JP2011130629A - Differential limit control device for electric vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a differential limit control device for an electric vehicle, for suppressing vehicle vibration or a change in drive force, in executing differential limiting between front and rear axles and between right and left wheels. <P>SOLUTION: The control device computes an actual rotation speed difference and a target rotation speed difference between the wheels, computes correction torque for causing the actual rotation speed difference to follow the target rotation speed difference, computes the maximum differential limit torque for limiting the maximum value of the correction torque, computes a limiter output obtained by limiting the upper limit value of the absolute value of the correction torque by the maximum differential limit torque, adds the limiter output to either of the target drive torques distributed from the total drive torque, and subtracts the limiter output from the other. The controller controls an electric motor so that the torque is obtained, and executes differential limiting. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a differential limiting control device that limits differential between front and rear shafts and left and right wheels of an electric vehicle.

  As a technique for controlling the driving force of the longitudinal axis of the vehicle, for example, a technique disclosed in Patent Document 1 is known.

Japanese Patent No. 3826247

  In Patent Document 1 (particularly, refer to paragraphs 0076 to 0096, FIGS. 6 to 8 and the like), when either the front wheel or the rear wheel is slipping, the required torque of the slipping wheel is reduced. Correction to make. However, the differential limitation itself that limits the differential between the front and rear axes is not performed. Considering that the technology shown in Patent Document 1 is applied to an electric vehicle in which the front and rear shafts are independently driven by an electric motor to limit the differential between the front and rear shafts, an electronically controlled LSD (Limited Slip Differential Gear) is used. In order to obtain the same effect as the differential limiting control between the front and rear axes by the used initial torque, it is necessary to increase the torque correction gain and improve the control response. As a result, control responsiveness is enhanced, but the torque correction amount becomes large, so that there is a problem that the control amount becomes oscillating, causing vehicle vibration and driving force change.

  Such a problem is similar in an electric vehicle in which the left and right wheels are independently driven by an electric motor.When limiting the differential between the left and right wheels, if the torque correction gain is increased and the control responsiveness is increased, Since the torque correction amount becomes large, the control amount becomes oscillating, causing vehicle vibrations and driving force changes.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a differential limiting control device for an electric vehicle that suppresses vehicle vibration and changes in driving force when differential limiting is performed between front and rear axes and between left and right wheels. And

A differential limiting control device for an electric vehicle according to a first invention for solving the above-described problem is
As a power source for driving the first wheel, it has at least an electric motor,
As a power source for driving the second wheel, it has at least another electric motor,
A differential restriction control device that controls the electric motor and the other electric motor to perform differential restriction between the first wheel and the second wheel;
The differential limiting control device includes:
According to the driver's acceleration request, calculate the total driving torque of the vehicle,
According to the vehicle state and the operation state of the driver, the total drive torque is respectively distributed to the target first wheel drive torque to the first wheel and the target second wheel drive torque to the second wheel,
From the actual rotational speed of the first wheel and the actual rotational speed of the second wheel, the actual rotational speed difference between the first wheel and the second wheel is calculated,
Based on the vehicle speed and steering angle of the vehicle, a target rotational speed difference between the first wheel and the second wheel is calculated,
Calculating a correction torque for causing the actual rotational speed difference to follow the target rotational speed difference;
Based on the operation state of the driver, the maximum differential limit torque that limits the maximum value of the correction torque is calculated,
A limiter output obtained by limiting the upper limit of the absolute value of the correction torque with the maximum differential limiting torque is calculated,
The limiter output is added to one of the target first wheel drive torque and the target second wheel drive torque, and the limiter output is subtracted from the other to limit the first wheel drive torque and the limit second wheel drive. Calculate the torque,
The electric motor is controlled so as to be the limited first wheel driving torque, and the other electric motor is controlled so as to be the limited second wheel driving torque, thereby performing differential limitation. And

A differential limiting control device for an electric vehicle according to a second invention that solves the above-described problem,
As a power source for driving the front shaft, it has at least an electric motor,
As a power source for driving the rear shaft, it has at least another electric motor,
A differential limiting control device that controls the electric motor and the other electric motor to perform differential limiting between the front shaft and the rear shaft;
The differential limiting control device includes:
According to the driver's acceleration request, calculate the total driving torque of the vehicle,
According to a vehicle state and a driver's operation state, the total drive torque is distributed to the target front shaft drive torque to the front shaft and the target rear shaft drive torque to the rear shaft, respectively.
From the actual rotational speed of the front shaft and the actual rotational speed of the rear shaft, the actual rotational speed difference between the front and rear axes, which is the actual rotational speed difference between the front shaft and the rear shaft, is calculated.
Based on the vehicle speed and steering angle of the vehicle, a target rotational speed difference between the front shaft and the rear shaft is calculated,
Calculate a correction torque for causing the actual front-rear shaft rotational speed difference to follow the target rotational speed difference,
Based on the operation state of the driver, the maximum differential limit torque that limits the maximum value of the correction torque is calculated,
A limiter output obtained by limiting the upper limit of the absolute value of the correction torque with the maximum differential limiting torque is calculated,
Of the target front shaft drive torque and the target rear shaft drive torque, the limiter output is added to the shaft with the lower rotational speed, and the limiter output is subtracted from the shaft with the higher rotational speed, before the limit. Calculate shaft drive torque and post-restricted shaft drive torque,
The electric motor is controlled so as to be the pre-restricted shaft driving torque, and the other electric motor is controlled so as to be the post-restricted shaft driving torque to perform differential limitation. .

