JP2012056367A - Control device of electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure stability of vehicle behavior in a running scene close to a critical region while using, to the maximum, the power consumption rate improvement effect by regenerative cooperation control.SOLUTION: The control device of electric vehicle includes: a motor controller 21 and a brake controller 10 as a regenerative cooperation brake control unit; a 4WAS (four-wheel anti-skid) controller 22 as a rudder angle correction steering control unit; and a vehicle controller 9 as a vehicle behavior control unit. The vehicle controller 9 corrects the rudder angle by the rudder angle correction steering control so as to compensate the disorder of a vehicle behavior upon the regenerative cooperation brake control, and thereafter, performs a control so as to lower a regenerative torque with the regenerative cooperation brake control (steps S7, S8 in Fig.4) when it is determined that the vehicle behavior is still unstable (NO in a step S6 in the Fig.4).

Description

  The present invention relates to a control device for an electric vehicle that is applied to an electric vehicle such as an electric vehicle or a hybrid vehicle and compensates for disturbance of vehicle behavior by regenerative cooperative brake control by steering angle correction.

  Conventionally, in the event that compliance steer changes in front or rear tires due to regenerative cooperative braking, resulting in disordered vehicle behavior, vehicle behavior is controlled by steering control that corrects the steering angle of at least one of the front and rear wheels. 2. Description of the Related Art A braking control device that compensates for disturbances is known (see, for example, Patent Document 1). Note that the compliance steer is a change in the suspension geometry caused by elastic deformation of the suspension link support bush when a braking force or lateral force is input to the tire, resulting in a change in toe angle (= steering angle change). ).

JP 2009-90899 A

  However, in the conventional braking control device, during regenerative coordinated braking, the disturbance of the vehicle behavior is compensated by correcting the steering angle for the compliance steer in the region where the lateral force with respect to the side slip angle of the tire is linear. ing. For this reason, in a driving scene that is closer to the limit region where the lateral force generated by the tire with respect to steering is saturated and the vehicle behavior is non-linear with respect to steering, the vehicle behavior can be improved by simply correcting the steering angle. There was a problem that it was difficult to compensate for the disturbance.

  The present invention has been made paying attention to the above problem, and is an electric vehicle capable of ensuring the stability of vehicle behavior in a driving scene close to a limit region while maximizing the power consumption improvement effect by regenerative cooperative control. An object is to provide a control device.

In order to achieve the above object, the control device for an electric vehicle according to the present invention includes a regenerative cooperative brake control unit, a steering angle correction steering control unit, and a vehicle behavior control unit.
The regenerative cooperative brake control means performs regenerative cooperative brake control that distributes the remaining braking torque, which is obtained by subtracting the regenerative torque generated by the motor-driven wheels from the total braking torque based on the brake operation, to the friction brake torque generated by the friction brakes of the front and rear wheels. Do.
The steering angle correction steering control means corrects the steering angle of at least one of the front and rear wheels so as to compensate for disturbance in vehicle behavior during the regenerative cooperative brake control.
The vehicle behavior control means performs control for reducing the regenerative torque by the regenerative cooperative brake control means when it is determined that the vehicle behavior is still unstable after the steering angle correction by the steering angle correction steering control means. Do.

Therefore, at the time of regenerative cooperative brake control, the steering angle correction steering control means corrects at least one of the front and rear wheels so as to compensate for the disturbance of the vehicle behavior. Then, after the steering angle is corrected by the steering angle correction steering control means, when it is determined that the vehicle behavior is still unstable, the vehicle behavior control means performs control to reduce the regenerative torque by the regenerative cooperative brake control means. Is called.
That is, in a traveling scene in which the disturbance of the vehicle behavior is compensated only by the steering angle correction, the regenerative torque is not reduced and the expected regenerative amount is ensured. On the other hand, regenerative torque is reduced only when the steering angle correction control precedes, for example, a steering intervention that applies lateral force to the tires results in a driving scene where the vehicle behavior is still unstable even if the steering angle is corrected. Control is performed. With this two-stage control, the stability of the vehicle behavior is ensured by recovering the tire grip force and adjusting the front-rear distribution of the braking force in a driving scene close to the limit region while ensuring as much regeneration as possible.
As a result, it is possible to ensure the stability of the vehicle behavior in the driving scene close to the limit region while maximizing the power consumption improvement effect by the regenerative cooperative control.

1 is an overall system diagram showing a regenerative cooperative brake control system and a four-wheel active steering control system of an electric vehicle (an example of an electric vehicle) to which a control device of Example 1 is applied. It is a block diagram which shows the whole structure of the vehicle behavior control calculation process performed with the vehicle controller 9 of Example 1. FIG. It is a block diagram which shows the detail of a steering angle correction | amendment logic among the vehicle behavior control calculation processes of Example 1. FIG. 4 is a flowchart illustrating a flow of a vehicle behavior control process executed by the vehicle controller 9 according to the first embodiment. FIG. 3 is a tire lateral force characteristic diagram showing a relationship of tire lateral force with respect to a tire lateral slip angle. It is a characteristic view which shows the relationship of the regenerative torque reduction allowance with respect to the difference with reference | standard behavior. 6 is a time chart showing time series responses of a steering wheel angle, a yaw rate, a front wheel rudder angle correction amount, and a braking G in a steering scene from constant G braking when Example 1 is applied. It is a block diagram which shows the whole structure of the vehicle behavior control calculation process performed with the vehicle controller 9 of Example 2. FIG. It is a block diagram which shows the detail of a steering angle correction | amendment logic among the vehicle behavior control calculation processes of Example 2. FIG. 4 is a flowchart illustrating a flow of a vehicle behavior control process executed by the vehicle controller 9 according to the first embodiment. FIG. 4 is a tire characteristic diagram showing a relationship between an apparent road surface μ and a tire maximum lateral force with respect to a tire slip rate inherent to the tire. 6 is a tire characteristic map showing a tire lateral force limit line in relation to an estimated value of a tire lateral force with respect to a tire slip ratio used in the vehicle behavior control process of the second embodiment. FIG. 6 is a characteristic diagram showing a relationship of a regeneration reduction gain with respect to a tire lateral force ratio (= tire lateral force estimated value / tire lateral force limit value). FIG. 10 is an operation explanatory diagram illustrating a vehicle behavior control operation when an instantaneous tire state value moves on a tire characteristic map in the second embodiment.

