JP5266707B2 - Braking control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a braking control device capable of obtaining desired vehicle behavior even if compliance steer is varied by variation of relationship of regenerative braking force and friction braking force. <P>SOLUTION: The braking control device controls vehicle behavior based on the relationship of the regenerative braking force and the friction braking force. For example, as shown in Fig.1, A brake controller 9 inputs sensor information from a wheel speed sensor 19 for detecting respective wheel speed of four wheels and a brake stroke sensor 20, and for example, performs regenerative cooperation brake control based on regenerative cooperation control instruction from an integrated controller 10 so as to compensate the degree of lack by mechanical braking force (braking force by friction brake) when it lacks relative to requirement braking force determined from a brake stroke BS only by the regenerative braking force at brake stepping braking. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a braking control device that generates a regenerative braking force and a friction braking force.

As a device for generating a regenerative braking force and a friction braking force in a hybrid vehicle, a technique disclosed in Patent Document 1 is disclosed. In this document, a target braking force generated in each wheel is calculated, and control is performed so that a resultant force of the regenerative braking force and the friction braking force becomes the target braking force.
JP 9-216554 A

  However, even when the same braking force is applied to the friction braking force and the regenerative braking force, the amount of compliance steer generated is different, and a desired behavior (yaw response gain) may not be obtained as a vehicle behavior. there were.

  The present invention has been made paying attention to the above problem, and provides a braking control device capable of obtaining a desired vehicle behavior even when the compliance steer changes due to a change in the relationship between the regenerative braking force and the friction braking force. The purpose is to provide.

To achieve the above object, the brake control apparatus of the present invention, it was decided to control the vehicle behavior based on the relationship with the regenerative braking force and the frictional braking force.

  Therefore, even if the compliance steer changes due to a change in the relationship between the friction braking force and the regenerative braking force, the desired vehicle behavior can be controlled.

  Hereinafter, the best mode for realizing the braking control device of the present invention will be described based on Example 1 shown in the drawings.

  First, the drive system configuration of the hybrid vehicle will be described. FIG. 1 is an overall system diagram showing a hybrid vehicle by rear wheel drive to which the engine start control device of the first embodiment is applied. As shown in FIG. 1, the drive system of the hybrid vehicle in the first embodiment includes an engine E, a first clutch CL1, a motor generator MG, a second clutch CL2, an automatic transmission AT, a propeller shaft PS, It has a differential mechanism DF, a left drive shaft DSL, a right drive shaft DSR, a left rear wheel RL (drive wheel), and a right rear wheel RR (drive wheel). FL is the front left wheel and FR is the front right wheel.

  The engine E is, for example, a gasoline engine, and the valve opening degree of the throttle valve and the like are controlled based on a control command from the engine controller 1 described later. The engine output shaft is provided with a flywheel FW.

  The first clutch CL1 is a clutch interposed between the engine E and the motor generator MG, and the control created by the first clutch hydraulic unit 6 based on a control command from the first clutch controller 5 described later. Fastening / release including slip fastening is controlled by hydraulic pressure.

  The motor generator MG is a synchronous motor generator in which a permanent magnet is embedded in a rotor and a stator coil is wound around a stator, and the three-phase AC generated by the inverter 3 is generated based on a control command from a motor controller 2 described later. It is controlled by applying. The motor generator MG can operate as an electric motor that is driven to rotate by receiving power supplied from the battery 4 (hereinafter, this state is referred to as “power running”), or when the rotor is rotated by an external force. Can function as a generator that generates electromotive force at both ends of the stator coil to charge the battery 4 (hereinafter, this operation state is referred to as “regeneration”). Note that the rotor of the motor generator MG is connected to the input shaft of the automatic transmission AT via a damper (not shown).

  The second clutch CL2 is a clutch interposed between the motor generator MG and the left and right rear wheels RL and RR, and is generated by the second clutch hydraulic unit 8 based on a control command from the AT controller 7 described later. The fastening / release including slip fastening is controlled by the control hydraulic pressure.

  The automatic transmission AT is a transmission that automatically switches the stepped gear ratio such as 5 forward speeds, 1 reverse speed, etc. according to the vehicle speed, accelerator opening, etc., and the second clutch CL2 is newly added as a dedicated clutch However, some frictional engagement elements are used among a plurality of frictional engagement elements that are engaged at each gear stage of the automatic transmission AT. Details will be described later.