A differential limiting control device for an electric vehicle according to a third invention for solving the above-described problem is
As a power source for driving the right wheel, it has at least an electric motor,
As a power source for driving the left wheel, it has at least another electric motor,
A differential limiting control device that controls the electric motor and the other electric motor to perform differential limiting between the right wheel and the left wheel;
The differential limiting control device includes:
According to the driver's acceleration request, calculate the total driving torque of the vehicle,
According to the vehicle state and the driver's operation state, the total drive torque is respectively distributed to the target right wheel drive torque to the right wheel and the target left wheel drive torque to the left wheel,
From the actual rotational speed of the right wheel and the actual rotational speed of the left wheel, an actual left-right wheel rotational speed difference that is the actual rotational speed difference between the right wheel and the left wheel is calculated,
Based on the vehicle speed and steering angle of the vehicle, a target rotational speed difference between the right wheel and the left wheel is calculated,
Calculating a correction torque that causes the difference between the actual left and right wheel rotational speeds to follow the target rotational speed difference;
Based on the operation state of the driver, the maximum differential limit torque that limits the maximum value of the correction torque is calculated,
A limiter output obtained by limiting the upper limit of the absolute value of the correction torque with the maximum differential limiting torque is calculated,
The limiter output is added to the target right wheel drive torque to calculate a limited right wheel drive torque, and the limiter output is subtracted from the target left wheel drive torque to calculate a limit left wheel drive torque.
The electric motor is controlled so as to be the limited right wheel drive torque, and the other electric motor is controlled so as to be the limited left wheel drive torque, thereby performing differential limitation.

A differential limiting control device for an electric vehicle according to a fourth aspect of the present invention for solving the above-described problem is
In the differential limiting control device for an electric vehicle according to any one of the first to third inventions,
The differential limiting control device includes:
The maximum differential limiting torque is calculated using a first map in which the maximum differential limiting torque increases according to an increase in the driver's acceleration request,
A correction coefficient for correcting the maximum differential limiting torque is calculated using a second map in which the correction coefficient decreases from 1 to 0 in accordance with an increase in the absolute value of the steering angle;
The maximum differential limit torque and the correction coefficient are integrated to calculate a torque difference upper limit value for limiting the correction torque,
The upper limit value of the absolute value of the correction torque is limited by the torque difference upper limit value, and the limiter output is calculated.

  According to the present invention, even if high gain follow-up control is performed and the correction torque for the target rotational speed difference is calculated, the upper limit of the calculated correction torque is limited, and the motor torque based on the limited correction torque is used. Since the motor is controlled, the response of the motor torque and the convergence to the target value are improved. As a result, an effect equivalent to the differential limiting control by the initial torque using the electronic control LSD can be obtained, and the stability and the traction performance can be improved. Further, when the target rotational speed difference is set to 0, the same effect as the electronic control LSD can be obtained, so that the straight running stability is improved.

  In addition, according to the present invention, since the target rotational speed difference calculated from the vehicle speed and the steering angle is used, the differential limiting torque difference acts as much as the actual vehicle body posture deviates from the target vehicle body posture, smooth turning and excellent stability. Both sexes can be achieved.

1 is a schematic configuration diagram illustrating an example of an embodiment of a differential limiting control device for an electric vehicle according to the present invention. It is a block diagram explaining the differential limiting control apparatus of the electric vehicle shown in FIG. It is a map used with the differential limiting control apparatus of the electric vehicle which concerns on this invention, (a) calculates the maximum differential limiting torque with respect to a drive torque, (b) calculates the correction coefficient with respect to a steering angle. It is. It is a schematic block diagram explaining another example of embodiment of the differential limiting control apparatus of the electric vehicle which concerns on this invention. It is a block diagram explaining the differential limiting control apparatus of the electric vehicle shown in FIG.

  Hereinafter, some of the embodiments of the differential limiting control device for an electric vehicle according to the present invention will be described with reference to FIGS.

  The differential limiting control device for an electric vehicle according to the present invention is applied to an electric vehicle having a plurality of power sources and using at least an electric motor as the power source. “At least” means that an electric motor may be included as a power source. For example, an electric motor and an internal combustion engine (engine) may be combined and used as a power source. The object to be controlled at the time of differential limitation is an electric motor. In addition, “a plurality of power sources” may be configured such that the front and rear shafts are independently driven by each of a plurality of power sources (a plurality of electric motors) as shown in Example 1 (see FIG. 1) described later. Alternatively, as shown in a second embodiment (see FIG. 4) to be described later, the left and right wheels may be independently driven by each of a plurality of power sources (a plurality of electric motors).

Example 1
FIG. 1 is a schematic configuration diagram illustrating a differential limiting control device for an electric vehicle according to the present embodiment. FIG. 2 is a block diagram for explaining the differential limiting control device shown in FIG. 1, and FIG. 3 is a map used in the differential limiting control device of the present invention.

  An electric vehicle 10 shown in FIG. 1 is connected to a front shaft 13 via a front shaft 13 that drives a front left wheel 11 and a front right wheel 12 and a differential gear 14, and serves as a power source for the front shaft 13. A rear shaft 18 that drives a shaft motor 15 (electric motor), a rear left wheel 16 and a rear right wheel 17, and a differential gear 19 is connected to the rear shaft 18 and serves as a power source for the rear shaft 18. It has a shaft motor 20 (another electric motor). In the present embodiment, the front left wheel 11 and the front right wheel 12, that is, the front shaft 13 side are the first wheels, and the rear left wheel 16 and the rear right wheel 17, that is, the rear shaft 18 side are the second wheels.

  Then, the front shaft motor 15 and the rear shaft motor 20 are controlled by the differential restriction control device 21 to perform differential restriction between the front and rear axes, which will be described later. Here, the differential gear 14 transmits the output from the front shaft motor 15 to the left wheel 11 and the right wheel 12 as a driving force, and adjusts the rotational speed difference between the left wheel 11 and the right wheel 12. The gear 19 transmits the output from the rear shaft motor 20 to the left wheel 16 and the right wheel 17 as a driving force, and adjusts the difference in rotational speed between the left wheel 16 and the right wheel 17.

  Next, the function and control of the differential limiting control device 21 will be described with reference to FIGS.

