JP2018129890A - Output control device of vehicle - Google Patents

Abstract

A vehicle output control device that enables a driver to control wheel slip even on a slippery road surface or the like. A vehicle output control apparatus calculates a slip ratio S of a wheel from a required torque deriving unit 22 for deriving a required torque Тreq from at least an accelerator pedal depression amount A, an estimated vehicle speed BV, and a wheel speed ω. Slip rate calculation unit 23, estimated slip speed calculation unit 24 that calculates an estimated slip speed α from the required torque derived from the required torque deriving unit and the road surface reaction force torque Т1, and at least road surface reaction force torque and slip rate calculation A target slip speed calculation unit 25 for obtaining a target slip speed αtgt from two of the slip ratios calculated by the unit, and a target control amount calculation unit 26 for obtaining a target damping control amount ΔT from the estimated slip speed and the target slip speed. And the rotational torque of the electric motor 2 is controlled so that the running torque Tout obtained from the target damping control amount and the required torque is obtained. [Selection] Figure 2

Description

  The present invention relates to a vehicle output control device.

An electric vehicle that is driven by a motor, which is an electric motor, generally has a feature that the inertia of a drive shaft is smaller than that of an engine vehicle. This is because the rotational inertia of the motor is small compared to the rotational inertia of the engine. However, the small drive shaft inertia has the advantage of good response to torque, but on the other hand, at the time of starting a small shock or wheel slip Accelerator control is difficult.
Thus, there is known an output control device that controls the output of the drive side so that the wheel grips when the wheel slips (for example, Patent Document 1).

JP 2004-320852 A

In the conventional configuration, output control is performed after the wheel slips, but this output control is a control that largely suppresses the torque for the purpose of securing traction, and the slip control of the wheel by the driver on a slippery road surface or the like. You can't assist.
It is an object of the present invention to enable wheel slip control by a driver even on a slippery road surface or the like.

  In order to solve the above problem, an output control device for a vehicle that travels by transmitting rotation of an electric motor to wheels according to the present invention includes a required torque deriving unit that derives a driver's required torque from at least an accelerator pedal depression amount. An estimated slip speed calculation that calculates an estimated slip speed of a wheel from a required torque and a road surface reaction torque calculated by a required torque deriving unit, a slip ratio calculating unit that calculates a wheel slip ratio from the estimated vehicle speed and wheel speed A target slip speed calculation unit that obtains a target slip speed from at least two of the road surface reaction force torque and the slip ratio calculated by the slip ratio calculation unit, and a target damping control amount from the estimated slip speed and the target slip speed. A target control amount calculation unit to be obtained, and a target damping control amount obtained by the target control amount calculation unit and a required torque deriving unit As the traveling torque obtained from the calculated torque is characterized by controlling the rotation torque of the motor.

  ADVANTAGE OF THE INVENTION According to this invention, the slip control of the wheel by a driver can be enabled also on the road surface etc. which are easy to slip.

The schematic block diagram of the vehicle provided with the output control apparatus which concerns on this invention. The block diagram explaining the structure of one Embodiment of the output control apparatus which concerns on this invention. The flowchart explaining one form of control by an output control apparatus. The figure which showed typically the content of the output control performed in this embodiment. (A)-(c) is a figure explaining the form of the drive format of a vehicle. The block diagram explaining the structure of the modification 1 of the output control apparatus which concerns on this invention. The block diagram explaining the structure of the modification 2 of the output control apparatus which concerns on this invention.

Hereinafter, embodiments and modifications of the present invention will be described with reference to the drawings. In the embodiments for carrying out the invention, the same members and members having the same functions are denoted by the same reference numerals, and redundant description is omitted. The drawings may be partially omitted to facilitate understanding of some configurations.
In FIG. 1, the vehicle denoted by reference numeral 1 travels by transmitting output torque (output rotation) from a motor 2, which is an electric motor, to a rear wheel 5 that is a driving wheel via a transmission 3 and a rear axle 4. It is an example of the electric vehicle. The wheels driven by the motor 2 may not be the rear wheels 5 but may be the front wheels 8 and 8 operated by operating the steering 7. Electric power from the battery 6 serving as a power source is supplied to the motor 2 via a controller 20 as an output control device, an inverter (not shown), and the like.

