Vehicular control device

Abstract

To provide a vehicular control device that can properly prevent a driving wheel from slipping.SOLUTION: An estimated value of a current road surface friction coefficient at a place where a slip has occurred is calculated on the basis of a place, an estimated value of a road surface friction coefficient, weather information, at the time when the slip has occurred, and current weather information at the place where the slip has occurred. Moreover, an estimated value of lower-limit force in the driving wheel, at which the slip may occur at the place where the slip has occurred, is calculated on the basis of the estimated value of the current road surface friction coefficient and a current wheel load. This enables force in the driving wheel where the slip is highly likely to be estimated accurately. Further, the force in the driving wheel that is outputted in accordance with operation by a driver is controlled so that the force becomes smaller than the estimated value of the lower-limit force, at the place where the slip has occurred. This enables operation support control of reducing occurrence of slips to be properly performed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device that reduces the occurrence of slippage of drive wheels. [Background technology]

[0002] Vehicle control devices that perform driving assistance control to reduce the occurrence of slippage of drive wheels are well known. For example, the control device described in Patent Document 1 discloses a control device that calculates the necessary driving force required for starting based on the vehicle weight and road surface gradient, calculates a limit driving force based on the vehicle weight and road surface friction coefficient, and activates a start assist device when the limit driving force falls below the necessary driving force. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-151817 Summary of the Invention [Problem to be solved by the invention]

[0004] However, depending on the number, position, and movement of passengers, the load on one of the drive wheels may be reduced, making it easier for the vehicle to slip. The technology in Patent Document 1 does not detect the wheel load on each drive wheel. Therefore, it is not possible to predict the occurrence of slip on a drive wheel with a reduced wheel load based on the vehicle weight alone, and there is a risk that driving assistance control to reduce the occurrence of slip on the drive wheels may not be performed appropriately.

[0005] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a vehicle control device that can appropriately reduce the occurrence of slippage of the drive wheels. [Means for solving the problem]

[0006] The gist of a first invention is that the vehicle control device includes: (a) a vehicle control device that performs driving assistance control to reduce the occurrence of slippage of drive wheels, (b) an acquisition unit that acquires the wheel load of each of the drive wheels, the wheel speed of each of the drive wheels, vehicle position information, a location where the slippage occurred, an estimated road friction coefficient at the location where the slippage occurred, and weather information for the area in which the vehicle is traveling; (c) a calculation unit that calculates an estimate of the current road friction coefficient at the location where the slippage occurred based on the location, the estimated road friction coefficient, and the weather information at the time the slippage occurred, and the current weather information for the location where the slippage occurred, and calculates an estimate of a lower limit force at the drive wheels at which the slippage will occur at the location where the slippage occurred based on the current estimated road friction coefficient and the current wheel load; and (d) an output control unit that controls the force at the drive wheels to be output in response to driver operation so that the force at the location where the slippage occurred is smaller than the estimated lower limit force. [Effects of the Invention]

[0007] According to the first aspect of the present invention, an estimate of the current road friction coefficient at the location where the slip occurred is calculated based on the location, estimated road friction coefficient, and weather information at the time of the slip, as well as current weather information for the location where the slip occurred. Additionally, an estimate of the lower limit force at the drive wheels at which slip will occur at the location where the slip occurred is calculated based on the current estimated road friction coefficient and the current wheel load. This allows for accurate estimation of the force at the drive wheels at which slip is likely to occur. Furthermore, the force at the drive wheels output in response to the driver's operation is controlled so that it is smaller than the estimated lower limit force at the location where the slip occurred. This limits the force at the drive wheels to the force at which slip is likely to occur, with the upper limit set to the force at the drive wheels at which slip is likely to occur, thereby appropriately performing driving assistance control to reduce the occurrence of slip. Therefore, the occurrence of drive wheel slip can be appropriately reduced. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle to which the present invention is applied; [Figure 2] 10A and 10B are diagrams illustrating an example of an embodiment in which driving force and braking force are controlled based on the current wheel load. [Figure 3] 4 is a flowchart illustrating the main control operations of a vehicle control device (electronic control device, data center). DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0010] Fig. 1 is a diagram illustrating the schematic configuration of a vehicle 10 to which the present invention is applied. In Fig. 1, the vehicle 10 is, for example, a route bus or an autonomous vehicle that travels along a predetermined route, and includes a first vehicle 10a, a second vehicle 10b, a third vehicle 10c, etc. The vehicle 10 is equipped with a power source 12, left and right front wheels 14, and left and right rear wheels 16. Note that the "left and right" mentioned above refer to the left and right with respect to the forward direction of the vehicle 10.

