Vehicle control method and vehicle control device

Abstract

To enable a driver to operate a vehicle stably when the vehicle outputs drive torque upon the driver releasing an accelerator.SOLUTION: In a vehicle control method for controlling a vehicle which outputs drive torque when a driver releases an accelerator, running resistance is detected and the drive torque upon accelerator-off operation is controlled based on the detected running resistance so that a vehicle speed remains constant.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a control technique for applying creep torque to a vehicle.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above control technique, when outputting creep torque (driving torque when the accelerator is off), the running resistance is not considered. Therefore, on a deceleration zone, a gradient road, etc., the vehicle speed does not stabilize, and depending on the situation, accelerator operation and brake operation by the driver are required.

[0005]

[0006] For example, when there is a step or the like on the road surface, the driver needs to step on the accelerator to get over it. Here, in a situation where it is necessary to decelerate the vehicle speed immediately after the accelerator operation, fine accelerator operation or quick brake operation is required. However, a driver with low driving skills or a slow reaction speed may have difficulty operating appropriately.

Means for Solving the Problems

[0007] ​According to an aspect of the present invention, there is provided a vehicle control method for controlling a vehicle that outputs driving torque when the driver releases the accelerator. In this vehicle control method, the running resistance is detected, and the driving torque when the accelerator is released is controlled so that the vehicle speed becomes constant based on the detected running resistance.

Advantages of the Invention

[0008] According to the above aspect, when crossing a step or the like, the driver can control the vehicle only by operating the brake, so that fine accelerator operations and quick brake operations are not required. Therefore, the driver can stably operate the vehicle.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0011] FIG. 1 is an example of a schematic configuration diagram of a vehicle 100 to which the vehicle control method according to an embodiment of the present invention is applied, as viewed from above. In FIG. 1, the forward traveling direction (upper side of the paper) of the vehicle 100 is defined as the front, the backward traveling direction (lower side of the paper) is defined as the rear, the left side in the state facing the front is defined as the left, and the right side is defined as the right. FIG. 2 is an example of a schematic configuration diagram of a control system for controlling the vehicle 100.

[0012] In this embodiment, the case where the vehicle 100 is a so-called battery electric vehicle (BEV) will be described. However, the vehicle 100 may be a series hybrid electric vehicle (HEV), a parallel hybrid electric vehicle, or a vehicle driven by an internal combustion engine. The type of the drive source for driving the wheels of the vehicle 100 is not limited.

[0013] The vehicle 100 includes a braking / driving unit 1, a driving force calculation unit 2, a radar 3, a front camera 4, side cameras 5L and 5R, a navigation system 6, an accelerator pedal opening sensor (hereinafter also referred to as an APO sensor) 7, a brake switch 8, a steering sensor 9, a gradient sensor 10, a vehicle speed detection unit 11, and a select switch 12.

[0014] The braking / driving unit 1 is a unit including an electric motor that is the drive source of the vehicle 100 and an inverter or the like that controls the electric motor. The electric motor operates by power supplied from a battery (not shown) and drives the wheels (not shown). Further, the electric motor generates a braking force by regenerating the kinetic energy of the vehicle 100 as electric power during deceleration. When the vehicle 100 is driven by an internal combustion engine, the braking / driving unit 1 is the internal combustion engine.

[0015] The driving force calculation unit 2 as a vehicle control device is composed of a microcomputer including a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). It is also possible to configure the driving force calculation unit 2 with a plurality of microcomputers.

[0016] The radar 3 is disposed, for example, near the front end of the vehicle body and detects the distance to and the direction of an object around the vehicle 100 using radio waves.

[0017] The front camera 4 is disposed, for example, near the rearview mirror facing the vehicle traveling direction, and captures the front of the vehicle 100 (region F1 in the figure). Note that the front camera 4 may be a camera unit including a camera that captures the above-described region F1 and a wide-angle camera that captures the side of the vehicle 100 (region F2 in the figure).

[0018] The side cameras 5L and 5R are provided, for example, with the side camera 5L on the left door mirror and the side camera 5R on the right door mirror, and capture the left side (region SL in the figure) and the right side (region SR in the figure) of the vehicle 100. Note that the side cameras 5L and 5R may be collectively referred to as the side camera 5.

