake in the drive unit 41, such as a drive motor. In this case, by having ABS control functions in the braking system 42, the braking force of the regenerative brake of the drive motor can be adjusted according to the slip ratio.

[0025] The front steering actuator 43 imparts a generally shared front wheel steering angle δ to the right front wheel 60fr and left front wheel 60fl of the main vehicle Vh. f The rear steering actuator 44 imparts a generally shared rear wheel steering angle δ to the right rear wheel 60rr and left rear wheel 60rl of the main vehicle Vh.r The front steering actuator 43 and the rear steering actuator 44 independently adjust the front wheel steering angle δ applied to the front wheel section 60f via motor torque. f and the rear wheel steering angle δ assigned to the rear wheel section at 60r r Therefore, in the main vehicle Vh, the front wheel steering angle δ can be controlled. f and rear wheel steering angle δ r The phase relationship.

[0026] Here, the front wheel steering angle δ f and rear wheel steering angle δ r It is defined as follows: taking the phase angle of the reference longitudinal direction X as 0°, setting the counterclockwise direction around the yaw axis in the main vehicle Vh (viewed from above) as the positive direction, and the clockwise direction as the negative direction (or, the completely opposite directional relationship). The reference longitudinal direction X is assumed to be the forward direction, specifically the forward direction, in the main vehicle Vh (viewed from above). Furthermore, the so-called front wheel steering angle δ... f and rear wheel steering angle δ r The phase relationship relative to the reference longitudinal X is adjusted in phase, which means the steering angle δ f δ r The signs of the two angles must be consistent; the steering angle δ f δ r The size can be the same or different. On the other hand, the so-called front wheel steering angle δ f and rear wheel steering angle δ r The phase relationship relative to the reference longitudinal X is adjusted in reverse phase, which means the steering angle δ f δ r The symbols they use need to be different.

[0027] like Figure 1 As shown, in the main vehicle Vh, the driver assistance system 100 is configured to acquire driver operation information, external information, vehicle information, driver monitoring information, and actuator information, etc. The driver operation information includes information related to the driver's driving operations, such as the steering wheel rotation angle (steering wheel angle), the amount of operation of each pedal of the accelerator pedal and the brake pedal.

[0028] External information includes sensing information acquired by external sensors and the vehicle's (Vh's) own position information acquired by a GNSS receiver. External sensors are at least one of the following: onboard cameras, millimeter-wave radar, LiDAR (light detection and ranging / laser imaging detection and ranging), and sonar. Multiple external sensors can also be combined and installed to sense the front, sides, and rear of the vehicle (Vh). The sensing information includes information indicating the relative position, direction of movement, and speed of external objects such as pedestrians (Pd) present outside the vehicle (Vh).

[0029] The vehicle information includes sensing information of the main vehicle Vh acquired by interior boundary sensors. These interior boundary sensors are, for example, at least one of a speed sensor, an acceleration sensor, a gyroscope sensor, and an inertial sensor. The interior boundary sensors sense specific vehicle physical quantities related to the vehicle motion of the main vehicle Vh. The vehicle information includes information such as body speed, wheel speed, yaw rate, steering angle, and steering torque.

[0030] The driver monitoring information includes sensing information acquired by occupant sensors. Occupant sensors are at least one of a driver monitor, a steering touch sensor, and a heart rate sensor. The occupant sensors sense the actions or states of occupants, including the driver, who are passengers in the main vehicle Vh.

[0031] The actuator information includes status information indicating whether the actuator group 40 can operate. For example, the actuator information may indicate whether the brakes in the braking system 42 can operate, or whether the steering control in the front steering actuator 43 and the rear steering actuator 44 can operate.

[0032] The driver assistance system 100 is connected to the actuator assembly 40, external sensors, internal sensors, and occupant sensors, for example, via at least one of a LAN (local area network), wiring harness, internal bus, and wireless communication line. The driver assistance system 100 is configured to include at least one dedicated computer. The dedicated computer is implemented as a control circuit (e.g., a control ECU) or a semiconductor device (e.g., a semiconductor chip). In this embodiment, an example is shown where the entire driver assistance system 100 is integrated into the main vehicle Vh. The driver assistance system 100 includes a driver assistance ECU (Electrical Control Unit) 10 and a motion control ECU 20, which are dedicated computers.

[0033] The dedicated computers constituting the driver assistance ECU 10 and the motion control ECU 20 have at least one processor 31, 36, RAM 32, 37, and storage devices 33, 38. Processors 31 and 36 are arithmetic processing units combined with RAM 32 and 37. Processors 31 and 36 include at least one of a CPU (central processing unit), a GPU (graphics processing unit), and a RISC (reduced instruction set computer) CPU as their core. Storage devices 33 and 38 non-transitory store computer-readable programs (e.g., driver assistance programs) and data. At least one non-transitory tangible storage medium, such as semiconductor memory, magnetic media, or optical media, is used as storage devices 33 and 38.

[0034] The driver assistance ECU 10 plans the driving control within the main vehicle Vh. The driver assistance ECU 10 is an ADAS domain ECU that implements both AD (autonomous driving) and ADAS (advanced driver assistance systems) functions. The driver assistance ECU 10 considers the driver's actions and determines whether emergency avoidance control is needed for objects (obstacles) such as pedestrians Pd. If avoidance is required, it follows the generated target trajectory Td (refer to...). Figure 2 Follow control.

[0035] The driver assistance ECU 10 executes multiple commands contained in the driver assistance program stored as software in the storage device 33 via the processor 31. Thus, the driver assistance ECU 10 incorporates multiple functional modules for assisting in avoiding collisions with obstacles during the driving of the main vehicle Vh. Specifically, the driver assistance ECU 10 incorporates functional modules such as an obstacle avoidance judgment unit 11, a trajectory generation unit 12, a following control unit 13, and a target generation unit 14.

[0036] The obstacle avoidance judgment unit 11 has functions such as external and internal boundary recognition, obstacle collision prediction, and obstacle avoidance judgment. The obstacle avoidance judgment unit 11 acquires external information, vehicle information, and driver monitoring information. Furthermore, the obstacle avoidance judgment unit 11 acquires actuator information from the motion control ECU 20 indicating whether the front wheel section 60f and the rear wheel section 60r can be steered in the same or opposite phases. The obstacle avoidance judgment unit 11 can also acquire inference results regarding the vehicle state quantities of the main vehicle Vh and calculation results regarding the vehicle response (described later) from the motion control ECU 20.

[0037] The collision avoidance determination unit 11 uses acquired external information and vehicle information to generate recognition data that identifies the state of the external and internal environments for each driving scenario of the main vehicle Vh. The collision avoidance determination unit 11 generates recognition data representing relative position, direction of movement, and speed by identifying external landmarks such as other vehicles and pedestrians Pd. Furthermore, the collision avoidance determination unit 11 generates recognition data by identifying the road on which the main vehicle Vh is traveling. Road-related recognition data includes at least one road structure such as position, shape (curvature of curves and road surface superelevation), size, and road surface condition.