  The differential limit control device 21 includes a total drive torque calculation means B1, a torque distribution calculation means B2, a front shaft drive torque → front shaft motor torque conversion means B3, a front shaft motor control means B4, and a target rotational speed difference calculation. Means B5, actual front shaft speed calculating means B6, actual rear shaft speed calculating means B7, target speed difference tracking control means B8, torque difference upper limit value calculating means B9, limiter B10, rear shaft drive Torque → rear shaft motor torque conversion means B11 and rear shaft motor control means B12.

  The sensor group A1 detects, for example, a vehicle speed sensor that detects a vehicle speed, an accelerator opening sensor that detects an accelerator opening, a steering angle sensor that detects a steering angle of a steering wheel, and an actual rotational speed from the wheel speed of each wheel. A wheel speed sensor, a longitudinal acceleration sensor for detecting longitudinal acceleration (both not shown), and the like, and a calculation described later is performed using the detected sensor value.

The total drive torque calculation means B1 calculates the total drive torque in response to the driver's acceleration request. Specifically, based on the vehicle speed and the accelerator opening detected by the vehicle speed sensor and the accelerator opening sensor, the total driving torque is obtained by a function F1 having the vehicle speed and the accelerator opening as variables as shown in the following formula. .
Total drive torque = F1 (vehicle speed, accelerator opening)

In the torque distribution calculation means B2, the total drive torque calculated by the total drive torque calculation means B1 is distributed as a target drive torque to each of the front shaft 13 and the rear shaft 18 according to the vehicle state and the operation state of the driver. ing. The target front shaft drive torque to be distributed to the front shaft 13 may be obtained by a function F2 or F3 having the vehicle state or the driver's operation state as a variable (for example, the following formulas (1) and (2)), or the vehicle May be obtained according to the load distribution ratio (fixed value) of (the following formula (3)).
Target front shaft drive torque = total drive torque × F2 (accelerator opening or drive torque) (1)
Target front shaft drive torque = total drive torque × F3 (longitudinal acceleration) (2)
Target front shaft drive torque = total drive torque x load distribution ratio (fixed value) (3)

Then, the target rear shaft drive torque to be distributed to the rear shaft 18 is obtained by the following equation using the target front shaft drive torque obtained using any one of the above equations (1) to (3).
Target rear shaft drive torque = Total drive torque-Target front shaft drive torque

  As will be described later, a correction torque is obtained for the distributed target front shaft drive torque and target rear shaft drive torque, but this correction torque is limited by the torque difference upper limit value, thereby Differential restriction will be performed.

The target rotational speed difference calculation means B5 calculates the target rotational speed difference according to the vehicle state and the driver's operation state. Specifically, based on the vehicle speed and the steering angle detected by the vehicle speed sensor and the steering angle sensor, the target rotational speed difference is obtained by a function F4 using the vehicle speed and the steering angle as variables, as shown in the following equations.
Target speed difference = F4 (vehicle speed, steering angle)
Note that the target rotational speed difference is 0 when the vehicle is running straight.

In the actual front shaft speed calculating means B6 and the actual rear shaft speed calculating means B7, the actual speeds of the front shaft 13 and the rear shaft 18 are obtained from the following equations using the wheel speed sensors of the respective wheels.
Actual front shaft speed = (front right wheel speed + front left wheel speed) / 2
Actual rear shaft speed = (rear right wheel speed + rear left wheel speed) / 2

In the actual front shaft speed calculating means B6 and the actual rear shaft speed calculating means B7, the motor speed detected by the front shaft motor 15 and the rear shaft motor 20 is used to determine the actual front shaft speed and the actual rear shaft speed. The rotational speed may be obtained.
Actual front shaft speed = front motor speed × factor Actual rear shaft speed = rear motor speed × factor

Then, in the calculator C1, by subtracting the actual rear shaft rotational speed obtained by the actual rear shaft rotational speed computing means B7 from the actual front shaft rotational speed obtained by the actual front shaft rotational speed computing means B6, the actual longitudinal axis The difference in rotational speed is obtained.
Difference between actual front and rear shaft speed = actual front shaft speed-actual rear shaft speed

The target rotational speed difference tracking control means B8 calculates a correction torque for controlling the actual rotational speed difference between the front and rear axes to follow the target rotational speed difference. Specifically, the target rotational speed difference obtained by the target rotational speed difference calculating means B5 and the actual front-rear shaft rotational speed obtained by the actual front shaft rotational speed calculating means B6, the actual rear shaft rotational speed calculating means B7 and the calculator C1. Based on the deviation from the number difference, as shown in the following equation, the correction torque for correcting the target front shaft drive torque and the target rear shaft drive torque is obtained by PID control.
Correction torque = PID (target speed difference-actual front-rear shaft speed difference)
The correction torque is limited by the torque difference upper limit value obtained by torque difference upper limit calculation means B9 described later.
Note that the correction torque is not limited to PID control, and may be obtained by other control methods such as H∞ control, fuzzy control, and the like. However, in this embodiment, the gain is set high in order to increase the responsiveness no matter what control is used.

  The torque difference upper limit calculation means B9 calculates an upper limit value (torque difference upper limit value) for the correction torque calculated by the target rotational speed difference follow-up control means B8 based on the vehicle state and the driver's operation state. Specifically, the torque difference upper limit value is calculated using the maps shown in FIGS. 3 (a) and 3 (b).

  A map 1 (first map) shown in FIG. 3A is a map for calculating a maximum differential limiting torque that limits the maximum value of the correction torque based on the total driving torque that is a driver's acceleration request. The maximum differential limiting torque is increased in proportion to the increase in the total driving torque. As shown in a map 2 in FIG. 3B described later, when the absolute value of the steering angle is 0, the correction coefficient for the maximum differential limiting torque is 1. A map 1 shown in FIG. 3A is obtained when the absolute value of the steering angle is 0, and is a maximum value that limits the correction torque.

