Driving assistance device and driving assistance method

Abstract

A driving assistance device (60) is provided with: a memory (101) that stores acceleration characteristics; a request derivation unit (103) that is configured to derive, on the basis of the acceleration characteristics, the acceleration of the vehicle (10) according to the operation amount of an operation member as a requested acceleration; and a command processing unit (105) that is configured to transmit a command value based on the requested acceleration to a driving device (20) and a braking device (30). The command processing unit (105) is further configured such that when the requested acceleration is included in the predetermined acceleration range, the command processing unit (105) derives a driving force command value and braking force command value so as to satisfy the requirements that the driving force command value and the braking force command value both be greater than 0 (zero) and that the difference between the driving force command value and the braking force command value be a value corresponding to the requested acceleration.

Description

Driving assistance device and driving assistance method

[0001] The present disclosure relates to a driving assistance device and a driving assistance method that assist a driver in driving a vehicle.

[0002] Patent Document 1 discloses an example of a traction control device that adjusts the braking force of wheels when a vehicle is traveling off-road.

[0003] Japanese Patent Application Laid-Open No. 2004-90886

[0004] Simultaneous operation, in which both the accelerator pedal and the brake pedal are operated simultaneously, is known as a driving technique for improving a vehicle's off-road performance. Specifically, simultaneous operation is a driving technique in which the driver operates the accelerator pedal with the right foot while operating the brake pedal with the left foot. By performing simultaneous operation, the driver can simultaneously adjust the vehicle's driving force and braking force. However, while skilled, advanced drivers can perform simultaneous operation when driving a vehicle off-road, it is difficult for drivers other than advanced drivers to perform simultaneous operation.

[0005] According to one aspect of the present disclosure, there is provided a driving assistance device applicable to a vehicle. The vehicle includes an operating member operated to adjust the vehicle's acceleration, a drive unit configured to adjust the driving force of the vehicle, and a brake unit configured to adjust the braking force of the vehicle. The driving assistance device includes a memory that stores acceleration characteristics indicating a relationship between an operating amount of the operating member and the acceleration of the vehicle, a demand derivation unit configured to derive a required acceleration of the vehicle corresponding to the operating amount based on the acceleration characteristics, and a command processing unit configured to transmit a command value corresponding to the required acceleration to the driving unit and the brake unit. When the required acceleration is within a predetermined acceleration range, the command processing unit is further configured to derive the driving force command value and the braking force command value so that both are greater than zero and the difference between the driving force command value and the braking force command value is a value corresponding to the required acceleration.

[0006] According to another aspect of the present disclosure, there is provided a driving assistance method applicable to a vehicle. The vehicle includes an operating member operated to adjust the acceleration of the vehicle, a drive device configured to adjust the driving force of the vehicle, and a braking device configured to adjust the braking force of the vehicle. The driving assistance method includes deriving, as a required acceleration, an acceleration of the vehicle corresponding to an operating amount of the operating member based on an acceleration characteristic indicating a relationship between the operating amount of the operating member and the acceleration of the vehicle, deriving a command value corresponding to the required acceleration, and transmitting the command value corresponding to the required acceleration to the operating device and the braking device. Deriving the command value corresponding to the required acceleration includes deriving the driving force command value and the braking force command value so that, when the required acceleration is within a predetermined acceleration range, both the driving force command value and the braking force command value are greater than 0 (zero) and the difference between the driving force command value and the braking force command value is a value corresponding to the required acceleration.

[0007] FIG. 1 is a schematic diagram showing a configuration of a vehicle equipped with a driving assistance device of an embodiment. FIG. 2 is a block diagram showing the functional configuration of the driving assistance device of FIG. 1. FIG. 3 is a flowchart showing a series of processes executed by a processing circuit of the driving assistance device of FIG. 1. FIG. 4 is a schematic diagram showing a state in which the vehicle of FIG. 1 stopped on an uphill road is started. FIG. 5 is a timing chart for starting the vehicle of FIG. 1 stopped on an uphill road. FIG. 6 is a schematic diagram showing a state in which the vehicle of FIG. 1 is stopped on a downhill road. FIG. 7 is a timing chart for stopping the vehicle of FIG. 1 on a downhill road. FIG. 8 is a diagram showing a modified example of the acceleration characteristics map shown in FIG. 2. FIG. 9 is a diagram showing an example of an acceleration characteristics map in another modified example in which the vehicle is equipped with an operation member dedicated to the acceleration / deceleration operation mode.

