Vehicular control device

Abstract

To provide a vehicular control device which can improve, while reducing disturbance to a turning vehicle derived from acceleration / deceleration, steering responsiveness at initial stage of steering.SOLUTION: A vehicular control device makes a front motor and a rear motor that are traveling power sources output a first driving force which is applied to right and left front wheels at a longitudinal distribution ratio configured to satisfy requested driving force and a second driving force which is applied to right and left rear wheels at the longitudinal distribution ratio configured to satisfy the requested driving force. The vehicular control device performs, when steering of the vehicle is generated within the range of a prescribed steering angle determined in advance as an initial stage of steering during a fixed speed travel of the vehicle (Yes at Step S4), adjustment processing (Step S5) to adjust the longitudinal distribution ratio to improve a yaw rate response related to the steering angle.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Conventionally, there are known techniques for improving the steering response of a vehicle. For example, Patent Document 1 describes a vehicle steering behavior improvement device that increases the driving force to the wheels when it detects that steering has been performed and then reduces it after a predetermined time. This device improves steering response by quickly increasing the yaw rate at the beginning of steering while avoiding the adverse effect of increasing the driving force other than at the beginning of steering. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5526983 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in order to achieve a sufficient improvement in steering response using the control method described in Patent Document 1, it may be necessary to significantly change the driving force, which may result in shocks due to acceleration and deceleration during cornering.

[0005] The present invention has been made in consideration of such problems, and its purpose is to provide a vehicle control device that can improve steering response at the initial stage of steering while preventing shocks caused by acceleration and deceleration from occurring in a turning vehicle. [Means for solving the problem]

[0006] In order to achieve the above object, the vehicle control device of the present invention is a vehicle control device that controls the vehicle so that a first braking / driving force is applied to the left and right front wheels and a second braking / driving force is applied to the left and right rear wheels at a distribution ratio set so that the required braking / driving force required by the vehicle is satisfied, and is characterized in that when steering of the vehicle occurs within a predetermined angle range that is predetermined as the initial steering angle while the vehicle is traveling at a constant speed, an adjustment process is executed to adjust the distribution ratio so that the yaw rate response to the steering angle tends to be faster. [Effects of the Invention]

[0007] According to the vehicle control device of the present invention, it is possible to improve steering response in the initial stage of steering while preventing shocks due to acceleration or deceleration from occurring in a turning vehicle. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram illustrating an example of a vehicle equipped with a vehicle control device according to an embodiment; [Figure 2] FIG. 1 is an explanatory diagram schematically illustrating a vehicle turning; [Figure 3] 10 is a flowchart showing an example of distribution ratio adjustment control. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a schematic diagram showing an example of a vehicle equipped with a vehicle control device according to an embodiment. The vehicle 1 is a four-wheel drive electric vehicle that travels by transmitting power from a front motor 10f, which serves as a power source for traveling, to left and right front wheels 2f, and transmitting power from a rear motor 10r, which also serves as a power source for traveling, to left and right rear wheels 2r. Note that the vehicle 1 may be an electronically controlled on-demand four-wheel drive vehicle that can apply driving force to the front wheels 2f and the rear wheels 2r at any desired distribution ratio, and may be, for example, an electronically controlled on-demand four-wheel drive vehicle that can use an electronically controlled coupling to turn a driven wheel into a driving wheel.

[0010] The front motor 10f outputs driving force to the left and right front wheels 2f via a transaxle 12f, which includes a transmission and a differential gear, and left and right front axles 13f. The rear motor 10r outputs driving force to the left and right rear wheels 2r via a transaxle 12r, which also includes a transmission and a differential gear, and left and right rear axles 13r. The vehicle 1 is equipped with a battery 14 serving as a power source, which is configured as a secondary battery such as a lithium-ion battery, and power from the battery 14 is supplied to the front motor 10f and the rear motor 10r via a power conversion device such as an inverter (not shown). The front motor 10f and the rear motor 10r are drive-controlled by a control device 16 (vehicle control device).

[0011] The control device 16 includes input / output devices, storage devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), etc., and performs overall control of the vehicle 1. The control device 16 receives inputs of vehicle speed V from a vehicle speed sensor 21 mounted on the vehicle 1, accelerator pedal position P from an accelerator pedal position sensor 22, steering angle δ of the vehicle 1 from a steering angle sensor 23, and other detected quantities detected by various sensors (not shown), such as brake stroke and wheel speed, as well as operation information of various devices. The control device 16 also receives inputs of a signal indicating a vehicle mode from a mode selection switch 24. The mode selection switch 24 is mounted in the passenger compartment (not shown) and is configured to allow the driver to select one of a plurality of vehicle modes. The plurality of vehicle modes includes at least a fuel-efficiency-oriented mode that prioritizes fuel economy over responsiveness to driving operations of the vehicle 1, and a performance-oriented mode that prioritizes responsiveness to driving operations over fuel economy.

