Vehicle travel control device

Abstract

Provided is a vehicle travel control device for controlling a slip angular velocity of a vehicle. A travel control section 25 in a main control unit comprises: a slip angular velocity calculation section 60 that calculates a current slip angular velocity β'est of the vehicle on the basis of a yaw rate γ, an actual lateral acceleration RGy, and a vehicle speed V; a slip angular velocity prediction section 61 that estimates a slip angular velocity β'(t+T) after an elapse of a predetermined time from the current slip angular velocity β'est; a target slip angular velocity calculation section that calculates a target slip angular velocity on the basis of a travel state; and a target slip angular velocity calculation section 62 that calculates a target slip angular velocity β'* from a target output torque ReqTrq, a longitudinal acceleration Gx, and a steering angle δ. The travel control section 25 performs feedback control by correcting a travel driving torque or a braking torque so that the slip angular velocity β'(t+T) after the elapse of the predetermined time follows the target slip angular velocity β'*.

Description

Vehicle driving control device

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

[0002] In recent years, various types of vehicle driving control devices have been developed, such as torque distribution control between front and rear wheels in four-wheel drive vehicles, torque vectoring control between left and right wheels, and four-wheel brake control devices. For example, Patent Document 1 proposes a technology that calculates a slip angular velocity, which is the rate of change of a vehicle body slip angle, which is the angle between the orientation of the vehicle body and the vehicle's traveling direction, based on information detected by sensors such as vehicle speed, vehicle lateral acceleration, and yaw rate, and corrects the drive torque of a driving source for driving in accordance with the slip angular velocity, thereby controlling vehicle body slip and improving cornering performance.

[0003] Japanese Patent Application Laid-Open No. 2020-125057

[0004] However, in Patent Document 1, the drive torque is corrected based on the slip angular velocity calculated from the current vehicle speed, lateral acceleration, and yaw rate, so there is a possibility that slip may not be sufficiently suppressed due to a control delay when traveling on a low-friction road such as a snowy road. Furthermore, cruise control devices that perform control based on parameters other than slip angular velocity have been developed for torque distribution control between front and rear wheels, torque vectoring control between left and right wheels, and four-wheel brake control devices in four-wheel drive vehicles. A problem arises in a vehicle equipped with a cruise control device that controls slip angular velocity and another cruise control device that controls based on parameters other than slip angular velocity, whereby the control based on slip angular velocity and the other control affect each other, making it difficult to achieve appropriate control.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a cruise control device that appropriately controls the slip angular velocity to suppress vehicle slip.

[0006] In order to achieve the above object, the vehicle driving control device of the present invention is characterized by comprising: a slip angular velocity calculation unit that calculates a current slip angular velocity of the vehicle based on the vehicle driving state; a slip angular velocity estimation unit that estimates a slip angular velocity after a predetermined time has elapsed from the current slip angular velocity; a target slip angular velocity calculation unit that calculates a target slip angular velocity based on the vehicle driving state; and a slip angular velocity control unit that controls the driving torque or braking torque of the vehicle so that the slip angular velocity after the predetermined time has elapsed follows the target slip angular velocity.

[0007] According to the vehicle driving control device of the present invention, the slip angular velocity after a predetermined time has elapsed is estimated and controlled so that the slip angular velocity after the predetermined time has elapsed follows the target slip angular velocity, thereby making it possible to appropriately control the slip angular velocity so that it does not exceed the target slip angular velocity, thereby suppressing vehicle slip.

[0008] The present invention relates to a driving control device for a vehicle, and more particularly to a driving control system for a vehicle having a driving control device according to the present invention.

[0009] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a schematic diagram of a plug-in hybrid vehicle (PHEV, hereinafter referred to as vehicle 1) equipped with a cruise control device according to the embodiment. Vehicle 1 is a four-wheel drive vehicle that can travel by driving front wheels 3a, 3b with the output of an engine 2, and that is equipped with an electric front motor 4 that drives the front wheels 3a, 3b and an electric rear motor 6 that drives rear wheels 3c, 3d. In the following description, unless there is a particular need to distinguish between them, the front wheels 3a, 3b and the rear wheels 3c, 3d will be referred to as "wheels 3."