[0011] The vehicle 10 is an all-wheel drive vehicle (also known as a four-wheel drive vehicle) in which torque is distributed to each of the front wheels 14 and the rear wheels 16. The front wheels 14 and the rear wheels 16 are each a driving wheel DW of the vehicle 10.

[0012] The power source 12 is, for example, an engine and / or an electric motor. The power of the power source 12 is controlled by an electronic control device 70, which will be described later. In the vehicle 10, the power of the power source 12 is transmitted as driving force Fd to front wheels 14 via a power transmission device including a front axle 18, and is also transmitted as driving force Fd to rear wheels 16 via a power transmission device including a rear axle 20.

[0013] The vehicle 10 further includes a wheel brake control device 30. The wheel brake control device 30 includes a known brake pedal (not shown), a brake master cylinder (not shown), a brake actuator 32, a brake oil passage 34, and a brake device 36. The brake device 36 is provided on each of the drive wheels DW, and includes a known brake wheel cylinder 38.

[0014] The brake actuator 32 supplies a brake hydraulic pressure Pbra to the brake wheel cylinder 38 in accordance with a command from the electronic control device 70. When the brake hydraulic pressure Pbra is supplied to the brake wheel cylinder 38, the braking device 36 applies a braking force Fb to the drive wheels DW.

[0015] Under normal circumstances, the brake actuator 32 supplies master cylinder hydraulic pressure generated from a brake master cylinder in response to a brake operation by the driver as brake hydraulic pressure Pbra to the brake wheel cylinders 38. The master cylinder hydraulic pressure is a hydraulic pressure corresponding to a brake operation amount Bra, which indicates the degree of depression of the brake pedal by the driver, i.e., the degree of braking operation.

[0016] Furthermore, regardless of the brake operation by the driver, the brake actuator 32 supplies the brake hydraulic pressure Pbra to the brake wheel cylinder 38 as needed. The brake actuator 32 also supplies the brake hydraulic pressure Pbra to the brake wheel cylinder 38, which is smaller than the brake hydraulic pressure Pbra corresponding to the brake operation by the driver, in order to prevent slippage of the drive wheels DW.

[0017] The vehicle 10 further includes a communication device 40. The communication device 40 exchanges various types of information with the electronic control device 70 via, for example, a cable. The communication device 40 also exchanges various types of information by communicating with a data center 50 via a known network 100 outside the vehicle 10. The communication device 40 is connected to the network 100 via, for example, wireless communication R with a wireless device 110 outside the vehicle 10. The wireless device 110 is a transmitting / receiving device connected to the network 100 and transmitting / receiving various signals via wireless communication R.

[0018] The data center 50 is an external control device that exists separately from the vehicle 10, and is a computer (here, a server is also synonymous) equipped with a CPU and the like that is connected to the network 100. The data center 50 is connected to each of the vehicles 10 via wireless communication. The data center 50 is a device that receives, processes, analyzes, stores, and provides various types of information.

[0019] The vehicle 10 further includes an electronic control device 70 as a controller including control devices of the vehicle 10 related to the control of the power source 12 and the brake device 36. The electronic control device 70 includes a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input / output interface, etc.

[0020] The electronic control unit 70 is supplied with various signals based on detection values ​​from various sensors provided on the vehicle 10. The various sensors include, for example, a six-axle force load meter 60, a wheel speed sensor 62, an accelerator opening sensor 64, a brake sensor 66, and a vehicle position sensor 68. The various signals include, for example, a wheel load Fw, a wheel speed Nw, an accelerator opening θacc, a brake-on signal Bon, a brake operation amount Bra, and position information Ivp. The six-axle force load meter 60 supplies measurement signals such as the wheel load Fw to the electronic control unit 70 via a wired connection, but it is also possible to supply measurement signals such as the wheel load Fw to the electronic control unit 70 wirelessly by using, for example, a telemeter.