  The output shaft of the automatic transmission AT is connected to the left and right rear wheels RL and RR via a propeller shaft PS, a differential DF, a left drive shaft DSL, and a right drive shaft DSR as vehicle drive shafts. The first clutch CL1 and the second clutch CL2 are, for example, wet multi-plate clutches that can continuously control the oil flow rate and hydraulic pressure with a proportional solenoid.

  This hybrid drive system has three travel modes according to the engaged / released state of the first clutch CL1. The first travel mode is an electric vehicle travel mode (hereinafter abbreviated as “EV travel mode”) as a motor use travel mode that travels using only the power of the motor generator MG as a power source with the first clutch CL1 opened. It is. The second travel mode is an engine use travel mode (hereinafter abbreviated as “HEV travel mode”) in which the first clutch CL1 is engaged and the engine E is included in the power source. The third travel mode is an abbreviated engine use slip travel mode (hereinafter referred to as “WSC travel mode”) in which the second clutch CL2 is slip-controlled while the first clutch CL1 is engaged and the engine E is included in the power source. ).

  The “HEV travel mode” has three travel modes of “engine travel mode”, “motor assist travel mode”, and “travel power generation mode”.

  In the “engine running mode”, the drive wheels are moved using only the engine E as a power source. In the “motor assist travel mode”, the drive wheels are moved by using the engine E and the motor generator MG as power sources. The “running power generation mode” causes the motor generator MG to function as a generator at the same time as the drive wheels RR and RL are moved using the engine E as a power source.

  During constant speed operation or acceleration operation, motor generator MG is operated as a generator using the power of engine E. Further, during deceleration operation, the braking energy is regenerated and generated by the motor generator MG and used for charging the battery 4.

  Further, as a further mode, there is a power generation mode in which the motor generator MG is operated as a generator using the power of the engine E when the vehicle is stopped.

  Next, the control system of the hybrid vehicle will be described. As shown in FIG. 1, the hybrid vehicle control system according to the first embodiment includes an engine controller 1, a motor controller 2, an inverter 3, a battery 4, a first clutch controller 5, and a first clutch hydraulic unit 6. The AT controller 7, the second clutch hydraulic unit 8, the brake controller 9, and the integrated controller 10 are configured. The engine controller 1, the motor controller 2, the first clutch controller 5, the AT controller 7, the brake controller 9, and the integrated controller 10 are connected via a CAN communication line 11 that can exchange information with each other. ing.

  The engine controller 1 inputs the engine speed information from the engine speed sensor 12, and controls the engine operating point (Ne: engine speed, Te: engine torque) according to the target engine torque command from the integrated controller 10, etc. For example, to a throttle valve actuator (not shown). Information such as the engine speed Ne is supplied to the integrated controller 10 via the CAN communication line 11.

  The motor controller 2 inputs information from the resolver 13 that detects the rotor rotational position of the motor generator MG, and according to a target motor generator torque command from the integrated controller 10 or the like, the motor operating point (Nm: motor generator) of the motor generator MG. A command for controlling the rotation speed (Tm: motor generator torque) is output to the inverter 3. The motor controller 2 monitors the battery SOC indicating the state of charge of the battery 4. The battery SOC information is used as control information for the motor generator MG and is supplied to the integrated controller 10 via the CAN communication line 11. Is done.

  The first clutch controller 5 inputs sensor information from the first clutch hydraulic pressure sensor 14 and the first clutch stroke sensor 15, and according to the first clutch control command from the integrated controller 10, the first clutch CL1 is engaged / released. A command to control is output to the first clutch hydraulic unit 6. Information on the first clutch stroke C1S is supplied to the integrated controller 10 via the CAN communication line 11.

  The AT controller 7 inputs sensor information from the accelerator switch 7a that outputs a signal corresponding to the position of the accelerator opening sensor 16, the vehicle speed sensor 17, the second clutch hydraulic pressure sensor 18, and the shift lever operated by the driver. In response to the second clutch control command from the controller 10, a command for controlling the engagement / disengagement of the second clutch CL2 is output to the second clutch hydraulic unit 8 in the AT hydraulic control valve. Information on the accelerator pedal opening APO, the vehicle speed VSP, and the inhibitor switch 7 a is supplied to the integrated controller 10 via the CAN communication line 11.

