JP2021027634A - Control device for vehicle - Google Patents

Abstract

To provide a control device for a vehicle capable of suppressing hunting in slip control of a wheel and stabilizing behavior of the vehicle.SOLUTION: In a control device for a vehicle having at least a motor as a driving force source, a rotational frequency of the motor is controlled so as to attain a predetermined target slip ratio when a driving wheel is slipped, the target slip ratio is lowered when a determination that actual rotational frequency of the motor is in the hunting state exceeding a preset prescribed range relative to the rotational frequency of the motor on the basis of the target slip ratio is made, target rotational frequency of the motor is calculated on the basis of the lowered target slip ratio, and the actual rotational frequency is controlled to the target rotational frequency (Steps S4-7).SELECTED DRAWING: Figure 3

Description

The present invention relates to a device for controlling a vehicle having at least a motor as a driving force source, and particularly to a control device when a wheel (driving wheel) slips.

Conventionally, traction control is known as a control for suppressing wheel slip. For example, the control device described in Patent Document 1 grips a drive wheel by torque-down control of a motor when slip of the drive wheel is detected. Is configured to recover. Specifically, it is configured to calculate the first torque down amount for protecting circuit parts and mechanical parts such as gears, and the second torque down amount for stabilizing the behavior of the vehicle. The larger torque-down amount of the first torque-down amount and the second torque-down amount is selected as the target torque-down amount.

Further, Patent Document 2 describes an invention relating to a traveling control device for a hybrid vehicle including an engine and a motor as a driving force source. The travel control device described in Patent Document 2 is configured to perform torque down control for reducing engine torque and motor torque when the wheels slip. In addition, in consideration of the responsiveness of the output of the engine and the motor during the torque down control, the control that feeds back the driving force to the wheels by the motor (first slip suppression control) and the driving force to the wheels by the engine are fed back. Of the controls (second slip suppression control), the feedback gain in the first slip suppression control is configured to be large. As a result, torque down control (that is, slip suppression) can be performed with good responsiveness.

Japanese Unexamined Patent Publication No. 2006-115644 Japanese Unexamined Patent Publication No. 2001-263148

According to the control device of Patent Document 1 described above, the larger torque-down amount of the first torque-down amount and the second torque-down amount is selected as the target torque-down amount. It is said that it is possible to achieve both protection and stability (stability of vehicle behavior). However, in the case of a low μ road, especially on a road surface with extremely low μ such as a snow-covered road surface of fresh snow or an ice floe, the control device described in Patent Document 1 keeps the slip ratio constant or converges to a target value. May not be possible. If μ is extremely low, there is a risk of overshooting from the slip target value and hunting (deviation beyond a predetermined range) due to a slight control error or deviation. Further, in Patent Document 2, a similar problem occurs, and when an overshoot occurs from the slip target value, the above feedback control may diverge, resulting in a slip state, and eventually the behavior of the vehicle becomes unstable. There is a risk of becoming.

The present invention has been conceived by paying attention to the above technical problems, and provides a vehicle control device capable of suppressing hunting in wheel slip control and stabilizing the behavior of the vehicle. Is the purpose.

In order to achieve the above object, the present invention is configured to include at least a motor as a driving force source and reduce the torque of the motor to grip the slipped drive wheel when the drive wheel slips. The vehicle control device includes a controller for controlling the vehicle, and the controller controls the rotation speed of the motor so as to obtain a predetermined target slip ratio when the drive wheels slip, and the motor When it is determined whether or not the actual rotation speed of the motor is hunting beyond a predetermined range determined in advance with respect to the rotation speed of the motor based on the target slip ratio, and it is determined that the hunting has occurred. In addition, the target slip ratio is lowered, the target rotation speed of the motor is calculated based on the lowered target slip ratio, and the actual rotation speed of the motor is controlled to the target rotation speed. It is characterized by being present.

