Vehicle control device

Abstract

To make a smooth evacuation travel to move to a safe place without any problem when a quick stop at the safe place needs to be made as abnormality related to a steer-by-wire type steering device occurs.SOLUTION: Once abnormality in which the redundancy of a steering device is lost is detected, an upper-limit speed is set to a first reference speed (initial speed) and then the vehicle speed is limited targeting the upper-limit speed in an autonomous evacuation state as a first stage. In a forcible speed reduction state as a second stage, the upper-limit speed is set to decrease gradually from the first reference speed to a predetermined target second reference speed (safety speed), and the vehicle speed is limited targeting the upper-limit speed. In a safety speed maintaining state as a third stage, the upper-limit speed is set to the second reference speed, and the vehicle speed is limited targeting the upper-limit speed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a control device for controlling a steer-by-wire steering device provided in a vehicle. [Background technology]

[0002] In a steer-by-wire steering device, the steering wheel operated by the driver and the rack shaft that steers the wheels are mechanically separated, and a steering angle sensor detects the steering angle of the steering wheel, and a steering actuator steers the wheels in accordance with that steering angle.

[0003] In such steer-by-wire steering devices, reliability is increased by providing redundancy through multiplexing, but if an abnormality occurs and redundancy is lost, continued use may result in difficulty in steering. For this reason, when an abnormality that causes a loss of redundancy occurs, it is necessary to perform evacuation driving by quickly moving the vehicle to a safe evacuation location such as the shoulder of the road and stopping the vehicle.

[0004] As a technology for control when an abnormality occurs in such a steer-by-wire steering device, a technology has been known in the past that, when an abnormality occurs in the generator, suppresses power consumption by limiting the vehicle speed, thereby ensuring the power supplied to the steering device and enabling the driver to steer to an evacuation shelter (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5013312 Summary of the Invention [Problem to be solved by the invention]

[0006] When an abnormality occurs in a steer-by-wire steering device that causes a loss of redundancy, the vehicle must move to a safe evacuation location such as a road shoulder and park there to perform evacuation driving. At this time, the vehicle must drive in accordance with the flow of traffic so as not to impede the driving of other vehicles in the vicinity. However, simply limiting the vehicle speed as in the conventional technology makes it difficult to drive in accordance with the flow of traffic, and there is a problem in that evacuation driving cannot be performed smoothly and without hindrance.

[0007] In view of the above background, an object of the present invention is to provide a vehicle control device that can smoothly and unhinderedly perform evacuation driving to move to a safe place when an abnormality related to a steer-by-wire steering device occurs and it is necessary to quickly stop the vehicle in a safe place. [Means for solving the problem]

[0008] In order to solve such problems, one embodiment of the present invention is a vehicle control device (21) mounted on a vehicle equipped with a steering device (11) in which an operating member (steering wheel 13) operated by a driver and a steering member (rack shaft 12) that steers the wheels (4) are mechanically separated and operated by power supplied from a power supply system (31), and when an abnormality that causes a loss of redundancy in the steering device is detected, first, in a first stage, an upper limit speed is set to a first reference speed, and the vehicle speed is restricted with the upper limit speed as a target, and then, in a second stage, an upper limit speed is set so as to gradually decrease from the first reference speed to a predetermined target second reference speed, and the vehicle speed is restricted with the upper limit speed as a target.

[0009] According to this configuration, when an abnormality occurs in the steer-by-wire steering device that causes a loss of redundancy, unnecessary high speed driving is restricted, but the vehicle speed is not restricted to a low speed suddenly, so that the degree of freedom of movement such as lane changing can be ensured. This allows the vehicle to smoothly and smoothly evacuate to a safe place without any hindrance. In the third stage following the second stage, an upper limit speed may be set to the second reference speed, and the vehicle speed may be restricted with the upper limit speed as a target.

[0010] Furthermore, in the above configuration, the steering device includes a reaction force device (reaction force actuator 17) that applies a reaction force to the operating member, and a steering device (steering actuator 16) that steers the wheels, and at least one of the reaction force device and the steering device has redundancy consisting of two systems, and it is preferable to detect a failure in one of the two systems as an abnormality that causes a loss of redundancy in the steering device.

[0011] According to this configuration, when a failure occurs in one of the two systems of the reaction force device and the steering device, and redundancy of the steering device is lost, it can be detected as an abnormality in the steering device. Note that the reaction force device includes a reaction force actuator, and the steering device includes a steering actuator.

[0012] In the above configuration, the first reference speed may be set to the higher of the vehicle speed of the host vehicle when the abnormality is detected and a permissible speed of the road on which the host vehicle is traveling.