  In the vehicle 1, a wheel speed sensor 11 is disposed in the vicinity of each wheel as wheel speed detecting means for detecting and outputting the wheel speed ω of each wheel of the front wheel 8 and the rear wheel 5. The vehicle 1 is provided with an accelerator pedal sensor 12 that detects and outputs the depression amount A of the accelerator pedal 9 that adjusts the output of the motor 2. The vehicle 1 is provided with a steering angle sensor 13 as a steering angle detection means that detects and outputs a steering angle θ that is a rotation angle of the steering 7. The vehicle 1 is provided with a G sensor 14 as vehicle state detection means for detecting longitudinal acceleration and yaw rate and outputting vehicle information G such as acceleration and turning information. The wheel speed sensor 11, the accelerator pedal sensor 12, the steering angle sensor 13, and the G sensor 14 are connected to the controller 20 via signal lines.

The vehicle 1 is equipped with an output control device that controls the output of the motor 2. In the present embodiment, the output control device is the controller 20. As shown in FIG. 2, the controller 20 includes an estimated vehicle speed deriving unit 21, a required torque deriving unit 22, a slip ratio calculating unit 23, an estimated slip speed calculating unit 24, a target slip speed calculating unit 25, and a target control amount calculating unit 26. A running torque calculator 27 is provided.
The controller 20 is configured by a computer including a CPU that is a central processing unit, ROM and RAM that are storage units, a timer that is a measurement unit, and the like. The estimated vehicle speed deriving unit 21, the required torque deriving unit 22, the slip ratio calculating unit 23, the estimated slip speed calculating unit 24, the target slip speed calculating unit 25, the target control amount calculating unit 26, and the running torque calculating unit 27 are added to the controller 20. The function is allocated. Here, all functions are given to one controller 20, but an output control device may be configured by providing a computer and an IC circuit for each function individually.

The estimated vehicle speed deriving unit 21 has a function of estimating the moving speed of the vehicle body 1 from the wheel speed ω, etc., and calculating and outputting the estimated vehicle speed BV. Calculation of the estimated vehicle speed BV by the estimated vehicle speed deriving unit 21 is referred to as estimated vehicle speed calculation processing.
The required torque deriving unit 22 has a function of obtaining and outputting the required torque T _req requested by the driver from the depression amount A from the accelerator pedal sensor 12 or the like. _{Obtaining the} required torque T _req by the required torque deriving unit 22 is referred to as required torque derivation processing.
The slip ratio calculation unit 23 has a function of calculating and outputting the slip ratio S of the front wheel 8 or the rear wheel 5 that is a wheel from the wheel speed ω and the estimated vehicle speed BV. For example, the slip ratio calculation unit 23 is calculated by the following formula 1.
(Wheel speed ω−estimated vehicle speed BV) / estimated vehicle speed BV (Expression 1)
The wheel speed ω here is the average speed of the wheels driven by one drive source. That is, in this embodiment, since the rear wheels 5 and 5 are rotationally driven by the motor 2 serving as one drive source, the average value of the wheel speeds of the rear wheels 5 and 5 is set to the wheel speed ω. Obtaining the slip ratio S by the slip ratio calculation unit 23 is referred to as slip ratio calculation processing.

The estimated slip speed calculation unit 24 has a function of calculating and outputting the estimated slip speed α of the front wheels 8 and the rear wheels 5 that are wheels from the required torque T _req and the road surface reaction force torque Tl (estimated value). The estimated slip speed α is the wheel acceleration. The estimated slip speed calculation unit 24 calculates the estimated slip speed α by the following equation 2.
α = (T _req −Tl) / I (Expression 2)
I: Drive system inertia
ω: wheel speed T _req: driver's required torque Tl: road reaction torque
The calculation of the estimated slip speed α by the estimated slip speed calculation unit 24 is referred to as an estimated slip speed calculation process.

The target slip speed calculation unit 25 has a function of _obtaining and outputting the target slip speed α _tgt from the road surface reaction force torque Tl and the slip ratio S from the slip ratio calculation unit 23. The target slip speed α _tgt is the wheel acceleration. The target slip speed calculation unit 25 calculates the target slip speed α _tgt by the following equation 3 obtained from, for example, the target drive system inertia.
α _tgt = (T _req −Tl) / I _tgt (Equation 3)
I _tgt : Target drive system inertia T _req : Driver's required torque Tl: Road surface reaction force torque The target slip speed calculation unit 25 calculates the target slip speed α _tgt is referred to as a target slip ratio calculation process.