According to the present invention, when the actual rotation speed of the motor is hunting with respect to the target rotation speed based on the predetermined target slip ratio (that is, when it deviates beyond a predetermined range), it is determined in advance. It is configured to reduce the target slip ratio and correct the target slip ratio. Specifically, when it is determined that hunting has occurred, the target rotation speed of the motor is calculated based on the reduced target slip ratio, and the actual rotation speed of the motor is set to that target rotation speed. Is configured to control. That is, it is configured to reduce the slip ratio and control the motor after grasping that the rotation speed of the motor has hunted. Therefore, for example, it is possible to prevent or suppress the hunting that has occurred as in Patent Document 1 and Patent Document 2 described above, or the divergence of feedback control. That is, hunting can be reliably suppressed, and as a result, the slipped drive wheel can be gripped. Further, by suppressing the occurrence of the hunting in this way, the behavior of the vehicle can be stabilized.

It is a schematic diagram which shows the drive system in the vehicle which can be the object of this invention. It is a block diagram for explaining the traction control control of a motor, (a) is a block diagram for explaining the control in a normal time, and (b) explains the control in embodiment of this invention. It is a block diagram for. It is a flowchart for demonstrating an example of control in Embodiment of this invention. It is a figure for demonstrating the control which reduces a target slip ratio. It is a flowchart for demonstrating the subroutine of the control example of FIG. It is a figure for demonstrating the time chart when the control example of FIG. 3 is carried out.

An embodiment of the present invention will be described with reference to the drawings. It should be noted that the embodiments shown below are merely examples of cases where the present invention is embodied, and do not limit the present invention.

Vehicles that can be targeted by the present invention include at least driving motors such as hybrid vehicles that use an engine and a motor as driving power sources, electric vehicles that use only motors as driving power sources, and fuel cell vehicles (hereinafter, simply). It is a vehicle equipped with a motor). As an example thereof, FIG. 1 schematically shows a hybrid vehicle (hereinafter, simply referred to as a vehicle) Ve equipped with an engine 1 and two motors (MG1 and MG2). The engine 1 and the first motor (MG1) 2 are connected to the power split mechanism 4. The power split mechanism 4 is configured by a single pinion type planetary gear mechanism as an example, and the first motor 2 is connected to the sun gear 5 and the engine 1 is connected to the carrier 6. The ring gear 7 is an output element, and the output gear 8 is provided on the outer circumference of the ring gear 7. On the other hand, a counter shaft 9 is provided in parallel with the power split mechanism 4, and a driven gear 10 that meshes with the output gear 8 is attached to the counter shaft 9.

Further, a drive gear 11 is attached to the counter shaft 9, and the drive gear 11 meshes with the ring gear 13 in the differential gear 12. Further, the drive gear 14 attached to the output shaft of the second motor (MG2) 3 meshes with the driven gear 10. Therefore, it is configured to add the torque of the second motor 3 to the torque output from the power split mechanism 4. Then, the torque is transmitted from the differential gear 12 to the left and right drive wheels 15 to travel. The power split mechanism 4, the gears 8, 10, 11 and the counter shaft 9 and the differential gear 12 constitute the power transmission system according to the embodiment of the present invention.

Each of the motors 2 and 3 is, for example, a permanent magnet type synchronous motor, which is a so-called motor generator having a function of functioning as a motor to output torque and forcibly rotating to generate power, and is a power storage device. It is also electrically connected to the power supply unit 16 including the inverter and the like. At the time of braking, the vehicle Ve converts the kinetic energy of the vehicle Ve into electrical energy by operating the motors 2 and 3 as a generator, and recovers the converted energy in the power storage device.

An electronic control device (ECU) 17 for controlling the output of each of the motors 2 and 3 and the start / stop and output of the engine 1 is provided. The ECU 17 corresponds to the "controller" in the embodiment of the present invention, is configured mainly by a microcomputer, performs calculations using input data, data stored in advance, and a program, and the calculation result thereof. Is configured to be output as a control command signal. The input data includes, for example, vehicle speed, accelerator opening which is a drive request amount, wheel speed of each wheel, charge amount (SOC) of a power storage device, engine rotation speed, engine torque, rotation speed of each motor 2 and 3. The torque, the braking force required for braking, the amount of depression of the brake pedal, and the like, and the data stored in advance are maps and the like in which each driving mode such as EV driving mode and HV driving mode is determined. Then, the ECU 17 outputs, as control command signals, a command signal for starting and stopping the engine 1, a torque command signal for each of the motors 2 and 3, a torque command signal for the engine 1, and the like. Although the example of FIG. 1 shows an example in which one ECU is provided, a plurality of ECUs may be provided for each device to be controlled or for each control content, for example.

