Control apparatus and control method

Abstract

To optimize the behavior of a vehicle.SOLUTION: A control apparatus 15 is a control apparatus that controls a behavior of a vehicle 1, and includes a control unit that executes, when slip of a wheel 2 occurs due to a driving force, a first control of suppressing the slip and a second control of generating a larger braking force, as compared to the first control, at the wheel 2 at which the slip is occurring. The control unit automatically executes the second control in response to behavior of the vehicle 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In order to stabilize the behavior of a vehicle, techniques have been proposed for suppressing wheel slip when wheel slip occurs due to driving force. For example, as disclosed in Patent Document 1, one such technique is a control that reduces the driving force of the vehicle when wheel slip occurs due to driving force. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-049825 Summary of the Invention [Problem to be solved by the invention]

[0004] There are a variety of situations in which wheel slippage due to driving force can occur, and it is desirable to optimize the vehicle behavior in response to the situation.

[0005] In view of the above, an object of the present invention is to provide a control device and a control method that can optimize the behavior of a vehicle. [Means for solving the problem]

[0006] In order to solve the above problem, the control device is a control device that controls the operation of the vehicle and is equipped with a control unit that executes a first control that suppresses slippage when wheel slippage occurs due to driving force, and a second control that generates a braking force greater than that of the first control on the wheel in which slippage occurs when slippage occurs, and the control unit automatically executes the second control according to the behavior of the vehicle.

[0007] In order to solve the above problem, the control method is a control method for controlling the operation of a vehicle, in which a control unit of a control device executes a first control that suppresses slip when wheel slip occurs due to driving force, and a second control that generates a braking force greater than that of the first control on the wheel in which slip occurs when slip occurs, and the control unit automatically executes the second control according to the behavior of the vehicle. [Effects of the Invention]

[0008] According to the present invention, it is possible to optimize the behavior of a vehicle. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing a general configuration of a vehicle according to an embodiment of the present invention; [Figure 2] 1 is a schematic diagram showing a general configuration of a brake system according to an embodiment of the present invention; [Figure 3] FIG. 2 is a block diagram showing an example of a functional configuration of a control device according to an embodiment of the present invention. [Figure 4] 1 is a diagram showing a state in which a vehicle according to an embodiment of the present invention is traveling on a low μ road; [Figure 5] FIG. 1 is a diagram illustrating a state in which a vehicle according to an embodiment of the present invention is traveling off-road. [Figure 6] 3 is a diagram showing an example of changes in the driving force and braking force of a vehicle in each traction control performed by a control device according to an embodiment of the present invention. FIG. [Figure 7] 3 is a diagram for explaining the transition of processing modes of traction control performed by a control device according to an embodiment of the present invention; FIG. [Figure 8] 10 is a flowchart showing an example of a flow of processing performed by a control device in a permission mode according to an embodiment of the present invention. [Figure 9] 1 is a diagram showing a state in which only the left wheel of a vehicle according to an embodiment of the present invention is located on a low μ road; [Figure 10] FIG. 3 is a diagram showing an example of a transition of acceleration of a wheel of a vehicle according to an embodiment of the present invention. [Figure 11] FIG. 3 is a diagram showing an example of changes in driving force and speed of a vehicle according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Dimensions, materials, and other specific values ​​shown in the embodiments are merely examples for facilitating understanding of the invention and, unless otherwise specified, do not limit the present invention. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

[0011] <Vehicle configuration> The configuration of a vehicle 1 according to an embodiment of the present invention will be described with reference to FIGS.

[0012] Fig. 1 is a schematic diagram showing the general configuration of a vehicle 1. As shown in Fig. 1, the vehicle 1 includes a plurality of wheels 2, a drive source 11, a hydraulic control unit 12, a plurality of wheel speed sensors 13, an inertial measurement unit (IMU) 14, and a control device 15. The vehicle 1 has four wheels 2: a left front wheel 2a, a right front wheel 2b, a left rear wheel 2c, and a right rear wheel 2d. However, the number of wheels 2 may be other than four.

[0013] The drive source 11 outputs a drive force that is transmitted to the wheels 2. An example of the drive source 11 is an engine. Note that instead of or in addition to the engine, an electric motor may be provided in the vehicle 1 as the drive source 11.

[0014] The hydraulic pressure control unit 12 controls the braking force of the vehicle 1. The hydraulic pressure control unit 12 controls the wheel cylinder pressure, which is the hydraulic pressure of the brake fluid in the wheel cylinder, thereby controlling the braking force applied to the wheels 2. Details of the hydraulic pressure control unit 12 will be described later.

[0015] The wheel speed sensor 13 is provided on each wheel 2 and detects the wheel speed of each wheel 2 .

[0016] The inertial measurement unit 14 includes a three-axis gyro sensor and a three-directional acceleration sensor, and detects the angular velocity and acceleration of the vehicle 1. The detection results of the inertial measurement unit 14 are used, for example, to estimate the attitude of the vehicle 1. Note that the inertial measurement unit 14 may include only a portion of the three-axis gyro sensor and the three-directional acceleration sensor.

[0017] The control device 15 controls the operation of the vehicle 1. The control device 15 includes a CPU (Central Processing Unit) which is an arithmetic processing device, a ROM (Read Only Memory) which is a storage element that stores programs used by the CPU, calculation parameters, etc., and a RAM (Random Access Memory) which is a storage element that temporarily stores parameters, etc. that change as appropriate during execution of the CPU. Details of the control device 15 will be described later.

[0018] 2 is a schematic diagram showing the general configuration of a brake system 20 of the vehicle 1. The brake system 20 is mounted on the vehicle 1 and is a system for controlling the braking force generated in the vehicle 1. As shown in FIG. 2, the brake system 20 includes a hydraulic control unit 12, a brake pedal 21, a brake booster 22, a master cylinder 23, a reservoir 24, and wheel cylinders 25.

