WO2024048739A1

WO2024048739A1 - Driving assistance device

Info

Publication number: WO2024048739A1
Application number: PCT/JP2023/031866
Authority: WO
Inventors: 真由山本; 真子野口
Original assignee: 株式会社アドヴィックス
Priority date: 2022-08-31
Filing date: 2023-08-31
Publication date: 2024-03-07
Also published as: JP2024033873A

Abstract

An execution device 62 of a driving assistance device 60 derives a reference drive force, which is a drive force required to increase the vehicle speed of a vehicle 10 to at least a target vehicle speed, on the basis of the gradient of a road surface on which the vehicle 10 is positioned and/or the weight of the vehicle 10. From the time at which the vehicle 10 is stopped, the execution device 62 starts a holding control by which a drive force instruction value is held at the reference drive force, and when the vehicle 10 does not start by executing the holding control, the execution device ends the holding control and increases the drive force instruction value beyond the reference drive force. When the vehicle 10 is traveling, the execution device 62 adjusts a braking force instruction value by a feedback control which is based on the deviation between the vehicle speed and the target vehicle speed.

Description

Driving support device

The present invention relates to a driving support device that supports vehicle operation by a vehicle driver.

Patent Document 1 discloses a parking support device that supports parking of a vehicle. The device includes a storage unit that stores the driving force of the vehicle at a predetermined position on the travel route of the vehicle to the target parking position when the vehicle is parked at the target parking position by the driver's driving operation. When the device automatically parks the vehicle at the target parking position with the driving force stored in the storage unit, the device controls the vehicle using the driving force stored in the storage unit.

Japanese Patent Application Publication No. 2015-77862

When the vehicle is driven by an assistance function that automatically adjusts the vehicle body speed, if the target value of the vehicle body speed is low, the driving force of the vehicle is not very large. Therefore, if the wheels come into contact with a step or if the slope of the road surface on which the vehicle is running becomes steep, the vehicle may come to a halt.

A driving support device for solving the above problem is a device that adjusts the vehicle speed of a vehicle based on a target vehicle speed. This driving support device uses a reference driving force, which is a driving force of a magnitude necessary to make the vehicle speed equal to or higher than the target vehicle speed, based on either the gradient of the road surface on which the vehicle is located or the weight of the vehicle. Alternatively, a reference driving force derivation unit that derives the reference driving force based on both, and holding control that maintains the driving force of the vehicle at the reference driving force, may be started from when the vehicle is stopped, and the holding control is performed. a driving force command unit that terminates the holding control and increases the driving force of the vehicle to be greater than the reference driving force when the vehicle does not start; and a driving force command unit that increases the vehicle body speed when the vehicle is running. A braking force command unit that adjusts the braking force of the vehicle through feedback control based on the deviation from the target vehicle speed.

The driving support device derives the reference driving force based on either or both of the slope of the road surface and the weight of the vehicle. The driving support device maintains the driving force of the vehicle at the reference driving force by performing holding control from when the vehicle is stopped. Thereby, the driving force of the vehicle when the vehicle is stopped can be increased compared to the case where the driving force is set without considering the slope of the road surface and the weight of the vehicle. As a result, the vehicle can be started early in a travel section where the above-mentioned disturbance exists.

Further, the driving support device increases the driving force of the vehicle to be larger than the reference driving force when the vehicle does not start even if the holding control is performed. Therefore, the vehicle can be started.
Then, when the vehicle starts by adjusting the driving force as described above, the driving support device adjusts the braking force of the vehicle by feedback control based on the deviation. Thereby, even if the driving force of the vehicle is relatively large, the vehicle speed can be adjusted based on the target vehicle speed.

FIG. 1 is a configuration diagram schematically showing a vehicle equipped with a driving support device according to an embodiment. FIG. 2 is a schematic diagram showing how the vehicle travels at low speed toward a parking position. FIG. 3 is a flowchart showing a processing routine executed by the driving support device. FIG. 4 is a timing chart showing changes in various parameters when the vehicle automatically travels at low speed toward the parking position. FIG. 5 is a timing chart for explaining a modification example.

An embodiment of the driving support device will be described below with reference to FIGS. 1 to 4.
FIG. 1 illustrates a portion of a vehicle 10 including a driving assistance device 60. As shown in FIG.
<Vehicle configuration>
The vehicle 10 includes front wheels 11 and rear wheels 12 as wheels. The vehicle 10 includes the same number of friction brakes 20 as wheels, a braking device 30, and a drive device 40. One friction brake 20 is provided for one wheel.