The vehicle Ve configured in this way controls the output torques of the engine 1 and the motors 2 and 3 in order to stabilize the behavior of the vehicle Ve when the drive wheels 15 slip, as is conventionally known. Alternatively, traction control (TRC control) is performed to prevent the wheels from slipping by controlling the brake hydraulic pressure, or antilock braking (ABS control) is performed to prevent the wheels from locking. For example, the motor traction control for controlling the motor torque is normally or generally executed as shown in the block diagram of FIG. 2A. In the example shown here, the vehicle body speed detection unit B1 and the target slip rate detection unit B2 It is composed of a target motor rotation speed calculation unit B3, a motor rotation speed FB control unit B4, and a motor rotation speed detection unit B5.

First, the vehicle body speed obtained from the wheel speed sensor is detected by the vehicle body speed detection unit B1. Further, the target slip rate calculation unit B2 calculates the target slip rate. The target slip ratio is a predetermined slip ratio capable of outputting the maximum driving force, and is appropriately set according to the characteristics of various vehicles and wheels. Then, the target motor rotation speed is calculated by the target motor rotation calculation unit B3 based on the vehicle body speed detected by the vehicle body speed detection unit B1 and the target slip rate calculated by the target slip rate calculation unit B2. Further, the motor torque is feedback-controlled by the FB control unit B4 so as to reach the target motor rotation speed, and is output to the second motor 3 which is a traveling motor. If the actual motor rotation speed is detected by the motor rotation speed detection unit B5 and the detected rotation speed deviates from the target rotation speed, the motor rotation speed is again performed by the FB control unit B4. Control the number.

On the other hand, when the traction control shown in FIG. 2A is executed on a low μ road having an extremely small μ such as an ice plate, the above feedback control diverges or the motor is caused by a slight control deviation or error. The number of revolutions hunts against the target number of revolutions, and the target slip ratio cannot be controlled, and the slip ratio may increase. Therefore, in the embodiment of the present invention, when the motor rotation speed is hunted by feedback control, the target slip ratio is corrected. In addition, the above-mentioned hunting means that a variation occurs with respect to a target value, and the variation exceeds a predetermined threshold value, deviates from an acceptable range, or repeatedly straddles the threshold value or range. Means.

FIG. 2B is a block diagram for explaining traction control of the motor including control for correcting the target slip ratio. Although the basic configuration is the same as the control of FIG. 2A described above, in the embodiment of the present invention, whether or not the motor rotation speed FB control unit B40 is hunting with respect to the motor target rotation speed. Includes a judgment function. Further, the target slip rate calculation unit B20 includes a correction function for reducing the target slip rate when it is determined that the actual motor rotation speed is hunting based on the hunting determination. That is, when it is determined that the motor rotation speed is hunting with respect to the target rotation speed, the target slip ratio is reduced, in other words, the target slip ratio is corrected on the grip side.

The control of FIG. 2B will be described in more detail with reference to the flowchart shown in FIG. First, it is determined whether or not the motor traction control (TRC control) is operating (step S1). The TRC control operates, for example, when the drive wheels 15 are slipping or when the difference in the number of rotations of the left and right drive wheels 15 is equal to or greater than a predetermined value. Therefore, if the TRC control is not operating and a negative determination is made in step S1, the system returns without executing the subsequent control.

On the contrary, when it is determined positively in this step S1, that is, when it is determined that the TRC control is in operation, the target slip ratio is calculated (step S2). As described above, this target slip ratio is a normal target slip ratio, and the slip ratio at which the vehicle Ve can output the maximum driving force is calculated.

Then, it is determined whether or not the previous hunting determination is ON (step S3). That is, it is determined whether or not the hunting determination is ON in the previous routine, and whether or not the hunting is currently (or already) hunted. The determination of whether or not hunting is performed is made based on, for example, whether or not the parameter for hunting determination (for example, the feedback correction amount of the motor rotation speed) exceeds a predetermined threshold value. Further, the determination may be made based on the integrated value of the motor rotation speed per unit time in the feedback control.

Therefore, if it is negatively determined in step S3, that is, if it is determined that the hunting determination is OFF because the feedback correction amount of the motor rotation speed is equal to or less than the threshold value, no further control is executed. Return. On the other hand, if it is positively determined in step S3, that is, if it is determined that the hunting determination is ON because the feedback correction amount of the motor rotation speed exceeds the threshold value, the target slip ratio is reduced. Make corrections (step S4).