[0012] The control device 16 then calculates information necessary for controlling the vehicle 1, such as the required driving force required for running the vehicle 1, based on the input detected amount, operation information of various devices, vehicle mode, etc., and controls various devices such as the front motor 10f and the rear motor 10r based on the calculated information. Specifically, the control device 16 calculates the first driving force F applied from the front motor 10f to the front wheels 2f. df and a second driving force F applied from the rear motor 10r to the rear wheel 2r. drThe required driving force F d The first driving force F df and the second driving force F dr Front-to-rear distribution ratio α c (Distribution ratio) is set (see formula (1)). c is set taking into consideration traction, driving stability, fuel economy, etc. for each situation, such as when the vehicle 1 is driving straight or turning.

[0013]

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[0014] (Improved steering response) In the vehicle 1 configured as described above, improvements in traction performance and maneuverability, particularly near the grip limit, are often sought to improve dynamic performance. However, it is also desirable to improve the steering response of the vehicle 1 (improving turning ability) not only near the grip limit but also at the initial stage of steering when the steering angle δ is within a range commonly used in daily driving. While it is possible to improve steering response by modifying the vehicle 1's hardware configuration, such as the suspension system and tires, modifying the hardware configuration may affect the ride comfort of the vehicle 1 and increase costs. While it is also possible to improve steering response by adjusting the total driving force applied to the vehicle 1, achieving sufficient results may require a large change in driving force, which may result in shocks due to acceleration and deceleration during cornering. Therefore, the control device 16 of this embodiment executes the control described below to improve steering response at the initial stage of steering while suppressing shocks due to acceleration and deceleration without modifying the hardware configuration.

[0015] (Steering response and front-rear distribution ratio) First, the steering response and the front / rear distribution ratio α cThe relationship between the above will be explained. Figure 2 is an explanatory diagram that shows a model of a vehicle 1 that is turning. As shown in the figure, it is assumed that the vehicle 1, which is traveling at a constant speed V, is turning left at a yaw rate γ. In this case, the lateral motion equation of the vehicle 1 using a two-wheel model (a model in a linear region where the vehicle is traveling at a constant speed and the slip angle is small) can be expressed by the following equation (2), and the motion equation for the rotation around the center axis of gravity of the vehicle 1 can be expressed by the following equation (3). "β" in the equation is the slip angle of the vehicle 1, "Y f " is the cornering force (lateral force) acting on the front wheel 2f, and "Y r "The cornering force acting on the rear wheels 2r is the same value on both the left and right. Also, "I" is the moment of inertia acting on the center of gravity CG of vehicle 1, "m" is the mass of vehicle 1, "l f " is the distance between the front axle 13f and the center of gravity CG, "l r " is the distance between the rear axle 13r and the center of gravity CG, and "l" is the distance between the front axle 13f and the rear axle 13r.

[0016]

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[0018] Furthermore, Cornering Force Y f is expressed by the following equation (4), and the cornering force Y r can be expressed by the following equation (5). f " is the cornering power of each front wheel 2f, "K f " is the cornering power of each rear wheel 2r, β f is the slip angle of each front wheel 2f, β f is the slip angle of each rear wheel 2r, and both are assumed to be the same value on the left and right.

[0019]

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[0021] Based on equations (4) and (5), equation (2) can be expressed as equation (6), and equation (3) can be expressed as equation (7). By applying Laplace transformation to the equations of motion in equations (6) and (7), it is possible to obtain a first-order lag relation between the steering angle δ and the yaw rate γ, and the time constant t R can be expressed by equation (8). R To minimize the sum "K f l f +K r l r " should be maximized.

[0022]

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[0025] In addition, the cornering power Kf and Kr are determined by the front-rear distribution ratio α c It can be expressed by the formulas (9) and (10) including "K f0 " is the cornering power of the front wheels 2f when no driving force is applied, "K r0 " is the cornering power of rear wheel 2r when no driving force is applied, "μ" is the friction coefficient between the wheels of vehicle 1 and the ground, "W" is the contact load acting on vehicle 1, and "R" is the running resistance of vehicle 1.

