JP2023021494A - Vehicle control device, vehicle control method and vehicle control system - Google Patents

Abstract

To provide a vehicle control device, a vehicle control method and a vehicle control system which can enhance smoothness when a vehicle stops in vehicle control which generates a driving force in a direction opposed to a target brake force when the vehicle stops.SOLUTION: A vehicle control device 17 corrects a control command to be output for generating anti-jerk control torque by a rear motor 7 by use of a friction coefficient modification gain according to a temperature of brake pads of friction brakes 3 in a state where a friction brake force is being generated when decelerating a vehicle according to target brake torque.SELECTED DRAWING: Figure 1

Description

The present invention relates to a vehicle control device, a vehicle control method, and a vehicle control system.

Patent Document 1 discloses means for determining a control amount of a friction braking device based on a target friction braking amount calculated from a required braking force and a regenerative execution amount, and a control amount absorbed by the friction braking from the start of the operation of the friction braking. and means for correcting the control amount of the friction braking device so that the target friction braking amount and the actual friction braking amount match based on the braking energy.

JP-A-2008-120220

However, in Patent Document 1, since the correction coefficient is determined by referring to a preset map of correction coefficients for changes in pad temperature, there is a risk that the correction coefficient cannot be obtained with high accuracy when the situation changes.
By the way, as one vehicle control, it is conceivable to generate a driving force in the direction opposite to the target braking force when the vehicle stops to make the stopping smoother. If the target braking force cannot be obtained, the difference between the target braking force and the actual braking force becomes large, and there is a risk that the vehicle will not stop smoothly.
One object of the present invention is to provide a vehicle control apparatus, a vehicle control method, and a vehicle control that can improve smoothness when a vehicle stops in vehicle control for generating a driving force in a direction opposite to a target braking force when the vehicle stops. It is to provide a system.

A vehicle control method according to an embodiment of the present invention acquires a physical quantity related to a target braking force required to decelerate a vehicle, and generates friction braking force when decelerating the vehicle based on the physical quantity related to the target braking force. In this state, the control command output for generating the driving force by the driving device is corrected due to the physical quantity related to the temperature of the friction braking device.

Therefore, according to the present invention, the smoothness of the vehicle when it stops can be improved.

1 is a configuration diagram of an electric vehicle control system according to Embodiment 1. FIG. 2 is a control block diagram of a vehicle control device 17 for implementing anti-jerk control; FIG. 3 is a control block diagram of a target braking torque corrector 31. FIG. FIG. 4 is a temperature-friction coefficient characteristic diagram of a brake pad; 4 is a time chart showing the operation of anti-jerk control when the target braking force is smaller than the actual braking force; 4 is a time chart showing the operation of anti-jerk control when the target braking force is greater than the actual braking force; 3 is a control block diagram of a correction gain calculator 34 based on temperature. FIG. 3 is a control block diagram of a friction coefficient correction gain calculator 35. FIG. 4 is a time chart showing the operation of anti-jerk control;

[Embodiment 1]
FIG. 1 is a configuration diagram of an electric vehicle control system according to a first embodiment.
The electric vehicle 1 has front wheels 2FL, 2FR, rear wheels 2RL, 2RR, and friction brakes (friction braking devices) 3FL, 3FR, 3RL, 3RR (hereinafter referred to as the Friction brakes are also collectively referred to as friction brakes 3).
The electric vehicle 1 has a rear motor (driving device) 7 that outputs torque to rear wheels 2RL and 2RR. The rear wheels 2RL and 2RR are collectively referred to as drive wheels 2 as well. Power transmission between the rear motor 7 and the rear wheels 2RL, 2RR is performed via a reduction gear 8, a differential 10 and rear axles 6RL, 6RR.

Each wheel 2FL, 2FR, 2RL, 2RR has a wheel speed sensor 11FR, 11FL, 11RL, 11RR for detecting wheel speed. The rear motor 7 has a rear wheel resolver 13 that detects the number of revolutions of the motor. In addition, the electric vehicle 1 has a G sensor 5 that detects longitudinal acceleration of the vehicle.
The friction brake 3 presses a brake pad against a brake rotor that rotates integrally with each wheel in the direction of the rotation axis of each wheel to generate braking force by frictional force. The friction brake 3 of the first embodiment will be described as having a configuration in which the brake pad is pressed by a wheel cylinder operated by brake fluid pressure. Not limited.

