Vehicle speed control method and vehicle speed control device

Abstract

To prevent behavior of an own vehicle traveling on a target travel trajectory from getting unstable due to frequency of a yaw rate.SOLUTION: In a vehicle speed control method, a target travel trajectory of an own vehicle is set; resonance frequency of a yaw rate of the own vehicle is calculated on the basis of a motion characteristic value of the own vehicle; and a target vehicle speed when the own vehicle travels on the target travel trajectory is set so that frequency of the yaw rate while the own vehicle travels on the target travel trajectory becomes less than the resonance frequency (S2, S3, S17 and S18). Also, in the vehicle speed control method, a vehicle speed of the own vehicle is controlled on the basis of the target vehicle speed (S4).SELECTED DRAWING: Figure 9

Description

[Technical Field]

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

[0002] Patent Document 1 describes a technique for setting a target speed while an autonomously driven vehicle is automatically traveling along a target travel path so that the turning acceleration does not exceed the coefficient of road friction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-121874 Summary of the Invention [Problem to be solved by the invention]

[0004] The yaw motion of a vehicle has a resonance frequency, and if the frequency of the yaw rate of the vehicle approaches the resonance frequency, there is a risk that the vehicle behavior will become unstable. An object of the present invention is to prevent the behavior of a vehicle traveling on a target traveling trajectory from becoming unstable due to the frequency of the yaw rate. [Means for solving the problem]

[0005] In one aspect of the present invention, a vehicle speed control method sets a target driving trajectory for the vehicle, calculates the resonance frequency of the yaw rate of the vehicle based on the vehicle's motion characteristic values, sets a target vehicle speed at which the vehicle will travel on the target driving trajectory so that the frequency of the yaw rate while the vehicle is traveling on the target driving trajectory is less than the resonance frequency, and controls the vehicle speed based on the target vehicle speed. [Effects of the Invention]

[0006] According to the present invention, it is possible to prevent the behavior of the host vehicle traveling on the target traveling trajectory from becoming unstable due to the frequency of the yaw rate. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic configuration diagram of a driving assistance device according to an embodiment; [Figure 2] FIG. 1 is an explanatory diagram illustrating an example of architecture of autonomous driving control by a driving assistance device according to an embodiment. [Figure 3] 2 is a block diagram showing an example of a functional configuration of an automatic driving control unit of the driving assistance device according to the embodiment; FIG. [Figure 4] 2 is a block diagram illustrating an example of a functional configuration of a vehicle control unit illustrated in FIG. 1. FIG. [Figure 5] 1A is an explanatory diagram of an example of a first vehicle speed profile, FIG. 1B is an explanatory diagram of an example of a second vehicle speed profile, and FIG. 1C is an explanatory diagram of an example of a third vehicle speed profile. [Figure 6] 5 is a block diagram illustrating an example of a functional configuration of a backward calculation unit illustrated in FIG. 4. FIG. [Figure 7] 5 is a block diagram illustrating an example of a functional configuration of a forward calculation unit illustrated in FIG. 4. FIG. [Figure 8] 3 is a flowchart illustrating an example of a vehicle speed control method according to an embodiment. [Figure 9] 9 is a flowchart illustrating an example of the process of step S2 in FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the drawings are schematic and may differ from the actual product. Furthermore, the embodiments of the present invention shown below are examples of devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not limit the structure, arrangement, etc. of component parts to those described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims.

[0009] See Figure 1. The host vehicle 1 is either a front-wheel steering vehicle capable of steering a right front wheel 2FR and a left front wheel 2FL, or a four-wheel steering vehicle capable of steering a right front wheel 2FR, a left front wheel 2FL, a right rear wheel 2RR, and a left rear wheel 2RL. Hereinafter, the right front wheel 2FR and the left front wheel 2FL will be collectively referred to as "front wheels 2F," the right rear wheel 2RR and the left rear wheel 2RL will be collectively referred to as "rear wheels 2R," and the front wheels 2F and rear wheels 2R will be collectively referred to as "wheels 2." The host vehicle 1 is equipped with a driving assistance device 10 that provides driving assistance for the host vehicle 1. Driving assistance provided by the driving assistance device 10 may include automatic driving control that automatically drives the host vehicle 1 without the involvement of the driver based on the driving environment around the host vehicle 1, and driving assistance control that assists the driver in driving the host vehicle 1. The driving assistance control may include driving control that controls at least one of the steering device, drive device, and braking device of the host vehicle 1, such as automatic steering, automatic braking, constant speed control, lane keeping control, and merging assistance control.

[0010] The driving assistance device 10 includes an object sensor 11, a vehicle sensor 12, a positioning device 13, a map database (map DB) 14, a navigation device 15, a controller 17, and an actuator 18. The object sensor 11 detects objects around the host vehicle 1. The object sensor 11 includes a plurality of different types of object detection sensors that detect objects around the host vehicle 1, such as a laser radar, a millimeter wave radar, a camera, and a LIDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging).

[0011] Vehicle sensor 12 is mounted on host vehicle 1 and detects various information (vehicle signals) obtained from host vehicle 1. Vehicle sensor 12 includes, for example, a vehicle speed sensor that detects the vehicle speed (traveling speed) V of host vehicle 1, wheel sensors that detect the rotational speed and amount of rotation of wheels 2, a three-axis acceleration sensor (G sensor) that detects the acceleration (including deceleration) in three axial directions of host vehicle 1, a steering angle sensor that detects the steering angle of the steering wheel, a turning angle sensor that detects the turning angle of the steered wheels, a gyro sensor that detects the angular velocity generated in host vehicle 1, a yaw rate sensor that detects the yaw rate, an accelerator sensor that detects the accelerator opening of host vehicle 1, and a brake sensor that detects the amount of brake operation by the driver.