[0038] When the obstacle avoidance determination unit 11 identifies an obstacle in the reference longitudinal direction X (front) of the main vehicle Vh based on the forward information of the main vehicle Vh included in the external information, it predicts whether the obstacle will collide with the main vehicle Vh. If the obstacle collision is predicted, the obstacle avoidance determination unit 11 determines that the main vehicle Vh needs to avoid the obstacle. If a collision with the obstacle is predicted, the obstacle avoidance determination unit 11 decides to implement braking control by the braking system 42. Furthermore, the obstacle avoidance determination unit 11 further determines whether steering control is also needed in addition to braking control to avoid the obstacle. If the obstacle avoidance determination unit 11 predicts that a collision with the obstacle will occur solely through braking control, it decides to implement collision avoidance based on lateral movement.

[0039] When obstacle avoidance requires steering control, the obstacle avoidance determination unit 11 determines the start of both braking control and steering control. In this case, the obstacle avoidance determination unit 11 outputs a braking control start flag and a steering control start flag to the track generation unit 12. On the other hand, when steering control is not required, in other words, when it is determined that the obstacle can be avoided by braking control alone, the obstacle avoidance determination unit 11 determines the obstacle avoidance by braking control and outputs a braking control start flag to the track generation unit 12.

[0040] The track generation unit 12 acquires identification data, braking control start flag, and steering control start flag generated by the avoidance judgment unit 11. When the avoidance judgment unit 11 determines that avoidance control is required and acquires the braking control start flag and steering control start flag, the track generation unit 12 uses the identification data to plan the target track Td of the main vehicle Vh (refer to...). Figure 2 The target track Td is the driving track that the master vehicle Vh will follow in its future journey.

[0041] The track generation unit 12 plans the target track Td by defining the time sequence changes of the position coordinates for each control cycle as the trajectory that will follow the main vehicle Vh during future travel. The track generation unit 12 generates the target track Td by directly or indirectly representing at least one of the following physical quantities of motion, such as velocity, acceleration, deceleration, yaw rate γ, and vehicle slip angle β, as motion parameters that appear on the trajectory for each control cycle.

[0042] The track generation unit 12 can calculate the target track Td used for obstacle avoidance control, and the trajectory of the main vehicle Vh as it decelerates and moves laterally to avoid obstacles such as pedestrian Pd. Based on actuator information obtained from the obstacle avoidance determination unit 11, the track generation unit 12 determines the presence or absence of the rear steering actuator 44, as well as the upper limits (limits) of the steering angle and steering angular velocity, which are hardware constraints. When rear wheel steering at 60r is possible, the track generation unit 12 determines whether to perform front wheel steering at δ. f and rear wheel steering angle δ r In-phase and out-of-phase control are implemented. The track generation unit 12 calculates and generates the vehicle slip angle β and yaw rate γ, and the target track Td for obstacle avoidance. The aforementioned vehicle slip angle β is achieved by controlling the front wheel steering angle δ in-phase. f and rear wheel steering angle δ r The resulting vehicle slip angle, the aforementioned yaw rate γ, is obtained through the front wheel steering angle δ. f and rear wheel steering angle δ r The difference in yaw rate. Here, even when making the front wheel steering angle δ... f and rear wheel steering angle δ r Under in-phase control, during the period when the vehicle slip angle β is required, the front wheel steering angle δ f and rear wheel steering angle δ r It is also possible not to maintain the same phase continuously. During the period when the vehicle slip angle β is required, as long as the front wheel steering angle δ... f and rear wheel steering angle δ r Maintaining the same phase for the dominant period is sufficient; alternatively, the front wheel steering angle δ can be temporarily adjusted. f and rear wheel steering angle δ r Inverting control (refer to) Figure 6(Times t3~t4, etc.)

[0043] The follow control unit 13 acquires the target track Td planned by the track generation unit 12. The follow control unit 13 calculates the yaw rate γ (hereinafter, required yaw rate γd) and the vehicle slip angle β (hereinafter, required slip angle βd) for following control to make the main vehicle Vh travel along the target track Td. The follow control unit 13 outputs the calculated required yaw rate γd and required slip angle βd to the motion control ECU 20.

[0044] Here, the required slip angle βd is given by Equation 1 using the required lateral velocity Vyd for travel following the target track Td and the actual forward and backward velocities Vxa of the main vehicle Vh.

[0045] [Formula 1]

[0046]

[0047] The target generation unit 14 acquires the target track Td planned by the track generation unit 12. The target generation unit 14 calculates the target deceleration (hereinafter, the required front-to-back acceleration) for the main vehicle Vh to decelerate along the target track Td. The target generation unit 14 outputs the calculated required front-to-back acceleration to the motion control ECU 20.

[0048] The motion control ECU 20 is a motion domain ECU that controls the motion of the main vehicle. The motion control ECU 20 comprehensively controls the actuator assembly 40 as part of the motion control of the main vehicle Vh. Based on requests from the driver assistance ECU 10, the motion control ECU 20 calculates requests to the actuator assembly 40.

[0049] The motion control ECU 20 executes multiple commands contained in the driving assistance program stored as software in the storage device 38 via the processor 36. Thus, multiple functional modules are constructed within the motion control ECU 20 to assist in avoiding collisions with obstacles during the driving of the main vehicle Vh. Specifically, the motion control ECU 20 includes functional modules such as an arbitration unit 21, a front-rear motion control unit 22, a lateral motion control unit 23, a state quantity inference unit 24, and an actuator allocation calculation unit (hereinafter, ACT allocation calculation unit) 25.

[0050] Arbitration unit 21 arbitrates driving operations performed by the driver and control requests based on the AD or ADAS functions of the driver assistance ECU 10. When the AD and ADAS functions are disabled, arbitration unit 21 outputs driver operation information to the front-rear motion control unit 22 and the lateral motion control unit 23. Conversely, when a control request for obstacle avoidance control or the like is received from the driver assistance ECU 10, arbitration unit 21 outputs the received control request to the front-rear motion control unit 22 and the lateral motion control unit 23. In this case, arbitration unit 21 requests front-rear acceleration to the front-rear motion control unit 22 and requests yaw rate γd and slip angle βd to the lateral motion control unit 23.

[0051] The front-to-rear motion control unit 22 obtains driver operation information or requests for front-to-rear acceleration from the arbitration unit 21. Furthermore, the front-to-rear motion control unit 22 obtains the inference results of vehicle state quantities and the calculation results of vehicle response from the state quantity inference unit 24. Based on the requested front-to-rear acceleration, the front-to-rear motion control unit 22 performs front-to-rear motion control of the main vehicle Vh. In the front-to-rear motion control, feedback control and feedforward control are used for acceleration in the front-to-rear direction. The front-to-rear motion control unit 22 calculates the target front-to-rear force based on the requested front-to-rear acceleration, etc., and outputs the calculated target front-to-rear force to the ACT allocation calculation unit 25.

