Control method for vehicle and control device for vehicle

Abstract

According to the present invention, when it is predicted from the relationship with slip ratio or slip amount that a wheel drive force that is the drive force transmitted to a wheel will be below running resistance, a vehicle (1) increases and thereby corrects the drive force transmitted to the wheel to correspond to the slip ratio or slip amount at which the drive force transmitted to the wheel will be above running resistance. The vehicle (1) can predict and thereby avoid unfavorable travel states caused by slip, unfavorable travel states caused by insufficient drive force for traveling over a step, etc.

Description

Vehicle control method and vehicle control device

[0001] The present invention relates to a vehicle control method and a vehicle control device.

[0002] For example, Patent Document 1 discloses a technology that can increase the driving torque before it is too late to start and accelerate a vehicle even in special conditions such as deep snow, sand, or mud.

[0003] In Patent Document 1, the drive torque is controlled based on the slip amount or slip ratio of the drive wheels, and the drive torque is increased after the occurrence of slip is detected.

[0004] However, in Patent Document 1, slippage may cause the drive wheels to sink (be buried) in deep snow, sand, mud, etc., which may further worsen special conditions such as deep snow, sand, or mud.

[0005] In other words, Patent Document 1 aims to improve the vehicle's running conditions by increasing the drive torque after slippage occurs, but does not take into consideration that the vehicle's running conditions may worsen due to slippage, and there is room for further improvement in this regard.

[0006] Patent No. 3085092

[0007] The vehicle of the present invention detects the condition around the tire, and controls the vehicle driving force based on the detected condition around the tire.

[0008] According to the present invention, the vehicle driving force can be controlled so that the vehicle does not fall into a driving condition that is worse than normal, such as tire slippage.

[0009] 1 is a diagram showing a schematic diagram of a system configuration of a vehicle to which the present invention is applied; 2 is a diagram showing a schematic diagram of the correlation between running resistance and sinkage amount; 3 is a diagram showing a schematic diagram of the correlation between sinkage amount and slip ratio; 4 is a diagram showing a schematic diagram of the correlation between driving force and slip ratio; 5 is a diagram showing a schematic diagram of the correlation between sinkage amount, slip ratio, and running resistance; 6 is a diagram showing a schematic diagram of the correlation between running resistance and slip ratio; 7 is a diagram showing a schematic diagram of the correlation between running resistance and driving force transmitted to the wheels; 8 is a diagram showing a schematic diagram of a vehicle climbing over a step on a hard road surface; 9 is a timing chart showing a situation in which, when a vehicle starts on a soft road surface, the driving force does not exceed the running resistance and the vehicle cannot start; 10 is a timing chart showing a situation in which, when a vehicle starts on a soft road surface, the driving force exceeds the running resistance and the vehicle is able to start; 11 is a timing chart showing a situation in which, when a road surface property changes while traveling, the required driving force exceeds the vehicle driving force. 1 is a timing chart showing a situation in which the vehicle driving force exceeds the required driving force when the road surface characteristics change during driving. 2 is a flowchart showing an example of a control flow in a vehicle according to an embodiment. 3 is an explanatory diagram showing a control system according to another embodiment of the present invention. 4 is an explanatory diagram showing a correlation between the driving force and the slip ratio according to another embodiment of the present invention.

[0010] An embodiment of the present invention will be described in detail below with reference to the drawings.

[0011] FIG. 1 is an explanatory diagram that schematically shows the system configuration of a vehicle 1 to which the present invention is applied.

[0012] The vehicle 1 is a four-wheel drive vehicle, and the drive wheels are driven by the rotation of a crankshaft of an internal combustion engine (not shown), for example. The drive wheels of the vehicle 1 may also be driven by a motor, for example.

[0013] The vehicle 1 has a camera 3 and a first infrared sensor 4 as condition detection units capable of detecting the condition around the front wheels 2, a second infrared sensor 6 as a condition detection unit capable of detecting the condition around the rear wheels 5, and a control unit 7 to which information from the camera 3, the first infrared sensor 4 and the second infrared sensor 6 is input.

[0014] The camera 3 and the first infrared sensor 4 are disposed, for example, on the left and right front wheels 2, respectively. The second infrared sensor 6 is disposed, for example, on the left and right rear wheels 5, respectively.

