Driving assistance systems

Abstract

To enable rear wheels of a vehicle to completely pass on a disturbance generated part promptly when the vehicle runs at a low speed.SOLUTION: An executing device 62 of a driving support device 60 executes constant-speed control of adjusting a driving force indication value and a braking force indication value, by feed-back control based on a deviation between a vehicle body speed and a target vehicle body speed. When executing the constant-speed control, the executing part 62 makes a memorizing device 63 an increase speed of the driving force indication value at a timing at which a preceding wheel of a front wheel 11 and a rear wheel 12 of a vehicle 10 passes on a disturbance-generated part. At the time when the preceding wheel passes on the disturbance-generated part and thereafter, the executing device 62 executes driving force-increase control by which the driving force indication value is increased at the increase speed memorized in the memorizing device 63.SELECTED DRAWING: Figure 1

Description

[[Technical Field]]

[0001] The present invention relates to a driving assistance device that assists a vehicle driver in vehicle operations. [[Background Art]]

[0002] Patent Document 1 discloses a parking assistance device that assists parking of a vehicle. Said device comprises a storage unit that stores the driving force of the vehicle at a predetermined position on the travel path of the vehicle to the target parking position when the vehicle is parked at the target parking position by the driving operation of the driver. Then, when the vehicle is automatically parked at the target parking position in a state where the storage unit stores the driving force, said device controls the vehicle using the driving force stored in the storage unit. [[Prior Art Documents]] [[Patent Documents]]

[0003] [[Patent Document 1]] Japanese Unexamined Patent Publication No. 2015-77862 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] When a vehicle travels at a low speed, the driving force of the vehicle is relatively small. Therefore, when the vehicle travels along a travel path that has a disturbance portion that increases travel resistance when the wheels pass through, such as a step, a sudden change in road gradient, or a depression in the road surface, it may take time for the wheels to pass through the disturbance portion. [[Means for Solving the Problem]]

[0005] A driver assistance device for solving the above problems includes a command unit that performs constant speed control to adjust the driving force and braking force of the vehicle by feedback control based on the deviation between the vehicle's body speed and a target vehicle body speed, and a storage unit that stores the rate at which the vehicle's driving force increases when the leading wheel, which is one of the front and rear wheels of the vehicle and is located in the direction of travel of the vehicle, passes over a disturbance in the vehicle's travel path, when the constant speed control is being performed. The command unit performs driving force increase control to increase the vehicle's driving force by the rate at which it increases, as stored in the storage unit, after the leading wheel has passed over the disturbance.

[0006] The above-mentioned driver assistance device, when the leading wheel passes over the disturbed area by implementing constant-speed control, stores the rate of increase in driving force at the time the leading wheel passes over the disturbed area in its memory. Then, from the time the leading wheel passes over the disturbed area onward, the driver assistance device implements driving force increase control, which increases the vehicle's driving force at the rate of increase stored in the memory. Compared to the case where constant-speed control continues even after the leading wheel passes over the disturbed area, by implementing driving force increase control, the vehicle's driving force can be increased earlier to a level that can counteract the increased driving resistance caused by the disturbed area. As a result, the trailing wheel can pass over the disturbed area earlier.

[0007] Therefore, the above-mentioned driving assistance device can enable the vehicle's rear wheels to complete passing over the disturbed area earlier when the vehicle is traveling at a low speed. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing a vehicle equipped with the driver assistance system of the embodiment. [Figure 2] Figure 2 is a schematic diagram showing a vehicle traveling at a low speed towards a parking spot. [Figure 3] Figure 3 is a flowchart showing the processing routines executed by the execution device of the driver assistance system. [Figure 4]Figure 4 is a flowchart showing the processing routine executed by the execution device. [Figure 5] Figure 5 is a timing chart showing the changes in various parameters as the vehicle travels at a low speed towards the parking position. [Modes for carrying out the invention]

[0009] An embodiment of the driving assistance device will be described below with reference to Figures 1 to 5. In this embodiment, as an example of a wheel passing over a disturbance that increases driving resistance when the wheel passes over it, the case where the wheel goes over a step will be described.

[0010] Figure 1 shows a part of a vehicle 10 equipped with a driver assistance device 60. <Vehicle Configuration> Vehicle 10 is equipped with front wheels 11 and rear wheels 12. Vehicle 10 is equipped with the same number of friction brakes 20 as the number of wheels, a braking device 30, and a drive device 40. One friction brake 20 is provided for each wheel.

[0011] Each of the multiple friction brakes 20 has 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 part 22 against the rotating body 21. The higher the hydraulic pressure inside the wheel cylinder 23, the greater the force pressing the friction part 22 against the rotating body 21. In other words, the higher the hydraulic pressure inside the wheel cylinder 23, the greater the braking force applied to the wheel.