[0052] The lateral motion control unit 23 obtains driver operation information or requested yaw rate γd and requested slip angle βd from the arbitration unit 21. Furthermore, the lateral motion control unit 23 obtains the inference results of vehicle state quantities and the calculation results of vehicle response from the state quantity inference unit 24. The lateral motion control unit 23 performs lateral motion control of the main vehicle Vh based on the requested yaw rate γd and requested slip angle βd, etc. In lateral motion control, transient response control and feedback control are used to determine the lateral position of the main vehicle Vh. The lateral motion control unit 23 calculates the target yaw rate and target vehicle slip angle based on the requested yaw rate γd and requested slip angle βd, etc. The lateral motion control unit 23 outputs the calculated target yaw rate and target vehicle slip angle to the ACT allocation calculation unit 25.

[0053] The state quantity inference unit 24 acquires actuator information and vehicle information. The state quantity inference unit 24 reads the actuator information and determines whether a rear steering control actuator 44 is installed, and the hardware constraints of each steering control actuator 43, 44 (limits to steering angle and steering angular velocity), etc. The state quantity inference unit 24 sends this information based on the actuator information to the avoidance judgment unit 11 and the ACT allocation calculation unit 25, etc. Furthermore, based on the vehicle information, the state quantity inference unit 24 determines the vehicle speed, wheel speed, and front wheel steering angle δ. f Rear wheel steering angle δ rThe system also calculates the latest vehicle state parameters, such as the actual yaw rate, and infers vehicle state parameters such as the actual slip angle. Furthermore, the state parameter inference unit 24 calculates the vehicle response (yaw response) based on the vehicle information. The state parameter inference unit 24 outputs the inferred vehicle state parameters and the calculated vehicle response to the lateral motion control unit 23, the state parameter inference unit 24, and the ACT allocation calculation unit 25, etc.

[0054] The ACT allocation calculation unit 25 acquires the target front and rear forces, the target yaw rate, and the target vehicle body slip angle. Based on the acquired target values, the ACT allocation calculation unit 25 calculates the workload allocation of the actuator assembly 40 and sets the required front and rear forces and the front wheel steering angle δ. f and rear wheel steering angle δ r The ACT distribution calculation unit 25 outputs control commands (brake request, brake control value) based on the required front and rear braking forces to the braking system 42. The ACT distribution calculation unit 25 can also output brake request commands based on the required front and rear braking forces to the drive unit 41. The ACT distribution calculation unit 25 outputs a forward steering actuator 43 to control the front wheel section 60f to a front wheel steering angle δ. f The control commands (steering request, steering control value) are output from the ACT allocation calculation unit 25 to the rear steering actuator 44, which controls the rear wheel steering angle δ at 60r. r The steering control request command.

[0055] <Detailed explanation of the obstacle avoidance driving assistance process>

[0056] Next, the driving assistance methods used to help avoid collisions with obstacles (pedestrian Pd) while driving the main vehicle Vh will be explained. Figure 2 In the illustrated driver assistance scenario, pedestrian Pd suddenly rushes out from an obstacle SO and into front of the main vehicle Vh. In such a scenario, when braking control alone is insufficient to avoid the obstacle, it becomes necessary to use steering control for lateral movement. Specifically, in the obstacle avoidance control in this scenario, braking control of the main vehicle Vh begins at time t1, and steering control of the main vehicle Vh begins at time t2. The period from time t1 to time t2 is the braking control period Pci, during which only braking control is performed within the obstacle avoidance control period Pc. On the other hand, after time t2, it becomes the cooperative control period Pce, during which both braking and steering control are performed in conjunction within the obstacle avoidance control period Pc.

[0057] As an example, assume that by means of the steering angle δ relative to the front wheels f Controlling the rear wheel steering angle δ in reverse phase r This generates a yaw moment to avoid obstacles laterally. However, in situations such as... Figure 4Under full braking conditions, where the tire's front and rear forces Fx are maximized as shown, the lateral force Fy of the tire decreases in the peak region Pf, where the coefficient of friction between the tire and the road surface is at its maximum. As a result, insufficient lateral force Fy may lead to a reduction in lateral movement. Alternatively, due to exceeding... Figure 3 The limits of the friction circles Fcf and Fcr shown indicate that slippage in the forward and backward directions is enhanced, which in turn raises concerns about the instability of the main vehicle Vh.

[0058] As another example, suppose the front wheel steering angle δ is controlled in phase. f and rear wheel steering angle δ r This avoidance control aims to suppress the yaw rate γ of the main vehicle Vh to approximately zero. In such control, lateral forces Fy on the tires are minimized, thus preventing yaw motion. The tires roll in the avoidance direction, generating a vehicle slip angle β, allowing for obstacle avoidance through lateral movement. However, in avoidance control without yaw motion, the target trajectory Tdn (refer to...) Figure 2 The lateral movement per unit time of the arrow (with a medium-long dashed line) is easily insufficient.

[0059] Therefore, in the driving assistance method of this embodiment, the calculation generates the front wheel steering angle δ by controlling it in phase. f and rear wheel steering angle δ r The resulting vehicle slip angle β and the front wheel steering angle δ f Rear wheel steering angle δ r The target orbit Td (refer to) is generated by the difference in yaw rate γ. Figure 2 (The arrowhead of the dashed line). Based on Figure 5 and Figure 6 , refer to Figures 1-3 The details of the driving assistance procedures used to achieve such avoidance control are explained.

[0060] Furthermore, during the startup of the main vehicle Vh, the driver assistance process is jointly initiated by the driver assistance ECU10 and the motion control ECU20. Figure 5 Repeated execution. Additionally, in the following explanation, each "S" in the driver assistance process represents a series of steps executed by multiple commands within a driver assistance program used to assist in avoiding collisions with obstacles while driving the primary vehicle Vh.

[0061] In S10 of the driving assistance process, the state quantity inference unit 24 reads actuator information to determine whether the front wheel unit 60f and the rear wheel unit 60r can perform steering operations, as well as the limit values ​​of steering angle and steering angular velocity. In the following S20, the state quantity inference unit 24 performs vehicle state quantity inference and vehicle response calculation. Furthermore, the state quantity inference unit 24 sends information indicating whether the front wheel unit 60f and the rear wheel unit 60r can perform in-phase and out-of-phase steering to the avoidance judgment unit 11, etc.

[0062] In step S30, the obstacle avoidance determination unit 11 predicts a collision with an obstacle and determines whether obstacle avoidance control is needed based on external information and vehicle information. If obstacle avoidance control is required, the obstacle avoidance determination unit 11 determines the start of braking control and steering control respectively. In this case, the obstacle avoidance determination unit 11 sends a braking control start flag and a steering control avoidance flag to the track generation unit 12.

[0063] The braking control start flag changes from closed to open at the start time t1 of both the avoidance control period (Pc) and the braking control period (Pci). Similarly, the steering control start flag changes from closed to open at the start time t2 of the cooperative control period (Pce). Both the braking control start flag and the steering control start flag remain open until the end time t10 of both the avoidance control period (Pc) and the cooperative control period (Pce), at which point they change from open to closed.