[0015] The camera 3 is positioned, for example, diagonally above and rearward of the target front wheel 2 and is capable of capturing images of the road surface conditions around the target front wheel 2 and in the direction of travel of the target front wheel 2 when the vehicle 1 is moving forward. The camera 3 is capable of detecting, for example, the difference in elevation of the road surface around the target front wheel 2, road surface properties, etc. The detection of the difference in elevation refers to the difference in elevation of the road surface in front of the front wheel 2, based on the position of the lower end of the front wheel 2. The detection of the road surface properties refers to whether the road surface is a soft surface such as sand, mud, or deep snow, or a hard surface such as asphalt. Here, in the case of a soft road surface, the difference in elevation of the road surface refers to the amount of subsidence (amount of sinking or burial), which is the difference in elevation between the lower end of the target wheel (e.g., the front wheel 2) and the road surface in the direction of travel of the target wheel (e.g., the front wheel 2). When the road surface is hard, the difference in elevation of the road surface is, for example, a step caused by an obstacle such as a curb existing on the road surface in the direction of travel of the target wheel (for example, the front wheel 2). In other words, the camera 3 detects the surrounding conditions on the side in the direction of travel of the front wheel 2 as the vehicle 1 moves forward.

[0016] The first infrared sensor 4 is located, for example, in front of the target front wheel 2, and has an emitting unit that emits infrared rays and a light receiving unit that receives reflected light of the infrared rays emitted from the emitting unit. The first infrared sensor 4 is capable of detecting, for example, the elevation difference and road surface properties of the road surface around the target front wheel 2. The first infrared sensor 4 detects the surrounding conditions in the direction of travel of the front wheel 2 when the vehicle 1 is moving forward.

[0017] The second infrared sensor 6 is located, for example, behind the target rear wheel 5, and has an emitting unit that emits infrared rays and a light receiving unit that receives reflected light of the infrared rays emitted from the emitting unit. The second infrared sensor 6 is capable of detecting, for example, the difference in elevation of the road surface around the target rear wheel 5, the road surface properties, etc. The difference in elevation of the road surface behind the rear wheel 5 refers to the difference in elevation of the road surface behind the rear wheel 5, with the lower end position of the rear wheel 5 as the reference. The second infrared sensor 6 detects the surrounding conditions in the direction of travel of the rear wheel 5 when the vehicle 1 is moving backward.

[0018] The control unit 7 is a well-known digital computer equipped with a CPU, ROM, RAM, and an input / output interface. For various control and calculation purposes, the control unit 7 receives output signals from the camera 3, the first infrared sensor 4, the second infrared sensor 6, and various other sensors.

[0019] For example, when vehicle 1 travels on a soft sandy road surface or starts off from a soft road surface, as shown in Figure 2, the greater the amount of sinking (sinking) of the tires (wheels), the greater the volume (weight) of sand that the wheels have to push aside and the height (amount of sinking) that the wheels attempt to climb up, resulting in increased running resistance.

[0020] Furthermore, for example, when the vehicle 1 is traveling on a soft sandy road surface or starting off from a soft road surface, if the wheels slip, as shown in Figure 3, the wheels will scrape out sand and the amount of sinking of the wheels will increase.

[0021] Furthermore, on soft road surfaces, the wheels are more likely to slip, and the driving force transmitted to the wheels is limited, as shown in Figure 4. In other words, the greater the slip ratio, the smaller the rate of increase in the driving force transmitted to the wheels, and the driving force transmitted to the wheels approaches a certain value.

[0022] Fig. 5 is a characteristic diagram that combines the characteristic diagrams shown in Fig. 2 and Fig. 3, with the amount of sinkage on the vertical axis. Fig. 6 shows the relationship between running resistance and slip ratio in a direct manner, with reference to Fig. 5. Fig. 6 is a characteristic diagram showing the relationship between running resistance and slip ratio. As shown in Fig. 6, the higher the slip ratio, the higher the running resistance.

[0023] From the relationship shown in Figure 4 and the relationship shown in Figure 6, the relationship between running resistance and driving force transmitted to the wheels can be derived as shown in Figure 7. The characteristic line C1 shown by a thin solid line in Figure 7 represents the running resistance. The characteristic line C2 shown by a thick solid line in Figure 7 represents the driving force transmitted to the wheels.

[0024] As shown in FIG. 7, the driving force transmitted to the wheels increases as the slip ratio increases, while the driving resistance changes in proportion to the slip ratio. However, the rate of increase (slope) decreases as the slip ratio increases.

[0025] Therefore, in an area where the slip ratio is small and the driving force is small, the driving force transmitted to the wheels is less than the running resistance, and there is a risk that the vehicle will not be able to obtain a propulsive force.