[0019] The information detected by the radar 3 and the image information captured by the front camera 4 and the side cameras 5 are read into the driving force calculation unit 2. The driving force calculation unit 2 specifies the surrounding situation of the vehicle 100 based on this information, for example, the distance to the target, the relative distance to the target, the relative speed to the target, the attributes of the target, etc.

[0020] The navigation system 6 is disposed, for example, in the vehicle interior, and performs setting and guidance of a driving route to a destination set by the driver based on map information stored in advance and position information acquired from artificial satellites.

[0021] In addition, the navigation system 6 specifies the surrounding situation of the vehicle 100 based on map information stored in advance and position information acquired from artificial satellites, for example, the attributes of the road during travel, the curvature, the width, the speed limit, the position and content of traffic signs, and the position of signals. Here, the attributes of the road refer to highways, congested roads, winding roads, roads in densely populated areas, narrow roads, within parking lots, etc. Note that the curvature and width of the road during travel can also be specified using the image information captured by the front camera 4 and the side cameras 5.

[0022] Note that the vehicle 100 of the present embodiment includes the radar 3, the front camera 4, the side camera 5, and the navigation system 6 as devices for specifying the surrounding situation, but is not limited thereto. For example, instead of or in addition to any of the radar 3, the front camera 4, and the side camera 5, a lidar (Laser Imaging Detection and Ranging) may be provided. Further, instead of or in addition to the navigation system 6, a communication device capable of vehicle-to-vehicle communication, road-to-vehicle communication, etc. may be provided.

[0023] The accelerator pedal opening sensor 7 detects the opening of an accelerator pedal (not shown; hereinafter may be simply referred to as "accelerator") operated by the driver. A state where the opening of the accelerator pedal is not zero is referred to as accelerator on, and a state where the opening of the accelerator pedal is zero is referred to as accelerator off. The detected accelerator pedal opening is read into the driving force calculation unit 2.

[0024] The brake switch 8 detects the operation state of a brake pedal (not shown; hereinafter may be simply referred to as "brake") operated by the driver. A state where the brake pedal is depressed is referred to as brake on, and a state where the brake pedal is not depressed is referred to as brake off. The detected operation state (brake on / brake off) of the brake pedal is read into the driving force calculation unit 2.

[0025] The steering sensor 9 detects the operation state (steering angle, steering force) of a steering (not shown) operated by the driver. The detected operation state of the steering is read into the driving force calculation unit 2.

[0026] The gradient sensor 10 detects the road surface gradient. The detected road surface gradient is read into the driving force calculation unit 2.

[0027] The vehicle speed detection unit 11 includes, for example, a rotational speed sensor that detects the rotational speed of the wheels. The detected rotational speed of the wheels is read into the driving force calculation unit 2. The vehicle speed detection unit 11 may be configured to estimate the vehicle speed based on the output torque of the drive source, or may be configured to estimate the vehicle speed based on the position information of the vehicle 100 acquired from the navigation system 6, or may be configured to estimate the vehicle speed based on the information acquired from the cameras 4 and 5 and the radar 3.

[0028] The select switch 12 detects the operation mode (forward mode, reverse mode, neutral mode, parking mode, etc.) of the vehicle 100 selected by the driver using a shifter (not shown). The detected operation mode is read into the driving force calculation unit 2.

[0029] The driving force calculation unit 2 reads the surrounding situation information, which is the information regarding the surrounding situation of the vehicle 100 described above, the information detected by various sensors, etc., and controls the braking / driving unit 1 based on this information.

[0030] In the present embodiment, when a predetermined condition is satisfied, the driving force calculation unit 2 executes drive torque control for outputting drive torque (hereinafter also referred to as creep torque) to the electric motor, which is the drive source, when the driver releases the accelerator.

[0031] The predetermined condition is, for example, the following conditions.