[0008] An embodiment of a driving assistance device and a driving assistance method will be described below with reference to Figures 1 to 7. <General Configuration of Vehicle> Figure 1 shows an outline of a vehicle 10 equipped with a driving assistance device 60. The vehicle 10 is equipped with an accelerator pedal 11, a brake pedal 12, a drive device 20, a braking device 30, multiple types of sensors, and a switching operation unit 50.

[0009] The drive device 20 adjusts the drive force Fd of the vehicle 10. The drive device 20 includes a power unit 21 and a drive control unit 22 that controls the power unit 21. The power unit 21 has at least one of an engine and a drive motor. An example of the drive control unit 22 is an electronic control device. The drive control unit 22 controls the drive force Fd of the vehicle 10 by operating the power unit 21. The drive control unit 22 is also configured to be able to send and receive various information and commands to and from the driving assistance device 60 via an in-vehicle network.

[0010] The braking device 30 adjusts the braking force Fb of the vehicle 10. The braking device 30 includes a braking actuator 31 and a braking control unit 32 that controls the braking actuator 31. An example of the braking control unit 32 is an electronic control device. The braking control unit 32 controls the braking force Fb of the vehicle 10 by operating the braking actuator 31. The braking control unit 32 is also configured to be able to send and receive various information and commands to and from the driving assistance device 60 via an in-vehicle network.

[0011] <Sensors> The plurality of sensors output detection signals according to the detection results to the driving assistance device 60. The vehicle 10 is equipped with sensors including an operation-related sensor that detects information related to the driver's operation and a state quantity detection sensor that detects a state quantity of the vehicle 10.

[0012] The operation-related sensors include an accelerator sensor 41 and a brake sensor 42. The accelerator sensor 41 detects the amount of operation of the accelerator pedal 11 by the driver. The brake sensor 42 detects the amount of operation of the brake pedal 12 by the driver. The brake sensor may be a sensor that detects the operating force of the brake pedal 12 by the driver or a correlation value thereof. Hereinafter, the operation amount based on the detection signal of the accelerator sensor 41 will be referred to as "accelerator opening degree AC." The operation amount based on the detection signal of the brake sensor 42 will be referred to as "braking operation amount BP."

[0013] The state quantity detection sensors include a longitudinal acceleration sensor 44, a lateral acceleration sensor 45, and a wheel speed sensor 46. The longitudinal acceleration sensor 44 detects the acceleration of the vehicle 10 in the longitudinal direction. The lateral acceleration sensor 45 detects the acceleration of the vehicle 10 in the lateral direction. A wheel speed sensor 46 is provided for each wheel of the vehicle 10. The wheel speed sensor 46 detects the rotational speed of the corresponding wheel. Hereinafter, the acceleration based on the detection signal of the longitudinal acceleration sensor 44 will be referred to as "longitudinal acceleration Gx." The acceleration based on the detection signal of the lateral acceleration sensor 45 will be referred to as "lateral acceleration Gy." The rotational speed based on the detection signal of the wheel speed sensor 46 will be referred to as "wheel speed VW."

[0014] <Switching Operation Unit> The switching operation unit 50 is an operation unit that switches the operation mode of the vehicle 10. The vehicle 10 has operation modes including a normal operation mode and an acceleration / deceleration operation mode. When the normal operation mode is selected, the driving force Fd of the vehicle 10 is adjusted by operating the accelerator pedal 11, while the braking force Fb of the vehicle 10 is adjusted by operating the brake pedal 12. When the acceleration / deceleration operation mode is selected, both the driving force Fd and the braking force Fb of the vehicle 10 can be adjusted by operating the accelerator pedal 11. In other words, when the acceleration / deceleration operation mode is selected, the accelerator pedal 11 functions as an "operating member" that is operated to adjust the acceleration of the vehicle 10.

[0015] The normal operation mode or the acceleration / deceleration operation mode can be selected by an occupant of the vehicle 10, such as a driver, operating the switching operation unit 50. The switching operation unit 50 transmits information about the selected operation mode to the driving assistance device 60.

