Control method of electric vehicle and control device of electric vehicle

Abstract

In a control method of an electric vehicle, a target inter-vehicle time, which is a target value of an inter-vehicle time obtained by dividing an inter-vehicle distance of the electric vehicle with respect to a preceding vehicle by the speed of the electric vehicle, is learned on the basis of the accelerator operations, brake operations, speed, and inter-vehicle distance of the electric vehicle, and the regenerative braking force of the electric vehicle is controlled on the basis of the learned target inter-vehicle time.

Description

Control method for electric vehicle and control device for electric vehicle

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

[0002] 2. Description of the Related Art A control device is known that controls the driving force 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] JP 2011-143798 A

[0004] In the vehicle control device described in Patent Document 1, the control threshold for the inter-vehicle time is set uniformly regardless of the driver, so depending on the driver, the inter-vehicle time during control may not match the driver's intentions.

[0005] An object of the present invention is to provide a control method and a control device for an electric vehicle that can bring the inter-vehicle time during control closer to what the driver intends.

[0006] In one aspect of the present invention, a target inter-vehicle time is learned based on the accelerator operation, brake operation, speed, and inter-vehicle distance of an electric vehicle to a preceding vehicle, the target inter-vehicle time being obtained by dividing the inter-vehicle distance by the speed of the electric vehicle, and the regenerative braking force of the electric vehicle is controlled based on the learned target inter-vehicle time.

[0007] It is a schematic diagram showing a general configuration of an electric 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 showing a method of learning a target THW. It is a diagram for explaining the target THW before and after learning. It is a flowchart showing a method of setting a correction amount of braking / driving force. It is a diagram showing the relationship between THW and target deceleration at an arbitrary vehicle speed. It is a diagram showing the relationship between TTC and target deceleration at an arbitrary vehicle speed.

[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 braking or driving force requesting operation means such as an accelerator pedal will be referred to as an "accelerator operation," the amount of operation will be referred to as an "accelerator operation amount," and an operation to reduce the accelerator operation amount to zero will be referred to as an "accelerator-off operation." A driver's request for braking force using a braking force requesting operation means such as a brake pedal will be referred to as a "brake operation," the amount of operation will be referred to as a "brake operation amount," and an operation to reduce the brake operation amount to zero will be referred to as a "brake-off operation." Braking or driving force refers to driving force and braking force. While driving force and braking force are both physical quantities that take positive values, a program that executes control treats braking force as a negative driving force. Therefore, driving force and braking force are expressed by the positive and negative values ​​of the braking or driving force. Therefore, braking force may be described as a negative value. Although deceleration is a physical quantity that takes a positive value, for the same reason, deceleration may be described as a negative value.

[0009] 1 is a schematic diagram showing the general configuration of an electric vehicle (hereinafter referred to as vehicle) 10. Vehicle 10 is an electric vehicle that generates its driving force and regenerative braking force (hereinafter also referred to as braking / driving force) by an electric driving source. Vehicle 10 includes a control mode selection device 1, a braking / driving force generation device 2, and a control device 3.

[0010] The control mode selection device 1 is composed of switches, dials, buttons, touch panels, etc., and is capable of selecting the control mode of the control device 3. The control modes include, for example, a first control mode that generates a braking force equivalent to the engine brake of an engine-driven vehicle, and a second control mode that corrects the braking / driving force, for example by making the regenerative braking force generated by the electric motor 23 stronger than in the first control mode.

[0011] The braking / driving force generation device 2 includes an inverter 21, a battery 22, an electric motor 23, a reducer 24, and wheels 25. 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 inputs 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 predetermined gear ratio based on the control of the control device 3 and transmits the reduced output to the wheels 25.

[0012] The control device 3 includes a navigation device 4 , an accelerator position sensor 5 as an accelerator operation amount sensor, a brake sensor 6 as a brake operation amount sensor, a vehicle speed sensor 7 , a vehicle distance sensor 8 , and a controller 9 .