  The brake controller 9 inputs sensor information from a wheel speed sensor 19 and a brake stroke sensor 20 that detect the wheel speeds of the four wheels. For example, when the brake is depressed, braking is performed with respect to the required braking force obtained from the brake stroke BS. When the braking force alone is insufficient, the regenerative cooperative brake control is performed based on the regenerative cooperative control command from the integrated controller 10 so that the shortage is supplemented by the mechanical braking force (braking force by the friction brake). More specifically, the front and rear wheel braking force distribution is obtained with respect to the required braking force, and the rear wheel braking force is determined based on the battery SOC (State of Charge) and the regenerative limit torque, and the regenerative braking force and the friction braking force. To decide.

  The mechanical braking force of the first embodiment is such that the braking force is controlled by hydraulic control by the brake-by-wire unit, and includes a pump as a hydraulic pressure source and various solenoid valves, and each wheel can freely and independently A pressure braking force can be generated. Not only the hydraulic pressure but also an EMB (Electric Motor Brake) system that controls the pressing force of the brake pad by the electric motor may be used. Further, an electric variable booster system capable of changing the boost ratio may be used.

  The integrated controller 10 manages the energy consumption of the entire vehicle and has a function for running the vehicle with the highest efficiency. The integrated controller 10 detects the motor rotational speed Nm, and the second clutch output rotational speed N2out. A second clutch output speed sensor 22 for detecting the second clutch torque, a second clutch torque sensor 23 for detecting the second clutch torque TCL2, a brake hydraulic pressure sensor 24, and a temperature sensor 10a for detecting the temperature of the second clutch CL2. And information obtained via the CAN communication line 11 are input.

  The integrated controller 10 also controls the operation of the engine E according to the control command to the engine controller 1, the operation control of the motor generator MG based on the control command to the motor controller 2, and the first control command to the first clutch controller 5. Engagement / release control of the clutch CL1 and engagement / release control of the second clutch CL2 by a control command to the AT controller 7 are performed.

[4-wheel active steering system]
FIG. 2 is a system configuration diagram of the four-wheel active steering system mounted on the vehicle of the first embodiment. A steering shaft 32 that is rotatably supported on the vehicle body side and connected to the steering wheel 31 is connected to the steering wheel 31 that is steered by the driver.

  The steering shaft 32 is provided with a steering angle sensor 38 that detects the steering angle θd of the driver, and outputs the steering angle θd to the control unit 100. Further, a variable steering angle actuator 33 for changing the steering angle ratio (ratio of the actual front wheel turning angle to the driver's steering angle θd) is provided on the front wheels FF, FR side of the steering angle sensor 38. This variable steering angle actuator 33 is provided with a front wheel motor 33a, and the steering angle ratio is changed by adding or subtracting the front wheel motor rotation angle θmf with respect to the steering angle θd.

  The front wheel motor 33 a is provided with an encoder 40, and the rotation angle θmf of the front wheel motor 33 a is output to the control unit 100. A pinion 34 is provided on the front wheels FF, FR side of the variable steering angle actuator 33, and a rack shaft 35 is moved to the left and right in the axial direction by a so-called rack and pinion mechanism to steer the front wheels FF, FR.

  The rear wheels RR and RL are provided with a rear wheel steering actuator 36 for providing a rear wheel steering angle. The rear wheel steering actuator 36 is provided with a rear wheel motor 36a that gives a steering angle to the rear wheels RR and RL. The rear wheel motor 36 a is provided with an encoder 41 that detects a rear wheel motor rotation angle θmr corresponding to the rear wheel steering angle, and the rotation angle θmr of the rear wheel motor 36 a is output to the control unit 100. A vehicle speed sensor 17 is provided, and the detected vehicle speed VSP is output to the control unit 100.

[Control unit control configuration]
FIG. 3 is a block diagram showing the configuration of the control unit 100. The control unit 100 includes a main controller 100a, a front wheel steering controller 100b, and a rear wheel steering controller 100c.