[0010] The engine 2 is capable of driving a drive shaft 8 of the front wheels 3 a, 3 b via a front transaxle 7, and is also capable of generating electricity by driving a motor generator 9 via the front transaxle 7. The engine 2 and the front wheels 3 a, 3 b are connected via a clutch 16 disposed within the front transaxle 7. The vehicle 1 is also provided with a fuel tank (not shown) that stores fuel to be supplied to the engine 2.

[0011] The front motor 4 is powered by high-voltage power supplied from a drive battery 11 and a motor generator 9 mounted on the vehicle 1 via a front motor control unit 10, and drives a drive shaft 8 of the front wheels 3 a, 3 b via a front transaxle 7. The rear motor 6 is powered by high-voltage power supplied from the drive battery 11 via a rear motor control unit 12, and drives a drive shaft 14 of the rear wheels 3 c, 3 d via a rear transaxle 13. The power generated by the motor generator 9 can charge the drive battery 11 via the front motor control unit 10, and can also supply power to the front motor 4 and the rear motor 6.

[0012] The drive battery 11 is composed of a secondary battery such as a lithium-ion battery, and has a battery module (not shown) configured by a group of multiple battery cells. The drive battery 11 also has a charge rate detector 11a that detects the state of charge (SOC) of the drive battery 11. The vehicle 1 is also equipped with a charger 18 that can charge the drive battery 11 from an external power source.

[0013] Based on control signals from a main control unit 20 mounted on the vehicle 1, the front motor control unit 10 controls the braking / driving force produced by the front motor 4, i.e., the driving torque and regenerative braking torque of the front motor 4, and also controls the power generation amount and output of the motor generator 9. Based on control signals from the main control unit 20, the rear motor control unit 12 controls the braking / driving force produced by the rear motor 6, i.e., the driving torque and regenerative braking torque of the rear motor 6.

[0014] The engine control unit 22 is a control device for the engine 2, and is configured to include input / output devices, memory devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), a timer, etc. Based on a control signal (required output) from the main control unit 20, the engine control unit 22 controls the fuel injection amount, fuel injection timing, intake amount, etc. of the engine 2, thereby controlling the drive of the engine 2.

[0015] The main control unit 20 is a control device for performing overall control of the vehicle 1, and is configured to include input / output devices, memory devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), a timer, etc. The front motor control unit 10, rear motor control unit 12, and engine control unit 22 are connected to the input side of the main control unit 20, and detection and operation information from these devices is input. On the other hand, the front motor control unit 10, rear motor control unit 12, engine control unit 22, and clutch 16 of the front transaxle 7 are connected to the output side of the main control unit 20.

[0016] The main control unit 20 is equipped with a driving control unit 25 that calculates the vehicle required output power required to drive the vehicle 1 based on various detected amounts such as the accelerator operation information level of the vehicle 1 and various operation information, and sends control signals to the engine control unit 22, the front motor control unit 10, and the rear motor control unit 12. The main control unit 20 controls switching of driving modes (EV mode, series mode, parallel mode), the outputs of the engine 2, the front motor 4, and the rear motor 6, the generated power and output of the motor generator 9, and the engagement and disengagement of the clutch 16 in the front transaxle 7.

[0017] Brake devices 30a, 30b, 30c, and 30d that apply braking torque are provided on each wheel 3 of the vehicle 1. The front wheel brake devices 30a and 30b are controlled by a front brake control unit 31, and the rear wheel brake devices 30c and 30d are controlled by a rear brake control unit 32, so that the braking torque for each wheel 3 can be controlled independently.

[0018] The front brake control unit 31 and the rear brake control unit 32 are connected to the main control unit 20 so as to be able to communicate with each other. The front brake control unit 31 may be connected to the main control unit 20 so as to be able to communicate with each other via the front motor control unit 10, and the rear brake control unit 32 may be connected to the main control unit 20 so as to be able to communicate with each other via the rear motor control unit 12. The front brake control unit 31 and the rear brake control unit 32 control the operation of each of the brake devices 30a, 30b, 30c, and 30d based on a brake pedal operation signal from a brake pedal sensor (not shown) or the like.

[0019] The front motor control unit 10, rear motor control unit 12, front brake control unit 31, and rear brake control unit 32 are each configured to include input / output devices, memory devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), a timer, etc. These control units have faster processing speeds than the main control unit 20.

