JP7222259B2 - VEHICLE WHEEL LOAD CONTROL METHOD AND WHEEL LOAD CONTROL DEVICE - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a wheel load control method and a wheel load control device for a vehicle that perform wheel load control of front and rear wheels by acceleration/deceleration.

In Patent Document 1, a target longitudinal force, a target lateral force, and a target yaw moment of a vehicle are calculated, control response frequency characteristics of steering control means and longitudinal force control means are calculated for each wheel, and proportional to the reciprocal of the characteristics. A weight to be applied is calculated, and the target slip ratio and target slip angle of each wheel are calculated by distribution control using an evaluation function using the weight. A vehicle running control device is disclosed that controls the steering angle of each wheel, the braking pressure, and the output torque of the engine so that the target slip ratio and target slip angle are achieved.

Patent Document 2 discloses a method for operating at least one of steering means for performing turning motion, accelerator means for changing the output of an engine that drives the drive wheels, and braking means for changing the braking force of the wheels. an actuator, a controller for controlling the actuator, and motion state detection means for detecting acceleration and jerk occurring in the vehicle. The controller receives the acceleration and jerk of the vehicle from the motion state detection means and negatively feeds back the acceleration of the vehicle to generate a control force or torque in the direction opposite to the acceleration to control the motion of the vehicle. , a control device is disclosed that positively feeds back the jerk of a vehicle to control the actuator based on the difference from a control force or torque that is generated in the same direction as the jerk and controls the motion of the vehicle. .

JP 2003-159966 A Japanese Patent No. 4020129

The technology disclosed in Patent Literature 1 performs integrated control using frequency-separated controllers so as to achieve a target longitudinal force, a target lateral force, and a target yaw moment. In other words, it only describes the control method and does not describe what the target should be. Therefore, although it is possible to improve the vehicle posture by targeting a specific frequency, it is not possible to uniform the overall turning characteristics.

The technique disclosed in Patent Literature 2 performs control to increase the front wheel load during steering to increase the steering response. Therefore, although it is effective for steering frequencies that are slightly slower than the normal steering input, the effective steering frequencies are limited to low frequency ranges.

The present disclosure has been made with a focus on the above problems, and aims to achieve good turning behavior in a wide range of steering frequencies from low to high frequencies in a scene where the vehicle attitude changes. do.

In order to achieve the above object, the present disclosure includes a controller that corrects drive torque from a drive source for running based on predetermined information and performs wheel load control by acceleration/deceleration. A vehicle wheel load control method by a controller has the following procedures.
Acquiring the required drive torque according to the driver's request or the system's request.
Information on the vehicle body slip angular velocity, which is the rate of change of the vehicle body slip angle formed by the vehicle body centerline and the vehicle traveling direction, is obtained.
A corrected drive torque is calculated by correcting the required drive torque according to the vehicle body slip angular velocity.
A wheel load control command for obtaining a corrected drive torque is output to the drive source for traveling.
A positive or negative correction sign is attached to the correction amount of the required drive torque according to the vehicle body slip angular velocity to calculate the torque correction amount, and the corrected drive torque is calculated by adding the torque correction amount to the required drive torque.
As for the correction sign, when the vehicle body slip angle changes away from zero, the sign of the torque correction amount is determined to be negative, and the required driving torque is corrected to the deceleration side.
As for the correction sign, when the vehicle body slip angle changes in the direction of approaching zero, the sign of the torque correction amount is determined to be positive, and the required drive torque is corrected on the acceleration side.

Therefore, in a scene in which the vehicle attitude changes, it is possible to achieve good turning behavior in a wide range of steering frequencies from low to high frequencies. In addition, in turning scenes where the vehicle body slip angle moves away from zero, changes in the vehicle body slip angle away from zero are suppressed by the quick response speed, achieving improved responsiveness that stabilizes the vehicle attitude. In a turning scene in which the vehicle body slip angle approaches zero, the response speed toward the zero vehicle body slip angle becomes slower, and the stability of the vehicle posture can be further improved.

1 is an overall system configuration diagram showing the system configuration of an electric vehicle to which the wheel load control method and wheel load control device of Example 1 are applied; FIG. 3 is a control block configuration diagram showing a control block configuration of a wheel load control unit configured by a wheel load control ECU and a drive motor ECU; FIG. 4 is a flowchart showing a flow of wheel load control processing by a wheel load control unit configured by a wheel load control ECU and a drive motor ECU; FIG. 4 is a schematic diagram showing a vehicle body slip angle and a vehicle body slip angular velocity in a four-wheeled vehicle; 4 is a block diagram showing torque correction amount calculation logic; FIG. FIG. 10 is a diagram for explaining the wheel load shifting action of the front and rear wheels when the drive torque is corrected on the deceleration side; FIG. 5 is a diagram for explaining the wheel load shifting action of the front and rear wheels when the driving torque is corrected on the acceleration side; FIG. 5 is a comparison characteristic diagram showing a comparison between the yaw rate gain frequency response characteristic and the yaw rate phase delay frequency response characteristic in the electric vehicle of Example 1 and the conventional electric vehicle; FIG. 7 is an overall system configuration diagram showing the system configuration of an automatically driven vehicle to which the wheel load control method and wheel load control device of Embodiment 2 are applied; FIG. 2 is a block configuration diagram showing control block configurations of an automatic driving controller and a vehicle motion controller;

Embodiments for implementing the vehicle wheel load control method and the wheel load control device according to the present disclosure will be described below based on a first embodiment and a second embodiment shown in the drawings.

The wheel load control method and the wheel load control device according to the first embodiment are applied to an electric vehicle (an example of a vehicle) manually operated by a driver. Hereinafter, the configuration of the first embodiment will be described by dividing it into "overall system configuration", "control block configuration of wheel load control unit", and "wheel load control processing configuration".

[Overall system configuration]
FIG. 1 shows the system configuration of an electric vehicle A1 to which the wheel load control method and wheel load control device of Example 1 are applied. The overall system configuration will be described based on FIG.

The electric vehicle A1, as shown in FIG. 1, is a front-wheel drive vehicle that includes a left front wheel 61L and a right front wheel 61R as driving wheels and a left rear wheel 62L and a right rear wheel 62R as driven wheels. Drive torque from a motor 63 (driving source for running) and a transmission 64 is input to the left front wheel 61L and the right front wheel 61R, which are drive wheels, via a left drive shaft 65L and a right drive shaft 65R, respectively.

As shown in FIG. 1, the left front wheel 61L and the right front wheel 61R of the electric vehicle A1 are not only drive wheels but also steered wheels that are steered by the driver's operation. As for the left front wheel 61L and the right front wheel 61R, when the driver inputs a steering input to the steering wheel 66, steering torque is input to the left and right front wheels 61L and 61R via the steering mechanism 67. FIG.

As a controller for driving and controlling the motor 63, as shown in FIG. 1, a wheel load control ECU 71 and a drive motor ECU 72 are provided. A wheel load control unit 7 is composed of the wheel load control ECU 71 and the drive motor ECU 72, and the wheel load control ECU 71 and the drive motor ECU 72 are connected by a two-way communication line 73 capable of exchanging information.

The wheel load control ECU 71 inputs information detected from the RL wheel speed sensor 74, the RR wheel speed sensor 75, the yaw rate sensor 76, the lateral acceleration sensor 77, etc., and calculates the vehicle body slip angular velocity based on the sensor input information. Then, a torque correction amount calculated based on the vehicle body slip angular velocity is added to the driver-requested drive torque acquired from the drive motor ECU 72 to calculate the corrected drive torque in the wheel load control.

Here, the RL wheel speed sensor 74 detects the left rear wheel speed Vrl. The RR wheel speed sensor 75 detects the right rear wheel speed Vrr. A yaw rate sensor 76 detects a yaw rate γ, which is a rotational angular velocity about a vertical axis passing through the center of gravity of the vehicle. The lateral acceleration sensor 77 detects lateral acceleration Gy, which is acceleration in a direction perpendicular to a plane perpendicular to the longitudinal direction of the vehicle when the vehicle turns. In the first embodiment, the wheel speed V obtained by averaging the left rear wheel speed Vrl and the right rear wheel speed Vrr is used as the information of the "vehicle speed V" and the "vehicle speed VSP".

The drive motor ECU 72 inputs information detected from the RL wheel speed sensor 74, the RR wheel speed sensor 75, the accelerator operation amount sensor 78, etc., and calculates the driver's requested drive torque based on the sensor input information. Then, either one of the driver-requested drive torque and the corrected drive torque acquired from the wheel load control ECU 71 is selected and output to the inverter 79 as a drive torque control command.