  In the main controller 100a, a target value generation unit 110 that generates a target front wheel steering angle θ * p_ref and a target rear wheel steering angle δ * ref based on the detected values θd and VSP of the steering angle sensor 38 and the vehicle speed sensor 17, and From the target value correction unit 120 that corrects each target value based on the regenerative braking force and friction braking force from the integrated controller 10 and outputs the corrected target front wheel steering angle θ * p and the corrected target rear wheel steering angle δ *. It is configured.

  The front wheel steering controller 100b outputs a steering angle command value to the front wheel motor 33a as a front wheel steering actuator based on the corrected target front wheel steering angle θ * p output from the target value correction unit 120, and the front wheel motor 33a. Execute servo control with.

  The rear wheel steering controller 100c outputs a steering angle command value to the rear wheel motor 36a as a rear wheel steering actuator based on the corrected target rear wheel steering angle δ * output from the target value correction unit 120, and the rear wheel motor. Servo control is executed with 36a.

[Control contents of target value generator]
Next, the control content of the target value generation unit 110 will be described.
(Front wheel control)
First, the target value of the proportional component is obtained from the steering angle θd of the driver and the front wheel proportional gain KPf (VSP) depending on the vehicle speed VSP shown in FIG. Here, when the vehicle speed VSP is low, the steering angle ratio is set large (quickly) so that a large steering angle can be obtained with a small steering angle θd of the driver. On the other hand, when the vehicle speed VSP is high, the steering angle ratio is set to be small (slow) in consideration of stability.

  Next, the target value of the differential component is obtained from the steering angular velocity dθd / dt obtained by differentiating the steering angle θd and the front wheel differential gain KDf depending on the vehicle speed VSP shown in FIG. This differential steering can generally improve the yaw rate response of the vehicle.

These proportional and differential components are added, and the front wheel target steering angle θ * p_ref is calculated by the following formula θ * p_ref = KPf × θd + KDf × dθd / dt
It is represented by In this case, the front wheel motor rotation angle command value θmf * is expressed by the following equation: θ * mf = θ * p_ref−θd
It is represented by

(Rear wheel control)
Similar to the front wheel control, the rear wheel steering angle target value is obtained using the rear wheel proportional gain KPr (VSP) depending on the vehicle speed VSP shown in FIG. 6 and the rear wheel differential gain KDr depending on the vehicle speed VSP shown in FIG. δ * ref is the following formula δ * ref = KPr × θd + KDr × dθd / dt
It is represented by

(Servo control)
The deviation e between the actual steering angle θ of the front wheels and the corrected target front wheel steering angle θ * is
e = θ-θ *
Is required.
The front wheel control command value I _theta, and the deviation e, a proportional gain P and, derivative gain D and the following formula I and a integral gain _{I θ = P × e + D} × de / dt + I × ∫edt
Is required. The proportional gain P, differential gain D, and integral gain I are tuning constants. Similar servo control is executed for the rear wheels.

[Details of target value correction unit]
Here, the necessity of correcting the target values of the front and rear wheels set by the logical configuration will be described. FIG. 8 is a schematic diagram showing the logic of compliance steer by tire front / rear input during braking. Compliance steer is an input applied to the tire contact point, and refers to the change in toe angle caused by the bending of each part, such as the bush at the suspension link attachment point, due to the lateral force and braking force generated during turning of the vehicle. Affect.

  Because of its mission, the suspension is attached to each link attachment point via a rubber bush. Otherwise, vibrations cannot be absorbed and riding comfort cannot be ensured, and the input to the suspension is large, leading to deterioration in durability. However, being attached via rubber means that when a force is applied, the portion is deformed and the arrangement of the suspension is changed. The change in toe angle caused by this is called compliance steer and occurs not only due to lateral force but also against longitudinal force due to braking or driving.

  FIG. 8A is a schematic diagram showing a state of compliance steer due to the front-rear tire input at the time of braking by friction braking, that is, braking by friction braking force. The tire, the axle, and the suspension link that are mechanically connected to the tire front-rear input generate a reaction force as a unit. As a result, the suspension link bush with low rigidity is bent, and the tire, axle, and suspension link are deformed. In general, a vehicle is designed to obtain a toe-in state from the viewpoint of ensuring stability during braking.