[0020] The vehicle 1 is equipped with a steering angle sensor 40 that detects the steering angle, a wheel speed sensor 41 that detects the rotational speed of each wheel, a yaw rate sensor 45 that detects the yaw rate of the vehicle body, a lateral acceleration sensor 46 that detects the acceleration of the vehicle body in the left-right direction, a vehicle speed sensor 47 that detects the vehicle traveling speed, and a longitudinal acceleration sensor 48 that detects the acceleration of the vehicle body in the front-rear direction. The detected values ​​of each of these sensors are sequentially input to the main control unit 20.

[0021] The cruise control unit 25 also has a yaw control function (yaw control device) that controls the yaw rate based on the detection values ​​of various sensors, such as the yaw rate sensor 45. Furthermore, the cruise control unit 25 also has a function of controlling the slip angular velocity of the vehicle. FIG. 2 is a block diagram showing a schematic configuration of the cruise control unit 25 of this embodiment. First, the configuration of the cruise control unit 25 in the main control unit 20 will be described. As shown in FIG. 2, the cruise control unit 25 includes a vehicle state estimation unit 51, a lateral G proportional FF control unit 52, a yaw inertia compensation FF control unit 53, a PD control unit 54, a slip angular velocity calculation unit 60, a slip angular velocity prediction unit 61 (slip angular velocity estimation unit), a target slip angular velocity calculation unit 62, a dead zone processing unit 63, a D-P control unit 64, a moment distribution control unit 70, a front / rear distribution FB control unit 71, a rear axle torque limiting unit 72, and a brake moment addition control unit 73.

[0022] Vehicle state estimation unit 51 receives steering angle δ from steering angle sensor 40, wheel speed Wspd of each wheel from wheel speed sensor 41, and actual yaw rate γ from yaw rate sensor 45, and outputs estimated lateral acceleration Gy and corrected yaw rate γ*. Lateral G proportional FF control unit 52 receives estimated lateral acceleration Gy from vehicle state estimation unit 51, and outputs an FF (feedforward) control correction amount proportional to the estimated lateral acceleration Gy.

[0023] The yaw inertia compensation FF control unit 53 receives an integrated value of the corrected yaw rate γ* output from the vehicle state estimation unit 51 and outputs an FF control correction amount for yaw inertia compensation. The PD control unit 54 compares the corrected yaw rate γ* output from the vehicle state estimation unit 51 with the actual yaw rate γ input from the yaw rate sensor 45 and outputs an FB (feedback) control correction amount for the yaw rate in the PD feedback control.

[0024] A slip angular velocity calculation unit 60 inputs the actual yaw rate γ from the yaw rate sensor 45, the actual lateral acceleration RGy input from the lateral acceleration sensor 46, and the vehicle speed V from the vehicle speed sensor 47, and calculates the current slip angular velocity β'est using the following (Equation 1): β'est = Gy / V - γ (Equation 1) A slip angular velocity prediction unit 61 estimates the slip angular velocity β'(t+T) after a predetermined time T seconds (after a predetermined time has elapsed). The slip angular velocity β'(t+T) after the predetermined time T seconds is calculated as β'est using the following (Equation 4) obtained by Taylor expansion of the equation of motion for lateral movement (Equation 2) and the equation of motion in the yaw direction (Equation 3).

[0025]

[0026]

[0027]

[0028] In the above formulas (2), (3), and (4), the symbols are as follows:

[0029]

[0030] Target slip angular velocity calculation unit 62 receives target output torque ReqTrq, longitudinal acceleration Gx from longitudinal acceleration sensor 48, and steering angle δ from steering angle sensor 40 to calculate target slip angular velocity β'*. D-P control unit 64 receives a comparison result (difference) between slip angular velocity β'(t+T) calculated by slip angular velocity prediction unit 61 and target slip angular velocity β'* calculated by target slip angular velocity calculation unit 62, and a value obtained by dead-band processing in dead-band processing unit 63. D-P control unit 64 outputs an FB control correction amount for the slip angle in derivative-leading P feedback control. For example, if slip angular velocity β'(t+T) calculated by slip angular velocity prediction unit 61 is equal to or less than the target slip angular velocity β'* calculated by target slip angular velocity calculation unit 62, dead-band processing unit 63 sets the output from dead-band processing unit 63 to 0, and feedback control in D-P control unit 64 is not performed.