This step S4 is a process of correcting the target slip rate calculated in step S2 described above, and when the hunting determination is determined to be ON, the process is corrected to the side that reduces the target slip rate. In other words, the slip ratio is corrected so as to grip the drive wheels 15. As described above, on a road surface having an extremely low μ, the motor rotation speed for which feedback control is executed may diverge or hunt with respect to the target rotation speed due to a slight control error or deviation, and slip of the drive wheels 15 may not be suppressed. .. Therefore, in this step S4, when it is determined that hunting has occurred, as shown in FIG. 4, the target slip ratio set in the normal state is reduced to the grip region side. This is configured to suppress hunting.

Here, the correction process for reducing the target slip ratio will be specifically described. For example, when it is determined that hunting has occurred, the uniformly set value is set to be reduced. Further, a value to be reduced may be set according to the magnitude of the value of the parameter when the hunting determination is made. In that case, the larger the value of the hunting determination parameter, the larger the value to be reduced is set. Further, a value to be reduced may be set according to the time when it is determined that hunting has occurred. In that case, the longer the hunting time is, the larger the value to be reduced is set. In addition, a value to be reduced may be set based on the magnitude of the value of the parameter for the hunting determination and the time for which the hunting is determined to occur.

Then, the target motor rotation speed is calculated based on the target slip ratio corrected in step S4 and the vehicle body speed (step S5). That is, the target motor rotation speed is calculated in order to control the target slip ratio. Then, after calculating the target motor rotation speed, the FB correction amount (rotation speed) for correcting the current motor rotation speed is calculated (step S6).

Then, the hunting determination parameter is calculated based on the correction of the motor rotation speed in step S6 (step S7). That is, the correction amount of the motor rotation speed per unit time of the rotation speed corrected in step S6 is calculated, or the correction amount and time after resetting the rotation speed corrected in the previous routine are calculated. Further, it is determined whether or not the calculated hunting determination parameter value is larger than a predetermined threshold value (step S8). That is, it is determined from the correction amount calculated in step S7 whether or not hunting is performed. In addition, this threshold value is set to the threshold value which can suppress the slip of the drive wheel 15.

Therefore, when a positive determination is made in step S8, that is, when it is determined that the value of the parameter for hunting determination is larger than the threshold value, the hunting determination is turned ON (step S9). That is, the hunting determination ON state that is ON in step S3 is maintained. On the contrary, when a negative determination is made in step S8, that is, when it is determined that the value of the parameter for hunting determination is equal to or less than the threshold value, the hunting determination is turned off (step S10). That is, since it can be determined that the occurrence of hunting with respect to the target rotation speed has been suppressed, the hunting determination is turned from ON to OFF.

After calculating the FB correction amount of the motor rotation speed in step S6 described above, the motor torque is output in parallel with step S7. A subroutine that is executed in parallel is shown in FIG. Specifically, after calculating the FB correction amount of the motor rotation speed in step S6, the motor torque is calculated and output based on the calculation (step S100). That is, the motor torque is output in accordance with the steps S4 to S9 to be executed when the hunting determination is ON.

FIG. 6 is a diagram for explaining a time chart when the control example of FIG. 3 described above is executed, and shows an example of a case where the vehicle runs from the time of starting or accelerating and hunts. Specifically, the vehicle body speed (and wheel speed), the correction amount of the FB control of the motor rotation speed, and the change of the parameter value of the hunting determination are shown. As a premise, the motor rotation speed is controlled so as to be the FB target value of the motor rotation speed. Then, when there is a deviation from the FB target value, the correction amount of the motor rotation speed is calculated, and the actual motor rotation speed is corrected accordingly. At the same time, the correction amount is calculated and the correction process is performed while performing the hunting determination. As described above, the parameter for hunting determination is, for example, the amount of correction of the motor rotation speed per unit time.

First, at t1, the drive wheels 15 are slipping due to the acceleration or start of the vehicle Ve. Therefore, in order to suppress the slip of the drive wheel 15 and grip it, the FB correction amount of the rotation speed of the motor is calculated and corrected. Since it is assumed in advance that the parameters in the hunting determination will overshoot the threshold value at the time of starting or accelerating, the values of the parameters at the time of starting or accelerating are masked and kept constant.