Electric vehicle 1 has a low voltage battery 14 and a high voltage battery 15 . Low-voltage battery 14 is, for example, a lead-acid battery. High-voltage battery 15 is, for example, a lithium-ion battery or a nickel-metal hydride battery. The high voltage battery 15 is charged with electric power boosted by the DC-DC converter 16 .
The electric vehicle 1 has a vehicle control device (control section) 17 , a brake control device 18 , a rear motor control device 20 and a battery control device 19 . Each controller 17 , 18 , 20 shares information with each other via CAN bus 21 .

The vehicle control device 17 acquires information from various sensors such as a rear wheel resolver 13, an accelerator pedal sensor 22 that detects the amount of accelerator operation, a brake sensor 23 that detects the amount of brake operation, and a gear position sensor 24, and integrates the vehicle. control. The vehicle control device 17 outputs a driver-requested torque to be output by the rear motor 7 according to the requested distributed torque, with respect to the requested torque according to the driver's accelerator operation, brake operation, or the like.
The brake control device 18 acquires information from various sensors such as the brake sensor 23, sets a target braking torque that is a torque conversion value of the target braking force of the vehicle, and determines the brake fluid required for each wheel according to the target braking torque. A pressure is generated and output to the friction brake 3 through the hydraulic pipe 18a.

Battery control device 19 monitors the charge/discharge state of high-voltage battery 15 and the single cells that make up high-voltage battery 15 . The battery control device 19 calculates a battery request torque limit value based on the charge/discharge state of the high voltage battery 15 and the like. The battery request torque limit value is the maximum torque allowed in the rear motor 7 . For example, when the charge amount of the high-voltage battery 15 is low, the battery request torque limit value is set to a smaller value than usual.
The rear motor control device 20 controls electric power supplied to the rear motor 7 based on the rear required torque.

In the electric vehicle 1 of Embodiment 1, anti-jerk control is performed in which driving torque equivalent to the actual braking torque is output from the rear motor 7 when the vehicle is stopped, with the aim of suppressing unpleasant vehicle shaking and reducing passenger fatigue when the vehicle is stopped. to implement. As a result, the longitudinal jerk (jerk) that occurs when the vehicle is stopped with a certain amount of brake operation can be reduced by about 68% compared to the case without anti-jerk control. In other words, smooth stopping can be realized without skillful brake operation. In the anti-jerk control, under the assumption that the target braking torque and the actual braking torque are approximately the same, the rear motor 7 outputs an anti-jerk control torque corresponding to the target braking torque.

FIG. 2 is a control block diagram of the vehicle control device 17 for implementing anti-jerk control.
A target braking torque correction unit 31 receives a target braking torque and a friction coefficient correction gain, which will be described later, and outputs an estimated actual braking torque. FIG. 3 is a control block diagram of the target braking torque corrector 31. As shown in FIG. The target braking torque correction unit 31 calculates an estimated actual braking torque by multiplying the target braking torque by a value obtained by multiplying the set nominal friction coefficient value (reference friction coefficient) by the friction coefficient correction gain. The nominal friction coefficient value is a value set at the start of running, and once set, is not changed during running. The nominal friction coefficient value is set by referring to a map obtained in advance from the temperature-friction coefficient characteristics of the brake pad as shown in FIG. The temperature may be the outside air temperature at the start of running, or a predetermined temperature (for example, 20° C.).
The vibration suppression control unit 32 inputs the estimated actual braking torque, the G sensor value and the vehicle speed, and outputs the anti-jerk control torque and the slope estimation result (slope estimated value, slope resistance estimated value). The G sensor value is the output value of the G sensor 5. The vehicle speed can be calculated from the output values of the wheel speed sensor 11 and the rear wheel resolver 13 .

The vibration suppression control unit 32 calculates a slope resistance estimated value, which is the resistance acting on the vehicle due to the road slope, from the vehicle speed and the G sensor value. Specifically, an estimated gradient value is obtained from the deviation between the estimated acceleration calculated from the vehicle speed and the G sensor value (actual acceleration), and the estimated gradient resistance value is calculated from the estimated gradient value. This is to avoid an excessive decrease in vehicle deceleration when the anti-jerk control torque is added due to the slope of the downward slope.
The vibration suppression control unit 32 subtracts the torque corresponding to the gradient resistance from the estimated actual braking torque to calculate an anti-jerk control torque capable of suppressing vibration in the pitching direction. The reason why the torque corresponding to the slope resistance is reduced is to avoid applying the anti-jerk control torque that generates a driving force exceeding the braking force.