  Hereinafter, the best mode for realizing an electric vehicle control device of the present invention will be described based on Example 1 and Example 2 shown in the drawings.

First, the configuration will be described.
FIG. 1 is an overall system diagram showing a regenerative cooperative brake control system and a four-wheel active steering control system of an electric vehicle (an example of an electric vehicle) to which the control device of the first embodiment is applied. The overall system configuration will be described below with reference to FIG.

  As shown in FIG. 1, the electric vehicle of the first embodiment is based on an FF vehicle, and includes a left front wheel tire 14FL, a right front wheel tire 14FR, a left rear wheel tire 14RL, and a right rear wheel tire 14RR, and left and right front wheel tires 14FL, 14FR is a drive wheel / steering wheel, and left and right rear tires 14RL and 14RR are driven wheels.

  Driving torque from the driving motor 1 is applied to the left and right front wheel tires 14FL and 14FR during traveling. At the time of braking, both the regenerative torque by the regenerative brake and the friction torque by the friction brake are applied. Further, at the time of turning or lane change, a steering angle and a corrected steering angle are added as necessary.

  The left and right rear wheel tires 14RL and 14RR are subjected to friction torque by a friction brake during braking. Further, when turning or changing lanes, a correction steering angle is added as necessary.

  As shown in FIG. 1, the regenerative cooperative brake control system includes a drive motor 1, a drive motor inverter 2, a secondary battery 3, a battery controller 4, an accelerator pedal 5, an accelerator opening sensor 6, and a brake. A pedal 7, a brake stroke sensor 8, a vehicle controller 9, a brake controller 10, a brake actuator 11, a master cylinder 12, a master cylinder pressure sensor 13, a brake hydraulic system 15, and a vehicle speed sensor 16 are provided. I have.

  The drive motor 1 is a driving source for driving an electric vehicle, and is connected to left and right front wheel tires 14FL and 14FR, which are drive wheels, via a final differential gear 23. When a positive torque command is output from the motor controller 21 to the drive motor inverter 2, the drive motor 1 performs a drive operation to generate drive torque using the discharge power from the secondary battery 3, and the left and right front wheels Drives tires 14FL and 14FR (powering). On the other hand, when a negative torque command is output from the motor controller 21 to the drive motor inverter 2, a power generation operation is performed to convert rotational energy from the left and right front wheel tires 14FL, 14FR into electric energy, and the generated power is secondary. The charging power of the battery 3 is used (regeneration). During this motor regeneration, a power generation load from the drive motor 1 is applied to the left and right front wheel tires 14FL, 14FR, and this power generation load serves as a regenerative brake that brakes the left and right front wheel tires 14FL, 14FR, thereby generating regenerative torque.

  The battery controller 4 determines the voltage, charge / discharge current, charge amount (= battery SOC), internal temperature (= temperature of IGBT, etc.), degree of deterioration (= battery usage time, etc.), etc. To detect. Further, the battery input / output possible power is calculated based on the state of the secondary battery 3, and the battery state information and the battery input / output possible power information are output to the vehicle controller 9.

  The brake controller 10 inputs brake stroke information from the brake stroke sensor 8 and outputs brake stroke information to the vehicle controller 9. When a brake fluid pressure command value is input from the vehicle controller 9, a control command for obtaining a friction torque corresponding to the brake fluid pressure command value is output to the brake actuator 11 based on master cylinder pressure information from the master cylinder pressure sensor 13.

  When a command for obtaining a friction brake torque is output from the vehicle controller 9 to the brake controller 10, the brake actuator 11 generates four brake fluid pressures by fluid pressure control using the master cylinder pressure as a base pressure. The brake fluid pressure of these four systems passes through the brake fluid pressure pipes 15FL, 15FR, 15RL, and 15RR, and is supplied to the wheel cylinders of the wheel tires 14FL, 14FR, 14RL, and 14RR so that the brake pads sandwich the brake disc. Friction brake torque is applied to each wheel tire 14FL, 14FR, 14RL, 14RR by friction welding.

  The vehicle controller 9 is a controller that collectively manages the regenerative cooperative brake system and the four-wheel active steering control system so as to ensure high power consumption performance while ensuring the stability of vehicle behavior. For this reason, the vehicle controller 9, the battery controller 4, the brake controller 10, the motor controller 21, and the 4WAS controller 22 are connected by a CAN communication line 24 that is a bidirectional communication line capable of exchanging information.

  An example of regenerative cooperative control performed by the vehicle controller 9 will be described. During braking by regenerative cooperative control, a total braking torque command is calculated based on the brake stroke from the brake stroke sensor 8. Then, based on the driver-requested regenerative torque, the battery regenerative torque, and the motor regenerative torque, a regenerative torque command to be generated by regenerative control of the drive motor 1 is determined. Then, a friction brake torque command is output to the brake controller 10 so that the friction torque compensates for the shortage of the regenerative torque alone with respect to the total braking torque.

  The vehicle controller 9 includes a steering angle sensor 17 that measures the angle of the steering wheel, a yaw rate sensor 18 that detects the yaw rate of the vehicle, a lateral G sensor 19 that detects lateral acceleration of the vehicle, and a wheel speed of each wheel. Information from the wheel speed sensor 20 or the like is input.