[0012] 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 also be, for example, an inertial navigation system. The map database 14 may store high-precision map data (hereinafter simply referred to as "high-precision map") suitable as a map for automated driving. The high-precision map is map data with higher precision than map data for navigation (hereinafter simply referred to as "navigation map"), and includes more detailed information on a lane-by-lane basis than on a road-by-road basis. The navigation device 15 recognizes the current position of the vehicle 1 using the positioning device 13, etc. The navigation device 15 acquires road information and traffic information around the vehicle 1 based on the recognized current position, and outputs the information to the controller 17. The navigation device 15 also provides route guidance to the occupant, and road and traffic information.

[0013] The controller 17 is an electronic control unit (ECU) that includes a processor and peripheral components such as a storage device, and performs driving assistance control of the host vehicle 1. The processor may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit). The storage device may include a semiconductor storage device, a magnetic storage device, an optical storage device, etc. The storage device may include a register, a cache memory, a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory) used as a main memory device. The processor of the controller 17 executes a computer program stored in the storage device, causing the controller 17 to function as an automatic driving control unit 20, an input arbitration unit 21, and a vehicle control unit 22. These functions will be described later.

[0014] The controller 17 may be formed by dedicated hardware for executing each of the information processes described below. For example, the controller may include functional logic circuits configured in a general-purpose semiconductor integrated circuit, such as a programmable logic device (PLD) such as a field-programmable gate array (FPGA).

[0015] The actuator 18 operates the steering device, drive device, and braking device of the host vehicle 1 in response to a control signal from the controller 17 to generate vehicle behavior of the host vehicle 1. The actuator 18 includes a steering actuator, an accelerator opening actuator, and a brake control actuator. When the host vehicle 1 is a front-wheel steering vehicle, the steering actuator controls the front wheel steering angle δ F When the host vehicle 1 is a four-wheel steering vehicle, the steering actuator controls the front wheel steering angle δ F In addition, the rear wheel steering angle δ R Control.

[0016] The steering actuator may be, for example, a steering assist motor that applies a steering assist force in an electric power steering system, or a steering motor that steers the wheels 2 in a steering-by-wire system in which the steering wheel and the wheels 2 are mechanically separated. The accelerator opening actuator controls the accelerator opening of a drive device (for example, an engine or an electric motor) that is a power source that generates driving force for the host vehicle 1. The brake control actuator controls the braking operation of the host vehicle 1's brake device. The combination of the drive device, the brake device, the controller 17 and the actuator 18 is an example of a "speed control device" as defined in the claims.

[0017] Next, an example of driving support control by the driving support device 10 of the embodiment will be described. Fig. 2 shows an example of architecture of autonomous driving control by the driving support device. The autonomous driving control is performed by an autonomous driving layer (AD Layer) 30, an arbitration unit (Arbitration) 31, a reference model unit (Reference Model) 32, a body motion control unit (Body Motion Control) 33, a wheel motion control unit (Wheel Motion Control) 34, and the above-mentioned actuator 18. The autonomous driving layer 30 sets a destination for the vehicle 1 and sets a driving route from the current position of the vehicle 1 to the destination. The destination may be a final destination set by the driver, or may be a point a predetermined distance ahead of the current position of the vehicle 1 (for example, the center position of the lane a predetermined distance ahead on the lane in which the vehicle is traveling). The autonomous driving layer 30 generates a target driving trajectory of the vehicle 1 traveling along a driving route, i.e., a driving trajectory on the road from the current position of the vehicle 1 to the destination, as an autonomous driving input (AD input), which is an instruction input from the autonomous driving layer 30.

[0018] The arbitration unit 31 arbitrates between manual driving input (MD input) which is input by the driver to operate the steering wheel, accelerator, and brake, and automatic driving input from the automatic driving layer 30, and sets the vehicle motion that the host vehicle 1 should perform. The normative model unit 32 sets the parameters of the vehicle motion model (e.g., yaw moment of inertia, cornering stiffness of the wheels 2, etc.) used to calculate the body behavior of the host vehicle 1 so that the host vehicle 1 realizes the vehicle motion set by the arbitration unit 31. The vehicle body behavior control unit 33 calculates the vehicle body behavior (e.g., vehicle speed, acceleration / deceleration, yaw rate, yaw angular acceleration, yaw moment, etc.) to realize the vehicle motion set by the arbitration unit 31 based on the vehicle motion model set by the normative model unit 32.

[0019] The wheel behavior control unit 34 calculates the control amount (steering angle, braking amount, driving amount, etc.) of the wheel 2 to cause the vehicle 1 to produce the vehicle body behavior calculated by the vehicle body behavior control unit 33, and controls the wheel behavior using the actuator 18. For example, the functions of the autonomous driving layer 30 may be performed by the autonomous driving control unit 20 shown in Figure 1, the functions of the arbitration unit 31 may be performed by the input arbitration unit 21, and the functions of the normative model unit 32, the vehicle body behavior control unit 33, and the wheel behavior control unit 34 may be performed by the vehicle control unit 22.

[0020] Next, an example of the functional configuration of the autonomous driving control unit 20 will be described with reference to Fig. 3. The autonomous driving control unit 20 includes a localization unit 40, a destination setting unit 41, a route planning unit 42, a decision making unit 43, a drive zone planning unit 44, and a trajectory generation unit 45.

[0021] The localization unit 40 recognizes the surrounding environment of the vehicle 1 based on the detection signal of the object sensor 11. The localization unit 40 determines the current position of the vehicle 1 on the high-precision map by map matching between the recognition result and the high-precision map in the map database 14. Furthermore, based on the recognition result of the surrounding environment, a local model 47 is generated, which is a model of the surrounding environment of the vehicle 1. Furthermore, a world model 46 is generated by combining the local model 47 with the high-precision map and road information and traffic information from the navigation device 15.