  In place of the total driving torque, the maximum differential limiting torque may be calculated based on the accelerator opening that is the driver's acceleration request, and the map in that case is also proportional to the increase in the accelerator opening. The maximum differential limiting torque is increased. The accelerator opening is detected using an accelerator opening sensor.

  A map 2 (second map) shown in FIG. 3B is a map for calculating a correction coefficient for correcting the maximum differential limiting torque calculated in the map 1 based on the steering angle detected by the steering angle sensor. The correction coefficient is decreased from 1 to 0 in inverse proportion to the increase in the absolute value of the steering angle. When the absolute value of the steering angle is larger than a predetermined value, the correction coefficient is set to 0.

Then, in the torque difference upper limit calculation means B9, as shown in the following equation, the torque difference upper limit value is obtained by adding the correction coefficient calculated in Map 2 to the maximum differential limiting torque calculated in Map 1. .
Torque difference upper limit = (maximum differential limiting torque of MAP1) × (correction coefficient of MAP2)

In the limiter B10, the absolute value of the correction torque input from the target rotational speed difference follow-up control means B8 is limited to be equal to or less than the torque difference upper limit value calculated by the torque difference upper limit value calculation means B9. Specifically, a limiter output in which the upper limit of the absolute value of the correction torque is limited by the upper limit value of the torque difference is calculated using the following equation.
Limiter output L = max {(−torque difference upper limit value), min (torque difference upper limit value, correction torque)}

  In the arithmetic unit C2, the coefficient A is added to the limiter output L limited by the limiter B10, and a correction value [A × L] is output. The coefficient A is, for example, “0.5”, and the correction torque calculated by the target rotational speed difference follow-up control means B8 and the torque difference by this differential limiting control (specifically, an arithmetic unit to be described later) The difference between the pre-restricted shaft drive torque calculated in C3 and the post-restricted shaft drive torque calculated in the calculator C4 is made equal.

  The correction value [A × L] output from the calculator C2 is used to correct the target front shaft drive torque and the target rear shaft drive torque calculated by the torque distribution calculation means B2, and this is corrected with a high rotational speed. The target drive torque of each axis is corrected by subtracting it from the target drive torque of the axis and adding it to the target drive torque of the axis having the lower rotational speed. In the present embodiment, the following description will be made on the assumption that the rotational speed of the front shaft 13 is faster and the rotational speed of the rear shaft 18 is slower.

  The computing unit C3 subtracts the correction value [A × L] output from the computing unit C2 from the target front shaft driving torque computed by the torque distribution computing unit B2, thereby obtaining the final front shaft driving torque (limitation). On the other hand, the calculator C4 adds the correction value [A × L] output from the calculator C2 to the target rear axis drive torque calculated by the torque distribution calculator B2. Thus, the final rear shaft drive torque (restricted rear shaft drive torque) is output.

The front shaft drive torque → front shaft motor torque conversion means B3 converts the limited front shaft drive torque output from the computing unit C3 into the front shaft motor torque of the front shaft motor 15 using the following equation. The coefficient in this equation corresponds to the reduction ratio of the front shaft 13, and is, for example, coefficient = (1 / reduction ratio).
Front shaft motor torque = Limit front shaft drive torque x Factor

Similarly, the rear shaft driving torque → rear shaft motor torque converting means B11 converts the limited rear shaft driving torque output from the computing unit C4 into the rear shaft motor torque of the rear motor 20 using the following equation. ing. The coefficient in this equation corresponds to the reduction ratio of the rear shaft 18, and for example, coefficient = (1 / reduction ratio).
Rear shaft motor torque = Restricted rear shaft drive torque x coefficient

  The front shaft motor control means B4 controls the front shaft motor 15 so as to output the front shaft motor torque, and the rear shaft motor control means B12 controls the rear shaft motor so as to obtain the rear shaft motor torque. In this way, differential control is performed by controlling the front shaft motor 15 and the rear shaft motor 20.

  Here, with reference to FIG. 1 to FIG. 3, an outline of a control procedure for differential limitation in the differential limitation control device 21 will be described.

  The target front shaft drive that calculates the total drive torque according to the driver's acceleration request (vehicle speed, accelerator opening) and distributes it to each of the front shaft 13 and the rear shaft 18 according to the vehicle state and the driver's operation state. Torque and target rear shaft drive torque are obtained (see total drive torque calculation means B1 and torque distribution calculation means B2 in FIG. 2).

  Using the actual rotational speed of the front shaft 13 and the rear shaft 18, or the motor rotational speed of the front shaft motor 15 and the motor rotational speed of the rear shaft motor 20, the actual rotational speed difference between the front and rear axes is calculated (the front shaft actual speed in FIG. 2). (Refer rotation speed calculation means B6, rear-axis real rotation speed calculation means B7, and calculator C1).

  Based on the vehicle state (vehicle speed) and the driver's operation state (steering angle), the target rotational speed difference is calculated (see target rotational speed difference calculating means B5 in FIG. 2).

  Using the deviation of the actual front-rear shaft rotational speed difference from the target rotational speed difference, a correction torque for controlling the actual front-rear shaft rotational speed difference to the target rotational speed difference is calculated (target rotational speed difference tracking in FIG. 2). Control means B8). For example, the correction torque may be obtained by PID control.

  Based on the driver's operating state (total driving torque (or accelerator opening), steering angle), a torque difference upper limit value for the correction torque is calculated (torque difference upper limit calculation means B9 in FIG. 2 and FIG. 3 (a)). (See maps 1 and 2 in (b)). At this time, the maximum differential limiting torque that limits the maximum value of the correction torque is calculated based on the total driving torque or the accelerator opening, and the correction coefficient that corrects the maximum differential limiting torque is calculated based on the steering angle. The torque difference upper limit value is obtained by adding the correction coefficient to the maximum differential limit torque.