A correction gain calculation unit 33 based on vehicle behavior when the vehicle is stopped receives the gradient estimation result, target braking torque, G sensor value, vehicle speed, and brake operation amount, and outputs a correction gain based on the vehicle behavior. When the pad temperature characteristics (temperature-friction coefficient characteristics) change due to deterioration of the brake pads over time, etc., the temperature-based correction gain calculator 34, which will be described later, corrects the change in the friction coefficient due to the pad temperature change to the target braking torque. However, a deviation occurs between the anti-jerk control torque based on the target braking torque and the actual braking torque. As shown in FIG. 5, when the target braking torque is smaller than the actual braking torque, the anti-jerk control torque is insufficient with respect to the actual braking torque, resulting in a strong shock upon stopping. In FIG. 5, the maximum value (peak value) of jerk occurring at the time of stopping is called maximum jerk. On the other hand, as shown in FIG. 6, when the target braking torque is larger than the actual braking torque, the anti-jerk control torque is excessive with respect to the actual braking torque, resulting in a long braking distance. In FIG. 6, the maximum amplitude of acceleration occurring at the time of stopping is called the acceleration fluctuation range. Therefore, in the first embodiment, based on the vehicle behavior (jerk, acceleration) that occurs when the vehicle is stopped, the percentage error in the target braking torque with respect to the actual braking torque is learned, and the error is canceled the next time the vehicle is stopped. Therefore, a gain for correcting the target braking torque (correction gain based on vehicle behavior) is calculated.

For example, when the maximum jerk is equal to or greater than the maximum jerk threshold just before stopping when the vehicle speed is equal to or lower than a specified speed, the correction gain based on the vehicle behavior is set to a positive sign, and the larger the maximum jerk, the larger the correction gain. Thereby, the shortage of the anti-jerk control torque with respect to the actual braking torque can be suppressed. In addition, when the maximum jerk generated is less than the maximum jerk threshold value and the acceleration fluctuation width is equal to or greater than the acceleration fluctuation width threshold value just before stopping when the vehicle speed is equal to or lower than the specified speed, the correction gain based on the vehicle behavior is applied. With a negative sign, the larger the acceleration fluctuation range, the smaller the correction gain (the larger the absolute value). As a result, excess anti-jerk control torque relative to actual braking torque can be suppressed. The maximum jerk threshold is obtained by comparing a value obtained by adding the torque conversion value of the estimated slope resistance value to the target braking torque and the specified braking torque. is less than the latter, the maximum jerk threshold may be set to the second threshold X2 (|X1|>|X2|).

A temperature-based correction gain calculator 34 inputs a target braking torque, a vehicle behavior-based correction gain, a wheel angular velocity (output value of the wheel speed sensor 11), an outside air temperature, and a cooling water temperature, and outputs a temperature-based correction gain. . When the friction coefficient of the pad changes due to temperature changes, the anti-jerk control torque based on the target braking torque deviates from the actual braking torque. Therefore, the pad temperature and pad friction coefficient are estimated, and a gain (correction gain based on temperature) for correcting the target braking torque is calculated in order to cancel the error of the estimated pad friction coefficient with respect to the nominal friction coefficient value.

FIG. 7 is a control block diagram of the correction gain calculator 34 based on temperature. Pad temperature estimation and friction coefficient estimation unit 341 estimates the pad temperature from the correction gain based on the target braking torque, wheel angular velocity, outside air temperature, cooling water temperature, and vehicle behavior, and from the estimated pad temperature, the brake pad shown in FIG. Calculate the estimated pad friction coefficient with reference to the temperature-friction coefficient characteristic diagram. The pad temperature T1 is calculated using the following formula (1), and is calculated using the formula (2) at the start of running.