[0022] The destination setting unit 41 sets the destination of the vehicle 1 based on an operational input by the driver via the navigation device 15. The route planning unit 42 calculates a planned driving route from the current position to the destination based on road information from the navigation device 15. Note that the planned driving route is not limited to this, and may be, for example, a planned route from the current position to a predetermined distance ahead of the vehicle. Alternatively, without using road information from the navigation device 15, the planned route from the predetermined distance ahead of the vehicle may be detected from an image captured by a camera or the like of the area ahead of the vehicle. The behavior decision unit 43 decides a driving behavior plan for the vehicle 1 to be executed by the driving assistance device 10 based on the recognition result of the surrounding environment, the current position of the vehicle 1, the world model 46, and the planned driving route.

[0023] Driving actions include, for example, stopping the vehicle 1, stopping temporarily, adjusting driving speed, slowing down, accelerating, changing lanes, turning right, turning left, going straight, changing lanes in merging sections or on multiple lanes, staying in lane, overtaking, and dealing with obstacles. The behavior decision unit 43 generates a driving behavior plan for the host vehicle 1 based on the current position and attitude of the host vehicle 1, the surrounding environment of the host vehicle 1, and the world model .

[0024] The driving zone planning unit 44 calculates a driving zone, which is an area in which the host vehicle 1 can travel, based on the generated driving action plan, the motion characteristics of the host vehicle 1, and the local model 47. The trajectory generation unit 45 generates a target driving trajectory for the host vehicle 1 so that the host vehicle 1 travels within the driving zone calculated by the driving zone planning unit 44 .

[0025] See Fig. 1. The input arbitration unit 21 arbitrates between the automatic driving input of the target driving trajectory set by the automatic driving control unit 20 and the manual driving input by the driver, and sets the vehicle motion that the host vehicle 1 should perform. The vehicle control unit 22 controls the behavior of the host vehicle 1 so as to realize the vehicle motion set by the input arbitration unit 21 .

[0026] Next, a description will be given of vehicle speed control by the vehicle control unit 22. In order for the host vehicle 1 to travel along a target travel trajectory, it is necessary to set a target vehicle speed so that the frictional force of the wheels 2 due to the lateral acceleration at the center of gravity of the host vehicle 1 does not exceed the friction limit. Furthermore, since the magnitude of the friction limit of the front wheels 2F and the friction limit of the rear wheels 2R change depending on the load fluctuations that accompany the acceleration and deceleration of the vehicle 1, it is necessary to set the target vehicle speed so that the friction forces generated on the front wheels 2F and the rear wheels 2R do not exceed the friction limits of the front wheels 2F and the rear wheels 2R, respectively. For example, in a driving scene where the vehicle turns while decelerating, a large braking force is generated on the front wheels 2F, and a large lateral force is generated on the front wheels 2F to turn the vehicle. This makes it easy for the frictional force of the front wheels 2F to saturate, which may result in a decrease in the vehicle's ability to follow the target driving trajectory.

[0027] Therefore, the vehicle control unit 22 limits the target vehicle speed so that the resultant force of the braking force and lateral force of each of the front wheels 2F and rear wheels 2R and the resultant force of the driving force and lateral force of each of the front wheels 2F and rear wheels 2R do not exceed the friction limit. This allows the target vehicle speed to be set so that the frictional force of the front wheels 2F and the frictional force of the rear wheels 2R do not exceed the friction limit, improving the ability to follow the target driving trajectory.

[0028] Furthermore, as described above, the yaw motion of a vehicle has a resonance frequency, and if the frequency of the yaw rate of the host vehicle 1 approaches the resonance frequency, the vehicle behavior may become unstable. Here, the yaw rate γ when turning at a certain point on the target travel trajectory can be expressed as γ = ρV, where V is the vehicle speed of the host vehicle 1 and ρ is the turning curvature. Therefore, the time change in yaw rate γ, γ' = (dρ / dt)V + ρ(dV / dt), is expressed as γ' = ρ'V, where Ax is the acceleration / deceleration in the traveling direction (i.e., the longitudinal direction) of the host vehicle 1 and ρ' is the change in turning curvature per unit distance. 2 It can be expressed as +ρAx. That is, the frequency of the yaw rate changes not only with the amount of change in curvature but also with the acceleration / deceleration Ax in the direction of travel. Therefore, there is a risk that the vehicle behavior may become unstable not only in driving situations where the curvature changes significantly, such as at the entrance to a curved road or an S-shaped curve, but also in situations where strong acceleration or deceleration occurs during cornering even when the curvature changes only slightly. Therefore, in addition to the above-mentioned restriction based on the friction limit, the vehicle control unit 22 restricts the target vehicle speed so that the frequency of the yaw rate of the host vehicle 1 is less than the resonance frequency.

[0029] Fig. 4 is a block diagram showing an example of the functional configuration of vehicle control unit 22 shown in Fig. 1. Vehicle control unit 22 includes a geometric calculation unit 50, a backward calculation unit 51, and a forward calculation unit 52. The geometric calculation unit 50 calculates the turning curvature ρ of the target traveling trajectory generated by the trajectory generation unit 45 in FIG. 3 and the maximum lateral acceleration setting value A that is preset as the maximum allowable lateral acceleration. yMax and a maximum yaw rate setting value γ Max Based on this, the lateral acceleration of the center of gravity of the host vehicle 1 is set to the maximum lateral acceleration setting value A yMax and the yaw rate of the host vehicle 1 does not exceed the maximum yaw rate setting value γ Max , so as not to exceed the target vehicle speed of the host vehicle. in Calculate. For example, the turning curvature at point i on the target driving trajectory is ρ i Then, the geometric calculation unit 50 calculates the target vehicle speed V at point i based on the following equation (1): i may be set.

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[0030] Figure 5(a) shows the first vehicle speed profile V in In the figure, the horizontal axis indicates the travel distance from the current position of the vehicle 1 to each point ahead of the vehicle on the target travel path, and the vertical axis indicates the target vehicle speed at each point. The leftmost point on the horizontal axis of FIG. 5(a) is the current position of the vehicle 1, and the rightmost point is the first vehicle speed profile V in is the point on the generated target driving trajectory that is the farthest from the vehicle 1 (hereinafter referred to as the "farthest point"). The same applies to Figures 5(b) and 5(c).