  A limiter process is performed to limit the absolute value of the correction torque to a torque difference upper limit value or less (see limiter B10 in FIG. 2).

  The coefficient A is added to the limiter output L subjected to the limiter process to output a correction value [A × L], and the correction value [A × L] is subtracted from the target front shaft drive torque calculated by the torque distribution calculation means B2. The final front shaft drive torque (restricted front shaft drive torque) is output, and the correction value [A × L] is added to the target rear shaft drive torque calculated by the torque distribution calculation means B2. The rear shaft driving torque (restricted rear shaft driving torque) is output (see the calculators C2, C3, and C4 in FIG. 2).

  The restricted front shaft drive torque is converted into the front shaft motor torque output by the front shaft motor 15 (see front shaft drive torque → front shaft motor torque conversion means B3 in FIG. 2), and the restricted rear shaft drive torque is converted to the rear shaft motor 20. Is converted into the rear shaft motor torque (see rear shaft drive torque → rear shaft motor torque conversion means B11 in FIG. 2).

  The front shaft motor 15 and the rear shaft motor 20 are controlled so as to output the converted front shaft motor torque and rear shaft motor torque, respectively, and differential limitation is performed (front shaft motor control means B4, rear shaft in FIG. 2). See motor control means B12).

  Even if high gain follow-up control is performed by the above-described control and the correction torque for the target rotational speed difference is calculated, the upper limit of the calculated correction torque is limited, and the front torque is calculated using the motor torque based on the limited correction torque. Since the motor 15 and the rear shaft motor 20 are controlled, the responsiveness of the motor torque and the convergence to the target value are improved. As a result, an effect equivalent to the differential limiting control by the initial torque using the electronic control LSD can be obtained, and the stability and the traction performance can be improved. Further, when the target rotational speed difference is set to 0, the same effect as the electronic control LSD can be obtained, so that the straight running stability is improved.

  In addition, the correction value [A × L] obtained by adding the coefficient A to the limited correction torque (limiter output L) by the control described above is used as one of the target front shaft drive torque and the target rear shaft drive torque (slow rotation speed). Therefore, even if differential limiting control is involved, the total drive torque does not change and smooth acceleration / deceleration can be realized.

  In the above-described control, the target rotational speed difference calculated from the vehicle speed and the steering angle is used, so that the differential limiting torque acts as much as the actual vehicle body posture deviates from the target vehicle body posture, smooth turning and excellent stability. Can be achieved.

(Example 2)
FIG. 4 is a schematic configuration diagram illustrating a differential limiting control device for an electric vehicle according to the present embodiment. FIG. 5 is a block diagram for explaining the differential limiting control device shown in FIG.

  An electric vehicle 30 shown in FIG. 1 has a front left wheel 31, a front right wheel 32, a front left wheel motor 33 serving as a power source for independently driving the front left wheel 31, and power for independently driving the front right wheel 32. Front right wheel motor 34 as a source, rear left wheel 35, rear right wheel 36, rear left wheel motor 37 as a power source for independently driving the rear left wheel 35, and rear right wheel 36 are driven independently. And a rear right wheel motor 38 as a power source. That is, the four wheels are independently driven by the electric motor.

  The rear right wheel motor 38 (electric motor) and the rear left wheel motor 37 (other electric motors) are controlled by a differential restriction control device 39. The control object of the differential limiting control device 39 is only the front left wheel motor 33 and the front right wheel motor 34, or only the rear left wheel motor 37 and the rear right wheel motor 38, the front left wheel motor 33, the front right wheel motor 34, and the rear left wheel. Although all of the motor 37 and the rear right wheel motor 38 may be used, in the present embodiment, in order to simplify the explanation, only the rear left wheel motor 37 and the rear right wheel motor 38 are described as control targets. That is, in the present embodiment, the rear right wheel 36 is the first wheel, and the rear left wheel 35 is the second wheel.

  Next, the function and control of the differential limiting control device 39 will be described with reference to FIG.

  The differential limit control device 39 includes total drive torque calculation means B21, torque distribution calculation means B22, rear right wheel drive torque → rear right wheel motor torque conversion means B23, rear right wheel motor control means B24, and target rotation. Number difference calculation means B25, actual rear right wheel rotation speed detection means B26, actual rear left wheel rotation speed detection means B27, target rotation speed difference tracking control means B28, torque difference upper limit value calculation means B29, limiter B30, Rear left wheel drive torque → rear left wheel motor torque conversion means B31 and rear left wheel motor control means B32.

  The sensor group A21 detects, for example, a vehicle speed sensor that detects a vehicle speed, an accelerator opening sensor that detects an accelerator opening, a steering angle sensor that detects a steering angle of a steering wheel, and an actual rotational speed from the wheel speed of each wheel. A wheel speed sensor, a yaw rate sensor that detects the yaw rate of the vehicle, a lateral acceleration sensor that detects the lateral acceleration of the vehicle (both not shown), and the like, and a calculation described later is performed using the detected sensor values.

The total drive torque calculation means B21 calculates the total drive torque in response to the driver's acceleration request. Specifically, based on the vehicle speed and the accelerator opening detected by the vehicle speed sensor and the accelerator opening sensor, the total driving torque is obtained by a function F1 having the vehicle speed and the accelerator opening as variables as shown in the following formula. .
Total drive torque = F1 (vehicle speed, accelerator opening)

In the torque distribution calculation means B22, the total drive torque calculated by the total drive torque calculation means B21 is distributed as a target drive torque to each of the rear left wheel 35 and the rear right wheel 36 in accordance with the vehicle state and the driver's operation state. is doing. The target rear right wheel driving torque to be distributed to the rear right wheel 36 may be obtained by PID control based on the deviation between the target yaw rate and the actual yaw rate detected by the yaw rate sensor (the following equation (4)), or It may be obtained according to the load distribution ratio (fixed value) (the following equation (5)), or may be obtained by a function F4 using the lateral acceleration as a variable based on the lateral acceleration detected by the lateral acceleration sensor (below) Formula (6)).
Target rear right wheel drive torque = total drive torque × PID (target yaw rate−actual yaw rate)
... (4)
Target rear right wheel drive torque = total drive torque × load distribution ratio (fixed value) (5)
Target rear right wheel driving torque = total driving torque × F5 (lateral acceleration) (6)