  FIG. 8B is a schematic diagram showing elements of compliance steer due to front and rear tire inputs during regenerative braking, that is, braking by regenerative braking force. The tire front / rear input is transmitted to the drive shaft because the tire, axle and suspension are not integrated. That is, since the tire front-rear input is not directly transmitted to the axle, it can be seen that the displacement amount of the suspension link connected to the axle is small. That is, even if the braking force is the same, the tire cannot obtain a toe-in state when the regenerative braking force is applied.

  In the first embodiment, since the engine E and the motor generator MG are connected to the rear wheels FR and FL, the toe-in state of the rear wheels differs between when the friction braking force is applied and when the regenerative braking force is applied. I understand. That is, a difference occurs in the yaw motion characteristics of the vehicle between turning braking to which regenerative braking force is applied and turning braking to which friction braking force is applied.

  In the case of a vehicle that applies a regenerative braking force to the rear wheels, it is less stable if the regenerative braking force is applied. This is because, as shown in FIG. 8 (b), the toe-in state cannot be obtained at the rear wheel with the regenerative braking force, and the cornering force of the rear wheel is lowered due to insufficient rear wheel slip angle during turning.

  Next, the reason why the distribution ratio between the regenerative braking force and the friction braking force changes will be described. In the hybrid vehicle, the energy transmitted from the wheels is recovered as electric energy by the regenerative operation of the motor generator MG. The regenerative limit torque of motor generator MG is defined by the rotational speed of motor generator MG. In general, the regenerative limit torque is small at high rotations, and the regenerative limit torque is large at low rotations. In some cases, the regenerative limit torque is reduced to prevent a reduction in efficiency at extremely low vehicle speeds.

  Since motor generator MG is rotated by driving wheels, the rotational speed of motor generator MG is defined by the vehicle speed and the gear ratio of automatic transmission AT interposed between motor generator MG and the driving wheels. In the automatic transmission AT, if the accelerator opening is 0, generally, the gear position is automatically determined only by the vehicle speed.

  Based on these facts, let us consider a situation where braking is performed with a constant braking force applied. As the vehicle speed decreases, the rotational speed of the motor generator MG changes due to a change in the vehicle speed and a downshift of the automatic transmission AT. This change also changes the regenerative limit torque. On the integrated controller 10 side, in order to generate the regenerative torque as much as possible when the battery has a margin, the regenerative braking force component of the constant braking force increases as the regenerative limit torque increases. The component of the friction braking force is reduced. In particular, since the rotational speed of the motor generator MG changes stepwise during gear shifting, the regenerative braking force component also changes stepwise. By the way, when a continuously variable transmission is installed, a change in the rotational speed due to a change in the gear ratio occurs even if there is no stepwise change.

  That is, in the case of a system in which the rear wheels are drive wheels as in the first embodiment, the regenerative braking force varies due to the vehicle speed and the downshift of the automatic transmission AT during braking, so the toe-in state of the rear wheels also varies. It becomes.

  Taking the situation of steering from straight braking, when the switching control is performed so that the regenerative braking force is gradually generated from the rear toe-in state by the friction braking force, the state changes to the rear toe-out. The steering response at this time has a problem that the yaw response gain becomes high.

  Further, in the vehicle of the first embodiment, when the transition is made from the high vehicle speed region to the low vehicle speed region, the variable steering angle actuator 33 is controlled to quick characteristics. At this time, for example, when turning braking in a high vehicle speed region, if the vehicle speed decreases due to braking, the target front wheel steering angle θ * p_ref increases even if the driver fixes the steering wheel 31, for example. Alternatively, the target rear wheel steering angle δ * ref may be switched from in-phase control to reverse-phase control, which may increase the yaw rate. Since this is different from the driver's intention, at the time of braking, the gain (proportional gain, differential gain) when calculating the target values of the front and rear wheels is fixed to prevent the yaw rate from increasing excessively. .

  However, as described above, if the target front wheel steering angle θ * p_ref is only fixed during braking, the toe-in state changes when the regenerative braking force and friction braking force on the rear wheel side change. There is a problem that the vehicle behavior (particularly unintended increase in yaw rate) is caused.