[0013] According to this configuration, if the vehicle speed of the vehicle at the time of abnormality detection is higher than the allowable speed of the road on which the vehicle is traveling, the vehicle speed of the vehicle at the time of abnormality detection is set to the upper limit speed. This makes it possible to prevent sudden deceleration of the vehicle, and enables smooth evacuation. On the other hand, if the allowable speed of the road on which the vehicle is traveling is higher than the vehicle speed of the vehicle at the time of abnormality detection, the allowable speed of the road on which the vehicle is traveling is set to the upper limit speed. This makes it possible to accelerate the vehicle up to the allowable speed of the road, and therefore makes it possible to perform evacuation driving in line with the flow of traffic, specifically, evacuation driving such as changing lanes to move to a safe place, without impeding the driving of other vehicles in the vicinity.

[0014] In the above configuration, the upper limit speed in the second stage may be set based on the deceleration in a state in which the driver is neither operating the accelerator nor the brake.

[0015] According to this configuration, the vehicle can be decelerated to the second reference speed (safe speed) reliably within a predetermined time without the driver performing any particular operation. This braking force includes not only engine braking but also regenerative braking and friction braking. It is preferable that this braking force is set to a deceleration that allows the driver to calmly steer the vehicle.

[0016] In the above configuration, when the speed of the host vehicle is within a speed range of a predetermined width that is equal to or less than the upper speed limit, acceleration that exceeds a predetermined value may be prohibited.

[0017] According to this configuration, when the vehicle speed is near the upper limit speed, sudden acceleration is prohibited, so that it is possible to prevent the host vehicle from suddenly accelerating and causing its speed to temporarily exceed the upper limit speed.

[0018] In the above configuration, when the vehicle speed exceeds the upper limit speed, the driving force of the driving device for traveling (power plant 5) may be limited.

[0019] According to this configuration, when the vehicle speed exceeds the upper limit speed, the vehicle speed can be quickly decelerated to below the upper limit speed. Note that regeneration or friction braking may be used in combination to quickly return the vehicle speed to the upper limit speed.

[0020] Furthermore, in the above configuration, when the power supplied by the power supply system is equal to or greater than a predetermined first reference power, normal control is performed, when the power supplied by the power supply system is less than the first reference power and equal to or greater than a predetermined second reference power, control is performed to limit the vehicle speed with an upper limit speed set in accordance with the remaining power amount of the power supply system as a target, and when the power supplied by the power supply system is less than the second reference power, control is performed to limit the vehicle speed to the second reference speed.

[0021] According to this configuration, even if there is no abnormality that causes redundancy to be lost in the steering device, the vehicle speed is limited according to the remaining power amount of the power supply system, so that the power required to safely stop the vehicle can be secured. Furthermore, if the power situation deteriorates to a level where steering is difficult while the vehicle is traveling with the vehicle speed limit control being executed, control is immediately performed to decelerate the vehicle to the second reference speed (safe speed), so that the vehicle can be safely stopped. The remaining power amount of the power supply system is the amount of power obtained by subtracting the amount of power required by the vehicle to bring the vehicle speed to the upper limit speed in the safe speed holding state from the amount of power supplied by the power supply system. As a representative example, the amount of power required for steering and braking may include the amount of power required to maintain the vehicle in an activated state. Furthermore, if there is an abnormality that causes a restriction in power generation, systems that consume power may be stopped within a range that does not interfere with traveling in order to conserve the remaining power amount as much as possible.

[0022] In the above configuration, when an abnormality in the power supply system is detected, if power supply from the power generation device (33) is possible, control is performed according to a determination result of comparing the supply power of the power supply system with the first reference power and the second reference power, and if power supply from the power generation device is impossible, control is performed to forcibly decelerate and stop the vehicle.

[0023] According to this configuration, even if the power supply system is abnormal, if power supply by generation is possible, the steering device will not immediately fail and the steering will become difficult, so smooth evacuation can be achieved by controlling the vehicle speed to be gradually limited. On the other hand, if power supply by the generator is not possible, the steering device may fail and the steering will immediately become difficult, so the vehicle's safety can be ensured by starting to decelerate and stop the vehicle.

[0024] Furthermore, in the above configuration, the abnormality in the steering device is judged to be at least two abnormal states, and when the two abnormal states occur simultaneously, an upper limit speed is set to the lower of the first reference speed and the second reference speed which are set individually in accordance with each of the two abnormal states, and the vehicle speed is restricted with the upper limit speed as a target.

[0025] According to this configuration, a plurality of abnormal conditions related to the steering device are identified, and a vehicle speed limit control corresponding to the abnormal condition is selected, thereby realizing an expected safe state. Furthermore, when a plurality of abnormal conditions occur simultaneously, a vehicle speed limit control that lowers the upper limit speed is selected, thereby always selecting a safer control method.

[0026] Furthermore, in the above configuration, the power supply system has redundancy consisting of two systems for supplying power to the steering device, and a failure in one of the power supply systems can be detected as an abnormality that causes a loss of redundancy in the steering device.