[0031] See Fig. 4. At each point on the target driving trajectory, the backward calculation unit 51 calculates the maximum backward speed based on the loads acting on the front wheels 2F and rear wheels 2R in accordance with the deceleration of the vehicle 1, so that the resultant force of the braking force and the lateral force on the front wheels 2F and rear wheels 2R does not exceed the friction limit. Furthermore, the backward calculation unit 51 calculates the maximum backward speed based on the vehicle speed, turning curvature, and changes in that curvature so that the frequency of the yaw rate of the vehicle 1 is less than the resonance frequency. The backward calculation unit 51 calculates the first vehicle speed profile V in By limiting the maximum backward speed, the second vehicle speed profile V B Set. Figure 5(b) shows the second vehicle speed profile V B An example is shown below.

[0032] Here, the first vehicle speed profile V at point i is limited by the friction limit. in Target vehicle speed V in From (i), the target vehicle speed V at the forward point (i+1) in If the vehicle speed cannot be reduced to (i+1), the first vehicle speed profile V in If this is exceeded, the vehicle will no longer be able to travel along the target travel trajectory. Therefore, the backward calculation unit 51 calculates the target vehicle speed V at a point (i+1) ahead of the target point i. in (i+1), the target vehicle speed V at the point of interest i is calculated.in Limit (i). Specifically, the target vehicle speed V at point (i+1) in (i+1) and the turning curvature ρ(i+1), the maximum deceleration A allowed for the host vehicle 1 at the point (i+1) x Calculate (i+1). And the maximum deceleration A at point (i+1) x Based on the loads applied to the front wheels 2F and rear wheels 2R according to (i+1), the maximum speed is calculated as the backward maximum speed assuming that the resultant force of the braking force and lateral force of the front wheels 2F and rear wheels 2R at the point of interest i does not exceed the friction limit. At this time, the target vehicle speed V at point (i+1) in (i+1), the turning curvature ρ(i+1), and the curvature change ρ'(i+1) are used to calculate the maximum backward speed so that the frequency of the yaw rate of the host vehicle 1 is less than the resonance frequency. Then, the first vehicle speed profile V at the target point i is calculated. in The target vehicle speed is limited by the maximum backward speed. This calculation is repeated while moving the attention point i backward one step at a time from the farthest point toward the current position of the host vehicle 1.

[0033] See Fig. 4. The forward calculation unit 52 calculates the maximum forward speed at each point on the target driving trajectory based on the loads acting on the front wheels 2F and rear wheels 2R in accordance with the acceleration of the vehicle 1, so that the resultant force of the driving force and lateral force on each of the front wheels 2F and rear wheels 2R does not exceed the friction limit. The forward calculation unit 52 calculates the maximum forward speed based on the vehicle speed, turning curvature, and changes in that curvature so that the frequency of the yaw rate of the vehicle 1 is less than the resonance frequency. The forward calculation unit 52 calculates the second vehicle speed profile V B By limiting the forward speed to the maximum, the third vehicle speed profile V out Set. The vehicle control unit 22 determines the third vehicle speed profile V out The speed of the host vehicle 1 is controlled by driving the accelerator opening actuator and the brake control actuator of the actuator 18 based on the above.

[0034] Contrary to the backward calculation unit 51, the forward calculation unit 52 calculates the target vehicle speed V at a point (i-1) one position behind the target vehicle 1, while moving the target point i forward one position at a time from the current position of the vehicle 1 toward the farthest point. in (i-1) and the turning curvature ρ(i-1), the maximum acceleration A allowed for the host vehicle 1 at the point (i-1) x Calculate (i-1). And the maximum acceleration A at point (i-1) x Based on the loads on the front wheels 2F and the rear wheels 2R according to (i-1), the maximum forward speed is calculated as the maximum speed at which the resultant force of the driving force and the lateral force of the front wheels 2F and the rear wheels 2R at the point of interest i does not exceed the friction limit. At this time, the target vehicle speed V at point (i-1) in (i-1), the turning curvature ρ(i-1), and the curvature change ρ'(i-1) are used to calculate the maximum forward speed so that the frequency of the yaw rate of the host vehicle 1 is less than the resonance frequency. Then, the second vehicle speed profile V at the target point i is calculated. B The target vehicle speed is limited to the maximum forward speed. This calculation is repeated while moving the attention point i forward one step at a time from the current position of the host vehicle 1 toward the farthest point.

[0035] In the examples of FIG. 4 and FIG. 5(a) to FIG. 5(c), the backward calculation unit 51 calculates the first vehicle speed profile V in By limiting the second vehicle speed profile V B is set, and the forward calculation unit 52 calculates the second vehicle speed profile V B By limiting the third vehicle speed profile V out Instead, the forward calculation unit 52 calculates the first vehicle speed profile V in The second vehicle speed profile V B The backward calculation unit 51 sets the second vehicle speed profile V B The third vehicle speed profile V out may be set.

[0036] Next, a detailed description will be given of the backward calculation unit 51 and the forward calculation unit 52. FIG. The backward calculation unit 51 sets a point one position behind the farthest point as the first attention point i, and calculates the maximum deceleration A at the attention point i while sequentially moving the attention point i backward one position at a time to the current position of the vehicle 1. x (i) and target vehicle speed V Tar (i) is calculated respectively. The backward calculation unit 51 includes a maximum speed calculation unit 51a, selectors 51b, 51k, and 51n, a load calculation unit 51c, a target lateral force calculation unit 51d, a maximum lateral force calculation unit 51e, a target longitudinal force calculation unit 51h, a maximum longitudinal force calculation unit 51i, a first maximum acceleration / deceleration calculation unit 51j, and a second maximum acceleration / deceleration calculation unit 51m.