[0032] (a) The driving mode (forward mode or reverse mode) is selected as the operation mode of the vehicle 100. (b) The vehicle speed is equal to or lower than a predetermined vehicle speed. The predetermined vehicle speed is, for example, a low vehicle speed of about 10 [km / h]. (c) The execution of the drive torque control is not prohibited by the driver. (When the driver can set whether to execute the drive torque control)

[0033] Here, consider the case where the driver needs to operate the accelerator or brake during the running of the vehicle 100 due to creep torque. As an example, there may be a step or the like on the road surface, and the driver may need to step on the accelerator to cross it.

[0034] In this case, further, when it is necessary to decelerate the vehicle speed immediately after the accelerator operation, fine accelerator operations or quick brake operations may be required. However, drivers with low driving skills or slow reaction speeds may have difficulty operating appropriately.

[0035] Therefore, the driving force calculation unit 2 of the present embodiment executes drive torque control according to the procedures shown in FIGS. 3 and 4 so that the driver can stably operate the vehicle 100.

[0036] Hereinafter, with reference to FIGS. 3 and 4, the drive torque control executed by the driving force calculation unit 2 will be described.

[0037] The drive torque control of the present embodiment includes a stop phase that is a process when the vehicle 100 is stopped and a running phase that is a process when the vehicle 100 is running. FIG. 3 is an example of a flowchart for explaining the stop phase of the drive torque control. FIG. 4 is an example of a flowchart for explaining the running phase of the drive torque control.

[0038] First, the stop phase will be described with reference to FIG. 3.

[0039] In step S11, the driving force calculation unit 2 determines whether the vehicle 100 is running (vehicle speed > 0 [km / h]).

[0040] When the vehicle speed is 0 [km / h], the driving force calculation unit 2 determines that the vehicle 100 is stopped and advances the process to step S12. In step S12, the process of the stop phase is started.

[0041] When the vehicle speed is not 0 [km / h], the driving force calculation unit 2 determines that the vehicle 100 is in motion and proceeds with the process to step S21. In step S21, the process for the in-motion phase is started. The in-motion phase will be described later.

[0042] In step S13, the driving force calculation unit 2 determines whether the accelerator pedal or the brake pedal is being operated.

[0043] When the accelerator is on or the brake is on, the driving force calculation unit 2 determines that the accelerator pedal or the brake pedal is being operated and proceeds with the process to step S20.

[0044] In step S20, the driving force calculation unit 2 stops the drive torque control. This can prevent the drive torque control from interfering with the driver's driving operation.

[0045] Also, in step S20, the driving force calculation unit 2 causes the display of the navigation system 6 and the instrument panel to indicate that the drive torque control is in a stopped state. This can inform the driver that the drive torque control has not stopped due to a malfunction.

[0046] When the accelerator is off and the brake is off, the driving force calculation unit 2 determines that neither the accelerator pedal nor the brake pedal is being operated and proceeds with the process to step S14.

[0047] In step S14, the driving force calculation unit 2, acting as a running resistance detection unit, performs a running resistance detection process.

[0048] The running resistance is a resistance force that hinders the movement of the vehicle 100 in the traveling direction when the vehicle 100 is traveling. Examples include gradient resistance, acceleration resistance, air resistance, rolling resistance, etc. Also, the structure of the road surface that the vehicle 100 has to overcome when traveling, such as a step on the road surface, can be treated as a running resistance.

[0049] The running resistance can be detected in various ways. As an example, in this embodiment, based on the specifications of the vehicle 100 and the experimental results, a map preset with parameters such as gradient resistance, acceleration resistance, air resistance, rolling resistance, etc. is referred to, and the running resistance is obtained. That is, when the running resistance value corresponding to the surrounding situation information and the information detected by various sensors is set in the map, the running resistance value is the running resistance detected by the running resistance detection process.

[0050] In step S15, the driving force calculation unit 2 determines whether the running resistance has been detected.

[0051] If the driving force calculation unit 2 can obtain the running resistance value by referring to the map, it determines that the running resistance has been detected and advances the process to step S16.

[0052] In step S16, the driving force calculation unit 2 as the driving torque control unit outputs a driving torque exceeding the detected running resistance to the electric motor to start the vehicle 100, and controls the driving torque so that a preset set vehicle speed (a constant vehicle speed) is reached. The set vehicle speed is, for example, a low vehicle speed of about 5 to 7 [km / h]. The set vehicle speed may be settable by the driver.