[0027] According to this configuration, when a failure occurs in one of the two power supply systems and redundancy of the steering device is lost, this can be detected as an abnormality in the steering device. Effect of the Invention

[0028] According to the above configuration, when an abnormality related to the steer-by-wire steering device occurs and it is necessary to quickly stop the vehicle in a safe place, evacuation driving to move to a safe place can be performed smoothly and without hindrance. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a schematic configuration diagram of a vehicle equipped with a control device according to an embodiment of the present invention; [Diagram 2] A plan view showing a vehicle's evacuation driving situation and a graph showing an overview of vehicle speed limit control [Diagram 3] Graph showing the details of vehicle speed limit control [Figure 4]FIG. 2 is a flow chart showing an operation procedure of a control device in a vehicle system. [Diagram 5] A flow chart showing the operation procedure of the control device when a power supply system abnormality occurs. [Figure 6] A graph showing an overview of the control performed by the control device DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0031] 1 is a schematic diagram of a vehicle 1 equipped with a steering device 11 according to this embodiment. As shown in the figure, the vehicle 1 is a four-wheeled automobile having four wheels 4 supported on a vehicle body 2 via a suspension 3.

[0032] The vehicle 1 includes a power plant 5 (driving device for driving) that drives the wheels 4, and a transmission 6 (gearbox) that changes the driving force transmission mode from the power plant 5 to the wheels 4. The power plant 5 is at least one of an internal combustion engine and an electric motor, and the driving force and braking force (engine brake) of the power plant 5 are transmitted to the wheels 4. The power plant 5 is controlled in response to the accelerator operation of the driver. In addition, the transmission 6 is controlled in response to the shift operation of the driver.

[0033] Vehicle 1 also includes a steer-by-wire steering device 11 that steers wheels 4. Steering device 11 includes a rack shaft 12 (steered member), a steering wheel 13 (operation member), a steering angle sensor 14, a steering angle sensor 15, a steering actuator 16 (steered device), a reaction force actuator 17 (reaction device), and a steering torque sensor 18. Steering device 11 is a so-called shaftless steer-by-wire system in which rack shaft 12 and steering wheel 13 are not mechanically connected.

[0034] Steering wheel 13 is operated by the driver. Steering angle sensor 14 detects the steering angle by steering wheel 13. Steering angle sensor 15 detects the steering angle of wheels 4. Steering actuator 16 pushes and pulls rack shaft 12 to steer wheels 4. Reaction actuator 17 applies a reaction force to steering wheel 13 against the operating force of the driver. Steering torque sensor 18 detects steering torque acting on steering shaft 19.

[0035] Furthermore, vehicle 1 is equipped with a control device 21 (ECU), a vehicle speed sensor 22 (driving condition detection means, vehicle speed detection means), and an acceleration sensor 23. Control device 21 is composed of a processor, memory, etc., and controls steering actuator 16, reaction force actuator 17, etc. based on the detection results of sensors such as steering angle sensor 14, steering angle sensor 15, steering torque sensor 18, vehicle speed sensor 22, and acceleration sensor 23.

[0036] The vehicle 1 also includes a power supply system 31 that supplies power to the steering device 11, the control device 21, etc. The power supply system 31 includes a battery 32 (electricity storage device), a power generation device 33, and the like.

[0037] In addition, the vehicle 1 is equipped with a braking system (braking device) (not shown) that brakes the wheels 4. This braking system is controlled in response to the driver's brake operation.

[0038] Moreover, the steering device 11 has redundancy to enhance reliability. For example, the steering actuator 16 (steering device) may have redundancy consisting of two systems. Moreover, the reaction force actuator 17 (reaction force device) may have redundancy consisting of two systems. Moreover, the control device 21 may have redundancy consisting of two systems. Moreover, the power supply system 31 may have redundancy consisting of two systems.

[0039] Next, an overview of the vehicle speed limit control performed by the control device 21 will be described. Fig. 2 is a diagram showing the evacuation running situation of the vehicle 1 and an overview of the vehicle speed limit control. Fig. 2(A) is a plan view showing the evacuation running situation of the vehicle 1. Fig. 2(B) is a graph showing the overview of the vehicle speed limit control.

[0040] When an abnormality occurs in the steer-by-wire steering device 11 of the host vehicle, the host vehicle is quickly moved to a safe evacuation location and stopped there, and evacuation driving is performed. Here, the safe evacuation location is a location where the host vehicle can be stopped without interfering with traffic and safety can be ensured, and in the example shown in FIG. 2(A), it is the shoulder of the road. In the example shown in FIG. 2(A), congestion occurs in the lane near the center where the host vehicle is traveling, for example, due to a right-turn congestion. For this reason, when the host vehicle is stopped on the shoulder of the road, it is necessary to first move to an adjacent lane by lane change.

