JP7628898B2 - Vehicle control device - Google Patents

Description

The present invention relates to a control device that controls a steer-by-wire steering device installed in a vehicle.

In a steer-by-wire steering system, the steering wheel operated by the driver is mechanically separated from the rack shaft that steers the wheels. 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.

Such steer-by-wire steering devices are designed to be reliable 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 occurs that causes a loss of redundancy, 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 there.

A known technology for controlling abnormalities in steer-by-wire steering devices is to restrict the vehicle speed to reduce power consumption when an abnormality occurs in the generator, thereby ensuring power to be supplied to the steering device and allowing the driver to steer to an evacuation site (see Patent Document 1).

Patent No. 5013312

Now, 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 the shoulder of the road, and park there to perform evacuation maneuvering. At this time, the vehicle must drive in line 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 conventional technology, makes it difficult to drive in line with the flow of traffic, and there is a problem in that evacuation maneuvering cannot be performed smoothly and without hindrance.

In view of the above background, the present invention aims to provide a vehicle control device that can smoothly and smoothly 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.

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) that operates with power supplied from a power supply system (31) and 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 when an abnormality that causes a loss of redundancy in the steering device is detected, 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 that the speed gradually decreases 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.

According to this configuration, if 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 suddenly restricted to a low speed, so freedom of movement such as lane changes can be ensured. This allows the vehicle to smoothly and unhinderedly evacuate to a safe location. Note that 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 this upper limit speed as a target.

In addition, in the above configuration, the steering device includes a reaction device (reaction 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 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.

With this configuration, if a failure occurs in one of the two systems, 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.

In the above configuration, the first reference speed may be set to the higher of the vehicle speed when the abnormality is detected and the allowable speed of the road on which the vehicle is traveling.

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 prevents sudden deceleration of the vehicle, enabling 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, making 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.

In addition, in the above configuration, the upper limit speed in the second stage may be set based on the deceleration when the driver is not operating the accelerator or brake.

With this configuration, the vehicle can be reliably decelerated to the second reference speed (safety speed) within a specified time without the driver having to perform any special operation. This braking force includes not only engine braking, but also regenerative and frictional braking forces. It is also preferable that this braking force be set to a deceleration that allows the driver to calmly steer the vehicle.

In addition, in the above configuration, if the vehicle speed is within a predetermined speed range below the upper speed limit, acceleration that exceeds a predetermined value may be prohibited.

With this configuration, when the vehicle speed is near the upper speed limit, sudden acceleration is prohibited, so the vehicle can be prevented from suddenly accelerating and temporarily exceeding the upper speed limit.

In addition, in the above configuration, if the vehicle speed exceeds the upper speed limit, the driving force of the driving device (power plant 5) may be limited.

With 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 to the upper limit speed.

In addition, in the above configuration, 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 equal to or greater than a predetermined second reference power, control is performed to limit the vehicle speed to a maximum speed set according to the remaining power amount of the power supply system, and when the power supply of the power supply system is less than the second reference power, control is performed to limit the vehicle speed to the second reference speed.

According to this configuration, even if there is no abnormality that causes the steering device to lose redundancy, the vehicle speed is limited according to the remaining power 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 point where steering is difficult while driving with the vehicle speed limit control being executed, control is performed to immediately decelerate the vehicle to the second reference speed (safe speed), so that the vehicle can be safely stopped. The remaining power 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 for the safe speed maintenance 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 to the extent that does not interfere with driving in order to conserve the remaining power as much as possible.

In addition, 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 the determination result of comparing the power supply from 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.

With this configuration, even if the power supply system is abnormal, if power can be supplied by generating electricity, the steering device will not immediately fail and 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 cannot be supplied by the generator, there is a possibility that the steering device will fail and steering will immediately become difficult, so the vehicle's safety can be ensured by starting to decelerate and stopping the vehicle.

In addition, in the above configuration, the abnormality of the steering device is judged to be at least two abnormal states, and if the two abnormal states occur simultaneously, the upper limit speed is set to the lower of the first reference speed and the second reference speed, which are set individually according to each of the two abnormal states, and the vehicle speed is restricted with the upper limit speed as a target.