[0013] The navigation device 4 is equipped with a position detection sensor 41 such as a GNSS (Global Navigation Satellite System). The navigation device 4 acquires map information and driving environment information within a predetermined distance around the vehicle, and displays the map information and driving environment information on a display (not shown) provided in the vehicle, or outputs the map information and driving environment information by voice. For example, the navigation device 4 displays the current position of the vehicle 10 and a driving route to a destination or an intermediate destination on a map displayed on the display, or provides audio guidance. The driving environment information includes, for example, the speed of the vehicle 10, traffic volume and congestion information on the road on which the vehicle 10 is traveling, weather conditions, and road conditions. Weather conditions include the weather on the road and changes in road surface conditions due to weather. Road conditions include the degree of inclination of the road and unevenness of the road surface.

[0014] The accelerator position sensor 5 detects the amount of accelerator operation of the vehicle 10. The accelerator position sensor 5 is configured, for example, as a pedal stroke sensor, and detects the amount of operation of an accelerator pedal 51, which serves as braking / driving force request operation means, as the amount of accelerator operation.

[0015] The brake sensor 6 detects the amount of braking operation of the vehicle 10. The brake sensor 6 is configured by, for example, a pedal stroke sensor, and detects the amount of operation of a brake pedal 61, which serves as braking force request operation means, as the amount of braking operation.

[0016] The vehicle speed sensor 7 is configured, for example, by a rotation speed sensor of the wheels 25, and detects the speed of the vehicle 10 (hereinafter referred to as vehicle speed).

[0017] The inter-vehicle distance sensor 8 is mounted on the vehicle 10 and detects the distance to a preceding vehicle and the relative speed of the vehicle 10 with respect to the preceding vehicle. In this embodiment, the inter-vehicle distance sensor 8 includes a camera 81 and a radar 82, and the radar 82 detects the inter-vehicle distance to the preceding vehicle recognized by the camera 81. Note that the radar 82 may be a laser radar, a millimeter-wave radar, a LiDAR (Light Detection and Ranging), or the like.

[0018] The controller 9 controls the braking / driving force generated by the electric motor 23 based on the vehicle speed, the accelerator operation amount, etc. The controller 9 is realized by, for example, a microcomputer including a calculation unit such as a CPU or a GPU, a storage unit 91 such as a ROM or a RAM, and an input / output unit such as an input / output interface. The control mode selection device 1, the navigation device 4, the accelerator position sensor 5, the brake sensor 6, the vehicle speed sensor 7, the inter-vehicle distance sensor 8, and the inverter 21 are electrically or communicatively connected to the controller 9.

[0019] 2 is a control block diagram of the controller 9. As shown in FIG. 2, the controller 9 includes a memory unit 91, a correction necessity determination unit 92, a basic braking / driving force setting unit 93, a preceding vehicle detection determination unit 94, a THW learning unit 95, a TTC calculation unit 96, a correction amount setting unit 97, and a braking / driving force setting unit 98.

[0020] The memory unit 91 stores a computer program for causing the controller 9 to function, various maps used for control, various parameter values, etc. The maps stored in the memory unit 91 include, for example, a map that defines the relationship between the accelerator operation amount, vehicle speed, and basic braking / driving force, a map that defines the relationship between THW (Time Headway), which is the time between the vehicle 10 and the preceding vehicle (also called headway time), and a target deceleration, and a map that defines the relationship between TTC (Time to Collision), which is the time until the vehicle 10 reaches the preceding vehicle, and a target deceleration. The parameter values ​​stored in the memory unit 91 include, for example, an initial value of a target value of THW, which is the target time between the vehicles, and various thresholds.

[0021] The correction necessity determining unit 92 determines whether or not the braking / driving force needs to be corrected based on the input of the control mode selected by the control mode selecting device 1 .

[0022] The basic braking / driving force setting unit 93 sets basic braking / driving forces based on the accelerator operation amount and the vehicle speed. The basic braking / driving forces are braking / driving forces that are applied without correction.

[0023] The preceding vehicle detection and determination unit 94 detects the presence or absence of a preceding vehicle based on the output of the inter-vehicle distance sensor 8 .

[0024] The THW learning unit 95 calculates the THW, which is the inter-vehicle time from the vehicle 10 to the preceding vehicle. The THW learning unit 95 also learns the target THW based on the accelerator operation, brake operation, vehicle speed, and inter-vehicle distance from the preceding vehicle of the vehicle 10. In this embodiment, the THW learning unit 95 also takes into consideration driving environment information acquired from the navigation device 4 when learning the target THW.