[0041] Here, in a lane where congestion is occurring, the vehicle speed is often slower than in adjacent lanes, and in order to change lanes from the congested lane to the adjacent lane, it is necessary to accelerate until the vehicle speed reaches the speed of the other adjacent lane.

[0042] At this time, if an abnormality in the steering device 11 is detected and the vehicle speed is limited by the vehicle speed limit control to a speed lower than the speed at the time the abnormality was detected, the vehicle traveling in the lane where congestion has occurred will not be able to accelerate to the same speed as other vehicles traveling in the adjacent lanes, and will not be able to change lanes to the adjacent lane or pull over to the shoulder of the road.

[0043] Therefore, in this embodiment, as shown in Figure 2 (B), when an abnormality that causes a loss of redundancy in the steering device 11 is detected, first, in the first stage (voluntary evacuation state), an upper limit speed is set to the initial speed (first reference speed), and control is performed to limit the vehicle speed with this upper limit speed as a target, next, in the second stage (forced deceleration state), an upper limit speed is set so that the speed gradually decreases from the initial speed to a predetermined safe speed (second reference speed), and control is performed to limit the vehicle speed with this upper limit speed as a target, next, in the third stage (safe speed holding state), an upper limit speed is set to the safe speed, and control is performed to limit the vehicle speed with this upper limit speed as a target.

[0044] In this way, the vehicle reaches a safe speed maintaining state, where an appropriate place to retreat is found, and if the abnormality in the steering device 11 progresses to the point where steering becomes difficult and it becomes necessary to stop the vehicle immediately, the driver decelerates the vehicle by applying the brakes to stop the vehicle.

[0045] Next, there will be described the details of the vehicle speed limit control performed by the control device 21. Fig. 3 is a graph showing the details of the vehicle speed limit control.

[0046] When the control device 21 detects an abnormality that causes a loss of redundancy in the steering device 11, it first transitions to a voluntary avoidance state (first stage). In this voluntary avoidance state, the higher of the vehicle speed at the time of abnormality detection and the allowable speed of the road on which the vehicle is traveling is set as an initial speed at the time of abnormality occurrence (first reference speed), an upper limit speed is set to that speed, and control is performed to limit the vehicle speed with the upper limit speed as a target.

[0047] If the vehicle speed at the time of the abnormality detection is higher than the allowable speed of the road on which the vehicle is traveling, the vehicle speed at the time of the abnormality detection is set to the upper limit speed, thereby preventing the vehicle from suddenly decelerating and enabling the vehicle to smoothly evacuate.

[0048] On the other hand, if the permissible speed of the road on which the vehicle is traveling is higher than the vehicle speed of the vehicle at the time of abnormality detection, the permissible speed of the road on which the vehicle is traveling is set as the upper speed limit. This makes it possible to accelerate the vehicle up to the permissible speed of the road, so that the vehicle can smoothly evacuate in line with the flow of traffic, specifically, by changing lanes to move to a safe place, without impeding the driving of other vehicles in the vicinity.

[0049] The permissible speed on a road may be set according to the road traffic environment and the driving location (urban area, expressway, etc.). For example, in the case of freeways in the United States, it may be set to 80 km / h, which is the legal minimum speed. In addition, the permissible speed may be set by recognizing the preceding vehicle and signs using cameras and radars used in the driving assistance system installed in the vehicle.

[0050] In this way, in the voluntary evacuation state, unnecessary high speed driving is restricted, but necessary acceleration and deceleration are permitted, allowing driving with a relatively high degree of freedom, and ensuring freedom of movement such as lane changing. Therefore, voluntary (active) evacuation driving by the driver's steering operation can be performed smoothly and without hindrance.

[0051] Next, when a predetermined duration of the voluntary avoidance state has elapsed, the vehicle transitions to a forced deceleration state (second stage). In this forced deceleration state, an upper limit speed is set so that the vehicle speed gradually decreases from an initial speed (first reference speed) to a predetermined target safe speed (second reference speed), and the vehicle speed is restricted to the upper limit speed.

[0052] Here, the initial speed (first reference speed) is the upper limit speed for the voluntary avoidance state, i.e., the upper limit speed set when an abnormality in the steering device 11 is detected and the vehicle transitions to the voluntary avoidance state, and is the higher of the vehicle speed at the time of the abnormality detection and the allowable speed of the road on which the vehicle is traveling. On the other hand, the safe speed (second reference speed) is the speed at which the vehicle can be stopped instantly and safely by decelerating the vehicle through the driver's brake operation without the need for steering by the driver.

[0053] The upper speed limit in the forced deceleration state is the vehicle speed when the vehicle is decelerated at a deceleration rate without the driver operating the accelerator or brake. This deceleration rate is set within a range of deceleration rates at which the driver can operate the steering wheel calmly. For example, it may be set based on the deceleration rate caused only by the braking force of the power plant 5 (driving device for driving). The vehicle speed based on the deceleration rate thus set is the upper speed limit. In addition to the engine brake, braking force caused by regeneration or friction may be used in combination depending on the set deceleration rate.