  As shown in FIG. 1, the four-wheel active steering control system includes a steering angle sensor 17, a 4WAS controller 22, a handle 25, a steering gear shaft 26, a 4WAS front motor 27, a 4WAS front lock solenoid valve 28, A front wheel rudder angle sensor 29, a steering shaft 30, a front wheel side rack & pinion mechanism 31, a 4WAS rear motor 32, a rear wheel rudder angle sensor 33, and a rear wheel side rack & pinion mechanism 34 are provided.

  The steering gear shaft 26, the 4WAS front motor 27, the 4WAS front lock solenoid valve 28, and the front wheel steering angle sensor 29 constitute a 4WAS front actuator. This 4WAS front actuator changes the steering angle ratio, which is the ratio of the front wheel steering angle to the steering wheel steering angle θ. That is, when a front wheel steering angle correction command is output from the 4WAS controller 22 to the 4WAS front motor 27, the steering angle ratio is changed by adding or subtracting the motor rotation angle with respect to the steering angle θ.

  The 4WAS rear motor 32 and the rear wheel steering angle sensor 33 constitute a 4WAS rear actuator. When the 4WAS rear actuator 32 outputs a rear wheel steering angle correction command to the 4WAS rear motor 32, the 4WAS rear actuator gives a steering angle to the rear wheels according to the motor rotation angle.

  FIG. 2 is a block diagram illustrating the overall configuration of the vehicle behavior control calculation process executed by the vehicle controller 9 of the first embodiment. The steering angle correction logic B1, the vehicle behavior determination logic B2, and the regeneration correction logic B3 are illustrated in FIG. Are constituted by three blocks.

  In the steering angle correction logic B1, the front wheel steering angle correction command and the rear wheel steering angle correction are performed using the steering wheel angle measured by the steering angle sensor 17 and the actual behavior of the vehicle measured by the yaw rate sensor 18 and the lateral G sensor 19. Command and vehicle behavior normative values are calculated. The front wheel steering angle correction command and the rear wheel steering angle correction command are sent to the 4WAS controller 22 in accordance with the system shown in FIG. The vehicle behavior normative value is sent to the next vehicle behavior determination logic B2.

  The vehicle behavior determination logic B2 compares an actual vehicle behavior (for example, yaw rate sensor value) with a standard vehicle behavior (for example, yaw rate standard value), and finally determines a reduction amount of the regenerative torque based on the difference.

  The regenerative correction logic B3 outputs a command value for reducing the regenerative torque and increasing the friction brake torque according to the regenerative torque reduction allowance command value and the total braking torque command sent from the vehicle behavior determination logic B2. To do.

  FIG. 3 is a block diagram illustrating details of the steering angle correction logic in the vehicle behavior control calculation process of the first embodiment, and includes a reference behavior estimation logic B11, a difference unit B14, and a steering angle correction logic B12. Configured.

  The reference behavior estimation logic B11 calculates a vehicle behavior reference value based on the reference model response at that moment based on the steering wheel angle θ and the vehicle speed V. As a calculation method, a simple model such as a two-wheel model for steering angle input under a certain vehicle condition may be used to derive the response, or a complex vehicle model may be used. A model such as

  The differencer B14 calculates the difference between the actual vehicle behavior (for example, yaw rate sensor value) and the vehicle behavior standard value (for example, yaw rate standard value), and sends it to the steering angle correction logic B12.

  In the steering angle correction logic B12, the steering angle correction amounts of the front wheels and the rear wheels that only compensate for the difference in behavior are calculated. Here, the steering angle output of the behavior input is calculated by the inverse model of the vehicle model in which the actual vehicle shows the vehicle response to the steering.

  FIG. 4 is a flowchart illustrating a flow of a vehicle behavior control process executed by the vehicle controller 9 according to the first embodiment. Hereinafter, each step of FIG. 4 will be described. In the first embodiment, the vehicle behavior disturbance index value is given by the yaw rate deviation Δγ.

  In step S1, when regenerative braking is started, the steering wheel angle θ, the vehicle speed V, and the yaw rate γ are read, and the process proceeds to step S2.

  In step S2, following the vehicle behavior reading in step S1, a yaw rate reference value γ * which is a vehicle behavior reference value is calculated based on the read steering wheel angle θ and vehicle speed V, and the process proceeds to step S3. The method for calculating the yaw rate normative value is as described in the normative behavior estimation logic B11 in FIG.

  In step S3, following the calculation of the yaw rate reference value γ * in step S2, a steering angle correction value for the front and rear wheels for correcting the difference between the yaw rate reference value γ * and the actual yaw rate γ read in step S1 is calculated. Proceed to step S4. The calculation method of the steering angle correction values for the front wheels and the rear wheels is as described in the steering angle correction logic B12 of FIG.

  In step S4, following the calculation of the steering angle correction values for the front and rear wheels in step S3, a steering angle correction command for correcting the actual steering angles of the front and rear wheels based on the calculated steering angle correction values for the front and rear wheels. And proceeds to step S5.

  In step S5, following the rudder angle correction in step S4, it is determined whether or not regenerative braking is performed. If YES (during regenerative braking), the process proceeds to step S6. If NO (regenerative braking is not being performed) Proceed to return.

In step S6, following the determination that regenerative braking is being performed in step S5, it is determined whether or not the yaw rate deviation Δγ between the actual yaw rate γ indicating the actual behavior and the yaw rate reference value γ * indicating the normal behavior is within the threshold γth. . If YES (Δγ ≦ γth), the process proceeds to return, and if NO (Δγ> γth), the process proceeds to step S7.
Here, as shown in FIG. 5, the threshold value γth is set to the value of the boundary region between the linear region and the nonlinear region in the tire lateral force characteristic with respect to the tire side slip angle.