T1(t)＝T1(t－1)－{(T1(t－1)－T2(t))×K(t)＋α×Tb(t)×ω(t)}/(C×m) … (1)
T1(0) = T2(0) …(2)
where, T2 is the outside air temperature, K(t) is the correction coefficient for natural convection, forced convection, etc. (calculated from the defined map), α is the braking heat rate that flows into the brake pads, Tb(t) is the actual braking torque, ω(t) is the wheel angular velocity, C is the specific heat of the brake pad, and m is the mass of the brake pad. The actual braking torque Tb(t) is calculated by multiplying the target braking torque by the pad friction coefficient μ(t). The pad friction coefficient μ(t) is calculated using the following formula (3).
μ(t)=nominal friction coefficient×correction gain based on temperature×(1+correction gain based on vehicle behavior) (3)

The temperature-based correction gain calculator 342 outputs a value obtained by dividing the estimated pad friction coefficient by the nominal friction coefficient value (estimated pad friction coefficient/nominal friction coefficient value) as a temperature-based correction gain.
A friction coefficient correction gain calculator 35 inputs a correction gain based on vehicle behavior and a correction gain based on temperature, and outputs a friction coefficient correction gain. FIG. 8 is a control block diagram of the friction coefficient correction gain calculator 35. As shown in FIG. A value obtained by multiplying 1 by a correction gain based on vehicle behavior (1 + correction gain based on vehicle behavior) and a correction gain based on temperature {(1 + correction gain based on vehicle behavior) x correction gain based on temperature } is output as the friction coefficient correction gain.

Next, the effect of Embodiment 1 is demonstrated.
FIG. 9 is a time chart showing the operation of anti-jerk control.
In section 1, whether or not there is a difference between the nominal friction coefficient value and the actual friction coefficient at the start of running is estimated based on the outside air temperature, and the correction gain based on the temperature is corrected. Furthermore, by changing the temperature-based correction gain in accordance with the change in pad temperature during deceleration, it is intended that the temperature change will be effective from the start of running. However, in FIG. 9, the current brake pad temperature-friction coefficient characteristics are different from the originally acquired characteristics, so correction based on temperature alone cannot be used, and the actual braking torque is excessive relative to the target braking torque. As a result, a large jerk occurs just before the stop.

In interval 2, the gain based on temperature is corrected in the same way as in interval 1. Furthermore, when the vehicle stops in section 1, the maximum jerk exceeds the maximum jerk threshold, and the correction gain calculation unit 33 based on the vehicle behavior at the time of stop detects that the vehicle has not been satisfactorily stopped. based correction gains are updated. By correcting the target braking torque with the friction coefficient correction gain obtained from these two gains, the anti-jerk control torque equivalent to the actual braking torque is calculated. When the anti-jerk control torque equivalent to the actual braking torque cannot be calculated only with the correction gain based on the temperature, as in section 1, it is assumed that the temperature-friction coefficient characteristics of the brake pad have changed due to aged deterioration or the like. Therefore, by correcting the friction coefficient correction gain with a correction gain based on vehicle behavior, it is possible to respond to changes in the temperature-friction coefficient characteristics of the brake pads, and achieve anti-jerk control torque equivalent to the actual braking torque.

Section 3 is a scene in which the brakes were not used for a long time after stopping in section 2, and the pad temperature dropped to the temperature equivalent to the outside temperature at the start of driving. In interval 3, the pad temperature is lower than in interval 2, but the temperature-based correction gain calculator 34 updates the estimated pad temperature over time, and based on the estimated temperature at that time, the brake pad temperature is reduced. A temperature-based correction gain that is considered more appropriate from the temperature-friction coefficient characteristics is set. Furthermore, in section 2, the correction gain calculation unit 33 is set based on the vehicle behavior when the vehicle is stopped for changes in the temperature-friction coefficient characteristics due to aging of the brake pads, so an anti-jerk control torque equivalent to the actual braking torque is realized. can.

As described above, the vehicle control device 17 of the first embodiment decelerates the vehicle in accordance with the target braking torque, and the anti-jerk control torque, which is the driving force of the rear motor 7, is generated while the friction braking force is being generated. A control command (target braking torque) output for generating is corrected by a friction coefficient correction gain according to the temperature of the brake pad of the friction brake 3. As a result, even if the friction coefficient of the brake pads changes due to changes in the pad temperature during deceleration, anti-jerk control torque equivalent to the actual braking torque can be achieved, improving smoothness when the vehicle stops. .

When the vehicle is decelerated according to the target braking torque, the vehicle control device 17 obtains the acceleration and jerk of the vehicle, and from the obtained acceleration and jerk, determines by what percentage the target braking torque has an error with respect to the actual braking torque. is learned, and when the vehicle is stopped next time, a correction gain based on the vehicle behavior for canceling the error is obtained, and the friction coefficient correction gain is corrected. As a result, even if the temperature-friction coefficient characteristics change due to deterioration over time of the brake pads, etc., the anti-jerk control torque equivalent to the actual braking torque can be achieved, so the smoothness of the vehicle when it stops can be improved.