[0054] In this manner, in the forced deceleration region, the vehicle is decelerated at a deceleration rate due to engine braking (including regenerative braking, etc.), so that the vehicle can be reliably decelerated to a safe speed (second reference speed) within a predetermined time without the driver performing a brake operation.

[0055] In this embodiment, the vehicle speed is controlled to be the upper limit speed when decelerated by the deceleration caused by engine braking (including regenerative braking, etc.).At this time, since the deceleration is constant, the duration of the forced deceleration state becomes shorter as the initial speed at the time the abnormality occurs becomes lower.

[0056] On the other hand, as shown in Fig. 3 as a first modified example, the duration of the forced deceleration state may be constant. In this case, the deceleration decreases as the initial speed at the time of occurrence of the abnormality decreases, so that the driver can make a safe evacuation run by steering operation with plenty of time. Also, as shown in Fig. 3 as a second modified example, the deceleration may be constant, and the duration of the voluntary evacuation state before the forced deceleration state may be lengthened as the initial speed at the time of occurrence of the abnormality decreases.

[0057] Next, when the vehicle speed drops to a safe speed (second reference speed) in the forced deceleration region, the system transitions to a safe speed maintenance state. In this safe speed maintenance state (third stage), an upper limit speed is set to the safe speed, and control is performed to limit the vehicle speed with the upper limit speed as a target.

[0058] The safe speed (second reference speed) is a speed at which the vehicle can be stopped immediately and safely by decelerating the vehicle through the driver's brake operation without the driver needing to steer. In other words, in the safe speed maintaining state, even if the abnormality in the steering device 11 progresses to the point where steering becomes difficult, the vehicle can be stopped immediately and safely by decelerating the vehicle through the driver's brake operation.

[0059] Therefore, after transitioning to the safe speed maintenance state, the driver drives the vehicle at a speed equal to or less than the safe speed until it reaches a suitable stopping location, and then stops the vehicle by applying the brakes at the necessary timing. Here, even if the vehicle suddenly becomes difficult to steer, the driver can safely stop the vehicle by applying the brakes.

[0060] In addition, the speed range below the upper limit speed in the voluntary evacuation state, the forced deceleration state, and the safe speed maintenance state is the acceleration / deceleration permitted range. If the vehicle speed of the host vehicle is included in this acceleration / deceleration permitted range, the driver can freely accelerate or decelerate the host vehicle by operating the accelerator and brakes. This allows the host vehicle to smoothly perform evacuation driving.

[0061] In addition, the speed region of a predetermined width below the upper speed limit in the voluntary evacuation state, the forced deceleration state, and the safe speed maintenance state is a sudden acceleration prohibition region. If the vehicle speed of the host vehicle is included in this sudden acceleration prohibition region, the host vehicle can be accelerated by the driver's accelerator operation, but acceleration that exceeds a predetermined value is prohibited. This makes it possible to prevent the host vehicle from suddenly accelerating and temporarily exceeding the upper speed limit.

[0062] Moreover, the speed region above the upper limit speed in the voluntary evacuation state, the forced deceleration state, and the safe speed maintenance state is a driving force limit region, and in this driving force limit region, control is performed to limit the driving force of the power plant 5 regardless of the accelerator operation of the driver. As a result, when the vehicle speed exceeds the upper limit speed, the vehicle speed can be quickly decelerated to below the upper limit speed. At this time, regeneration and friction braking may be used in combination depending on the amount of excess speed from the upper limit speed and the rate at which the vehicle speed deviates.

[0063] Next, the control of the vehicle system will be described with reference to Fig. 4, which is a flow chart showing the operation procedure of the control device 21 in the vehicle system.

[0064] Even if there is no abnormality in the steering device 11 itself, the power supply system 31 may enter a state where it is temporarily unable to guarantee the power required by the steering device 11. Such a state of the power supply system 31 may occur when the battery 32 constituting the power supply system 31 has deteriorated, when the output of the battery 32 has decreased due to low temperature, when the vehicle system is started up in a state where the remaining power of the battery 32 is insufficient due to long-term storage, etc.

[0065] In such a case, reliable operation of the steering device 11 cannot be guaranteed, and steering may become difficult, so it may not be possible to perform evacuation driving using control that gradually limits the vehicle speed (stepwise vehicle speed limit control).

[0066] Therefore, in this embodiment, the control method is switched depending on the magnitude of the power supplied by the power supply system 31 that supplies power to the steering device 11. However, there are cases where the state of the power supply system cannot be accurately grasped immediately after the vehicle system is started. Until it is determined that the vehicle is normal, traveling is temporarily not permitted, or traveling is permitted only up to a safe speed (second reference speed).