And the target rear left wheel drive torque distributed to the rear left wheel 35 is calculated | required by the following formula | equation using the target rear right wheel drive torque calculated | required using either of said Formula (4)-(6).
Target rear left wheel drive torque = total drive torque-target rear right wheel drive torque

  As will be described later, a corrected torque is obtained for the distributed target rear right wheel drive torque and the target rear left wheel drive torque, and this corrected torque is limited by the torque difference upper limit value. Therefore, differential limitation is performed.

The target rotational speed difference calculation means B25 calculates the target rotational speed difference according to the vehicle state and the driver's operation state. Specifically, based on the vehicle speed and the steering angle detected by the vehicle speed sensor and the steering angle sensor, the target rotational speed difference is obtained by a function F4 using the vehicle speed and the steering angle as variables, as shown in the following equations.
Target speed difference = F4 (vehicle speed, steering angle)
Note that the target rotational speed difference is 0 when the vehicle is running straight.

The actual rear right wheel rotational speed detection means B26 detects the actual rear right wheel rotational speed from the wheel speed sensor of the rear right wheel 36, and the actual rear left wheel rotational speed detection means B27 detects from the wheel speed sensor of the rear left wheel 35. The actual rear left wheel rotational speed is detected, and the computing unit C21 subtracts the detected actual rear left wheel rotational speed from the detected actual rear right wheel rotational speed, as shown in the following equation, to obtain the rear right wheel 36 and The difference between the actual left and right wheel rotational speeds, which is the rotational speed difference from the rear left wheel 35, is obtained.
Difference between actual left and right wheel rotational speed = actual rear right wheel rotational speed-actual rear left wheel rotational speed Also, the rear left wheel actual motor rotational speed and rear right wheel actual motor rotational speed detected by rear left wheel motor 37 and rear right wheel motor 38 Based on the following equation, the actual left and right wheel rotation speed difference may be obtained.
Difference between actual left and right wheel speeds = (rear right wheel actual motor speed-rear left wheel actual motor speed) x coefficient

The target rotational speed difference tracking control means B28 calculates a correction torque for controlling the actual left and right wheel rotational speed difference to follow the target rotational speed difference. Specifically, the target rotational speed difference obtained by the target rotational speed difference calculating means B25 and the actual right and left wheel rotational speeds obtained by the actual rear right wheel rotational speed detecting means B26, the actual rear left wheel rotational speed detecting means B27 and the calculator C21. Based on the deviation from the number difference, the correction torque is obtained by PID control as shown in the following equation.
Correction torque = PID (target speed difference-actual left and right wheel speed difference)
Note that the correction torque is not limited to PID control, and may be obtained by other control methods such as H∞ control, fuzzy control, and the like. However, in this embodiment, the gain is set high in order to increase the responsiveness no matter what control is used.

  The torque difference upper limit calculation means B29 calculates an upper limit value (torque difference upper limit value) for the correction torque calculated by the target rotational speed difference follow-up control means B28 based on the vehicle state and the driver's operation state. Specifically, the torque difference upper limit value is calculated using the maps shown in FIGS. 3 (a) and 3 (b). The map used in the present embodiment is strictly different from the map shown in FIGS. 3A and 3B, but has the same shape. Therefore, in this embodiment, as an example, The following description will be given with reference to FIGS.

  A map 1 (first map) shown in FIG. 3A is a map for calculating a maximum differential limiting torque that limits the maximum value of the correction torque based on the total driving torque that is a driver's acceleration request. The maximum differential limiting torque is increased in proportion to the increase in the total driving torque. As shown in a map 2 in FIG. 3B described later, when the absolute value of the steering angle is 0, the correction coefficient for the maximum differential limiting torque is 1. A map 1 shown in FIG. 3A is obtained when the absolute value of the steering angle is 0, and is a maximum value that limits the correction torque.

  In place of the total driving torque, the maximum differential limiting torque may be calculated based on the accelerator opening that is the driver's acceleration request, and the map in that case is also proportional to the increase in the accelerator opening. The maximum differential limiting torque is increased. The accelerator opening is detected using an accelerator opening sensor.

  A map 2 (second map) shown in FIG. 3B is a map for calculating a correction coefficient for correcting the maximum differential limiting torque calculated in the map 1 based on the steering angle detected by the steering angle sensor. The correction coefficient is decreased from 1 to 0 in inverse proportion to the increase in the absolute value of the steering angle. When the absolute value of the steering angle is larger than a predetermined value, the correction coefficient is set to 0.

Then, in the torque difference upper limit calculating means B29, as shown in the following equation, the torque difference upper limit value is obtained by adding the correction coefficient calculated in map 2 to the maximum differential limiting torque calculated in map 1. .
Torque difference upper limit = (maximum differential limiting torque of MAP1) × (correction coefficient of MAP2)

In the limiter B30, the absolute value of the correction torque input from the target rotational speed difference tracking control unit B28 is limited to be equal to or less than the torque difference upper limit value calculated by the torque difference upper limit value calculation unit B29. Specifically, a limiter output in which the upper limit of the absolute value of the correction torque is limited by the upper limit value of the torque difference is calculated using the following equation.
Limiter output = max {(−torque difference upper limit value), min (torque difference upper limit value, correction torque)}

  The computing unit C22 adds the coefficient A to the limiter output L limited by the limiter B30, and outputs a correction value [A × L]. The coefficient A is, for example, “0.5”, and the correction torque calculated by the target rotational speed difference follow-up control means B28 and the torque difference by this differential limiting control (specifically, an arithmetic unit to be described later) The difference between the post-restricted right wheel drive torque calculated in C23 and the post-restricted left wheel drive torque calculated in the calculator C24 is made equal.

