JP6788424B2 - Vehicle braking force control device - Google Patents

Description

The present invention relates to a vehicle braking force control device capable of regenerative braking and hydraulic braking and having an antilock brake control (Antilock Brake System: hereinafter abbreviated as ABS) function for preventing a locked state of wheels.

Conventionally, ABS that prevents a locked state of wheels has been adopted in many vehicles, and has also been adopted in electric vehicles and hybrid vehicles capable of regenerative braking and hydraulic braking. At this time, the regenerative brake is superior in control response to the hydraulic brake, but has a different characteristic that the regenerative braking force changes depending on the situation and is unstable. Therefore, for example, Japanese Patent Application Laid-Open No. 2015-196474 In Japanese Patent Application Laid-Open No. 1 (hereinafter referred to as Patent Document 1), in ABS, when the locking tendency is eliminated and the total braking force is restored, the regenerative brake is increased prior to the hydraulic brake, and the regenerative brake precedes the hydraulic brake. The technology of the braking force control device for a vehicle is disclosed in which the hydraulic brake is increased while the regenerative brake is reduced and at least a part of the regenerative brake is replaced with the hydraulic brake.

JP 2015-196474

By the way, ABS requires accurate control of braking force (reduction, holding, increase, etc.) in a short period of time, and if the regenerative brake and hydraulic brake are simply controlled, their responsiveness and stability There is a problem that deceleration is lost due to the difference between the two, and conversely, the braking force becomes unstable. Therefore, when controlling with brakes having different characteristics such as a regenerative brake and a hydraulic brake, it is necessary to adopt the ABS technology disclosed in the above-mentioned Patent Document 1, and there is a problem that the control becomes complicated. ..

The present invention has been made in view of the above circumstances, and even in a vehicle capable of regenerative braking and hydraulic braking, deceleration may occur or the braking force may become unstable with simple control of ABS. It is an object of the present invention to provide a vehicle braking force control device that can be performed accurately without becoming a vehicle.

One aspect of the vehicle braking force control device of the present invention is a vehicle braking force control device capable of braking by a regenerative brake of an electric motor and braking by a hydraulic brake, in which the braking force during braking is controlled to control the wheel. Anti-lock brake control operation prediction that detects the front road surface condition and the anti-lock brake control means that prevents the locked state, and predicts the operation of the anti-lock brake control means based on the front road surface condition and the running state of the vehicle. means and, when said antilock brake control means is predicted, and a control means for a changeover regenerative brake hydraulic brake prior to operation of the antilock brake control means, said anti-lock brake control operation predicting means Predicts the operation of the anti-lock brake control means at a position where the road surface friction coefficient in front changes in the direction of decreasing.

According to the vehicle braking force control device according to the present invention, even if the vehicle is capable of regenerative braking and hydraulic braking, deceleration may occur or the braking force may become unstable with simple control of ABS. It is possible to carry out with high accuracy without becoming.

It is a schematic block diagram of the regenerative brake system and the hydraulic brake system of the vehicle which concerns on one Embodiment of this invention. It is a flowchart of the braking force control program which concerns on one Embodiment of this invention. It is a detection explanatory view of the front road surface state change which concerns on one Embodiment of this invention. It is a characteristic explanatory diagram of the ABS intervention determination threshold value which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 indicates a vehicle, and the left front wheel 2fl, the right front wheel 2fr, the left rear wheel 2rl, and the right rear wheel 2rr of the vehicle 1 are supported by the vehicle body via suspensions (not shown).

Inside the left front wheel 2fl, right front wheel 2fr, left rear wheel 2rl, right rear wheel 2rr, left front wheel in-wheel motor 3fl, right front wheel in-wheel motor 3fr, left rear wheel in-wheel motor 3rl, right rear wheel in-wheel A motor 3rr is incorporated in each wheel so that power can be transmitted freely.

In the present embodiment, the torques of the in-wheel motors 3fl, 3fr, 3rl, and 3rr are independently controlled to generate the driving force and the driving force to be described later for each wheel 2fl, 2fr, 2rl, and 2rr. , The regenerative braking force (regenerative braking) is independently and freely controllable.

Each in-wheel motor 3fl, 3fr, 3rl, and 3rr is connected to an inverter 4 provided corresponding to each motor, converts DC power supplied from the battery 5 into AC power, and converts the DC power into AC power. Is independently supplied to each in-wheel motor 3fl, 3fr, 3rl, and 3rr. As a result, the in-wheel motors 3fl, 3fr, 3rl, and 3rr are driven and controlled to apply driving force to each wheel 2fl, 2fr, 2rl, and 2rr.