[0016] <Driving Assistance Device> The driving assistance device 60 assists the driver in driving the vehicle 10. The driving assistance device 60 includes a processing circuit 61. An example of the processing circuit 61 is an electronic control device. In this case, the processing circuit 61 includes a CPU 62, a first memory 63, and a second memory 64. The first memory 63 stores a control program executed by the CPU 62 and various maps referenced by the CPU 62. The second memory 64 stores the results of calculations by the CPU 62. As will be described in more detail below, a portion of the storage area of ​​the first memory 63 functions as a "memory" that stores acceleration characteristics that indicate the relationship between the accelerator opening AC, which is the amount of operation of the accelerator pedal 11 by the driver, and the acceleration DVS of the vehicle 10.

[0017] The CPU 62 executes the control program stored in the first memory 63, causing the processing circuit 61 to function as various functional units for assisting the driver in operating the vehicle. Fig. 2 shows the functional units that operate when the acceleration / deceleration operation mode is selected. The functional units include a storage unit 101, which is a memory, as well as a request derivation unit 103 and a command processing unit 105.

[0018] <Storage Unit> The storage unit 101 stores an acceleration characteristics map MP1 as an acceleration characteristic that indicates the relationship between the accelerator opening AC and the acceleration DVS of the vehicle 10. When the vehicle 10 accelerates, the acceleration DVS takes a positive value. On the other hand, when the vehicle 10 decelerates, the acceleration DVS takes a negative value.

[0019] In the acceleration characteristics map MP1, the greater the accelerator opening AC, the greater the acceleration DVS. Specifically, the reference opening ACb is set to an accelerator opening AC greater than 0 (zero). When the accelerator opening AC is equal to the reference opening ACb, the acceleration DVS is 0 (zero). When the accelerator opening AC is less than the reference opening ACb, the acceleration DVS is a negative value. When the accelerator opening AC is greater than the reference opening ACb, the acceleration DVS is a positive value.

[0020] <Demand Derivation Unit> The demand derivation unit 103 derives the acceleration DVS corresponding to the accelerator pedal position AC as the demand acceleration DVSRq of the vehicle 10 based on the acceleration characteristics map MP1. The demand acceleration DVSRq is a demand value of the acceleration DVS for the vehicle 10. The demand derivation unit 103 reads out the acceleration DVS corresponding to the accelerator pedal position AC from the acceleration characteristics map MP1. Then, the demand derivation unit 103 sets the acceleration DVS read out from the acceleration characteristics map MP1 as the demand acceleration DVSRq.

[0021] <Command Processing Unit> The command processing unit 105 derives at least one of a command driving force FdTr and a command braking force FbTr based on the required acceleration DVSRq. The command driving force FdTr is a command value of the driving force Fd. The command braking force FbTr is a command value of the braking force Fb.

[0022] Then, the command processing unit 105 transmits the derived command value to the drive device 20 and the braking device 30. Specifically, when the command processing unit 105 derives the command driving force FdTr, it transmits the command driving force FdTr to the drive control unit 22 of the drive device 20. When the command processing unit 105 derives the command braking force FbTr, it transmits the command braking force FbTr to the braking control unit 32 of the braking device 30.

[0023] When the drive control unit 22 receives the command drive force FdTr, it operates the power unit 21 so that the drive force Fd becomes the command drive force FdTr. When the brake control unit 32 receives the command braking force FbTr, it operates the brake actuator 31 so that the braking force Fb becomes the command braking force FbTr.

[0024] For example, the command processing unit 105 derives at least one of the command driving force FdTr and the command braking force FbTr based on a command value derivation map MP2. In the command value derivation map MP2 shown in FIG. 2, the longitudinal force Fx corresponding to the required acceleration DVSRq is indicated by a dashed line. The longitudinal force Fx is the value obtained by subtracting the braking force Fb from the driving force Fd. Therefore, when the driving force Fd is equal to the braking force Fb, the longitudinal force Fx becomes 0 (zero). When the driving force Fd is greater than the braking force Fb, the longitudinal force Fx becomes a positive value. When the driving force Fd is smaller than the braking force Fb, the longitudinal force Fx becomes a negative value. According to the command value derivation map MP2, the longitudinal force Fx becomes larger as the required acceleration DVSRq becomes larger.