[0012] The braking device 30 includes a braking actuator 31 and a braking control unit 32 that controls the braking actuator 31. The braking actuator 31 is configured to individually adjust the hydraulic pressure in multiple wheel cylinders 23.

[0013] The braking control unit 32 controls the braking force of the vehicle 10 by operating the braking actuator 31. The braking control unit 32 can communicate with the driver assistance system 60 via the in-vehicle network. For example, when the braking control unit 32 receives a braking force instruction value FbR, which is the instruction value of the braking force of the vehicle 10, from the driver assistance system 60, it operates the braking actuator 31 based on the braking force instruction value FbR.

[0014] The drive unit 40 includes a power unit 41 and a drive control unit 42 that controls the power unit 41. The power unit 41 has at least one of an engine and an electric motor as a power source for the vehicle 10. In the vehicle 10, the output torque of the power unit 41 is transmitted to the front wheels 11. Note that the output torque of the power unit 41 only needs to be transmitted to at least one of the front wheels 11 and the rear wheels 12.

[0015] 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 driver assistance system 60 via the in-vehicle network. For example, when the drive control unit 42 receives a driving force instruction value FdR, which is the instructed value of the driving force of the vehicle 10, from the driver assistance system 60, it operates the power unit 41 based on the driving force instruction value FdR.

[0016] <Vehicle detection system> The detection system of the vehicle 10 is equipped with multiple sensors. The multiple sensors include wheel speed sensors 51, the same number as the wheels, longitudinal acceleration sensors 52, and a brake switch 53. The multiple wheel speed sensors 51 each detect the rotational speed of the corresponding wheel. The longitudinal acceleration sensors 52 detect the longitudinal acceleration of the vehicle 10. The brake switch 53 outputs a signal indicating whether the driver is operating the braking control member 15. The braking control 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 called "wheel speed VW". The longitudinal acceleration based on the detected value of the longitudinal acceleration sensor 52 is called "longitudinal acceleration GX". The driver's operation of the braking control member 15 is also called "braking operation".

[0017] <Driving support device> The driving support device 60 has a function of supporting a driver's vehicle operations. The "vehicle operations" herein include accelerator operation, braking operation, and steering operation. For example, the driving support device 60 has a support function that causes the vehicle 10 to perform automatic travel at low speed. Such a support function is used when parking the vehicle 10 in a parking position, for example. The "low speed travel of the vehicle 10" herein refers to travel of the vehicle 10 at less than 10 km / h, for example. Furthermore, "automatic travel" refers to travel of the vehicle 10 in a state where the vehicle body speed of the vehicle 10 is adjusted on the vehicle 10 side.

[0018] 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, the execution device 62 is a CPU. The storage device 63 stores various control programs executed by the execution device 62. When implementing the above-described support function, the execution device 62 transmits a driving force command value FdR to a drive control unit 42, and transmits a braking force command value FbR to a braking control unit 32.

[0019] By executing the control program, the execution device 62 functions as a command unit M11 and a target vehicle body speed setting unit M13. The command unit M11 and the target vehicle body speed setting unit M13 are functional units for realizing the above-described support function.

[0020] <Command unit> The command unit M11 performs constant speed control for adjusting the driving force and braking force of the vehicle 10 by feedback control based on the deviation between the vehicle body speed VS of the vehicle 10 and a target vehicle body speed VSTr. The feedback control is, for example, PID control or PI control. The vehicle body speed VS is derived based on at least one of the wheel speeds VW of the plurality of wheels. As the target vehicle body speed VSTr, the above-mentioned speed less than 10 km / h is set.

[0021] As shown in Figure 2, there may be a step 101 in the vehicle 10's travel path 100. In this case, of the front wheels 11 and rear wheels 12, the leading wheel, which is the wheel located in the direction of vehicle 10's travel, will overcome the step 101 first, followed by the trailing wheel, which is not the leading wheel. As shown in the example in Figure 2, when vehicle 10 is moving backward, the rear of vehicle 10 is in the direction of vehicle 10's travel, so the rear wheel 12 corresponds to the leading wheel and the front wheel 11 corresponds to the trailing wheel. On the other hand, when vehicle 10 is moving forward, the front of vehicle 10 is in the direction of vehicle 10's travel, so the front wheel 11 corresponds to the leading wheel and the rear wheel 12 corresponds to the trailing wheel.

[0022] If the leading wheel comes into contact with the step 101 while constant speed control is being performed, the vehicle 10's driving resistance will increase compared to before the leading wheel came into contact with the step 101. Therefore, if the vehicle 10's driving force Fd is small, the leading wheel may not be able to overcome the step 101, and the vehicle 10 may stop. For example, the vehicle 10's driving force Fd is also the torque generated by the power unit 41. In this case, the command unit M11 increases the driving force instruction value FdR by feedback control, which takes the deviation between the vehicle speed VS and the target vehicle speed VSTr as input. When the leading wheel overcomes the step 101 because the vehicle 10's driving force Fd has increased as the driving force instruction value FdR has increased, the command unit M11 stores the rate of increase ΔFdR of the driving force instruction value FdR at the time the leading wheel overcame the step 101 in the memory device 63. In other words, the memory device 63 corresponds to a "storage unit" that stores the increasing speed ΔFdR at the time the leading wheel passes over the step 101, which is an example of an external disturbance.