The plurality of friction brakes 20 each include a rotating body 21, a friction part 22, and a wheel cylinder 23. Since the rotating body 21 rotates together with the wheel, the friction brake 20 can apply braking force to the wheel by pressing the friction portion 22 against the rotating body 21. The higher the hydraulic pressure within the wheel cylinder 23, the greater the force that presses the friction portion 22 against the rotating body 21. That is, the higher the hydraulic pressure within the wheel cylinder 23, the greater the braking force applied to the wheel.

The brake device 30 includes a brake actuator 31 and a brake control section 32 that controls the brake actuator 31. The brake actuator 31 is configured to be able to individually adjust the hydraulic pressure within the plurality of wheel cylinders 23.

The brake control unit 32 controls the braking force of the vehicle 10 by operating the brake actuator 31. The brake control unit 32 can communicate with the driving support device 60 via the in-vehicle network. For example, when the brake control unit 32 receives a braking force command value FbR, which is a command value of the braking force of the vehicle 10, from the driving support device 60, the brake control unit 32 operates the brake actuator 31 based on the braking force command value FbR.

The drive device 40 includes a power unit 41 and a drive control section 42 that controls the power unit 41. Power unit 41 has at least one of an engine and an electric motor as a power source for vehicle 10. In vehicle 10 , output torque of power unit 41 is transmitted to front wheels 11 . Note that the output torque of the power unit 41 may be transmitted to at least one of the front wheels 11 and the rear wheels 12.

The drive control unit 42 controls the driving force of the vehicle 10 by operating the power unit 41. The drive control unit 42 can communicate with the driving support device 60 via the in-vehicle network. For example, when the drive control unit 42 receives the driving force instruction value FdR, which is the instruction value of the driving force of the vehicle 10, from the driving support device 60, the drive control unit 42 operates the power unit 41 based on the driving force instruction value FdR.

<Vehicle detection system>
The detection system of the vehicle 10 includes a plurality of sensors. The plurality of sensors include the same number of wheel speed sensors 51 as wheels, longitudinal acceleration sensors 52, and brake switches 53. The plurality of wheel speed sensors 51 each detect the rotational speed of the corresponding wheel. The longitudinal acceleration sensor 52 detects the longitudinal acceleration of the vehicle 10. The brake switch 53 outputs a signal indicating whether or not the driver is operating the brake operating member 15. The brake operation member 15 is, for example, a brake pedal. The rotational speed of the wheel based on the detected value of the wheel speed sensor 51 is referred to as "wheel speed VW." The longitudinal acceleration based on the detected value of the longitudinal acceleration sensor 52 is referred to as "longitudinal acceleration GX." The driver's operation of the brake operation member 15 is also referred to as a "brake operation."

<Driving support device>
The driving support device 60 has a function of supporting the driver's vehicle operation. "Vehicle operation" here includes accelerator operation, braking operation, and steering operation. For example, the driving support device 60 has a support function that allows the vehicle 10 to automatically travel at low speed. Such support functions are used when parking the vehicle 10 at a parking position. The "low-speed running of the vehicle 10" herein refers to running the vehicle 10 at a speed of less than 10 km/h, for example. Furthermore, "automatic driving" refers to traveling of the vehicle 10 in a state where the vehicle speed of the vehicle 10 is adjusted on the vehicle 10 side.

The driving support device 60 includes a processing circuit 61. The processing circuit 61 includes an execution device 62 and a storage device 63. For example, execution device 62 is a CPU. The storage device 63 stores various control programs executed by the execution device 62. The execution device 62 transmits the driving force instruction value FdR to the drive control section 42 and the braking force instruction value FbR to the braking control section 32 when realizing the above support function.

The execution device 62 functions as a reference driving force deriving unit M11, a driving force commanding unit M12, and a braking force commanding unit M13 by executing the control program. The reference driving force deriving unit M11, the driving force commanding unit M12, and the braking force commanding unit M13 are functional units for causing the vehicle 10 to travel at a low speed by the above-mentioned support function.

<Reference driving force derivation section>
The reference driving force deriving unit M11 calculates a reference driving force FdB, which is a driving force of a magnitude necessary to make the vehicle speed VS equal to or higher than the target vehicle speed VSTr, based on the gradient of the road surface on which the vehicle 10 is located and the weight of the vehicle 10. Derived based on. The vehicle speed VS is derived based on at least one of the wheel speeds VW of the plurality of wheels. The target vehicle speed VSTr is set to the above-mentioned speed of less than 10 km/h. For example, the driving force of the vehicle 10 is torque generated by the power unit 41.

The reference driving force deriving unit M11 derives a driving force that increases as the weight of the vehicle 10 increases as the standard driving force FdB. The reference driving force deriving unit M11 derives a larger driving force as the reference driving force FdB when the road surface is an uphill road than when the road surface is not an uphill road. Further, when the road surface is an uphill road, the reference driving force deriving unit M11 preferably derives a driving force that is larger as the slope of the road surface becomes steeper as the reference driving force FdB.

