JP2006025485A - Brake drive force controller for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake drive force controller of a vehicle capable of preventing overslip in ABS operation at braking, and of exhibiting maximum brake characteristics. <P>SOLUTION: The brake drive force controller of a vehicle comprises motors 4 and 2, connected to the right and left front wheels 3 and 1 of the vehicle, respectively, a means 9 for braking the right and left front wheels 3 and 1 mechanically, and an ABS controller 7 for controlling mechanical brake force of the right and left front wheels 3 and 1, depending on the locking tendency thereof during braking, wherein the ABS controller 7 is provided with a means for controlling brake drive force of the motors 2 and 4, such that the wheel speed follows the vehicle speed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention belongs to the technical field of a vehicle braking / driving force control device that controls a mechanical braking force and a regenerative braking force during ABS operation.

In a conventional electric vehicle, when a tendency to lock is detected in each wheel during braking, the lock tendency is suppressed and the braking distance is shifted by shifting to an ABS operation period in which the mechanical braking force and the regenerative braking force are simultaneously reduced. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 10-297462

  However, in the above prior art, when the rotational speed of the motor is in a high constant power region, the maximum torque value of the motor decreases as the rotational speed increases. Therefore, regenerative braking or driving at high torque is performed in the high rotational region. However, regenerative braking and driving are performed at a low torque with a predetermined time constant. For this reason, a delay due to a predetermined time constant occurs with respect to the reduction of the total braking force, and there is a possibility that a so-called overslip in which the wheel temporarily stops is generated.

  The present invention has been made paying attention to the above-mentioned problem, and an object of the present invention is to provide a braking / driving force control device for a vehicle that can prevent overslip in the ABS operation during braking and that can exhibit the maximum braking characteristics. Is to provide.

In order to achieve the above object, the present invention provides:
An electric motor connected to each of the left and right drive wheels of the vehicle;
Mechanical braking means for mechanically braking the left and right drive wheels;
Mechanical braking force control means for controlling the mechanical braking force of the left and right drive wheels according to the locking tendency of the left and right drive wheels during braking;
In a braking / driving force control device for a vehicle having
An electric motor braking / driving force control means is provided for controlling the braking / driving force of the electric motor so that the wheel speed follows the vehicle body speed during the mechanical braking force control by the mechanical braking force control means.

  In the present invention, when the left and right drive wheels tend to be locked, the braking / driving force of the motor is controlled so that the wheel speed matches the vehicle body speed while controlling the mechanical braking force. In addition, the braking distance can be shortened.

  Hereinafter, the best mode for carrying out the present invention will be described based on Examples 1 and 2.

First, the configuration will be described.
FIG. 1 is an overall configuration diagram illustrating a braking / driving force control device for a vehicle according to a first embodiment.

  For example, electric motors 2 and 4 such as a three-phase AC motor are connected to the left and right front wheels 1 and 3 which are driving wheels and steering wheels of the vehicle. These electric motors 2 and 4 are driven by the electric power supplied from the power converter 5. The power converter 5 is connected to the DC power supply 10 via the DC voltage conversion means 11.

  Wheel speed sensors 6 for detecting wheel speeds are respectively attached to the left and right front wheels 1 and 3 and the left and right rear wheels 12 and 13, and outputs of the wheel speed sensors 6 are connected to an ABS controller 7. The output of the ABS controller 7 is connected to the ABS actuator 8 and the power converter 5.

  The left and right front wheels 1 and 3 and the left and right rear wheels 12 and 13 are respectively provided with mechanical braking means 9 for generating braking force on the wheels by brake hydraulic pressure. Each mechanical braking means 9 is supplied with the brake hydraulic pressure generated by the master cylinder 15 according to the operation amount of the brake pedal 14 and the brake hydraulic pressure generated by the ABS actuator 8.

  The ABS controller 7 is configured to control the braking / driving force (regenerative braking force and driving force) of the electric motors 2 and 4 and the hydraulic control by the ABS actuator 8 based on the pulse signal corresponding to the rotational speed of the wheel input from the wheel speed sensor 6. Coordinately control power (mechanical braking force). During normal braking, the motors 2 and 4 are mainly driven as generators, so that the braking torque is recovered in the DC power source 10 as electric energy.

  Here, if power is prevented from returning from the DC voltage conversion means 11 to the DC power supply 10, the input voltage of the power converter 5 becomes high. Alternatively, the input voltage of the power converter 5 may be increased by boosting the power from the DC power supply 10 by the DC voltage conversion unit 11 and supplying the boosted power to the power converter 5. The power converter 5 generates a high-voltage PWM and applies it to the electric motors 2 and 4.