In addition, each in-wheel motor 3fl, 3fr, 3rl, 3rr also functions as a generator, generates electricity by the rotational energy of each wheel 2fl, 2fr, 2rl, and 2rr, and regenerates the generated power to the battery 5 via the inverter 4. The regenerative energy generated by the power generation of each of the in-wheel motors 3fl, 3fr, 3rl, and 3rr applies regenerative braking force (regenerative braking) to each wheel 2fl, 2fr, 2rl, and 2rr. Give.

On the other hand, each wheel 2fl, 2fr, 2rl, and 2rr is provided with friction brake mechanisms 6fl, 6fr, 6rl, and 6rr, respectively, and these friction brake mechanisms 6fl, 6fr, 6rl, and 6rr are, for example, disc brakes. It is a known braking device such as a drum brake.

These friction brake mechanisms 6fl, 6fr, 6rl, and 6rr are connected to the brake drive unit 7, and the piston of the wheel cylinder is operated by the hydraulic pressure supplied from the brake drive unit 7, and each wheel 2fl, 2fr, 2rl, A braking force (hydraulic brake) is applied to 2rr.

The brake drive unit 7 is a hydraulic pressure generator composed of a booster pump, an accumulator, etc., a pressure adjustment control valve that adjusts the pressure of the brake hydraulic oil and supplies it to the wheel cylinders of the friction brake mechanisms 6fl, 6fr, 6rl, and 6rr, and a friction brake. It is a hydraulic unit including an on-off control valve for opening and closing a hydraulic circuit that supplies brake hydraulic oil to the mechanisms 6fl, 6fr, 6rl, and 6rr.

The above-mentioned inverter 4 and the brake drive unit 7 are connected to the control unit 10, respectively.

The control unit 10 is composed of a microcomputer composed of a CPU, ROM, RAM, etc., and executes various programs to execute various in-wheel motors 3fl, 3fr, 3rl, 3rr, and friction braking mechanisms 6fl, 6fr, 6rl, 6rr. Control the operation independently. Therefore, the control unit 10 includes an accelerator sensor 11 that detects the driver's accelerator operation amount, a brake sensor 12 that detects the driver's brake operation amount, and wheel speeds ωfl, ωfr, and ωrl of each wheel 2fl, 2fr, 2rl, and 2rr. , The wheel speed sensors 13fl, 13fr, 13rl, 13rr that detect ωrr, the road surface condition detection device 14 that detects the road surface condition in front, and the front-rear acceleration sensor 15 that detects the front-rear acceleration Gx are connected. Further, the control unit 10 controls each in-wheel motor 3fl, 3fr, 3rl, 3rr, such as a signal representing a current value flowing from the inverter 4 to each in-wheel motor 3fl, 3fr, 3rl, 3rr, a signal representing a voltage value, and the like. The sensor signal required for the above is input from the inverter 4.

Here, the road surface condition detection device 14 described above is based on image information in front of the traveling path taken by a camera, for example, as disclosed in JP-A-2002-127882 and JP-A-2004-168286. , The road surface condition in a predetermined region (asphalt dry road surface, asphalt wet road surface, snowy road, etc.) is detected, and these road surface conditions are replaced with preset road surface friction coefficients for detection. For example, as shown in FIG. 3, based on the image information from the camera, A1, A2, A3, A4, A5, ..., An-2, An-1, An. It is divided into regions, and the road surface friction coefficients μ1, μ2, μ3, μ4, μ5, ..., Μn-2, μn-1, μn, which are set in advance, are associated with the determined road surface conditions of these regions. The road surface condition ahead is detected.

Then, based on each of the above signals, the control unit 10 has a required driving force (target driving force) according to the accelerator operation amount of the driver and a required braking force (target braking force) according to the brake operation amount of the driver, that is. , The required driving force required to drive or brake the vehicle 1 is calculated in a predetermined manner with reference to a preset map, table, etc., and each wheel 2fl, 2fr, 2rl, 2rr. It is distributed to each wheel required driving force generated by each in-wheel motor 3fl, 3fr, 3rl, 3rr. If the value of the required driving force is positive, it means that the driving force is required, and if the value of the required driving force is negative, it means that the braking force is required.