Here, the accelerator operation amount sensor 78 detects an accelerator operation amount APO representing the amount of depression of the accelerator pedal by the driver. When receiving a drive torque control command from the drive motor ECU 72, the inverter 79 converts the direct current from the battery 80 into a three-phase alternating current to the motor 63, and performs control to output the motor drive torque according to the control command.

[Control block configuration of wheel load control unit]
FIG. 2 shows a control block configuration of the wheel load control unit 7 (controller) composed of the wheel load control ECU 71 and the drive motor ECU 72 . The control block configuration of the wheel load control unit 7 will be described below with reference to FIG.

The wheel load control ECU 71 includes, as shown in FIG. and a drive torque calculator 715 .

A first vehicle speed condition determination unit 711 receives a vehicle speed V and determines whether or not the vehicle speed V exceeds a first vehicle speed set value VThresh1. If it is determined that V>VThresh1, the process proceeds to vehicle body slip angular velocity calculation section 712 . When it is determined that V≦VThresh1, a wheel load control non-operation flag for selecting the driver-requested driving torque as the driving torque is output to the driving torque selection unit 722 .

A vehicle body slip angular velocity calculation unit 712 (vehicle slip angular velocity information acquisition unit) obtains information on a vehicle body slip angular velocity β′, which is a rate of change in the vehicle body slip angle formed between the vehicle center line and the vehicle traveling direction, from the steering angle of the vehicle steering. Calculate an estimate. For example, in a system having a reference model for calculating a target slip angle from a steering angle of a vehicle, the posture of the vehicle is controlled by controlling the target slip angle. The change speed or deviation of this target slip angle is acquired as information of the vehicle body slip angular velocity β'. In addition, in a vehicle that has a driving support device that supports driving of the vehicle, or a vehicle that performs automatic driving, in a system that calculates the trajectory of the vehicle and controls it to follow the trajectory, instead of the steering angle of the steering wheel Alternatively, the trajectory calculated by the system or the curvature of the trajectory may be used to estimate the steering angle. Information on the vehicle body slip angular velocity β' may be estimated and calculated from the trajectory calculated by the system and the curvature of the trajectory. In addition, the wheel speed V, the yaw rate γ, and the lateral acceleration Gy are inputted, and the information of the vehicle body slip angular velocity β', which is the rate of change of the vehicle body slip angle formed by the vehicle center line and the vehicle traveling direction, is obtained by estimation calculation. may

A torque correction amount calculation unit 713 receives the vehicle body slip angular velocity β' from the vehicle body slip angular velocity calculation unit 712, and applies a positive or negative correction sign to the correction amount of the driver's requested driving torque Trq(D) according to the vehicle body slip angular velocity β'. Then, the torque correction amount Trq(add) is calculated.

A second vehicle speed condition determination unit 714 receives a vehicle speed V and determines whether or not the vehicle speed V exceeds a second vehicle speed set value VThresh2 (>VThresh1). If it is determined that V>VThresh2, the process proceeds to the correction driving torque calculation section 715. FIG. When it is determined that V≦VThresh2, a wheel load control non-operation flag for selecting the driver-requested driving torque as the driving torque is output to the driving torque selection unit 722 .

The corrected drive torque calculator 715 calculates the torque correction amount Trq(add) calculated by the torque correction amount calculator 713 and the driver requested drive torque Trq(D) calculated by the driver requested drive torque calculator 721. input. Then, the corrected drive torque Trq(c) is calculated by adding the torque correction amount Trq(add) to the driver requested drive torque Trq(D).

The drive motor ECU 72 includes, as shown in FIG.

A driver-requested drive torque calculation unit 721 receives the accelerator operation amount APO and the vehicle speed VSP, and obtains information by calculating information on the driver-requested drive torque Trq(D) according to the driver's accelerator operation amount APO and the vehicle speed VSP. Here, the information of the driver's requested drive torque Trq(D) may be obtained by searching the drive torque map using, for example, a drive torque map preset using the accelerator operation amount APO and the vehicle speed V as parameters. Further, the information of the driver requested drive torque Trq(D) is always calculated unlike the torque correction amount Trq(add) calculated when the first vehicle speed condition is established.

Drive torque selector 722 inputs corrected drive torque Trq(c) from corrected drive torque calculator 715 and driver requested drive torque Trq(D) from driver requested drive torque calculator 721 . Then, when the wheel load control non-operation flag is input from the first vehicle speed condition determination unit 711 or the second vehicle speed condition determination unit 714, the driver requested driving torque Trq(D) is selected as the driving torque. On the other hand, when the wheel load control non-operation flag is not input from the first vehicle speed condition determination unit 711 or the second vehicle speed condition determination unit 714, that is, the scene where the vehicle speed V exceeds the second vehicle speed set value VThresh2. Then, the corrected drive torque Trq(c) is selected as the drive torque.

Control output unit 723 outputs a drive control command for obtaining driver-requested drive torque Trq(D) to inverter 79 when driver-requested drive torque Trq(D) is selected by drive torque selection unit 722 . On the other hand, when the drive torque selector 722 selects the corrected drive torque Trq(c), it outputs to the inverter 79 a wheel load control command for obtaining the corrected drive torque Trq(c).

[Wheel load control processing configuration]
FIG. 3 shows the flow of wheel load control processing by the wheel load control unit 7 (controller) composed of the wheel load control ECU 71 and the drive motor ECU 72 . Each step in FIG. 3 representing the wheel load control processing configuration will be described below.

In step S1, following the start, the wheel speed V is detected. In step S2, the yaw rate γ is detected. In step S3, the lateral acceleration Gy is detected. In step S4, the accelerator operation amount APO is detected.

In step S5, following the detection of the accelerator operation amount APO in step S4, the driver's required drive torque Trq(D) is calculated according to the accelerator operation amount APO and the vehicle speed VSP, and the process proceeds to step S6.

In step S6, following the calculation of the driver-requested drive torque Trq(D) in step S5, it is determined whether or not the vehicle speed V at that time exceeds a preset first vehicle speed set value VThresh1. If YES (VThresh1<V), go to step S7, and if NO (VThresh1≧V), go to step S11.

Here, the "first vehicle body speed set value VThresh1" is set to a vehicle body speed lower limit value that prevents erroneous estimation of the vehicle body slip angular velocity β' estimated and calculated based on the wheel speed V, the yaw rate γ, and the lateral acceleration Gy. . That is, when obtaining the vehicle body slip angular velocity β' by estimation calculation, the vehicle body speed condition is that the vehicle body speed V exceeds the first vehicle body speed set value VThresh1. In other words, the vehicle body slip angular velocity β' is not estimated and calculated in the low vehicle speed range where the vehicle body speed V is equal to or lower than the first vehicle body speed set value VThresh1.

In step S7, following the judgment that VThresh1<V in step S6, when VThresh1<V, the vehicle body slip angular velocity β' is estimated from the wheel speed V, yaw rate γ, and lateral acceleration Gy, and the process proceeds to step S8. .

Here, the vehicle body slip angular velocity β' is, for example,
(Car body slip angular velocity β') = (Yaw rate γ) - (Lateral acceleration Gy) / (Wheel velocity V)
It is estimated and calculated using the formula of As a method for estimating the vehicle body slip angular velocity β', it is possible to estimate using various methods other than the calculation using the above-described well-known formula.

As shown in FIG. 4, the "vehicle body slip angle β" is the angle formed by the center line of the vehicle in the longitudinal direction of the vehicle passing through the center of gravity of the vehicle and the instantaneous traveling direction of the vehicle starting from the center of gravity of the vehicle. Say. The "vehicle slip angular velocity β'" is the amount of change in the vehicle body slip angle β per unit time when the vehicle body slip angle β increases or decreases. Therefore, when traveling on a curved road, the vehicle behavior and the vehicle body center line (β = 0) increase in the vehicle body slip angle β in the direction (arrow B direction in FIG. 4) away from the vehicle body center line (β = 0). 4 shows vehicle behavior in which the vehicle body slip angle β decreases in the direction of approaching (the direction of arrow C in FIG. 4).

In step S8, following the calculation of the vehicle body slip angular velocity β' in step S7, a torque correction amount Trq(add) corresponding to the absolute value |β'| of the vehicle body slip angular velocity β' is calculated, and the process proceeds to step S9.

Here, the "torque correction amount Trq(add)" is the correction amount of the driver's requested driving torque Trq(D), and the vehicle body slip angular velocity absolute value |β'| is calculated by adding a positive or negative correction sign to .

