Vehicle contorl method and control device

Abstract

Provided is a vehicle control method in which: a target deceleration or a target braking torque of a vehicle is set on the basis of the inter-vehicle distance to a preceding vehicle and the relative speed of the vehicle with respect to the preceding vehicle; the speed of change of the target deceleration or the speed of change of the target braking torque is restricted on the basis of the speed of change of an accelerator operation amount when vehicle accelerator operation is turned off from a state in which accelerator operation is being performed; and braking torque generated in the vehicle is set on the basis of the target deceleration or the target braking torque.

Description

Vehicle control method and control device

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

[0002] 2. Description of the Related Art A control device is known that controls the deceleration and braking force of a vehicle in accordance with the distance between the vehicle and a preceding vehicle (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2021-173464

[0004] The vehicle control device described in Patent Document 1 controls the vehicle's deceleration based on the vehicle speed and the distance and relative speed between the vehicle and the preceding vehicle. This results in significant fluctuations in deceleration in response to changes in these values, resulting in a poor ride. In contrast, if the rate of change in the target deceleration value is slowed to allow for smooth and comfortable driving, the start of deceleration when the accelerator pedal is released will be delayed, and a large braking force will need to be generated only after the distance between the vehicle and the preceding vehicle has decreased. This results in a poor ability to follow the preceding vehicle, making it difficult to achieve both comfortable driving and the ability to follow the preceding vehicle.

[0005] An object of the present invention is to provide a vehicle control method and control device that can achieve both smooth and comfortable driving performance and the ability to follow a preceding vehicle.

[0006] In one aspect of the present invention, the rate of change of the target deceleration or the target braking torque of the vehicle is limited based on the rate of change of the accelerator operation amount when the accelerator operation is released from a state in which the vehicle's accelerator is being operated, and the braking torque to be generated in the vehicle is set based on the target deceleration or the target braking torque.

[0007] It is a diagram showing a schematic configuration of a vehicle according to an embodiment. It is a control block diagram of a controller. It is a diagram showing the relationship between the vehicle speed of a preceding vehicle and an equilibrium inter-vehicle distance. It is a flowchart of control executed by a controller. It is a flowchart of limiting the rate of change of a correction torque. It is an example of a time chart of limiting the rate of change of a correction torque. It is a control block diagram of a controller according to a modified example.

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that, hereinafter, a driver's operation to request a driving or braking force using a driving or braking force requesting operation means such as an accelerator pedal will be referred to as an "accelerator operation," and the amount of operation will be referred to as an "accelerator operation amount." Furthermore, the term "driving or braking force" refers to a driving force and a braking force, and the term "driving or braking torque" refers to a driving torque and a braking torque. Driving force, braking force, driving torque, and braking torque are all physical quantities that take positive values. However, in a program that executes control, braking force is treated as a negative driving force, and braking torque is treated as a negative driving torque. Therefore, the driving force, braking force, driving torque, and braking torque are expressed by the positive and negative values ​​of the driving or braking force and braking or braking torque. Therefore, braking force and braking torque are sometimes described as negative values. Furthermore, deceleration is a physical quantity that takes a positive value, but for the same reason, deceleration is sometimes described as a negative value.

[0009] 1 is a diagram showing a schematic configuration of a vehicle 1. The vehicle 1 includes a braking / driving force generating device 2, a control device 3, and sensors 4, 5, and 6.

[0010] The braking / driving force generation device 2 includes an inverter 21, a battery 22, an electric motor 23, a reducer 24, wheels 25, and a brake mechanism 26. Based on a command input from the control device 3, the inverter 21 converts direct current input from the battery 22 into alternating current and outputs the alternating current to the electric motor 23. Based on a command input from the control device 3, the inverter 21 also converts alternating current input from the electric motor 23 into direct current and outputs the direct current to the battery 22. The reducer 24 includes a transmission 24A and a differential gear 24B, and reduces the output of the electric motor 23 at a gear ratio based on the control of the control device 3, and transmits the reduced output to the wheels 25. The brake mechanism 26 includes, for example, a hydraulic or electric disc brake, and generates a braking force on the wheels 25 by friction.

[0011] The control device 3 includes an accelerator position sensor 4 as an accelerator operation amount sensor, a vehicle speed sensor 5, a vehicle distance sensor 6, and a controller 7.

[0012] The accelerator position sensor 4 detects the amount of accelerator operation of the vehicle 1. The accelerator position sensor 4 is configured by, for example, a pedal stroke sensor, and detects the amount of operation of an accelerator pedal 41, which serves as driving force request operation means, as the accelerator operation amount.