In step S7, following the determination that Δγ> γth in step S6, a regenerative torque reduction allowance is calculated, and the process proceeds to step S8.
Here, as shown in FIG. 6, the calculation of the regenerative torque reduction allowance (value for reducing the regenerative torque) is given according to the magnitude of the yaw rate deviation Δγ when the yaw rate deviation Δγ exceeds the threshold value γth. That is, until the yaw rate deviation Δγ is up to Δγ1, the amount of regenerative torque reduction (the amount to reduce regenerative torque) increases as the yaw rate deviation Δγ increases, and when the yaw rate deviation Δγ exceeds Δγ1, the amount of regenerative torque reduction is given by a constant amount. When the time change of the yaw rate deviation Δγ is large, Δγ1 when the time change is small is lowered to Δγ1 ′, and the amount of reduction of the regenerative torque is increased compared to when the time change is small.

  In step S8, following the regenerative torque reduction allowance calculation in step S7, based on the regenerative torque command value calculated in step S8, control is performed to reduce the regenerative torque amount regenerated by the drive motor 1, and the process proceeds to return.

Next, the operation will be described.
The control operation of the electric vehicle according to the first embodiment will be described by dividing it into “problem of regenerative cooperative brake control” and “vehicle behavior control operation during regenerative braking”.

[Problems of regenerative cooperative brake control]
First, the allowable values for the total input of driving force, braking force, and lateral force that can be input to the vehicle tire are determined by the tire-road friction coefficient and wheel load at that time, and this is the tire capacity. That's it.

  Accordingly, in the electric vehicle according to the first embodiment shown in FIG. 1, during regenerative braking, for example, when braking is performed only with regenerative torque at the beginning of braking, the left and right front wheel tires 14FL and 14FR correspond to total braking torque. When a large regenerative braking force is applied, and steering intervenes at this time, a lateral force is further applied to the regenerative braking force. Note that neither the braking force nor the lateral force is applied to the left and right rear wheel tires 14RL, 14RR unless the friction brake torque is applied, so the braking force distribution is also distributed only to the front wheels.

  Therefore, during regenerative braking, if a large regenerative braking force is applied to the left and right front wheel tires 14FL, 14FR and a lateral force due to steering intervention is input in a tire capacity limit state, the left and right front wheel tires 14FL, Lateral force generated by 14FR is saturated. As described above, when the lateral force generated by the tire with respect to the steering is saturated beyond the tire capacity, a non-linear vehicle behavior with respect to the steering is exhibited as shown in the non-linear region of FIG.

  As described above, when the input to the tire is saturated beyond the tire capacity, the road surface grip force of the tire is reduced, so that it becomes difficult to compensate for the disturbance of the vehicle behavior even if the steering angle correction is performed. In other words, in order to compensate for vehicle behavior disturbance, the input to the tire must be less than the tire capacity. In the case of the first embodiment, the regenerative torque applied to the left and right front tires 14FL, 14FR It needs to be lowered.

  Therefore, when steering intervenes during regenerative braking, the regenerative torque is limited in advance with respect to the total braking torque, and regenerative cooperative control is performed in combination with the friction brake torque. In this case, the state where the input to the tire is equal to or less than the tire capacity and the braking force is distributed to the front and rear wheels is maintained, and the disturbance of the vehicle behavior can be suppressed. However, regardless of whether or not the vehicle behavior is disturbed by the steering intervention, the regenerative torque will be limited from the beginning of the steering intervention, and the regenerative torque limit will increase the power consumption by securing the regenerative amount. To lose.

[Vehicle behavior control action during regenerative braking]
Therefore, in order to achieve both improvement in power consumption and stabilization of vehicle behavior, it is divided into a linear region that exhibits linear vehicle behavior with respect to steering and a nonlinear region that exhibits nonlinear vehicle behavior with respect to steering. The angle correction is performed, and the configuration that reduces the regenerative torque in the non-linear range is adopted.

  When the regenerative cooperative brake control is performed and the yaw rate deviation Δγ is within the threshold value γth, in the flowchart of FIG. 4, the flow proceeds from step S1, step S2, step S3, step S4, step S5, step S6, and return. Repeated. That is, in step S4, a steering angle correction command for correcting the actual steering angles of the front wheels and the rear wheels is output based on the calculated steering angle correction values of the front wheels and the rear wheels so as to compensate for vehicle behavior disturbance. The rudder angle of at least one of the wheels is corrected.

  When it is determined that the vehicle behavior is still unstable and the yaw rate deviation Δγ exceeds the threshold value γth regardless of the steering angle correction, in the flowchart of FIG. 4, step S1 → step S2 → step S3 → The flow of going from step S4 → step S5 → step S6 → step S7 → step S8 → return is repeated. That is, in step S7, the regenerative torque reduction allowance is calculated, and in step S8, control for reducing the regenerative torque is performed.

  That is, in a traveling scene (yaw rate deviation Δγ ≦ γth) in which the disturbance of the vehicle behavior is compensated only by the steering angle correction, the regenerative torque is not reduced and the expected regenerative amount is ensured. On the other hand, there is a control to reduce the regenerative torque only when the driving scene (yaw rate deviation Δγ> threshold γth) is preceded by the steering angle correction control and the vehicle behavior is still unstable even after the steering angle correction. Done. This two-stage control ensures as much regeneration as possible, while this two-stage control ensures as much regeneration as possible while maintaining a tire grip force in a driving scene close to the limit area. The stability of the vehicle behavior is ensured by the recovery and adjustment of the distribution of braking force.