[0019] The brake system 20 controls the braking force acting on each wheel 2 by controlling the hydraulic pressure (i.e., wheel cylinder pressure) of the wheel cylinder 25 provided on each wheel 2. In order to facilitate understanding, FIG. 2 shows only the parts related to two wheels 2 (e.g., the left front wheel 2a and the right rear wheel 2d) out of the total four wheels 2, and omits the parts related to the other two wheels 2 (e.g., the right front wheel 2b and the left rear wheel 2c).

[0020] The brake pedal 21 is used by the driver to apply the brakes. When applying the brakes, the driver depresses the brake pedal 21. The booster 22 is connected to the brake pedal 21 and works in conjunction with the brake pedal 21 to amplify the force applied to the brake pedal 21. Specifically, the booster 22 incorporates a piston that reciprocates in conjunction with the brake pedal 21 and is connected to a master cylinder 23. As the piston moves in response to the brake application, the master cylinder pressure, which is the hydraulic pressure in the master cylinder 23, is increased. In this way, the booster 22 can generate master cylinder pressure in accordance with the amount of brake application. The reservoir 24 is attached to the master cylinder 23 and stores brake fluid.

[0021] The hydraulic pressure control unit 12 includes a base 12a in which a flow path for brake fluid is formed. The master cylinder 23 and each wheel cylinder 25 are connected to the base 12a of the hydraulic pressure control unit 12. When the wheel cylinder pressure, which is the hydraulic pressure in the wheel cylinder 25, increases, the brake pads (not shown) operate to press against the brake discs (not shown), thereby applying a braking force corresponding to the wheel cylinder pressure to the wheels 2.

[0022] The base body 12a of the hydraulic control unit 12 is formed with brake fluid flow paths, including a main flow path 31, a sub-flow path 32, and a supply flow path 33. The main flow path 31 distributes the brake fluid in the master cylinder 23 to the wheel cylinders 25. The sub-flow path 32 releases the brake fluid in the wheel cylinders 25. The supply flow path 33 supplies the brake fluid in the master cylinder 23 to the sub-flow path 32.

[0023] In addition, the base 12a of the hydraulic control unit 12 is provided with components for controlling the braking force generated on each wheel 2, including an inlet valve (EV) 41, a release valve (AV) 42, a first valve (USV) 43, a second valve (HSV) 44, an accumulator 45, a pump 46 and a motor 47.

[0024] The main flow path 31 connects the master cylinder 23 and the wheel cylinders 25. The main flow path 31 includes one first main flow path 31a and two second main flow paths 31b. The first main flow path 31a is connected to the master cylinder 23. The two second main flow paths 31b branch off from the first main flow path 31a and are connected to the wheel cylinders 25, respectively. A first valve 43 is provided in the first main flow path 31a. An inlet valve 41 is provided in the second main flow path 31b.

[0025] The sub-path 32 communicates the wheel cylinder 25 side of the main path 31 relative to the inlet valve 41 with the master cylinder 23 side of the main path 31 relative to the inlet valve 41 and the wheel cylinder 25 side of the first valve 43. The sub-path 32 includes two first sub-paths 32a and one second sub-path 32b. Each first sub-path 32a is connected to the wheel cylinder 25 side of the main path 31 relative to the inlet valve 41. The second sub-path 32b connects the junction of the two first sub-paths 32a with the master cylinder 23 side of the main path 31 relative to the inlet valve 41 and the wheel cylinder 25 side of the first valve 43. A release valve 42 is provided in the first sub-path 32a. An accumulator 45 and a pump 46 are provided in the second sub-path 32b, in this order from the first sub-path 32a side.

[0026] The pump 46 is driven by the motor 47 and sucks brake fluid from the first sub-channel 32a and discharges it to the main channel 31. The pump 46 is a reciprocating plunger pump. Specifically, the plunger of the pump 46 is intermittently pressed by an eccentric cam provided on the output shaft of the motor 47, thereby causing the pump 46 to pump and deliver brake fluid.

[0027] The supply flow path 33 communicates the master cylinder 23 side of the first valve 43 in the main flow path 31 with the suction side of the pump 46 in the sub-flow path 32. A second valve 44 is provided in the supply flow path 33.

[0028] The inlet valve 41 is, for example, a solenoid valve that is open in a de-energized state and closed in a powered state. The release valve 42 is, for example, a solenoid valve that is closed in a de-energized state and open in a powered state. The first valve 43 is, for example, a solenoid valve that is open in a de-energized state and closed in a powered state. The second valve 44 is, for example, a solenoid valve that is closed in a de-energized state and open in a powered state. By controlling the operation of these valves and the motor 47, the braking force acting on each wheel 2 is controlled.

[0029] For example, during normal operation when antilock brake control (described later) or the like is not being executed, inlet valve 41 is open, release valve 42 is closed, first valve 43 is open, and second valve 44 is closed. This allows brake fluid to flow from master cylinder 23 to wheel cylinder 25 only through main flow path 31, without passing through sub-flow path 32 and supply flow path 33. When brake pedal 21 is depressed in this state, the master cylinder pressure is increased, which in turn increases the wheel cylinder pressure, thereby applying braking force to wheel 2.

[0030] Furthermore, for example, when anti-lock brake control, which is a control for preventing the wheels 2 from locking, is executed, first, the inlet valve 41 is closed, the release valve 42 is opened, the first valve 43 is opened, and the second valve 44 is closed. This stops the flow of brake fluid between the main flow path 31 and the wheel cylinders 25, allowing brake fluid to flow from the wheel cylinders 25 to the secondary flow path 32. Therefore, brake fluid flows from the wheel cylinders 25 to the accumulator 45, reducing the wheel cylinder pressure and the braking force applied to the wheels 2. The brake fluid that has flowed into the accumulator 45 is returned to the main flow path 31 via the secondary flow path 32 by driving the pump 46.

[0031] Then, from the above state, both the inlet valve 41 and the release valve 42 are closed, stopping the flow of brake fluid between the main flow path 31 and the sub-flow path 32 and the wheel cylinders 25, maintaining the wheel cylinder pressure and maintaining the braking force applied to the wheels 2. Thereafter, the inlet valve 41 is opened and the release valve 42 is closed, restarting the flow of brake fluid between the main flow path 31 and the wheel cylinders 25, increasing the wheel cylinder pressure and increasing the braking force applied to the wheels 2.