[0064] In S40, the track generation unit 12 generates the target track Td. The track generation unit 12 calculates the target track Td based on the premise that the vehicle slip angle β and yaw rate γ are generated during the cooperative control period. The track generation unit 12 plans to generate the target track Td with a yaw rate γ in the opposite direction to that generated before avoiding the obstacle after the main vehicle Vh avoids the obstacle (time t9~t10).

[0065] The target generation unit 14 calculates the required front-to-back acceleration to decelerate the main vehicle Vh according to the target track Td, and sends the calculated required front-to-back acceleration to the arbitration unit 21. The required front-to-back acceleration is set so that the braking force is at its maximum during the braking control period Pci from time t1 to time t2. The target generation unit 14 ensures that the braking force does not exceed the limits of the tire's friction circles Fcf and Fcr; in other words, it ensures a margin for the tire's lateral force Fy (refer to...). Figure 8 The acceleration before and after the required adjustment is made at time t2. Furthermore, the shapes of the friction circles Fcf and Fcr are not limited to precise circles. The shapes of the friction circles Fcf and Fcr can also be elliptical or deformed elliptical shapes, etc.

[0066] The target generation unit 14 reduces the braking force in Pce during the cooperative control period after the steering control begins compared to the braking force in Pci during the braking control period before the steering control begins. As a result, the rate of decrease in vehicle speed per unit time in Pce during the cooperative control period is smaller than the rate of decrease in vehicle speed per unit time in Pci during the braking control period.

[0067] The following control unit 13 calculates the required yaw rate γd and required slip angle βd for the main vehicle Vh to move laterally while following the target track Td, and sends these calculated values ​​to the avoidance judgment unit 11. The following control unit 13 calculates the values ​​during the period from time t2 to time t3 after the start of steering control, as well as the rear wheel steering angle δ. r During the period from time t5 to time t6 after the maximum steering angle δrm reaches the upper limit, the required yaw rate γd is increased. The follow-up control unit 13 then reduces the required yaw rate γd to zero during the period from time t7 to time t8.

[0068] Here, when steering control is terminated while a yaw rate γ is generated in the avoidance direction and the main vehicle Vh has a yaw angle, there is a possibility that the main vehicle Vh may go out of the lane due to inertia after the steering control ends. Therefore, during the latter half of the cooperative control period Pce after obstacle avoidance (times t9 to t10), the follow control unit 13 controls the main vehicle Vh to generate a yaw rate γ in the opposite direction to the avoidance direction and to orient the main vehicle Vh along the lane direction. Furthermore, the period from time t2 to time t10 is the interval Pgy during which the yaw rate γ is generated.

[0069] After the required yaw rate γd begins to increase, the follow control unit 13 begins to require the slip angle βd to increase. During the period from the moment t8 when the required yaw rate γd is zero to the moment t9 when the required yaw rate γd is set in the opposite direction, the follow control unit 13 reduces the required slip angle βd to zero. The period during which the required slip angle βd continues to increase or decrease is the gradient range Pgs of the vehicle slip angle β.

[0070] In S50, the front and rear motion control unit 22 performs front and rear motion control, causing the main vehicle Vh to generate front and rear acceleration (braking acceleration) in accordance with the acquired required front and rear acceleration. Specifically, the front and rear motion control unit 22 calculates the target front and rear force based on the required front and rear acceleration and sends the calculated target front and rear force to the ACT allocation calculation unit 25. Meanwhile, the lateral motion control unit 23 performs lateral motion control, causing the main vehicle Vh to generate lateral movement in accordance with the acquired required yaw rate γd and required slip angle βd. Specifically, the lateral motion control unit 23 calculates the target yaw rate and target vehicle slip angle and sends these calculated values ​​to the ACT allocation calculation unit 25.

[0071] In S60, the ACT allocation calculation unit 25 calculates the actuator allocation used to generate target front and rear forces, target yaw rate, and target vehicle body slip angle for the main vehicle Vh. Specifically, the ACT allocation calculation unit 25 calculates the front and rear forces and the front wheel steering angle δ. f and rear wheel steering angle δ r The required values. The ACT allocation calculation unit 25, in order to generate the yaw rate γ in the avoidance direction, sets the front wheel steering angle δ... f Set as the rear wheel steering angle δ r Large. In the following S70, the ACT allocation calculation unit 25 sends these calculated values ​​as a request instruction to the actuator group 40.

[0072] The ACT allocation calculation unit 25 adjusts the front wheel steering angle δ during the period from time t2 to time t6. f The ACT allocation calculation unit 25 maintains the front wheel steering angle δ from time t6 to time t7. f The front wheel steering angle δ will be adjusted from time t7 to time t9. f Return to zero. Front wheel steering angle δ f During the period from time t6 to time t7, the maximum steering angle δfm based on the lateral acceleration constraint described later can also be maintained. During the period from time t9 to time t10, the ACT allocation calculation unit 25 sets the front wheel steering angle δ in the opposite direction to the previous one. f .

[0073] During the period from time t2 to time t3, the ACT allocation calculation unit 25 temporarily steers the rear wheel 60r to increase the yaw rate γ, thereby increasing the rear wheel steering angle δ. r With front wheel steering angle δ f It becomes the opposite phase. During the period from time t3 to time t4, the ACT allocation calculation unit 25 will adjust the rear wheel steering angle δ after the opposite phase steering. r Return to zero. Furthermore, during the period from time t4 to time t5, the ACT allocation calculation unit 25 adjusts the rear wheel steering angle δ. r Switch to front wheel steering angle δ f In phase. Rear wheel steering angle δ r At time t5, the maximum steering angle δrm, constrained by hardware, is reached and remains at its maximum from time t5 to time t8. The ACT allocation calculation unit 25 adjusts the rear wheel steering angle δrm from time t8 to time t9. r Reduced to zero. The ACT allocation calculation unit 25 can maintain the rear wheel steering angle δ during the period from time t9 to time t10. r The value is zero, or the rear wheel steering angle δ can be set in the opposite direction. r With the front wheel steering angle δ f Become the same phase.

[0074] The driver assistance system 100 can terminate the avoidance control after the primary vehicle Vh comes to a stop. Alternatively, the driver assistance system 100 can transfer control of the driving operation to the driver while the primary vehicle Vh continues to move.

[0075] <Characteristic computational processing in driver assistance processes>

[0076] Next, we will further explain the details of the characteristic computational processing performed in each step of the driver assistance process.

[0077] [Constraint settings in orbital calculations]

[0078] In the trajectory calculation of S40 in the driver assistance process, the lateral acceleration of the main vehicle Vh in the gradient interval Pgs of the vehicle slip angle β and the generation interval Pgy of the yaw rate γ is set below or less than the limit value to ensure that it does not exceed the limit value. The limit value of lateral acceleration uses the system upper limit value preset for the driver assistance system 100 (application) and the margin of the inferred lateral force Fy of the tire (refer to...). Figure 8 The side with the smaller median value.