The correction sign determination unit of the torque correction amount calculation logic determines the correction sign using the vehicle body slip angle β and the vehicle body slip angular velocity β' obtained by integral calculation of the vehicle body slip angular velocity β'. As for the correction sign, when the vehicle body slip angle β changes toward zero, the sign of the torque correction amount Trq(add) is determined to be positive, and the driver's requested drive torque Trq(D) is corrected to the acceleration side. On the other hand, as for the correction sign, when the vehicle body slip angle β changes away from zero, the sign of the torque correction amount Trq(add) is determined to be negative, and the driver's requested drive torque Trq(D) is corrected to the deceleration side.

The torque correction amount Trq(add) is obtained by multiplying the absolute value |β'| of the vehicle body slip angular velocity β' by the coefficient K using the formula Trq(add)=K×|β'| Calculate a value proportional to the magnitude of |β'|. A front/rear G limit value (for example, about ±0.01 G) is set to suppress the front/rear G generated by the correction of the driver's requested driving torque Trq(D) to a level that the vehicle occupants do not perceive. When the torque correction amount Trq(add) exceeds the upper limit correction amount that becomes the front/rear G limit value, a value limited by the upper limit correction amount is calculated.

In step S9, following the calculation of the torque correction amount Trq(add) in step S8, it is determined whether or not the vehicle speed V at that time exceeds a preset second vehicle speed set value VThresh2 (>VThresh1). to decide. If YES (VThresh2<V), proceed to step S10. If NO (VThresh2≧V), proceed to step S11.

Here, the "second vehicle body speed set value VThresh2" is set to the vehicle body speed lower limit value at which the torque correction amount Trq(add) becomes a stable value without variations. That is, when starting wheel load control in which the torque correction amount Trq(add) is added to the driver-requested driving torque Trq(D), the vehicle speed V is set to the second vehicle speed setting value VThresh2 higher than the first vehicle speed setting value VThresh1. The vehicle body speed condition is that the vehicle speed is exceeded. In other words, wheel load control using the corrected driving torque Trq(c) is not performed in the low vehicle speed range where the vehicle speed V is equal to or lower than the second vehicle speed set value VThresh2.

In step S10, following the determination that VThresh2<V in step S9, when VThresh2<V, the driver required drive torque Trq(D) is added with the torque correction amount Trq(add) to obtain the corrected drive torque Trq( c) is calculated, and the process proceeds to step S11.

In step S11, following the determination of NO in step S6 or step S9, motor drive control is executed to obtain the driver's requested drive torque Trq(D), and the process proceeds to the end. On the other hand, when the corrected drive torque Trq(c) is calculated in step S10, the motor drive control for obtaining the corrected drive torque Trq(c) is executed, and the process proceeds to END.

Next, "Background technology and problem-solving measures" will be explained. Then, the "wheel load control action" of the first embodiment will be described.

[Background technology and problem-solving measures]
G-Vectoring Control (hereinafter referred to as "GVC") is known as a background technology for wheel load control. GVC focuses on the steering angle of the driver's steering wheel in order to maximize the tire's performance in response to the driver's steering wheel operation. It is a technique to perform

For example, the moment the driver starts to turn the steering wheel, the drive torque of the engine is controlled to decrease to generate the deceleration G, and the load is transferred to the front wheels. This increases the tire grip of the front wheels and improves the responsiveness of the vehicle. After that, when the driver holds the steering wheel at a constant steering angle, the driving torque of the engine is instantly restored and the load is transferred to the rear wheels, thereby improving the stability of the vehicle. This series of load transfers draws out the grip of the front and rear wheels, and enhances the responsiveness and stability of the vehicle according to the driver's intentions.

However, GVC reflects the steering angle of the steering wheel (= driver's steering operation) in wheel load control, and is effective for a low frequency range due to steering input that is slightly slower than normal steering input. However, since the steering angle of the steering wheel is used as input information, it is less effective in the high frequency range due to faster steering input than normal steering input. In other words, in the case of GVC, in the yaw rate frequency response characteristic, the yaw rate gain decreases in the high frequency range, and the yaw rate phase lags in the high frequency range. There was a problem that it was limited to a low frequency range.

In response to such background art, in a scene where the vehicle posture changes, instead of increasing the responsiveness and stability of the vehicle only in a specific low frequency range, it is necessary to align the overall steering frequency characteristics up to the high frequency range. I want to provide ease of handling. In addition, there is a demand for attitude control that cannot be determined by changes in turning G.

Therefore, the inventors of the present invention consider that it is important to stabilize the vehicle posture more quickly in a scene where the vehicle posture changes. ). Then, wheel load control using the vehicle body slip angular velocity β' as input information was realized. That is, the corrected driving torque Trq(c) is calculated by correcting the driver's requested driving torque Trq(D) according to the acquired vehicle body slip angular velocity β'. A method of controlling the wheel load by outputting to the motor 63 a wheel load control command for obtaining the corrected driving torque Trq(c) is adopted.

The wheel load control mechanism is
・ The steady-state turning characteristics are mainly due to the performance of the rear tires, and the transient characteristics are due to the performance of the front tires.
・ The transient/steady state of turning can be determined by observing the change in the body slip angular velocity β'.
・By increasing the wheel load, it is possible to secure the gripping force that the tire produces.
That is the point.

Based on the above mechanism, the vehicle behavior (= vehicle body slip angle β) rather than the steering operation is used to distinguish steady state/transient and its degree, and the wheel load shift changes the front-rear balance of tire grip characteristics.

Therefore, by using the vehicle body slip angular velocity β' as input information and performing wheel load control that reflects the vehicle body slip angular velocity β' (=vehicle behavior), it is possible to execute wheel load control before the vehicle behavior changes significantly. (Transitional period control). In other words, it becomes possible to execute control corresponding to changes in vehicle behavior (=vehicle body slip angular velocity β') of high-frequency components. As a result, appropriate wheel load control can be executed before the behavior of the vehicle changes significantly. By stabilizing the vehicle behavior in this manner, the turning performance of the electric vehicle A1 can be improved.

For example, when the driver turns the steering wheel at the entrance of a curved road and the vehicle body slip angle β changes away from zero, the transient state occurs, and at that moment, the driving torque of the motor 63 is corrected to the decreasing side to generate the deceleration G. Then, the load is transferred to the left and right front wheels 61L, 61R. As a result, as shown in FIG. 6, the tire gripping force of the left and right front wheels 61L, 61R is increased, the increase in the vehicle body slip angular velocity β' is suppressed, and the responsiveness for stabilizing the vehicle behavior is improved.

After that, when the driver holds the steering wheel at a constant steering angle and the vehicle body slip angular velocity β' changes in the direction of approaching zero, at that moment, the acceleration G is generated by the acceleration side correction of the driving torque of the motor 63. Then, the load is transferred to the left and right rear wheels 62L, 62R. As a result, as shown in FIG. 7, the tire gripping force of the left and right rear wheels 62L, 62R is increased, the speed at which the vehicle body slip angle β approaches zero is suppressed, and the stability of vehicle behavior is improved.

When the vehicle body slip angular velocity β' becomes zero and changes in the vehicle body slip angle β are stopped, the torque correction amount Trq(add) is also made zero from that moment, and the wheel load control is not performed. Therefore, stable vehicle behavior is maintained while maintaining a steady turning state.

Next, when the driver returns the steering wheel at the exit of the curved road and the vehicle body slip angle β changes in the direction away from zero, at that moment the deceleration G is reduced by correcting the driving torque of the motor 63 to the decreasing side. It is generated and the load is transferred to the left and right front wheels 61L and 61R. As a result, as shown in FIG. 6, the tire grip of the left and right front wheels 61L, 61R is increased to suppress the increase in the vehicle body slip angular velocity β', thereby improving the responsiveness for stabilizing the vehicle behavior.

After that, when the driver holds the steering wheel at the neutral steering angle and the vehicle body slip angular velocity β' changes in the direction of approaching zero, at that moment, acceleration G is generated by the acceleration side correction of the driving torque of the motor 63. Then, the load is transferred to the left and right rear wheels 62L, 62R. As a result, as shown in FIG. 7, the tire grip of the left and right rear wheels 62L, 62R is increased, the speed at which the vehicle body slip angle β approaches zero is suppressed, and the stability of vehicle behavior is improved.

This series of wheel load shifting actions draws out the gripping force of the front and rear tires so as to stabilize the vehicle behavior (= vehicle body slip angular velocity β') in turning scenes, realizing turning characteristics that are easy for the driver to drive. be done.