[0067] Specifically, as shown in Fig. 4, when the vehicle system is started, the control device 21 first judges whether the power required for the steering device 11 during normal control is guaranteed, that is, whether the power required for operating the steering device 11 to achieve and maintain a safe state, that is, a state in which the vehicle travels at a safe vehicle speed at which the vehicle can be stopped immediately, is guaranteed (step ST1). At this time, it is judged whether the power supplied by the power supply system 31 is equal to or greater than a first reference power. This first reference power is a threshold value for judging whether the power required for the steering device 11 during normal control is guaranteed.

[0068] Here, if the required power of the steering device 11 during normal control is guaranteed (ST1: Yes), normal control is performed (step ST2).

[0069] On the other hand, if the power required by the steering device 11 during normal control is not guaranteed (ST1: No), then it is determined whether or not the power required by the steering device 11 during first vehicle speed limit control is guaranteed (step ST3). At this time, it is determined whether or not the power supplied by the power supply system 31 is equal to or greater than a second reference power. This second reference power is a threshold value for determining whether or not the power required by the steering device 11 during first vehicle speed limit control is guaranteed.

[0070] Here, if the power required by the steering device 11 during the first vehicle speed limit control is guaranteed (ST3: Yes), the first vehicle speed limit control is implemented (step ST4). In this first vehicle speed limit control, control is performed to limit the vehicle speed to a maximum speed set according to the remaining power amount of the power supply system 31. Note that the remaining power amount of the power supply system 31 is the amount of power obtained by subtracting the amount of power required for the vehicle from the amount of power supplied by the power supply system.

[0071] On the other hand, if the power required by the steering device 11 during the first vehicle speed limit control is not guaranteed (ST3: No), then it is determined whether or not the power required by the steering device 11 during the second vehicle speed limit control is guaranteed (step ST5). At this time, it is determined whether or not the power supplied by the power supply system 31 is equal to or greater than a third power value. This third power value is a threshold value for determining whether or not the power required by the steering device 11 during the second vehicle speed limit control is guaranteed.

[0072] Here, if the required power of the steering device 11 during the second vehicle speed limit control is guaranteed (ST5: Yes), the second vehicle speed limit control is implemented (step ST6). In this second vehicle speed limit control, control is performed to limit the vehicle speed by targeting a safe speed as an upper limit speed.

[0073] On the other hand, if the required power of the steering device 11 during the second vehicle speed limit control is not guaranteed (ST5: No), the host vehicle is put into a traveling prohibited state in which starting of the host vehicle is prohibited (step ST7).

[0074] In this manner, in this embodiment, the control (first vehicle speed limit control) that limits the vehicle speed is performed according to the remaining power amount of the power supply system 31, so that the power required to safely stop the host vehicle can be secured. That is, when the vehicle speed is high, the power required to safely stop the host vehicle increases, so by setting the upper limit speed when limiting the vehicle speed in the vehicle speed limit control according to the remaining power amount of the power supply system 31, the host vehicle can be stopped safely.

[0075] In addition, in this embodiment, if the power situation deteriorates to the point where steering is difficult during normal driving or while driving with the first vehicle speed limit control, the control immediately switches to a control (second vehicle speed limit control) that decelerates the vehicle to a safe speed (second reference speed), allowing the vehicle to be stopped safely.

[0076] Next, a description will be given of the control when an abnormality (power failure) occurs in the power supply system 31. Fig. 5 is a flow diagram showing the operation procedure of the control device 21. Fig. 6 is a graph showing an overview of the control performed by the control device 21. Fig. 6(A) shows the case of stepwise vehicle speed limit control, Fig. 6(B) shows the case of forced deceleration control, and Fig. 6(C) shows the case of forced stop control.

[0077] If an abnormality (power failure) occurs in the power supply system 31, it may become difficult to travel due to lack of electricity, and the steering device 11 to which power is supplied by the power supply system 31 may also be unable to operate normally, resulting in a state similar to that in which the redundancy of the steering device 11 itself is lost. Therefore, before steering becomes difficult, control is performed to put the host vehicle into a safe speed maintenance state or a stopped vehicle maintenance state.

[0078] Specifically, as shown in FIG. 5, when the control device 21 detects an abnormality (power failure) in the power supply system 31, it first determines whether or not power supply from the power generation device 33 is possible (step ST11).

[0079] If power supply from the power generation device 33 is possible (ST11: Yes), then it is determined whether the power required by the steering device 11 can be guaranteed by the power supplied by the power generation device 33 (step ST12). Note that if the battery 32 has deteriorated or the output of the battery 32 has decreased, the power required by the steering device 11 may not be guaranteed by the power supplied by the power generation device 33, although travel is possible using the power supplied by the power generation device 33.