Note that the reference driving force derivation unit M11 can derive the gradient θ of the road surface based on the longitudinal acceleration GX and the time-differentiated value of the vehicle body speed VS. Further, for example, the reference driving force derivation unit M11 can derive the weight WG of the vehicle 10 based on the vehicle weight of the vehicle 10 and the number of passengers on board the vehicle 10. The vehicle weight is the weight of the vehicle 10 itself. The weight WG of the vehicle 10 referred to here is a weight that also takes into account the weight of the occupant.

For example, the reference driving force deriving unit M11 can derive the reference driving force FdB by using the following relational expression (A1).
FdB=FdA+FdX(θ)+FdY(WG)...(A1)
In relational expression (A1), "FdA" increases the vehicle speed VS from 0 (zero) to the target vehicle speed VSTr when the road surface is level and the number of passengers in the vehicle 10 is one. The specified driving force is the driving force that can be used. The specified driving force FdA can be set based on the specifications of the vehicle 10.

In relational expression (A1), "FdX(θ)" is the amount of correction of the driving force according to the slope θ of the road surface. The correction amount FdX(θ) when the slope θ is a value indicating an uphill road is larger than when the slope θ is a value indicating a horizontal road or when the slope θ is a value indicating a downhill road. Even when the gradient θ is a value indicating an uphill road, the larger the degree of inclination of the uphill road indicated by the gradient θ, the larger the correction amount FdX(θ) becomes. For example, the correction amount FdX(θ) can be expressed as “Sin(θ)×KA1”. In this case, "KA1" is a predetermined coefficient.

In the relational expression (Formula 1), “FdY(WG)” is the amount of correction of the driving force according to the weight WG of the vehicle 10. The correction amount FdY(WG) increases as the weight WG increases. For example, the correction amount FdY(WG) can be expressed as "WG×KB1". In this case, "KB1" is a predetermined coefficient.

<Driving force command section>
The driving force command unit M12 starts holding control for holding the driving force command value FdR at the reference driving force FdB from when the vehicle 10 is stopped.

Here, as shown in FIG. 2, a step 101 may exist on the travel route 100 of the vehicle 10. When the above-mentioned holding control is being carried out, if one of the front wheels 11 and rear wheels 12, which is a wheel located in the traveling direction of the vehicle 10, comes into contact with the step 101, the leading wheel will not be able to get over the step 101. The vehicle 10 may not be able to start, or the vehicle 10 that was traveling at low speed may stop. When the vehicle 10 is moving backward as in the example shown in FIG. 2, the rear of the vehicle 10 is the traveling direction of the vehicle 10, so the rear wheels 12 correspond to the leading wheels and the front wheels 11 correspond to the trailing wheels. On the other hand, when the vehicle 10 is moving forward, the forward direction of the vehicle 10 is the traveling direction of the vehicle 10, so the front wheels 11 correspond to the leading wheels and the rear wheels 12 correspond to the trailing wheels.

Therefore, if it is determined that the vehicle 10 will not start even if the holding control is performed, the driving force command unit M12 ends the holding control and makes the driving force command value FdR larger than the reference driving force FdB. For example, the driving force command unit M12 sets the driving force command value FdR based on feedback control using the deviation between the vehicle speed VS and the target vehicle speed VSTr as input. In this case, the driving force command unit M12 may derive the amount of increase in the driving force through the feedback control described above, and set the sum of the reference driving force FdB and the amount of increase as the driving force command value FdR. When the vehicle 10 is stopped, the vehicle speed VS is lower than the target vehicle speed VSTr. Therefore, the driving force command unit M12 can increase the driving force command value FdR from the reference driving force FdB by deriving the driving force command value FdR based on such feedback control.

On the other hand, when the vehicle 10 starts, that is, when the vehicle 10 is running, the driving force command unit M12 maintains the driving force command value FdR at the reference driving force FdB by continuing to perform the holding control.

<Braking force command section>
The braking force command unit M13 adjusts the braking force command value FbR by feedback control based on the deviation between the vehicle body speed VS and the target vehicle body speed VSTr when the vehicle 10 is running while the holding control is being performed. That is, when the vehicle 10 is running, the braking force command unit M13 adjusts the braking force instruction value FbR, thereby maintaining the vehicle body speed VS at the target vehicle body speed VSTr.