[0013] The vehicle speed sensor 5 is configured, for example, by a rotation speed sensor of the wheels 25, and detects the speed of the vehicle 1 (hereinafter referred to as vehicle speed).

[0014] The inter-vehicle distance sensor 6 is mounted on the vehicle 1 and detects the relative speed of the vehicle 1 with respect to the preceding vehicle and the inter-vehicle distance between the preceding vehicle and the vehicle 1. In this embodiment, the inter-vehicle distance sensor 6 includes a camera 61 and a radar 62, and the relative speed and inter-vehicle distance between the vehicle 1 and the preceding vehicle recognized by the camera 61 are detected by the radar 62. Note that the radar 62 may be a laser radar, a millimeter-wave radar, a LiDAR (Light Detection and Ranging), or the like. The relative speed is the speed of the vehicle 1 relative to the preceding vehicle, and therefore takes a negative value when the speed of the vehicle 1 is higher than that of the preceding vehicle, and takes a positive value when the speed of the vehicle 1 is lower.

[0015] The controller 7 controls the braking / driving torque generated by the electric motor 23 and the braking torque generated by the brake mechanism 26 based on the accelerator operation amount, the vehicle speed, etc. The controller 7 is configured by, for example, a microcomputer including a calculation unit such as a CPU (Central Processing Unit) and a GPU (Central Graphics Processing Unit), a storage unit 71 such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and an input / output unit such as an input / output interface. The accelerator position sensor 4, the vehicle speed sensor 5, the inter-vehicle distance sensor 6, the inverter 21, and the brake mechanism 26 are electrically or communicatively connected to the controller 7.

[0016] 2 is a control block diagram of the controller 7. As shown in FIG. 2, the controller 7 includes a storage unit 71, a driver request torque setting unit 72 as a driver request setting unit, a target deceleration setting unit 73, a correction torque setting unit 74 as a deceleration target value setting unit, a change rate limiting unit 75, and a braking / driving torque setting unit 76.

[0017] The storage unit 71 stores a computer program for causing the controller 7 to function, various maps used for control, various parameter values, etc. The maps stored in the storage unit 71 include, for example, a map that defines the relationship between the accelerator operation amount, the vehicle speed, and the driver-requested torque, and a map that defines the relationship between the vehicle speed of the preceding vehicle and the equilibrium inter-vehicle distance. The parameter values ​​stored in the storage unit 71 include, for example, a preset change amount that is used as the allowable change rate of the correction torque.

[0018] The driver request torque setting unit 72 sets the driver request torque based on the accelerator operation amount and the vehicle speed. The driver request torque is the torque that the driver requests through the operation of the accelerator pedal 41.

[0019] The target deceleration setting unit 73 sets a target deceleration of the vehicle 1 based on the inter-vehicle distance and the relative speed with respect to the preceding vehicle. In this embodiment, the target deceleration setting unit 73 sets an equilibrium inter-vehicle distance based on the vehicle speed of the preceding vehicle, which is obtained by adding the relative speed to the host vehicle speed, and sets a target deceleration of the vehicle 1 based on the difference between the inter-vehicle distance and the equilibrium inter-vehicle distance and the relative speed. The equilibrium inter-vehicle distance is an inter-vehicle distance that serves as a guide when the relative speed of the vehicle 1 with respect to the preceding vehicle is set to zero. The target deceleration setting unit 73 sets the equilibrium inter-vehicle distance, for example, by referring to the map shown in FIG. 3. The map shown in FIG. 3 is set so that the equilibrium inter-vehicle distance increases as the vehicle speed of the preceding vehicle increases. The target deceleration setting unit 73 calculates the target deceleration, for example, using the following equation (1):

[0020] ta = C1 × Vr ２÷(Ld-Lr) (1) ta: target deceleration C1: coefficient Vr: relative speed Ld: distance from the preceding vehicle (distance detected by the distance sensor 6) Lr: equilibrium distance

[0021] 2 , the correction torque setting unit 74 sets a correction torque as a target braking torque for the driver requested torque based on the target deceleration, the vehicle specifications of the weight of the vehicle 1 and the wheels 25, and vehicle characteristics such as the running resistance of the vehicle 1. The correction torque is a torque for performing a correction to decelerate the vehicle 1 at the target deceleration, and is set, for example, by subtracting a torque corresponding to the running resistance of the vehicle 1 from a value obtained by converting the target deceleration into torque using the vehicle specifications.