The control unit 10 generates a control signal (for example, a PWM control signal) so that a current corresponding to the required driving force of each wheel 2fl, 2fr, 2rl, and 2rr flows to each in-wheel motor 3fl, 3fr, 3rl, and 3rr. And output to the inverter 4. When the required driving force of each wheel 2fl, 2fr, 2rl, and 2rr is negative, the control unit 10 sets the required driving force of each wheel 2fl, 2fr, 2rl, and 2rr in advance by experiments, calculations, and the like. According to the set ratio, the regenerative brake generated by each in-wheel motor 3fl, 3fr, 3rl, 3rr and the hydraulic brake generated by the friction brake mechanism 6fl, 6fr, 6rl, 6rr are distributed. At this time, the control unit 10 outputs a control signal for generating the regenerative brake to the inverter 4 and outputs a control signal for generating the hydraulic brake to the brake drive unit 7. As a result, the target regenerative brake is generated at each in-wheel motor 3fl, 3fr, 3rl, and 3rr, and the target hydraulic brake is generated at the friction brake mechanisms 6fl, 6fr, 6rl, and 6rr.

Further, the control unit 10 has an ABS function of controlling the braking force during braking to prevent the wheel from being locked, detects the front road surface condition as described above, and detects the front road surface condition and the vehicle traveling. The operation of ABS is predicted based on the state, and when the operation of ABS is predicted , a signal is output to the inverter 4 and the brake drive unit 7 before the vehicle reaches the position where the operation of ABS is predicted, and regeneration is performed. ABS is executed after replacing the brake with a hydraulic brake. Specifically, in the ABS of the present embodiment, for example, when a preset wheel deceleration is reached, the increase in the brake fluid pressure is suppressed, the brake fluid pressure is maintained, and then the tire When the slip ratio of the wheel exceeds a preset value, the brake fluid pressure is reduced, and thereafter, the brake fluid pressure is maintained, the brake fluid pressure is increased, and so on. As described above, the control unit 10 has functions as an anti-lock brake control means, an anti-lock brake control operation prediction means, and a control means.

Next, the braking force control of the present embodiment executed by the control unit 10 will be described with reference to the flowchart of FIG.

First, in step 101 (hereinafter, abbreviated as "S") 101, it is determined whether or not the own vehicle 1 is braking. If the vehicle 1 is not braking, the program is exited, and if the vehicle is braking, the process proceeds to S102.

In S102, it is determined whether or not the executed braking includes the regenerative brake (whether or not the braking is performed by the regenerative brake and the hydraulic brake), and when the regenerative brake is not included, that is, when only the hydraulic brake is used. The brake control is continued as it is by jumping to S112, and the ABS is operated as needed.

As described above, in the ABS of the present embodiment, for example, when the preset wheel deceleration is reached, the increase in the brake fluid pressure is suppressed, the brake fluid pressure is held, and then the brake fluid pressure is maintained. When the slip ratio of the tire exceeds a preset value, the brake fluid pressure is reduced, and thereafter, the brake fluid pressure is maintained, the brake fluid pressure is increased, and so on.

Further, when it is determined in S102 that the regenerative brake is included (braking by the regenerative brake and the hydraulic brake), the process proceeds to S103 and a change in the road surface condition is detected. Specifically, as shown in FIG. 3, the road surface friction coefficients μ1, μ2, μ3, μ4, μ5, ..., Μn-2, μn detected for each region in front of the traveling path detected by the road surface condition detection device 14. For -1, μn, the road surface friction coefficient is calculated by obtaining the difference from (the road surface friction coefficient in the area closer to the own vehicle) to (the road surface friction coefficient in the area farther from the own vehicle) in the regions adjacent to the front and rear. The amounts of change Δμ1, Δμ2, Δμ3, Δμ4, Δμ5, ..., Δμn-3, Δμn-2, Δμn-1 are calculated. That is, if the amount of change in the road surface friction coefficient is a positive value, it is a region where traveling on a road surface having a low road surface friction coefficient is predicted .

Next, the process proceeds to S104, and the amount of change in the road surface friction coefficient detected in S103 exceeds the threshold value (positive value) set in advance by experiments, calculations, etc., and the road surface friction coefficient starts from a high value in front of the traveling road. It is determined whether or not there is a portion that greatly fluctuates to a low value (for example, a portion that fluctuates from an asphalt dry road surface to a snowy road).

As a result of the determination in S104, when it is determined that there is no region in which the amount of change in the road surface friction coefficient exceeds the threshold value (positive value) set in advance by experiments, calculations, etc., the current traveling state (deceleration state) is used. Since it can be determined that the ABS will not operate due to a sudden change in the road surface condition (for example, high μ road → low μ road), jump to S112 and continue the braking control as it is, and the ABS operates as necessary. Will be done.

On the contrary, when it is determined as a result of the determination in S104 that there is a region in which the amount of change in the road surface friction coefficient exceeds the threshold value (positive value) set in advance by experiments, calculations, etc., the process proceeds to S105, which will be described later. The ABS intervention judgment threshold DABS is set. If it is determined that there are a plurality of regions in which the amount of change in the road surface friction coefficient exceeds the threshold value (positive value) set in advance by experiments, calculations, etc., the nearest region is the subsequent S105 to S111. It becomes the target area for processing.