The target control amount calculation unit 26 has a function of _obtaining and outputting a target damping control amount ΔT from the estimated slip speed α and the target slip speed α _tgt . The target control amount calculation unit 26 calculates the target damping control amount ΔT by the following expression 4. The calculation of the target damping control amount ΔT by the target control amount calculation unit 26 is referred to as a target control amount calculation process.
ΔT = (α−α _tgt ) * I / Tl (Expression 4)

The running torque calculation unit 27 _obtains a running torque T _out obtained from the target control amount ΔT obtained by the target control amount calculation unit 26 and the requested torque T _req obtained by the required torque deriving unit 22, and the traveling torque and Thus, the function of controlling the rotational torque of the motor 2 is provided. The running torque calculation unit 27 calculates the running torque T _{out according} to the following formula 5.
T _out = (T _req −ΔT) (Formula 5)
The calculation of the travel torque T _out by the travel torque calculation unit 27 is referred to as a travel torque calculation process.
In other words, in this embodiment, in order to make it easier for the driver to control the slip speed (wheel acceleration) when the rear wheel 5 that is the wheel (drive wheel) slips, the target damping occurs when any wheel slips. The control amount ΔT is subtracted from the required torque T _req and the running torque T _out generated by the motor 2 is suppressed, thereby controlling the sensitivity of the accelerator petal.

  As shown in FIG. 1, the controller 20 includes a slip determination unit 30 that determines whether to perform output control from the slip rate S calculated by the slip rate calculation unit 23 and a threshold value S1 set in advance in, for example, a ROM. Yes. When the controller 20 determines that the slip determination unit 30 performs the output control, the controller 20 executes at least the estimated slip speed calculation process, the target slip ratio calculation process, the target control amount calculation process, and the travel torque calculation process to execute the travel torque of the motor 2. Suppress. It is assumed that equations (1) to (7) are stored in advance in the ROM of the controller 20.

FIG. 3 is a flowchart for explaining one form of control processing executed by the controller 20.
In step ST <b> 1, the controller 20 performs an information acquisition process for acquiring various information of the vehicle 1. Here, for example, the wheel speed ω and the vehicle body information G are acquired, and the process proceeds to step ST2. In step ST2, the controller 20 performs a required torque derivation process in the required torque deriving unit 22 to obtain the required torque T _req . In step ST3, the controller 20 calculates the estimated vehicle speed BV by executing the estimated vehicle speed processing in the estimated vehicle speed deriving unit 21, and proceeds to step ST4. In ST4, the controller 20 executes slip ratio calculation processing by the slip ratio calculation unit 23 to calculate the slip ratio S, and proceeds to step ST5.

In step ST5, the controller 20 determines whether or not the wheel is slipping based on the magnitude relationship between the slip rate S and the threshold value S1. Here, when the slip ratio S does not exceed the threshold value S1, the controller 20 determines that it is not slipping and does not execute output control, and ends this control routine. When the slip ratio S exceeds the threshold value S1, the controller 20 determines that the rear wheel 5 that is the drive wheel is slipping and needs output control, and proceeds to step ST6, where the running torque (rotational torque) of the motor 2 is determined. The output control process is started to suppress this. In the present embodiment, the output control process is an estimated slip speed calculation process, a target slip ratio calculation process, a target control amount calculation process, and a running torque calculation process.
In step ST6, the controller 20 performs an estimated slip speed calculation process by the estimated slip speed calculation unit 24 to calculate an estimated slip speed α, and in step ST7, the target slip speed calculation unit 25 executes a target slip speed calculation process. A target slip speed α _tgt is calculated. Either the estimated slip speed α or the target slip speed α _tgt may be calculated first.
In step ST8, the controller 20 executes target control amount calculation processing by the target control amount calculation unit 26 to calculate the target damping control amount ΔT, and proceeds to step ST9. The controller 20, in step ST9, travels by running the running torque calculation processing to calculate the running torque _{T out} at the torque calculating unit 27, in step ST10, the direction to suppress the output of the motor 2 so that the driving torque _{T out} To control.