[0021] The six-axle force load meter 60 includes a left front wheel load meter 60fl, a right front wheel load meter 60fr, a left rear wheel load meter 60rl, and a right rear wheel load meter 60rr. The wheel load Fw is the wheel load on each of the drive wheels DW and includes a left front wheel load Fwfl of the left front wheel 14, a right front wheel load Fwfr of the right front wheel 14, a left rear wheel load Fwrl of the left rear wheel 16, and a right rear wheel load Fwrr of the right rear wheel 16. The wheel speed sensor 62 includes a left front wheel speed sensor 62fl, a right front wheel speed sensor 62fr, a left rear wheel speed sensor 62rl, and a right rear wheel speed sensor 62rr. The wheel speed Nw is the rotational speed of each of the drive wheels DW and includes a left front wheel speed Nwfl of the left front wheel 14, a right front wheel speed Nwfr of the right front wheel 14, a left rear wheel speed Nwrl of the left rear wheel 16, and a right rear wheel speed Nwrr of the right rear wheel 16. The accelerator opening θacc is the magnitude of accelerator pedal depression, i.e., the magnitude of accelerator operation by the driver, and is the accelerator operation amount that indicates the magnitude of the driver's acceleration operation. The brake-on signal Bon is a signal that indicates the state in which the brake pedal is being operated by the driver. The vehicle position sensor 68 includes a GPS (Global Positioning System) antenna and the like. The position information Ivp includes host vehicle position information that indicates the current position of the vehicle 10 on the earth's surface or a map based on GPS signals (orbital signals) transmitted by GPS satellites and the like.

[0022] The electronic control device 70 outputs various command signals to each device provided in the vehicle 10. The devices are, for example, the power source 12, the brake actuator 32, etc. The various command signals are, for example, a power source control command signal Spu, a brake control command signal Sbra, etc. The power source control command signal Spu is a command signal for controlling the power source 12, i.e., the driving force Fd. The brake control command signal Sbra is a command signal for controlling the brake hydraulic pressure Pbra, i.e., the braking force Fb.

[0023] The data center 50 is supplied with weather information Iwth of the area in which the vehicle 10 is traveling from, for example, a weather information center 120, which is an external organization, via the network 100.

[0024] Here, since a vehicle 10 such as a route bus or an autonomous vehicle has a fixed driving route, it is possible to identify locations where slippage of the drive wheels DW is likely to occur depending on road conditions based on past driving history. However, the wheel load Fw of the vehicle 10 changes depending on the number, positions, and movements of passengers, and this changes the driving force Fd or braking force Fb at which slippage occurs in the vehicle 10.

[0025] Therefore, the electronic control device 70 and the data center 50 function as a vehicle control device that performs driving assistance control to reduce the occurrence of slippage of the drive wheels DW. In this driving assistance control, the force at the drive wheels DW output in response to the driver's operation, that is, the driving force Fd and the braking force Fb, are controlled to prevent slippage, for example, by reflecting the wheel load Fw in the running control (which is also synonymous with drive control) and brake control.

[0026] In order to realize driving assistance control, the electronic control unit 70 includes an in-vehicle acquisition unit 72 and an output control unit 74. In order to realize driving assistance control, the data center 50 includes a center acquisition unit 52 and a storage device 54.

[0027] The in-vehicle acquisition unit 72 acquires the wheel load Fw, the wheel speed Nw, the position information Ivp of the vehicle 10, etc. Based on whether any of the wheel speeds Nw has suddenly increased when the vehicle 10 is driven, the in-vehicle acquisition unit 72 determines whether any of the drive wheels DW has slipped, causing a sudden rotation of the drive wheels DW. Alternatively, based on whether any of the wheel speeds Nw has suddenly decreased when the vehicle 10 is braking, the in-vehicle acquisition unit 72 determines whether any of the drive wheels DW has locked, causing a slip between the drive wheels DW and the road surface.

[0028] When it is determined that a slip has occurred, the on-board acquisition unit 72 acquires the location and date and time when the slip occurred, as well as the wheel load Fw, driving force Fd, or braking force Fb when the slip occurred, and transmits this data to the data center 50. The center acquisition unit 52 acquires the data transmitted from each vehicle 10 and stores it in the storage device 54. The driving force Fd is an estimated value based on the power source control command signal Spu, or a value detected by the axle six-component force load meter 60, etc. The braking force Fb is an estimated value based on the brake control command signal Sbra, or a value detected by the axle six-component force load meter 60, etc.

[0029] The data on slippage stored in the storage device 54 is shared by each vehicle 10. The center acquisition unit 52 acquires the data on slippage stored in the storage device 54 from the data center 50. The output control unit 74 controls the driving force Fd or the braking force Fb using the data on slippage and the current wheel load Fw. This makes it possible to prevent vehicles 10 other than the vehicle 10 on which the slippage occurred from slipping again in the same location.