On the other hand, if the vehicle 10 is stopped even while the holding control is being performed, the braking force command unit M13 adjusts the braking force command value FbR as follows. That is, when the braking force command unit M13 determines that the driver has the intention to start the vehicle 10 while performing the holding control, the braking force reduction control gradually decreases the braking force command value FbR. Implement. For example, if the vehicle 10 is stopped due to the braking force caused by the driver's braking operation, the braking force command unit M13 determines that the driver has the intention to start the vehicle 10 when the braking operation is released. It is best to determine that there is. Whether or not the braking operation has been released can be determined based on the output signal of the brake switch 53. In this case, in the braking force reduction control, the braking force command unit M13 sets the braking force upon release FbL, which is the braking force applied to the vehicle 10 at the time the braking operation was released, as the braking force instruction value FbR. Then, the braking force command unit M13 gradually decreases the braking force command value FbR toward 0 (zero).

Note that when the braking operation is released as described above, it can also be said that the driver has requested that the vehicle 10 start. Therefore, it can be said that the braking force command unit M13 starts the braking force reduction control when the driver requests that the vehicle 10 start.

<Driving support processing>
With reference to FIG. 3, a processing routine showing a driving support process executed by the execution device 62 when the vehicle 10 is caused to automatically travel at a low speed by the above-mentioned support function will be described.

If the execution device 62 determines that the execution conditions for the support function described above are satisfied, it repeatedly executes this processing routine every predetermined control cycle. For example, the execution device 62 detects when the driver performs an operation to turn on the above-mentioned support function, and when the driver starts operating the vehicle in order to park the vehicle 10 at a predetermined parking position. In some cases, it is determined that the execution condition is met.

In step S11, the execution device 62 derives the reference driving force FdB by functioning as the reference driving force deriving unit M11. The processing executed by the execution device 62 to derive the reference driving force FdB in this manner is also referred to as "reference driving force derivation processing." After the execution device 62 derives the reference driving force FdB, the execution device 62 moves the process to step S13.

In step S13, the execution device 62 determines whether the vehicle 10 is stopped due to the influence of a disturbance. Specifically, the execution device 62 determines whether the vehicle 10 is stopped based on the vehicle speed VS. When determining that the vehicle 10 is stopped, the execution device 62 determines whether the driver has the intention to start the vehicle 10. For example, if the execution device 62 determines that the driver is not performing a braking operation, it determines that the driver has the intention to start the vehicle 10. On the other hand, if the execution device 62 determines that the driver is performing a braking operation, it determines that the driver does not have the intention to start the vehicle 10. If it is determined that the vehicle 10 is stopped and it is determined that the driver has the intention to start the vehicle 10, it is assumed that the vehicle 10 is stopped due to the influence of the disturbance. On the other hand, if it is determined that the vehicle 10 is stopped and it is determined that the driver does not have the intention to start the vehicle 10, the vehicle 10 is stopped due to the driver's intention. Therefore, it is assumed that the vehicle 10 has not stopped due to the influence of the disturbance. Then, when the execution device 62 determines that the vehicle 10 is stopped due to the influence of the disturbance (S13: YES), the execution device 62 shifts the process to step S17. On the other hand, when the execution device 62 determines that the vehicle 10 is not stopped due to the influence of the disturbance (S13: NO), the execution device 62 shifts the process to step S15. On the other hand, even when the execution device 62 determines that the vehicle 10 is not stopped, it can be determined that the vehicle 10 is not stopped due to the influence of the disturbance (S13: NO), so the process proceeds to step S15. .

In step S15, the execution device 62 performs holding control by functioning as the driving force command unit M12. Specifically, the execution device 62 sets the reference driving force FdB derived in step S11 as the driving force instruction value FdR. However, when switching the control from driving force increase control to holding control, the driving force instruction value FdR is larger than the reference driving force FdB. Therefore, immediately after switching the control from driving force increase control to holding control, the execution device 62 gradually decreases the driving force instruction value FdR from the value at the end of the driving force increase control toward the reference driving force FdB. . After deriving the driving force instruction value FdR, the execution device 62 transmits the driving force instruction value FdR to the drive control unit 42 . The process executed by the execution device 62 in step S15 is also referred to as "driving force retention process." After transmitting the driving force instruction value FdR, the execution device 62 moves the process to step S19.

In step S17, the execution device 62 performs driving force increase control by functioning as the driving force command unit M12. Specifically, the execution device 62 sets a driving force larger than the reference driving force FdB as the driving force instruction value FdR. For example, the execution device 62 derives the control amount through feedback control using the deviation between the vehicle speed VS and the target vehicle speed VSTr as input. Feedback control is, for example, PID control or PI control. The control amount derived by feedback control is also referred to as FB control amount. The execution device 62 derives a larger value as the amount of increase in the driving force as the FB control amount increases. The execution device 62 sets the sum of the increase amount and the reference driving force FdB as the driving force instruction value FdR. Then, the execution device 62 transmits the driving force instruction value FdR to the drive control unit 42. The process executed by the execution device 62 in step S17 is also referred to as "driving force increase process." After transmitting the driving force instruction value FdR, the execution device 62 moves the process to step S19.