  The ABS controller 7 calculates the estimated vehicle speed based on the detection signal of the wheel speed sensor 6 and the longitudinal acceleration of the vehicle, and based on the estimated vehicle speed and the detection signal of each wheel speed sensor 6, the difference between the actual wheel speed and the vehicle speed. Is calculated. Further, a target wheel speed body speed difference capable of realizing a slip ratio that can secure a grip force on the road surface of the wheel at the estimated body speed is calculated.

  The ABS controller 7 calculates a regenerative braking force and a hydraulic braking force from a preset control map based on the difference between the calculated target wheel speed body speed difference and the actual wheel speed body speed difference. 3 to control the total braking force.

  Further, the ABS controller 7 starts the ABS operation when the wheel speed falls below the target wheel speed, and controls the hydraulic braking force of the mechanical braking means 9 based on the control map (corresponding to the mechanical braking force control means). Then, the regenerative braking force (including negative regenerative braking force) of the electric motors 2 and 4 is controlled so that the wheel speed follows the target wheel speed (corresponding to electric motor braking / driving force control means). As described above, when the electric motors 2 and 4 are powered during the ABS operation, the power supply voltage supplied to the electric motors 2 and 4 is increased (corresponding to high voltage supply means).

Next, the operation will be described.
[Over slip during ABS operation]
Conventionally, as a vehicle braking force control device, techniques described in Japanese Patent Laid-Open Nos. 5-270387, 10-297462, and 3438243 are known. These prior arts include hydraulic braking means for generating a braking force by hydraulic pressure and regenerative braking means for generating a braking force by regenerative energy of the electric motor.

  In the braking force control device, the hydraulic braking force and the regenerative braking force with respect to the total braking force are controlled so as to be appropriately distributed. That is, the braking force is controlled by increasing or decreasing the hydraulic braking while the regenerative braking force is maintained constant, or the braking force is increased or decreased when the hydraulic braking force is maintained constant. The braking force is controlled by controlling or by increasing or decreasing both at the same time.

  The braking force control device is provided with an ABS controller that controls the hydraulic braking force and the regenerative braking force based on the wheel speed and the estimated vehicle body speed. The ABS controller calculates the estimated vehicle speed based on the detection signal of the wheel speed sensor and the longitudinal acceleration of the vehicle, and calculates the slip ratio for each tire from the estimated vehicle speed and the detection signal of each wheel speed sensor. Then, the hydraulic braking force and the regenerative braking force are controlled so that the slip ratio becomes a predetermined value.

  For this reason, in the above conventional example, the braking distance can be shortened by the hydraulic braking force and the regenerative braking force. Further, even when a steering input is made during the ABS operation, the vehicle can be steered by rotating the wheels.

  Here, when the vehicle is traveling on a road surface with a low friction coefficient (low μ road), the slip ratio is high even if the braking force is small compared to the high μ road, and the wheels are easily locked. If it is necessary to control the above and μ changes greatly, the braking force must be changed quickly.

[When increasing or decreasing only the hydraulic braking force]
During ABS operation, when the braking force is increased or decreased while maintaining the regenerative braking force to control the total braking force, the hydraulic braking force is reduced when a command to reduce the braking force is generated when the ABS operates. Since the rotational force of the wheel increases due to friction between the wheel and the road surface, the wheel speed after a certain time has returned to the vehicle body speed.

  In other words, because the wheel speed is passively recovered, if the road friction coefficient μ is small, even if the ABS operation is started and the braking force is reduced, sufficient rotational force does not work on the wheel, and the wheel is slipping. It is difficult to return immediately from the wheel, and there is a case where the wheel is temporarily stopped. In this case, the braking distance from when the brake is applied to when the brake is stopped is increased, or the steering amount of the steered wheels is decreased with respect to the steering input, thereby giving the driver a sense of incongruity.

  Further, when a steering input is made, the force acting in the lateral direction of the wheel is increased due to the rotation direction of the wheel being deviated from the traveling direction, so that the tire slip ratio is increased, and the braking force and the steering performance are further reduced.

[When only increasing or decreasing the regenerative braking force]
Also, when controlling the total braking force by increasing / decreasing the regenerative braking during the ABS operation as in the technique described in Japanese Patent Laid-Open No. 5-270387, the regenerative braking force is positively controlled by controlling it to the negative side. It is possible to rotate the wheel and to actively control the wheel speed.