[0025] A predetermined acceleration range RDVS is set in the command value derivation map MP2. The acceleration range RDVS is a range of acceleration DVS that includes 0 (zero). For example, the width of the acceleration range RDVS and the upper and lower limits of the acceleration range RDVS are preset ranges.

[0026] When the required acceleration DVSRq is smaller than the lower limit value of the acceleration range RDVS, the command processing unit 105 derives the absolute value of the longitudinal force Fx corresponding to the required acceleration DVSRq as the command braking force FbTr. In this case, the command processing unit 105 derives 0 (zero) as the command driving force FdTr. When the required acceleration DVSRq is greater than the upper limit value of the acceleration range RDVS, the command processing unit 105 derives the longitudinal force Fx corresponding to the required acceleration DVSRq as the command driving force FdTr. In this case, the command processing unit 105 derives 0 (zero) as the command braking force FbTr.

[0027] When the required acceleration DVSRq is included in the acceleration range RDVS, the command processing unit 105 derives the command driving force FdTr and the command braking force FbTr so as to satisfy the following conditions (A1) and (A2).

[0028] (A1) Both the command driving force FdTr and the command braking force FbTr are greater than 0 (zero). (A2) The difference between the command braking force FbTr and the command braking force FbTr is equal to the longitudinal force Fx corresponding to the required acceleration DVSRq.

[0029] Specifically, when the required acceleration DVSRq is within the acceleration range RDVS and is greater than 0 (zero), the command processing unit 105 derives the command driving force FdTr and the command braking force FbTr so that the command driving force FdTr is greater than the command braking force FbTr. Furthermore, when the required acceleration DVSRq is within the acceleration range RDVS and is less than 0 (zero), the command processing unit 105 derives the command driving force FdTr and the command braking force FbTr so that the command braking force FbTr is greater than the command driving force FdTr.

[0030] When the required acceleration DVSRq is within the acceleration range RDVS, the braking gradient, which is the amount of change in the command braking force FbTr with respect to a change in the required acceleration DVSRq, is the same as the driving gradient, which is the amount of change in the command driving force FdTr with respect to a change in the required acceleration DVSRq. In the example shown in Figure 2, when the required acceleration DVSRq is within the acceleration range RDVS, both the braking gradient and the driving gradient are constant regardless of the required acceleration DVSRq. However, the braking gradient and the driving gradient may change depending on the required acceleration DVSRq.

[0031] <Driving Assistance Processing> The driving assistance processing, which is a series of processing executed by the processing circuit 61 when the acceleration / deceleration operation mode is selected, will be described with reference to Fig. 3. The processing circuit 61 repeatedly executes the driving assistance processing at predetermined control intervals.

[0032] In step S11, the processing circuit 61 determines whether the acceleration / deceleration operation mode has been selected as the operation mode. If the acceleration / deceleration operation mode has not been selected (S11: NO), the processing circuit 61 temporarily terminates the driving assistance process. On the other hand, if the processing circuit 61 determines that the acceleration / deceleration operation mode has been selected (S11: YES), the processing circuit 61 proceeds to step S13.

[0033] In step S13, the processing circuit 61 acquires the accelerator pedal position AC as the amount of operation of the operating member. In the following step S15, the processing circuit 61 functions as the demand derivation unit 103 to acquire the acceleration DVS corresponding to the accelerator pedal position AC based on the acceleration characteristics map MP1 stored in the first memory 63. The processing circuit 61 then derives the acquired acceleration DVS as the demand acceleration DVSRq.

[0034] In the next step S17, the processing circuit 61 functions as the command processing unit 105 to derive a command driving force FdTr and a command braking force FbTr according to the required acceleration DVSRq. At this time, the processing circuit 61 derives the command driving force FdTr and the command braking force FbTr based on the command value derivation map MP2. Then, in step S19, the processing circuit 61 functions as the command processing unit 105 to transmit the command driving force FdTr to the drive control unit 22 of the drive device 20. The processing circuit 61 transmits the command braking force FbTr to the braking control unit 32 of the braking device 30. Thereafter, the processing circuit 61 temporarily ends the driving assistance process.