  Therefore, in the first embodiment, as described above, the effect of changes in the regenerative braking force and the friction braking force on the vehicle behavior is taken into account, and when the regenerative braking force and the friction braking force change, an actuator capable of controlling the vehicle behavior. On the other hand, the vehicle behavior is controlled in a stable direction.

FIG. 9 is a flowchart showing the control content of the target value correction unit 120.
In step S1, it is determined whether or not braking is in progress. If the brake is being applied, the process proceeds to step S2. If not, the process proceeds to step S8. Note that whether or not braking is in progress may be determined, for example, when braking is performed by a predetermined value or more based on stroke information from the brake stroke sensor 20.

In step S2, the braking flag F is set to 1.
In step S3, it is determined whether or not the brake flag F has changed from 0 to 1. If changed, the process proceeds to step S4, and otherwise, the process proceeds to step S5.

In step S4, each gain (KPf, KPr, KDf, KDr) is fixed to a gain corresponding to the vehicle speed at this time.
In step S5, a fixed gain target value (calculated for both front and rear wheels) is generated based on each fixed gain. A specific calculation method is the same as that of the above-described target value generation unit 110, and thus description thereof is omitted.

  In step S6, a correction amount is calculated based on the regenerative braking force and the friction braking force. The details of this calculation will be described later.

  In step S7, a corrected target front and rear wheel steering angle target value is output based on the fixed gain target value calculated in step S5 and the correction amount calculated in step S6.

In step S8, since it is determined in step S1 that braking is not being performed, the braking flag F is set to 0 and each fixed gain is reset.
In step S9, the generation value of the target value generation unit 110 is output as a corrected target front and rear wheel steering angle.

  The operation based on the flowchart will be described. First, it is determined whether or not braking is being performed. When the brake is not being performed, the toe-in state of the drive wheels does not change, and servo control is executed using the generated value of the target value generating unit 110.

  On the other hand, during braking, the vehicle speed decreases, so there is a risk of a quick tendency as the front and rear wheel steering angle control. Therefore, during braking, the gains (KPf, KPr, KDf, KDr) corresponding to the current vehicle speed are fixed for the time being to prevent the yaw rate from increasing due to the gain change.

  Next, since the gain is fixed during braking, a target value must be generated based on the fixed gain. Therefore, a fixed gain target value is generated based on the fixed gain. Specifically, the target front wheel steering angle and the target rear wheel steering angle are calculated in the same manner as the target value generation unit 110 described above, based on the gain at the time when braking is started.

Next, the regenerative braking force and the friction braking force are read from the integrated controller 10 and the correction amount is calculated. Here, the correction amount calculation based on the regenerative braking force and the friction braking force will be described. Here, the correspondence between the braking force and the toe change amounts S0 to S4 is defined. Each compliance coefficient is a coefficient obtained by experiments or the like, and associates the braking force with the toe angle change amount.
S1: Current rear axle regenerative braking force x WC compliance coefficient (change in toe angle when regenerative braking force is applied)
S2: Current rear axle friction braking force x contact point compliance coefficient (change in toe angle when friction braking force is applied)
S0: Rear axle total braking force x contact point compliance coefficient (change in toe angle when friction braking force is applied)
Then,
The toe angle change amount S4 due to the current braking force is
S4 = S1 + S2
It becomes. Therefore, the toe angle change amount S3 generated by generating the regenerative braking force is
S3 = S0−S4
It is represented by

  FIG. 10 is a map showing the relationship between the toe angle change amount S3 and the yaw response gain change amount. When the toe angle change amount S3 increases to the toe-in side, the yaw response gain change amount changes to the DOWN side, that is, the direction in which the yaw response deteriorates (stable side), and changes to the DOWN side as the vehicle speed increases. . On the other hand, when the toe angle change amount S3 increases to the toe-out side, the yaw response gain change amount changes to the UP side, that is, the direction in which the yaw response improves (unstable side), and the higher the vehicle speed, the more the UP side To change. As described above, when the regenerative braking force increases, the compliance steer characteristic changes only to the toe-out side. Therefore, the yaw response gain change amount is calculated from the vehicle speed and the map shown in FIG.