[0053] In addition, when performing a vehicle behavior of crossing a step on the road surface at the start of the vehicle 100, the moment around the contact point with the step may be large enough to cross the step. For example, the contact point with the wheel can be estimated from the height of the step sensed by the radar 3 or the front camera 4, and the driving torque required to cross the step can be calculated from the straight-ahead force and gravity of the wheel center of gravity around the contact point with the step. In addition, in the running phase described later, the driving torque required to cross the step can be obtained from the momentum of the translational motion and the rotational motion.

[0054] However, in the driving torque control, an upper limit is set for the outputtable driving torque (hereinafter referred to as the upper limit driving torque). This is to prevent the vehicle from overcoming a step (traveling resistance) that should not be overcome. For example, the wheel stopper grounded in the parking lot is an example of a step that should not be overcome.

[0055] The upper limit driving torque is preset in the driving force calculation unit 2. However, when the step sensed by the radar 3 or the front camera 4 is determined to be a step that should not be overcome by image processing, AI (Artificial Intelligence) determination, etc., and it is estimated that the step can be overcome with a driving torque lower than the preset upper limit driving torque, the upper limit driving torque may be automatically updated to a lower value or manually updated by the driver so that the step cannot be overcome.

[0056] When the driving force calculation unit 2 cannot obtain the traveling resistance value by referring to the map, it determines that the traveling resistance has not been detected and proceeds with the process to step S17.

[0057] In step S17, the driving force calculation unit 2 increases the driving torque of the electric motor.

[0058] In step S18, the driving force calculation unit 2 determines whether the vehicle 100 has started moving.

[0059] Based on the detection result of the vehicle speed detection unit 11, when the driving force calculation unit 2 determines that the vehicle 100 has started moving, it proceeds with the process to step S19.

[0060] Based on the detection result of the vehicle speed detection unit 11, when the driving force calculation unit 2 determines that the vehicle 100 has not started moving, it proceeds with the process to step S17.

[0061] In step S19, the driving force calculation unit 2 as a slip detection unit determines whether the wheel is slipping. Specifically, the driving force calculation unit 2 determines that the wheel is slipping when the slip ratio of the wheel is equal to or greater than a predetermined value.

[0062] The slip ratio of the wheel can be estimated, for example, based on the difference between the rotational speed of the wheel and the estimated movement amount of the vehicle 100. The estimated movement amount of the vehicle 100 may be estimated based on the surrounding situation information or may be estimated based on the output torque of the electric motor.

[0063] When the driving force calculation unit 2 determines that the wheel is slipping, it reduces the driving torque and stops the driving torque control (step S20). Thereby, in a situation where it is difficult to control the vehicle speed, the driving torque control can be quickly stopped.

[0064] In addition, the driving force calculation unit 2 causes the display of the navigation system 6 or the instrument panel to display that the driving torque control is in a stopped state. Thereby, it is possible to convey to the driver that the driving torque control has not stopped due to a failure.

[0065] When the driving force calculation unit 2 determines that the wheel is not slipping, it proceeds to step S21 and starts the processing in the driving phase.

[0066] Hereinafter, the driving phase will be described with reference to FIG. 4.

[0067] In step S22, the driving force calculation unit 2 determines whether the accelerator pedal or the brake pedal is being operated.

[0068] When the accelerator is on or the brake is on, the driving force calculation unit 2 determines that the accelerator pedal or the brake pedal is being operated and proceeds to step S29.

[0069] In step S29, the driving force calculation unit 2 stops the driving torque control. This can prevent the driving torque control from interfering with the driver's driving operation.

[0070] Also, in step S29, the driving force calculation unit 2 causes the display of the navigation system 6 and the instrument panel to display that the driving torque control is in a stopped state. This can inform the driver that the driving torque control has not stopped due to a failure.

[0071] When the accelerator is off and the brake is off, the driving force calculation unit 2 determines that neither the accelerator pedal nor the brake pedal is being operated and proceeds with the process to step S23.

[0072] In step S23, the driving force calculation unit 2, which serves as the running resistance detection unit and the obstacle detection unit, performs a running resistance detection process and an obstacle detection process.