FIG. 4 is a diagram schematically showing the contents of the output control performed in the present embodiment.
The vehicle 1 that travels with the motor 2 has a small response to the torque because the rotational inertia of the motor 2 is small relative to the rotational inertia of the engine. However, there is a problem that it is difficult to control the accelerator at the time of starting the minute shock or the wheel slip. . That is, when the estimated slip speed α rises faster than the estimated vehicle speed and the driver notices, the wheel often slips more than the driver expects. This state is the non-control state of FIG. For this reason, in this embodiment, when a wheel (rear wheel 5 which is a driving wheel) slips, the controller 20 controls the output of the motor 2 by reducing the slip speed (wheel acceleration), and the motor torque is reduced. I tried to suppress it.
As described above, when slip occurs on the wheel (rear wheel 5 which is a driving wheel), the controller 20 controls the output of the motor 2 so as to suppress the motor torque. Slip of the wheels 5 and 5 can be suppressed, and even in a slip state, accelerator control is facilitated by the driver's intention.
In addition, if the wheel slips as in the conventional output control, the output is controlled not to suppress the output uniquely and prevent the occurrence of slip, but to reduce the degree of slip in the slip state. Even under the control, the output of the motor 2 can be adjusted by controlling the accelerator. For this reason, for example, even when the vehicle 1 is stacked, torque adjustment (slip speed adjustment) for the drive wheels can be performed by the driver's accelerator work. That is, the driver can control the slip of the wheel even on a slippery road surface.

Here, the difference between this embodiment and the traction control which is one of what controls the slip of a wheel is demonstrated. In traction control, when an arbitrary wheel slips and the slip ratio exceeds an arbitrary value, control is generally performed to suppress the output so that the wheel grips. That is, when a wheel slips, control is performed so as not to slip by suppressing the rotational torque on the drive side so that a certain amount of rotational torque is not generated in the wheel under any circumstances. In the case of such control, since the slip rate is suppressed to a constant regardless of the depression amount of the accelerator pedal 9, the output torque is limited to a range where slipping does not occur. Since the driving force is not transmitted to the road surface when stacked, it cannot come out. Further, even when the driver is depressing the accelerator pedal 9, the driving torque that idles with respect to the wheels cannot be transmitted due to the torque limitation, so that the driver cannot accelerate while slipping.
On the other hand, in this embodiment, when the rear wheels 5 and 5 which are driving wheels slip, in the case of a slip ratio exceeding a certain level, the motor torque is suppressed so that the slip ratio is reduced and the slip ratio is reduced. Decrease the slip speed to suppress it more than when control starts. Thus, at the time of slip, the motor torque is controlled so as to suppress the slip ratio by reducing the response of the motor torque to the accelerator pedal operation. At this time, since the suppression of the slip ratio is moderated, it is possible to give time for the driver to determine the accelerator pedal operation.

In the above embodiment, the vehicle 1 has been described as a rear-wheel drive vehicle in which the rear wheels 5 and 5 are driven by the single motor 2, but another form may be employed as the drive form. FIGS. 5A to 5C are diagrams simply showing other driving methods. FIG. 5A shows a form of a four-wheel drive vehicle that travels by driving the front wheels 8 and 8 and the rear wheels 5 and 5 to rotate by individual motors 2A and 2B, respectively. FIG. 5B shows a form of a four-wheel drive vehicle that travels by rotating the front wheels 8 and 8 and the rear wheels 5 and 5 with one motor 2. FIG. 5C shows a form of a four-wheel drive vehicle in which all four wheels (front wheels 8, 8 and rear wheels 5, 5) are driven to rotate by individual motors 2A to 2D.
When the output control for suppressing the rotational torque of each motor at the time of slip by the controller 20 as the output control device is applied to these vehicles, the wheel speed ω is the average speed of the wheels driven by one drive source. And That is, in the case of the form of FIG. 5A, the average speed of the left and right front wheels 8, 8 or the average speed of the left and right rear wheels 5, 5 is set as the wheel speed ω. In the case of the form of FIG. 5B, the average speed of the left and right front wheels 8, 8 and the left and right rear wheels 5, 5 is defined as a wheel speed ω. In the case of the form shown in FIG. 5C, the four wheels may be controlled individually using the wheel speeds ω of the four wheels.