[0022] The change rate limiting unit 75 limits the change rate of the correction torque based on the change rate of the accelerator operation amount when the accelerator operation of the vehicle 1 is released from a state in which the accelerator operation is being performed.

[0023] Braking / driving torque setting unit 76 sets braking / driving torque to be generated by electric motor 23 and brake mechanism 26 based on the driver required torque and the correction torque. Braking / driving torque setting unit 76 outputs a command to inverter 21 to output the set braking / driving torque, and causes electric motor 23 to drive or perform regenerative operation in accordance with the command. If electric motor 23 alone is unable to generate the set braking torque, braking / driving torque setting unit 76 outputs a command to brake mechanism 26 to supplement the braking torque of electric motor 23, and causes brake mechanism 26 to perform braking operation in accordance with the command.

[0024] 4 and 5 are flowcharts of the braking / driving force control executed by controller 7. The control routine shown in the flowchart is pre-programmed and installed in controller 7. Controller 7 repeatedly executes the following control routine in accordance with the program, for example, at an operation cycle of about 10 milliseconds. Note that in FIGS. 4 and 5, deceleration is treated as negative acceleration and braking torque is treated as negative driving torque, and each is represented by a negative value.

[0025] In step S1 of FIG. 4, the controller 7 acquires the output values ​​of the sensors 4, 5, and 6, that is, the accelerator pedal operation amount, the vehicle speed, the inter-vehicle distance, and the relative speed.

[0026] In step S2, driver request torque setting unit 72 references, for example, a map that defines the relationship between accelerator operation amount, vehicle speed, and driver request torque, and sets driver request torque based on the accelerator operation amount and vehicle speed.

[0027] In step S3, the target deceleration setting unit 73 sets a target deceleration of the vehicle 1 based on the inter-vehicle distance and relative speed with respect to the preceding vehicle.

[0028] In step S4, the correction torque setting unit 74 sets a correction torque based on the target deceleration set in step S3, the vehicle specifications, and the vehicle characteristics.

[0029] In step S5, the change rate limiting unit 75 limits the change rate of the correction torque based on the change rate of the accelerator operation amount when the accelerator operation is released from a state in which the accelerator of the vehicle 1 is being operated. The method for limiting the change rate of the correction torque will be described later with reference to FIGS. 5 and 6.

[0030] In step S6, braking / driving torque setting unit 76 sets braking / driving torque based on the driver required torque and the correction torque. Braking / driving torque setting unit 76 also outputs commands to inverter 21 and brake mechanism 26 to output the set braking / driving torque, and causes electric motor 23 to drive or perform regenerative operation or brake mechanism 26 to perform braking operation in accordance with the commands.

[0031] The flow chart of the correction torque change rate limit shown in FIG. 5 will be described below with reference to the time chart of FIG.

[0032] 5, the change rate limiting unit 75 calculates the amount of change in the driver requested torque per calculation cycle as the change rate of the driver requested torque. In this embodiment, the change rate limiting unit 75 calculates the amount of change in the driver requested torque for each calculation cycle over a predetermined number of consecutive calculation cycles, for example, five calculation cycles of 10 milliseconds, and averages these amounts of change.

[0033] In the next step S52, the change rate limiting unit 75 determines whether the accelerator operation has been released from a state in which the accelerator operation was being performed. If it is determined in step S52 that the accelerator operation has been released, the process proceeds to step S53, and if not, the process proceeds to step S57.

[0034] In step S53, the change rate limiter 75 determines whether the amount of change in the driver requested torque when the accelerator pedal is released from an accelerator operation state is greater than a preset amount of change. The preset amount of change is a fixed value in this embodiment, and allows the correction torque to change more slowly than when the amount of change in the driver requested torque is used as the allowable amount of change in the correction torque.

[0035] If it is determined in step S53 that the change in the driver requested torque is equal to or less than a predetermined change, the change rate limiting unit 75 sets the predetermined change rate as the change in the correction torque per calculation cycle, which is the allowable change rate of the correction torque, in step S54.

[0036] On the other hand, if it is determined in step S53 that the change amount of the driver requested torque is greater than the predetermined change amount, the change rate limiting unit 75 sets the change amount of the driver requested torque as the change amount of the correction torque per calculation cycle in step S55.

[0037] 6, at time T1, the accelerator is released from a state in which the accelerator is being operated, and the accelerator operation amount becomes zero. The change rate limiting unit 75 determines the amount of change in the driver requested torque at this time as the allowable amount of change in the correction torque.