[0023] The command unit M11 performs a driving force increase control, which increases the driving force instruction value FdR at the increase rate ΔFdR stored in the memory device 63, from the point when the leading wheel has overcome the step 101. Specifically, the command unit M11 starts the driving force increase control before the trailing wheel makes contact with the step 101.

[0024] Even if the driving force instruction value FdR is increased by implementing the driving force increase control, the rear wheels may not easily overcome the step 101. Therefore, if the elapsed time TM from the start of the driving force increase control exceeds the specified time TMth and the rear wheels have not overcome the step 101, the command unit M11 increases the driving force instruction value FdR at a higher speed than the increase speed ΔFdR stored in the memory device 63.

[0025] Furthermore, once constant speed control is interrupted and driving force increase control is initiated, the driving force instruction value FdR continues to increase. As a result, the vehicle speed VS may exceed the target vehicle speed VSTr. Therefore, the command unit M11 adjusts the braking force instruction value FbR after the driving force increase control is initiated to prevent the vehicle speed VS from deviating from the target vehicle speed VSTr.

[0026] Then, once the rear wheels have overcome the step 101, the control unit M11 resumes constant speed control. <Target vehicle speed setting unit> The target vehicle speed setting unit M13 sets the target vehicle speed VSTr as described above. Before the rear wheels overcome the step 101, that is, before the rear wheels pass over the step 101 (disturbance), the target vehicle speed setting unit M13 sets the first vehicle speed VS1 as the target vehicle speed VSTr. After the rear wheels overcome the step 101, that is, after the rear wheels pass over the step 101 (disturbance), the target vehicle speed setting unit M13 increases the target vehicle speed VSTr. Specifically, the target vehicle speed setting unit M13 gradually increases the target vehicle speed VSTr up to the second vehicle speed VS2. The second vehicle speed VS2 is set to be a vehicle speed higher than the first vehicle speed VS1. Furthermore, if the vehicle 10 stops due to the driver's braking operation or the like, the target vehicle speed setting unit M13 sets the first vehicle speed VS1 as the target vehicle speed VSTr.

[0027] <Drive Brake Adjustment Process> Referring to Figure 3, a processing routine showing the drive-braking adjustment process performed by the execution device 62 to derive the drive force instruction value FdR and the braking force instruction value FbR will be described. Several steps S11 to S35 of this processing routine are performed by the execution device 62 functioning as the command unit M11.

[0028] The execution device 62 repeatedly executes this processing routine at predetermined control cycles if it determines that the execution conditions for the above-mentioned support function have been met. For example, the execution device 62 determines that the execution conditions have been met when the driver performs an operation to turn on the above-mentioned support function, or when it detects that the driver has started operating the vehicle to park the vehicle 10 in a predetermined parking position.

[0029] In step S11, the execution device 62 determines whether the leading wheel of the vehicle 10 has overcome the step 101. Referring to Figure 5, an example of the process for determining whether the leading wheel has overcome the step 101 will be explained. When the leading wheel comes into contact with the step 101 while the execution device 62 is performing constant speed control, the vehicle 10 stops. That is, as shown in Figure 5(A), the vehicle speed VS becomes 0 (zero). In this case, since the vehicle speed VS is below the target vehicle speed VSTr, the execution device 62 increases the driving force instruction value FdR by feedback control, as shown in Figure 5(D). When the driving force Fd of the vehicle 10 exceeds the driving force required to make the leading wheel overcome the step 101, the leading wheel overcomes the step 101. That is, the leading wheel begins to rotate. As a result, the vehicle 10 starts moving, and the vehicle speed VS suddenly increases, as shown in Figure 5(A).

[0030] Therefore, the execution device 62 determines that the leading wheel has overcome the step 101 when the following condition (A1) is met during constant speed control. That is, the execution device 62 determines that the leading wheel has passed over the step 101, which is an example of an external disturbance. A value is set as the determination increase speed that allows the system to determine whether or not the vehicle speed VS has increased rapidly. (A1) When the vehicle speed VS is greater than 0 (zero) from a state where it is 0 (zero), the rate of increase of the vehicle speed VS must be equal to or greater than the rate of increase determined.

[0031] Returning to Figure 3, in step S11, if the execution device 62 determines that the leading wheel has overcome the step 101 (YES), it proceeds to step S15. On the other hand, if the execution device 62 determines that the leading wheel has not overcome the step 101 (S11:NO), it proceeds to step S13.