  In other words, when the regenerative torque is reduced, the reduced amount is shared by the friction brake torque at the rear wheels or the front and rear wheels, and the braking force shared by the left and right front wheel tires 14FL, 14FR is suppressed below the tire capacity, The road grip of the front tires 14FL and 14FR is restored. When the steering angle correction is controlled in a state where the road surface grip force is recovered, the steering angle correction is performed in a region where the lateral force with respect to the side slip angle of the tire is linear, and the effect of compensating for vehicle behavior disturbance is exhibited. In addition, by adjusting the braking force distribution of the front and rear wheels in the equally distributed direction, an effect of compensating for vehicle behavior disturbance is exhibited.

  Incidentally, FIG. 7 is a time chart showing time series responses of the steering wheel angle, the yaw rate, the front wheel steering angle correction amount, and the braking G in the steering scene from the constant G braking when the first embodiment is applied.

  Under the constant braking G condition from time t0 to time t1, braking by 100% regenerative braking is performed. Then, as shown in the steering wheel angle characteristic, with the start of steering from time t0, a divergence occurs between the vehicle behavior standard value (yaw rate standard value γ *) and the vehicle behavior (actual yaw rate γ). However, in the region up to time t1, the difference between the vehicle behavior standard value (yaw rate standard value γ *) and the vehicle behavior (actual yaw rate γ) is reduced by correcting the steering angle of the front wheels. Then, as the steering wheel angle is increased, the tire enters a non-linear region, and the yaw rate deviation Δγ of the vehicle behavior standard value (yaw rate standard value γ *) and the vehicle behavior (actual yaw rate γ) spreads rapidly. Exceed. When the yaw rate deviation Δγ exceeds the threshold value γth, the regenerative torque is reduced from 100% regenerative braking, and the regenerative torque and friction brake torque are used in combination. Then, the front-rear force distribution of the front wheels and the rear wheels is adjusted, and the vehicle behavior (actual yaw rate γ) follows the vehicle behavior normative value (yaw rate normative value γ *), and the vehicle behavior can be stabilized.

As described above, in the first embodiment, during regenerative braking, the steering angle correction control precedes, and even when the steering angle correction is performed, the vehicle behavior is still unstable (yaw rate deviation Δγ> threshold γth). Only occasionally, control to lower the regenerative torque is performed.
Therefore, the stability of the vehicle behavior is ensured in the driving scene close to the limit region while maximizing the power consumption improvement effect by the regenerative cooperative control.

In the first embodiment, after the steering angle is corrected by the steering angle correction control, the vehicle behavior turbulence index value (yaw rate deviation Δγ) representing the amount of turbulence in the vehicle behavior becomes a value in the boundary region between the linear region and the nonlinear region of the tire lateral force. When the set threshold (threshold γth) is exceeded, it is determined that the vehicle behavior is unstable.
In other words, control is performed such that the steering angle is corrected in a linear region showing a linear vehicle behavior with respect to steering, and the regenerative torque is reduced to the steering angle correction in a nonlinear region showing nonlinear vehicle behavior with respect to steering.
Therefore, the power consumption improvement effect by the regenerative cooperative control is ensured to the maximum in the linear region showing the linear vehicle behavior with respect to the steering, and the stability of the vehicle behavior is reliably ensured in the driving scene close to the limit region.

In the first embodiment, as the vehicle behavior disorder index value (yaw rate deviation Δγ) is larger, the regenerative torque reduction range is increased (FIG. 6).
Therefore, as the vehicle behavior disturbance index value (yaw rate deviation Δγ) increases, the amount of regenerative torque reduction (amount of decrease in regenerative torque) is increased, and the vehicle behavior is stabilized.

In the first embodiment, when the time change of the vehicle behavior disturbance index value (yaw rate deviation Δγ) is large, the reduction range of the regenerative torque is increased (FIG. 6).
Therefore, when the time change of the vehicle behavior disturbance index value (yaw rate deviation Δγ) is large, an effect of stabilizing the vehicle behavior at an early stage is exhibited by increasing the amount of decrease in the regenerative torque.

In the first embodiment, a vehicle behavior difference (yaw rate deviation Δγ) between a vehicle behavior standard value (yaw rate standard value γ *) and a vehicle actual behavior value (actual yaw rate γ) is used as a vehicle behavior disorder index value.
Therefore, in a driving scene close to the limit region, the actual yaw rate γ around the center of gravity of the vehicle converges to the yaw rate reference value γ *, thereby ensuring the stability of the vehicle behavior.

Next, the effect will be described.
In the control apparatus for the electric vehicle according to the first embodiment, the effects listed below can be obtained.

(1) Regenerative coordination that distributes the remaining braking torque, which is obtained by subtracting the regenerative torque from the motor-driven wheels (left and right front tires 14FL, 14FR) from the total braking torque based on the brake operation, to the friction brake torque by each friction brake on the front and rear wheels Regenerative cooperative brake control means (motor controller 21, brake controller 10) for performing brake control;
Steering angle correction steering control means (4WAS controller 22) for correcting the steering angle of at least one of the front and rear wheels so as to compensate for disturbance in vehicle behavior during the regenerative cooperative brake control;
When it is determined that the vehicle behavior is still unstable after the steering angle correction by the steering angle correction steering control means (4WAS controller 22), the regeneration cooperative brake control means (motor controller 21, brake controller 10) Vehicle behavior control means (vehicle controller 9, FIG. 4) for performing control for reducing the regenerative torque;
Is provided.
For this reason, it is possible to ensure the stability of the vehicle behavior in a driving scene close to the limit region while maximizing the power consumption improvement effect by the regenerative cooperative control.