With this configuration, multiple abnormal conditions related to the steering device are identified, and vehicle speed limit control corresponding to the abnormal condition is selected, thereby realizing an expected safe state. Furthermore, when multiple abnormal conditions occur simultaneously, a vehicle speed limit control that lowers the upper limit speed is selected, making it possible to always select a safer control method.

In addition, in the above configuration, the power supply system has redundancy consisting of two systems that supply power to the steering device, and it is preferable to detect a failure in one of the power supply systems as an abnormality that causes a loss of redundancy in the steering device.

With this configuration, if 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.

With the above configuration, if an abnormality occurs related to the steer-by-wire steering device and it is necessary to stop the vehicle quickly in a safe place, evacuation driving to move to a safe place can be performed smoothly and without any problems.

FIG. 1 is a schematic configuration diagram of a vehicle equipped with a control device according to an embodiment of the present invention; A plan view showing a vehicle's evacuation driving situation and a graph showing an overview of vehicle speed limit control Graph showing the details of vehicle speed limit control FIG. 2 is a flow chart showing an operation procedure of a control device in a vehicle system. A flow chart showing the operation procedure of the control device when a power supply system abnormality occurs. A graph showing an overview of the control performed by the control device

The following describes in detail an embodiment of the present invention with reference to the drawings.

Figure 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.

The vehicle 1 is equipped with 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.

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

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

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

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

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

The steering device 11 also has redundancy to improve reliability. For example, the steering actuator 16 (steering device) may have redundancy consisting of two systems. The reaction force actuator 17 (reaction force device) may have redundancy consisting of two systems. The control device 21 may have redundancy consisting of two systems. The power supply system 31 may have redundancy consisting of two systems.

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 driving situation of the vehicle 1 and an overview of the vehicle speed limit control. FIG. 2(A) is a plan view showing the evacuation driving situation of the vehicle 1. FIG. 2(B) is a graph showing an overview of the vehicle speed limit control.

If 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 (evacuation run). Here, a safe evacuation location is a location where the host vehicle can be stopped safely without interfering with traffic, 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 has occurred in the lane near the center in which the host vehicle is traveling, for example due to a right-turn congestion. For this reason, if the host vehicle is to be stopped on the shoulder of the road, it is necessary to first move to an adjacent lane by lane changing.

Here, the vehicle speed in the congested lane is often slower than in the 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.

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 which 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.

In this embodiment, as shown in FIG. 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), the upper limit speed is set to the initial speed (first reference speed), and control is performed to limit the vehicle speed with the upper limit speed as the target. Next, in the second stage (forced deceleration state), the 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 the upper limit speed as the target. Next, in the third stage (safe speed maintenance state), the upper limit speed is set to the safe speed, and control is performed to limit the vehicle speed with the upper limit speed as the target.

In this way, the vehicle reaches a state of maintaining a safe speed. At this point, if a suitable 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 will decelerate the vehicle by applying the brakes to bring it to a halt.

Next, we will explain the details of the vehicle speed limit control performed by the control device 21. Figure 3 is a graph showing the details of the vehicle speed limit control.

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 evacuation state (first stage). In this voluntary evacuation state, the higher of the vehicle's speed at the time of abnormality detection and the allowable speed of the road on which the vehicle is traveling is set as the 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 that upper limit speed as the target.

Here, if the vehicle speed at the time of abnormality detection is higher than the allowable speed of the road on which the vehicle is traveling, the vehicle speed at the time of abnormality detection is set to the upper limit speed. This prevents the vehicle from suddenly decelerating, enabling smooth evacuation driving.

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 the abnormality was detected, the permissible speed of the road on which the vehicle is traveling is set to the upper speed limit. This makes it possible to accelerate the vehicle up to the permissible speed of the road, enabling the vehicle to smoothly evacuate in line with the flow of traffic, specifically by changing lanes to move to a safe location, without impeding the driving of other vehicles in the vicinity.

The permissible speed for a road may be set according to the road traffic environment and the driving location (urban area, highway, 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 vehicle ahead and signs using cameras and radars used in the driving assistance system installed in the vehicle.