In step S19, the execution device 62 determines whether the vehicle 10 is traveling. Specifically, when the vehicle speed VS is greater than 0 (zero), it is assumed that the vehicle 10 is running. On the other hand, if the vehicle speed VS is equal to 0 (zero), it is assumed that the vehicle 10 is not running. When the execution device 62 determines that the vehicle 10 is traveling (S19: YES), the execution device 62 moves the process to step S27. On the other hand, when the execution device 62 determines that the vehicle 10 is not running (S19: NO), the execution device 62 moves the process to step S21.

In step S21, the execution device 62 determines whether the driver has the intention to start the vehicle 10. A method for determining whether or not the driver has the intention to start the vehicle 10 is, for example, the same as the method described in step S13 above. When the execution device 62 determines that the driver has the intention to start the vehicle 10 (S21: YES), the execution device 62 moves the process to step S23. On the other hand, if the execution device 62 determines that the driver does not have the intention to start the vehicle 10 (S21: NO), it temporarily ends this processing routine.

In step S23, the execution device 62 derives the provisional braking force value FbR1 by functioning as the braking force command unit M13. For example, although it was determined that the driver did not have the intention to start the vehicle 10 when this process routine was executed last time, it was determined that the driver did not have the intention to start the vehicle 10 when this process routine was executed this time. If it is determined that this is the case, the execution device 62 sets the above-mentioned brake force upon release FbL as the temporary brake force value FbR1. On the other hand, if it is determined that the driver has the intention to start the vehicle 10 even during the previous execution of this processing routine, the execution device 62 uses the braking force instruction derived during the previous execution of this processing routine. A value obtained by subtracting a predetermined reduced braking force dFb from the value FbR is derived as a tentative braking force value FbR1.

In step S25, the execution device 62 selects the larger of the temporary braking force value FbR1 and 0 (zero) as the braking force command value FbR by functioning as the braking force command unit M13. Then, the execution device 62 transmits the braking force instruction value FbR to the braking control unit 32. In this embodiment, step S23 and step S25 correspond to "braking force reduction control". Furthermore, the series of processes executed by the execution device 62 in steps S23 and S25 is also referred to as a "braking force reduction process." After transmitting the braking force instruction value FbR to the braking control unit 32, the execution device 62 temporarily ends this processing routine.

In step S27, the execution device 62 derives the braking force command value FbR by functioning as the braking force command unit M13. Specifically, the execution device 62 derives the FB control amount through feedback control using the deviation between the vehicle speed VS and the target vehicle speed VSTr as input. Feedback control is, for example, PID control or PI control. The execution device 62 sets the braking force according to the FB control amount as the braking force instruction value FbR. Then, the execution device 62 transmits the braking force instruction value FbR to the braking control unit 32. The process executed by the execution device 62 in step S27 is also referred to as "braking force adjustment process." After transmitting the braking force instruction value FbR, the execution device 62 temporarily ends this processing routine.

<Action and effect>
The operation and effects of the driving support device 60 will be explained with reference to FIGS. 2 and 4.
In this example, the driver performs a braking operation when the rear wheels 12 (leading wheels) contact the step 101 while the vehicle 10 is moving backward, so a braking force is applied to the vehicle 10. As a result, the vehicle 10 stops with the rear wheels 12 in contact with the step 101. In addition, in (C) of FIG. 4, the solid line shows the transition of the braking force FbS applied to the vehicle 10 by the driver's braking operation, while the broken line shows the transition of the braking force instruction value FbR or the braking force instruction value. It shows the transition of the braking force Fb of the vehicle 10 that is controlled according to FbR.

As shown in FIG. 4, before timing t11, the vehicle 10 is stopped because the driver is performing a braking operation. In this case, it can be determined that the vehicle 10 is not stopped due to a disturbance such as the step 101, so the holding control is performed. Therefore, the reference driving force FdB is set as the driving force instruction value FdR. That is, the driving force instruction value FdR is larger than the driving force at idle. For example, if the vehicle 10 is a conventional vehicle that includes only an engine as a power source, the driving force corresponding to the torque of the engine during idling corresponds to the driving force during idling.

In this example, the driver's braking operation is released at timing t11. However, since the rear wheels 12 are in contact with the step 101, the vehicle 10 remains stopped. Then, at timing t12, when it is determined that the vehicle 10 is stopped due to a disturbance such as the step 101, the control is switched from holding control to driving force increase control. As a result, as shown by the broken line in FIG. 4(D), from timing t12, the driving force instruction value FdR is increased from the reference driving force FdB.