FIG. 11 is a map showing the relationship between the yaw response gain change amount and the gear ratio correction coefficient Khf. The yaw response gain change amount is calculated from FIG. 10, and the gear ratio correction coefficient Khf corresponding to the yaw response gain change amount is calculated. Correction is performed so that the gear ratio decreases as the yaw response gain change amount increases (as the vehicle yaw rate change increases). Further, the gear ratio correction coefficient is set to a larger value as the vehicle speed is lower. Then, the corrected target front wheel steering angle θ * p is calculated by the following equation.
θ * p = (KPf / Khf) × θd + KDf × dθd / dt
Thereby, the steering angle ratio is corrected to the slow side by dividing the fixed front wheel proportional gain KPf by the gear ratio correction coefficient. In the first embodiment, only the proportional gain is changed, but the differential gain may be changed.

The corrected target rear wheel steering angle δ * is calculated by the following formula.
δ * = KPr × θd + KDr × dθd / dt + S3 × Khr
Here, Khr is calculated from the map shown in FIG. FIG. 12 is a map showing the relationship between the steering angle θ and the rear wheel steering angle correction coefficient. When the steering angle θ is near 0, that is, near the neutral position, the rear wheel steering angle correction amount is set to be small, and when the steering angle θ is equal to or larger than the predetermined steering angle, a correction amount corresponding to the toe angle change amount S3 is set.

  When the toe angle change amount S3 is calculated, the rear wheel steering angle correction amount is calculated by multiplying the toe angle change amount S3 by the rear wheel steering angle correction coefficient Khr corresponding to the steering angle θ, and the target rear wheel steering amount is calculated. The corrected target rear wheel steering angle δ * is calculated by adding to the angle δ * ref. At this time, since the rear wheel steering angle correction amount is always added to the in-phase side, the vehicle behavior is corrected to the more stable side (yaw rate is less likely to occur).

As described above, the effects listed below can be obtained in the first embodiment.
(1) A motor generator MG that applies a regenerative braking force to the drive wheels, a friction brake that applies a friction braking force to the drive wheels, and a target braking force of the vehicle is achieved by the regenerative braking force and / or the friction braking force. An integrated controller 10 (braking force control means) that controls the motor generator MG and / or friction brake to achieve, and a four-wheel active steering system that controls vehicle behavior based on the relationship between the regenerative braking force and the friction braking force ( Vehicle behavior control means).

  Therefore, even if the compliance steer changes due to a change in the relationship between the friction braking force and the regenerative braking force, the vehicle behavior control means can control the behavior to a desired value.

  (2) The vehicle behavior control means is a variable steering angle actuator that can change the ratio of the actual front wheel turning angle to the steering wheel steering angle. Therefore, the vehicle behavior characteristic can be easily controlled by adjusting the steering angle ratio.

  (3) The vehicle behavior control means is a rear wheel steering actuator that gives a steering angle to the rear wheels. Therefore, the vehicle behavior characteristic can be easily controlled by the in-phase control and the reverse phase control of the rear wheel steering angle.

  (4) The driving wheel is a rear wheel, and the vehicle behavior control means performs control so that the vehicle yaw rate decreases as the regenerative braking force increases. When the driving wheel is the rear wheel, the compliance steer changes from the toe-in state to the toe-out state when the regenerative braking force increases. That is, since the yaw response gain is high for the vehicle, the vehicle lacks stability. Therefore, vehicle stability can be ensured by controlling the vehicle yaw rate to be small.

  In the first embodiment, the rear-wheel drive hybrid vehicle has been described. However, the present invention can be similarly applied to a front-wheel drive hybrid vehicle. In this case, when the regenerative braking force of the front wheels increases, the yaw response gain decreases, and therefore, control may be performed so that the vehicle yaw rate increases. Specifically, the yaw response gain is increased by controlling the steering angle ratio of the variable steering angle actuator to be large. Alternatively, the yaw response gain is increased by performing reverse phase control of the rear wheel steering actuator. Thereby, vehicle stability can be ensured.

  The vehicle behavior control means may be a steer-by-wire system that can independently control the steering wheel steering angle and the actual front wheel turning angle. In this case as well, control may be performed such that the yaw response gain is increased for the front wheel drive type, and control is performed so that the yaw response gain is decreased for the rear wheel drive type. Thereby, vehicle stability can be ensured.