[0079] Furthermore, in the trajectory calculation of S40, the steering angular velocities of the front wheel section 60f and the rear wheel section 60r are set below or less than the limit values ​​in the gradient range Pgs of the vehicle slip angle β and the generation range Pgy of the yaw rate γ, so as not to exceed the limit values. Steering angular velocity is the angular velocity representing the change in steering angle per unit time. The limit value for the steering angular velocity of the front wheel section 60f is the smaller of the system upper limit value preset for the driver assistance system 100 (application) and the upper limit value based on the hardware requirements of the front steering actuator 43. The limit value for the steering angular velocity of the rear wheel section 60r is the upper limit value based on the hardware requirements of the rear steering actuator 44.

[0080] Based on the identification data of the road ahead and obstacles identified by the avoidance judgment unit 11, the track generation unit 12 calculates the trajectory of the main vehicle Vh that avoids obstacles without leaving the driving lane. The track generation unit 12 first sets a minimum track that maintains a minimum lateral movement and a maximum track that allows a maximum lateral movement. The track generation unit 12 calculates the trajectory that satisfies the above-mentioned constraints on lateral acceleration and steering angular velocity, and passes through the range between the minimum track and the maximum track as the target track Td.

[0081] [Road shape correction]

[0082] In the track following control of S40 of the driving assistance process, when the main vehicle Vh is traveling in a curve section, the required yaw rate γd, taking into account the road curvature (hereinafter, curve curvature) of the curve section, is calculated. Based on the identification data of the road ahead generated by the obstacle avoidance judgment unit 11, the following control unit 13 calculates a corrected yaw rate to correct (counteract) the influence of the curve curvature on lateral movement. The following control unit 13 calculates the required yaw rate γd obtained by adding the corrected yaw rate of the curve curvature to the basic yaw rate used to achieve obstacle avoidance track, and sends it to the motion control ECU 20.

[0083] Furthermore, in the track following control of S40, when the main vehicle Vh is traveling on a superelevated surface, a required yaw rate γd considering the inclination of the superelevated surface is calculated. The following control unit 13 calculates a corrected yaw rate to correct (counteract) the influence of the superelevated surface inclination on lateral movement based on the identification data of the road ahead generated by the obstacle avoidance judgment unit 11. The following control unit 13 calculates the required yaw rate γd by adding the corrected yaw rate for the superelevated inclination to the base yaw rate used for obstacle avoidance track, and sends it to the motion control ECU 20.

[0084] [Adjustment of front and rear acceleration to take into account steering control requirements]

[0085] In the target deceleration calculation of S40 in the driver assistance process, based on the limit value of lateral acceleration (system upper limit value) and the inference result of the friction coefficient between the tire and the road surface, the required front-to-back acceleration that does not exceed the tire friction circle Fcf and Fcr is calculated and sent to the motion control ECU20.

[0086] If described in detail, such as Figure 7 As shown, when the ABS operates after the PB (Pre-Clash Brake) command in the Pci during braking control, the state quantity inference unit 24 infers the maximum deceleration (hereinafter, inferred maximum deceleration μ*) between the tire and the road surface based on the actual deceleration during ABS operation. As an example, ... Figure 8 As shown, the value obtained by subtracting the specified inference margin Me from the detected maximum acceleration μd is used as the inferred maximum deceleration μ*.

[0087] When the ABS is not activated after the PB command, the state quantity inference unit 24 can take the generated predetermined deceleration as the inferred maximum deceleration μ*. In addition, when the friction coefficient between the tire and the road surface is inferred normally in the main vehicle Vh, the friction coefficient inferred before the PB command can also be used to set the inferred maximum deceleration μ*.

[0088] The target generation unit 14 calculates the required front-to-back acceleration based on the inferred maximum deceleration μ*, which ensures a margin of lateral force Fy required to generate the required yaw rate γd. For example... Figure 7 and Figure 8 As shown, after the steering of the front wheel unit 60f and the rear wheel unit 60r begins, the target generation unit 14 subtracts the deceleration offset G from the inferred maximum deceleration μ*. x_offset The obtained value is used as the required acceleration before and after. Offset G x_offset The following Equation 2 is given by using the yaw rate g (requiring yaw rate γd), the required change in vehicle body slip angle ω+γ determined by track calculation, and the vehicle body speed V.

[0089] [Equation 2]

[0090]

[0091] The target generation unit 14 takes into account the braking response time Tbi on the entry side and the braking response time Tbr on the exit side, and requires a change in front-to-back acceleration. The target generation unit 14 adjusts the required front-to-back acceleration so that the braking force after the start of steering control is reduced compared to before the start of steering control. The target generation unit 14 uses the smaller value (the increase in deceleration) between the calculated value from Equation 2 and a preset predetermined value as the offset G. x_offset This is used to ensure that the required amount of acceleration before and after is not insufficient.

[0092] In order to achieve rapid deceleration release before the front wheel section 60f and the rear wheel section 60r begin steering, the target generation unit 14 temporarily subtracts the aforementioned offset G from the required front and rear acceleration. x_offset A large value. If the actual deceleration is close to the required acceleration before and after, then to prevent overshoot, the target generation unit 14 will temporarily change the required acceleration before and after to a value similar to the offset G. x_offset The corresponding value.

[0093] [Considering trajectory calculations for deceleration in steering control]

[0094] Based on the target deceleration calculation above, during the cooperative control period, the vehicle speed V of the master vehicle Vh decreases (refer to...). Figure 6 Therefore, in the trajectory calculation of S40, a trajectory calculation taking into account the deceleration of the main vehicle Vh is performed. For a detailed description, the front wheel steering angle δ... f and rear wheel steering angle δ r The following equation 3 is given by using the yaw rate γ and the vehicle body slip angle β.

[0095] [Formula 3]

[0096]

[0097] In Equation 3 above, G rf It is the yaw rate γ relative to the front wheel steering angle δ f steady-state gain, G rr It is the yaw rate γ relative to the rear wheel steering angle δ r The steady-state gain. Additionally, G bf It is the vehicle slip angle β relative to the front wheel steering angle δ f steady-state gain, G br It is the vehicle slip angle β relative to the rear wheel steering angle δ r The steady-state gain. These steady-state gains G rf G rr G bf G br The following equations 4 through 7 are given.

[0098] [Formula 4]

[0099]

[0100] [Formula 5]

[0101]

[0102] [Formula 6]

[0103]

[0104] [Formula 7]

[0105]

[0106] In equations 4 to 7 above, m is the mass of the main vehicle Vh, l is the wheelbase of the main vehicle Vh, and l f It is the distance from the front wheel arch (60f) to the center of gravity, l r It is the distance from the rear wheel at 60° to the center of gravity. And, K f It is the lateral stiffness of the front wheel section 60f, K r Here, θ is the lateral stiffness of the rear wheel at 60r, and V is the vehicle speed. Furthermore, A is a stability factor representing the steering characteristics of the main vehicle Vh. This stability factor A is given by Equation 8 below.