[0032] Furthermore, if the execution device 62 determines, by executing the above determination process, that the leading wheel has overcome the step 101, it will continue to determine that the leading wheel has overcome the step 101 until the step section determination flag FLG, described later, switches from on to off.

[0033] In step S13, the execution device 62 performs constant speed control. Specifically, the execution device 62 derives a control variable by feedback control, which takes the deviation between the vehicle speed VS and the target vehicle speed VSTr as input. This control variable is called the "FB control variable". Based on the FB control variable, the execution device 62 derives the driving force instruction value FdR and the braking force instruction value FbR. For example, if the leading wheel cannot overcome the step 101 and the vehicle speed VS is significantly lower than the target vehicle speed VSTr, the execution device 62 increases the driving force instruction value FdR while keeping the braking force instruction value FbR at 0 (zero) by performing feedback control. The execution device 62 transmits the driving force instruction value FdR to the drive control unit 42 and the braking force instruction value FbR to the braking control unit 32. After transmitting the instruction values ​​FdR and FbR, the execution device 62 terminates this processing routine.

[0034] In step S15, the execution device 62 determines whether the step section determination flag FLG is set to off. The step section determination flag FLG is a flag used to determine whether the vehicle 10 is traveling through a section where a step 101 exists. If the vehicle 10 is traveling through a section where a step 101 exists, the step section determination flag FLG is set to on. If the vehicle 10 is traveling through a section where there is no step 101, or if the vehicle 10 has passed through such a section, the step section determination flag FLG is set to off. If the step section determination flag FLG is set to off (S15: YES), the execution device 62 proceeds to step S17. On the other hand, if the step section determination flag FLG is set to on (S15: NO), the execution device 62 proceeds to step S21.

[0035] In step S17, the execution device 62 stores the current rate of increase ΔFdR of the driving force instruction value FdR in the memory device 63. That is, the execution device 62 stores the rate of increase ΔFdR at the time it determines that the leading wheel has overcome the step 101 in the memory device 63. For example, the execution device 62 stores the time derivative of the driving force instruction value FdR as the rate of increase ΔFdR in the memory device 63. The rate of increase ΔFdR stored in the memory device 63 can be said to be "the rate of increase of the driving force of the vehicle 10 at the time the leading wheel passes over a disturbance present in the vehicle 10's travel path." Furthermore, the feedback control in this example is PI control or PID control. Therefore, the longer the vehicle 10 remains in a state of not starting, the larger the rate of increase ΔFdR of the driving force instruction value FdR becomes. Therefore, compared to the case where the step 101 is small and the time required for the leading wheel to overcome the step 101 is short, the value of the increasing speed ΔFdR stored in the memory device 63 is larger when the step 101 is large and the time required for the leading wheel to overcome the step 101 is long.

[0036] Next, in step S19, the execution device 62 sets the step section determination flag FLG to ON. After that, the execution device 62 proceeds to step S21. In step S21, the execution device 62 determines whether a predetermined first time lag TL1 has elapsed since it determined that the leading wheel has overcome the step 101. The time at which it determines that the leading wheel has overcome the step 101 can also be said to be the time when the leading wheel passes over the disturbance. If constant speed control continues even after the leading wheel has overcome the step 101, the vehicle speed VS will increase. Therefore, the driving force instruction value FdR is reduced by feedback control. When the driving force instruction value FdR is reduced, the driving force Fd of the vehicle 10 also decreases. The delay in the response of the driving force Fd to the decrease in the driving force instruction value FdR can be known in advance from the specifications of the vehicle 10. Therefore, the length of time that takes this response delay into account is set as the first time lag TL1. If the execution device 62 determines that the first time lag TL1 has elapsed since it determined that the leading wheel has overcome the step 101 (S21: YES), it proceeds to step S23. On the other hand, if the execution device 62 determines that the leading wheel has overcome the step 101, and the first time lag TL1 has not elapsed (S21:NO), the process moves to step S13 and constant speed control is performed.

[0037] In step S23, the execution device 62 determines whether the elapsed time TM from the reference time exceeds the specified time TMth. The reference time is the time when the first time lag TL1 has elapsed from the time when it is determined that the leading wheel has overcome the step 101. The reference time can also be said to be the start time of the driving force increase control described later. The execution time of the driving force increase control is set as the specified time TMth. The specified time TMth may be set based on the wheelbase length of the vehicle 10 and the target vehicle speed VSTr. If the elapsed time TM exceeds the specified time TMth (S23: YES), the execution device 62 proceeds to step S27. On the other hand, if the elapsed time TM is less than or equal to the specified time TMth (S23: NO), the execution device 62 proceeds to step S25.