[0080] Here, if the power required by the steering device 11 is guaranteed by the power supply of the power generation device 33 (ST12: Yes), stepwise vehicle speed limit control is performed (step ST13). In this stepwise vehicle speed limit control, as shown in Fig. 6(A), control is performed to smoothly perform evacuation driving to move to a safe place such as a road shoulder by sequentially transitioning to three speed limit states (voluntary evacuation state, forced deceleration state, safe speed maintenance state).

[0081] On the other hand, if the power required by the steering device 11 is not guaranteed by the power supply of the power generation device 33 (ST12: No), forced deceleration control is performed (step ST14). In this forced deceleration control, as shown in Fig. 6(B), a speed limit is imposed that gradually reduces the upper limit speed, thereby forcibly decelerating the host vehicle to a safe speed.

[0082] Furthermore, if the vehicle cannot travel using the power supplied by the power generation device 33 (ST11: No), forced stop control is performed (step ST15). In this forced stop control, as shown in Fig. 6(C), control is performed to forcibly stop the host vehicle by gradually lowering the upper speed limit. After the host vehicle has stopped, control is performed to keep the host vehicle in a stopped state by a vehicle stop maintenance function, specifically, an EPB (electric parking brake) and the parking position of the transmission 6.

[0083] In this embodiment, even if the power supply system 31 is abnormal, if power supply by power generation is possible, the steer-by-wire steering device 11 will not immediately fail and steering will not become difficult, so smooth evacuation travel is possible by controlling to gradually limit the vehicle speed. On the other hand, if power supply by the power generation device 33 is not possible, there is a possibility that the steer-by-wire steering device 11 will immediately fail and steering will not become difficult, so the safety of the host vehicle can be ensured by quickly decelerating and stopping the vehicle.

[0084] However, there are various types of abnormalities in the steer-by-wire steering device 11, and the degree of influence of the abnormalities on the traveling of the vehicle 1 also varies. Therefore, with regard to the abnormality of the steer-by-wire steering device 11, at least two abnormal states may be detected in a distinguishable manner. Also, a first reference speed and a second reference speed may be set individually for each of the at least two abnormal states, and an upper limit speed may be set to either the first reference speed or the second reference speed corresponding to the detected abnormal state, and the vehicle speed may be limited with the upper limit speed as a target. In this way, by distinguishing a plurality of abnormal states related to the steering device 11 and selecting a vehicle speed limit control corresponding to the abnormal state, the host vehicle can be brought into a safe speed maintenance state or a stopped vehicle maintenance state.

[0085] Also, when two abnormal conditions occur simultaneously, the upper limit speed may be set to the lower of the first and second reference speeds, and the vehicle speed may be limited to the upper limit speed. In this way, when multiple abnormal conditions occur simultaneously, a safer control method can be selected by selecting the vehicle speed limit control that lowers the upper limit speed.

[0086] In addition, when the vehicle speed is slowed down by the driver's braking operation and becomes lower than the upper limit vehicle speed set in the forced deceleration state, control is performed to decelerate the vehicle to the lower vehicle speed as the upper limit speed.

[0087] Although the description of the specific embodiment is finished above, the present invention can be widely modified and implemented without being limited to the above embodiment. In addition, the specific configuration, arrangement, quantity, angle, procedure, etc. of each member or part can be appropriately changed within the scope of the gist of the present invention. On the other hand, all of the components shown in the above embodiment are not necessarily required and can be appropriately selected. In addition, the present invention can be implemented not only when a steer-by-wire steering device fails, but also when system performance deteriorates due to overheating protection of the steering device, or when an abnormality occurs in which redundancy is lost in a brake-by-wire braking device or automatic driving. [Explanation of symbols]

[0088] 1 vehicle 2. Body 3. Suspension 4 wheels 5 Power plant (driving device) 6. Transmission 11 Steering gear 12 Rack shaft (steering member) 13 Steering wheel (operating member) 14 Steering angle sensor 15 Steering angle sensor 16 Steering actuator (steering device) 17 Reaction actuator (reaction device) 18 Steering torque sensor 19 Steering shaft 21 Control device 22 Vehicle speed sensor 23 Acceleration Sensor 31 Power System 32 Battery 33 Power generation equipment

Claims

1. A vehicle control device is mounted on a vehicle having a steering device in which an operating member operated by a driver and a steering member for steering wheels are mechanically separated and which operates by power supplied from a power supply system, When an abnormality that causes a loss of redundancy in the steering device is detected, In the first stage, an upper limit speed is set to the first reference speed, and the vehicle speed is restricted to the upper limit speed for a predetermined duration. In a second stage, an upper limit speed is set so as to gradually decrease from the first reference speed to a predetermined target second reference speed, and the vehicle speed is restricted with the upper limit speed as a target.

2. The vehicle control device as described in Claim 1, characterized in that the first stage continues for the duration so as to enable voluntary evacuation driving by the driver's steering operation.