[0107] [Formula 8]

[0108]

[0109] As shown in equations 4 to 7 above, under a given steady-state gain G... rf G rr G bf G brThe formula includes the vehicle speed V of the main vehicle Vh. Therefore, if the main vehicle Vh decelerates through braking control in the steering control, the steady-state gain G... rf G rr G bf G br It also changes. Therefore, the orbit generation unit 12 considers the steady-state gain G. rf G rr G bf G br The changes are used to calculate the target orbit Td.

[0110] Furthermore, as shown in Equation 8 above, the formula for defining the stability factor A includes the respective lateral stiffness K of the front wheel portion 60f and the rear wheel portion 60r. f K r Lateral stiffness K f K r The lateral stiffness K increases or decreases according to the change in ground load on the front wheel section 60f and the rear wheel section 60r as the main vehicle Vh decelerates. Therefore, if the main vehicle Vh decelerates, the lateral stiffness K... f K r Consequently, the stability factor A also changes. Therefore, the orbit generation unit 12 calculates the target orbit Td by taking into account the change in the stability factor A.

[0111] [Variable lateral stiffness]

[0112] In the forward and backward motion control (S50) and actuator allocation calculation (S60) of the driver assistance process, the forward and backward motion control unit 22 and the ACT allocation calculation unit 25 perform control to quickly realize the required forward and backward acceleration received from the following control unit 13. Furthermore, in the lateral motion control (S50) and actuator allocation calculation (S60), the lateral motion control unit 23 and the ACT allocation calculation unit 25 calculate the target front wheel steering angle δ based on the values ​​of the target yaw rate, the target vehicle slip angle, and the current vehicle speed V. f and rear wheel steering angle δ r .

[0113] At this time, the lateral motion control unit 23 or the ACT distribution calculation unit 25 infers the ground load of the front wheel 60f and the rear wheel 60r based on the values ​​of the front and rear accelerations, and sets the lateral stiffness K corresponding to the ground load. f K r By adjusting the lateral stiffness K in lateral motion control f K r The variable allows for the calculation of the front wheel steering angle δ, used to achieve the target yaw rate and target vehicle slip angle, using equations 3 to 8 above, with higher precision. f and rear wheel steering angle δ r .

[0114] [Feedback control of lateral movement]

[0115] In the track following control of S40 in the driver assistance process, feedback control of the vehicle slip angle β and yaw rate γ is performed to improve the following performance on the target track Td. The following control unit 13 implements feedback control of the vehicle slip angle β and yaw rate γ based on the deviation between the target values ​​of the main vehicle Vh's lateral position, lateral velocity, yaw angle, and yaw rate γ on the target track Td and these measured values.

[0116] Here, as Figure 9 As shown, even when the actual lateral movement (hereinafter, actual lateral movement MAa) is insufficient relative to the target value of the lateral movement (hereinafter, target lateral movement MAt), it may be impossible to achieve the rear wheel steering angle δ due to hardware limitations. r Scenarios where the maximum steering angle δrm is increased.

[0117] When the actual lateral movement MAa deviates from the target lateral movement MAt, and the measured value's deficiency relative to the target lateral position exceeds a threshold (reference time t31), the follow control unit 13 increases the required yaw rate γd. This yaw rate output enhances feedback control (reference...). Figure 9 (grid arrow), ACT allocation calculation unit 25 increases the front wheel steering angle δ required by the front steering actuator 43. f This is to increase the yaw rate γ. The ACT allocation calculation unit 25, for example, adjusts the front wheel steering angle δ... f Increase to the maximum steering angle δfm corresponding to the limit value of lateral acceleration (refer to) Figure 9 (The solid line indicating the required steering angle).

[0118] Furthermore, if the amount by which the measured value is insufficient relative to the target value of the lateral position exceeds a threshold, the following control unit 13 extends the rear wheel steering angle δ. r The time during which the maximum steering angle δrm is maintained, in other words, the time during which the vehicle slip angle β is maintained at its maximum. The follow-up control unit 13 shifts the starting time t32 of the required reduction of the slip angle βd backward, extending it to time t33. This slip angle output extension feedback control (see reference) Figure 9 (The arrow at the dot), ACT allocation calculation unit 25 extends the rear wheel steering angle δ required by the rear steering actuator 44. r Maximum maintenance time (refer to) Figure 9 (The required steering angle is indicated by the dashed line).

[0119] Based on the combination of yaw rate output-enhanced feedback control and slip angle output-extended feedback control, the actual lateral movement MAa of the main vehicle Vh can be increased, achieving the corrected actual lateral movement MAc to reach the target lateral movement Mat. Furthermore, when there is a margin in the lateral acceleration limit, yaw rate output-enhanced feedback control can be prioritized over slip angle output-extended feedback control.

[0120] (Summary of Implementation Methods)

[0121] In the previously described embodiment, when the main vehicle Vh decelerates due to lateral movement, due to the front wheel steering angle δ f Controlling the rear wheel steering angle δ in phase r Therefore, the main vehicle Vh is less likely to become unstable. Furthermore, due to the front wheel steering angle δ after in-phase steering... f Rear wheel steering angle δ r The difference between the two factors results in a yaw rate γ, thus making it easy to ensure the amount of lateral movement. Based on the above, even when the main vehicle Vh decelerates due to lateral movement, the stability of the main vehicle Vh can be ensured, and the reduction in the amount of lateral movement can be suppressed.

[0122] Furthermore, in this embodiment, within the gradient range Pgs of the vehicle slip angle β and the generation range Pgy of the yaw rate γ, a target track Td is calculated to ensure that the lateral acceleration of the main vehicle Vh does not exceed a limit. By generating a target track Td that satisfies this constraint of maximum lateral acceleration, instability in the behavior of the main vehicle Vh undergoing lateral movement is suppressed.

[0123] Furthermore, in this embodiment, within the gradient range Pgs of the vehicle slip angle β and the generation range Pgy of the yaw rate γ, target tracks are calculated so that the respective steering angular velocities of the front wheel portion 60f and the rear wheel portion 60r do not exceed the limit values. By generating a target track Td that satisfies such a steering angular velocity constraint, instability in the behavior of the main vehicle Vh, which is moving laterally, is suppressed.

[0124] Furthermore, in this embodiment, a corrected yaw rate is added to the base yaw rate to compensate for the influence of at least one of the curvature of the road surface and the superelevation of the road surface on lateral movement. Therefore, even in scenarios such as driving in curved sections and on roads with superelevation, these effects can be reduced or offset, and the lateral movement of the main vehicle Vh can be appropriately controlled to keep it within the lane.