[0030] FIG. 2 is a diagram illustrating an example of controlling the driving force Fd and the braking force Fb based on the current wheel load Fw. FIG. 2(a) illustrates an example of controlling the driving force Fd, and FIG. 2(b) illustrates an example of controlling the braking force Fb. In FIG. 2(a), the driving force Fd at which slippage is likely to occur is estimated based on the wheel load Fw and driving force Fd at the time of slippage and the current wheel load Fw at a location where slippage occurred during previous deceleration (or braking). A power source control command signal Spu is output to control the power source 12, limiting the driving force Fd so that it is less than the estimated driving force Fd, thereby preventing or suppressing slippage at this location during starting. In FIG. 2(b), the braking force Fb at which slippage is likely to occur is estimated based on the wheel load Fw and braking force Fb at the time of slippage and the current wheel load Fw at a location where slippage occurred during previous deceleration (or braking). By outputting a brake control command signal Sbra that controls the brake actuator 32 and limiting the braking force Fb so that it is less than the estimated braking force Fb, the occurrence of slippage during deceleration at this location is prevented or suppressed.

[0031] The driving force Fd and braking force Fb at which slip is likely to occur are forces at the driving wheels DW at which slip is likely to occur, and are the lower limit forces at the driving wheels DW at which slip occurs (driving force Fd, braking force Fb). The lower limit forces at the driving wheels DW at which slip occurs are the lower limit values ​​of the range of forces at the driving wheels DW at which slip occurs. The lower limit forces at the driving wheels DW at which slip occurs are called the slip occurrence lower limit forces Fslp (slip occurrence driving force Fdlim, slip occurrence braking force Fblim).

[0032] Even when traveling in the same location, the friction coefficient of the road, i.e., the road surface friction coefficient μ, varies depending on the weather (sunny, rainy, snowy, etc.) in the area where the vehicle is traveling. As a result, even with the same wheel load Fw, the slip occurrence lower limit force Fslp (= μ × Fw) varies depending on the weather. For example, on an asphalt road, μ is approximately 0.8 when it is sunny, μ is approximately 0.5 when it is raining, and μ is approximately 0.3 when it is snowing. Also, on a gravel road when it is sunny, μ is approximately 0.5. Even with the same wheel load Fw, for example, on a sunny day, the upper limit of the driving force Fd, which is limited by the slip occurrence driving force Fdlim, is higher than on a snowy day. In this embodiment, driving assistance control is performed taking into account the road surface friction coefficient μ, which varies depending on the weather.

[0033] In order to realize the driving assistance control, the electronic control unit 70 further includes an on-board computing unit 76 , and the data center 50 further includes a center computing unit 56 .

[0034] 3 is a flowchart illustrating the main control operations of the vehicle control device (electronic control device 70, data center 50), and is a flowchart illustrating the control operations for appropriately reducing the occurrence of slippage of the drive wheels DW, which are executed repeatedly, for example. FIG. 3(a) is a flowchart for transmitting information about the occurrence of slippage of the drive wheels DW from the electronic control device 70 to the data center 50. FIG. 3(b) is a flowchart for controlling the driving force Fd or braking force Fb based on information about past occurrences of slippage of the drive wheels DW.

[0035] 3A, first, in step S10 (hereinafter, "step" will be omitted) corresponding to the function of the on-vehicle acquisition unit 72, it is determined whether or not slippage of the drive wheels DW has occurred. If the determination in S10 is negative, the routine is terminated. If the determination in S10 is positive, in S20 corresponding to the function of the on-vehicle acquisition unit 72, the location and date and time when the slippage occurred, the wheel load Fw, driving force Fd or braking force Fb when the slippage occurred, an estimated value of the road friction coefficient μ at the location where the slippage occurred, etc. are acquired, and these data are transmitted to the data center 50. The on-vehicle acquisition unit 72 calculates an estimated value of the road friction coefficient μ based on the wheel load Fw and driving force Fd or braking force Fb when the slippage occurred, for example, to acquire the estimated value of the road friction coefficient μ. Alternatively, the on-board acquisition unit 72 may acquire an estimated value of a predetermined road surface friction coefficient μ based on image information of the road at the location where the slip occurred, for example, taken by a camera (not shown) that captures an image in front of the vehicle 10.

[0036] Next, in S30, which corresponds to the function of the center acquisition unit 52, data transmitted from each of the vehicles 10 (10a, 10b, 10c, etc.) is acquired and stored in the storage device 54. In addition, weather information Iwth for the location where the slip occurred, i.e., the area where the vehicle 10 is traveling, transmitted from the weather information center 120, is acquired and stored in the storage device 54. The road surface friction coefficient μ varies depending on the location where the slip occurred and the weather. Therefore, in S30, the location where the slip occurred, the estimated value of the road surface friction coefficient μ when the slip occurred, and the weather at the location where the slip occurred are linked together and stored in the storage device 54. The on-board acquisition unit 72 and the center acquisition unit 52 function as acquisition units in the vehicle control device.