In this way, in the voluntary evacuation state, unnecessary high speed driving is restricted, but necessary acceleration and deceleration is permitted, allowing for a relatively high degree of freedom in driving and ensuring freedom of movement such as lane changes. This allows the driver to operate the steering wheel to voluntarily (actively) evacuate smoothly and without hindrance.

Next, when a predetermined duration of the voluntary evacuation 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 gradually decreases from the initial speed (first reference speed) to a predetermined target safe speed (second reference speed), and control is performed to limit the vehicle speed with the upper limit speed as the target.

The initial speed (first reference speed) is the upper limit speed for the voluntary evacuation 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 evacuation 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 using the brakes of the driver without the need for steering by the driver.

The upper limit speed in the forced deceleration state is the vehicle speed when the vehicle decelerates without the driver operating the accelerator or brake. This deceleration is set within a range of deceleration at which the driver can calmly steer the vehicle. For example, it may be set based on the deceleration caused only by the braking force of the power plant 5 (driving device for driving). The vehicle speed based on the deceleration thus set is the upper limit speed. Depending on the deceleration set, braking force due to regeneration or friction may be used in addition to engine braking.

In this way, in the forced deceleration region, the vehicle is decelerated by the deceleration caused by engine braking (including regenerative braking, etc.). This allows the vehicle to be reliably decelerated to a safe speed (second reference speed) within a specified time without the driver having to apply the brakes.

In this embodiment, the vehicle speed is controlled so that the upper limit speed is the vehicle speed when decelerated by engine braking (including regenerative braking, etc.), and since the deceleration is constant, the duration of the forced deceleration state becomes shorter as the initial speed at the time of the abnormality becomes lower.

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 abnormality occurrence decreases, allowing the driver to steer away with ease. Also, as shown in FIG. 3 as a second modified example, the deceleration may be constant, and the duration of the voluntary evacuation state preceding the forced deceleration state may be lengthened as the initial speed at the time of abnormality occurrence decreases.

Next, when the vehicle speed drops to a safe speed (second reference speed) in the forced deceleration region, the vehicle 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 the target.

The safe speed (second reference speed) is a speed at which the vehicle can be stopped immediately and safely by the driver slowing down through braking without the driver needing to steer. In other words, in the safe speed maintenance 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 the driver slowing down through braking.

Therefore, after transitioning to the safe speed maintenance state, the driver simply drives the vehicle at a speed below the safe speed until it reaches a suitable stopping location, and then applies the brakes at the necessary timing to stop the vehicle. Even if the vehicle suddenly becomes difficult to steer, the driver can apply the brakes to safely stop the vehicle.

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 vehicle is included in this acceleration/deceleration permitted range, the driver can freely accelerate or decelerate the vehicle by operating the accelerator and brakes. This allows the vehicle to smoothly evacuate.

In addition, the speed region of a predetermined width below the upper limit speed 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 limit speed.

In addition, the speed range 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 range, and in this driving force limit range, 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.

Next, the control of the vehicle system will be described. Figure 4 is a flow diagram showing the operation procedure of the control device 21 in the vehicle system.

Even if there is no abnormality in the steering device 11 itself, the power supply system 31 may temporarily enter a state where it cannot 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 is deteriorated, when the output of the battery 32 is reduced due to low temperatures, or 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.

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

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).

Specifically, as shown in FIG. 4, when the vehicle system is started, the control device 21 first determines whether the power required by the steering device 11 during normal control is guaranteed, that is, whether the power required to operate the steering device 11 and 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 determined 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 determining whether the power required by the steering device 11 during normal control is guaranteed.

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

On the other hand, if the power required by the steering device 11 during normal control is not guaranteed (ST1: No), it is next determined whether the power required by the steering device 11 during the first vehicle speed limit control is guaranteed (step ST3). At this time, it is determined whether 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 the power required by the steering device 11 during the first vehicle speed limit control is guaranteed.

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 by the vehicle from the amount of power supplied by the power supply system.

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), it is next determined whether 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 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 the power required by the steering device 11 during the second vehicle speed limit control is guaranteed.

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 with a target safe speed as the upper limit speed.