As described above, by performing wheel load control using the vehicle body slip angular velocity β' as input information, in a scene where the vehicle attitude changes, good turning behavior can be achieved in a wide frequency range from low to high steering frequencies. can be realized. The fact that good turning behavior can be achieved in this wide frequency range is due to the yaw rate frequency response characteristics of the electric vehicle A1 (solid line characteristic) of Example 1 and the conventional electric vehicle (broken line characteristic) shown in FIG. supported by comparison.

In other words, as shown in the yaw rate gain frequency response characteristics (upper part of FIG. 8), the dashed line characteristic shows the resonance peak of the yaw rate gain at a steering frequency slightly higher than 2 Hz, while the solid line characteristic shows arrow D in FIG. , the resonance peak is suppressed. Also, as shown in the yaw rate gain frequency response characteristic (upper part of FIG. 8), the dashed line characteristic shows that the yaw rate gain drops steeply in the high frequency range above the steering frequency at the resonance peak, while the solid line characteristic A decrease in the yaw rate gain in the area is suppressed. That is, as indicated by arrow E in FIG. 8, the high frequency response is improved in the yaw rate gain frequency response characteristic. In addition, in the solid line characteristic, as indicated by the arrow F in the yaw rate gain frequency response characteristic (upper part of FIG. 8), the yaw rate gain characteristic difference in the entire frequency range from low steering frequency to high steering frequency is reduced, Overall frequency response characteristics are aligned up to high frequencies.

Furthermore, as shown in the yaw rate phase delay frequency response characteristic (lower part of FIG. 8), in the dashed line characteristic, the yaw rate phase delay increases as the steering frequency increases, whereas in the solid line characteristic, the yaw rate phase delay is larger than that of the dashed line characteristic. kept small. That is, as indicated by arrow G in FIG. 8, the high frequency response is improved in the yaw rate phase lag frequency response characteristic. In this way, by suppressing the resonance peak and improving the high-frequency response, the entire frequency range from a low steering frequency to a high steering frequency, in other words, the steering speed when the tires of the left and right front wheels 61L and 61R are steered (=steering Good turning behavior is achieved regardless of whether the frequency is high or low.

[Wheel load control action]
First, the operation of the wheel load control processing will be described with reference to the flowchart of FIG. →S6→S11→End is repeated.

Therefore, when traveling in a low vehicle speed range where the first vehicle speed condition is not satisfied, the driver's requested drive torque Trq(D) is calculated in S5 according to the accelerator operation amount APO and the vehicle speed VSP. Then, in S11, motor drive control is executed to obtain the driver requested drive torque Trq(D).

Further, when the vehicle body speed V exceeds the first vehicle body speed set value VThresh1 but is equal to or less than the second vehicle body speed set value VThresh2, S1→S2→S3→S4→S5→S6→ The flow of S7->S8->S9->S11->End is repeated.

Therefore, when traveling in a low vehicle speed range where the first vehicle speed condition is satisfied but the second vehicle speed condition is not satisfied, in S5, the driver required drive torque Trq( D) is calculated. In S7, the vehicle body slip angular velocity β' is estimated and calculated from the wheel speed V, yaw rate γ, and lateral acceleration Gy. In S8, the torque correction amount Trq(add ) is calculated. However, in S11, motor drive control is executed to obtain the driver requested drive torque Trq(D).

On the other hand, when the vehicle body speed V exceeds the second vehicle body speed set value VThresh2, in the flow chart of FIG. The flow is repeated.

Therefore, when traveling in a vehicle speed range where both the first vehicle speed condition and the second vehicle speed condition are satisfied, in S5, the driver's required driving torque Trq(D) is calculated according to the accelerator operation amount APO and the vehicle speed VSP. . In S7, the vehicle body slip angular velocity β' is estimated and calculated from the wheel speed V, the yaw rate γ, and the lateral acceleration Gy, and in S8, the torque correction amount Trq(add) corresponding to the absolute value |β'| Calculated. Then, in S10, the corrected drive torque Trq(c) is calculated by adding the torque correction amount Trq(add) to the driver requested drive torque Trq(D). Therefore, wheel load control is executed by motor drive to obtain the corrected drive torque Trq(c).

Thus, when the wheel load control is executed, if the vehicle body slip angle β changes away from zero, it is determined in S8 that the correction sign of the torque correction amount Trq(add) is negative, and the driver requested driving torque Trq (D) is deceleration side correction. Therefore, when the vehicle body slip angle β changes away from zero on the entrance side of the curved road, the wheel load shifts to the left and right front wheels 61L, 61R. Therefore, in a turning scene where the vehicle body slip angle β moves away from zero, the change in the direction away from zero is suppressed by a quick response speed, and the responsiveness is improved to stabilize the vehicle attitude. achieved.

On the other hand, when the vehicle body slip angle β changes toward zero, it is determined in S8 that the correction sign of the torque correction amount Trq(add) is positive, and the driver's requested drive torque Trq(D) is corrected to the acceleration side. . Therefore, when the vehicle body slip angle β changes toward zero on the exit side of the curved road, the wheel load shifts to the left and right rear wheels 62L, 62R. Therefore, in a turning scene in which the vehicle body slip angle β approaches zero, the response speed for moving the vehicle body slip angle β to zero is slowed down, and the stability of the vehicle posture is further improved.

When the wheel load control is executed, the torque correction amount Trq(add) is calculated as a value proportional to the magnitude of the absolute value |β'| of the vehicle body slip angular velocity β'. Therefore, the amount of movement of the wheel load by the wheel load control, which is proportional to the torque correction amount Trq(add), corresponds to the change speed of the vehicle behavior represented by the magnitude of the vehicle body slip angular velocity absolute value |β'|. Become. Therefore, excess or deficiency of the torque correction amount Trq(add) in the wheel load control is suppressed, and the wheel load control is executed with an appropriate torque correction amount Trq(add), thereby turning according to changes in the turning state. Performance is improved.

When the wheel load control is executed, the torque correction amount Trq(add) is set to a value limited by the upper limit correction amount when the torque correction amount Trq(add) exceeds the upper limit correction amount that becomes the front/rear G limit value. At this time, the longitudinal G limit value is set to suppress the longitudinal G generated by the correction of the driver's requested driving torque Trq(D) to such an extent that the vehicle occupants do not perceive it. Therefore, even if the wheel load control is executed by adding or subtracting the torque correction amount Trq(add) to the driver-requested drive torque Trq(D), turning performance is improved while suppressing discomfort given to the driver and fellow passengers. be able to.

In the first embodiment, when the information of the vehicle body slip angular velocity β' is obtained by estimation calculation, the vehicle body speed condition is that the vehicle body speed V exceeds the first vehicle body speed set value VThresh1. When the wheel load control for adding the torque correction amount Trq(add) to the driver requested drive torque Trq(D) is started, the vehicle speed V is set to the second vehicle speed set value VThresh2 higher than the first vehicle speed set value VThresh1. The vehicle body speed condition is that the vehicle speed is exceeded. Therefore, the calculation of the vehicle body slip angular velocity β' is stopped in the vehicle speed range where the estimated accuracy of the vehicle body slip angular velocity β' is low, and the wheel load control is stopped in the vehicle speed range where the torque correction amount Trq(add) is not stable. Therefore, the information of the vehicle body slip angular velocity β' can be obtained with high accuracy, and the wheel load control for adding the torque correction amount Trq(add) can be properly executed.

In the first embodiment, the vehicle is an electric vehicle A1 that is operated by the driver, and the required driving torque is the driver's required driving torque Trq(D) corresponding to the accelerator operation amount APO by the driver and the vehicle speed VSP. Therefore, when the driver operates the steering wheel, the wheel load is controlled by accelerating and decelerating so that the steady state is stabilized more quickly. Therefore, in a scene of traveling on a curved road, a turning characteristic that is easy for the driver to drive is realized, and correction steering by the driver is reduced.

As described above, the wheel load control method and the wheel load control device for the electric vehicle A1 of the first embodiment have the following effects.

(1) The wheel load of the vehicle (electric vehicle A1) by the controller (wheel load control unit 7) that corrects the driving torque from the driving source (motor 63) based on predetermined information and controls the wheel load by acceleration/deceleration. In the control method,
Acquiring information on the required driving torque according to the driver's request or system's request,
Acquiring information on a vehicle body slip angular velocity β', which is a rate of change of the vehicle body slip angle β formed by the vehicle body center line and the vehicle traveling direction,
A corrected drive torque Trq(c) is calculated by correcting the required drive torque (driver required drive torque Trq(D)) according to the vehicle body slip angular velocity β',
A wheel load control command for obtaining the corrected driving torque Trq(c) is output to the driving source (motor 63) (FIG. 2).
Therefore, it is desirable to provide a wheel load control method for a vehicle (electric vehicle A1) that achieves good turning behavior in a wide range of steering frequencies from low to high in a scene where the vehicle attitude changes. can.