[0032] Here, the hydraulic control unit 12 can also automatically increase the wheel cylinder pressure without requiring a brake operation. For example, when automatically increasing the wheel cylinder pressure without requiring a brake operation, the inlet valve 41 is opened, the release valve 42 is closed, the first valve 43 is closed, and the second valve 44 is opened. This allows brake fluid to flow from the master cylinder 23 to the wheel cylinder 25 via the supply flow path 33 and the sub-flow path 32. In this state, the pump 46 is driven to increase the wheel cylinder pressure, generating a braking force that brakes the wheels 2.

[0033] In addition, when the wheel cylinder pressure is automatically increased, some of the inlet valves 41 can be opened and other inlet valves 41 can be closed, thereby applying braking force only to the wheels 2 corresponding to those some of the inlet valves 41.

[0034] 3 is a block diagram showing an example of the functional configuration of control device 15. Control device 15 may be, for example, a single device or may be divided into multiple devices. When control device 15 is divided into multiple devices, the various functions described below are shared among the multiple devices, so that, for example, some functions of control unit 15b described below and other functions may be shared by different devices.

[0035] As shown in FIG. 3, the control device 15 includes, for example, an acquisition unit 15a and a control unit 15b.

[0036] The acquisition unit 15a acquires information from each device in the vehicle 1. For example, the acquisition unit 15a acquires information from the wheel speed sensor 13 and the inertial measurement unit 14. In this specification, the acquisition of information may include the extraction or generation (e.g., calculation) of information.

[0037] The control unit 15b executes various controls by controlling the operation of each device in the vehicle 1. For example, the control unit 15b controls the operation of the drive source 11 and the hydraulic control unit 12.

[0038] Here, the control unit 15b can execute traction control, which is control for stabilizing the behavior of the vehicle 1 by suppressing slip (i.e., spin) of the wheels 2 caused by the driving force while the vehicle 1 is traveling. As will be described later, the control unit 15b can switch between and execute off-road traction control, which is traction control for off-road traveling, and normal traction control other than the off-road traction control. Note that the normal traction control corresponds to an example of the first control according to the present invention, and the off-road traction control corresponds to an example of the second control according to the present invention. Prior to describing the off-road traction control, the normal traction control will be described below with reference to FIG. 4.

[0039] FIG. 4 is a diagram showing a state in which the vehicle 1 is traveling on a low-friction road 51. In FIG. 4, the low-friction road 51 is indicated by hatching. The low-friction road 51 refers to a road surface with a low coefficient of friction, such as an icy road surface. As shown in FIG. 4, the vehicle 1 is equipped with a front differential device 3a and a rear differential device 3b.

[0040] The front differential 3a is connected to the left front wheel 2a and the right front wheel 2b via drive shafts. A portion of the driving force output from the drive source 11 is transmitted to the front differential 3a, and then distributed and transmitted by the front differential 3a to the left front wheel 2a and the right front wheel 2b.

[0041] The rear differential 3b is connected to the left rear wheel 2c and the right rear wheel 2d via drive shafts. A portion of the driving force output from the drive source 11 is transmitted to the rear differential 3b, and then distributed and transmitted by the rear differential 3b to the left rear wheel 2c and the right rear wheel 2d.

[0042] In the example of FIG. 4, all of the wheels 2 of the vehicle 1 are positioned on a low μ road 51. In such a situation, even if the driving force of the vehicle 1 is small, slippage is likely to occur in each wheel 2. Therefore, for example, slippage may occur in all of the wheels 2. Normal traction control is a control for stabilizing the behavior of the vehicle 1 in such a case by suppressing slippage in each wheel 2.

[0043] In the normal traction control, the control unit 15b controls the drive source 11, for example, to reduce the driving force of the vehicle 1 (i.e., the driving force output from the drive source 11). For example, when the control unit 15b determines that slippage is occurring in at least one wheel 2, the control unit 15b executes the normal traction control and reduces the driving force of the vehicle 1. This suppresses slippage of the wheel 2. Note that the control unit 15b may determine that slippage is occurring in a wheel 2, for example, when the slip ratio of the wheel 2 exceeds a target slip ratio. Here, the slip ratio is an index indicating the degree to which the wheel 2 is slipping relative to the road surface, and is, for example, a value obtained by dividing the difference between the speed of the vehicle 1 (i.e., vehicle speed) and the wheel speed by the speed of the vehicle 1. The acquisition unit 15a may acquire the speed of the vehicle 1, for example, based on the detection results of each wheel speed sensor 13.

[0044] Note that, in normal traction control, control unit 15b may apply a braking force to a slipping wheel 2 in addition to or instead of reducing the driving force of vehicle 1. For example, control unit 15b can apply a braking force to a slipping wheel 2 by opening inlet valve 41 corresponding to the slipping wheel 2, closing release valve 42 corresponding to the wheel 2, closing first valve 43, opening second valve 44, and driving pump 46.

[0045] <Control device operation> The operation of the control device 15 according to the embodiment of the present invention will be described with reference to FIGS.

[0046] As described above, the control unit 15b of the control device 15 can execute traction control as control for suppressing slip of the wheels 2 due to the driving force and stabilizing the behavior of the vehicle 1. Here, various situations are conceivable in which slip of the wheels 2 due to the driving force occurs. It is desirable to optimize the behavior of the vehicle 1 in response to the occurring situation.

[0047] FIG. 5 is a diagram showing a state in which a vehicle 1 is traveling off-road. "Off-road" refers to an unpaved road surface. As shown in FIG. 5, on an off-road road, there is a bump 52 that protrudes upward from the road surface. In the example of FIG. 5, the right front wheel 2b and the left rear wheel 2c are positioned on the bump 52. As a result, the left front wheel 2a and the right rear wheel 2d are floating above the road surface. In this state shown in FIG. 5, the vehicle 1 may become stuck and be unable to move forward. In such a case, the wheels 2 that are floating above the road surface (the left front wheel 2a and the right rear wheel 2d in the example of FIG. 5) may slip.