The vehicle control device 17 performs correction based on the outside air temperature T2, the wheel angular velocity ω, the mass m of the brake pad, the specific heat C of the brake pad, the target braking torque, the nominal friction coefficient, and the temperature-friction coefficient characteristics of the brake pad stored in advance. A gain is obtained, and the larger the temperature-based correction gain, the larger the friction coefficient correction gain. As a result, the deviation of the pad friction coefficient from the nominal friction coefficient can be calculated without actually measuring the temperature of the brake pad. By correcting the target braking torque with a friction coefficient correction gain proportional to the amount of deviation, an anti-jerk control torque equivalent to the actual braking torque can be achieved.

[Other embodiments]
Although the embodiment for carrying out the present invention has been described above, the specific configuration of the present invention is not limited to the configuration of the embodiment, and design changes, etc. within the scope of the invention may be made. is also included in the present invention.
For example, in the present embodiment, the present invention is applied to a rear-wheel drive electric vehicle, but may be applied to a front-wheel drive electric vehicle or a four-wheel drive electric vehicle. Further, the vehicle is not limited to an electric vehicle, and may be a vehicle equipped with an internal combustion engine, or a hybrid vehicle that can run using both an engine and a motor.
The target braking force includes automatic braking and the like in addition to the braking operation by the driver.

1 electric vehicle, 3 friction brake (friction braking device), 7 rear motor (driving device), 17 vehicle control device (control section)

Claims (6)

A vehicle comprising a control section that is provided in the vehicle having a friction braking device that generates a friction braking force on the vehicle and a drive device that generates a driving force on the vehicle, and which outputs a result of calculation based on input information. a controller,
The control unit
obtaining a physical quantity related to the speed of the vehicle;
Acquiring a physical quantity related to a target braking force required to decelerate the vehicle;
When decelerating the vehicle based on the physical quantity related to the target braking force, the friction braking device outputs a control command to generate a driving force by the driving device while the friction braking force is being generated. corrected due to physical quantities related to the temperature of
Vehicle controller. The vehicle control device according to claim 1,
The control unit
obtaining a physical quantity related to the behavior of the vehicle when decelerating the vehicle based on the physical quantity related to the target braking force;
correcting the control command due to a physical quantity related to the behavior of the vehicle;
Vehicle controller. The vehicle control device according to claim 1,
The temperature of the friction braking device is the temperature of the brake pad,
The control unit
The brake pad obtained based on a pre-obtained reference coefficient of friction of the brake pad, a physical quantity related to the target braking force, a specific heat of the brake pad, a mass of the brake pad, a wheel angular velocity of the vehicle, and an outside air temperature. Determine the correction gain based on the estimated friction coefficient of and
correcting the control command based on the magnitude of the correction gain;
Vehicle controller. The vehicle control device according to claim 3,
The control unit
obtaining a physical quantity related to the behavior of the vehicle when decelerating the vehicle based on the physical quantity related to the target braking force;
calculating the correction gain by adding a physical quantity related to the behavior of the vehicle;
correcting the control command based on the magnitude of the correction gain;
Vehicle controller. A vehicle control method that includes a friction braking device that generates a friction braking force on a vehicle and a drive device that generates a driving force on the vehicle, and is executed by a control unit mounted on the vehicle,
obtaining a physical quantity related to the speed of the vehicle;
Acquiring a physical quantity related to a target braking force required to decelerate the vehicle;
When decelerating the vehicle based on the physical quantity related to the target braking force, the friction braking device outputs a control command to generate a driving force by the driving device while the friction braking force is being generated. corrected due to physical quantities related to the temperature of
Vehicle control method. a friction braking device that generates a friction braking force on the vehicle;
a driving device that generates a driving force for the vehicle;
A control device that outputs a result calculated based on input information,
obtaining a physical quantity related to the speed of the vehicle;
Acquiring a physical quantity related to a target braking force required to decelerate the vehicle;
When decelerating the vehicle based on the physical quantity related to the target braking force, the friction braking device outputs a control command to generate a driving force by the driving device while the friction braking force is being generated. corrected due to physical quantities related to the temperature of
the control device;
vehicle control system.

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