[0073] In the running resistance detection process, similar to step S14, the running resistance is detected. Also, in the obstacle detection process, based on the surrounding situation information, obstacles such as walls are detected.

[0074] In step S24, the driving force calculation unit 2 determines whether the running resistance in front of the traveling direction of the vehicle 100 is a running resistance that should not be overcome (necessity of overcoming the running resistance).

[0075] The running resistance in front of the traveling direction of the vehicle 100 is a running resistance (such as a step) that is estimated to be located on the traveling lane on which the vehicle 100 will travel based on the past traveling trajectory of the vehicle 100 until the running resistance detection process is executed in step S23. The step located on the traveling lane on which the vehicle 100 will travel can have its running resistance determined by estimating the contact point between the step and the wheel. Then, the driving torque required to overcome the running resistance can be obtained from the momentum of the translational motion and the rotational motion.

[0076] As described above, in the driving torque control, the upper limit driving torque is set in advance. When the driving torque required to overcome the running resistance in front of the traveling direction of the vehicle 100 exceeds the upper limit driving torque, the driving force calculation unit 2 determines that the running resistance is a running resistance that should not be overcome.

[0077] Also, as described above, the driving force calculation unit 2 can determine whether the running resistance detected based on the surrounding situation information is a running resistance that should not be overcome by image processing, AI determination, etc. In addition, when the running resistance in front of the traveling direction of the vehicle 100 is determined to be a running resistance that should not be overcome by image processing, AI determination, etc., and it is estimated that the running resistance can be overcome with a driving torque lower than the preset upper limit driving torque, the upper limit driving torque may be automatically updated to a lower value or manually updated by the driver so that the running resistance cannot be overcome.

[0078] When the driving force calculation unit 2 determines that the running resistance in front of the traveling direction of the vehicle 100 is a running resistance that should not be overcome (not to be overcome), the driving torque is decreased and the driving torque control is stopped (step S29). Thereby, it is possible to prevent the vehicle 100 from overcoming a running resistance that should not be overcome (such as wheel locking).

[0079] In addition, the driving force calculation unit 2 causes the display of the navigation system 6 and the instrument panel to display that the driving torque control is in a stopped state. Thereby, it is possible to inform the driver that the driving torque control is not stopped due to a failure.

[0080] In step S25, the driving force calculation unit 2 determines whether there is an obstacle in front of the traveling direction of the vehicle 100.

[0081] When an obstacle is detected in front of the vehicle 100 in the traveling direction by the obstacle detection process, the driving force calculation unit 2 reduces the driving torque to reduce the vehicle speed and stops the driving torque control (step S29). Thereby, a sense of security can be given to the driver.

[0082] In addition, the driving force calculation unit 2 causes the display of the navigation system 6 and the instrument panel to display that the driving torque control is in a stopped state. Thereby, it is possible to convey to the driver that the driving torque control is not stopped due to a failure.

[0083] When an obstacle is detected in front of the vehicle 100 in the traveling direction by the obstacle detection process, the driving force calculation unit 2 may gradually reduce the driving torque when the distance from the vehicle 100 to the obstacle becomes equal to or less than a predetermined distance.

[0084] When an obstacle is not detected in front of the vehicle 100 in the traveling direction by the obstacle detection process, the driving force calculation unit 2 advances the process to step S26.

[0085] In step S26, the driving force calculation unit 2 as a driving torque control unit controls the driving torque so as to reach a preset set vehicle speed (constant vehicle speed). Specifically, based on the running resistance detected by the running resistance detection process and the difference between the set vehicle speed and the actual vehicle speed, the insufficient or excessive driving torque is added or subtracted to make the vehicle speed reach the preset set vehicle speed. The set vehicle speed is, for example, a low vehicle speed of about 5 to 7 [km / h]. The set vehicle speed may be settable by the driver.

[0086] In step S27, the driving force calculation unit 2 determines whether or not the vehicle 100 is traveling (vehicle speed > 0 [km / h]).

[0087] When the vehicle speed is not 0 [km / h], the driving force calculation unit 2 determines that the vehicle 100 is traveling and advances the process to step S22.

[0088] When the vehicle speed is 0 [km / h], the driving force calculation unit 2 determines that the vehicle 100 is stopped and proceeds with the process to step S28.