[0048] If normal traction control is executed when the vehicle 1 is stuck off-road, as in the example of Figure 5, the normal traction control may reduce the driving force of the vehicle 1. In this case, it may become more difficult for the vehicle 1 to escape from the bump 52, making it more difficult to rid the vehicle 1 of the stuck state. Therefore, the control unit 15b is capable of executing off-road traction control, which is traction control for off-road driving to rid the vehicle 1 of the stuck state under such circumstances, and which is different from normal traction control.

[0049] In the off-road traction control, the control unit 15b, for example, applies a braking force to the wheel 2 that is slipping and increases the driving force of the vehicle 1. For example, when the control unit 15b determines that at least one wheel 2 is slipping, the control unit 15b automatically switches between normal traction control and off-road traction control and executes each of them depending on the behavior of the vehicle 1. This makes it possible to execute the off-road traction control when the vehicle 1 is stuck off-road, as in the example of FIG. 5. The process of switching between traction controls depending on the behavior of the vehicle 1 will be described in detail later.

[0050] Fig. 6 is a diagram showing an example of changes in the driving force DF and braking force BF of the vehicle 1 during each traction control performed by the control device 15. In Fig. 6, the horizontal axis represents time T, and the vertical axis represents the driving force DF and braking force BF of the vehicle 1, and the changes in the driving force DF and braking force BF are shown.

[0051] In Figure 6, the solid lines show the changes in driving force DF and braking force BF when off-road traction control is executed at time T1. Also in Figure 6, the two-dot chain lines show the changes in driving force DF and braking force BF when normal traction control is executed at time T1. As shown by the two-dot chain lines in Figure 6, when normal traction control starts at time T1, for example, the driving force DF decreases. On the other hand, as shown by the solid lines in Figure 6, when off-road traction control starts at time T1, for example, the driving force DF increases and braking force BF (specifically, braking force acting on the wheel 2 that is slipping) is generated.

[0052] As described above, in the normal traction control, the control unit 15b may apply a braking force to the slipping wheel 2. In this regard, in the off-road traction control, the control unit 15b applies a braking force that is greater than that in the normal traction control to the slipping wheel 2.

[0053] For example, in the example of Fig. 5, when off-road traction control is executed, braking force is automatically applied to the slipping left front wheel 2a and right rear wheel 2d. As a result, of the driving force distributed from the front differential 3a to the left front wheel 2a and right front wheel 2b, a larger proportion is distributed to the right front wheel 2b, which is positioned on the bump 52. Also, of the driving force distributed from the rear differential 3b to the left rear wheel 2c and right rear wheel 2d, a larger proportion is distributed to the left rear wheel 2c, which is positioned on the bump 52. As a result, the propulsion force of the vehicle 1 increases.

[0054] Furthermore, in the example of FIG. 5, when off-road traction control is executed, the driving force of the vehicle 1 (specifically, the driving force output from the driving source 11) automatically increases. This further increases the propulsive force of the vehicle 1. This allows the vehicle 1 to escape from the bump 52 and to become unstuck. Note that, in the off-road traction control, the control unit 15b may only perform a process to generate a braking force on the wheel 2 that is slipping, without performing a process to increase the driving force of the vehicle 1. Even in this case, the propulsive force of the vehicle 1 can be increased by the off-road traction control, allowing the vehicle 1 to escape from the bump 52 and to become unstuck.

[0055] As described above, the control unit 15b of the control device 15 automatically executes off-road traction control in accordance with the behavior of the vehicle 1. This allows the behavior of the vehicle 1 to be optimized in response to the current situation. Specifically, the control unit 15b automatically transitions the processing mode of the traction control in accordance with the behavior of the vehicle 1. This enables the off-road traction control to be automatically executed in accordance with the behavior of the vehicle 1. The processing mode of the traction control refers to the mode of processing performed by the control unit 15b regarding the traction control.

[0056] Fig. 7 is a diagram for explaining the transition of the traction control processing mode performed by the control device 15. As shown in Fig. 7, the traction control processing mode is switched between a prohibition mode M10 and a permission mode M20. The prohibition mode M10 is a mode in which off-road traction control is prohibited. The permission mode M20 is a mode in which off-road traction control is permitted.

[0057] The control unit 15b transitions the traction control processing mode to the prohibited mode M10 when any of the prohibition conditions for off-road traction control described below is satisfied. On the other hand, the control unit 15b transitions the traction control processing mode to the permitted mode M20 when none of the prohibition conditions described below is satisfied.

[0058] The prohibition mode M10 includes a first prohibition mode M11, a second prohibition mode M12, a third prohibition mode M13, and a fourth prohibition mode M14.

[0059] The first prohibition mode M11 is a mode to which the vehicle 1 transitions when a first prohibition condition is satisfied. The first prohibition condition is a condition that the vehicle 1 is stopped. In other words, when the control unit 15b determines that the vehicle 1 is stopped, the control unit 15b transitions the traction control processing mode to the first prohibition mode M11 and prohibits off-road traction control. For example, when the speed of the vehicle 1 is below a lower limit speed, the control unit 15b determines that the vehicle 1 is stopped. The lower limit speed is, for example, a predetermined speed that is higher than 0 km / h but close to 0 km / h. Note that the control unit 15b may also determine that the vehicle 1 is stopped when the speed of the vehicle 1 remains below the lower limit speed for a predetermined period of time.

[0060] When the vehicle 1 is stopped, even if the vehicle 1 is stuck off-road, it can be assumed that there is little need to get the vehicle 1 off the bump 52 and unstick the vehicle 1. Therefore, by prohibiting the off-road traction control in such a case, it is possible to prevent the off-road traction control from being executed unnecessarily.