[0026] Therefore, in the vehicle 1 of this embodiment, when it is expected that the driving force transmitted to the wheels, which is the wheel driving force, will be lower than the running resistance in relation to the slip ratio (or slip amount), the control unit 7 as a control unit increases and corrects the driving force transmitted to the wheels so that the slip ratio (or slip amount) is such that the driving force transmitted to the wheels exceeds the running resistance.

[0027] 8, when the vehicle 1 of this embodiment goes over a bump caused by an obstacle such as a rock or a curb while traveling on asphalt, which is a hard road surface, the control unit 7 corrects and increases the driving force transmitted to the wheels so that the driving force required to go over the bump is added. The correction amount increases as the bump is higher (larger). In other words, the vehicle driving force of a target wheel (e.g., front wheel 2) is controlled in accordance with the difference in elevation of the road surface ahead, which is the direction of travel of the target wheel.

[0028] FIG. 9 is a timing chart showing a situation in which the vehicle cannot start moving on a soft road surface because the driving force does not exceed the running resistance.

[0029] At time t1 in FIG. 9 , the accelerator pedal depression increases, and driving force (vehicle driving force shown by a solid line in FIG. 9 ) begins to be transmitted to the wheels. However, the driving force transmitted to the wheels is smaller than the required driving force shown by a dashed line in FIG. 9 . The required driving force is greater than the running resistance described above. Therefore, the vehicle remains in a state where it cannot start moving (a zero vehicle speed state) after time t1. Furthermore, after time t1, the wheels of the vehicle begin to slip, and the amount of wheel sinking gradually increases. Therefore, the driving force required for starting (required driving force shown by a dashed line in FIG. 9 ) also gradually increases. Therefore, if this situation continues, the driving force required for starting will increase further due to the increase in the amount of sinking caused by slipping, and in some cases, the vehicle may become stuck.

[0030] FIG. 10 is a timing chart showing a situation in which the driving force exceeds the running resistance and the vehicle is able to start moving on a soft road surface.

[0031] The vehicle has been stopped with its wheels sinking on the soft road surface since before time t1 in FIG. 10, but by taking into account the amount of sinking of the vehicle and transmitting a driving force that exceeds the necessary driving force to the wheels from time t1, the vehicle can start moving at time t1 even though it is slipping.

[0032] In other words, the vehicle 1 of the present embodiment described above controls the vehicle driving force so that it exceeds the required driving force (running resistance) based on the detected road surface condition around the tires, thereby preventing poor running conditions due to tire slippage, etc., even when starting from a soft road surface, as shown in Figure 10. In other words, the vehicle 1 of the present embodiment described above can prevent the vehicle 1 from moving forward (being unable to move) due to a vehicle driving force below the running resistance, causing the tires to sink (sink), and the amount of sinking (sinking) increases, making it impossible for the vehicle to get stuck. In other words, the vehicle 1 of the present embodiment described above can control the vehicle driving force so as to prevent poor running conditions due to tire slippage, etc., by detecting (understanding) the road surface condition around the tires.

[0033] Furthermore, the vehicle 1 of the present embodiment described above controls the vehicle driving force based on the state of the tire's surroundings detected before slippage occurs, and therefore can effectively prevent the vehicle from becoming stuck.

[0034] FIG. 11 is a timing chart showing a situation in which the required driving force exceeds the vehicle driving force when the road surface conditions change during driving.

[0035] At time t1 in Figure 11, the vehicle begins to experience an increase in slippage (or slip ratio) due to changes in road surface conditions, and the driving force transmitted to the wheels becomes smaller than the required driving force indicated by the dashed line in Figure 11 from time t1 onwards. Therefore, the vehicle speed begins to decrease from time t1 in Figure 11. At time t2 in Figure 11, the driver senses deceleration and presses the accelerator, but even after time t2, the increase in vehicle driving force cannot keep up with the increase in required driving force, and deceleration continues.

[0036] In other words, for example, if the running resistance suddenly increases due to a change in road surface characteristics while driving, if the vehicle driving force is not controlled appropriately, the vehicle driving force will fall below the required driving force, resulting in increased slippage and vehicle deceleration, which may in some cases cause the vehicle to stop (stand still) and become stuck.

[0037] FIG. 12 is a timing chart showing a situation in which the vehicle driving force exceeds the required driving force when the road surface conditions change during driving.