  However, in order to reduce only the regenerative braking force while the hydraulic braking force is kept constant, it is necessary to perform negative regenerative braking (= power running) against the hydraulic braking force, and a large torque is applied to the motor. This is necessary and can only be handled by large motors. That is, in a small electric motor, since the negative regenerative braking torque is small, a predetermined time constant must be passed in order to reduce the total braking force, which causes the above-described overslip.

[When hydraulic brake force and regenerative braking force are increased or decreased simultaneously]
When the hydraulic braking force and the regenerative braking force are increased or decreased simultaneously as in the techniques described in Japanese Patent Application Laid-Open No. 10-297462 and Japanese Patent No. 3438243, the total braking force is reduced compared to the case where the hydraulic braking force is made constant. It becomes easy to do. Further, in the case of a general electric motor, a large torque can be generated in a low rotation range, so that negative regenerative braking (= power running) can be performed in a short time.

  However, as shown in FIG. 2, in the constant power region where the rotational speed of the motor is high, the torque decreases as the rotational speed increases. Therefore, regenerative braking and driving with high torque cannot be performed in the high rotational region, and the torque is low. Regenerative braking and driving are performed with a predetermined time constant. For this reason, in order to reduce the total braking force by the ABS operation when the electric motor rotates at a high speed, there is a delay due to a time constant, which causes overslip.

  FIG. 3 is a time chart showing the action at the time of ABS operation in the conventional device that simultaneously increases or decreases the mechanical braking force and the regenerative braking force. The wheel speed, the vehicle body speed, the hydraulic braking force, the regenerative braking force, and the total during braking are shown. It shows the correspondence with braking force. It is assumed that the electric motor is driven in a constant power region with a high rotational speed.

When the wheel speed at the time t ₁ is less than the target wheel speed, the ABS operation start, has been shifted to the period of the braking force reduction. At this time, the total braking force is reduced by simultaneously reducing the mechanical (hydraulic) braking force and the regenerative braking force. However, since the maximum torque value of the motor is small in the constant power region, the total braking force is reduced. For this purpose, there is a delay due to a predetermined time constant, and an overslip occurs.

[Braking / driving force control action]
On the other hand, in the first embodiment, the braking / driving force of the motors 2 and 4 is controlled so that the wheel speed follows the vehicle body speed during the period in which the hydraulic braking force of the mechanical braking means 9 is reduced during the ABS operation. The wheel speed can be prevented from decreasing due to the ABS operation, and overslip can be prevented.

  Further, in the first embodiment, during the ABS operation, in order to increase the power supply voltage supplied to the motors 2 and 4, regeneration is performed over the entire constant torque region and constant power region of the motor without increasing the size of the motor. It is possible to quickly switch between braking and avoid overslip caused by response delay.

  That is, when the input voltage of the power converter 5 is in a high voltage state, the rotation speed-torque curve of the motors 2 and 4 increases the maximum value in the constant power region as shown in FIG. Can perform regeneration and power running of large torque / power exceeding conventional limits. For this reason, it moves to the power running from the state of regenerative braking, and it becomes possible to generate a big torque in a short time. Therefore, a desired magnitude of powering can be performed quickly from the regenerative braking state.

FIG. 5 is a time chart showing the braking / driving force control operation of the first embodiment. When a braking operation is performed in FIG. 5, the ABS controller 7 supplies each braking force at time t ₀ when the braking state is reached. As a result, the wheel speed decreases, and when the wheel acceleration / deceleration falls below a predetermined wheel acceleration / deceleration, the holding period starts.

Subsequently, at a time point t ₁ when the wheel speed is lower than the target wheel speed, the process shifts to a braking force reduction period. In this braking force decrease period, but reduces the hydraulic braking monotonically, regenerative braking is performed drive from the control map to the negative side, the time t ₂ which is at the end of the braking force reduction period, returns to the regenerative braking again To the retention period.

When the wheel acceleration is the time t ₃ when exceeding a predetermined value, the process proceeds to light braking period, the regenerative braking force is increased retained or slowly, followed by time t ₄ after the wheel deceleration is below a predetermined value Then, it shifts to a holding period for holding a constant regenerative braking force. This is repeated and control is performed so that the slip ratio of each tire becomes the reference slip ratio.

  That is, according to the control of the regenerative braking force of the first embodiment, not only the regenerative braking force is monotonously decreased but also a driving force that stops the slip is generated. Here, the power running does not necessarily mean that the driving torque is transmitted to the axle, but means that electric power running power is applied to the motors 2 and 4 in order to quickly reduce the braking force (regenerative force).