[0125] Furthermore, in this embodiment, based on the forward information of the main vehicle Vh, the target trajectory Td of the main vehicle Vh is calculated to avoid pedestrian Pd by simultaneously decelerating and moving laterally. Ensuring the amount of lateral movement is crucial in scenarios involving avoiding pedestrian Pd. Therefore, the front wheel steering angle δ after the in-phase turn is calculated.f Rear wheel steering angle δ r The trajectory with a yaw rate γ resulting from the difference is suitable as an obstacle avoidance track for pedestrians such as Pd.

[0126] Furthermore, in this embodiment, after the main vehicle Vh avoids pedestrian Pd, a target track Td with a yaw rate γ in the opposite direction to that generated before avoiding pedestrian Pd is planned. This prevents the main vehicle Vh from going out of the lane due to inertia after the steering control operation ends.

[0127] Furthermore, in this embodiment, a target track Td is planned to begin steering control after braking control begins. In this case, the inferred maximum deceleration μ* at which the friction coefficient between the tire and the road surface reaches its peak is inferred based on the actual deceleration when the ABS is operating before steering control begins. Moreover, the target generation unit 14 reduces the braking force after steering control begins compared to before steering control begins, so as to ensure a margin of lateral force Fy of the tire required to generate yaw rate γ based on the inferred maximum deceleration μ*. Based on the above, during the cooperative control Pce, the lateral force Fy of the tire is not generated solely by exhausting the friction circles Fcf and Fcr through the front and rear forces, thus ensuring the amount of lateral movement.

[0128] Furthermore, in this embodiment, the target trajectory Td is calculated by taking into account the variations in steady-state gains Grf, Grrr, Gbf, and Gbr caused by the deceleration of the main vehicle Vh due to braking control in steering maneuvering control, as well as the variations in the stability factor A of the main vehicle Vh. As described above, by performing calculations that take into account the reduction in vehicle speed V during steering maneuvering avoidance when generating the target trajectory Td, it is easy to execute braking control and steering maneuvering control following the target trajectory Td.

[0129] In this embodiment, the front wheel steering angle δ is calculated using the required slip angle βd and required yaw rate γd for following the target trajectory Td, and the current vehicle speed V of the main vehicle Vh. f and rear wheel steering angle δ r The respective control values ​​are determined. Furthermore, the ground loads of the front wheel section 60f and the rear wheel section 60r are inferred based on the deceleration value of the main vehicle Vh, and the respective lateral stiffnesses Kf and Kr of the front wheel section 60f and the rear wheel section 60r vary according to the ground load. As described above, by considering the increase or decrease in lateral stiffnesses Kf and Kr caused by the load movement accompanying deceleration, braking control and steering control following the target track Td can be easily implemented.

[0130] Furthermore, in this embodiment, feedback control of the vehicle body slip angle β and yaw rate γ is performed based on the deviation between the target lateral movement Mat of the main vehicle Vh based on the target track Td and the actual lateral movement MAa. Moreover, when the actual lateral movement MAa is insufficient relative to the target lateral movement MAt, the front wheel steering angle δ is increased. f The control increases the yaw rate γ by adjusting the steering of the front wheel section 60f. In this way, the control output increases the yaw rate γ by increasing the steering amount of the front wheel section 60f, even when the rear wheel steering angle δ... r While there are constraints, it is also possible to improve the tracking accuracy of the target orbit Td.

[0131] Furthermore, in this embodiment, when the actual lateral movement MAa is insufficient relative to the target lateral movement MAt, the rear wheel steering angle δ is extended. r Maintaining control at its maximum duration. By extending the control that maintains the vehicle's slip angle β at its maximum for an extended period while extending the rear wheel steering input of 60r, it is easy to ensure lateral movement. As a result, tracking accuracy to the target trajectory Td can be improved.

[0132] In addition, in this embodiment, when starting steering control to follow the target trajectory Td, the rear wheel steering angle δ is adjusted. r Temporarily with front wheel steering angle δ f After turning in the opposite phase, the rear wheel steering angle δ is increased. r Switch to front wheel steering angle δ f In-phase control. By generating a yaw rate γ at the rear wheel section 60r through the action of the rear steering actuator 44, the rise in lateral movement response can be improved.

[0133] Furthermore, in the above embodiments, storage devices 33 and 38 correspond to "storage media," the front steering actuator 43 and the rear steering actuator 44 correspond to "steering actuators," and the pedestrian Pd corresponds to "object." Additionally, the required slip angle βd corresponds to "the required value of the vehicle body slip angle," the required yaw rate γd corresponds to "the required value of the yaw rate," and the inferred maximum deceleration μ* corresponds to "the maximum deceleration." Moreover, the target lateral movement MAt corresponds to "the target value of lateral movement," and the actual lateral movement MAa corresponds to "the measured value of lateral movement."

[0134] (Other implementation methods)

[0135] The above describes one embodiment of the present disclosure, but the present disclosure is not limited to the above embodiment and can be applied to various embodiments and combinations without departing from the spirit of the present disclosure.

[0136] The vehicle-mounted ECUs that function as the driving assistance ECU 10 and motion control ECU 20 can also be appropriately modified. In a variation, the driving assistance ECU 10 can be an identification ECU that recognizes the driving environment, a locator ECU that infers its own position, or a navigation ECU that navigates the driving route. Furthermore, the motion control ECU 20 can be an actuator ECU that controls the actuator group 40, or a central ECU that relays multiple ECUs.

[0137] Furthermore, at least some of the functions of the driver assistance ECU 10 and the motion control ECU 20 can also be installed, for example, on a mobile terminal connected to the in-vehicle network of the main vehicle Vh, or on an external central computer capable of communicating with the main vehicle Vh. Moreover, an integrated ECU that combines the functions of the driver assistance ECU 10 and the motion control ECU 20 can also construct a "driver assistance system".

[0138] In a variation, the target track Td that slows down the main vehicle due to lateral movement is also applied outside the track for avoiding pedestrians Pd, etc. For example, the aforementioned target track Td can also be applied to tracks related to lane changes. Furthermore, in a variation, a target track Td can be planned that extends beyond the lane to avoid an object.

[0139] In a variation, the dedicated computer constituting the driver assistance ECU 10 and the motion control ECU 20 may also have at least one of digital circuitry and analog circuitry as a processor. Here, the digital circuitry is, for example, at least one of ASIC, FPGA, SOC, PGA, and CPLD. ASIC stands for Application Specific Integrated Circuit. FPGA stands for Field Programmable Gate Array. SOC stands for System on a Chip. PGA stands for Programmable Gate Array. CPLD stands for Complex Programmable Logic Device. Such digital circuitry may also have a memory storing programs.

[0140] In a variation, the operator of the main vehicle Vh to which the manual driving assistance system 100 is applicable can also be a remote operator who remotely operates the main vehicle Vh from an external center. Alternatively, the driving assistance system 100 can be configured to perform a manual driving assistance task without the need for a human operator, and can only achieve an automatic driving task.

[0141] The combination of "above / below" and "more than / below" when making a determination based on a comparison with a threshold in each of the above embodiments can also be appropriately changed. In other words, when the value to be determined is the same as the threshold, it can be included in either the case of being greater than the threshold or the case of being less than the threshold.