[0025] The TTC calculation unit 96 calculates the TTC, which is the time to reach the preceding vehicle, based on the inter-vehicle distance and relative speed to the preceding vehicle.

[0026] The correction amount setting unit 97 sets a correction amount for the basic braking / driving force based on the THW, TTC, accelerator operation amount of the vehicle 10, and vehicle speed. In the present embodiment, the correction amount setting unit 97 sets a target deceleration for the vehicle 10 based on the THW, TTC, accelerator operation amount, and vehicle speed, and sets a correction amount for the basic braking / driving force based on the target deceleration. A correction is performed by the correction amount to decelerate the vehicle 10 at the target deceleration.

[0027] Braking / driving force setting unit 98 sets the braking / driving forces to be generated by electric motor 23 based on the determination result of correction necessity determination unit 92, the basic braking / driving force, and the correction amount. Braking / driving force setting unit 98 outputs a command to inverter 21 to output the set braking / driving force, and causes electric motor 23 to drive or regenerate in accordance with the command.

[0028] 3 is a flowchart of the control executed by the controller 9. The control routine shown in the flowchart is pre-programmed, and this program is installed in the controller 9. In accordance with the program, the controller 9 repeatedly executes the following control routine at an operation cycle of, for example, about 10 milliseconds.

[0029] In step S1 of FIG. 3, the controller 9 acquires the outputs of the control mode selection device 1, the navigation device 4, and the sensors 5, 6, 7, and 8, i.e., the control mode, driving environment information, accelerator operation amount, brake operation amount, vehicle speed, inter-vehicle distance, and relative vehicle speed.

[0030] In step S2, the basic braking / driving force setting unit 93 refers to a map that defines the relationship between the accelerator operation amount, vehicle speed, and basic braking / driving force, and sets the basic braking / driving force based on the accelerator operation amount and vehicle speed.

[0031] In step S3, correction necessity determination unit 92 determines whether the second control mode, which corrects the braking / driving force, has been selected. If it is determined in step S3 that the second control mode has been selected, the process proceeds to step S4; otherwise, braking / driving force setting unit 98 sets the basic braking / driving force to the final braking / driving force in step S9.

[0032] In step S4, the preceding vehicle detection determination unit 94 determines whether or not a preceding vehicle has been detected based on the output of the inter-vehicle distance sensor 8. If it is determined in step S4 that a preceding vehicle has not been detected, the braking / driving force setting unit 98 sets the basic braking / driving force to the final braking / driving force in step S9.

[0033] On the other hand, if it is determined in step S4 that a preceding vehicle has been detected, then in step S5, the THW learning unit 95 calculates the THW using the following formula (1). Also, the TTC calculation unit 96 calculates the TTC using the following formula (2). THW = Inter-vehicle distance / Vehicle speed (1) TTC = Inter-vehicle distance / Relative vehicle speed (2)

[0034] In step S6, the THW learning unit 95 learns the target THW. The method for learning the target THW will be described later with reference to FIGS.

[0035] In step S7, correction amount setting unit 97 sets the amount of correction for braking / driving force. The method for setting the correction amount will be described later with reference to FIG.

[0036] In step S8, braking / driving force setting unit 98 sets the final braking / driving force to a value obtained by adding the correction amount to the basic braking / driving force, and outputs a command to electric motor 23 to output the set braking / driving force. If the set braking / driving force is positive, positive torque is output from electric motor 23 to become driving force, and if it is negative, regeneration is performed by electric motor 23 to become braking force.

[0037] 4 is a flowchart showing a method for learning the target THW. In step S61 of FIG. 4, the THW learning unit 95 determines whether the value obtained by subtracting THW from the target THW exceeds a threshold value. If it is determined in step S61 that the value obtained by subtracting THW from the target THW exceeds the threshold value, the THW learning unit 95 determines in step S62 whether an accelerator release operation has occurred or whether the decrease in the accelerator operation amount has exceeded the threshold value. If it is determined in step S62 that an accelerator release operation has occurred or that the decrease in the accelerator operation amount has exceeded the threshold value, the process proceeds to step S65, in which the reciprocal of the THW at that time is stored.