Further, as shown in time point t ₁₁ ~ time t ₁₂ of FIG. 3, even though the braking force is reduced, when a slip occurs, shown at time t ₁₁ ~ time t ₁₂ of FIG. 5 Thus, by giving power running electric power to the electric motors 2 and 4, it appears as a driving force with respect to an axle, and an overslip can be prevented.

  Further, in the first embodiment, highly responsive control is realized by varying the regenerative braking force of the electric motors 2 and 4 to cause the wheel speed to follow the vehicle body speed. By the way, when control is performed to vary the mechanical braking force (brake hydraulic pressure) and the wheel speed to follow the vehicle body speed, the current value of the motors 2 and 4 is changed, but the response delay is large. The following performance cannot be obtained and the braking distance becomes long. This is also clear from the fact that the initial reduction amount of the mechanical braking force is set by feedforward control considering responsiveness during normal ABS operation.

Next, the effect will be described.
In the braking / driving force control device for a vehicle according to the first embodiment, the following effects can be obtained.

  (1) The motor braking / driving force control means controls the braking / driving force of the motors 2 and 4 to adjust the wheel speed to the vehicle body speed during the period in which the mechanical braking force is reduced by the ABS operation, so that overslip is avoided. The braking distance can be shortened and the steering performance can be improved. Further, by powering the electric motor during the period when the mechanical braking force is reduced, the wheel speed can be effectively adjusted to the vehicle body speed in a short time.

  (2) When the motors 2 and 4 are driven by the motor braking / driving force control means, a high voltage supply means for increasing the power supply voltage supplied to the motors 2 and 4 is provided, so that the limit value is exceeded in the constant power region. Torque and large electric power can be generated, and regeneration and driving can be switched instantaneously with a small electric motor over the entire region, so that overslip caused by a response delay of the electric motors 2 and 4 can be prevented.

  Example 2 is an example of driving an electric motor connected to driving wheels on the outer side of a turn when a steering input is applied during an ABS operation.

  FIG. 6 is an overall configuration diagram illustrating a vehicle braking / driving force control apparatus according to the second embodiment. Compared to FIG. 1, a steering angle sensor 16 that detects a steering angle and a yaw rate sensor (yaw rate) that detects an actual yaw rate of the vehicle. This is different from the first embodiment in that a detection means) 17 is provided.

  In the ABS controller 7 of the second embodiment, when the wheel speed falls below the target wheel speed, the ABS operation is started as in the first embodiment, and the difference between the target wheel speed vehicle speed difference and the actual wheel speed vehicle speed difference is determined. Based on the control map, the regenerative braking force applied to the electric motor inside the turn is calculated.

  Further, in the second embodiment, when a steering input is applied during the ABS operation, the actual yaw rate of the vehicle detected by the yaw rate sensor 17, the steering steering angle detected by the steering angle sensor 16, and the vehicle body speed are obtained. (Equivalent to target yaw rate calculation means) The driving force applied to the motor outside the turn is calculated so as to eliminate the difference from the target yaw rate.

Next, the operation will be described.
[Braking / driving force control action]
In the second embodiment, during the ABS operation, the motor on the outer side of the turn is driven according to the deviation between the target yaw rate and the actual yaw rate, so that the wheel speed of the outer turning wheel becomes faster than the wheel speed of the inner turning wheel. Therefore, the turning performance according to the target yaw rate can be ensured while preventing the tire from slipping.

  Incidentally, as a control similar to the second embodiment for compensating for the steering of the vehicle, the vehicle stability that increases the stability of the vehicle by driving the driving wheels on the outer side during turning and controlling the driving wheels on the inner side during turning. Control is known. However, this vehicle stability control is a control that suppresses the side slip of the vehicle that occurs when entering a low μ road curve, and cannot compensate for steering during control, particularly during ABS operation.

[Braking / driving force control action]
FIG. 7 is a time chart showing the braking / driving force control action of the second embodiment. When the steering operation is performed together with the braking operation, each braking force is supplied at the time point t ₀ when the braking state is reached, and the wheel is accordingly moved. Speed decreases.

When the wheel speed falls below the target wheel speed at the time t _1, to shift to the period of the braking force reduction. In this braking force decrease period, the mechanical braking force is monotonously reduced, but the regenerative braking is performed with the braking force control calculated from the control map.