[0038] In step S25, the execution device 62 increases the drive force instruction value FdR at the increase rate ΔFdR stored in the memory device 63. That is, step S25 corresponds to "drive force increase control". For example, the execution device 62 derives the latest value of the drive force instruction value FdR as the sum of the product of the increase rate ΔFdR and the cycle time TMc and the previous value of the drive force instruction value FdR. The cycle time TMc is the length of the control cycle of this processing routine. The previous value of the drive force instruction value FdR is the drive force instruction value FdR derived when this processing routine was executed last time. The execution device 62 transmits the derived latest value of the drive force instruction value FdR to the drive control unit 42. Then, the execution device 62 moves the process to step S29.

[0039] In step S27, the execution device 62 increases the drive force instruction value FdR at a speed higher than the increase rate ΔFdR stored in the memory device 63. For example, the execution device 62 derives the latest value of the drive force instruction value FdR as the sum of the product of the increase rate ΔFdR and the cycle time TMc, the previous value of the drive force instruction value FdR, and a predetermined offset drive force α. A positive drive force is set as the offset drive force α. The execution device 62 transmits the derived latest value of the drive force instruction value FdR to the drive control unit 42. Then, the execution device 62 moves the process to step S29.

[0040] In step S29, the execution device 62 derives a braking force instruction value FbR to suppress the vehicle speed VS from deviating from the target vehicle speed VSTr. For example, the execution device 62 derives the braking force instruction value FbR based on feedback control that takes the deviation between the vehicle speed VS and the target vehicle speed VSTr as input. The feedback control performed here is, for example, PID control or PI control. The execution device 62 transmits the derived braking force instruction value FbR to the braking control unit 32. As a result, the execution device 62 can suppress the vehicle speed VS from deviating from the target vehicle speed VSTr by adjusting the braking force instruction value FbR. After transmitting the braking force instruction value FbR, the execution device 62 proceeds to step S31.

[0041] In step S31, the execution device 62 determines whether the rear wheels of the vehicle 10 have overcome the step 101. Referring to Figure 5, an example of the process for determining whether the rear wheel has overcome the step 101 will be explained. After the start of the driving force increase control, the execution device 62 adjusts the braking force Fb to prevent the vehicle speed VS from exceeding the target vehicle speed VSTr. Since the step 101 is an obstacle to increasing the vehicle speed VS, when the rear wheel overcomes the step 101, the vehicle speed VS temporarily decreases and then increases, as shown around timing t14 in Figure 5. Therefore, the execution device 62 determines that the rear wheel has overcome the step 101 when it detects a decrease or increase in vehicle speed VS while adjusting the braking force Fb as described above. For example, the execution device 62 determines that the rear wheel has overcome the step 101 if the rate of decrease in vehicle speed VS is equal to or greater than the determined rate of decrease. In this case, "the rear wheel has overcome the step 101" also includes "the state in which the rear wheel is in contact with the step 101 and is in the process of overcoming the step 101." On the other hand, the execution device 62 determines that the rear wheels have not crossed the step 101 if the rate of decrease in vehicle speed VS is less than the determined rate of decrease. In this case, the rate of decrease at which it can determine whether or not the vehicle speed VS has started to decrease due to the rear wheels crossing the step 101 is set as the determined rate of decrease.

[0042] Returning to Figure 3, in step S31, if the execution device 62 determines that the rear wheel has overcome the step 101 (YES), it proceeds to step S33. On the other hand, if the execution device 62 determines that the rear wheel has not overcome the step 101 (S31:NO), it terminates this processing routine.

[0043] In step S33, the execution device 62 determines whether a predetermined second time lag TL2 has elapsed since the time of overcoming the obstacle, which is the point at which the determination in step S31 switched from NO to YES. The time of overcoming the obstacle can also be said to be the point at which it is determined that the rear wheels have overcome the step 101. When the rear wheels have overcome the step, the vehicle speed VS temporarily decreases. In this case, if braking force is applied to the vehicle 10 based on the braking force instruction value FbR, the braking force instruction value FbR decreases due to the decrease in vehicle speed VS. The length of time required for the vehicle speed VS to recover to some extent can be predicted to some extent from the specifications of the vehicle 10. Therefore, the length of time at which it is possible to determine whether the vehicle speed VS has recovered to some extent is set as the second time lag TL2. If the second time lag TL2 has elapsed since the time of overcoming the obstacle (S33: YES), the execution device 62 proceeds to step S35. On the other hand, if the execution device 62 has not yet completed the second time lag TL2 since the point of crossing the threshold (S33:NO), it terminates this processing routine.

[0044] In step S35, the execution device 62 sets the step section determination flag FLG to off. Then, the execution device 62 proceeds to step S13 to perform constant speed control. <Target vehicle speed setting process> Referring to Figure 4, a processing routine showing the target vehicle speed setting process executed by the execution device 62 to set the target vehicle speed VSTr will be described. Several steps S51 to S59 of this processing routine are executed by the execution device 62 functioning as the target vehicle speed setting unit M13. The execution device 62 repeatedly executes this processing routine at predetermined control cycles.