[0038] Here, as an example, when it is determined in step S61 that the value obtained by subtracting THW from target THW exceeds the threshold value and when it is determined in step S62 that an accelerator release operation has been performed, for example, is when, while continuing accelerator operation, vehicle 10 approaches the preceding vehicle to a distance where THW is smaller than target THW by a threshold value or more, as shown in Figure 5, and the accelerator is released, or when the accelerator is released, but vehicle 10 decelerates more than the driver expected and moves away from the preceding vehicle, so the driver resumes accelerator operation, and vehicle 10 approaches the preceding vehicle to a distance where THW is smaller than target THW by a threshold value or more. In these cases, it is considered that the target THW does not match the driver's intention, and the reciprocal of THW at that time is stored.

[0039] Returning to FIG. 4, if it is determined in step S61 that the value obtained by subtracting THW from target THW does not exceed the threshold value, then in step S63, the THW learning unit 95 determines whether the value obtained by subtracting THW from target THW exceeds the threshold value.

[0040] If it is determined in step S63 that the value obtained by subtracting the target THW from the THW exceeds the threshold, then in step S64, the THW learning unit 95 determines whether an accelerator release operation has been performed, whether a brake release operation has been performed, whether the decrease in the accelerator operation amount has exceeded the threshold, or whether the increase in the brake operation amount has exceeded the threshold. If it is determined in step S64 that an accelerator release operation or a brake release operation has been performed, or that the decrease in the accelerator operation amount or the increase in the brake operation amount has exceeded the threshold, the process proceeds to step S65, in which the reciprocal of the THW at that time is stored.

[0041] As an example, when it is determined in step S63 that the value obtained by subtracting the target THW from the THW exceeds the threshold value and when it is determined in step S64 that a brake-off operation has been performed, this occurs when the vehicle 10 is separated from the preceding vehicle to a distance where the THW is greater than the target THW by the threshold value or more, and then the brake-off operation is performed after the braking operation is started, as shown in Figure 5. In this case, it is considered that the target THW does not match the driver's intention, and therefore the reciprocal of the THW at this time is stored.

[0042] 4, in step S65, the THW learning unit 95 stores the reciprocal of the THW in the storage unit 91. The driver's sense of risk when following a preceding vehicle is expressed as the reciprocal of the THW and the reciprocal of the TTC, but while there is little difference in the reciprocal of the TTC between drivers, there is difference in the reciprocal of the THW between drivers. For this reason, in this embodiment, the THW learning unit 95 stores the reciprocal of the THW as a value representing the driver's characteristics.

[0043] After storing the reciprocal of THW in step S65, in step S66 the THW learning unit 95 restores the reciprocal of THW to the original value to set it as THW again, learns this THW as a target THW, and stores it in the storage unit 91. Furthermore, the THW learning unit 95 of this embodiment learns the target THW based on driving environment information. For example, the THW learning unit 95 learns the target THW for each driving environment, such as the traffic volume on the road, the presence or absence of congestion information, the weather, the degree of inclination of the road, the presence or absence of road surface irregularities, and stores it in the storage unit 91 as an individual target THW corresponding to the driving environment.

[0044] The above-described flow for learning the target THW is repeatedly executed in the calculation cycle of the controller 9, so that the THW learning unit 95 re-learns the learned target THW when the learning conditions are satisfied.

[0045] Fig. 6 is a flowchart showing a method for setting the braking / driving force correction amounts. In step S71 of Fig. 6, correction amount setting unit 97 sets a first target deceleration based on TWH, vehicle speed, and driving environment information, and sets a second target deceleration based on TTC, vehicle speed, and driving environment information. Memory unit 91 stores a map such as Fig. 7 showing the relationship between THW and first target deceleration, and a map such as Fig. 8 showing the relationship between TTC and second target deceleration, for each vehicle speed and driving environment. Correction amount setting unit 97 sets the first target deceleration and the second target deceleration by referring to these maps.

[0046] 7 is a diagram showing the relationship between THW and the first target deceleration at an arbitrary vehicle speed when road surface conditions are not changing due to weather. In Fig. 7, the first target deceleration is set to decrease as TWH becomes larger than a predetermined range of values ​​including the target THW, and to increase as TWH becomes smaller than the predetermined range.