[0026]

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[0028] Therefore, Japanese f l f +K r l r " can be expressed by equation (11), and the time constant t R The sum that minimizes "K f l f +K r l r " is obtained by the front-rear distribution ratio α c It can be seen that the value calculated by the formula (12) is the value calculated by the formula (12). In this embodiment, the front / rear distribution ratio α c The ideal distribution ratio α ci "

[0029]

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[0030]

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[0031] (Allocation ratio adjustment control) Next, the above ideal distribution ratio α ci The distribution ratio adjustment control for improving steering response at the initial stage of steering using the above will be described with reference to Fig. 3. Fig. 3 is a flowchart showing an example of the distribution ratio adjustment control. The process shown in Fig. 3 is repeatedly executed by the control device 16 at predetermined time intervals (for example, every few msec) while the vehicle 1 is traveling.

[0032] The control device 16 determines whether the vehicle speed V acquired from the vehicle speed sensor 21 is less than a predetermined vehicle speed V1 (step S1). The predetermined vehicle speed V1 is determined in advance as a vehicle speed at which high steering response may result in a decrease in driving stability. The predetermined vehicle speed V1 is, for example, about 120 km / h.

[0033] When the control device 16 determines that the vehicle speed V is less than the predetermined vehicle speed V1 (Yes in step S1), it determines whether the vehicle 1 is traveling at a constant speed (step S2). The vehicle 1 is considered to be traveling at a constant speed when the ideal distribution ratio α ci This is a state in which the vehicle speed V falls within a small change range to such an extent that the above-mentioned can be used.

[0034] When the control device 16 determines that the vehicle 1 is traveling at a constant speed (Yes in step S2), it determines whether the vehicle mode is set to a fuel efficiency priority mode or a performance priority mode (step S3). When the control device 16 determines in step S3 that the vehicle mode is set to the fuel efficiency priority mode, it determines whether steering of the vehicle 1 occurs within a predetermined angle range of the steering angle δ (step S4). The predetermined angle range is determined in advance as the value of the steering angle δ that indicates the initial stage of steering of the vehicle 1. The predetermined angle range is, for example, a range of 50° or less.

[0035] When it is determined that the steering angle δ is within a predetermined angle range of the vehicle 1 (Yes in step S4), the control device 16 adjusts the front / rear distribution ratio α so that the yaw rate response to the steering angle δ tends to be quicker. c As an adjustment process for adjusting the ideal distribution ratio α ci The front-rear distribution ratio α c (Step S5). This allows the yaw rate response to the steering angle δ to be the fastest, making it possible to improve the steering response at the initial stage of steering. After the process of step S5, the control device 16 again executes the processes from step S1 onwards.

[0036] On the other hand, when the control device 16 determines that the vehicle speed V is equal to or greater than the predetermined vehicle speed V1 (No in step S1) or when it determines that the vehicle 1 is not traveling at a constant speed (No in step S2), it omits the adjustment process in step S5 in consideration of traveling stability and executes the processes from step S1 onwards again. Also, when the control device 16 determines that the steering angle δ is within a predetermined angle range and no steering is occurring in the vehicle 1 (the vehicle 1 is not turning, or is turning but is not in the initial stage of steering) (No in step S4), it omits the adjustment process in step S5 and executes the processes from step S1 onwards again. In this case, the front / rear distribution ratio α c As described above, the value is appropriately set in consideration of traction, running stability, fuel economy, etc. for each situation, such as when the vehicle 1 is running straight or when it is turning.

[0037] Furthermore, when the control device 16 determines in step S3 that the vehicle mode is set to the performance-oriented mode, it skips the processing of step S4 and executes the adjustment processing (step S5), and executes the processing from step S1 onwards again. That is, if the vehicle mode is the performance-oriented mode, the adjustment processing is executed even when no steering is occurring in the vehicle 1. As a result, in the performance-oriented mode, it is possible to maintain a vehicle state with improved steering response even before steering occurs, and therefore it is possible to further improve steering response when steering actually occurs.

[0038] (Effects of the embodiment) As described above, the control device 16 (vehicle control device) of the embodiment adjusts the front / rear distribution ratio α so that the yaw rate response to the steering angle δ tends to be faster when the steering of the vehicle 1 occurs within a predetermined angle range that is predetermined as the initial steering angle while the vehicle 1 is traveling at a constant speed. c (Step S5). With this configuration, the front-rear distribution ratio α cThe yaw rate response of the vehicle 1 can be increased simply by adjusting the above. Therefore, the control device 16 of the embodiment can improve the steering response at the initial stage of steering while preventing shocks due to acceleration or deceleration from occurring in the vehicle 1 during cornering. Furthermore, since the hardware configuration of the vehicle 1 is not changed, it is possible to suppress the impact on ride comfort and increase in costs.