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 vehicle enters a traveling prohibited state in which starting of the vehicle is prohibited (step ST7).

In this embodiment, the vehicle speed is limited according to the remaining power of the power supply system 31 (first vehicle speed limit control), so the power required to safely stop the vehicle can be secured. In other words, when the vehicle speed is high, the power required to safely stop the vehicle increases, so the upper limit speed when limiting the vehicle speed in the vehicle speed limit control is set according to the remaining power of the power supply system 31, so the vehicle can be stopped safely.

In addition, in this embodiment, if the power situation deteriorates to the point where steering is difficult while the vehicle is running normally or while running under 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.

Next, the control when an abnormality (power failure) occurs in the power supply system 31 will be described. 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.

If an abnormality (power failure) occurs in the power supply system 31, it may become difficult to drive due to lack of power, 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 steering device 11 itself has lost redundancy. Therefore, before steering becomes difficult, control is performed to put the vehicle into a safe speed maintenance state or a stopped state.

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 can be supplied by the power generation device 33 (step ST11).

If power supply from the power generation device 33 is possible (ST11: Yes), it is next determined whether the power required by the steering device 11 is 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, even though the vehicle can be driven using the power supplied by the power generation device 33.

If the power required by the steering device 11 is guaranteed by the power supply from 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), the vehicle is controlled to smoothly perform evacuation driving to move to a safe place such as the shoulder of the road by sequentially transitioning to three speed limit states (voluntary evacuation state, forced deceleration state, and safe speed maintenance state).

On the other hand, if the power required by the steering device 11 is not guaranteed by the power supply from 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 speed limit, forcing the vehicle to decelerate to a safe speed.

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), a control is performed to forcibly stop the vehicle by gradually lowering the upper speed limit. After the vehicle has stopped, a stop-maintaining function, specifically, the EPB (electric parking brake) and the parking position of the transmission 6, is used to control the vehicle to be in a stop-maintaining state.

In this embodiment, even if the power supply system 31 is abnormal, if power supply by generation is possible, the steer-by-wire steering device 11 will not immediately fail and steering will not become difficult, so smooth evacuation driving is possible by controlling to gradually limit the vehicle speed. On the other hand, if power supply by the generator 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 vehicle can be ensured by quickly decelerating and stopping the vehicle.

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, it is possible to detect at least two abnormal states in relation to the abnormality of the steer-by-wire steering device 11 in a distinguishable manner. Also, it is possible to set a first reference speed and a second reference speed individually for each of the at least two abnormal states, set an upper limit speed to either the first reference speed or the second reference speed corresponding to the detected abnormal state, and limit the vehicle speed with the upper limit speed as a target. In this way, by distinguishing between multiple abnormal states related to the steering device 11 and selecting vehicle speed limit control according to the abnormal state, it is possible to keep the host vehicle in a safe speed maintenance state or a stopped state.

In addition, 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 results in the lower upper limit speed.

In addition, if 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.

Although the description of the specific embodiment is now complete, the present invention is not limited to the above embodiment and can be modified in a wide range of ways. In addition, the specific configuration, arrangement, quantity, angle, procedure, etc. of each member or part can be changed as appropriate without departing from the spirit of the present invention. On the other hand, not all of the components shown in the above embodiment are necessarily required and can be selected as appropriate. Furthermore, the present invention can be implemented not only when a steer-by-wire steering device fails, but also when system performance deteriorates, such as when the steering device is overheated, or when an abnormality occurs that causes a loss of redundancy in a brake-by-wire braking device or automatic driving.

1 Vehicle 2 Vehicle body 3 Suspension 4 Wheels 5 Power plant (driving device)
6 Transmission 11 Steering device 12 Rack shaft (steering member)
13 Steering wheel (operating member)
14 Steering angle sensor 15 Turning angle sensor 16 Turning actuator (turning 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 supply system 32 battery 33 power generation device

Claims (11)

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 according to claim 1, wherein the first stage continues for the duration period so as to enable a driver to voluntarily evacuate the vehicle by operating a steering wheel. 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. 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 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. 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 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. 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. 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 a vehicle speed of the vehicle exceeds the upper limit speed. 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. 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 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. 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 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 ... 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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