(2) The vehicle behavior control means (vehicle controller 9, FIG. 4) corrects the steering angle by the steering angle correction steering control, and then indicates a vehicle behavior disturbance index value (yaw rate deviation) representing a disturbance amount or a predicted disturbance amount of the vehicle behavior. When (Δγ) exceeds a threshold value (threshold value γth) set to the value of the boundary region between the linear region and the nonlinear region of the tire lateral force, it is determined that the vehicle behavior is unstable (step S6 in FIG. 4).
For this reason, in addition to the effect of (1) above, power consumption is improved by regenerative cooperative control in a linear region showing linear vehicle behavior with respect to steering while ensuring the stability of vehicle behavior in a driving scene close to the limit region. It is possible to ensure the maximum effect.

(3) The vehicle behavior control means (vehicle controller 9, FIG. 4) increases the reduction range of the regenerative torque as the vehicle behavior disturbance index value (yaw rate deviation Δγ) increases (FIG. 6).
For this reason, in addition to the effect of (2) above, as the vehicle behavior disturbance index value (yaw rate deviation Δγ) is larger, the amount of seamless regenerative torque reduction is increased, resulting in a change in vehicle behavior caused by lowering the regenerative torque. Can be suppressed.

(4) The vehicle behavior control means (vehicle controller 9, FIG. 4) increases the reduction amount of the regenerative torque when the time change of the vehicle behavior disturbance index value (yaw rate deviation Δγ) is large (FIG. 6).
For this reason, in addition to the effect of (2) or (3) above, it is possible to suppress sudden changes in vehicle behavior (unstable vehicle behavior) by responding quickly to transient vehicle behavior changes. .

(5) The vehicle behavior control means (vehicle controller 9, FIG. 4) calculates a vehicle behavior difference (yaw rate deviation Δγ) between the vehicle behavior standard value (yaw rate standard value γ *) and the vehicle actual behavior value (actual yaw rate γ). The vehicle behavior disturbance index value is used.
For this reason, in addition to the effects (2) to (4) above, in the driving scene close to the limit region, the actual yaw rate γ around the center of gravity of the vehicle is converged to the yaw rate reference value γ *, thereby improving the stability of the vehicle yaw behavior. Can be secured.

  The second embodiment is an example in which a tire lateral force ratio Fyr representing a predicted amount of vehicle behavior disturbance is used as the vehicle behavior disturbance index value.

First, the configuration will be described.
In the control apparatus for an electric vehicle according to the second embodiment, the overall system configuration is the same as that of FIG.

  FIG. 8 is a block diagram showing the overall configuration of the vehicle behavior control calculation process executed by the vehicle controller 9 of the second embodiment. The steering angle correction logic B1, the tire capacity estimation logic B4, and the regeneration correction logic B5 are shown in FIG. And three blocks.

  In the steering angle correction logic B1, the front wheel steering angle correction command and the rear wheel steering angle correction are performed using the steering wheel angle measured by the steering angle sensor 17 and the actual behavior of the vehicle measured by the yaw rate sensor 18 and the lateral G sensor 19. Command and tire lateral force estimated value are calculated. The front wheel steering angle correction command and the rear wheel steering angle correction command are sent to the 4WAS controller 22 in accordance with the system shown in FIG. The estimated tire lateral force value is sent to the tire capacity estimation logic B4 and the regeneration correction logic B5.

  In the tire capacity estimation logic B4, the maximum lateral force that can be generated by the tire slip amount of each wheel according to the tire characteristic map is compared with the estimated lateral force value to determine whether or not to reduce the regenerative torque. Further, the maximum tire lateral force limit value that can be generated by the tire in the instantaneous tire slip is calculated according to the tire characteristic map, and is sent to the regeneration correction logic B5.

  In the regenerative correction logic B5, the regenerative torque is reduced according to the tire lateral force limit value, the regenerative reduction ON / OFF, and the total braking torque command sent from the tire capacity estimation logic B4. Output increasing command value.

  FIG. 9 is a block diagram showing details of the steering angle correction logic in the vehicle behavior control calculation processing of the second embodiment. The reference behavior estimation logic B11, the differencer B14, the steering angle correction logic B12, and the tire lateral force And an estimation logic B13. Note that the normative behavior estimation logic B11, the differentiator B14, and the steering angle correction logic B12 are the same as those in the first embodiment, and thus the description thereof is omitted.

  In the tire lateral force estimation logic B13, an estimated tire lateral force value of a tire that performs regenerative braking is calculated based on the steering wheel angle θ, the vehicle speed V, and the vehicle behavior. The calculation method of the tire lateral force estimated value can be derived by an observer using a simple model such as a two-wheel model of steering angle input under a constant vehicle condition, and a complicated vehicle model can be used as a vehicle model, It is also possible to apply a method with higher accuracy by using a method such as a Kalman filter or an extended Kalman filter for the observer.

FIG. 10 is a flowchart illustrating a flow of a vehicle behavior control process executed by the vehicle controller 9 according to the second embodiment. Hereinafter, each step of FIG. 10 will be described. In the second embodiment, the vehicle behavior disorder index value is given by the tire lateral force ratio Fyr.
Steps S21 to S25 in FIG. 10 are the same as steps S1 to S5 in FIG.

In step S26, following the determination that regenerative braking is being performed in step S25, a tire characteristic map defining the tire maximum lateral force with respect to the tire slip ratio of the regenerative wheel is read, and the process proceeds to step S27.
Here, in order to explain the tire characteristic map, the original characteristic of the tire is shown in FIG. FIG. 11 shows the relationship between the apparent road surface μ (front / rear force) and the tire maximum lateral force Fy with respect to the tire slip rate. The apparent road surface μ showing the magnitude of the force in the tire front-rear direction has a peak at a certain slip ratio, and has a characteristic of being saturated at more than that. In contrast, the tire maximum lateral force has a characteristic of decreasing as the slip ratio increases. Using this characteristic, the tire characteristic map shown in FIG. 12 is set according to the actual tire characteristic.

  In step S27, following the reading of the tire characteristic map in step S26, the tire slip ratio calculated by the wheel speed and the vehicle speed of the regenerative wheel is obtained, and the process proceeds to step S28.

