Vehicular control method and control device

Abstract

This vehicular control method includes: setting a balanced inter-vehicle distance which is the distance to a preceding vehicle when the relative speed of a vehicle relative to the preceding vehicle is set to zero; calculating a target deceleration for the vehicle by using an expression (1); and controls the braking force of the vehicle so that the deceleration of the vehicle becomes the target deceleration.　Expression (1): ｔａ＝１／２×Ｖｒ２÷（Ｌｄ－Ｌｒ）. ta is the target deceleration; Vr is the relative speed; Ld is the inter-vehicle distance between the vehicle and the preceding vehicle; and Lr is the balanced inter-vehicle distance.

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 deceleration based on the vehicle speed and the distance and relative speed between the vehicle and the preceding vehicle, which results in large fluctuations in deceleration, making it difficult to achieve both smooth and comfortable drivability 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 and the ability to follow a preceding vehicle.

[0006] In one aspect of the present invention, an equilibrium inter-vehicle distance is set, which is the distance to the preceding vehicle when the relative speed of the vehicle with respect to the preceding vehicle is set to zero, and a target deceleration of the vehicle is calculated by the following equation (1): ta=½×Vr ２ ÷(Ld-Lr) (1) ta: target deceleration Vr: relative speed Ld: distance from preceding vehicle Lr: equilibrium distance

[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 flowchart of control executed by the controller. It is a flowchart of target deceleration setting executed by the 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 diagram showing the relationship between the relative speed and an upper limit value of the target deceleration. It is a timing chart showing the following state of a host vehicle relative to a preceding vehicle.

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 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, the driving force, braking force, driving torque, and braking torque are expressed by the positive or negative values ​​of the driving or braking force and braking or braking torque, so the braking force and braking torque are sometimes described as negative values. Furthermore, although deceleration is a physical quantity that takes a positive value, 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 force 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 following 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 required torque setting unit 72, an equilibrium inter-vehicle distance setting unit 73, a target deceleration setting unit 74, a target deceleration limiting unit 75, a correction torque setting unit 76, and a braking / driving torque setting unit 77.

[0017] The storage unit 71 stores a computer program for causing the controller 7 to function, various maps used for control, various thresholds, etc. The maps stored in the storage unit 71 include, for example, a map that defines the relationship between the accelerator operation amount and vehicle speed and the driver-requested torque, a map that defines the relationship between the vehicle speed of the preceding vehicle and the balanced inter-vehicle distance, and a map that defines the relationship between the relative speed and the upper limit of the target deceleration.

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

[0019] The balanced inter-vehicle distance setting unit 73 sets an balanced inter-vehicle distance, which is the distance to the preceding vehicle when the relative speed of the vehicle 1 with respect to the preceding vehicle is set to zero, based on the vehicle speed of the preceding vehicle.

[0020] The target deceleration setting unit 74 sets a target deceleration of the vehicle 1 based on the difference between the inter-vehicle distance and the equilibrium inter-vehicle distance from the preceding vehicle, and the relative speed. When the target deceleration is equal to or less than a threshold value, the target deceleration setting unit 74 sets the target deceleration to zero.

[0021] The target deceleration setting unit 74 calculates the target deceleration using the following formula (1): ta=½×Vr ２ ÷(Ld-Lr) (1) ta: target deceleration Vr: relative speed Ld: distance from the preceding vehicle (distance detected by the distance sensor 6) Lr: equilibrium distance

[0022] When vehicle 1 is following a preceding vehicle, in order to achieve smooth and comfortable driving, it is preferable that the relative speed and distance between vehicle 1 and the preceding vehicle be automatically reduced at a constant acceleration or deceleration. In other words, it is preferable that the acceleration and deceleration performed by vehicle 1 be constant acceleration motion.

[0023] In uniformly accelerated motion, if time is t, velocity is v, and acceleration is a, then v = at. Transforming this gives the following equation (2): t = v ÷ a (2)

[0024] On the other hand, the distance is the derivative of the velocity, and so if the distance is L, it is expressed by the following equation (3).