When the driving force Fd of the vehicle 10 is increased in accordance with the increase in the driving force instruction value FdR, the rear wheels 12 overcome the step 101 at timing t14. That is, the vehicle 10 starts. When the vehicle 10 starts, the control switches from driving force increase control to holding control. Then, the driving force instruction value FdR is decreased from timing t14 to become the reference driving force FdB.

When the rear wheels 12 get over the step 101, the vehicle speed VS increases. Then, the vehicle speed VS exceeds the target vehicle speed VSTr. Therefore, the braking force command value FbR is derived to suppress the vehicle speed VS from exceeding the target vehicle speed VSTr. As a result, while the holding control is being performed, the vehicle speed VS can be maintained at the target vehicle speed VSTr.

Here, a comparative example in which conventional constant speed control is performed from timing t11 will be described. The "conventional constant speed control" here refers to control in which the driving force during idling is set as the driving force instruction value FdR when the vehicle 10 is stopped. The two-dot chain line in (A) of FIG. 4 shows the transition of the vehicle body speed VS0 in the case of the comparative example. Moreover, the chain double-dashed line in FIG. 4(D) shows the transition of the driving force Fd0 of the vehicle 10 in the case of the comparative example. Since the target vehicle speed VSTr is set to a relatively low vehicle speed, a relatively small value is set as the feedback control gain. Therefore, from timing t11, the driving force instruction value FdR is slowly increased from the driving force at the time of idling. As a result, at timing t15, which is later than timing t13, the driving force Fd0 of the vehicle 10 reaches a driving force that allows the rear wheels 12 to overcome the step 101, so the vehicle 10 starts moving.

On the other hand, in the driving support device 60, the reference driving force FdB, which is larger than the driving force at idle, is applied to the drive from before the timing t11 when it is determined that the driver has the intention to start the vehicle 10. This is set as the force instruction value FdR. This reference driving force FdB is a driving force derived based on the slope θ of the road surface and the weight WG of the vehicle 10. Therefore, after timing t11, the driving force Fd of the vehicle 10 can be quickly increased to the driving force that allows the rear wheels 12 to overcome the step 101. Thereby, even if the vehicle 10 is stopped due to the influence of the step 101, which is an example of a disturbance, the vehicle 10 can be started quickly.

At subsequent timing t16, the front wheel 11, which is the trailing wheel, contacts the step 101. Then, since the vehicle speed VS decreases, the braking force instruction value FbR is decreased by feedback control. As a result, the braking force Fb of the vehicle 10 is reduced while the driving force command value FdR is maintained at the reference driving force FdB, so that the front wheels 11 complete climbing over the step 101. Since the vehicle 10 reaches the target parking position at subsequent timing t17, the driver starts a braking operation. Then, the braking force FbS resulting from the braking operation is applied to the vehicle 10, so the vehicle 10 stops.

Note that the reference driving force FdB is derived every predetermined control cycle. Therefore, if the gradient θ of the road surface changes while the vehicle 10 is running, the reference driving force FdB may also change.
The driving support device 60 can further provide the following effects.

(1) When the vehicle 10 starts moving by increasing the driving force Fd of the vehicle 10 due to the execution of the driving force increasing control, the driving force increasing control is ended and the holding control is started. Thereby, compared to the case where the driving force increase control is continued even after the vehicle 10 starts, it is possible to suppress the braking force Fb applied to the vehicle 10 from increasing in order to maintain the vehicle body speed VS at the target vehicle body speed VSTr. . Therefore, the energy utilization efficiency of the vehicle 10 can be improved.

(2) In the driving support device 60, the driving force Fd of the vehicle 10 is made larger than the driving force during idling before the vehicle 10 starts. Therefore, when the driver's braking operation is released, the vehicle 10 can be started quickly. However, since the driving force Fd of the vehicle 10 is large, if the leading wheels of the vehicle 10 are not in contact with the step 101, there is a risk that the vehicle 10 will suddenly start.

In this regard, in the driving support device 60, when it is determined that the driver has the intention to start the vehicle 10, that is, when it is determined that the driver requests the start of the vehicle 10, the braking force is reduced. Controls are in place. Accordingly, at the time it is determined that the driver has the intention to start the vehicle 10, the braking force Fb is applied to the vehicle 10. Then, the braking force Fb is gradually reduced. Thereby, it is possible to suppress the acceleration of the vehicle 10 from becoming too large when the vehicle 10 starts.

However, the vehicle 10 may start while the braking force instruction value FbR is being reduced by implementing the braking force reduction control. In this case, the driving support device 60 ends the braking force reduction control and starts deriving the braking force instruction value FbR by the feedback control. Thereby, after the vehicle 10 starts, it is possible to suppress the vehicle body speed VS from deviating from the target vehicle body speed VSTr.