  In step S28, following the reading of the tire slip ratio in step S27, the tire characteristic map read in step S26 is searched based on the tire slip ratio value read in step S27, and the lateral force that can be generated at that moment of the regenerative wheel. The tire lateral force limit value that is the maximum value of is obtained, and the process proceeds to step S29.

  In step S29, following the calculation of the maximum lateral force in step S28, as shown in the description of the tire lateral force estimation logic B13 in FIG. 9, the tire lateral force estimated value at the moment of the regenerative wheel is calculated, and the process proceeds to step S30.

In step S30, following the actual lateral force calculation in step S29, the tire side which is the ratio of the actual tire lateral force estimated value of the regenerative wheel calculated in step S29 to the tire lateral force limit value of the regenerated wheel calculated in step S28. A force ratio Fyr is calculated, and it is determined whether or not the tire lateral force ratio Fyr is within a threshold value Fyth. If YES (Fyr ≦ Fyth), the process proceeds to return, and if NO (Fyr> Fyth), the process proceeds to step S31.
Here, the threshold value Fyth is set to a value smaller than 1 before the estimated tire lateral force value indicating the actual lateral force reaches the tire lateral force limit value.

In step S31, following the determination that Fyr> Fyth in step S30, a regenerative torque reduction allowance is calculated, and the process proceeds to step S32.
The method for reducing the regenerative torque is as follows:
Freg = (1-K) × Freg_req (1)
Where Freg: Regenerative torque command correction value
Freg_req: Regenerative torque command value K: Regenerative reduction gain.
As shown in FIG. 13, the regeneration reduction gain K is determined with respect to the tire lateral force ratio Fyr. When the tire lateral force ratio Fyr exceeds the threshold Fyth, the regeneration reduction gain K gradually increases from K = 0 as the tire lateral force ratio Fyr increases. When the tire lateral force ratio Fyr becomes Fyr1, the value K = 1 is shown. . When the regenerative reduction gain K is K = 0, Freg = Freg_req, and braking is performed with the regenerative brake. When the regenerative reduction gain K is K = 1, Freg = 0 and the regenerative brake is zero (braking only with the friction brake). And when the time change of the tire lateral force ratio Fyr is large, the threshold value Fyth is shifted to a lower value side (threshold value Fyth '), and when the tire lateral force ratio Fyr becomes large, the regeneration reduction gain K becomes early K = Set to reach 1.

  In step S32, following the regenerative torque reduction allowance calculation in step S31, control is performed to reduce the amount of regenerative torque regenerated by the drive motor 1 based on the regenerative torque command correction value calculated in step S31, and the process proceeds to return. .

Next, the vehicle behavior control action during regenerative braking in the second embodiment will be described.
When regenerative cooperative brake control is performed and the tire lateral force ratio Fyr is within the threshold value Fyth, in the flowchart of FIG. 10, step S21 → step S22 → step S23 → step S24 → step S25 → step S26 → step S27 → step The flow from S28 → step S29 → step S30 → return is repeated. That is, in step S24, a steering angle correction command for correcting the actual steering angles of the front wheels and the rear wheels is output based on the calculated steering angle correction values of the front wheels and the rear wheels so as to compensate for disturbances in vehicle behavior. The rudder angle of at least one of the wheels is corrected.

  If it is determined that the vehicle behavior is still unstable and the tire lateral force ratio Fyr exceeds the threshold value Fyth regardless of the steering angle correction, from step S30 to step S31 → step in the flowchart of FIG. The flow from S32 to return is repeated. That is, if it is determined in step S30 that the vehicle behavior is unstable using the tire characteristic map shown in FIG. 12, a regenerative torque reduction allowance is calculated in step S31, and the regenerative torque is reduced in step S32. Control is performed.

Here, a method for determining whether or not the vehicle behavior performed using the tire characteristic map in step S30 is unstable will be described with reference to an example shown in FIG.
First, the tire characteristic map shown in FIG. 12 is divided into two regions, a regenerative torque restriction region and a regenerative torque non-restriction region, for the two axes of the tire slip ratio and the tire lateral force estimation value. Accordingly, in FIG. 14, when the estimated tire lateral force value at the instantaneous tire slip rate is A, it is determined that the tire can be generated without being saturated, and the regenerative torque is not reduced. On the other hand, when the estimated tire lateral force at the instantaneous tire slip ratio is B, the estimated tire lateral force is larger than the tire lateral force limit line that can be generated by the tire. By lowering the rate, the vehicle behavior is stabilized by shifting to C in a region where the tire lateral force can be generated.

  In the second embodiment, the regeneration torque is reduced by determining the regeneration reduction gain K with respect to the tire lateral force ratio Fyr as shown in FIG. In this way, by limiting the regeneration amount by the tire lateral force ratio Fyr, a rapid regeneration aperture can be suppressed and smooth correction can be performed. When the tire lateral force ratio Fyr changes abruptly, the tire lateral force ratio Fyr is shifted to a smaller side than the tire lateral force ratio Fyr at which the regeneration reduction gain K becomes 1 when it changes slowly. The threshold Fyth of the tire lateral force ratio Fyr is lowered. Therefore, it is possible to prevent the lateral force of the tire from suddenly entering the non-linear region and the vehicle behavior from being easily disturbed due to sudden steering. Since other operations are the same as those of the first embodiment, description thereof is omitted.

Next, the effect will be described.
In the electric vehicle control apparatus according to the second embodiment, the following effects can be obtained in addition to the effects (2) to (4) of the first embodiment.