[0037] In the calculation at the first point of interest i, the maximum speed calculation unit 51a calculates the target vehicle speed V at the point (i+1) immediately before the point of interest i. Tar (i+1), the first vehicle speed profile V in Set the target vehicle speed and the maximum deceleration A at point (i+1). x (i+1) is the maximum allowable deceleration preset value A xMax Set. In the calculation at the second or subsequent point of interest i, the target vehicle speed V calculated at the previous point of interest (i.e., point (i+1)) is used. Tar (i+1) and maximum deceleration A x Enter (i+1). The maximum speed calculation unit 51a calculates the target vehicle speed V at the previous point (i+1). Tar (i+1) and maximum deceleration A x The speed limit value of the following equation (2) is set according to (i+1).

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[0038] The selector 51b selects the first vehicle speed profile V at the point of interest i.in Target vehicle speed V in (i) according to the following equation (3), the target vehicle speed V Tar Set (i).

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[0039] The load calculation unit 51c calculates the maximum deceleration A at the point (i+1) immediately ahead based on the following equations (4) and (5): x (i+1), the front wheel load Fz, which is the load on the front wheel 2F based on the pitch motion of the body of the host vehicle 1. F (i) and the rear wheel load Fz, which is the load on the rear wheel 2R R Calculate (i).

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[0040] The target lateral force calculation unit 51d calculates the target vehicle speed V at the target point i based on the following equations (6) and (7): Tar (i) and the turning curvature ρ(i) of the target running trajectory, the target front wheel lateral force Fy ReqF (i) and the target rear wheel lateral force Fy ReqR (i) is calculated respectively.

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[0041] The maximum lateral force calculation unit 51e calculates the front wheel load Fz based on the following equations (8) and (9). F (i) and rear wheel load Fz R (i) and the target vehicle speed V Tar (i) and the maximum lateral acceleration setting value A yMax and a maximum yaw rate setting value γ Max Based on this, the maximum front wheel lateral force Fy is the maximum lateral force that can be generated on the front wheel 2F. MaxF (i) and the maximum rear wheel lateral force Fy, which is the maximum lateral force that can be generated on the rear wheel 2R. MaxR (i) is calculated respectively.

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[0042] The target longitudinal force calculation unit 51h calculates the maximum deceleration setting value Ax based on the following equation (10): Max and the front wheel target lateral force Fy ReqF (i) and the rear wheel target lateral force Fy ReqR (i) and the maximum front wheel lateral force Fy MaxF (i) and the maximum rear wheel lateral force Fy MaxR (i) A target longitudinal force Fx to be generated in the host vehicle 1 Req Calculate (i).

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[0043] The target longitudinal force calculation unit 51h calculates the target longitudinal force Fx based on the following equations (11) and (12): Req (i) is the brake distribution ratio κ of the front wheel 2F and the rear wheel 2R F :(1-κ F ) based on the target longitudinal force Fx of the front wheels, which is the target longitudinal force to be generated on the front wheels 2F. ReqF (i) and the target rear wheel longitudinal force Fx, which is the target lateral force to be generated on the rear wheel 2R. ReqR (i) is calculated respectively.

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[0044] The maximum longitudinal force calculation unit 51i calculates the front wheel load Fz F (i) and rear wheel load Fz R (i) The friction circles of the front wheel 2F and the rear wheel 2R according to (i) and the maximum lateral force Fy MaxF (i) and the maximum rear wheel lateral force Fy MaxR Based on (i), the maximum longitudinal force that can be generated on the front wheel 2F is the maximum longitudinal force Fx MaxF (i) and the maximum rear wheel longitudinal force Fx, which is the maximum longitudinal force that can be generated on the rear wheel 2R. MaxR (i) and (ii) are calculated respectively. Specifically, the maximum longitudinal force calculation unit 51i calculates the front wheel maximum longitudinal force Fx based on the following equations (13) and (14): MaxF (i) and maximum rear wheel longitudinal force Fx MaxR Calculate (i).

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[0045] The first maximum acceleration / deceleration calculation unit 51j calculates the front wheel target longitudinal force Fx ReqF (i) and maximum front wheel longitudinal force Fx MaxF (i) The smallest value min(Fx ReqF (i),Fx MaxF (i)) and the rear wheel target longitudinal force Fx ReqR (i) and maximum rear wheel longitudinal force Fx MaxR (i) The smallest value min(Fx ReqR (i),Fx MaxR (i)) and the ratio of the target lateral force to the maximum lateral force Fy ReqF (i) / Fy MaxF (i), Fy ReqR (i) / Fy MaxR (i) respectively, and the sum of these is the maximum longitudinal force Fx at which the frictional force of the front wheel 2F and the rear wheel 2R does not exceed the friction limit. Max (i) (the following formula (15)).

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[0046] The second maximum acceleration / deceleration calculation unit 51m calculates the target vehicle speed V TarBased on (i), the turning curvature ρ(i), and the curvature change ρ'(i), the maximum deceleration at which the frequency of the yaw rate of the vehicle 1 becomes lower than the resonance frequency is calculated as the second maximum deceleration Ax2(i). Specifically, the second maximum acceleration / deceleration calculation unit 51m calculates the resonance frequency ω of the yaw rate of the host vehicle 1 based on the following equation (16) using the motion characteristic value of the host vehicle 1: n Calculate.

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[0047] The second maximum acceleration / deceleration calculation unit 51m calculates the target vehicle speed V Tar (i), turning curvature ρ(i), and maximum yaw rate setting value γ Max Based on this, the maximum yaw rate change amount γ', which is the upper limit of the yaw rate change amount (i.e., yaw acceleration) occurring in the host vehicle 1, is calculated according to the following equation (17): Max Calculate.