[0025]

[0026] Substituting equation (2) into equation (3) gives the following equation (4): L = 1 / 2 × a × (v ÷ a) ２ = 1 / 2 × v ２ ÷ a … (4)

[0027] When formula (4) is transformed with respect to a, the following formula (5) is obtained: a = 1 / 2 × v ２ ÷L … (5)

[0028] Equation (1) is obtained by replacing L in equation (5) with the difference between the inter-vehicle distance to the preceding vehicle and the equilibrium inter-vehicle distance. Therefore, according to equation (1), a target deceleration is set that decelerates vehicle 1 at the smallest constant deceleration so that the relative speed becomes zero before the inter-vehicle distance reaches the equilibrium inter-vehicle distance. Therefore, if vehicle 1 is decelerated at the target deceleration, maximum vehicle tracking ability can be obtained with a limited amount of control.

[0029] The target deceleration limiting unit 75 sets an upper limit value for the target deceleration based on the relative speed, and limits the target deceleration to be equal to or less than the upper limit value.

[0030] The correction torque setting unit 76 sets a correction 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 making 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.

[0031] Braking / driving torque setting unit 77 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 77 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 77 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.

[0032] 3 and 4 are flowcharts of the braking / driving force control executed by controller 7. The control routine shown in the flowchart is pre-programmed, and this program is installed in controller 7. In accordance with the program, controller 7 repeatedly executes the following control routine at an operation cycle of, for example, about 10 milliseconds.

[0033] In step S1 of FIG. 3, 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.

[0034] 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.

[0035] In step S3, the target deceleration setting unit 74 sets a target deceleration for the vehicle 1 based on the difference between the detected inter-vehicle distance and the balanced inter-vehicle distance, and the relative speed. The method for setting the target deceleration will be described later with reference to FIG. 4.

[0036] In step S4, the correction torque setting unit 76 sets the correction torque based on the target deceleration set in step S3, the vehicle specifications, and the vehicle characteristics. The correction torque setting unit 76 sets the correction torque when the accelerator operation amount is zero or equal to or less than a predetermined value.

[0037] In step S5, braking / driving torque setting unit 77 sets braking / driving torque based on the driver required torque and the correction torque. In this embodiment, braking / driving torque setting unit 77 sets braking / driving torque by adding the correction torque to the driver required torque. Braking / driving torque setting unit 77 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.

[0038] 4 is a flowchart of the target deceleration setting executed by the controller 7. In step S31 of FIG. 4, the balanced inter-vehicle distance setting unit 73 adds the relative speed to the host vehicle speed to set the speed of the preceding vehicle. At this time, the balanced inter-vehicle distance setting unit 73 limits the speed of the preceding vehicle to zero or more.

[0039] In step S32, the balanced inter-vehicle distance setting unit 73 sets the balanced inter-vehicle distance based on the vehicle speed of the preceding vehicle. In this embodiment, the balanced inter-vehicle distance setting unit 73 sets the balanced inter-vehicle distance by referring to the map shown in Fig. 5, for example. The map shown in Fig. 5 is set so that the balanced inter-vehicle distance increases as the vehicle speed of the preceding vehicle increases.

[0040] 4, the target deceleration setting unit 74 sets the target deceleration using the above formula (1). The difference between the inter-vehicle distance and the equilibrium inter-vehicle distance used in formula (1) is limited to zero or more.

[0041] In step S34, the target deceleration limiting unit 75 sets an upper limit for the target deceleration based on the relative speed, and limits the target deceleration to be equal to or less than the upper limit. In this embodiment, the balanced inter-vehicle distance setting unit 73 sets the upper limit for the target deceleration, for example, by referring to the map shown in FIG. 6. Note that deceleration is a physical quantity that takes a positive value, but the program of the controller 7 expresses deceleration as a negative value, so in FIG. 6, the target deceleration and its upper limit are negative values. In the map shown in FIG. 6, the relative speed is expressed as a negative value, so the upper limit for the target deceleration is set to increase as the negative value of the relative speed increases, i.e., as the speed of the vehicle 1 increases relative to the preceding vehicle.

[0042] In step S35 of Fig. 4, the target deceleration setting unit 74 determines whether the target deceleration exceeds the start threshold. If it is determined in step S35 that the target deceleration exceeds the start threshold, the target deceleration setting unit 74 sets a deceleration control flag in step S36; otherwise, the process proceeds to step S37. In step S37, the target deceleration setting unit 74 determines whether the target deceleration is equal to or less than the end threshold, and if it is determined that the target deceleration is equal to or less than the start threshold, the deceleration control flag is reset in step S38. Note that deceleration control refers to control performed using the target deceleration set using equation (1).

[0043] In step S39, the target deceleration setting unit 74 determines whether the deceleration control flag is set or not, and if it is determined that the flag is set, the target deceleration is left as is in step S40, and if it is determined that the flag is not set, the target deceleration is set to zero in step S41.