(2) When the vehicle body slip angle β increases, the corrected drive torque Trq(c) is calculated so as to correct to the deceleration side, and when the vehicle body slip angle β decreases, the corrected drive torque is calculated to make the correction to the acceleration side. Calculate Trq(c) (Fig. 2).
Therefore, in a scene where the vehicle attitude changes, the corrected driving torque Trq(c) that realizes good turning behavior can be calculated based on the increase or decrease in the vehicle body slip angle β.

(3) Calculate the torque correction amount Trq(add) by adding a positive or negative correction sign to the correction amount of the required driving torque (driver's required driving torque Trq(D)) according to the vehicle body slip angular velocity β', and calculate the required driving torque. The corrected drive torque Trq(c) is calculated by adding the torque correction amount Trq(add) to (driver requested drive torque Trq(D)) (FIG. 2).
For this reason, in a scene where the vehicle attitude changes, a torque correction amount Trq(add) with a positive or negative correction sign is added to the base required driving torque (driver's required driving torque Trq(D)). Torque Trq(c) can be calculated.

(4) As for the correction sign, when the vehicle body slip angle β changes away from zero, the sign of the torque correction amount Trq(add) is determined to be negative, and the required drive torque (driver required drive torque Trq(D)) is corrected. Deceleration side correction is applied (Figs. 4 and 6).
Therefore, in turning scenes where the vehicle body slip angle β moves away from zero, changes in the direction away from zero are suppressed by the quick response speed, improving the responsiveness of stabilizing the vehicle attitude. can be achieved.

(5) As for the correction sign, when the vehicle body slip angle β changes toward zero, the sign of the torque correction amount Trq(add) is determined to be positive, and the required drive torque (driver required drive torque Trq(D)) is determined. to the acceleration side correction (Figs. 4 and 7).
Therefore, in a turning scene in which the vehicle body slip angle β approaches zero, the response speed of the vehicle body slip angle β tends to zero, and the stability of the vehicle posture can be further improved.

(6) The torque correction amount Trq(add) for the required driving torque (driver's required driving torque Trq(D)) is calculated from a value proportional to the absolute value |β'| of the vehicle body slip angular velocity β' (Fig. 5).
Therefore, excess or deficiency of the torque correction amount Trq(add) in the wheel load control is suppressed, and the wheel load control is executed with an appropriate torque correction amount Trq(add), thereby turning according to changes in the turning state. It can improve performance.

(7) setting a longitudinal G limit value that suppresses the longitudinal G generated by correcting the required drive torque (driver required drive torque Trq(D)) to a level that is not perceived by vehicle occupants;
When the torque correction amount Trq(add) of the required driving torque (driver's required driving torque Trq(D)) exceeds the upper limit correction amount that becomes the front/rear G limit value, it is set to a value limited by the upper limit correction amount (Fig. 5). .
Therefore, even if wheel load control is executed by adding or subtracting the torque correction amount Trq(add) to or from the required driving torque (driver's required driving torque Trq(D)), it is possible to suppress discomfort given to the driver and fellow passengers. Turning performance can be improved.

(8) When obtaining information on the vehicle body slip angular velocity β' by estimation calculation, the vehicle body speed condition is that the vehicle body speed V exceeds the first vehicle body speed set value VThresh1,
When starting the wheel load control that adds the torque correction amount Trq(add) to the required drive torque (driver required drive torque Trq(D)), the second vehicle speed setting is such that the vehicle speed V is higher than the first vehicle speed set value VThresh1. The vehicle speed condition is defined as exceeding the value VThresh2 (Fig. 3).
Therefore, the information of the vehicle body slip angular velocity β' can be obtained with high accuracy, and the wheel load control for adding the torque correction amount Trq(add) can be appropriately executed.

(9) The vehicle is a manual driving vehicle (electric vehicle A1) that is operated by the driver,
The required driving torque is the driver required driving torque Trq(D) corresponding to the accelerator operation amount APO by the driver and the vehicle speed VSP (Fig. 1).
Therefore, in a scene where the vehicle travels on a curved road, turning characteristics that are easy for the driver to drive can be realized, and correction steering by the driver can be reduced.

(10) Wheels of a vehicle (electric vehicle A1) equipped with a controller (wheel load control unit 7) that corrects the driving torque from the drive source (motor 63) based on predetermined information and controls the wheel load by acceleration/deceleration. In the load controller,
The controller (wheel load control unit 7)
a required driving torque acquisition unit (driver required driving torque calculation unit 721) that acquires information on the required driving torque according to a driver request or a system request;
a vehicle body slip angular velocity information acquisition unit (vehicle slip angular velocity calculation unit 712) that acquires information on a vehicle body slip angular velocity β', which is the rate of change in the vehicle body slip angle β formed by the vehicle body centerline and the vehicle traveling direction;
a corrected drive torque calculation unit 715 that calculates a corrected drive torque Trq(c) by correcting the required drive torque (driver required drive torque Trq(D)) according to the vehicle body slip angular velocity β′;
a control output unit 723 for outputting a wheel load control command for obtaining the corrected drive torque Trq(c) to the drive source for running (motor 63);
(Fig. 2).
Therefore, it is desirable to provide a wheel load control device for a vehicle (electric vehicle A1) that achieves good turning behavior in a wide range of steering frequencies from low to high in a scene where the vehicle attitude changes. can.

Embodiment 2 is an example in which the wheel load control method and the wheel load control device of the present invention are applied to an automatically driving vehicle.

In the wheel load control method and wheel load control device of the second embodiment, when the automatic driving mode is selected, a target trajectory is generated, and vehicle motion is controlled by speed and steering angle so that the vehicle travels along the generated target trajectory. It is applied to an automatic driving vehicle (an example of a vehicle). Hereinafter, the configuration of the first embodiment will be described by dividing it into "overall system configuration", "control block configuration of automatic driving controller", and "control block configuration of vehicle motion controller".

[Overall system configuration]
FIG. 9 shows the system configuration of an automatic driving vehicle A2 to which the wheel load control method and wheel load control device of the second embodiment are applied. The overall system configuration will be described based on FIG.

The automatic driving vehicle A2 includes an in-vehicle sensor 1, a navigation device 2, an in-vehicle control unit 3, an actuator 4, and an HMI module 5, as shown in FIG.

The in-vehicle sensor 1 is various sensors mounted on the vehicle for recognizing objects around the vehicle, the surrounding environment such as the shape of the road, the state of the vehicle, and the like. This in-vehicle sensor 1 has an external sensor 11 , a GPS receiver 12 and an internal sensor 13 . Note that the in-vehicle sensor 1 may perform sensor fusion to acquire necessary information using a plurality of different sensors.

The external sensor 11 is a detection device that detects environmental information around the vehicle. The external sensor 11 is composed of a camera, a radar, a LIDER (Laser Imaging Detection and Rangin), and the like. It should be noted that the cameras, radars and lidars do not necessarily have to be duplicated.

A camera is imaging equipment for acquiring image data. This camera, for example, is configured by combining a front recognition camera, a rear recognition camera, a right recognition camera, a left recognition camera, etc., and analyzes the captured images and videos in real time using artificial intelligence and image processing processors. do in As a result, the camera can detect objects on the road on which the vehicle is traveling, lanes, objects outside the vehicle's traveling road (road structures, preceding vehicles, following vehicles, oncoming vehicles, surrounding vehicles, pedestrians, bicycles, motorcycles), and the vehicle's traveling road ( It can detect road white lines, road boundaries, stop lines, crosswalks), road signs (speed limits), etc. Although a monocular camera cannot generally measure the distance to an object, it is possible to measure the distance to an object by simultaneously taking pictures from different viewpoints using a compound eye camera.

Radar is a device that uses reflected signals to obtain range data. Here, "radar" is a general term including radar using radio waves and sonar using ultrasonic waves. For example, laser radar, millimeter wave radar, ultrasonic radar, laser range finder, etc. can be done. A lidar is a device that acquires distance data using light.

Radars and lidars transmit signals such as radio waves and light around the vehicle, and by receiving signals such as radio waves and light reflected by the target, determine the distance and direction to the target, which is the reflection point. To detect. As a result, radar and lidar can detect the position of objects on and off the road on which the vehicle is traveling (road structures, preceding vehicles, following vehicles, oncoming vehicles, surrounding vehicles, pedestrians, bicycles, and motorcycles). In addition, the distance to each object can be detected.