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[0048] The second maximum acceleration / deceleration calculation unit 51m calculates the maximum lateral jerk Jy, which is the upper limit of the lateral jerk that occurs in the host vehicle 1. Max In this case, the second maximum acceleration / deceleration calculation unit 51m may calculate the second maximum deceleration Ax2(i) based on the target vehicle speed V Tar (i), turning curvature ρ(i), and maximum lateral acceleration setting value A yMax Based on this, the maximum lateral jerk Jy is calculated according to the following equation (19): Max Calculate.

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[0049] The selector 51n selects the smaller of the maximum deceleration candidate Axc output from the selector 51k and the second maximum deceleration Ax2(i) as the maximum deceleration A at the point of interest i. x The calculated value (i) is output to the maximum speed calculation unit 51a and the load calculation unit 51c. This completes the calculation for the target point i. Then, when the target point i is moved backward by one and calculation for the next target point i is started, the maximum deceleration A calculated at the previous target point (i.e., point (i+1)) is x (i+1) is the target vehicle speed V at the new target point i Tar (i) and maximum deceleration A x Used in the calculation of (i).

[0050] FIG. 7 is a block diagram showing an example of the functional configuration of the forward calculation unit 52. As shown in FIG. The forward calculation unit 52 sets a point one position ahead of the current position of the vehicle 1 as the first point of interest i, and calculates the maximum acceleration A at the point of interest i while sequentially moving the point of interest i forward one position at a time until it reaches the farthest point. x (i) and target vehicle speed V Tar (i) is calculated respectively. The forward calculation unit 52 includes a maximum speed calculation unit 52a, selectors 52b, 52k, and 52n, a load calculation unit 52c, a target lateral force calculation unit 52d, a maximum lateral force calculation unit 52e, a target longitudinal force calculation unit 52h, a maximum longitudinal force calculation unit 52i, a first maximum acceleration / deceleration calculation unit 52j, and a second maximum acceleration / deceleration calculation unit 52m.

[0051] In the calculation at the first point of interest i, the maximum speed calculation unit 52a calculates the target vehicle speed V at the point (i-1) immediately after the point of interest i. Tar (i-1) is the first vehicle speed profile V in Set the target vehicle speed and the maximum acceleration A at point (i-1). x (i-1) is the maximum allowable acceleration preset value A xMax Set. In the calculation at the second or subsequent point of interest i, the target vehicle speed V calculated at the previous point (i.e., point (i-1)) is used. Tar (i-1) and maximum acceleration A x Enter (i-1). The maximum speed calculation unit 52a calculates the target vehicle speed V at the previous point (i-1). Tar (i-1) and maximum acceleration A x The speed limit value of the following equation (21) is set according to (i-1).

number

[0052] The selector 52b selects the first vehicle speed profile V at the point of interest i. in Target vehicle speed V in (i) according to the following equation (22), the target vehicle speed V TarSet (i).

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[0053] The load calculation unit 52c calculates the maximum acceleration A at the point (i-1) immediately before based on the following equations (23) and (24): x In response to (i-1), a front wheel load Fz, which is the load on the front wheel 2F based on the pitch motion of the body of the host vehicle 1, is calculated. F (i) and the rear wheel load Fz, which is the load on the rear wheel 2R R Calculate (i).

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[0054] The functions of the target lateral force calculation section 52d, maximum lateral force calculation section 52e, target longitudinal force calculation section 52h, maximum longitudinal force calculation section 52i, first maximum acceleration / deceleration calculation section 52j, selector 52k, second maximum acceleration / deceleration calculation section 52m, and selector 52n of the forward calculation section 52 are similar to the functions of the target lateral force calculation section 51d, maximum lateral force calculation section 51e, target longitudinal force calculation section 51h, maximum longitudinal force calculation section 51i, first maximum acceleration / deceleration calculation section 51j, selector 51k, second maximum acceleration / deceleration calculation section 51m, and selector 51n of the backward calculation section 51. However, the "maximum deceleration A" in the description of the backward calculation section 51 is omitted. x ”, “1st maximum deceleration A x 1", "2nd maximum deceleration A x 2", "Maximum deceleration candidate Axc", "Maximum deceleration setting value A xMax " and "Brake distribution ratio" are set to "Maximum acceleration A x ”, “1st maximum acceleration A x 1", "2nd maximum acceleration A x 2", "Maximum acceleration candidate Axc", "Maximum acceleration setting value A xMax "," "driving force distribution ratio."

[0055] (operation) 8 is an explanatory diagram of an example of a vehicle speed control method according to an embodiment. In step S1, the geometric calculation unit 50 calculates a first vehicle speed profile V, which is a profile of a target vehicle speed of the host vehicle 1. in Calculate. In step S2, the backward calculation unit 51 calculates the first vehicle speed profile V so that the friction limit is not exceeded during deceleration and the yaw rate frequency of the host vehicle 1 is less than the resonance frequency. in By limiting the second vehicle speed profile V B Set. Fig. 9 is a flowchart of an example of the process of step S2 in Fig. 8. Here, the process of steps S10 to S18 is repeated while moving the attention point i backward one step at a time from the point immediately behind the farthest point toward the current position of the vehicle 1.

[0056] In step S10, the maximum speed calculation unit 51a and the selector 51b calculate the maximum deceleration A at the point (i+1) immediately before the target point i. x (i+1) based on the first vehicle speed profile V at the point of interest i in Target vehicle speed V in (i) is limited to the second vehicle speed profile V B Target vehicle speed V B Calculate (i). In step S11, the target lateral force calculation unit 51d calculates the front wheel target lateral force Fy ReqF (i) and rear wheel target lateral force Fy ReqR Calculate (i).

[0057] In step S12, the maximum lateral force calculation unit 51e calculates the front wheel maximum lateral force Fy MaxF (i) and maximum rear wheel lateral force Fy MaxR Calculate (i). In step S13, the target longitudinal force calculation unit 51h calculates the front wheel target longitudinal force Fx ReqF (i) and rear wheel target longitudinal force Fx ReqR Calculate (i). In step S14, the maximum longitudinal force calculation unit 51i calculates the front wheel maximum longitudinal force Fx MaxF (i) and maximum rear wheel longitudinal force Fx MaxR (i) and (ii) are calculated respectively.