  The calculator C23 adds the correction value [A × L] output from the calculator C22 to the target rear right wheel drive torque calculated by the torque distribution calculator B22, thereby obtaining the final rear right wheel drive torque. On the other hand, the calculator C24 outputs the correction value [A × L output from the calculator C22 from the target rear left wheel drive torque calculated by the torque distribution calculator B22. ] Is output as a final rear left wheel driving torque (restricted left wheel driving torque).

In the rear right wheel drive torque → rear right wheel motor torque conversion means B23, the restricted right wheel drive torque output from the calculator C23 is converted into the rear right wheel motor torque of the rear right wheel motor 38 using the following equation. It has been converted. The coefficient in this equation is in accordance with the reduction ratio of the rear right wheel 36, for example, coefficient = (1 / reduction ratio).
Rear right wheel motor torque = Right wheel drive torque after restriction x coefficient

Similarly, the rear left wheel drive torque → rear left wheel motor torque conversion means B31 converts the limited left wheel drive torque output from the calculator C24 into the rear left wheel motor torque of the rear left wheel motor 37 using the following equation. ing. The coefficient in this equation corresponds to the reduction ratio of the rear left wheel 35, for example, coefficient = (1 / reduction ratio).
Rear left wheel motor torque = Restricted left wheel drive torque x coefficient

  The rear right wheel motor control means B24 controls the rear right wheel motor 38 to output the rear right wheel motor torque. The rear left wheel motor control means B32 controls the rear left wheel motor torque to The rear left wheel motor 37 is controlled. In this way, by controlling the rear right wheel motor 38 and the rear left wheel motor 37, differential limitation is performed.

  Here, with reference to FIG. 3 to FIG. 5, an outline of a control procedure for differential limitation in the differential limitation control device 39 will be described.

  The target rear left wheel that calculates the total driving torque according to the driver's acceleration request (vehicle speed, accelerator opening) and distributes it to each of the rear left wheel 35 and the rear right wheel 36 according to the vehicle state and the driver's operation state. The driving torque and the target rear right wheel driving torque are obtained (refer to total driving torque calculating means B21 and torque distribution calculating means B22 in FIG. 5).

  The difference between the actual left and right wheel rotational speeds is calculated using the actual rotational speeds of the rear left wheel 35 and the rear right wheel 36 or the motor rotational speed of the rear left wheel motor 37 and the motor rotational speed of the rear right wheel motor 38 (rear right and left in FIG. 5). Wheel real rotation speed detection means B26, rear left wheel real rotation speed detection means B27, and calculator C21).

  Based on the vehicle state (vehicle speed) and the driver's operation state (steering angle), the target rotational speed difference is calculated (see target rotational speed difference calculating means B25 in FIG. 5).

  Using the deviation of the actual left and right wheel rotational speed difference with respect to the target rotational speed difference, a correction torque for controlling the actual left and right wheel rotational speed difference to follow the target rotational speed difference is calculated (target rotational speed difference tracking control means in FIG. 5). B28). For example, the correction torque may be obtained by PID control.

  Based on the driver's operation state (total driving torque (or accelerator opening), steering angle), a torque difference upper limit value for the correction torque is calculated (torque difference upper limit calculation means B29 in FIG. 5 and FIG. 3 (a)). (See maps 1 and 2 in (b)). At this time, the maximum differential limiting torque that limits the maximum value of the correction torque is calculated based on the total driving torque or the accelerator opening, and the correction coefficient that corrects the maximum differential limiting torque is calculated based on the steering angle. The torque difference upper limit value is obtained by adding the correction coefficient to the maximum differential limit torque.

  A limiter process is performed to limit the absolute value of the correction torque to a torque difference upper limit value or less (see limiter B30 in FIG. 5).

  The coefficient A is added to the limiter output L subjected to the limiter process to output a correction value [A × L], and the correction value [A × L] is added to the target rear right wheel drive torque calculated by the torque distribution calculation means B22. These are added and output as the final rear right wheel drive torque (restricted right wheel drive torque), and the correction value [A × L] is subtracted from the target rear left wheel drive torque calculated by the torque distribution calculation means B22. Thus, the final rear left wheel driving torque (restricted left wheel driving torque) is output (see computing units C22, C23, and C24 in FIG. 5).

  The restricted right wheel drive torque is converted into a rear right wheel motor torque output by the rear right wheel motor 38 (see rear right wheel front shaft drive torque → rear right wheel motor torque conversion means B23 in FIG. 5), and the restricted left wheel The drive torque is converted into rear left wheel motor torque output by the rear left wheel motor 37 (see rear left wheel drive torque → rear left wheel motor torque conversion means B31 in FIG. 5).

  The rear right wheel motor 38 and the rear left wheel motor 37 are controlled so as to output the converted rear right wheel motor torque and rear left wheel motor torque, respectively, and differential limitation is performed (rear right wheel motor control means B24 in FIG. 5). The rear left wheel motor control means B32).

  Even if high gain follow-up control is performed by the above-described control and the correction torque for the target rotational speed difference is calculated, the upper limit of the calculated correction torque is limited, and the motor torque based on the limited correction torque is used. Since the wheel motor 38 and the rear left wheel motor 37 are controlled, the response of the motor torque and the convergence to the target value are improved. As a result, an effect equivalent to the differential limiting control by the initial torque using the electronic control LSD can be obtained, and the stability and the traction performance can be improved. Further, when the target rotational speed difference is set to 0, the same effect as the electronic control LSD can be obtained, so that the straight running stability is improved.

  In the above-described control, the target rotational speed difference calculated from the vehicle speed and the steering angle is used, so that the differential limiting torque acts as much as the actual vehicle body posture deviates from the target vehicle body posture, smooth turning and excellent stability. Can be achieved.