[0089] In step S28, the driving force calculation unit 2, which serves as a slip detection unit, determines whether the wheels are slipping. Specifically, the driving force calculation unit 2 determines that the wheels are slipping when the slip ratio of the wheels is equal to or greater than a predetermined value.

[0090] When the driving force calculation unit 2 determines that the wheels are slipping, it reduces the driving torque and stops the driving torque control (step S29). As a result, in a situation where it is difficult to control the vehicle speed, the driving torque control can be quickly stopped.

[0091] In addition, the driving force calculation unit 2 causes the display of the navigation system 6 and the instrument panel to display that the driving torque control is in a stopped state. This can inform the driver that the driving torque control has not stopped due to a failure.

[0092] As described above, in the present embodiment, the driving force calculation unit 2 detects the running resistance and controls the driving torque at the time of releasing the accelerator so that the vehicle speed becomes constant based on the detected running resistance.

[0093] According to this, when crossing a running resistance (such as a step), the driver can control the vehicle 100 only by operating the brake, so that fine accelerator operations and quick brake operations are not required. Therefore, the driver can stably operate the vehicle 100.

[0094] In addition, in the present embodiment, the driving force calculation unit 2 detects an obstacle in front of the traveling direction of the vehicle 100, and when an obstacle is detected, it reduces the driving torque at the time of releasing the accelerator to reduce the vehicle speed.

[0095] According to this, a sense of security can be given to the driver.

[0096] In addition, in the present embodiment, the driving force calculation unit 2 detects wheel slip, and when wheel slip is detected, it reduces the driving torque when the accelerator is off.

[0097] According to this, in a situation where it is difficult to control the vehicle speed, the driving torque control can be promptly stopped.

[0098] In addition, in the present embodiment, the driving force calculation unit 2 determines whether it is necessary to overcome the detected running resistance, and when it is determined that it is not necessary to overcome the running resistance, it reduces the driving torque when the accelerator is off.

[0099] According to this, it is possible to prevent the vehicle 100 from overcoming a running resistance (such as wheel locking) that should not be overcome.

[0100] In addition, in the present embodiment, the driving force calculation unit 2 specifies a step on the driving lane based on the past driving trajectory, and estimates the contact point between the step and the wheel to detect the running resistance.

[0101] According to this, since the change in the running resistance during the running of the vehicle 100 can be appropriately detected, the vehicle speed can be accurately controlled.

[0102] As described above, the embodiments of the present invention have been described, but the above embodiments merely show one application example of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

Explanation of Reference Numerals

[0103] 2 Driving force calculation unit (vehicle control device, running resistance detection unit, driving torque control unit) 100 Vehicle

Claims

1. A vehicle control method for controlling a vehicle that outputs driving torque when the driver releases the accelerator, comprising: detecting running resistance; controlling the driving torque at the time of accelerator-off so that the vehicle speed becomes constant based on the detected running resistance. A vehicle control method.

2. The vehicle control method according to Claim 1, comprising: detecting an obstacle in front of the traveling direction of the vehicle; when the obstacle is detected, reducing the driving torque at the time of accelerator-off to reduce the vehicle speed. A vehicle control method.

3. The vehicle control method according to Claim 1 or 2, comprising: detecting wheel slip; when the wheel slip is detected, reducing the driving torque at the time of accelerator-off. A vehicle control method.

4. The vehicle control method according to Claim 1, comprising: determining whether it is necessary to overcome the detected running resistance; when it is determined that it is not necessary to overcome the running resistance, reducing the driving torque at the time of accelerator-off. A vehicle control method.

5. The vehicle control method according to Claim 1, comprising: identifying a step on the driving lane based on a past driving trajectory and estimating a contact point between the step and the wheel to detect the running resistance. A vehicle control method.

6. A vehicle control device for controlling a vehicle that outputs driving torque when the driver releases the accelerator, comprising: a running resistance detection unit that detects running resistance; a driving torque control unit that controls the driving torque at the time of accelerator-off so that the vehicle speed becomes constant based on the running resistance detected by the running resistance detection unit. A vehicle control device comprising the above.

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