(3) The driver can quickly start the vehicle 10 without operating the accelerator when making the wheels go over the step 101. Therefore, stress caused to the driver due to waiting for the vehicle 10 to start can be suppressed. Additionally, the driver's unnecessary accelerator and braking operations can be suppressed.

<Example of change>
The above embodiment can be modified and implemented as follows. The above embodiment and the following modification examples can be implemented in combination with each other within a technically consistent range.

・It is not essential to implement braking force reduction control. For example, when the reference driving force FdB is relatively small, the execution device 62 does not need to perform the braking force reduction control when determining that the driver has the intention to start the vehicle 10. In this case, if the reference driving force FdB is relatively large, the execution device 62 may perform the braking force reduction control when determining that the driver has the intention to start the vehicle 10.

- If the braking force FbS decreases while executing the holding control while the vehicle 10 is stopped due to the driver's braking operation, the execution device 62 decreases the driving force command value FdR from the reference driving force FdB. You may also perform a reduction process upon release. For example, in the release reduction process, the execution device 62 reduces the driving force instruction value FdR from the reference driving force FdB when the driver's braking operation is released. In particular, when the brake is suddenly released such that the rate of decrease in the braking force FbS exceeds a predetermined rate of decrease, it is preferable to decrease the driving force command value FdR by performing a reduction process upon release. While the release reduction process is being executed, the driving force instruction value FdR is set within a predetermined range below the reference driving force FdB and above a predetermined lower limit value FdL that is larger than the driving force during idling. In this case, the driving force Fd reduced by executing the release reduction process is higher than the driving force at idle, so while the holding control continues to have the effect of suppressing the start delay due to steps, etc., the driving force Fd is By decreasing the predetermined amount, it is possible to suppress sudden start of the vehicle 10 when the brake is suddenly released on a level road, a downhill road, or the like.

Here, the cancellation-time reduction process will be explained with reference to FIG. 5. When the braking force FbS starts to decrease rapidly from timing t20, the driving force command value FdR starts to decrease by executing the release decreasing process. Then, since the driving force instruction value FdR reaches the lower limit value FdL at timing t21, the driving force instruction value FdR is maintained at the lower limit value FdL during the period from timing t21 to timing t22. Note that when the release reduction process is executed, as shown in FIG. 5, the braking force reduction control may not be performed. Alternatively, when performing the cancellation-time reduction process, the speed at which the braking force is reduced in the braking force reduction control may be made smaller than usual.

Furthermore, even though it is determined that the driver has the intention to start the vehicle 10 with the driving force instruction value FdR made smaller than the reference driving force FdB by executing the release reduction control. If the vehicle 10 does not start due to a step or the like, the driving force increase control increases the driving force command value FdR to the reference driving force FdB at a return increasing speed that is higher than the normal increasing speed when increasing the driving force Fd. The execution device 62 may execute the release-time return processing to increase the number. In this case, after the driving force instruction value FdR is increased to the reference driving force FdB by the release return process, the execution device 62 increases the driving force at the normal increasing speed by executing the driving force increase control.

Here, the cancellation-time reduction process will be explained with reference to FIG. 5. At timing t22, if it is determined that the vehicle 10 does not start even though it is determined that the driver has the intention to start the vehicle 10, the driving force instruction value FdR is set to the reference value by the cancellation return process. The driving force is increased at an increasing speed for return up to FdB. Then, when the driving force instruction value FdR reaches the reference driving force FdB at timing t23, the reference driving force FdB is increased at the normal increasing speed from timing t23 onwards.

- If the execution device 62 can increase the driving force instruction value FdR in the driving force increase control, it is not necessary to derive the driving force instruction value FdR based on the feedback control. For example, in the driving force increase control, the execution device 62 may increase the driving force instruction value FdR at a predetermined increasing speed.

- When the vehicle 10 starts by increasing the driving force Fd with the implementation of the driving force increase control, the execution device 62 sets the driving force instruction value FdR to the driving force instruction value FdR at the time when the vehicle 10 starts. It may also be retained.

- In the embodiment described above, if the vehicle 10 cannot be started even if the holding control is executed, the holding control is ended and the driving force increasing control is started even if the braking force reduction control is being executed. However, it is not limited to this. For example, even if the holding control is in progress, the holding control may continue to be carried out during a period in which the braking force instruction value FbR is being reduced by the braking force reduction control. In this case, if the vehicle 10 is still stopped even after the reduction of the braking force command value FbR by the braking force reduction control is finished, the execution device 62 ends the holding control and starts the driving force increase control. You can also do this.

- The execution device 62 may derive the reference driving force FdB by also considering information other than the road surface slope θ and the weight WG of the vehicle 10. For example, the execution device 62 may derive the reference driving force FdB based on the amount of steering operation, or may derive the reference driving force FdB based on the outside temperature. The execution device 62 may also derive the reference driving force FdB based on information from the navigation device, or may derive the reference driving force FdB based on the analysis result of an image captured by an imaging device such as a camera. You may.