[0031] The moment distribution control unit 70 performs feedforward control of the torque distribution between the front and rear axles and the torque limit of the rear axle in the yaw control device. The moment distribution control unit 70 adds and inputs the FF control amounts output from the lateral G proportional FF control unit 52, the yaw inertia compensation FF control unit 53, the PD control unit 54, and the DP control unit, and calculates the torque distribution between the front and rear axles and the torque limit amount of the rear axle, i.e., the torque limit amount of the rear motor 6, on the premise that the vehicle does not feel like it is decelerating.

[0032] The front / rear distribution FB control unit 71 performs feedback control of torque distribution between the front and rear axles in the yaw control device. The rear axle torque limiting unit 72 limits the torque on the rear axles in the yaw control device, taking into account the differential device (front LSD) between the left and right front wheels. The brake moment addition control unit 73 controls the amount of braking (amount of braking) of the brake device in the yaw control device.

[0033] The front / rear distribution FB control unit 71, the rear axle torque limiting unit 72, and the brake moment addition control unit 73 add the PD control amount output from 54 and the PD control amount output from 64 to set each control amount. In this embodiment, the feedforward control amounts in the lateral G proportional FF control unit 52 and the yaw inertia compensation FF control unit 53 are multiplied by a control gain corresponding to the slip angular velocity β'est input from the slip angular velocity calculation unit 60. For example, since the control gain is corrected to be smaller as the slip angular velocity β'est increases, control toward the turning promotion side is suppressed in advance, and a spin of the vehicle 1 is suppressed.

[0034] Furthermore, the feedback control amount in the PD control unit 54 is multiplied by a control gain corresponding to the slip angular velocity β'est input from the slip angular velocity calculation unit 60. For example, the control gain is corrected to decrease as the slip angular velocity β'est increases, so that control toward the turning promotion side is promptly suppressed when the vehicle spins. Furthermore, in this embodiment, the slip angular velocity prediction unit 61 estimates the slip angular velocity β'(t+T) T seconds later, and the D-P control unit 64 performs feedback control so that the slip angular velocity β'(t+T) follows the target slip angular velocity β'* calculated in the target slip angular velocity calculation unit 62.

[0035] Furthermore, when feedback control is performed in the D-P control unit 64, an upper limit is set for the target value (target slip angular velocity β'*) and control is performed so that the slip angular velocity β'(t+T) does not exceed the upper limit. Also, an upper limit is set for the target value (target slip angular velocity β'*) in the dead band processing unit 63, and if the slip angular velocity β'(t+T) is equal to or less than the target slip angular velocity β'*, the D-P control unit 64 does not perform feedback control.

[0036] As described above, the traveling control unit 25 calculates each control correction amount in the lateral G proportional FF control unit 52, the yaw inertia compensation FF control unit 53, and the PD control unit 54 based on the vehicle state (steering angle δ, each wheel speed Wspd, and actual yaw rate γ). In this embodiment, however, the slip angular velocity β' is further used to correct the control gains in the lateral G proportional FF control unit 52, the yaw inertia compensation FF control unit 53, and the PD control unit 54, so that the moment distribution control unit 70 performs moment distribution taking the slip angular velocity β' into consideration.

[0037] Furthermore, in this embodiment, the slip angular velocity β'(t+T) after T seconds is estimated, and the D-P control unit 64 performs feedback control using the slip angular velocity β'(t+T) after T seconds. The slip angular velocity β'(t+T) after T seconds is then used to control the torque distribution between the front and rear axles in the front / rear distribution FB control unit 71, the rear axle torque limiting control in the rear axle torque limiting unit 72, and the brake amount control in the brake moment addition control unit 73, so that the slip angular velocity after T seconds is controlled to follow the target slip angular velocity β'*. This makes it possible to prevent the slip angular velocity β' from deviating significantly from the target slip angular velocity β'*, and to prevent the vehicle 1 from spinning out even if the driver steers roughly, for example.