The GPS receiver 12 is a device for receiving signals from three or more GPS satellites and acquiring position data indicating the position of the vehicle. This GPS receiver 12 has a GNSS antenna 12a and detects the latitude and longitude of the vehicle position.
"GNSS" is an abbreviation for "Global Navigation Satellite System", and "GPS" is an abbreviation for "Global Positioning System". Also, when signal reception by the GPS receiver 12 is poor, the function of the GPS receiver 12 may be complemented by using the internal sensor 13 or an odometer (vehicle movement amount measuring device).

The internal sensor 13 is a detection device that detects own vehicle information such as speed, acceleration, and attitude data of the own vehicle. This internal sensor 13 has, for example, a 6-axis inertial sensor (IMU: Inertial Measurement Unit), and can detect the movement direction, orientation, and rotation of the vehicle. Furthermore, based on the detection result of the internal sensor 13, the moving distance, moving speed, etc. can be calculated. A 6-axis inertial sensor is realized by combining an acceleration sensor capable of detecting acceleration in three directions (back and forth, left and right, and up and down) and a gyro sensor capable of detecting rotational speed in these three directions. The internal sensor 13 can include necessary sensors such as a wheel speed sensor, a yaw rate sensor, an accelerator operation amount sensor, and the like.

Further, the in-vehicle sensor 1 may acquire necessary information from the outside by performing wireless communication with an external data communication device (not shown). That is, when the external data communication device is, for example, a data communication device mounted on another vehicle, vehicle-to-vehicle communication is performed between the own vehicle and the other vehicle. Through this inter-vehicle communication, necessary information can be acquired from various information held by other vehicles. Further, when the external data communication device is, for example, a data communication device provided in infrastructure equipment, infrastructure communication is performed between the vehicle and the infrastructure equipment. Through this infrastructure communication, necessary information can be acquired from various information held by the infrastructure equipment. As a result, for example, when there is insufficient information or changed information in the map data possessed by the automatic driving controller 31, necessary map data can be supplemented. It is also possible to acquire traffic information such as congestion information and travel regulation information on the route on which the own vehicle is scheduled to travel.

The navigation device 2 is a device that incorporates map data and facility information data and guides a route to a destination. When a destination is input, the navigation device 2 generates a guidance route from the current location of the vehicle (or an arbitrarily set starting point) to the destination. Information on the generated guidance route is displayed on the display panel of the HMI module 5 after being combined with the map data. The destination may be set by the occupant of the vehicle in the vehicle, or the destination set by the user using the user's terminal (eg, mobile phone, smartphone) is received by the vehicle via wireless communication. and may use the received destination. Further, the guidance route may be calculated by a navigation device using a controller provided in the vehicle, or may be calculated by a navigation device using a controller outside the vehicle.

The in-vehicle control unit 3 includes a CPU and a memory, and stores various detection information detected by the in-vehicle sensor 1, guidance route information generated by the navigation device 2, and driver input information appropriately input as necessary. Integrated processing. The vehicle-mounted control unit 3 is a controller that controls vehicle motion by hierarchical processing. Note that "hierarchical processing" refers to the process of sequentially (hierarchically) executing multiple processes on input information to calculate the final output information. (calculated value) becomes the input value in the processing of the lower layer.

The in-vehicle control unit 3 has an automatic driving controller 31 that calculates a control command value for controlling vehicle motion, and a vehicle motion controller 32 . Here, the automatic operation controller 31 that performs calculations in the first control period (for example, about 70 msec) performs upper layer processing, and calculates in the second control period (for example, about 10 msec) that is shorter than the first control period. The vehicle motion controller 32 that performs the lower layer processing is performed.

The automatic driving controller 31 generates a target vehicle speed profile and a target trajectory through multistage hierarchical processing based on input information from the in-vehicle sensor 1 and the navigation device 2, high-precision map data, and the like. Here, the "target trajectory" is a trajectory that is a target when the vehicle is driven automatically. , including the trajectory for traveling within the travelable area and the trajectory during emergency steering for avoiding obstacles. Information on the generated target vehicle speed profile and target trajectory is output to the vehicle motion controller 32 . Information on the generated target trajectory may be combined with high-precision map data and displayed on the display panel of the HMI module 5 .

The vehicle motion controller 32 calculates a control command value for driving the own vehicle by multi-stage hierarchical processing based on information on the target vehicle speed profile and target trajectory and information input by the driver (hereinafter referred to as "driver input"). . The calculated control command value is output to the actuator 4 . The vehicle motion controller 32 arbitrates the driving mode depending on the presence or absence of driver input, and calculates a control command value according to the arbitration result. For example, when the automatic driving mode is selected and there is no driver input, a control command value for automatically driving the own vehicle along the target trajectory is output. On the other hand, when the driver input intervenes during automatic driving or when the manual driving mode is selected, the control command value for driving the own vehicle is output with the driver input as the target.

The actuator 4 is a control actuator for running or stopping the vehicle, and has a speed control actuator 41 and a steering control actuator 42 . Note that "running" refers to accelerated running/constant speed running/deceleration running of the vehicle.

The speed control actuator 41 controls driving torque or braking torque output to the driving wheels based on the speed control command value input from the vehicle-mounted control unit 3 . As the speed control actuator 41, for example, an engine is used for an engine vehicle, an engine and a motor/generator are used for a hybrid vehicle, and a motor/generator is used for an electric vehicle. Further, as an actuator for controlling only braking torque, for example, a hydraulic booster, an electric booster, a brake fluid pressure actuator, a brake motor actuator, or the like is used.

The steering control actuator 42 controls the steering angle of the steered wheels based on the steering control command value input from the in-vehicle control unit 3 . As the steering control actuator 42, a steering motor or the like provided in the steering force transmission system of the steering system is used.

The HMI module 5 is an interface for outputting and inputting information between the vehicle occupants (including the driver) and the onboard control unit 3 . The HMI module 5 includes, for example, a steering wheel, an accelerator, a brake, a display panel for displaying image information to the occupant, a speaker for audio output, operation buttons and a touch panel for the occupant to perform input operations, and the like.

[Control block configuration of automatic driving controller]
The automatic driving controller 31 includes a high-precision map data storage unit 311, a self-position estimation unit 312, a surrounding environment recognition unit 313, and a driving environment recognition unit 314, as shown in FIG. As hierarchical processing units for generating the target trajectory, a travel lane calculation unit 316, an operation determination unit 317, a travel area setting unit 318, and a target trajectory generation unit 319 are provided.

The high-precision map data storage unit 311 stores high-precision three-dimensional map data (hereinafter referred to as “HD map”) in which three-dimensional position information (longitude, latitude, height) of stationary objects existing outside the vehicle is set. It is an in-vehicle memory with Stationary objects include pedestrian crossings, stop lines, various signs, junctions, road markings, traffic lights, utility poles, buildings, signboards, center lines of roads and lanes, division lines, road shoulders, connections between roads, etc. elements are included.

Self-position estimation unit 312 estimates the current location (self-position) of the vehicle based on the input information. Here, sensor information from the in-vehicle sensor 1, HD map information from the high-precision map data storage unit 311, and the like are input to the self-position estimation unit 312. FIG. Then, the self-position estimation unit 312 estimates the self-position by, for example, matching the input sensor information and the HD map information. Self-position information is output from self-position estimation section 312 to driving environment recognition section 314 .

The surrounding environment recognition unit 313 recognizes the surrounding environment of the vehicle based on the input information and the dynamic surrounding environment information (local model) in which the ever-changing dynamic information of the surrounding environment of the vehicle is put into a database. Here, "dynamic information" means quasi-static data including, for example, traffic regulation information, road construction information, and wide-area weather information; static data, for example, dynamic data including surrounding vehicle information, pedestrian information, traffic light information, and the like. These dynamic information are hierarchized, and the update frequency of each data is different. The surrounding environment recognition unit 313 receives sensor information (environmental information around the vehicle) and the like from the vehicle-mounted sensor 1 . Using the dynamic surrounding environment information, the surrounding environment recognition unit 313 analyzes the input environmental information around the own vehicle and calculates surrounding environment recognition information. Surrounding environment recognition section 313 outputs surrounding environment recognition information to running environment recognition section 314 and running area setting section 318 .