[0142] The control unit and methods described in this disclosure can be implemented by a dedicated computer, which is configured as a processor programmed to perform one or more functions embodied in a computer program. Alternatively, the apparatus and methods described in this disclosure can also be implemented by dedicated hardware logic circuitry. Alternatively, the apparatus and methods described in this disclosure can also be implemented by one or more dedicated computers, which are configured as a combination of a processor executing a computer program and one or more hardware logic circuits. Furthermore, the computer program can also be stored as instructions executed by a computer on a computer-readable non-transferable tangible recording medium.

Claims

1. A driving assistance system having at least one processor for assisting the driving of a main vehicle. The aforementioned driving assistance system is configured such that at least one of the aforementioned processors performs the processing: Plan the target track for the aforementioned main vehicle; and In the aforementioned main vehicle, the front wheel steering angle and rear wheel steering angle, respectively, applied to the front and rear wheels by the steering actuators relative to a reference longitudinal direction, are adjusted to control the movement of the main vehicle according to the aforementioned target trajectory. The above-mentioned target trajectory includes: While the main vehicle is decelerated due to lateral movement, the target trajectory is calculated to generate the vehicle slip angle and yaw rate. The vehicle slip angle is generated by controlling the front wheel steering angle and the rear wheel steering angle in phase with the reference longitudinal direction. The yaw rate is generated by the difference between the front wheel steering angle and the rear wheel steering angle.

2. The driving assistance system according to claim 1, wherein, The above-mentioned target trajectory includes: Within the gradient range of the vehicle body slip angle and the range of yaw rate generation, the target track is calculated so that the lateral acceleration of the main vehicle does not exceed the limit value.

3. The driving assistance system according to claim 1, wherein, The above-mentioned target trajectory includes: Within the gradient range of the aforementioned vehicle body slip angle and the range of the aforementioned yaw rate generation, the target trajectory is calculated so that the respective steering angular velocities of the aforementioned front wheel section and the aforementioned rear wheel section do not exceed the limit value.

4. The driving assistance system according to claim 1, wherein, The above-mentioned target trajectory includes: A modified yaw rate is added to the base yaw rate, which is used to correct the influence of at least one of the curvature of the road and the superelevation of the road surface on the lateral movement of the main vehicle.

5. The driving assistance system according to any one of claims 1 to 4, wherein, The above-mentioned target trajectory includes: Based on the aforementioned information about the main vehicle's front, the target trajectory is calculated so that the main vehicle decelerates while moving laterally to avoid the object.

6. The driving assistance system according to claim 5, wherein, The above-mentioned target trajectory includes: After the main vehicle avoids the object, a target track is planned with a yaw rate in the opposite direction to that generated before avoiding the object.

7. The driving assistance system according to any one of claims 1 to 4, wherein, The above-mentioned target trajectory includes: When the plan is to initiate steering control after braking control begins, the target trajectory described above is to be turned. The maximum deceleration at which the friction coefficient between the tire and the road surface reaches its peak is inferred from the actual deceleration when the ABS is activated before the aforementioned steering control is initiated. The braking force after the steering control is initiated is reduced compared to before the steering control is initiated, so as to ensure a margin of lateral force of the tires required to generate the yaw rate based on the maximum deceleration.

8. The driving assistance system according to any one of claims 1 to 4, wherein, The above-mentioned target trajectory includes: The target trajectory is calculated by taking into account the deceleration of the main vehicle caused by braking control in the steering control, the resulting changes in the steady-state gains of the vehicle body slip angle and the yaw rate relative to the front wheel steering angle and the rear wheel steering angle, and the resulting changes in the stability factor of the main vehicle.

9. The driving assistance system according to any one of claims 1 to 4, wherein, Controlling the movement of the aforementioned main vehicle includes: Using the required values ​​of the vehicle body slip angle and yaw rate for following the target trajectory, and the current vehicle body speed, the control values ​​of the front wheel steering angle and the rear wheel steering angle are calculated. The ground load of the front and rear wheels can be inferred based on the deceleration value of the main vehicle. The lateral stiffness of the front wheel and the rear wheel can be varied according to the ground load.

10. The driving assistance system according to any one of claims 1 to 4, wherein, Controlling the movement of the aforementioned main vehicle includes: Based on the deviation between the target value of the lateral movement of the main vehicle on the target track and the measured value of the lateral movement, feedback control is performed on the vehicle body slip angle and the yaw rate. If the measured value is insufficient relative to the target value of the lateral movement, the yaw rate is increased by increasing the steering angle of the front wheels.

11. The driving assistance system according to any one of claims 1 to 4, wherein, Controlling the movement of the aforementioned main vehicle includes: Based on the deviation between the target value of the lateral movement of the main vehicle on the target track and the measured value of the lateral movement, feedback control is performed on the vehicle body slip angle and the yaw rate. If the measured value is insufficient relative to the target value of the lateral movement, the time for which the rear wheel steering angle is maintained at its maximum is extended.

12. The driving assistance system according to any one of claims 1 to 4, wherein, Controlling the movement of the aforementioned main vehicle includes: When starting to follow the target trajectory for steering control, after turning the rear wheel part in a manner where the rear wheel steering angle is opposite to the front wheel steering angle, the rear wheel steering angle is changed to be in the same phase as the front wheel steering angle.

13. A driving assistance method, executed by at least one processor to assist in driving a main vehicle, comprising: Plan the target track for the aforementioned main vehicle; and In the aforementioned main vehicle, the steering angles of the front and rear wheels, respectively, are adjusted relative to a reference longitudinal direction by the steering actuator, and the movement of the main vehicle is controlled according to the aforementioned target trajectory. The above-mentioned target trajectory includes: While the main vehicle is decelerated due to lateral movement, the target trajectory is calculated to generate the vehicle slip angle and the yaw rate. The vehicle slip angle is generated by controlling the front wheel steering angle and the rear wheel steering angle in phase with the reference longitudinal direction. The yaw rate is generated by the difference between the front wheel steering angle and the rear wheel steering angle.

14. A driving assistance program product stored on at least one storage medium, for assisting the driving of a primary vehicle, and stored on at least one storage medium. The command that causes at least one processor to execute includes: Plan the target track for the aforementioned main vehicle; and In the aforementioned main vehicle, the front wheel steering angle and rear wheel steering angle, respectively, applied to the front and rear wheels by the steering actuators relative to a reference longitudinal direction, are adjusted to control the movement of the main vehicle according to the aforementioned target trajectory. The above-mentioned target trajectory includes: While the main vehicle is decelerated due to lateral movement, the target trajectory is calculated to generate the vehicle slip angle and yaw rate. The vehicle slip angle is generated by controlling the front wheel steering angle and the rear wheel steering angle in phase with the reference longitudinal direction. The yaw rate is generated by the difference between the front wheel steering angle and the rear wheel steering angle.

Images