[0038] In the following step S56, the change rate limiting unit 75 sets the allowable torque to an initial value. The allowable torque is a torque for limiting the correction torque to an allowable value. Of the correction torques shown in FIG. 6, the dashed dotted line indicates the allowable torque. In FIG. 6, the allowable torque is set to the initial value at time T1. The initial value of the allowable torque may be, for example, a predetermined value or a previously stored value.

[0039] In the next step S57, the change rate limiting unit 75 determines whether the value of the correction torque is less than the allowable torque. If it is determined in step S57 that the correction torque is less than the allowable torque, the change rate limiting unit 75 limits the correction torque to the value of the allowable torque in step S58. At time T1 in Figure 6, the correction torque before limiting is less than the allowable torque, so the correction torque is limited to the value of the allowable torque.

[0040] In the next step S59, the change rate limiting unit 75 subtracts the allowable change amount from the allowable torque for each calculation cycle. As a result, the allowable torque decreases at the change rate of the driver requested torque from time T1, as shown in Fig. 6. By limiting the correction torque by this allowable torque, the correction torque decreases at a rate faster than the gradual change rate based on a preset change rate, in accordance with the change rate of the driver requested torque.

[0041] Thereafter, the allowable torque decreases, and when the allowable torque reaches the pre-limiting correction torque as shown at time T2 in FIG. 6 , it is determined in step S57 that the correction torque is equal to or greater than the allowable torque, and the process proceeds to step S60. In step S60, the change rate limiting unit 75 determines whether the correction torque is smaller than the value obtained by subtracting a preset change amount from the previous correction torque. If it is determined in step S60 that the correction torque is smaller than the value obtained by subtracting the preset change amount from the previous correction torque, the change rate limiting unit 75 limits the correction torque to the value obtained by subtracting the preset change amount from the previous correction torque in step S61. As a result, the correction torque decreases at a slow rate of change by the preset change amount from time T2 as shown in FIG. 6 .

[0042] According to the above-described embodiment, the rate of change of the correction torque is limited based on the rate of change of the accelerator operation amount when the accelerator is released from a state in which the accelerator is being operated, so the correction torque can be changed quickly in accordance with the rate of change of the accelerator operation amount when the accelerator is released. As a result, deceleration begins sooner when the accelerator is released, improving the ability to follow the preceding vehicle, thereby achieving both comfortable drivability and the ability to follow the preceding vehicle.

[0043] According to this embodiment, the rate of change of the driver required torque is set corresponding to the rate of change of the accelerator operation amount when the accelerator is released from a state in which the accelerator is being operated, and the rate of change of the correction torque is limited based on the rate of change of the driver required torque. Because the behavior of the vehicle 1 when the accelerator is released is proportional to the correction torque and the target acceleration, setting the amount of change of the correction torque and the target acceleration based on the driver required torque and the driver required acceleration corresponding to the rate of change of the accelerator opening rather than setting them according to the rate of change of the accelerator opening improves continuity with the behavior of the vehicle 1 immediately before the accelerator was released and improves drivability.

[0044] As described above, the best configurations, methods, and the like for implementing the present invention have been disclosed in the above description, but the present invention is not limited thereto. That is, although the present invention has been particularly illustrated and described mainly with reference to specific embodiments, those skilled in the art can make various modifications to the above-described embodiments in terms of shape, material, quantity, and other detailed configurations without departing from the scope of the technical idea and purpose of the present invention. Furthermore, the above-disclosed descriptions limiting the shape, material, and the like are provided as examples to facilitate understanding of the present invention and are not intended to limit the present invention. Therefore, descriptions using names of components that are free from some or all of the limitations on shape, material, and the like are included in the present invention.

[0045] The braking / driving force generation device 2 may include an internal combustion engine, which drives a generator to supply electricity to the electric motor 23, thereby driving the wheels 25 with the electric motor 23, or the wheels 25 may be driven by the electric motor 23 and the internal combustion engine together. In other words, the vehicle 1 may be a so-called series hybrid vehicle or a parallel hybrid vehicle.

[0046] In the control device 3, the driving force request operation means is configured by the accelerator pedal 41, and the accelerator operation amount sensor is configured by the accelerator position sensor 4, but other configurations may be used. For example, the driving force request operation means may be configured by an operation lever, an operation dial, or the like, and the accelerator operation amount sensor may be configured by a sensor such as a stroke sensor or potentiometer that detects the amount of operation of these.

[0047] The vehicle speed sensor 5 is not particularly limited, and may be, for example, a ground speed sensor.