[0047] 7, when the value of the target THW is changed through learning, the value of THW1 at which the first target deceleration begins to increase is also changed. That is, when the value of the target THW increases through learning, the value of THW1 is increased, and when the value of the target THW decreases through learning, the value of THW1 is decreased. Since the correction amount for the basic braking / driving force is determined based on the target deceleration, changing the first target deceleration in accordance with the learning result of the target THW changes the correction amount, which in turn changes the timing at which regenerative braking of the vehicle 10 begins and the magnitude of the regenerative braking force.

[0048] Returning to FIG. 6 , in step S72, the correction amount setting unit 97 sets a first coefficient based on the accelerator depression amount and a second coefficient based on the vehicle speed. When the accelerator depression amount is equal to or greater than a predetermined amount, the first coefficient reduces the sum of the first target deceleration and the second target deceleration to a value within a range from the sum to zero. For example, the first coefficient is a value within a range from 0 to 1, and is set smaller as the accelerator depression amount increases. When the vehicle speed is within a predetermined speed range, the second coefficient reduces the sum of the first target deceleration and the second target deceleration to a value within a range from the sum to zero. For example, the second coefficient is a value within a range from 0 to 1, and is set smaller when the vehicle speed is low or high, and larger when the vehicle speed is between low and high.

[0049] In step S73, the correction amount setting unit 97 sets the target deceleration of the vehicle 10 using the following equation (3): Target deceleration=(first target deceleration+second target deceleration)×first coefficient×second coefficient (3).

[0050] In step S74, the correction amount setting unit 97 sets upper and lower allowable limits for the target deceleration based on the vehicle speed, and limits the target deceleration to within the set upper and lower allowable limits. The upper and lower allowable limits may be, for example, fixed values ​​determined for each vehicle speed.

[0051] In step S75, the correction amount setting unit 97 limits the amount of change in the target deceleration over time, i.e., limits the rate of change. The amount of limit on the time change in the correction amount may be different or the same when the correction amount changes in the negative direction and when the correction amount changes in the positive direction.

[0052] In step S76, the correction amount setting unit 97 sets a correction amount for the basic braking / driving force based on the target deceleration. For example, the correction amount setting unit 97 sets the correction amount based on the target deceleration, the weight of the vehicle 10, the vehicle specifications of the wheels 25, and vehicle characteristics such as the running resistance of the vehicle 10. The correction amount set in this manner is used to correct the driving force when a preceding vehicle is detected. If the correction amount is positive and greater than zero, the braking / driving force is increased from the basic braking / driving force, and if the correction amount is negative, the braking / driving force is decreased from the basic braking / driving force.

[0053] According to the above-described embodiment, the target THW is learned based on the accelerator operation, brake operation, vehicle speed, and distance from the preceding vehicle of the vehicle 10, and the regenerative braking force of the vehicle 10 is controlled based on the learned target THW, so that the inter-vehicle time during control can be made closer to the driver's intention.

[0054] According to the embodiment, the target THW is learned when the accelerator is released, when the decrease in the accelerator operation amount exceeds a threshold, or when the increase in the brake operation amount exceeds a threshold, so that the target THW intended by the driver can be learned with high accuracy.

[0055] According to the embodiment, the target THW is re-learned when the difference between the learned target THW and the actual THW exceeds a threshold value, so that the target THW can be brought closer to the driver's intention while preventing erroneous learning.

[0056] According to the embodiment, the target THW is learned based on the driving environment, such as the speed of the vehicle 10, traffic volume on the road, weather conditions, and road conditions, so that the target THW can be learned according to the driving environment.

[0057] 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.

[0058] 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 10 may be a so-called series hybrid vehicle or a parallel hybrid vehicle.

[0059] In the control device 3, the braking / driving force request operation means is configured as the accelerator pedal 51, the braking force request operation means is configured as the brake pedal 61, the accelerator operation amount sensor is configured as the accelerator position sensor 5, and the brake operation amount sensor is configured as the brake sensor 6, but other configurations may also be used. For example, the braking / driving force request operation means and the braking force request operation means may be configured as an operation lever, an operation dial, or the like, and the accelerator operation amount sensor and the brake operation amount sensor may be configured as sensors such as a stroke sensor or a potentiometer that detect the amount of operation of these.