(Modification 1)
FIG. 6 is a block diagram showing a configuration of Modification 1 of the present embodiment. In this modified example, the target damping control amount ΔT calculated by the target control amount calculating unit 26 is corrected and calculated for each wheel speed ω with respect to the embodiment shown in FIG.
For example, when this control is performed in the vehicle 1 that drives a plurality of wheels described with reference to FIGS. 5A to 5C with a motor, the control is performed to prevent torque suppression of other wheels. In other words, in the case of four-wheel drive, since all wheels are drive wheels, if the rotational torque of each motor is suppressed according to the slip rate of any one drive wheel, However, since the slip speed is reduced, the acceleration performance and the torque distribution during stacking change. However, in the first modification, it is possible to avoid the loss of driving force by monitoring all of the plurality of wheel speeds to be driven and calculating the target damping control amount ΔT individually according to the wheel speed ω of each wheel. This is preferable because it is possible.
In the first modification, the target damping control amount ΔT is calculated by correcting for each wheel speed ω using the following equation (6).
ΔT = k * (α−α _tgt ) * I / Tl (Expression 6)
Note that k is determined according to the drive target wheel in consideration of the characteristics of the drive system components. For example, k is a correction coefficient that is determined by a map using the wheel speed difference between the front and rear axes and the wheel speed difference between the left and right as inputs. For this reason, it is preferable to store Equation 6 and the map in advance in the ROM of the controller 20.

(Modification 2)
FIG. 7 is a block diagram showing a configuration of Modification 2 of the present embodiment. In the above-described embodiment, the state at the time of turning of the vehicle 1 is not taken into consideration, and it is assumed that the wheel slips mainly at the time of straight traveling, but in a modified example, the embodiment shown in FIG. The target damping control amount ΔT calculated by the target control amount calculation unit 26 is calculated by correcting with the lateral acceleration information. The lateral acceleration information here is vehicle body information G, steering angle θ, and estimated vehicle speed BV. The vehicle body information G is a yaw rate or a lateral G.
In the second modification, correction is performed using Equation 7 below according to the lateral G or the estimated lateral G (calculated from the steering angle, the estimated vehicle body speed, and the yaw rate).
ΔT = k * (α−α _tgt ) * I / Tl (Expression 7)
Note that k is a correction coefficient determined by a map using the lateral G and the estimated lateral G as inputs. For this reason, it is preferable to store Equation 7 and the map in advance in the ROM of the controller 20.
Thus, when the target damping control amount ΔT calculated by the target control amount calculating unit 26 is corrected according to the lateral acceleration, the target damping control is performed in consideration of the slip ratio of each wheel that changes when the vehicle 1 turns. Since the amount ΔT can be calculated, loss of driving force during turning can be avoided, and the turning performance is also stabilized, which is preferable.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to this specific embodiment, Unless it is specifically limited by the above-mentioned description, this invention described in the claim is described. Various modifications and changes are possible within the scope of the gist of the invention.

  The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Electric motor, 5, 5 ... Rear wheel (wheel), 8, 8 ... Front wheel (wheel), 9 ... Accelerator pedal, 20 ... Output control apparatus, 22 ... required torque deriving unit, 23 ... slip rate calculating unit, 24 ... estimated slip speed calculating unit, 25 ... target slip speed calculating unit, 26 ... target control amount calculating unit, .. Depression amount, BV ... Estimated vehicle speed (lateral acceleration information), Т _req ... Required torque, ω ... Wheel speed, α ... Estimated slip speed, α _tgt ... Target slip speed, S: slip ratio, Tl: road reaction force torque, ΔT: target damping control amount, T _out: travel torque, G: vehicle body information (lateral acceleration information), θ: steering Angle (lateral acceleration information)

Claims (3)

An output control device for a vehicle that travels by transmitting rotation of an electric motor to wheels,
A required torque deriving unit for deriving a driver required torque from at least the accelerator pedal depression amount;
A slip ratio calculator for calculating the slip ratio of the wheel from the estimated vehicle speed and the wheel speed;
An estimated slip speed calculating unit that calculates an estimated slip speed of the wheel from the required torque and road surface reaction force torque derived by the required torque deriving unit;
A target slip speed calculation unit for obtaining a target slip speed from at least two of the road surface reaction force torque and the slip ratio calculated by the slip ratio calculation unit;
A target control amount calculation unit for obtaining a target damping control amount from the estimated slip speed and the target slip speed;
A vehicle output control device that controls the rotational torque of the electric motor so as to obtain a running torque obtained from the target damping control amount obtained by the target control amount calculating unit and the required torque obtained by the required torque deriving unit. .   The vehicle output control apparatus according to claim 1, wherein the target damping control amount is corrected according to the wheel speed.   The vehicle output control apparatus according to claim 1, wherein the target damping control amount is corrected according to lateral acceleration information of the vehicle.

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