[0035] <Operations and Effects of the Present Embodiment> The operations and effects when the vehicle 10 travels on an off-road uphill road will be described with reference to Figures 4 and 5. Here, the case where the acceleration / deceleration operation mode is selected is the example, and the case where the normal operation mode is selected is the first comparative example. In Figures 5A to 5C, the solid lines indicate the changes in vehicle speed VS, driving force Fd, and braking force Fb in the example. Meanwhile, in Figures 5A to 5C, the two-dot chain lines indicate the changes in vehicle speed VS, driving force Fd, and braking force Fb in the first comparative example. Figure 5D shows the changes in accelerator opening AC in the example.

[0036] As shown in FIG. 5 , in this embodiment, the accelerator pedal 11 is not operated before timing t11. That is, the accelerator opening AC is 0 (zero). Therefore, in this embodiment, the processing circuit 61 derives 0 (zero) as the command driving force FdTr and a value greater than 0 (zero) as the command braking force FbTr. The processing circuit 61 then transmits this command braking force FbTr to the brake control unit 32. Therefore, the brake actuator 31 is operated based on this command braking force FbTr. As a result, a braking force Fb is applied to the vehicle 10, and the vehicle 10 is maintained in a stopped state.

[0037] In the first comparative example, the driver operates the brake pedal 12 to apply a braking force Fb to the vehicle 10. This maintains the stopped state of the vehicle 10. At timing t11 while the vehicle 10 is stopped, the driver starts a vehicle operation to start the vehicle 10.

[0038] In the first comparative example, the driver releases the brake pedal 12 and then begins to operate the accelerator pedal 11. That is, the driver begins to release the brake pedal 12 at timing t11, and then begins to operate the accelerator pedal 11 at timing t12. As shown by the two-dot chain lines in Figures 5B and 5C, a time lag occurs between when the braking force Fb becomes zero and when the driving force Fd begins to increase. During this time lag, no force is acting on the vehicle 10 to prevent it from rolling backward. Therefore, the vehicle 10 temporarily rolls backward, as shown in Figures 5A and 4. In this case, the driver panics and operates the accelerator pedal 11, which tends to increase the rate at which the accelerator pedal depression angle AC increases. As a result, when the vehicle 10 starts to move forward, the acceleration DVS of the vehicle 10 tends to increase, as shown in Figure 5A.

[0039] In contrast, in this embodiment, because the acceleration / deceleration operation mode is selected, the driver can adjust the braking force Fb and the driving force Fd by operating the accelerator pedal 11 without operating the brake pedal 12. That is, when operation of the accelerator pedal 11 begins at timing t11, the processing circuit 61 reduces the command braking force FbTr in accordance with an increase in the accelerator opening AC. The braking control unit 32 operates the brake actuator 31 based on this command braking force FbTr, thereby reducing the braking force Fb.

[0040] At time t12, while the braking force Fb is still being applied to the vehicle 10, the required acceleration DVSRq corresponding to the accelerator pedal position AC falls within the acceleration range RDVS. Therefore, the processing circuit 61 decreases the command braking force FbTr and increases the command driving force FdTr in response to an increase in the accelerator pedal position AC. The processing circuit 61 then transmits the command braking force FbTr to the brake control unit 32 and the command driving force FdTr to the driving control unit 22. Therefore, while the braking force Fb is being applied to the vehicle 10, the driving force Fd of the vehicle 10 begins to increase. On an uphill road, the driving force Fd acts on the vehicle 10 to prevent the vehicle 10 from rolling downhill. Therefore, even if the braking force Fb is reduced, the increased driving force Fd prevents the vehicle 10 from rolling downhill.

[0041] Then, at timing t13, when the longitudinal force Fx increases in accordance with an increase in the driving force Fd and a decrease in the braking force Fb, the vehicle 10 starts moving. In other words, the driving assistance device 60 can start the vehicle 10 after preventing the vehicle 10, which has stopped on an uphill off-road road, from sliding down the slope. Therefore, the driving assistance device 60 can improve the off-road running performance of the vehicle 10.