[0037] 3(b), first, in S110, which corresponds to the function of the central calculation unit 56, current weather information Iwth for the location where a slip occurred in the past, transmitted from the weather information center 120, is acquired. Then, an estimate of the current road friction coefficient μ for the location where a slip occurred in the past is calculated based on the location, the estimated value of the road friction coefficient μ, and the weather information Iwth when a slip occurred in the past, and the current weather information Iwth for the location where a slip occurred in the past. For example, the estimate of the road friction coefficient μ for the location where a slip occurred in the past is corrected by the amount of the difference between the road friction coefficient μ due to the difference between the past weather and the current weather. In S110, past slip information such as the location when a slip occurred in the past, the wheel load Fw, the driving force Fd, or the braking force Fb, and the estimate of the current road friction coefficient μ for the location where a slip occurred in the past are transmitted to the electronic control unit 70.

[0038] Next, in S120, which corresponds to the function of the on-board calculation unit 76, an estimate of the slip occurrence lower limit force Fslp (=μ×Fw) at the location where slip occurred in the past is calculated based on the current wheel load Fw and an estimate of the current road friction coefficient μ at the location where slip occurred in the past. The estimate of the current road friction coefficient μ is a value calculated based on past slip information and an estimate of the road friction coefficient μ when slip occurred in the past. The center calculation unit 56 and the on-board calculation unit 76 function as calculation units in the vehicle control device.

[0039] Next, in S130, which corresponds to the function of the output control unit 74, the driving force Fd or braking force Fb to be output is calculated based on the pedal opening degree (accelerator opening degree θacc, brake operation amount Bra) operated by the driver and the detected values ​​(driving force Fd, braking force Fb) by the axle 6-component force load meter 60.

[0040] Next, in S140, which corresponds to the function of the output control unit 74, if the driving force Fd or braking force Fb calculated in S130 above is greater than the estimated value of the slip occurrence lower limit force Fslp calculated in S120 above, the power source 12 and the brake actuator 32 are controlled so that the driving force Fd or braking force Fb becomes smaller than the estimated value of the slip occurrence lower limit force Fslp. In this way, the output control unit 74 controls the driving force Fd or braking force Fb so that they become smaller than the estimated value of the slip occurrence lower limit force Fslp at the location where slip has occurred.

[0041] As described above, according to this embodiment, the slip occurrence lower limit force Fslp is estimated with high accuracy. Furthermore, by limiting the driving force Fd and the braking force Fb with the slip occurrence lower limit force Fslp as the upper limit, driving assist control that reduces the occurrence of slip is appropriately performed. Therefore, the occurrence of slip of the drive wheels DW can be appropriately reduced.

[0042] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0043] For example, in the above-described embodiment, data from each of the vehicles 10 (10a, 10b, 10c, etc.) is collected and processed in the data center 50, but this is not limited to this. For example, the vehicle 10 may process the data independently to perform driving assistance control. In this case, a vehicle control device that performs driving assistance control is configured using only the electronic control unit 70. The present invention can also be applied in this manner.

[0044] In the above-described embodiment, the vehicle 10 is an all-wheel drive vehicle, and a route bus, an autonomous vehicle, or the like is exemplified as the vehicle 10, but the present invention is not limited to this. For example, the vehicle 10 may be a two-wheel drive vehicle, or may be a passenger car other than a commercial vehicle.

[0045] It should be noted that the above is merely one embodiment, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0046] 10: Vehicle 14: Left and right front wheels (drive wheels) 16: Left and right rear wheels (drive wheels) 50: Data center (vehicle control device) 52: Center acquisition unit (acquisition unit) 56: Center calculation unit (calculation unit) 70: Electronic control device (vehicle control device) 72: On-vehicle acquisition unit (acquisition unit) 74: Output control unit 76: On-vehicle calculation unit (calculation unit) DW: Drive wheels

Claims

[Claim 1] A vehicle control device that performs driving assistance control to reduce the occurrence of slippage of drive wheels, an acquisition unit that acquires the wheel load of each of the drive wheels, the wheel speed of each of the drive wheels, vehicle position information, the location where the slip occurred, an estimated value of the road surface friction coefficient at the location where the slip occurred, and weather information for the area where the vehicle is traveling; a calculation unit that calculates an estimate of a current road friction coefficient at the location where the slip occurred based on the location, the estimated road friction coefficient, and the weather information at the time the slip occurred, and the current weather information at the location where the slip occurred, and calculates an estimate of a lower limit force at the drive wheel at which the slip will occur at the location where the slip occurred based on the estimated current road friction coefficient and the current wheel load; an output control unit that controls the force output to the drive wheels in response to an operation by a driver so that the force is smaller than the estimated lower limit force at the location where the slip has occurred; A vehicle control device comprising:

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