[0061] The second prohibition mode M12 is a mode to which the vehicle 1 transitions when a second prohibition condition is satisfied. The second prohibition condition is a condition that the speed of the vehicle 1 is higher than a reference speed. In other words, when the control unit 15b determines that the speed of the vehicle 1 is higher than the reference speed, the control unit 15b transitions the traction control processing mode to the second prohibition mode M12 and prohibits off-road traction control. The reference speed is, for example, a speed high enough to determine that the vehicle 1 is not stuck off-road. Note that the control unit 15b may also prohibit off-road traction control when the speed of the vehicle 1 remains higher than the reference speed for a predetermined period of time.

[0062] If the speed of the vehicle 1 is higher than the reference speed, it can be assumed that the vehicle 1 is not stuck off-road. Therefore, by prohibiting the off-road traction control in such a case, unnecessary execution of the off-road traction control can be prevented.

[0063] The third prohibition mode M13 is a mode to which the control unit 15b transitions when a third prohibition condition is satisfied. The third prohibition condition is a condition that slippage occurs in all of the wheels 2. In other words, when the control unit 15b determines that slippage occurs in all of the wheels 2, the control unit 15b transitions the traction control processing mode to the third prohibition mode M13 and prohibits off-road traction control. Note that, as described above, the control unit 15b may determine that slippage occurs in a wheel 2 when, for example, the slip ratio of that wheel 2 exceeds a target slip ratio.

[0064] If slippage occurs on all of the wheels 2, it can be assumed that the vehicle 1 is not stuck off-road, and that all of the wheels 2 are positioned on a low μ road 51, as in the example of Fig. 4. Therefore, by prohibiting off-road traction control in such a case, it is possible to stabilize the behavior of the vehicle 1 by executing normal traction control.

[0065] The fourth prohibition mode M14 is a mode to which the vehicle 1 transitions when a fourth prohibition condition is satisfied. The fourth prohibition condition is a condition in which the driver of the vehicle 1 does not intend to accelerate. In other words, when the control unit 15b determines that the driver of the vehicle 1 does not intend to accelerate, the control unit 15b transitions the traction control processing mode to the fourth prohibition mode M14 and prohibits off-road traction control. The intention to accelerate means the intention to accelerate the vehicle 1. For example, when the vehicle 1 is stuck on an off-road road, the intention to accelerate means the intention to move the vehicle 1 away from the bump 52 and to unstick the vehicle 1.

[0066] The control unit 15b determines whether or not the driver of the vehicle 1 intends to accelerate based on, for example, the driving force of the vehicle 1 (i.e., the driving force output from the driving source 11). For example, if the driving force of the vehicle 1 is greater than a threshold, the control unit 15b determines that the driver of the vehicle 1 intends to accelerate, and if the driving force of the vehicle 1 is less than the threshold, the control unit 15b determines that the driver of the vehicle 1 does not intend to accelerate.

[0067] Here, the control unit 15b may determine whether or not the driver of the vehicle 1 intends to accelerate by taking into account the braking force of the vehicle 1 (i.e., the braking force applied to the vehicle 1 by the hydraulic control unit 12) in addition to the driving force of the vehicle 1. For example, the control unit 15b may determine that the driver of the vehicle 1 intends to accelerate if the value obtained by subtracting the braking force of the vehicle 1 from the driving force of the vehicle 1 is greater than a threshold value, and may determine that the driver of the vehicle 1 does not intend to accelerate if the value is less than the threshold value.

[0068] Furthermore, the control unit 15b may determine whether the driver of the vehicle 1 intends to accelerate by taking into account the gradient of the road on which the vehicle 1 is traveling, in addition to the driving force of the vehicle 1. For example, when the vehicle 1 is traveling uphill, the control unit 15b may determine that the driver of the vehicle 1 intends to accelerate if the value obtained by subtracting the component of gravity acting on the vehicle 1 in the fore-and-aft direction due to the gradient of the road from the driving force of the vehicle 1 is greater than a threshold value, and may determine that the driver of the vehicle 1 does not intend to accelerate if the value is less than the threshold value. Note that the acquisition unit 15a can acquire the gradient of the road based on, for example, the detection result of the inertial measurement unit 14. The control unit 15b can determine a larger value as the component of gravity acting on the vehicle 1 in the fore-and-aft direction due to the gradient of the road, as the gradient of the road increases.

[0069] If the driver of the vehicle 1 has no intention to accelerate, even if the vehicle 1 is stuck off-road, it can be assumed that there is little need to get the vehicle 1 off the bump 52 and unstick the vehicle 1. Therefore, by prohibiting the off-road traction control in such a case, unnecessary execution of the off-road traction control can be prevented.

[0070] In permission mode M20, control unit 15b estimates the probability of vehicle 1 becoming stuck off-road, and determines the traction control to be executed based on the estimated result of the probability of vehicle 1 becoming stuck. Specifically, as will be described later, control unit 15b sets the traction control to be executed to off-road traction control when the probability of vehicle 1 becoming stuck is higher than a standard, and sets the traction control to be executed to normal traction control when the probability of vehicle 1 becoming stuck is lower than the standard.

[0071] Information indicating whether off-road traction control or normal traction control is set as the traction control to be executed is stored, for example, in a storage element of the control device 15. Then, when it is determined that the execution conditions for traction control are satisfied (for example, when it is determined that slippage is occurring in at least one wheel 2), the control unit 15b executes the traction control that is set as the traction control to be executed. For example, a set mode in which normal traction control is set as the traction control to be executed may be called a normal mode, and a set mode in which off-road traction control is set as the traction control to be executed may be called an off-road mode.

[0072] The permitted mode M20 includes a low probability mode M21, a medium probability mode M22, and a high probability mode M23.

[0073] The low-probability mode M21 is a mode to which the system transitions when it is estimated that the probability of getting stuck is low. The high-probability mode M23 is a mode to which the system transitions when it is estimated that the probability of getting stuck is high. The medium-probability mode M22 is a mode to which the system transitions when it is estimated that the probability of getting stuck is higher than the low-probability mode M21 but lower than the high-probability mode M23. In the allowed mode M20, the processing mode switches between the low-probability mode M21, the medium-probability mode M22, and the high-probability mode M23 based on the estimation result of the probability of getting stuck. Note that when the processing mode transitions from one of the low-probability mode M21 and the high-probability mode M23 to the other, the transition may be via the medium-probability mode M22, or a direct transition may be possible without via the medium-probability mode M22.