From the time t2 to the time t3, the motor rotation speed is hunted with respect to the FB target value of the motor, but since the parameter value in the hunting determination is equal to or less than the threshold value, the control is controlled so as to have a predetermined target slip ratio. Will be done.

Then, it is determined that if the parameter value of the hunting determination exceeds the threshold value at t3, hunting may not be suppressed, or divergence may occur even when FB correction is performed. That is, since the hunting determination is turned ON, a correction process is performed to reduce the target slip ratio toward the grip side. Then, based on the hunting determination being turned ON, a correction for reducing the FB target value of the motor rotation speed is performed (at the time of t4), and the motor rotation speed is controlled so as to match the corrected target rotation speed.

Then, by reducing the target slip ratio and controlling the motor rotation speed to the FB target value, divergence and hunting with respect to the FB target value are suppressed (from t4 to t5). In addition, the FB correction amount becomes smaller accordingly. Then, when the parameter value of the hunting determination reaches the threshold value or less, the hunting determination is turned off (at t5). While the parameter value of the hunting determination exceeds the threshold value, the above correction control is repeatedly executed.

In addition to the case where the parameter value of the hunting determination is equal to or less than the threshold value, the determination of whether or not to turn off the hunting determination is performed, for example, a determination value for resetting the correction amount in which the parameter of the hunting determination is an integrated value. It may be determined that it is OFF when the timing falls below. Further, the hunting determination may be turned off when the acceleration request from the driver is once completed, that is, when the required driving force obtained from the accelerator off timing or the accelerator opening degree becomes "0". In addition, the hunting determination may be turned off at the timing when the slip control ends.

Next, the action and effect in the embodiment of the present invention will be described. As described above, in the embodiment of the present invention, when the actual motor rotation speed (actual rotation speed) is hunting with respect to the target rotation speed, a correction process for reducing a predetermined target slip ratio is executed. It is configured to do. That is, it is configured to reduce the target slip value on the grip side. Therefore, even when hunting occurs, the motor rotation speed converges with respect to the FB target value, and as a result, the generated hunting can be suppressed. Further, by suppressing the hunting in this way, it is possible to suppress the slip of the drive wheels 15 and to prevent the behavior of the vehicle Ve from becoming unstable.

Further, in the embodiment of the present invention, it is configured to execute the above correction control after making a hunting determination, in other words, capturing the fact of hunting. Therefore, hunting can be suppressed without performing unnecessary control. Further, since the above correction control is performed until the hunting converges, it is possible to reliably suppress the hunting that has occurred. Since the above control example is executed based on the determination of hunting, it is assumed that hunting occurs several times, but the hunting several times does not affect the behavior of the vehicle Ve.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned examples, and may be appropriately modified as long as the object of the present invention is achieved. In the control example described above, when hunting occurs, the correction process for reducing the target slip ratio is executed, but instead, hunting generated by, for example, lowering the feedback gain is suppressed and the vehicle. You may try to stabilize the behavior of Ve.

1 ... Engine, 2 ... 1st motor, 3 ... 2nd motor, 4 ... Power split mechanism, 5 ... Sun gear, 6 ... Carrier, 7 ... Ring gear, 8 ... Output gear, 9 ... Counter shaft, 10 ... Driven gear, 11 ... Drive gear, 12 ... differential gear, 13 ... ring gear, 14 ... drive gear, 15 ... drive wheel, 16 ... power supply unit, 17 ... electronic control device (ECU), Ve ... vehicle.

Claims (1)

In a vehicle control device that includes at least a motor as a driving force source and is configured to reduce the torque of the motor when the driving wheels slip to grip the slipped driving wheels.
A controller for controlling the vehicle is provided.
The controller
When the drive wheels slip, the rotation speed of the motor is controlled so as to have a predetermined target slip ratio.
It is determined whether or not the actual rotation speed of the motor is hunting beyond a predetermined range determined in advance with respect to the rotation speed of the motor based on the target slip ratio.
When it is determined that the hunting has occurred, the target slip ratio is lowered, and the target rotation speed of the motor is calculated based on the lowered target slip ratio.
A vehicle control device characterized in that the actual rotation speed of the motor is controlled to the target rotation speed.

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