The driving environment recognition unit 314 recognizes the driving environment of the own vehicle based on the input information and the dynamic driving environment information (world model) in which dynamic information of the driving environment of the own vehicle that changes every second is put into a database. Here, "dynamic driving environment information (world model)" refers to a dynamic driving environment obtained by expanding the environment recognition area more than "dynamic surrounding environment information (local model)" centering on the own position of the vehicle. information. Driving environment recognition unit 314 stores sensor information from in-vehicle sensor 1, guidance route information from navigation device 2, HD map information from high-precision map data storage unit 311, and self-position from self-position estimation unit 312. Information, surrounding environment recognition information from the surrounding environment recognition unit 313, and the like are input. Using the dynamic driving environment information, the driving environment recognition unit 314 calculates the driving environment recognition information on the HD map of a predetermined range based on the estimated current position of the own vehicle. Driving environment recognition section 314 outputs driving environment recognition information to action determining section 317 .

The driving lane calculation unit 316 calculates the driving lane (hereinafter referred to as "target lane") in which the vehicle should travel on the guidance route to the destination. Here, the guidance route information from the navigation device 2 and the HD map information from the high-definition map data storage unit 311 are input to the driving lane calculation unit 316 . Then, the driving lane calculation unit 316 calculates the direction of the destination determined from the route guidance information and the target lane from the HD map. The target lane information is output from the driving lane calculation unit 316 to the operation determination unit 317 in the next layer.

The motion determination unit 317 extracts events encountered by the own vehicle and determines the "motion of the own vehicle" in response to these events. Here, the "movement of the own vehicle" is the movement of the own vehicle necessary for traveling along the target lane, such as starting, stopping, accelerating, decelerating, turning right or left.

Driving environment recognition information from the driving environment recognition unit 314 , target lane information from the driving lane calculation unit 316 , and the like are input to the operation determination unit 317 . Then, the motion determination unit 317 checks the target lane and the driving environment around the vehicle, and determines an appropriate motion of the vehicle. Then, the vehicle motion determination information is output from the motion determination unit 317 to the travel area setting unit 318 in the next layer.

The travel area setting unit 318 sets a travelable area in which the vehicle can travel along the target lane. Here, the driving area setting unit 318 stores HD map information from the high-definition map data storage unit 311, surrounding environment recognition information from the surrounding environment recognition unit 313, vehicle operation determination information from the operation determination unit 317, and the like. is entered. Then, the travel area setting unit 318 compares the operation information of the own vehicle with the surrounding environment information of the own vehicle, and sets an area in which the own vehicle can travel. For example, when an object such as an obstacle exists around the vehicle, the travelable area is set so as to avoid contact with the object. The travelable area information is output from the travel area setting unit 318 to the target locus generation unit 319 in the next layer.

The target trajectory generator 319 generates a target trajectory within the set travelable area. Here, the target trajectory generation unit 319 receives travelable area information and the like from the travel area setting unit 318 . The target trajectory generation unit 319 generates a target trajectory by a geometrical method under the constraint condition that the vehicle travels within the drivable area from the current position of the vehicle to an arbitrarily set target position. . Note that the target trajectory generator 319 may generate the target trajectory using, for example, a composite clothoid curve. In addition, the target locus generator 319 may generate a target locus that allows driving that satisfies standards such as safety, legal compliance, and driving efficiency. Target trajectory information is output from the target trajectory generator 319 to the vehicle motion controller 32 .

Here, the target trajectory generator 319 may generate a target vehicle speed profile for the target trajectory. A target vehicle speed profile is a time-series target vehicle speed when traveling along a target locus. Thereby, the target vehicle speed profile can be generated in accordance with the curvature of the target locus. For example, in a scene with a large curvature, the target vehicle speed may be set low so as not to give the occupants a large vehicle behavior, and in a scene with a small curvature, the target vehicle speed profile may be set higher than in a scene with a large curvature. good. Alternatively, the target vehicle speed profile may be calculated first, and then the target trajectory may be generated in accordance with the target vehicle speed profile. For example, when the target vehicle speed is high, the trajectory may be generated with a small curvature, and conversely, when the target vehicle speed is low, the target trajectory may be generated with a large curvature. When the target vehicle speed profile is generated, the road surface μ value information may be used as a parameter for suppressing the change gradient (acceleration gradient, deceleration gradient) of the vehicle speed as the estimated friction coefficient of the road surface becomes lower.

[Control block configuration of vehicle motion controller]
As shown in FIG. 2, the vehicle motion controller 32 includes an input information arbitration unit 321, a reference model setting unit 322, a behavior control unit 323, a required drive torque calculation unit 324, a wheel load control unit 325, and a drive torque A selection unit 326 and a control output unit 327 are provided.

The input information arbitration unit 321 determines whether to calculate the control command value based on the input information from the automatic driving controller 31 or to calculate the control command value with the driver input from the HMI module 5 as the target, depending on the presence or absence of the driver input. mediate. Here, in the input information arbitration unit 321, when there is no driver input during selection of the automatic driving mode, the target vehicle speed and the target rudder set based on the information of the target vehicle speed profile and the target trajectory from the automatic driving controller 31 The corner information is output to the reference model setting unit 322 . On the other hand, when the driver input intervenes during automatic driving or when the manual driving mode is selected, information on the target vehicle speed and target steering angle set based on the driver input is output to the reference model setting unit 322.

The reference model setting unit 322 sets a reference model of vehicle motion that is represented by an arbitrarily settable motion equation and that occurs when the own vehicle is driven. In other words, information on the target vehicle speed and the target steering angle from the input information arbitration section 321 is input to the reference model setting section 322 . Then, the reference model setting unit 322 calculates the reference model value by substituting the input information into the equation of motion, which is the reference model. Here, the "reference model value" means, for example, a target yaw rate when using the yaw rate reference model, a target lateral acceleration when using the lateral acceleration reference model, and a target vehicle body when using the vehicle body slip angle reference model. Slip angle, etc. Information on the reference model values such as the target yaw rate is output from the reference model setting unit 322 to the behavior control unit 323 .

The behavior control unit 323 inputs the information of the reference model value from the reference model setting unit 322, converges the actual value of the own vehicle motion to the reference model value, and follows the vehicle behavior of the reference model. Calculate values. For example, if the reference model value is the target yaw rate, the deviation from the actual yaw rate occurring in the own vehicle is calculated, and the vehicle speed command value and the steering angle command value that reduce this deviation are calculated. At this time, the behavior control unit 323 performs calculation mainly by a feedback control system. From the behavior control section 323 , information on the vehicle speed command value is output to the required driving torque calculation section 324 , and information on the steering angle command value is output to the control output section 327 .

The required drive torque calculation unit 324 receives the vehicle speed command value from the behavior control unit 323 and calculates the required drive torque that achieves the vehicle speed command value. That is, when there is no driver input during selection of the automatic driving mode, the system required driving torque Trq(S) for achieving the vehicle speed command value based on the target vehicle speed profile and target trajectory information is calculated. When the driver input intervenes during automatic driving or when the manual driving mode is selected, the driver-requested driving torque Trq(D) that achieves the vehicle speed command value based on the driver input is calculated. Then, the required drive torque calculation section 324 outputs information on the system required drive torque Trq(S) or the driver required drive torque Trq(D) to the wheel load control section 325 and the drive torque selection section 326 .

The wheel load control section 325 is a control section having the same function as the wheel load control ECU 71 of the first embodiment. That is, the vehicle body slip angular velocity β' is calculated based on sensor input information from a wheel speed sensor, a yaw rate sensor, a lateral acceleration sensor, or the like. A torque correction amount Trq(add) is calculated by adding a positive or negative correction sign to the correction amount of the system required driving torque Trq(S) or the driver required driving torque Trq(D) according to the vehicle body slip angular velocity β'. Then, the corrected driving torque Trq(c) is calculated by adding the torque correction amount Trq(add) to the system required driving torque Trq(S) or the driver required driving torque Trq(D) acquired from the required driving torque calculation unit 324. do. Then, the wheel load control section 325 outputs information on the corrected drive torque Trq(c) to the drive torque selection section 326 .

The drive torque selector 326 is a controller having the same function as the drive torque selector 722 of the first embodiment. That is, the corrected driving torque Trq(c) from the wheel load control unit 325 and the system required driving torque Trq(S) or the driver required driving torque Trq(D) from the required driving torque calculating unit 324 are input. Then, when the wheel load control non-operation flag is input due to vehicle speed condition determination, the system required driving torque Trq(S) or the driver required driving torque Trq(D) is selected as the driving torque. On the other hand, when there is no input of the wheel load control non-operation flag due to vehicle speed condition determination, that is, when the vehicle speed V exceeds the second vehicle speed set value VThresh2, the corrected drive torque Trq(c) is used as the drive torque. select.