[0038] FIG. 3 is a time chart showing an example of the transition of slip angular velocity β' during cornering of the vehicle. In FIG. 3, the solid line shows the transition of slip angular velocity β' when feedback control is not performed by the D-P control unit 64, the dashed line shows the case when feedback control is performed but no upper limit is set, and the dashed-dotted line shows the case when an upper limit is set. In a situation where the slip angular velocity increases during cornering as shown by the solid line in FIG. 3, by performing feedback control by the D-P control unit 64, the slip angular velocity decreases due to feedback control, for example, from the point when the slip angular velocity β'(t+T) after T seconds exceeds the target slip angular velocity β'*, as shown by the dashed line. In this embodiment, the slip angular velocity is controlled so as not to exceed the upper limit slip angular velocity β'*+U, as shown by the dashed-dotted line.

[0039] When the slip angular velocity β'(t+T) after T seconds is between the target slip angular velocity β'* and the upper limit β'*+U, the coefficient ksp is set to 0 when the slip angular velocity β' is the target slip angular velocity β'*, and set to 1 when the slip angular velocity β' is the upper limit slip angular velocity β'*+U, so that the slip angular velocity β' is continuously changed between these values. This controls the slip angular velocity β' so that it does not exceed the upper limit slip angular velocity β'*+U, and smoothly changes the slip angular velocity β' during this control, thereby reducing any discomfort while driving.

[0040] Although the description of the embodiment has been completed, aspects of the present invention are not limited to this embodiment. For example, the details of the control in this embodiment may be changed as appropriate. Furthermore, although the vehicle 1 in the above embodiment is a plug-in hybrid vehicle (PHEV) equipped with an engine 2 and capable of external charging and external power supply, the present invention can also be applied to hybrid vehicles (HEVs) and electric vehicles (EVs). The present invention can also be applied to vehicles in which the driving or braking of each of the four wheels can be electrically controlled independently.

[0041] 1 Vehicle 25 Travel control unit (travel control device) 60 Slip angular velocity calculation unit 61 Slip angular velocity prediction unit (slip angular velocity estimation unit) 62 Target slip angular velocity calculation unit 52 Lateral G proportional FF control unit (turning feedforward control unit) 53 Yaw inertia compensation FF control unit (turning feedforward control unit) 54 PD control unit (turning feedback control unit) 64 D-P control unit (slip angular velocity control unit) 73 Brake moment addition control unit β'est Current slip angular velocity β'(t+T) Slip angular velocity after a predetermined time has elapsed β'* Target slip angular velocity

Claims

1. A vehicle driving control device comprising: a slip angular velocity calculation unit that calculates a current slip angular velocity of a vehicle based on a vehicle driving state; a slip angular velocity estimation unit that estimates a slip angular velocity after a predetermined time has elapsed from the current slip angular velocity; a target slip angular velocity calculation unit that calculates a target slip angular velocity based on the vehicle driving state; and a slip angular velocity control unit that controls a driving torque or a braking torque of the vehicle so that the slip angular velocity after the predetermined time has elapsed follows the target slip angular velocity.

2. The vehicle driving control device according to claim 1, characterized in that the driving control device includes a turning feedforward control unit that feedforward controls the lateral acceleration or yaw rate of the vehicle based on the driving state when the vehicle is turning, and the slip angular velocity control unit limits the gain in the turning feedforward control unit based on the slip angular velocity calculated in the slip angular velocity calculation unit to reduce the slip angular velocity.

3. The vehicle driving control device according to claim 1, characterized in that the driving control device includes a turning feedback control unit that feedback controls the yaw rate of the vehicle based on the driving state during turning, and the slip angular velocity control unit limits the gain in the turning feedback control unit based on the slip angular velocity calculated in the slip angular velocity calculation unit to reduce the slip angular velocity.

4. The vehicle driving control device according to claim 3, characterized in that the driving control device comprises a torque distribution control unit that distributes torque between the front and rear axles of the vehicle, and a rear axle torque limiting unit that limits torque on the rear axle, and the slip angular velocity control unit corrects the torque distribution between the front and rear axles of the vehicle and limits torque on the rear axle by limiting the gain in the turning feedback control unit.

5. The vehicle driving control device according to claim 3, characterized in that the driving control device includes a brake moment application control unit that controls the braking forces of the brake devices on the front, rear, left, and right wheels of the vehicle to apply a moment to the vehicle, and the slip angular velocity control unit controls the application of the moment by controlling the brake devices by limiting the gain in the turning feedback control unit.