(6) The vehicle behavior control means (vehicle controller 9, FIG. 10) determines a tire lateral force limit value based on a tire characteristic map (FIG. 12) indicating a lateral force characteristic that can be generated by the tire against a tire slip (step 12). S28) An estimated tire lateral force value at which a tire is actually generated is calculated (step S29), and a tire lateral force ratio Fyr which is a ratio of the tire lateral force estimated value to the tire lateral force limit value is calculated as the vehicle. The behavior disturbance index value is set (step S30).
For this reason, in a driving scene close to the limit region, the vehicle behavior compensation is easily performed by reducing the regenerative torque so that the vehicle behavior compensation can be started before the estimated tire lateral force value reaches the tire lateral force limit value. be able to.

(7) The vehicle behavior control means (vehicle controller 9, FIG. 10) decreases the threshold value Fyth of the tire lateral force ratio Fyr when the time change of the tire lateral force ratio Fyr is large (FIG. 13).
For this reason, in addition to the effect of (6) above, it is possible to prevent the lateral force of the tire from suddenly entering the non-linear region and the vehicle behavior from being easily disturbed in response to sudden steering.

  As mentioned above, although the control apparatus of the electric vehicle of this invention has been demonstrated based on Example 1, 2, it is not restricted to these Examples 1, 2 about a concrete structure, Each of Claims Design changes and additions are permitted without departing from the scope of the claimed invention.

  In Example 1, the yaw rate deviation Δγ is used as the vehicle behavior disorder index value, and in Example 2, the tire lateral force ratio Fyr is used as the vehicle behavior disorder index value. However, the vehicle behavior disturbance index value is not limited to these examples, and may be any index value that represents the disturbance amount or the predicted disturbance amount of the vehicle behavior. For example, instead of the yaw rate deviation Δγ of the first embodiment, an example using a lateral acceleration deviation as a vehicle behavior difference, an example using a composite value deviation of yaw rate and lateral acceleration, an example using a side slip angle deviation, etc. May be. Further, instead of the tire lateral force ratio Fyr of the second embodiment, an example using the difference between the maximum lateral force and the actual lateral force may be used.

  In the first and second embodiments, an example of a front-wheel drive electric vehicle (EV vehicle) is shown as the electric vehicle. However, it can be applied to other electric vehicles such as rear wheel drive electric vehicles (EV vehicles), front and rear wheel drive electric vehicles (EV vehicles), hybrid vehicles (HEV vehicles), fuel cell vehicles (FCV vehicles), etc. it can. That is, the present invention can be applied to any vehicle that is a vehicle that motor-drives at least one of the front wheels and the rear wheels, and is equipped with a steering control system that corrects the steering angle of at least one of the front wheels and the rear wheels.

DESCRIPTION OF SYMBOLS 1 Drive motor 2 Drive motor inverter 3 Secondary battery 4 Battery controller 5 Accelerator pedal 6 Accelerator opening sensor 7 Brake pedal 8 Brake stroke sensor 9 Vehicle controller (vehicle behavior control means)
10 Brake controller (regenerative cooperative brake control means)
DESCRIPTION OF SYMBOLS 11 Brake actuator 12 Master cylinder 13 Master cylinder pressure sensor 14 Wheel 15 Brake hydraulic system 16 Vehicle speed sensor 17 Steering angle sensor 18 Yaw rate sensor 19 Lateral G sensor 20 Wheel speed sensor 21 Motor controller (regenerative cooperative brake control means)
22 4WAS controller (steering angle correction steering control means)

Claims (7)

Regenerative cooperative brake control means for performing regenerative cooperative brake control for distributing the remaining braking torque, which is obtained by subtracting the regenerative torque generated by the motor-driven wheels from the total braking torque based on the brake operation, to the friction brake torque generated by the friction brakes of the front and rear wheels;
Steering angle correction steering control means for correcting the steering angle of at least one of the front and rear wheels so as to compensate for disturbance in vehicle behavior during the regenerative cooperative brake control;
Vehicle behavior control means for performing control to reduce the regenerative torque by the regenerative cooperative brake control means when it is determined that the vehicle behavior is still unstable after the steering angle correction by the steering angle correction steering control means;
An electric vehicle control device comprising: In the control device of the electric vehicle according to claim 1,
The vehicle behavior control means, after the steering angle correction by the steering angle correction steering control, the vehicle behavior disturbance index value representing the disturbance amount or the predicted disturbance amount of the vehicle behavior is a boundary region between the linear region and the nonlinear region of the tire lateral force A control device for an electric vehicle, characterized in that the vehicle behavior is determined to be unstable when a threshold value set to the value of is exceeded. In the control apparatus of the electric vehicle according to claim 2,
The control apparatus for an electric vehicle characterized in that the vehicle behavior control means increases the reduction range of the regenerative torque as the vehicle behavior disorder index value increases. In the control apparatus of the electric vehicle according to claim 2 or claim 3,
The control apparatus for an electric vehicle characterized in that the vehicle behavior control means increases a reduction range of the regenerative torque when a time change of the vehicle behavior disturbance index value is large. In the control apparatus for the electric vehicle according to any one of claims 2 to 4,
The electric vehicle control device, wherein the vehicle behavior control means uses a vehicle behavior difference between a vehicle behavior normative value and a vehicle actual behavior value as the vehicle behavior disturbance index value. In the control apparatus for the electric vehicle according to any one of claims 2 to 4,
The vehicle behavior control means determines a tire lateral force limit value based on a tire characteristic map indicating a lateral force characteristic that can be generated by a tire against tire slip, and calculates an estimated tire lateral force value that is actually generated by the tire. A control apparatus for an electric vehicle, wherein a tire lateral force ratio, which is a ratio of the tire lateral force estimated value to the tire lateral force limit value, is used as the vehicle behavior disorder index value. In the control apparatus of the electric vehicle according to claim 6,
The vehicle behavior control means reduces the threshold value of the tire lateral force ratio when the time variation of the tire lateral force ratio is large.