[0048] The inter-vehicle distance sensor 6 may be equipped with only one of the camera 61 and the radar 62, or, for example, may be equipped with multiple cameras 61 and no radar 62, or may be equipped with multiple radars 62 and no camera 61.

[0049] When the braking / driving torque set by the braking / driving torque setting unit 76 is a braking torque, the controller 7 may generate the braking torque only by the electric motor 23, or may generate the braking torque by the electric motor 23 and the brake mechanism 26, or may generate the braking torque only by the brake mechanism 26.

[0050] The controller 7 may limit the rate of change of the target deceleration based on the rate of change of the accelerator operation amount when the accelerator operation is released from a state in which the accelerator is being operated, and set the correction torque based on the limited target deceleration. For example, as shown in FIG. 7 , the controller 7 may include a memory unit 71, a driver-requested acceleration / deceleration setting unit 72A as a driver-request setting unit, a target deceleration setting unit 73 as a deceleration target value setting unit, a correction torque setting unit 74, a change rate limiting unit 75A, and a braking / driving torque setting unit 76. The driver-requested acceleration / deceleration setting unit 72A sets the driver-requested acceleration / deceleration based on the accelerator operation amount and the vehicle speed. The driver-requested acceleration / deceleration is the acceleration / deceleration of the vehicle 1 requested by the driver via operation of the accelerator pedal 41, and includes the driver-requested acceleration and the driver-requested deceleration. The change rate limiting unit 75A sets the rate of change of the driver-requested deceleration corresponding to the rate of change of the accelerator operation amount when the accelerator operation amount is set to zero, and limits the rate of change of the target deceleration based on the rate of change of the driver-requested deceleration.

[0051] The target deceleration setting unit 73 may set the target deceleration of the vehicle 1 based on the inter-vehicle distance and the relative speed with respect to the preceding vehicle, without using the parallel inter-vehicle distance.

[0052] The change rate limiting units 75 and 75A may set the allowable change amount of the correction torque and the allowable change amount of the target acceleration based on the rate of change of the accelerator operation amount when the accelerator operation is released from a state in which the accelerator is being operated, without using the driver requested torque or the driver requested deceleration. For example, the change rate limiting units 75 and 75A may set a predetermined first change amount as the allowable change amount when the absolute value of the change amount of the accelerator operation amount when the accelerator operation is released is smaller than a predetermined value and the rate of change of the accelerator operation amount is low, and may set a second change amount whose rate of change is faster than the first change amount as the allowable change amount when the absolute value of the change amount of the accelerator operation amount is greater than the predetermined value and the rate of change of the accelerator operation amount is high.

[0053] If it is determined in step S53 that the change in the driver requested torque is equal to or less than a predetermined change, the change rate limiting unit 75 sets the predetermined change rate as the change in the correction torque per calculation cycle, which is the allowable change rate of the correction torque, in step S54.

[0054] 1... vehicle, 6... inter-vehicle distance sensor, 7... controller, 74... correction torque setting section (deceleration target value setting section), 75... change speed limiting section, 76... braking / driving torque setting section

Claims

1. A vehicle control method comprising: setting a target deceleration or target braking torque for the vehicle based on the distance to a preceding vehicle and the relative speed of the vehicle with respect to the preceding vehicle; limiting the rate of change of the target deceleration or the target braking torque based on the rate of change of accelerator operation amount when the accelerator operation of the vehicle is released from a state in which the accelerator is being operated; and setting the braking torque to be generated in the vehicle based on the target deceleration or the target braking torque.

2. A vehicle control method as claimed in claim 1, wherein a driver-requested deceleration or a driver-requested torque is set based on the accelerator operation amount, a rate of change of the driver-requested deceleration or the driver-requested torque is set corresponding to a rate of change of the accelerator operation amount when the accelerator operation is released from a state in which the accelerator is being operated, and the rate of change of the target deceleration or the target braking torque is limited based on the rate of change of the driver-requested deceleration or the rate of change of the driver-requested torque.

3. A control device for a vehicle, comprising: a controller for controlling the vehicle, the controller comprising: a deceleration target value setting unit that sets a target deceleration or target braking torque for the vehicle based on the distance to a preceding vehicle and the relative speed of the vehicle with respect to the preceding vehicle; a change rate limiting unit that limits the rate of change of the target deceleration or the target braking torque based on the rate of change of accelerator operation amount when the accelerator operation of the vehicle is released from a state in which the accelerator is being operated; and a braking / driving torque setting unit that sets the braking torque to be generated in the vehicle based on the target deceleration or the target braking torque.

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