  Subsequently, as in the first embodiment, the regenerative braking force applied to the turning inner wheel is calculated from the control map based on the difference between the target wheel speed vehicle speed difference and the actual wheel speed vehicle speed difference. When a steering input is applied, the yaw rate signal from the yaw rate sensor 17 is input to the ABS controller 7, and the difference from the target yaw rate calculated from the steering angle is calculated. Based on this difference, the driving force applied to the turning outer wheel is calculated from the control map.

Applying a longitudinal force that is the calculation of the left and right to the drive wheels 1,3, the time t ₂ which is at the end of the braking force reduction period, returns to the regenerative braking again, the process proceeds to the holding period. Since the subsequent steps are the same as those in the first embodiment, description thereof is omitted.

  In the second embodiment, as shown in FIG. 7, the regenerative braking force of the motor outside the turning is given a driving force for assisting the steering operation. Therefore, the turning outer wheel uses the power running power as the driving force. Appears.

Next, the effect will be described.
In the vehicle braking / driving force control apparatus according to the second embodiment, the following effects can be obtained in addition to the effects (1) and (2) of the first embodiment.

  (3) When the ABS operates and a steering input is applied, the motor braking / driving force control means drives the motor on the outer side during the period in which the braking force is reduced by the ABS operation. Can be made faster than the wheel speed on the inner side of the turn, so that a high turn responsiveness can be secured while suppressing the locking tendency.

  (4) Since the electric motor braking / driving force control means drives the electric motor outside the turn so as to eliminate the deviation between the target yaw rate and the actual yaw rate, an optimal vehicle behavior corresponding to the target yaw rate can be obtained.

(Other examples)
As mentioned above, although the braking / driving force control device for a vehicle according to the present invention has been described based on the first and second embodiments, the specific configuration is not limited to each embodiment. In the above example, the front wheel serves as both a drive wheel and a steered wheel. However, as long as it conforms to the gist of the present application, all the wheels may be drive wheels, or the drive wheels may be non-steer wheels. There may be.

  In the second embodiment, an example is shown in which a yaw rate sensor is provided as a yaw rate detection means for detecting the actual yaw rate of the vehicle. However, the yaw rate at the center of gravity of the vehicle is estimated from the driving force difference (torque difference) between the left and right motors and the slip ratio. May be. Moreover, it is good also as a structure which estimates a steering steering angle from the rotation speed difference and slip ratio of a left-right motor, without providing a steering angle sensor.

1 is an overall configuration diagram illustrating a vehicle braking / driving force control device according to a first embodiment; It is explanatory drawing which shows the problem of a prior art example. It is a time chart which shows the effect | action of a conventional apparatus. It is explanatory drawing which shows the motor torque increase effect | action in the constant electric power area | region of Example 1. FIG. 3 is a time chart showing the braking / driving force control operation of the first embodiment. 1 is an overall configuration diagram illustrating a vehicle braking / driving force control device according to a first embodiment; 6 is a time chart showing the braking / driving force control operation of the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Left front wheel 2 Electric motor 3 Right front wheel 4 Electric motor 5 Power converter 6 Wheel speed sensor 7 ABS controller 8 ABS actuator 9 Mechanical braking means 10 DC power supply 11 DC voltage conversion means 12 Left rear wheel 13 Right rear wheel 14 Brake pedal 15 Master cylinder

Claims (4)

An electric motor connected to each of the left and right drive wheels of the vehicle;
Mechanical braking means for mechanically braking the left and right drive wheels;
Mechanical braking force control means for controlling the mechanical braking force of the left and right drive wheels according to the locking tendency of the left and right drive wheels during braking;
In a braking / driving force control device for a vehicle having
The vehicle braking / driving force control means is provided for controlling the braking / driving force of the electric motor so that the wheel speed follows the vehicle body speed during the mechanical braking force control by the mechanical braking force control means. Driving force control device. The vehicle braking / driving force control device according to claim 1,
The vehicle braking / driving force control means drives a motor connected to driving wheels on the outer side of the turn, and the braking / driving force control device for a vehicle. The vehicle braking / driving force control device according to claim 2,
Target yaw rate calculating means for calculating the target yaw rate of the vehicle from the steering angle,
Yaw rate detection means for detecting the actual yaw rate of the vehicle;
Provided,
The vehicle braking / driving force control device drives a motor connected to driving wheels on the outer side of the turn based on a deviation between the target yaw rate and the actual yaw rate. The braking / driving force control device for a vehicle according to any one of claims 1 to 3,
A vehicle braking / driving force control device comprising high voltage supply means for increasing a power supply voltage supplied to the motor when the motor is driven by the motor braking / driving force control means.

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