[0074] Figure 8 is a flowchart showing an example of the flow of processing performed by the control device 15 in the permission mode M20. Step S101 in Figure 8 corresponds to the start of the processing flow shown in Figure 8. The processing flow shown in Figure 8 starts when the traction control processing mode transitions to the permission mode M20. The processing flow shown in Figure 8 ends when the traction control processing mode transitions to the prohibition mode M10.

[0075] 8 starts, the control unit 15b estimates the possibility of the vehicle 1 getting stuck in step S102. As described above, the possibility of the vehicle 1 getting stuck in an off-road situation is the possibility of the vehicle 1 getting stuck in an off-road situation.

[0076] In step S102, the control unit 15b may estimate the possibility of getting stuck based on, for example, the acceleration of the wheels 2 (specifically, the acceleration of the wheels 2 that are not slipping). Here, when some of the wheels 2 are slipping, it is necessary to determine whether the slip is occurring because the vehicle 1 is stuck off-road or because of some other factor.

[0077] 9 is a diagram showing a state in which only the wheels 2 on the left side of the vehicle 1 (i.e., the left front wheel 2a and the left rear wheel 2c) are positioned on the low μ road surface 51. In the example of FIG. 9, the left front wheel 2a and the left rear wheel 2c are positioned on the low μ road surface 51, but the right front wheel 2b and the right rear wheel 2d are not positioned on the low μ road surface 51. In this situation, slippage may occur only on the left front wheel 2a and the left rear wheel 2c.

[0078] 9, if off-road traction control is executed in a situation where only one of the left and right wheels 2 of the vehicle 1 (the left front wheel 2a and the left rear wheel 2c in the example of FIG. 9) is positioned on a low μ road surface 51, the vehicle 1 will travel mainly using the grip force of the other of the left and right wheels 2 (the right front wheel 2b and the right rear wheel 2d in the example of FIG. 9). This will cause the vehicle 1 to turn toward the low μ road surface 51 (the left side in the example of FIG. 9), causing all of the wheels 2 to enter the low μ road surface 51, which may make the behavior of the vehicle 1 more unstable.

[0079] Therefore, in a situation where only one of the left and right wheels 2 of the vehicle 1 is located on a low μ road surface 51, as in the example of Fig. 9, the behavior of the vehicle 1 should be stabilized by normal traction control, not by off-road traction control. Therefore, based on the acceleration of the wheel 2 that is not slipping, the control unit 15b determines whether a situation has occurred where only one of the left and right wheels 2 of the vehicle 1 is located on a low μ road surface 51, as in the example of Fig. 9, or whether a situation has occurred where the vehicle 1 is stuck off-road.

[0080] FIG. 10 is a diagram showing an example of the transition of the acceleration AC of the wheel 2 of the vehicle 1 (specifically, the acceleration of the wheel 2 when no slip occurs). In FIG. 10, the horizontal axis represents time T and the vertical axis represents the acceleration AC of the wheel 2 when no slip occurs, and the transition of the acceleration AC of the wheel 2 is shown. Note that the acquisition unit 15a can acquire the acceleration AC of the wheel 2 (i.e., the acceleration of the wheel 2 in the longitudinal direction of the vehicle) based on, for example, the detection result of the wheel speed sensor 13.

[0081] When the vehicle 1 is stuck off-road, the acceleration AC of the wheel 2 does not increase significantly over time, as shown by the solid line in Fig. 10. On the other hand, when only one of the left and right wheels 2 of the vehicle 1 is located on a low μ road 51, as shown by the example in Fig. 9, the acceleration AC of the wheel 2 increases significantly over time compared to when the vehicle 1 is stuck off-road, as shown by the two-dot chain line in Fig. 10. Therefore, the control unit 15b estimates the possibility of the vehicle 1 getting stuck based on, for example, the amount of increase in the acceleration AC of the wheel 2 over a predetermined period of time.

[0082] For example, if the increase in the acceleration AC of the wheel 2 over a predetermined time period is smaller than a first threshold, the control unit 15b estimates that the possibility of the wheel 2 getting stuck is high. In this case, for example, the processing mode transitions to the high possibility mode M23 in FIG. 7. Alternatively, for example, if the increase in the acceleration AC of the wheel 2 over a predetermined time period is larger than the first threshold and smaller than a second threshold that is larger than the first threshold, the control unit 15b estimates that the possibility of the wheel 2 getting stuck is medium. In this case, for example, the processing mode transitions to the medium possibility mode M22 in FIG. 7. Alternatively, for example, if the increase in the acceleration AC of the wheel 2 over a predetermined time period is larger than a second threshold, the control unit 15b estimates that the possibility of the wheel 2 getting stuck is low. In this case, for example, the processing mode transitions to the low possibility mode M21 in FIG. 7. Note that the control unit 15b may continuously change the possibility of the wheel 2 getting stuck in accordance with the increase in the acceleration AC of the wheel 2 over a predetermined time period.

[0083] In step S102, the control unit 15b may also estimate the possibility of the vehicle 1 getting stuck based on the driving force and speed of the vehicle 1, for example.

[0084] Fig. 11 is a diagram showing an example of changes in driving force DF and speed VS of the vehicle 1. In Fig. 11, the horizontal axis represents time T, and the vertical axis represents driving force DF and speed VS of the vehicle 1, and the changes in driving force DF and speed VS are shown.

[0085] In the example of Figure 11, the vehicle 1 is traveling with a driving force DF being continuously output from the driving source 11. Here, the speed VS of the vehicle 1 increases and then decreases in the region indicated by the dashed-dotted line in Figure 11. When the driving force DF is maintained at a relatively high value but the speed VS is decreasing (i.e., the vehicle 1 is decelerating), as in the region indicated by the dashed-dotted line in Figure 11, it can be inferred that the vehicle 1 is stuck off-road.