  The present invention is suitable for limiting the differential between the front and rear shafts and between the left and right wheels in an electric vehicle.

11, 31 Front left wheel 12, 32 Front right wheel 13 Front shaft 14 Differential gear 15, 20, 33, 34, 37, 38 Electric motor 16, 35 Rear left wheel 17, 36 Rear right wheel 18 Rear shaft 19 Differential gear 21 39 Differential limiting control device

Claims (4)

As a power source for driving the first wheel, it has at least an electric motor,
As a power source for driving the second wheel, it has at least another electric motor,
A differential restriction control device that controls the electric motor and the other electric motor to perform differential restriction between the first wheel and the second wheel;
The differential limiting control device includes:
According to the driver's acceleration request, calculate the total driving torque of the vehicle,
According to the vehicle state and the operation state of the driver, the total drive torque is respectively distributed to the target first wheel drive torque to the first wheel and the target second wheel drive torque to the second wheel,
From the actual rotational speed of the first wheel and the actual rotational speed of the second wheel, the actual rotational speed difference between the first wheel and the second wheel is calculated,
Based on the vehicle speed and steering angle of the vehicle, a target rotational speed difference between the first wheel and the second wheel is calculated,
Calculating a correction torque for causing the actual rotational speed difference to follow the target rotational speed difference;
Based on the operation state of the driver, the maximum differential limit torque that limits the maximum value of the correction torque is calculated,
A limiter output obtained by limiting the upper limit of the absolute value of the correction torque with the maximum differential limiting torque is calculated,
The limiter output is added to one of the target first wheel drive torque and the target second wheel drive torque, and the limiter output is subtracted from the other to limit the first wheel drive torque and the limit second wheel drive. Calculate the torque,
The electric motor is controlled so as to be the limited first wheel driving torque, and the other electric motor is controlled so as to be the limited second wheel driving torque, thereby performing differential limitation. A differential limiting control device for an electric vehicle. As a power source for driving the front shaft, it has at least an electric motor,
As a power source for driving the rear shaft, it has at least another electric motor,
A differential limiting control device that controls the electric motor and the other electric motor to perform differential limiting between the front shaft and the rear shaft;
The differential limiting control device includes:
According to the driver's acceleration request, calculate the total driving torque of the vehicle,
According to a vehicle state and a driver's operation state, the total drive torque is distributed to the target front shaft drive torque to the front shaft and the target rear shaft drive torque to the rear shaft, respectively.
From the actual rotational speed of the front shaft and the actual rotational speed of the rear shaft, the actual rotational speed difference between the front and rear axes, which is the actual rotational speed difference between the front shaft and the rear shaft, is calculated.
Based on the vehicle speed and steering angle of the vehicle, a target rotational speed difference between the front shaft and the rear shaft is calculated,
Calculate a correction torque for causing the actual front-rear shaft rotational speed difference to follow the target rotational speed difference,
Based on the operation state of the driver, the maximum differential limit torque that limits the maximum value of the correction torque is calculated,
A limiter output obtained by limiting the upper limit of the absolute value of the correction torque with the maximum differential limiting torque is calculated,
Of the target front shaft drive torque and the target rear shaft drive torque, the limiter output is added to the shaft with the lower rotational speed, and the limiter output is subtracted from the shaft with the higher rotational speed, before the limit. Calculate shaft drive torque and post-restricted shaft drive torque,
The electric motor is controlled so as to be the pre-restricted shaft driving torque, and the other electric motor is controlled so as to be the post-restricted shaft driving torque to perform differential limitation. A differential limiting control device for an electric vehicle. As a power source for driving the right wheel, it has at least an electric motor,
As a power source for driving the left wheel, it has at least another electric motor,
A differential limiting control device that controls the electric motor and the other electric motor to perform differential limiting between the right wheel and the left wheel;
The differential limiting control device includes:
According to the driver's acceleration request, calculate the total driving torque of the vehicle,
According to the vehicle state and the driver's operation state, the total drive torque is respectively distributed to the target right wheel drive torque to the right wheel and the target left wheel drive torque to the left wheel,
From the actual rotational speed of the right wheel and the actual rotational speed of the left wheel, an actual left-right wheel rotational speed difference that is the actual rotational speed difference between the right wheel and the left wheel is calculated,
Based on the vehicle speed and steering angle of the vehicle, a target rotational speed difference between the right wheel and the left wheel is calculated,
Calculating a correction torque that causes the difference between the actual left and right wheel rotational speeds to follow the target rotational speed difference;
Based on the operation state of the driver, the maximum differential limit torque that limits the maximum value of the correction torque is calculated,
A limiter output obtained by limiting the upper limit of the absolute value of the correction torque with the maximum differential limiting torque is calculated,
The limiter output is added to the target right wheel drive torque to calculate a limited right wheel drive torque, and the limiter output is subtracted from the target left wheel drive torque to calculate a limit left wheel drive torque.
The electric motor is controlled so as to be the limited right wheel driving torque, and the other electric motor is controlled so as to be the limited left wheel driving torque to perform differential limitation. A differential limiting control device for a vehicle. In the differential limiting control device for an electric vehicle according to any one of claims 1 to 3,
The differential limiting control device includes:
The maximum differential limiting torque is calculated using a first map in which the maximum differential limiting torque increases according to an increase in the driver's acceleration request,
A correction coefficient for correcting the maximum differential limiting torque is calculated using a second map in which the correction coefficient decreases from 1 to 0 in accordance with an increase in the absolute value of the steering angle;
The maximum differential limit torque and the correction coefficient are integrated to calculate a torque difference upper limit value for limiting the correction torque,
The differential limit control device for an electric vehicle, wherein the limiter output is calculated by limiting an upper limit value of the absolute value of the correction torque with the upper limit value of the torque difference.

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