The drive torque selection unit 326 outputs the selected drive torque (system required drive torque Trq(S), driver required drive torque Trq(D), or correction drive torque Trq(c)) to the control output unit 327 .

When the steering angle command value is input from the behavior control section 323 , the control output section 327 outputs the steering angle command value to the steering control actuator 42 . Further, when the drive torque selected by the drive torque selector 326 is input, it outputs a drive control command for obtaining the selected drive torque to the speed control actuator 41 . For example, when the system required driving torque Trq(S) or the driver required driving torque Trq(D) is selected, the drive control command to obtain the system required driving torque Trq(S) or the driver required driving torque Trq(D) is speed controlled. Output to the actuator 41 .

However, when the corrected drive torque Trq(c) is selected by the drive torque selector 326, by outputting a wheel load control command for obtaining the corrected drive torque Trq(c) to the speed control actuator 41, Load control is performed.

Next, the wheel load control action will be described. In the second embodiment, the vehicle is an automatically driven vehicle A2 that automatically runs, and the required driving torque is the system required driving torque Trq(S ).

In other words, during autonomous driving, unlike during manual driving, the driver is not involved in the steering operation or accelerator operation. More sensitive than when running. Therefore, during automatic driving, higher vehicle behavior stability is required than during manual driving.

On the other hand, in a scene where the vehicle posture changes during automatic driving, wheel load control is performed by accelerating and decelerating so that the vehicle behavior stabilizes in a steady state more quickly. In particular, unintended swinging of the head of the driver or passenger on the exit side of the turn during automatic driving is suppressed. Therefore, in a scene where the vehicle travels on a curved road, turning characteristics due to stable vehicle behavior are realized for the driver and passengers, and comfortable automatic driving is achieved without giving discomfort to the driver and passengers. Since the other actions are the same as those of the first embodiment, description thereof will be omitted.

As described above, in the wheel load control method and the wheel load control device for the self-driving vehicle A2 of the second embodiment, in addition to the effects (1) to (8) and (10) of the first embodiment, the following effect.

(11) The vehicle is an automated driving vehicle A2 that runs automatically,
The required drive torque is the system required drive torque Trq(S) when automatically driving along the target trajectory generated by the automatic driving system (FIG. 10).
As a result, when the vehicle travels on a curved road, it is possible to achieve turning characteristics that result in stable vehicle behavior for the driver and passengers, and to achieve comfortable automatic driving that does not give the driver and passengers a sense of discomfort.

The wheel load control method and wheel load control device for a vehicle according to the present disclosure have been described above based on the first and second embodiments. However, the specific configuration is not limited to these examples, and design changes, additions, and the like are permitted as long as they do not depart from the gist of the invention according to each claim of the scope of claims.

In Embodiments 1 and 2, the correction sign of the torque correction amount Trq(add) is determined to be positive when the vehicle body slip angle β changes in the direction approaching zero, and the vehicle body slip angle β moves away from zero. An example is shown in which it is determined to be negative when it changes to . However, the correction sign of the torque correction amount may be determined to be positive only when the vehicle body slip angle changes toward zero. Alternatively, the correction sign of the torque correction amount may be determined to be negative only when the vehicle body slip angle changes away from zero.

Embodiment 1 shows an example in which the wheel load control method and the wheel load control device of the present disclosure are applied to the electric vehicle A1 that is manually operated by the driver. Embodiment 2 shows an example in which the wheel load control method and the wheel load control device of the present disclosure are applied to an automatically driven vehicle A2 in which vehicle motion is controlled based on speed and steering angle so as to travel along a target trajectory. . However, the wheel load control method and the wheel load control device of the present disclosure are not limited to manual driving vehicles and automatic driving vehicles, and are applicable to driving support vehicles equipped with an automatic braking function, a constant speed control function, a lane departure prevention function, etc. can also be applied. In short, the present invention can be applied to any vehicle capable of controlling the wheel loads of the front and rear wheels by accelerating or decelerating.

A1 Electric vehicle (manual driving vehicle)
63 motor (driving source for running)
7 wheel load control unit (controller)
71 wheel load control ECU
711 First vehicle speed condition determination unit 712 Vehicle slip angular velocity calculation unit (Vehicle slip angular velocity information acquisition unit)
713 Torque correction amount calculation unit 714 Second vehicle speed condition determination unit 715 Correction drive torque calculation unit 72 Drive motor ECU
721 driver required drive torque calculation unit (required drive torque calculation unit)
722 Drive torque selection unit 723 Control output unit A2 Autonomous vehicle 32 Vehicle motion controller (controller)
324 required drive torque calculation unit 325 wheel load control unit 326 drive torque selection unit 327 control output unit 41 speed control actuator

Claims (7)

A wheel load control method for a vehicle by a controller that corrects drive torque from a drive source for traveling based on predetermined information and performs wheel load control by acceleration/deceleration,
Acquiring information on the required driving torque according to the driver's request or system's request,
Acquiring information on a vehicle body slip angular velocity, which is the rate of change in the vehicle body slip angle formed by the vehicle body centerline and the vehicle traveling direction,
calculating a corrected drive torque obtained by correcting the required drive torque according to the vehicle body slip angular velocity;
outputting a wheel load control command for obtaining the corrected drive torque to the drive source for traveling;
A torque correction amount is calculated by adding a positive or negative correction sign to the correction amount of the required drive torque according to the vehicle body slip angular velocity, and the corrected drive torque is calculated by adding the torque correction amount to the required drive torque. ,
When the vehicle body slip angle changes away from zero, the correction sign determines that the sign of the torque correction amount is negative, and corrects the required driving torque to the deceleration side,
When the vehicle body slip angle changes in a direction approaching zero, the correction sign determines that the sign of the torque correction amount is positive, and corrects the required drive torque to the acceleration side. Load control method. In the vehicle wheel load control method according to claim 1 ,
A vehicle wheel load control method, wherein the torque correction amount of the required driving torque is calculated by a value proportional to the magnitude of the absolute value of the vehicle body slip angular velocity. In the vehicle wheel load control method according to claim 2 ,
setting a front/rear G limit value that suppresses the front/rear G generated by the correction of the required drive torque to a level that is not perceived by vehicle occupants;
A wheel load control method for a vehicle, wherein the torque correction amount of the required drive torque is set to a value limited by the upper limit correction amount when the torque correction amount exceeds the upper limit correction amount for the longitudinal G limit value. In the vehicle wheel load control method according to any one of claims 1 to 3 ,
When acquiring the information of the vehicle body slip angular velocity by estimation calculation, the vehicle body speed condition is that the vehicle body speed exceeds a first vehicle body speed set value,
When wheel load control for adding the torque correction amount to the required drive torque is started, the vehicle speed condition is that the vehicle speed exceeds a second vehicle speed set value higher than the first vehicle speed set value. A vehicle wheel load control method characterized by: In the vehicle wheel load control method according to any one of claims 1 to 4 ,
The vehicle is a manually operated vehicle that is operated by a driver,
A vehicle wheel load control method, wherein the required drive torque is a driver-requested drive torque corresponding to an amount of accelerator operation by the driver and a vehicle speed. In the vehicle wheel load control method according to any one of claims 1 to 4 ,
The vehicle is an automated driving vehicle that runs automatically,
A wheel load control method for a vehicle, wherein the required driving torque is a system required driving torque when automatically driving along a target trajectory generated by an automatic driving system. A wheel load control device for a vehicle comprising a controller that corrects drive torque from a drive source for traveling based on predetermined information and performs wheel load control by acceleration and deceleration,
The controller is
a required drive torque acquisition unit that acquires information on a required drive torque according to a driver request or a system request;
a vehicle body slip angular velocity information acquisition unit that acquires information on a vehicle body slip angular velocity, which is the rate of change in the vehicle body slip angle formed by the vehicle body centerline and the vehicle traveling direction;
a corrected drive torque calculation unit that calculates a corrected drive torque obtained by correcting the required drive torque according to the vehicle body slip angular velocity;
a control output unit that outputs a wheel load control command for obtaining the corrected drive torque to the drive source for traveling;
has
The corrected drive torque calculation unit calculates a torque correction amount by adding a positive or negative correction sign to the correction amount of the required drive torque according to the vehicle body slip angular velocity, and adds the torque correction amount to the required drive torque. to calculate the corrected driving torque,
When the vehicle body slip angle changes in a direction away from zero, the correction sign determines that the sign of the torque correction amount is negative and corrects the required driving torque to the deceleration side,
When the vehicle body slip angle changes in a direction approaching zero, the correction sign determines that the sign of the torque correction amount is positive, and corrects the required drive torque to the acceleration side. Load controller.

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