[0045] In step S51, the execution device 62 determines whether the vehicle 10 is stopped or not. For example, the execution device 62 determines whether the vehicle 10 is stopped or not based on the vehicle speed VS. If the execution device 62 determines that the vehicle 10 is stopped (S51: YES), it proceeds to step S55. On the other hand, if the execution device 62 determines that the vehicle 10 is not stopped (S51: NO), it proceeds to step S53.

[0046] In step S53, the execution device 62 determines whether the rear wheel has overcome the step 101, similar to step S31 shown in Figure 3. If the execution device 62 determines that the rear wheel has overcome the step 101 (S53: YES), it proceeds to step S57. On the other hand, if the execution device 62 determines that the rear wheel has not overcome the step 101 (S53: NO), it proceeds to step S55.

[0047] In step S55, the execution device 62 sets the first vehicle speed VS1 as the target vehicle speed VSTr. After that, the execution device 62 terminates this processing routine. In step S57, the execution device 62 derives the sum of the previous value of the target vehicle speed VSTr and a predetermined speed value dVS as the provisional target vehicle speed VSTr1. The previous value of the target vehicle speed VSTr is the target vehicle speed VSTr derived when this processing routine was executed last time. In the next step S59, the execution device 62 derives the smaller of the provisional target vehicle speed VSTr1 and the second vehicle speed VS2 as the target vehicle speed VSTr. After that, the execution device 62 terminates this processing routine.

[0048] <Mechanism and Effects> The operation and effects of the driver assistance device 60 will be explained with reference to Figures 2 and 5. In this example, when the vehicle 10 is reversing, the driver applies the brakes when the rear wheel 12 (leading wheel) comes into contact with the step 101, thus applying braking force to the vehicle 10. As a result, the vehicle 10 stops with the rear wheel 12 in contact with the step 101. In Figure 5(C), the solid line shows the change in braking force FbS applied to the vehicle 10 by the driver's braking operation, while the dashed line shows the change in the braking force instruction value FbR, or the change in the braking force Fb of the vehicle 10 controlled according to the braking force instruction value FbR. Furthermore, while the driver is performing the braking operation, the driving force instruction value FdR becomes 0 (zero), but the driving force Fd is a predetermined driving force (>0 (zero)).

[0049] As shown in Figure 5, when the driver's braking operation is released at timing t11, constant speed control is initiated, and the driving force command value FdR increases from 0 (zero). However, because the leading wheel, the rear wheel 12, is in contact with the step 101, the driving resistance is high. As a result, the vehicle 10 does not start. That is, the vehicle speed VS remains below the target vehicle speed VSTr. Then, as shown in Figure 5(D), the driving force command value FdR is increased by feedback control. In this way, the driving force Fd of the vehicle 10 also increases in accordance with the increase in the driving force command value FdR.

[0050] At timing t12, the driving force Fd of the vehicle 10 exceeds the driving force required to make the rear wheels 12 overcome the step 101, so the rear wheels 12 overcome the step 101. As a result, the vehicle 10 starts moving, and the vehicle speed VS increases as shown in Figure 5(A). When it is determined that the leading wheel, the rear wheel 12, has overcome the step 101, the step section determination flag FLG is set to ON as shown in Figure 5(E). In addition, the rate of increase ΔFdR of the driving force instruction value FdR at timing t12 is stored in the memory device 63.

[0051] When the rear wheels 12 cross the step 101, the driving force instruction value FdR is reduced and the braking force instruction value FbR is increased in order to prevent the vehicle speed VS from exceeding the target vehicle speed VSTr. This prevents the vehicle speed VS from deviating from the target vehicle speed VSTr.

[0052] At timing t13, which is the point when the first time lag TL1 has elapsed from timing t12, constant speed control ends and driving force increase control begins. In other words, driving force increase control begins before the rear wheels reach the step 101, which is an example of an external disturbance. As a result, even if the vehicle speed VS is not less than the target vehicle speed VSTr, the driving force instruction value FdR is increased by the increase rate ΔFdR stored in the memory device 63. This allows the driving force Fd of the vehicle 10 to be increased earlier. Furthermore, the driving force Fd can be increased at an increase rate corresponding to the size of the step 101.

[0053] Here, we will describe a comparative example in which constant speed control is continued even after the leading wheels have overcome the step 101. In this case, after the leading wheels have overcome the step 101, the vehicle speed VS is almost equal to the target vehicle speed VSTr, so the driving force instruction value FdR and the driving force Fd are relatively small. With the driving force Fd being relatively small in this way, the trailing wheels will come into contact with the step 101. As a result, there is a risk that the trailing wheels will not be able to overcome the step 101 and the vehicle 10 will come to a stop. Alternatively, even if the vehicle 10 does not come to a stop, there is a risk that the vehicle speed VS will drop to near 0 (zero). When constant speed control is implemented, the driving force instruction value FdR gradually increases after a deviation occurs between the vehicle speed VS and the target vehicle speed VSTr. As a result, it takes time for the trailing wheels to overcome the step 101 due to the increase in driving force Fd. If it takes time for the rear wheels to overcome the step 101, the driver may try to move the vehicle 10 faster, which could lead to the driver accelerating and then braking.