[0042] Note that even after the vehicle 10 starts moving, as long as the required acceleration DVSRq remains within the acceleration range RDVS, the processing circuit 61 decreases the commanded braking force FbTr and increases the commanded driving force FdTr in response to an increase in the required acceleration DVSRq. In the example shown in FIG. 5 , the required acceleration DVSRq leaves the acceleration range RDVS at time t14, so the processing circuit 61 derives 0 (zero) as the commanded braking force FbTr. This prevents the braking force Fb from being applied to the vehicle 10 while it is moving. Therefore, from time t14 onward, the driver can drive the vehicle 10 without feeling any drag caused by the braking force Fb.

[0043] The operation and effect of stopping the vehicle 10 traveling on an off-road downhill road will be described with reference to Figures 6 and 7. Here, the acceleration / deceleration operation mode is selected in the example, and the normal operation mode is selected in the second comparative example. In Figures 7A to 7C, the solid lines indicate the changes in vehicle speed VS, driving force Fd, and braking force Fb in the example. In Figures 7A to 7C, the two-dot chain lines indicate the changes in vehicle speed VS, driving force Fd, and braking force Fb in the second comparative example. Figure 7D shows the changes in accelerator pedal position AC in the example.

[0044] As shown in Figure 7, in this embodiment, before timing t21, the driver operates the accelerator pedal 11, causing the vehicle 10 to travel downhill. Therefore, in this embodiment, the processing circuit 61 derives 0 (zero) as the command braking force FbTr and a value greater than 0 (zero) as the command driving force FdTr. The processing circuit 61 then transmits this command driving force FdTr to the drive control unit 22. Therefore, the power unit 21 is operated based on this command driving force FdTr, causing the vehicle 10 to travel.

[0045] In the example shown in FIG. 7 , the driver initiates a vehicle operation to stop the vehicle 10 at timing t21. In the second comparative example, the driver releases the accelerator pedal 11 and then begins to operate the brake pedal 12. That is, the driver begins to release the accelerator pedal 11 at timing t21, and then begins to operate the brake pedal 12 at timing t24. As shown by the two-dot chain lines in FIGS. 7B and 7C , a time lag occurs between when the driving force Fd becomes zero and when the braking force Fb begins to increase. During this time lag, no force is acting on the vehicle 10 to decelerate it. Therefore, the vehicle 10 does not decelerate, as shown in FIGS. 7A and 6 . In this case, the driver panics and operates the brake pedal 12. Then, when the braking force Fb becomes sufficiently large, the vehicle 10 stops on a downhill road. That is, in the second comparative example, the vehicle 10 may stop after the vehicle speed VS, which is the traveling speed of the vehicle 10, temporarily increases. Furthermore, a large time lag occurs between the time when the vehicle operation to stop the vehicle 10 is started and the time when the vehicle 10 actually stops.

[0046] In contrast, in this embodiment, because the acceleration / deceleration operation mode is selected, the driver can adjust the braking force Fb and the driving force Fd by operating the accelerator pedal 11 without operating the brake pedal 12. That is, when the accelerator opening AC is reduced by operating the accelerator pedal 11 from timing t21, the processing circuit 61 reduces the command driving force FdTr in accordance with the reduction in accelerator opening AC. The drive control unit 22 operates the power unit 21 based on this command driving force FdTr, and the driving force Fd is reduced.

[0047] At time t22 while the driving force Fd is still being applied to the vehicle 10, the required acceleration DVSRq corresponding to the accelerator pedal position AC falls within the acceleration range RDVS. Therefore, the processing circuit 61 decreases the commanded driving force FdTr and increases the commanded braking force FbTr in response to a decrease in the accelerator pedal position AC. The processing circuit 61 then transmits this commanded braking force FbTr to the brake control unit 32 and also transmits this commanded driving force FdTr to the drive control unit 22. Then, while the driving force Fd is being applied to the vehicle 10, the braking force Fb of the vehicle 10 begins to increase.

[0048] After timing t22, the braking force Fb is increased in response to a decrease in the accelerator pedal position AC. Therefore, as shown in FIG. 7A, the increase in vehicle speed VS is suppressed compared to the second comparative example. Then, at timing t23, the required acceleration DVSRq reaches the lower limit of the acceleration range RDVS, and therefore, after timing t23, the processing circuit 61 derives 0 (zero) as the command driving force FdTr. Therefore, after timing t23, of the driving force Fd and the braking force Fb, only the braking force Fb is applied to the vehicle 10. If the braking force Fb continues to increase in response to a decrease in the accelerator pedal position AC, the vehicle 10 stops at timing t25.