[0038] At time t1 in FIG. 12 , the vehicle's slip amount (or slip ratio) begins to increase due to a change in road surface conditions, but the driving force transmitted to the wheels is greater than the required driving force, indicated by the dashed line in FIG. 12 , from time t1 in FIG. 12 onward. That is, the vehicle driving force is controlled to remain greater than the required driving force after time t1 (time t1 in FIG. 12 ), predicting the timing at which the road surface conditions will change. Therefore, in FIG. 12 , the slip amount (or slip ratio) and the amount of sinking are suppressed after time t1, and the vehicle speed does not decrease after time t1. Furthermore, by suppressing the slip amount (or slip ratio) and the amount of sinking, the increase in the required driving force after time t1 in FIG. 12 is suppressed.

[0039] Therefore, the vehicle 1 of the above-described embodiment corrects the driving force transmitted to the wheels in accordance with the road surface conditions ahead of the wheels, which is the direction in which the wheels are traveling.

[0040] In other words, the vehicle 1 of the above-described embodiment controls the vehicle driving force so that it exceeds the required driving force (running resistance) based on the road surface characteristics in front of the tire as the detected condition around the tire, and can continue to drive smoothly without slowing down even if the road surface characteristics change during driving, as shown in Figure 12.

[0041] Furthermore, the vehicle 1 of the above-described embodiment can instantly increase the vehicle driving force based on the conditions around the tires even in cases where the road surface height remains unchanged but the depth (amount of subsidence) changes, which is not visible to the naked eye.

[0042] In short, the vehicle 1 of the above-described embodiment controls the driving force of the vehicle based on the difference in elevation of the road surface around the wheels (tires) and the road surface characteristics so as to obtain the torque required for the front wheels 2 or rear wheels 5 of the vehicle 1 to move forward or backward.

[0043] This allows the vehicle 1 to control the vehicle driving force so as to prevent the vehicle 1 from falling into a poor driving condition such as wheel (tire) slippage.

[0044] Specifically, it becomes possible to predict and avoid poor driving conditions due to tire (wheel) slippage, or poor driving conditions due to insufficient driving force to overcome bumps, in advance.

[0045] FIG. 13 is a flowchart showing an example of the flow of control in the vehicle 1 of the present embodiment described above.

[0046] In step S1, the condition of the area around the tire, i.e., the area around the front wheel 2 of the vehicle 1, is detected. Specifically, for example, when the vehicle 1 is moving forward, the condition of the area around the front wheel 2 is detected as the difference in elevation and surface condition of the road surface ahead of the front wheel 2, which is the area in the direction of travel of the front wheel 2.

[0047] In step S2, the vehicle driving force based on the road surface conditions around the front wheels 2 is calculated.

[0048] In step S3, the driving force is distributed to the front wheels 2 and the rear wheels 5 so that the vehicle driving force calculated in step S2 is obtained by the front wheels 2.

[0049] Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention.

[0050] For example, the vehicle 1 can be applied to an all-wheel drive vehicle (AWD vehicle) or a situation where the driving force and braking force are automatically controlled. In this case, the vehicle 1 is controlled according to the flow shown in Fig. 14. Fig. 14 is an explanatory diagram that schematically shows a control system in another embodiment of the present invention.

[0051] Step S21 corresponds to the state detection units of the camera 3, the first infrared sensor 4, the second infrared sensor 6, and the like.

[0052] In step S22, the elevation difference, road surface properties, etc. of the road surface around the target wheel are detected.

[0053] In step S23, the vehicle driving force (required torque) is calculated based on the detected road surface conditions around the target wheel.

[0054] Step S24 corresponds to the control unit 7.

[0055] Step S25 is an AWD controller that controls the distribution of driving force to each wheel when the vehicle 1 is an all-wheel drive vehicle. If the vehicle 1 is an all-wheel drive vehicle, step S25 distributes driving force to each wheel so that the vehicle driving force (required torque) calculated in step S23 is obtained at the target wheel.

[0056] The vehicle 1, which is an all-wheel drive vehicle, can prevent the vehicle driving force from falling below the running resistance by changing the distribution of driving force to all wheels.

[0057] Furthermore, since the vehicle driving force is controlled based on the state of the tire's surroundings detected by the sensor before slippage occurs, it is possible to effectively prevent the vehicle from becoming stuck.

[0058] Furthermore, if a bump with low road resistance is detected, the system can, for example, change (review) the drive force distribution to all wheels, making it easier to ensure the total drive force required to climb over the bump.