3. the steering device includes a reaction device that applies a reaction force to the operating member, and a steering device that steers the wheels, and at least one of the reaction device and the steering device has redundancy consisting of two systems; 2. The vehicle control device according to claim 1, wherein a failure in one of the two systems is detected as an abnormality that causes a loss of redundancy in the steering device.

4. A vehicle control device mounted on a vehicle equipped with a steering device that operates using power supplied from a power supply system, in which an operating member operated by a driver and a steering member that steers the wheels are mechanically separated, comprising: When an abnormality that causes a loss of redundancy in the steering device is detected, In the first stage, an upper limit speed is set to the first reference speed, and the vehicle speed is restricted to the upper limit speed as a target. Next, in a second stage, an upper speed limit is set so that the upper speed limit is gradually decreased from the first reference speed to a predetermined second reference speed as a target, and the vehicle speed is limited to the upper speed limit.

2. A vehicle control device according to claim 1, wherein the first reference speed is set to the higher of the vehicle speed of the vehicle when the abnormality is detected and a permissible speed of the road on which the vehicle is traveling.

5. A vehicle control device mounted on a vehicle equipped with a steering device that operates using power supplied from a power supply system, in which an operating member operated by a driver and a steering member that steers the wheels are mechanically separated, comprising: When an abnormality that causes a loss of redundancy in the steering device is detected, In the first stage, an upper limit speed is set to the first reference speed, and the vehicle speed is restricted to the upper limit speed as a target. Next, in a second stage, an upper speed limit is set so that the upper speed limit is gradually decreased from the first reference speed to a predetermined second reference speed as a target, and the vehicle speed is limited to the upper speed limit. The vehicle control device according to claim 1, wherein the upper limit speed in the second stage is set based on the deceleration in a state in which the driver is not operating the accelerator or the brake.

6. 6. The vehicle control device according to claim 1, wherein, when the speed of the host vehicle is within a speed range of a predetermined width that is equal to or less than the upper speed limit, acceleration that exceeds a predetermined value is prohibited.

7. 7. The vehicle control device according to claim 1, further comprising: a limiting unit that limits a driving force of a driving device for traveling when the vehicle speed exceeds the upper limit speed.

8. When the power supply of the power supply system is equal to or greater than a predetermined first reference power, normal control is performed; When the power supply of the power supply system is less than the first reference power and is equal to or greater than a predetermined second reference power, a control is performed to limit a vehicle speed to an upper limit speed set according to a remaining power amount of the power supply system; 8. The vehicle control device according to claim 1, wherein when the power supplied by the power supply system is less than the second reference power, the vehicle speed is limited to the second reference speed.

9. A vehicle control device mounted on a vehicle equipped with a steering device that operates using power supplied from a power supply system, in which an operating member operated by a driver and a steering member that steers the wheels are mechanically separated, comprising: When an abnormality that causes a loss of redundancy in the steering device is detected, In the first stage, an upper limit speed is set to the first reference speed, and the vehicle speed is restricted to the upper limit speed as a target. Next, in a second stage, an upper speed limit is set so that the upper speed limit is gradually decreased from the first reference speed to a predetermined second reference speed as a target, and the vehicle speed is limited to the upper speed limit. When the power supply of the power supply system is equal to or greater than a predetermined first reference power, normal control is performed; When the power supply of the power supply system is less than the first reference power and is equal to or greater than a predetermined second reference power, a control is performed to limit a vehicle speed to an upper limit speed set according to a remaining power amount of the power supply system; When the power supply of the power supply system is less than the second reference power, a control is performed to limit the vehicle speed to the second reference speed. When an abnormality in the power supply system is detected, When the power generation device is capable of supplying power, the power supply system is controlled in accordance with a result of a comparison between the first reference power and the second reference power; A vehicle control device comprising: a control unit for forcibly decelerating and stopping a host vehicle when the power generation device is unable to supply electric power.

10. A vehicle control device mounted on a vehicle equipped with a steering device that operates using power supplied from a power supply system, in which an operating member operated by a driver and a steering member that steers wheels are mechanically separated, comprising: When an abnormality that causes a loss of redundancy in the steering device is detected, In the first stage, an upper limit speed is set to the first reference speed, and the vehicle speed is restricted to the upper limit speed as a target. Next, in a second stage, an upper speed limit is set so that the upper speed limit is gradually decreased from the first reference speed to a predetermined second reference speed as a target, and the vehicle speed is limited to the upper speed limit. The abnormality of the steering device is determined to be in at least two abnormal states, a vehicle speed limiting device that limits a vehicle speed so as not to exceed an upper limit speed when two of the abnormal conditions occur simultaneously, the vehicle speed limiting device being configured to limit ...

11. The power supply system has redundancy consisting of two systems for supplying power to the steering device, 11. The vehicle control device according to claim 1, wherein a failure in one of the power supply systems is detected as an abnormality that causes a loss of redundancy in the steering device.

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