[0049] In other words, the driving assistance device 60 can suppress a temporary increase in the vehicle speed VS when stopping the vehicle 10 on an off-road downhill road. Furthermore, the driving assistance device 60 can shorten the time lag between when the driver starts a vehicle operation to stop the vehicle 10 and when the vehicle 10 actually stops. Therefore, the driving assistance device 60 can improve the off-road traveling performance of the vehicle 10.

[0050] <Modifications> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0051] The acceleration characteristics map MP1 may be configured to change the relationship between the accelerator pedal position AC and the acceleration DVS as shown in Figure 8. For example, the processing circuit 61 may be configured to change the acceleration characteristics map MP1 from the relationship shown by the dashed line in Figure 8 to the relationship shown by the solid line in Figure 8 in accordance with the driver's preference. Furthermore, for example, the processing circuit 61 may be configured to change the acceleration characteristics map MP1 depending on the weather, road surface conditions, etc. The road surface conditions here include the μ value of the road surface, the road surface roughness index, and the road surface gradient.

[0052] The acceleration range RDVS may be changed in the command value derivation map MP2. For example, the processing circuit 61 may be configured to change at least one of the width of the acceleration range RDVS, the upper limit value of the acceleration range RDVS, and the lower limit value of the acceleration range RDVS in response to the driver's request. Furthermore, for example, the processing circuit 61 may be configured to change at least one of the width of the acceleration range RDVS, the upper limit value of the acceleration range RDVS, and the lower limit value of the acceleration range RDVS in response to weather, road surface conditions, vehicle speed VS, etc. The road surface conditions referred to here include the μ value of the road surface, the rough road index of the road surface, and the gradient of the road surface.

[0053] The acceleration range RDVS may be a range of acceleration DVS that does not include 0 (zero). The operating member may be a member other than the accelerator pedal 11. For example, the driving assistance device 60 may cause the brake pedal 12 to function as the operating member. The vehicle may also be provided with an operating member dedicated to the acceleration / deceleration operation mode, separate from the accelerator pedal 11 and the brake pedal 12. An example of such an operating member is a lever. In this case, it is preferable that the operating member be displaceable in a first operating direction and a second operating direction that is opposite to the first operating direction. For example, the first operating direction is the operating direction when accelerating the vehicle. The second operating direction is the operating direction when decelerating the vehicle.

[0054] An example of an acceleration characteristics map MP11 when such an operating member is used is shown by a solid line in Figure 9. When the operating member is displaced from the reference position in the first operating direction X1, the operating amount QS of the operating member becomes a positive value. When the operating member is displaced from the reference position in the second operating direction X2, the operating amount QS of the operating member becomes a negative value. When the operating member is located at the reference position, the operating amount QS is 0 (zero). In the acceleration characteristics map MP11, when the operating amount QS is a positive value, the acceleration DVS becomes a positive value. When the operating amount QS is a negative value, the acceleration DVS becomes a negative value.

[0055] Even when such an operating member is employed, the acceleration characteristic map MP11 may be changed from the characteristic shown by the solid line in Fig. 9 to the characteristic shown by the dashed line in Fig. 9. The acceleration characteristic may be a relational expression that shows the relationship between the operation amount of the operating member and the acceleration, instead of a map such as that shown in Fig. 2.

[0056] In the above embodiment, an electronic control unit that functions as the driving assistance device 60 is provided separately from the electronic control unit that functions as the drive control unit 22, but this is not limited to this. That is, the electronic control unit that functions as the drive control unit 22 may also function as the driving assistance device 60. In this case, various information and commands can be transmitted and received between the driving assistance device 60 and the drive control unit 22 without going through an in-vehicle network.

[0057] In the above embodiment, an electronic control unit that functions as the driving assistance device 60 is provided separately from the electronic control unit that functions as the braking control unit 32, but this is not limited to this. That is, the electronic control unit that functions as the braking control unit 32 may also function as the driving assistance device 60. In this case, various information and commands can be transmitted and received between the driving assistance device 60 and the braking control unit 32 without going through an in-vehicle network.