[0059] Step S26 is performed when the vehicle has a function for automatically controlling the driving force and braking force. In step S26, the driving force and braking force are automatically controlled so that the vehicle driving force (required torque) calculated in step S23 is obtained at the target wheel.

[0060] Even in a driving mode in which drive torque and braking are automatically controlled, a vehicle driving force that exceeds the running resistance may be generated in a feedforward manner based on the state of the tire's surroundings. In the above driving mode, the amount of slip (or slip ratio) can be optimized by the braking force (brake operation) in that driving mode.

[0061] For example, the camera 3, the first infrared sensor 4, and the second infrared sensor 6 may be disposed on only one side of the front wheel 2 or the rear wheel 5, either to the left or right.

[0062] For example, the vehicle 1 may include at least one of the camera 3 , the first infrared sensor 4 and the second infrared sensor 6 .

[0063] For example, the vehicle 1 may be equipped with a camera that can detect the surrounding conditions on the side in the direction of travel of the wheels (front wheels 2 or rear wheels 5) when the vehicle 1 is moving backward.

[0064] For example, the vehicle 1 may use a lidar, sonar, millimeter-wave radar, or the like as a condition detection unit capable of detecting the condition around the front wheels 2 or the rear wheels 5. The condition detection unit of the vehicle 1 may also be a camera or sensor used in a parking assistance system, or the like.

[0065] For example, if the driving force transmitted to the wheels of the vehicle 1 is low relative to the running resistance, the driving force transmitted to the wheels may be increased by changing the driving force distribution ratio between the front wheels 2 and the rear wheels 5, as shown in FIG. 15. By changing the driving force distribution ratio between the front and rear wheels, the driving force transmitted to the target wheels can be increased as shown in FIG. 15. In FIG. 15, the characteristic line C1 shown by the thin solid line represents the running resistance. In FIG. 15, the characteristic lines C2a and C2b shown by the thick dashed lines and the characteristic line C2c shown by the thick solid line represent the driving force transmitted to the wheels. As shown in FIG. 15, by changing the driving force distribution ratio between the front and rear wheels, the driving force transmitted to the target wheels can be changed from that represented by the characteristic line C2a to that represented by the characteristic line C2b and the characteristic line C2c.

[0066] The above-described embodiment relates to a control method for the vehicle 1 and a control device for the vehicle 1 .

Claims

1. A vehicle control method for detecting a condition around a tire of a vehicle and controlling a vehicle driving force based on the detected condition around the tire.

2. A vehicle control method as set forth in claim 1, wherein the condition around the tire is detected as a difference in elevation ahead of the tire in the vehicle's traveling direction, and the vehicle driving force is controlled in accordance with the difference in elevation.

3. A vehicle control method according to claim 1, wherein the road surface conditions ahead of the tire are detected as the conditions around the tire, and the vehicle driving force is controlled in accordance with the road surface conditions ahead of the tire.

4. A vehicle control method as described in claim 3, wherein, when the road surface condition ahead of the tire is detected as a soft road surface, if the slip rate or slip amount of the tire is such that the vehicle driving force is lower than the running resistance, the vehicle driving force is corrected to a slip rate or slip amount such that the vehicle driving force exceeds the running resistance.

5. A vehicle control method as set forth in claim 4, wherein the running resistance increases in proportion to the tire slip ratio or slip amount, and the rate of increase of the vehicle driving force in response to an increase in the tire slip ratio or slip amount decreases as the tire slip ratio or slip amount increases.

6. A vehicle control method as described in claim 3, wherein, when the road surface condition ahead of the tire is detected as a hard road surface, the vehicle driving force is increased so that the tire can climb over the elevation difference ahead of the tire.

7. The vehicle control method according to claim 1, wherein the vehicle is an all-wheel drive vehicle, and the control of the vehicle driving force comprises changing the distribution of driving force of the all-wheel drive vehicle.

8. A vehicle control method as described in claim 7, wherein when the vehicle driving force that exceeds the running resistance cannot be generated by the tire alone, the driving force is allocated to tires other than the tire so that the vehicle driving force exceeds the running resistance for the entire vehicle.

9. A vehicle control method as described in claim 1, which has a driving mode that automatically controls driving torque and braking, and while driving in said driving mode, generates said vehicle driving force that exceeds the running resistance in a feedforward manner based on the detected conditions around said tires.

10. A vehicle control device having a condition detection unit that detects the condition around a tire of a vehicle, and a control unit that controls the vehicle driving force based on the condition around the tire detected by the condition detection unit.

Images