[0058] In step S15, the first maximum acceleration / deceleration calculation unit 51j calculates the maximum front wheel longitudinal force Fx MaxF (i), Rear wheel maximum longitudinal force Fx MaxR (i) Front wheel target longitudinal force Fx ReqF (i) Rear wheel target longitudinal force Fx ReqR (i) is limited, and the maximum longitudinal force Fx that can be generated on the vehicle 1 without the frictional force of the front wheel 2F and the rear wheel 2R exceeding the friction limit is calculated. Max The first maximum acceleration / deceleration calculation unit 51j calculates the maximum longitudinal force Fx Max First maximum deceleration Ax1(i)=Fx caused by (i) Max Calculate (i) / m. In step S16, the selector 51k selects the first maximum deceleration Ax1(i) and the maximum deceleration setting value A xMax The smaller of these is selected as the maximum deceleration candidate Axc. In step S17, the second maximum acceleration / deceleration calculation unit 51m calculates the maximum deceleration at which the frequency of the yaw rate of the host vehicle 1 becomes lower than the resonance frequency as the second maximum deceleration Ax2(i). In step S18, the selector 51n selects the smaller of the second maximum deceleration Ax2(i) and the maximum deceleration candidate Axc as the maximum deceleration Ax2(i). x Select as (i). When the above steps S10 to S18 are repeated until the target point i reaches the current position of the vehicle 1, the process then proceeds to step S3 in FIG.

[0059] 8, in step S3, the forward calculation unit 52 calculates the second vehicle speed profile V so that the friction limit is not exceeded during acceleration and the yaw rate frequency of the host vehicle 1 is less than the resonance frequency. B By limiting the third vehicle speed profile V out Set. The processing of the forward calculation unit 52 is similar to the processing of the backward calculation unit 51 in step S2, except for the following points (1) and (2). (1) The target point i is moved forward one point at a time from the point one point ahead of the current position of the vehicle 1 to the farthest point. (2) "Maximum deceleration A x ”, “1st maximum deceleration A x 1", "2nd maximum deceleration A x 2", "Maximum deceleration candidate Axc", "Maximum deceleration setting value A xMax " and "Brake distribution ratio" are set to "Maximum acceleration A x ”, “1st maximum acceleration A x 1", "2nd maximum acceleration A x 2", "Maximum acceleration candidate Axc", "Maximum acceleration setting value A xMax "," shall be read as "driving force distribution ratio." In step S4, the vehicle control unit 22 calculates the third vehicle speed profile V out The actuator 18 is driven based on this to control the speed of the host vehicle 1. Then, the process ends.

[0060] (Effects of the embodiment) (1) The controller 17 sets a target driving trajectory for the vehicle 1, calculates the resonance frequency of the yaw rate of the vehicle 1 based on the motion characteristic values ​​of the vehicle 1, sets a target vehicle speed at which the vehicle 1 will travel on the target driving trajectory so that the frequency of the yaw rate while the vehicle 1 is traveling on the target driving trajectory is less than the resonance frequency, and controls the vehicle speed of the vehicle 1 based on the target vehicle speed. This allows the target vehicle speed to be set so that the yaw rate frequency of the host vehicle 1 traveling on the target traveling trajectory does not exceed the resonance frequency, thereby preventing the behavior of the host vehicle 1 from becoming unstable due to the yaw rate frequency.

[0061] (2) The controller 17 may set a first vehicle speed profile, which is a profile of the target vehicle speed of the host vehicle 1, so that the lateral acceleration of the center of gravity of the host vehicle 1 is below a predetermined value at each point on the target driving trajectory and the yaw rate of the host vehicle 1 is below a predetermined value at each point on the target driving trajectory, calculate the maximum speed when either the acceleration or the deceleration is limited so that the frequency of the yaw rate of the host vehicle 1 is less than the resonant frequency at each point as a first maximum speed, set a second vehicle speed profile by limiting the first maximum speed at each point, calculate the maximum speed when either the acceleration or the deceleration is limited so that the frequency of the yaw rate of the host vehicle 1 is less than the resonant frequency at each point as a second maximum speed, set a third vehicle speed profile by limiting the second vehicle speed profile at each point, and control the vehicle speed of the host vehicle 1 based on the third vehicle speed profile. This allows the vehicle speed to be controlled so that it does not exceed both the deceleration and acceleration allowable for the host vehicle.

[0062] (3) The controller 17 may designate one of the points on the target driving trajectory, one closer to the vehicle 1 or one farther away from the vehicle 1, as a first point, and the other as a second point, and calculate the maximum yaw rate change allowable for the vehicle 1 at the first point based on the curvature at the first point, the target speed of the vehicle 1 at the first point, a predetermined maximum allowable yaw rate, and the resonant frequency, calculate the maximum acceleration / deceleration at which the yaw rate change of the vehicle 1 is less than or equal to the maximum yaw rate change, and set the target vehicle speed at the second point based on the maximum acceleration / deceleration. In this case, the controller 17 may calculate the maximum yaw rate change amount based on the curvature at the first point, the target speed of the vehicle 1 at the first point, the maximum allowable yaw rate, and the product of the resonant frequency and a gain less than 1. Then, the maximum acceleration / deceleration may be calculated based on the maximum yaw rate change amount, the curvature and curvature change at the first point, and the target speed of the host vehicle 1 at the first point. This allows the maximum yaw rate change amount at which the frequency of the yaw rate of the host vehicle 1 becomes less than the resonance frequency to be calculated, and the target vehicle speed to be set by limiting the maximum acceleration / deceleration based on the maximum yaw rate change amount.