[0086] Therefore, for example, when the driving force DF is maintained at a relatively high value but the speed VS is decreasing, the control unit 15b may estimate that the likelihood of getting stuck is increasing. For example, when the processing mode is the low-probability mode M21 in Figure 7 and a situation occurs in which the driving force DF is maintained at a relatively high value but the speed VS is decreasing, the control unit 15b may transition the processing mode to the medium-probability mode M22 in Figure 7. Also, for example, when the processing mode is the medium-probability mode M22 in Figure 7 and a situation occurs in which the driving force DF is maintained at a relatively high value but the speed VS is decreasing, the control unit 15b may transition the processing mode to the high-probability mode M23 in Figure 7.

[0087] The above describes an example in which the possibility of getting stuck is estimated based on the acceleration of the wheels 2 that are not slipping, and an example in which the possibility of getting stuck is estimated based on the driving force and speed of the vehicle 1. However, the control unit 15b may estimate the possibility of getting stuck based on both the acceleration of the wheels 2 that are not slipping and the driving force and speed of the vehicle 1, or may estimate the possibility of getting stuck based on only one of the acceleration of the wheels 2 that are not slipping and the driving force and speed of the vehicle 1.

[0088] After step S102 in FIG. 8, in step S103, the control unit 15b determines whether the probability of getting stuck is higher than a reference value.

[0089] In step S103, for example, when the processing mode is the low possibility mode M21 in Fig. 7, the control unit 15b determines that the possibility of getting stuck is lower than the standard, and when the processing mode is the high possibility mode M23 in Fig. 7, the control unit 15b determines that the possibility of getting stuck is higher than the standard. Here, for example, when the processing mode is the medium possibility mode M22 in Fig. 7, the control unit 15b determines that the possibility of getting stuck is higher than the standard if a predetermined condition is satisfied, and determines that the possibility of getting stuck is lower than the standard if the predetermined condition is not satisfied.

[0090] An example of the predetermined condition is that the time during which the processing mode is maintained in the medium probability mode M22 in Fig. 7 exceeds a threshold value. That is, the control unit 15b may estimate that the longer the time during which the processing mode is maintained in the medium probability mode M22 in Fig. 7, the higher the possibility of the device being stuck.

[0091] Furthermore, the predetermined condition may be, for example, that the time elapsed since the processing mode transitioned from the high-probability mode M23 to the medium-probability mode M22 in Fig. 7 is shorter than a threshold value. That is, the control unit 15b may estimate that the shorter the time elapsed since the processing mode transitioned from the high-probability mode M23 to the medium-probability mode M22 in Fig. 7, the higher the possibility of getting stuck.

[0092] Note that, when the processing mode is the medium possibility mode M22 in Fig. 7, the control unit 15b may change the probability of getting stuck by taking into account parameters other than the time during which the processing mode is maintained in the medium possibility mode M22 in Fig. 7 and the elapsed time since the processing mode transitioned from the high possibility mode M23 in Fig. 7 to the medium possibility mode M22. For example, when the processing mode is the medium possibility mode M22 in Fig. 7 and the driving force of the vehicle 1 is low, the control unit 15b may determine that the driver of the vehicle 1 does not intend to accelerate and reduce the probability of getting stuck.

[0093] If it is determined that the possibility of getting stuck is higher than the reference value (YES in step S103), the process proceeds to step S104. In step S104, the control unit 15b sets the traction control to be executed to off-road traction control (i.e., sets the traction control setting mode to the off-road mode), and returns to step S102. In this case, for example, if it is determined that slippage is occurring in at least one wheel 2, the off-road traction control is executed.

[0094] On the other hand, if it is determined that the possibility of getting stuck is lower than the reference value (step S103 / NO), the process proceeds to step S105. In step S105, the control unit 15b sets the traction control to be executed to normal traction control (i.e., sets the traction control setting mode to normal mode), and returns to step S102. In this case, for example, if it is determined that slippage is occurring in at least one wheel 2, the normal traction control is executed.

[0095] The above describes an example of the processing performed by the control device 15. However, the processing performed by the control device 15 is not limited to the above example of processing, and may be, for example, a processing obtained by appropriately modifying the above example of processing.

[0096] For example, the above describes an example in which the control unit 15b estimates the possibility of getting stuck in three stages (specifically, an example in which, in the permission mode M20, the processing mode switches between a low possibility mode M21, a medium possibility mode M22, and a high possibility mode M23 depending on the possibility of getting stuck). However, the control unit 15b may estimate the possibility of getting stuck in more stages. Alternatively, the control unit 15b may estimate the possibility of getting stuck in two stages: low possibility and high possibility.

[0097] In the above example, the control unit 15b uses the first prohibition condition, the second prohibition condition, the third prohibition condition, and the fourth prohibition condition as the prohibition conditions for off-road traction control (specifically, the example in which the prohibition mode M10 includes the first prohibition mode M11, the second prohibition mode M12, the third prohibition mode M13, and the fourth prohibition mode M14). However, the control unit 15b does not have to use some or all of the first prohibition condition, the second prohibition condition, the third prohibition condition, and the fourth prohibition condition as the prohibition conditions for off-road traction control. In other words, some or all of the first prohibition mode M11, the second prohibition mode M12, the third prohibition mode M13, and the fourth prohibition mode M14 may be omitted from the prohibition mode M10.

[0098] <Effects of the control device> The effects of the control device 15 according to the embodiment of the present invention will be described.

[0099] The control device 15 includes a control unit 15b that executes a first control (normal traction control in the above example) to suppress slippage when slippage occurs in the wheels 2 due to driving force, and a second control (off-road traction control in the above example) to apply a braking force greater than that in the first control to the slipping wheels 2 when slippage occurs. The control unit 15b then automatically executes the second control in accordance with the behavior of the vehicle 1. This allows the control unit 15b to focus on the behavior of the vehicle 1, respond to the current situation, and automatically switch between the first control and the second control. This makes it possible to optimize the behavior of the vehicle 1.

[0100] Furthermore, because the control device 15 can automatically switch between the first control and the second control, there is no need to manually switch between a setting mode in which the first control is set as the traction control to be executed and a setting mode in which the second control is set as the traction control to be executed. This eliminates the need for additional devices to switch between setting modes and reduces the effort required to switch between setting modes.