[0058] The CPU 62, the first memory 63, and the second memory 64 do not all need to be mounted on the same board. That is, the CPU 62, the first memory 63, and the second memory 64 may be mounted separately, like the drive control unit 22 and the braking control unit 32.

[0059] The processing circuitry 61 is not limited to a circuit having a CPU and ROM and executing software processing. In other words, the processing circuitry 61 may have any one of the following configurations (a), (b), and (c):

[0060] (a) The processing circuitry 61 includes one or more processors that execute various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to execute processes. Memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or special-purpose computer.

[0061] (b) The processing circuit 61 includes one or more dedicated hardware circuits that perform various processes. Examples of dedicated hardware circuits include application specific integrated circuits (ASICs) or FPGAs. ASIC is an abbreviation for "Application Specific Integrated Circuit." FPGA is an abbreviation for "Field Programmable Gate Array."

[0062] (c) The processing circuitry 61 includes one or more processors that execute some of the various processes in accordance with a computer program, and one or more dedicated hardware circuits that execute the remaining processes among the various processes.

[0063] It should be noted 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" used in this specification means "only one option" or "both of two options" if the number of options is two. As another example, the expression "at least one" used in this specification means "only one option" or "any combination of two or more options" if the number of options is three or more.

Claims

1. A driving assistance device applied to a vehicle, the vehicle comprising: an operating member operated to adjust the acceleration of the vehicle; a drive unit configured to adjust the driving force of the vehicle; and a brake unit configured to adjust the braking force of the vehicle, the driving assistance device comprising: a memory that stores acceleration characteristics that indicate the relationship between the operation amount of the operating member and the acceleration of the vehicle; a demand derivation unit configured to derive, based on the acceleration characteristics, an acceleration of the vehicle corresponding to the operation amount, as a required acceleration; and a command processing unit configured to send a command value corresponding to the required acceleration to the drive unit and the brake unit, wherein the command processing unit is further configured to derive, when the required acceleration is within a predetermined acceleration range, the command value for the driving force and the command value for the braking force so that both are greater than 0 (zero) and the difference between the command value for the driving force and the command value for the braking force is a value corresponding to the required acceleration.

2. The driving assistance device according to claim 1, wherein the acceleration range is a range of acceleration of the vehicle that includes 0 (zero), and the command processing unit is further configured to: derive the driving force command value and the braking force command value so that the driving force command value is greater than the braking force command value when the required acceleration is included in the acceleration range and is greater than 0 (zero), and derive the driving force command value and the braking force command value so that the braking force command value is greater than the driving force command value when the required acceleration is included in the acceleration range and is less than 0 (zero).

3. The driving assistance device according to claim 1 or 2, wherein the command processing unit is further configured to: derive a driving force corresponding to the requested acceleration as the command value of the driving force when the requested acceleration is greater than an upper limit of the acceleration range; and derive a braking force corresponding to the requested acceleration as the command value of the braking force when the requested acceleration is less than a lower limit of the acceleration range.

4. The driving assistance device according to claim 1 or 2, wherein the command processing unit is further configured to: derive 0 (zero) as the command value for the braking force when the required acceleration is greater than an upper limit of the acceleration range; and derive 0 (zero) as the command value for the driving force when the required acceleration is less than a lower limit of the acceleration range.

5. A driving assistance method applied to a vehicle, the vehicle comprising an operating member that is operated to adjust the acceleration of the vehicle, a drive device configured to adjust the driving force of the vehicle, and a braking device configured to adjust the braking force of the vehicle, the driving assistance method comprising: deriving, as a required acceleration, an acceleration of the vehicle that corresponds to the operation amount of the operating member based on an acceleration characteristic that indicates the relationship between the operation amount of the operating member and the acceleration of the vehicle; deriving a command value that corresponds to the required acceleration; and transmitting the command value that corresponds to the required acceleration to the driving device and the braking device, wherein deriving the command value that corresponds to the required acceleration includes deriving the command value for the driving force and the command value for the braking force so that, when the required acceleration is within a predetermined acceleration range, both the command value for the driving force and the command value for the braking force are greater than 0 (zero), and the difference between the command value for the driving force and the command value for the braking force is a value that corresponds to the required acceleration.

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