[0054] In this embodiment, the driving force Fd can be increased even before the rear wheels make contact with the step 101. Therefore, compared to the comparative example, the rear wheels can overcome the step 101 earlier. Consequently, when the vehicle 10 is automatically traveling at a low speed, the rear wheels can overcome the step 101 earlier. Thus, the vehicle 10 can be started quickly before the driver operates the accelerator to start the stationary vehicle 10. In other words, it is possible to suppress the driver's unnecessary accelerator or braking operations when making the wheels overcome the step 101.

[0055] In the example shown in Figure 5, at timing t14 during the implementation of the driving force increase control, it is determined that the front wheel 11 has overcome the step 101. When the vehicle speed VS decreases as the wheel overcomes the step 101, the braking force instruction value FbR is rapidly reduced. As a result, the already increased driving force Fd is quickly exerted on the contact surface of the drive wheel to allow the wheel to overcome the step 101. The increase in the driving force instruction value FdR by the driving force increase control is carried out from timing t14 until timing t15, which is the time when the second time lag TL2 has elapsed.

[0056] At timing t15, constant speed control is resumed. Then, the vehicle speed VS is controlled by adjusting the driving force Fd and braking force Fb. In the example shown in Figure 5, the braking force instruction value FbR gradually decreases when the system switches to constant speed control. In addition, the driving force instruction value FdR also decreases in accordance with the decrease in the braking force instruction value FbR. When the driver starts braking at timing t17 while constant speed control is in operation, a braking force FbS is applied to the vehicle 10, causing the vehicle 10 to stop. In other words, constant speed control is terminated.

[0057] Furthermore, the following effects can be obtained with the driver assistance device 60. (1) Even after starting the drive force increase control, the rear wheels may have difficulty overcoming the step 101. In this embodiment, if the rear wheels have not overcome the step 101 even at timing t16, which is a specified time TMth after timing t13, the start of the drive force increase control, the drive force instruction value FdR will be increased at a faster rate than when the drive force increase control is being performed. This makes it possible to increase the drive force Fd earlier and more than when the drive force increase control is being continued. Therefore, it is possible to suppress delays in the rear wheels overcoming the step 101.

[0058] (2) After the start of the driving force increase control, the driving force instruction value FdR is increased regardless of whether the vehicle speed VS is less than the target vehicle speed VSTr, so there is a risk that the discrepancy between the vehicle speed VS and the target vehicle speed VSTr will become large. In this embodiment, during the period from the start of the driving force increase control until the constant speed control is resumed, the discrepancy between the vehicle speed VS and the target vehicle speed VSTr is suppressed by adjusting the braking force instruction value FbR. This makes it possible to suppress the vehicle speed VS from significantly exceeding the target vehicle speed VSTr when the vehicle 10 is automatically driving through a section where a step 101 exists. This makes it possible to suppress the impact when the rear wheels collide with the step 101 due to a significant increase in the vehicle speed VS.

[0059] (3) The driver does not need to operate the accelerator when the wheels go over the step 101. In addition, it is possible to prevent the driver from having to brake in order to decelerate the vehicle 10 because the vehicle speed VS has become excessively large due to accelerator operation when the wheels go over the step.

[0060] (4) When the vehicle 10 passes over the section where the step 101 exists, the target vehicle speed VSTr gradually increases. In the example shown in Figure 5, the target vehicle speed VSTr increases toward the second vehicle speed VS2 from timing t14. This allows the vehicle 10 to move to the predetermined parking position earlier.

[0061] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0062] It is not essential to increase the target vehicle speed (VSTr) after the rear wheel has overcome the obstacle 101. The first vehicle speed VS1 and the second vehicle speed VS2 may be made changeable by the driver's operation.

[0063] After the start of the driving force increase control, the braking force instruction value FbR is varied according to the deviation between the vehicle speed VS and the target vehicle speed VSTr, but this is not limited to this. For example, the execution device 62 may maintain the braking force instruction value FbR at a predetermined value during the period from the start of the driving force increase control until the restart of constant speed control.

[0064] The execution device 62 may increase the drive force instruction value FdR at an increase rate proportional to the increase rate ΔFdR stored in the memory device 63 during drive force increase control. The execution device 62 may also set an upper limit on the increase rate of the drive force instruction value FdR during the execution of drive force increase control.