[0060] The vehicle speed sensor 7 is not particularly limited, and may be, for example, a ground speed sensor.

[0061] The inter-vehicle distance sensor 8 may be equipped with only one of the camera 81 and the radar 82, or, for example, may be equipped with multiple cameras 81 and no radar 82, or may be equipped with multiple radars 82 and no camera 81.

[0062] In addition to determining whether the increase in the brake operation amount exceeds a threshold, the THW learning unit 95 may also determine whether the rate of increase in the brake operation amount or the depression strength of the brake pedal 61 exceeds a threshold. This allows the degree of urgency or discomfort indicated by the driver's depression of the brake pedal 61 to be recognized and reflected in learning the target THW. The depression strength of the brake pedal 61 is proportional to the brake operation amount and may be determined from the brake operation amount. Alternatively, the brake fluid pressure that increases as the brake pedal 61 is depressed may be detected by a pressure sensor or a pedal force meter provided on the brake pedal 61. The THW learning unit 95 may set the target THW as the THW1 value at which the first target deceleration begins to increase. In this case, when the target THW value is changed through learning, the THW1 value at which the first target deceleration begins to increase is also changed. The THW learning unit 95 may store the THW itself, rather than the reciprocal of the THW, as a value representing the driver's characteristics, and perform learning using this THW as the target THW.

[0063] The correction amount setting unit 97 may set the correction amount for the basic braking / driving force based on the THW, TTC, accelerator operation amount, and vehicle speed, without setting the target deceleration. For example, the correction amount setting unit 97 may set a first correction amount based on the TWH, vehicle speed, and driving environment information, and set a second correction amount based on the TTC, vehicle speed, and driving environment information, and set the correction amount for the basic braking / driving force using the following equation (4): Correction amount = (first correction amount + second correction amount) × first coefficient × second coefficient (4)

[0064] 3...control device, 9...controller, 10...electric vehicle

Claims

1. A control method for an electric vehicle, comprising: learning a target inter-vehicle time, which is a target value for the inter-vehicle time obtained by dividing the inter-vehicle distance by the speed of the electric vehicle, based on the accelerator operation, brake operation, speed, and inter-vehicle distance of the electric vehicle from a preceding vehicle; and controlling the regenerative braking force of the electric vehicle based on the learned target inter-vehicle time.

2. A control method according to claim 1, wherein the target inter-vehicle time is learned when the accelerator operation amount is reduced.

3. A control method according to claim 2, wherein the target inter-vehicle time is learned when the amount of decrease in the accelerator operation amount exceeds a threshold value.

4. A control method according to claim 2, wherein the target inter-vehicle time is learned when an increase in the amount of brake operation exceeds a threshold value.

5. A control method according to claim 4, wherein the inter-vehicle time is learned when the rate of increase in the brake operation amount or the brake pedal depression strength exceeds a threshold value.

6. A control method according to claim 1, wherein the target inter-vehicle time is learned when the difference between the learned target inter-vehicle time and the inter-vehicle time exceeds a threshold value.

7. A control method according to claim 1, wherein the target inter-vehicle time is learned based on the driving environment of the electric vehicle.

8. A control method according to claim 7, wherein the driving environment of the electric vehicle is the speed of the electric vehicle.

9. A control method according to claim 7, wherein the driving environment of the electric vehicle is the traffic volume on the road on which the electric vehicle is traveling.

10. A control method according to claim 7, wherein the driving environment of the electric vehicle is weather conditions.

11. A control method according to claim 10, wherein the weather conditions are changes in road surface conditions due to weather.

12. A control method according to claim 7, wherein the driving environment of the electric vehicle is the condition of the road on which the electric vehicle is traveling.

13. A control method according to claim 12, wherein the road conditions are the slope of the road or the unevenness of the road surface.

14. A control device for an electric vehicle, comprising a controller that learns a target inter-vehicle time, which is a target value for the inter-vehicle time obtained by dividing the inter-vehicle distance by the speed of the electric vehicle, based on the accelerator operation, brake operation, speed, and inter-vehicle distance from a preceding vehicle of the electric vehicle, and controls the regenerative braking force of the electric vehicle based on the learned target inter-vehicle time.

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