[0063] (4) The controller 17 may designate one of the points on the target driving trajectory, one closer to the vehicle 1 or one farther away from the vehicle 1, as a first point, and the other as a second point, and calculate the maximum lateral jerk allowable for the vehicle 1 at the first point based on the curvature at the first point, the target speed of the vehicle 1 at the first point, a predetermined maximum allowable lateral acceleration, and the resonance frequency, calculate the maximum acceleration / deceleration at which the lateral jerk of the vehicle 1 is equal to or less than the maximum lateral jerk, and set the target vehicle speed at the second point based on the maximum acceleration / deceleration. In this case, the controller 17 may calculate the maximum lateral jerk based on the curvature at the first point, the target speed of the vehicle 1 at the first point, the maximum allowable lateral acceleration, and the product of the resonance frequency and a gain less than 1. Then, the maximum acceleration / deceleration may be calculated based on the maximum lateral jerk, the curvature and curvature change at the first point, and the target speed of the host vehicle 1 at the first point. This allows the maximum lateral jerk at which the frequency of the yaw rate of the host vehicle 1 is less than the resonance frequency to be calculated, and the target vehicle speed to be set by limiting the maximum acceleration / deceleration based on the maximum lateral jerk. [Explanation of symbols]

[0064] 22...vehicle control unit, 50...geometric calculation unit, 51...backward calculation unit, 51a, 522a...maximum speed calculation unit, 51b, 51k, 51n, 52b, 52k, 52n...selector, 51c, 52c...load calculation unit, 51d, 52d...target lateral force calculation unit, 51e, 52e...maximum lateral force calculation unit, 51f, 52f...maximum steering angle calculation unit, 51g, 52g...maximum lateral force limiting unit, 51h, 52h...target longitudinal force calculation unit, 51i, 52i...maximum longitudinal force calculation unit, 51j, 52j...first maximum acceleration / deceleration calculation unit, 51m, 52m...second maximum acceleration / deceleration calculation unit

Claims

1. Set a target driving trajectory for the vehicle, calculating a resonance frequency of a yaw rate of the host vehicle based on the motion characteristic value of the host vehicle; setting a target vehicle speed at which the host vehicle travels on the target travel path so that a frequency of a yaw rate while the host vehicle is traveling on the target travel path is less than the resonance frequency; controlling the vehicle speed of the host vehicle based on the target vehicle speed; A vehicle speed control method comprising:

2. setting a first vehicle speed profile, which is a profile of a target vehicle speed of the host vehicle, so that the lateral acceleration of the center of gravity of the host vehicle is equal to or less than a predetermined value at each point on the target traveling trajectory and the yaw rate of the host vehicle is equal to or less than a predetermined value at each point on the target traveling trajectory; calculating, at each of the points, a maximum speed when either acceleration or deceleration is limited so that a frequency of a yaw rate of the host vehicle is less than the resonance frequency, as a first maximum speed; establishing a second vehicle speed profile by limiting the first vehicle speed profile at the first maximum speed at each of the locations; calculating, at each of the points, a maximum speed when either the acceleration or the deceleration is limited so that the frequency of the yaw rate of the host vehicle is less than the resonance frequency, as a second maximum speed; establishing a third vehicle speed profile by limiting the second vehicle speed profile at the second maximum speed at each of the locations; controlling the vehicle speed of the host vehicle based on the third vehicle speed profile; 2. The vehicle speed control method according to claim 1.

3. one of the points on the target traveling trajectory that is closer to the host vehicle and the other that is farther from the host vehicle is designated as a first point, and the other is designated as a second point, and a maximum yaw rate change amount that is allowable for the host vehicle at the first point is calculated based on the curvature at the first point, the target speed of the host vehicle at the first point, a predetermined maximum allowable yaw rate, and the resonance frequency; calculating a maximum acceleration / deceleration at which a yaw rate change amount of the host vehicle is equal to or less than the maximum yaw rate change amount; setting the target vehicle speed at the second location based on the maximum acceleration / deceleration; 3. The vehicle speed control method according to claim 2.

4. 4. The vehicle speed control method according to claim 3, wherein the maximum acceleration / deceleration is calculated based on the maximum yaw rate change, the curvature and curvature change at the first point, and the target speed of the vehicle at the first point.

5. 5. The vehicle speed control method according to claim 3, wherein the maximum yaw rate change amount is calculated based on the curvature at the first point, the target speed of the vehicle at the first point, the maximum allowable yaw rate, and the product of the resonance frequency and a gain less than 1.

6. one of a point closer to the host vehicle and a point farther from the host vehicle among the points on the target traveling trajectory is designated as a first point, and the other point is designated as a second point, and a maximum lateral jerk allowable for the host vehicle at the first point is calculated based on the curvature at the first point, the target speed of the host vehicle at the first point, a predetermined maximum allowable lateral acceleration, and the resonance frequency; calculating a maximum acceleration / deceleration at which the lateral jerk of the host vehicle is equal to or less than the maximum lateral jerk; setting the target vehicle speed at the second location based on the maximum acceleration / deceleration; 3. The vehicle speed control method according to claim 2.

7. 7. The vehicle speed control method according to claim 6, wherein the maximum acceleration / deceleration is calculated based on the maximum lateral jerk, the curvature and curvature change at the first point, and a target speed of the host vehicle at the first point.

8. 8. The vehicle speed control method according to claim 6, wherein the maximum lateral jerk is calculated based on a curvature at the first point, a target speed of the host vehicle at the first point, the maximum allowable lateral acceleration, and a product of the resonance frequency and a gain less than 1.

9. a drive device that generates a drive force for the host vehicle; a braking device that generates a braking force for the host vehicle; a controller that sets a target running trajectory of the host vehicle, calculates a resonance frequency of a yaw rate of the host vehicle based on a motion characteristic value of the host vehicle, sets a target vehicle speed at which the host vehicle runs on the target running trajectory so that a frequency of a yaw rate while the host vehicle is running on the target running trajectory is less than the resonance frequency, and controls at least one of the drive device or the braking device based on the target vehicle speed; A vehicle speed control device comprising:

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