[0044] 7 is a timing chart showing the state in which the vehicle 1 follows the preceding vehicle, in which the vehicle 1 accelerates toward the preceding vehicle traveling at a substantially constant speed, and then the accelerator pedal is released, causing the vehicle 1 to follow the preceding vehicle.

[0045] 7, as vehicle 1 accelerates, the difference between the detected inter-vehicle distance and the equilibrium inter-vehicle distance gradually decreases, and at time T1, the target deceleration begins to exceed the start threshold. Accordingly, the correction torque is set as shown by the solid line in FIG. 7, but because the accelerator is being operated at time T1, the final correction torque is zero at this time, as shown by the dashed line in the figure.

[0046] After that, when the accelerator is released at time T2, the final correction torque is set as shown by the dashed line in Figure 7. As a result, the braking / driving torque is set by subtracting the final correction torque from the driver requested torque, and deceleration at the target deceleration begins.

[0047] After that, vehicle 1 decelerates at a roughly constant deceleration rate, and the relative speed becomes zero at time T3. In other words, vehicle 1 smoothly follows the preceding vehicle without braking, simply by releasing the accelerator. Then, by gradually applying the accelerator to match the speed of the preceding vehicle, vehicle 1 can continue to follow the preceding vehicle.

[0048] According to the above embodiment, the target deceleration of vehicle 1 is set using equation (1) based on the difference between the inter-vehicle distance and the equilibrium inter-vehicle distance with the preceding vehicle, and the relative speed between the preceding vehicle and vehicle 1, thereby suppressing fluctuations in deceleration and achieving both smooth and comfortable drivability and the ability to follow the preceding vehicle.

[0049] Here, if the target deceleration is set when the distance to the preceding vehicle is large, the deceleration of the vehicle 1 may start too early, which may result in the distance to the following vehicle becoming too small. In this embodiment, when the target deceleration is equal to or less than the threshold value, the target deceleration is set to zero, so that the deceleration control is not started until the vehicle 1 gets close to the preceding vehicle to a certain extent, and the deceleration control can be started at an appropriate timing.

[0050] Furthermore, in equation (1), since the relative speed is the denominator, if the relative speed becomes too small, a small change in the numerator may cause the target deceleration to fluctuate. In this embodiment, an upper limit value of the target deceleration is set based on the relative speed, and the target deceleration is limited to be equal to or less than the upper limit value. This suppresses fluctuations in the target deceleration, thereby achieving smooth and comfortable drivability.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] The vehicle speed sensor 5 is not particularly limited, and may be, for example, a ground speed sensor.

[0055] 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.

[0056] When the braking / driving torque set by the braking / driving torque setting unit 77 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.

[0057] The controller 7 may correct the torque by a method other than that described in the embodiment. For example, the controller 7 may calculate the ratio of the correction torque to the driver request torque and correct the torque by the correction torque amount by multiplying the driver request torque by (1 - calculated ratio).

[0058] 1...vehicle, 6...inter-vehicle distance sensor, 7...controller

Claims

1. A vehicle control method, comprising: setting an equilibrium inter-vehicle distance, which is the distance to a preceding vehicle when the relative speed of the vehicle with respect to the preceding vehicle is set to zero; calculating a target deceleration of the vehicle using the following formula (1); and controlling the braking force of the vehicle so that the deceleration of the vehicle becomes the target deceleration: ta = 1 / 2 × Vr ２ ÷(Ld-Lr) (1) ta: target deceleration Vr: relative speed Ld: distance from preceding vehicle Lr: equilibrium distance 2. A vehicle control method according to claim 1, wherein when the target deceleration is equal to or less than a threshold value, the target deceleration is set to zero.

3. A vehicle control method according to claim 1 or 2, wherein an upper limit value of the target deceleration is set based on the relative speed, and the target deceleration is limited to be equal to or less than the upper limit value.

4. A vehicle control device comprising a controller that sets an equilibrium inter-vehicle distance, which is the distance to a preceding vehicle when the relative speed of the vehicle with respect to the preceding vehicle is set to zero, calculates a target deceleration of the vehicle using the following formula (1), and controls the braking force of the vehicle so that the deceleration of the vehicle becomes the target deceleration: ta = 1 / 2 × Vr ２ ÷(Ld-Lr) (1) ta: target deceleration Vr: relative speed Ld: distance from preceding vehicle Lr: equilibrium distance

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