[0065] The execution device 62 may determine that the rear wheels have overcome the step 101 when it is confirmed that the rate of decrease of the vehicle speed VS becomes equal to or greater than the determined rate of decrease, and then the vehicle speed VS begins to increase. The fact that the vehicle speed VS has begun to increase may be confirmed, for example, by detecting that a predetermined amount of time has passed since the point in time when the vehicle speed VS changed from a decreasing state to an increasing state. The state in which the vehicle speed VS is decreasing is strictly speaking a state in which a load is applied to the vehicle 10 for the rear wheels to overcome the step 101, and there are cases in which the rear wheels are located on the step 101 and have not completely overcome the step 101. Therefore, by confirming the increase in the vehicle speed VS, it is possible to reliably detect the state in which the rear wheels have overcome the step 101.

[0066] The execution device 62 does not need to adjust the braking force instruction value FbR to suppress the vehicle speed VS from deviating from the target vehicle speed VSTr after the start of the driving force increase control.

[0067] The execution device 62 may continue to implement the driving force increase control until it determines that the rear wheel has overcome the step 101. The execution device 62 may switch control from constant speed control to driving force increase control after it can determine through constant speed control that the vehicle speed VS is equal to the target vehicle speed VSTr when the leading wheel has overcome the step 101. In other words, the execution device 62 may start driving force increase control from an intermediate timing between timing t13 and timing t14 in the timing chart shown in Figure 5, or from a timing near that intermediate timing.

[0068] The execution device 62 may switch the control from constant speed control to increased driving force control after the rear wheels have made contact with the step 101, that is, after the rear wheels have reached the disturbance. Even in this case, compared to the case where constant speed control is continued even after the rear wheels have made contact with the step 101, the driving force Fd of the vehicle 10 can be increased earlier to a level that allows the rear wheels to overcome the step 101.

[0069] The support function for automatically driving the vehicle 10 at a low speed, as described above, may also be implemented in situations other than when parking the vehicle 10. If the vehicle 10 is equipped with an imaging device capable of imaging the road surface on which the vehicle 10 is traveling, the driver assistance device 60 can determine whether or not there are disturbances such as steps 101 in the vehicle 10's travel path by analyzing the images captured by the imaging device. The disturbances may be depressions in the road surface or sections where the road surface gradient changes abruptly. The execution device 62 of the driver assistance device 60 may initiate the constant speed control described above when it detects the presence of disturbances by analyzing the images.

[0070] The processing circuit 61 of the driver assistance device 60 is not limited to one that includes a CPU and ROM and performs software processing. In other words, the processing circuit 61 may have any of the following configurations (a) to (c).

[0071] (a) The processing circuit 61 includes one or more processors that perform 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 perform the processes. The memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or dedicated computer.

[0072] (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, i.e., ASICs or FPGAs. ASIC is an abbreviation for "Application Specific Integrated Circuit," and FPGA is an abbreviation for "Field Programmable Gate Array."

[0073] (c) The processing circuit 61 includes a processor that executes a portion of the various processes according to a computer program, and a dedicated hardware circuit that executes the remaining processes among the various processes.

[0074] In this specification, the expression "at least one" means "one or more" of the desired options. For example, if there are two options, the expression "at least one" means "only one option" or "both of the two options." As another example, if there are three or more options, the expression "at least one" means "only one option" or "a combination of two or more arbitrary options."

[0075] <Other technological ideas> The technical concepts that can be understood from the above embodiments and modified examples are described in the appendix. (Note 1) It is preferable to have a target vehicle speed setting unit that increases the target vehicle speed after the rear wheel has passed over the disturbance section. [Explanation of Symbols]

[0076] 10... Vehicles 11…Front wheel 12... Rear wheel 60…Driving assistance systems 62… Execution device 63…Memory device (an example of a memory unit) 100...Route 101... Step M11…Command unit M13...Target vehicle speed setting unit

Claims

1. A command unit that performs constant speed control by adjusting the driving force and braking force of the vehicle through feedback control based on the deviation between the vehicle's body speed and the target vehicle speed, When the constant speed control is being implemented, the system includes a storage unit that stores the rate at which the driving force of the vehicle increases at the point when the leading wheel, which is one of the front and rear wheels of the vehicle and is located in the direction of travel of the vehicle, passes over a disturbance present in the vehicle's travel path. The command unit performs a driving force increase control that increases the driving force of the vehicle at the increased speed stored in the memory unit after the leading wheel has passed the disturbance area. Driving assistance system.

2. The command unit starts the driving force increase control before the trailing wheel, which is not the leading wheel among the front and rear wheels, reaches the disturbance. The driving support device according to claim 1.

3. The command unit increases the vehicle's driving force at a speed higher than the increase speed stored in the memory unit if the elapsed time from the start of the driving force increase control exceeds a specified time but the following wheel has not passed over the disturbance area. The driving support device according to claim 2.

4. The command unit, after initiating the driving force increase control, adjusts the braking force of the vehicle to prevent the vehicle speed from deviating from the target vehicle speed. A driving assistance device according to any one of claims 1 to 3.

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