[0039] The adjustment process in step S5 is also performed by adjusting the time constant t of the yaw rate response to the steering angle δ. R The ideal allocation ratio α that minimizes ci The front-rear distribution ratio α c This configuration makes it possible to speed up the yaw rate response of the vehicle 1 through the adjustment process, and to further improve the steering response at the initial stage of steering.

[0040] Furthermore, when the vehicle speed V is equal to or greater than the predetermined vehicle speed V1, the control device 16 does not execute the adjustment process of step S5. This configuration ensures driving stability when the vehicle 1 is traveling in a high vehicle speed range.

[0041] Furthermore, when the vehicle mode is the fuel economy priority mode, the control device 16 executes the adjustment process when the steering of the vehicle 1 occurs within a predetermined angle range while the vehicle 1 is traveling at a constant speed, and when the vehicle mode is the performance priority mode, the control device 16 executes the adjustment process even if no steering occurs while the vehicle 1 is traveling at a constant speed. With this configuration, in the fuel economy priority mode, the front / rear distribution ratio α c In order to perform the adjustment process, when vehicle 1 is traveling straight, the front / rear distribution ratio α c In addition, in the performance-oriented mode, the vehicle state with improved steering response is maintained even before steering input occurs, and steering response can be further improved when steering input actually occurs.

[0042] Although the description of the embodiment has been completed above, the aspects of the present invention are not limited to this embodiment. For example, the control device 16 may execute the adjustment process (step S5) only when it is determined in step S4 that the steering angle δ of the vehicle 1 is within a predetermined angle range, regardless of the vehicle mode.

[0043] In this embodiment, the ideal distribution ratio α ci The front-rear distribution ratio α c However, the adjustment process is performed by adjusting the front / rear distribution ratio α c For example, the sum "K f l f +K r l r " tends to increase, and the front-to-rear distribution ratio α c Setting this will speed up the yaw rate response.

[0044] In this embodiment, the distribution ratio adjustment control shown in Fig. 3 is executed when the vehicle 1 is being driven. However, with regard to the front / rear distribution ratio between the first braking force applied to the front wheels 2f and the second braking force applied to the rear wheels 2r, which is set so as to satisfy the required braking force required for braking the vehicle 1, the "driving force" in the embodiment may be read as "braking force," and distribution ratio adjustment control similar to that shown in Fig. 3 may be executed. In this case, each braking force may be a regenerative braking force from the front motor 10f or the rear motor 10r, or may include a force from a friction braking device (such as a disc brake) not shown that can apply a friction braking force to each wheel. [Explanation of symbols]

[0045] 1 vehicle 2f Front wheel 2r rear wheel 16 Control device (vehicle control device) α c Front / rear distribution ratio α ci Ideal distribution ratio

Claims

1. A vehicle control device that controls a vehicle so that a first braking / driving force is applied to left and right front wheels and a second braking / driving force is applied to left and right rear wheels at a distribution ratio set so as to satisfy a required braking / driving force required by the vehicle, A vehicle control device characterized in that, when steering of the vehicle occurs within a predetermined angle range that is predetermined as the initial steering angle while the vehicle is traveling at a constant speed, an adjustment process is executed to adjust the distribution ratio so that the yaw rate response to the steering angle tends to be faster.

2. 2. The vehicle control device according to claim 1, wherein the adjustment process sets the distribution ratio to an ideal distribution ratio that minimizes the time constant of the yaw rate response to the steering angle.

3. 3. The vehicle control device according to claim 1, wherein the adjustment process is not executed when the vehicle speed is equal to or higher than a predetermined vehicle speed.

4. As a vehicle mode, a fuel economy priority mode that prioritizes fuel economy over responsiveness to driving operations and a performance priority mode that prioritizes responsiveness to driving operations over fuel economy can be selected. When the vehicle mode is the fuel economy priority mode, the adjustment process is executed when the vehicle is steered within the predetermined angle range while the vehicle is traveling at a constant speed.

3. The vehicle control device according to claim 1, wherein when the vehicle mode is the performance-oriented mode, the adjustment process is executed even if no steering occurs while the vehicle is traveling at a constant speed.

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