[0101] Preferably, in the control device 15, the control unit 15b applies a larger braking force to the slipping wheel 2 in the second control (off-road traction control in the above example) than in the first control (normal traction control in the above example), and increases the driving force of the vehicle 1. This makes it possible to more effectively increase the propulsive force of the vehicle 1 through the second control. Therefore, the second control more appropriately enables the vehicle 1 to escape from the bump 52 and to rid the vehicle 1 of being stuck.

[0102] Preferably, in the control device 15, the control unit 15b prohibits the second control (off-road traction control in the above example) when it is determined that the vehicle 1 is stopped. This makes it possible to prevent the second control from being unnecessarily executed when the vehicle 1 is stopped.

[0103] Preferably, in the control device 15, the control unit 15b prohibits the second control (off-road traction control in the above example) when it is determined that the speed of the vehicle 1 is higher than the reference speed. This makes it possible to prevent the second control from being unnecessarily executed when the speed of the vehicle 1 is higher than the reference speed.

[0104] Preferably, in the control device 15, the control unit 15b prohibits the second control (off-road traction control in the above example) when it is determined that slippage is occurring in all of the wheels 2. By prohibiting the second control when slippage is occurring in all of the wheels 2, the first control (normal traction control in the above example) can be executed to stabilize the behavior of the vehicle 1.

[0105] Preferably, in the control device 15, the control unit 15b prohibits the second control (off-road traction control in the above example) when it is determined that the driver of the vehicle 1 does not intend to accelerate. This makes it possible to prevent the second control from being unnecessarily executed when the driver of the vehicle 1 does not intend to accelerate.

[0106] Preferably, in the control device 15, the control unit 15b executes the second control (off-road traction control in the above example) based on the acceleration of the wheels 2 that are not slipping. This makes it possible to execute the second control after appropriately estimating the possibility of getting stuck in consideration of the acceleration of the wheels 2 that are not slipping. Therefore, it is possible to distinguish whether the slip is occurring because the vehicle 1 is stuck off-road or due to some other factor, and then appropriately execute the second control in response to the occurring situation.

[0107] Preferably, in the control device 15, the control unit 15b executes the second control (off-road traction control in the above example) based on the driving force and speed of the vehicle 1. This makes it possible to execute the second control after appropriately estimating the possibility of the vehicle 1 getting stuck in consideration of the driving force and speed of the vehicle 1. Therefore, it is possible to distinguish whether the slippage is caused by the vehicle 1 getting stuck off-road or by some other factor, and then appropriately execute the second control in response to the situation that has occurred.

[0108] The above describes a preferred embodiment of the present invention with reference to the accompanying drawings. However, it goes without saying that the present invention is not limited to the above-described embodiment, and various modified or altered examples within the scope of the claims also fall within the technical scope of the present invention.

[0109] For example, the processes described herein using flowcharts do not necessarily have to be performed in the order shown in the flowcharts, some process steps may be performed in parallel, additional process steps may be employed, and some process steps may be omitted.

[0110] Furthermore, for example, the series of processes performed by the control device 15 described above may be realized using software, hardware, or a combination of software and hardware. The programs constituting the software are stored in advance in, for example, a storage medium provided inside or outside the information processing device. [Explanation of symbols]

[0111] 1 vehicle 2 wheels 2a Left front wheel 2b Right front wheel 2c left rear wheel 2d right rear wheel 3a Front differential device 3b Rear differential device 11. Drive source 12 Hydraulic control unit 13 Wheel speed sensor 14 Inertial Measurement Unit 15 Control device 15a Acquisition part 15b Control section 20 Brake System 21 Brake pedal 22 Booster 23 Master cylinder 24 reservoir 25 Wheel cylinder 31 Main channel 32 Subchannel 33 Supply channel 41 Inlet valve 42 Release valve 43 First Valve 44 Second valve 45 Accumulator 46 Pump 47 Motor 51 Low μ road 52 Bump M10 Prohibited Mode M11 1st prohibition mode M12 Second prohibition mode M13 Third prohibition mode M14 4th Prohibited Mode M20 Permit Mode M21 Low Probability Mode M22 Medium Potential Mode M23 High Availability Mode

Claims

1. A control device (15) for controlling the operation of a vehicle (1), a control unit (15b) that executes a first control for suppressing slippage when slippage of a wheel (2) occurs due to a driving force, and a second control for applying a braking force greater than that of the first control to the wheel (2) in which slippage occurs when the slippage occurs, The control unit (15b) automatically executes the second control in accordance with the behavior of the vehicle (1). Control device.

2. In the second control, the control unit (15b) applies a braking force to the wheel (2) where the slipping is occurring that is greater than that in the first control, and increases the driving force of the vehicle (1). The control device according to claim 1 .

3. The control unit (15b) prohibits the second control when it determines that the vehicle (1) is stopped. The control device according to claim 1 or 2.

4. The control unit (15b) prohibits the second control when it determines that the speed of the vehicle (1) is higher than a reference speed. The control device according to claim 1 or 2.

5. The control unit (15b) prohibits the second control when it is determined that the slippage occurs in all of the wheels (2). The control device according to claim 1 or 2.

6. The control unit (15b) prohibits the second control when it is determined that the driver of the vehicle (1) does not intend to accelerate. The control device according to claim 1 or 2.

7. The control unit (15b) executes the second control based on the acceleration of the wheel (2) in which slipping does not occur. The control device according to claim 1 or 2.

8. The control unit (15b) executes the second control based on the driving force and speed of the vehicle (1). The control device according to claim 1 or 2.

9. A control method for controlling an operation of a vehicle (1), comprising: a control unit (15b) of the control device (15) executes a first control for suppressing slippage of a wheel (2) caused by a driving force, and a second control for applying a braking force greater than that of the first control to the wheel (2) in which the slippage occurs, when the slippage occurs; The control unit (15b) automatically executes the second control in accordance with the behavior of the vehicle (1). Control method.

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