- The execution device 62 may derive the reference driving force FdB based on either the road surface gradient θ or the weight WG of the vehicle 10. For example, the execution device 62 may derive the reference driving force FdB without using the driving force correction amount FdX(θ) according to the gradient θ. For example, the execution device 62 may derive the reference driving force FdB without using the driving force correction amount FdX(WG) according to the weight WG.

- The execution device 62 may derive the driving force correction amount FdX(θ) according to the road surface slope θ from both the slope θ and the weight WG of the vehicle 10. For example, the correction amount FdX(θ) may be expressed as “Sin(θ)×WG×KA2”. In this case, "KA2" is a predetermined coefficient.

・The target vehicle speed VSTr may be changed when holding control is being performed. For example, when it is determined that the trailing wheels of the vehicle 10 have climbed over the step 101, the target vehicle speed VSTr may be set to a higher vehicle speed than before it was determined that the trailing wheels have climbed over the step 101.

- The support function for automatically driving the vehicle 10 at a low speed described above may be realized even when the vehicle 10 is not parked. In this case, if the execution device 62 performs the driving force increase control at all times when the vehicle stops, the energy efficiency of the vehicle 10 may deteriorate due to the increase in the driving force Fd. Therefore, in a state in which predetermined driving support control is implemented or permitted to be implemented or in a state in which a predetermined driving condition is satisfied, a support function for automatically driving the vehicle at a low speed may be implemented.

- When the vehicle 10 is equipped with an imaging device capable of capturing an image of the road surface on which the vehicle 10 is traveling, the driving support device 60 analyzes the image captured by the imaging device to create a bump 101 on the traveling route of the vehicle 10. It is possible to determine whether or not there is a disturbance such as The disturbance may be a depression in the running road surface or a portion where the road surface gradient changes suddenly. The execution device 62 of the driving support device 60 may operate the above-mentioned support function upon detecting the presence of a disturbance by analyzing an image.

- The processing circuit 61 of the driving support device 60 is not limited to one that includes a CPU and a ROM and executes software processing. That is, the processing circuit 61 may have any of the following configurations (a) to (c).

(a) The processing circuit 61 includes one or more processors that execute various processes according to computer programs. The processor includes a CPU and memory such as RAM and ROM. The memory stores program codes or instructions configured to cause the CPU to perform processes. Memory, or computer-readable media, includes any available media that can be accessed by a general purpose or special purpose computer.

(b) The processing circuit 61 includes one or more dedicated hardware circuits that execute various processes. Dedicated hardware circuits may include, for example, application specific integrated circuits, ie ASICs or FPGAs. Note that ASIC is an abbreviation for "Application Specific Integrated Circuit," and FPGA is an abbreviation for "Field Programmable Gate Array."

(c) The processing circuit 61 includes a processor that executes some of the various processes according to a computer program, and a dedicated hardware circuit that executes the remaining processes of the various processes.

Note that the expression "at least one" used in this specification means "one or more" of the desired options. As an example, the expression "at least one" as used herein means "only one option" or "both of the two options" if the number of options is two. As another example, the expression "at least one" as used herein means "only one option" or "any combination of two or more options" if there are three or more options. means.

Claims

A driving support device that adjusts the vehicle speed of a vehicle based on a target vehicle speed,
Deriving a reference driving force, which is a driving force of a magnitude necessary to make the vehicle speed equal to or higher than the target vehicle speed, based on either or both of the gradient of the road surface on which the vehicle is located and the weight of the vehicle. a reference driving force deriving unit,
A holding control that maintains the driving force of the vehicle at the reference driving force is started when the vehicle is stopped, and if the vehicle does not start even after carrying out the holding control, the holding control is terminated. a driving force command unit that makes the driving force of the vehicle larger than the reference driving force;
A driving support device, comprising: a braking force command unit that adjusts the braking force of the vehicle by feedback control based on a deviation between the vehicle body speed and the target vehicle body speed when the vehicle is running.
The driving support device according to claim 1, wherein the driving force command section maintains the driving force of the vehicle at the reference driving force by performing the holding control when the vehicle starts moving.
When the driving force command unit ends the holding control and makes the driving force of the vehicle larger than the reference driving force, the driving force command unit controls the driving force by feedback control based on the deviation between the vehicle body speed of the vehicle and the target vehicle body speed. The driving support device according to claim 1, which increases the driving force of the vehicle.
The braking force command unit performs braking force reduction control to gradually reduce the braking force of the vehicle when there is a request to start the vehicle while the holding control is being performed. The driving support device according to any one of the above.