  In the first embodiment, the yaw response gain is changed by the steering angle control. However, the yaw rate is controlled by a braking force control means capable of controlling the friction braking force acting on each wheel, specifically, a vehicle dynamics control system or the like. It is good as well. Thereby, vehicle stability can be ensured.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall system diagram illustrating a rear-wheel drive hybrid vehicle according to a first embodiment. 1 is a system configuration diagram of a four-wheel active steering system mounted on a vehicle of Example 1. FIG. It is a block diagram showing the structure of the control unit of a four-wheel active steering system. It is a map showing the front-wheel proportional gain depending on the vehicle speed of a 4-wheel active steering system. It is a map showing the front wheel differential gain depending on the vehicle speed of the four-wheel active steering system. It is a map showing the rear-wheel proportional gain depending on the vehicle speed of a four-wheel active steering system. It is a map showing the rear-wheel differential gain depending on the vehicle speed of a four-wheel active steering system. It is the schematic showing the logic of the compliance steer by the tire front-back input at the time of braking. 3 is a flowchart showing control contents of a target value correcting unit of the four-wheel active steering system according to the first embodiment. 3 is a map showing a relationship between a toe angle change amount and a yaw response gain change amount according to the first embodiment. 6 is a map showing a relationship between a yaw response gain change amount and a gear ratio correction coefficient according to the first embodiment. 3 is a map showing a relationship between a steering angle and a rear wheel steering angle correction coefficient according to the first embodiment.

Explanation of symbols

E engine
MG motor generator
CL2 2nd clutch
AT automatic transmission
RL Left rear wheel (drive wheel)
RR Right rear wheel (drive wheel)
FL Left front wheel
FR Right front wheel
BURL Left rear wheel brake unit
BURR Right rear wheel brake unit
BUFL Left front wheel brake unit
BUFR Right front wheel brake unit 1 Engine controller 2 Motor controller 3 Inverter 4 Battery 5 Clutch controller 6 Clutch hydraulic unit 7 Controller 7a Inhibitor switch 8 Clutch hydraulic unit 9 Brake controller 10 Integrated controller 17 Vehicle speed sensor 33 Variable steering angle actuator 36 Rear wheel steering actuator
100 control unit
120 Target value correction unit, front wheels
MG motor generator

Claims (6)

A motor generator for applying a regenerative braking force to the rear wheels as drive wheels;
A frictional braking means for applying a frictional braking force to the rear wheel,
Braking force control means for controlling the motor generator and / or the friction braking means so as to achieve a target braking force of the vehicle by the regenerative braking force and / or the friction braking force;
And the vehicle behavior control means for controlling the vehicle behavior based on the relationship between the frictional braking force and the regenerative braking force,
Equipped with a,
The vehicle behavior control means controls the vehicle yaw rate so that the vehicle yaw rate decreases as the regenerative braking force increases . A motor generator for applying a regenerative braking force to the front wheels as drive wheels;
Friction braking means for applying a friction braking force to the front wheels;
Braking force control means for controlling the motor generator and / or the friction braking means so as to achieve a target braking force of the vehicle by the regenerative braking force and / or the friction braking force;
Vehicle behavior control means for controlling vehicle behavior based on the relationship between the regenerative braking force and the friction braking force;
With
The vehicle behavior control means controls the vehicle yaw rate so that the vehicle yaw rate increases as the regenerative braking force increases . The braking control device according to claim 1 or 2,
The braking control device according to claim 1, wherein the vehicle behavior control means is variable steering angle control means capable of changing a ratio of an actual front wheel turning angle to a steering wheel steering angle . The braking control device according to any one of claims 1 to 3,
The vehicle behavior control means is a rear wheel steering control means for giving a steering angle to the rear wheels . The braking force control device according to any one of claims 1 to 4,
The braking control apparatus according to claim 1, wherein the vehicle behavior control means is a steer-by-wire system capable of independently controlling a steering wheel steering angle and an actual front wheel turning angle . In the braking control device according to any one of claims 1 to 5 ,
The braking control apparatus according to claim 1, wherein the vehicle behavior control means is a braking force control means capable of controlling a friction braking force acting on each wheel .

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