The ABS intervention determination threshold value DABS is set in advance by experiments, calculations, etc. For example, as shown in the characteristic diagram of FIG. 4, the ABS that keeps the wheel slip ratio during braking within a predetermined range is used. It is set in response to the deceleration that operates, and is set to a lower value as the road surface friction coefficient in the far side region of the region adjacent to the front and rear is lower.

Next, the process proceeds to S106, and the front-rear acceleration Gx of the own vehicle and the ABS intervention determination threshold value DABS are compared.

As a result of this comparison of S106, in the case of Gx <DABBS, it can be determined that the ABS does not operate due to a sudden change in the road surface condition (for example, high μ road → low μ road) in the current running state (deceleration state). Therefore, the brake control is continued as it is by jumping to S112, and the ABS is operated as needed.

Further, in the case of Gx ≧ D ABS, it is predicted that the ABS will operate when the road surface condition change position (sudden change position) is reached in the current running state (deceleration state), so the process proceeds to S107 to the road surface condition change position. The distance Lμ is detected.

Next, the process proceeds to S108, and the time tμ to the road surface state change position is calculated, for example, by the relationship of the following equation (1).

Lμ = V0 ・ tμ + (1/2) ・ Gx ・ tμ ² … (1)
Here, V0 is the current vehicle speed calculated from the wheel speed sensors 13fl, 13fr, 13rl, and 13rr, and the sign of the front-rear acceleration Gx is negative because it is in the deceleration state.

Next, the process proceeds to S109, and the time tst for replacing the regenerative brake with the hydraulic brake by subtracting the margin time Δt set in advance by experiments, calculations, etc. from the time tμ calculated in S108 to the road surface state change position. Is calculated (tst = tμ−Δt).

Next, the process proceeds to S110 and waits until the time tst for replacing the regenerative brake with the hydraulic brake elapses. When the time tst elapses, the process proceeds to S111, the regenerative brake is replaced with the hydraulic brake, and the braking control is continued. However, when the ABS is activated, the ABS is braked only by the hydraulic brake.

As described above, according to the embodiment of the present invention, it has the function of ABS that controls the braking force during braking to prevent the wheel from being locked, detects the front road surface condition, and determines the front road surface condition. predicting the operation of the ABS based on the running state of the vehicle, if the operation of the ABS is expected, before reaching the position where the vehicle is operated in the ABS is predicted, it outputs a signal to the inverter 4 and the brake driving unit 7 Then, ABS is executed after replacing the regenerative brake with the hydraulic brake. Therefore, even in a vehicle capable of regenerative braking and hydraulic braking, ABS is prevented from operating when brakes having different characteristics such as regenerative braking and hydraulic braking are operating. It is possible to accurately perform ABS without deceleration omission or unstable braking force by simple control without using particularly complicated control.

In the present embodiment, an electric vehicle having in-wheel motors on each of the four wheels has been described as an example, but a vehicle traveling with one motor, a vehicle traveling with two motors, and an electric vehicle traveling with three motors. Needless to say, it can also be applied to hybrid vehicles.

1 Vehicle 2fl, 2fr, 2rl, 2rr Wheels 3fl, 3fr, 3rl, 3rr In-wheel motor 4 Inverter 5 Battery 6fl, 6fr, 6rl, 6rr Friction brake mechanism 7 Brake drive unit 10 Control unit (anti-lock brake control means, anti-lock) Brake control operation prediction means, control means)
11 Accelerator sensor 12 Brake sensor 13fl, 13fr, 13rl, 13rr Wheel speed sensor 14 Road surface condition detector 15 Front-rear acceleration sensor

Claims (2)

In a vehicle braking force control device that can freely brake by regenerative braking of an electric motor and braking by hydraulic braking.
Anti-lock braking control means that controls the braking force during braking to prevent the wheels from locking.
An anti-lock brake control operation predicting means that detects the road surface condition in front and predicts the operation of the anti-lock brake control means based on the road surface condition in front and the running state of the vehicle.
When the operation of the anti-lock brake control means is predicted , the control means for replacing the regenerative brake with the hydraulic brake before the operation of the anti-lock brake control means, and
Equipped with a,
The anti-lock brake control operation predicting means is a vehicle braking force control device for predicting the operation of the anti-lock brake control means at a position where the front road surface friction coefficient decreases . Wherein if the operation of the antilock brake control means is predicted, that a changeover the regenerative brake before the vehicle reaches the position operation is predicted in the antilock brake control means hydraulic brake braking force control apparatus for a vehicle according to claim 1 Symbol mounting features.

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