JP2023134167A - Brake force estimation device and brake force estimation method - Google Patents

Abstract

To provide a brake force estimation device and a brake force estimation method capable of improving accuracy of brake force of a friction brake device and controlling a friction brake and a regenerative brake for optimizing the use of the regenerative brake in a manner that optimizes a ratio of the friction brake force to the regenerative brake force and thereby improving electricity consumption.SOLUTION: A brake force estimation device is for a vehicle comprising a steering actuator steering a steering wheel. The brake force estimation device has brake force estimation means which estimates brake force generated while braking on the basis of steering reaction force on the steering actuator and a distance between the steering wheel and a rotation shaft center of the steering actuator.SELECTED DRAWING: Figure 3

Description

The present invention relates to a braking force estimating device and a braking force estimating method for estimating the braking force generated in the tires of a vehicle during braking, and in particular, by estimating the braking force with high accuracy, the ratio between friction braking and regenerative braking is improved. The present invention relates to a brake force estimating device and a brake force estimating method that can optimize the amount of power generated by regenerative braking and maximize the amount of power generated by regenerative braking.

2. Description of the Related Art Conventionally, vehicles are known that are equipped with a road surface condition estimating device for performing steering control or braking control of each wheel based on the degree of grip of each wheel of the vehicle. Various structures of such road surface condition estimating devices are known, but for example, as shown in Patent Document 1, steering control is performed for each wheel by a drive means that is mechanically separated from the driver's operation means. A road surface condition estimation device installed in a vehicle to estimate a road surface condition while the vehicle is running, comprising: a road surface reaction torque detection means for detecting a road surface reaction torque when steering at least one wheel of the vehicle; self-aligning torque estimating means for estimating self-aligning torque generated in the wheel based on the detection result of the reaction torque detecting means; and at least one wheel index from among wheel indexes including a side force on the wheel and a wheel slip angle. The characteristics of the self-aligning torque estimated by the wheel index acquisition means to be estimated or detected and the self-aligning torque estimation means for the wheel index acquired by the wheel index acquisition means at least pass through the origin and have a slope at the origin. a reference self-aligning torque setting means for setting a reference self-aligning torque based on a reference self-aligning torque characteristic that approximates the linearity and identifies a slope while the vehicle is running; A road surface condition estimating device is known that includes a grip degree estimating means for estimating the degree of grip on a wheel based on a comparison result between a set reference self-aligning torque and a self-aligning torque estimated by the self-aligning torque estimating means. There is.

According to such a road surface condition estimating device, even when used in a vehicle with a steer-by-wire system that performs steering control for each wheel, it is possible to accurately estimate the road surface condition while the vehicle is running as the degree of grip or coefficient of friction. , can be estimated at appropriate timing. In particular, by providing a reference self-aligning torque setting means, when determining the change in the self-aligning torque described above, the self-aligning torque estimated by the self-aligning torque estimating means and the self-aligning torque that at least passes through the origin and The degree of grip is easily determined by approximating a linear shape having a slope at the origin, and based on a comparison result with a standard self-aligning torque set based on a standard self-aligning torque characteristic that identifies the slope while the vehicle is running. Moreover, it can be estimated with high accuracy.

Patent No. 3964771

However, conventional road surface condition estimating devices include a plurality of means, including a road surface reaction torque detecting means, a self-aligning torque estimating means, a wheel index obtaining means, a reference self-aligning torque setting means, and a grip degree estimating means. , there was a problem that the configuration became complicated.

Furthermore, in electric vehicles (EVs) and hybrid vehicles that use an electric motor or the like as driving force, the vehicle is braked by a combination of two braking forces: a regenerative braking device and a friction braking device. Here, a friction brake device is a brake device that performs braking by utilizing the frictional resistance between objects generated by pressing brake pads or brake shoes against a wheel, and a regenerative brake device usually converts power input. The electric motor, which outputs drive rotational force, conversely inputs the shaft rotation of the wheels to operate as a generator, converting kinetic energy into electrical energy and recovering or consuming it for use as a brake. It is a brake device.

In a braking device that is a combination of a regenerative braking device and a friction braking device, if the accuracy of the friction braking force of the friction braking device deteriorates, it is necessary to set the ratio of frictional braking force to a higher level in order to ensure reliable braking force. There is a need to. In this way, when the proportion of the friction brake device is increased, the proportion of the regenerative brake device is decreased, and thus the amount of power generation obtained by the regenerative brake device is reduced. Therefore, in order to increase the amount of power generated by the regenerative braking device, there is a need to improve the accuracy of the friction braking force.

However, the friction braking force of a friction brake device fluctuates widely depending on road conditions, the condition of brake pads and brake shoes, etc., and it is difficult to control this accurately, and the braking performance of the brake device has a large effect on vehicle safety. Considering related points, there was a problem in that the proportion of the friction brake device was set to be high.

The present invention has been made to solve the above problems, and by improving the accuracy of the braking force of a friction brake device, the ratio of friction braking force and regenerative braking force is optimized to maximize regenerative braking. It is an object of the present invention to provide a brake force estimating device and a brake force estimating method that can improve the electricity consumption of a vehicle by controlling the brake force so that it can be used for a limited time.

A brake force estimating device according to the present invention that solves the above problems is a brake force estimating device for a vehicle equipped with a steer actuator that steers steered wheels, and the brake force estimating device is a brake force estimating device for a vehicle equipped with a steer actuator that steers a steered wheel. The present invention is characterized by comprising a brake force estimating means for estimating the steering reaction force and the distance between the steered wheel and the rotation axis of the steer actuator.

Further, a brake force estimation method according to the present invention that solves the above-mentioned problems is a brake force estimation method for a vehicle equipped with a steer actuator that steers a steered wheel, the method comprising: detecting a steer reaction force of the steer actuator. The present invention is characterized by comprising a detecting step and a braking force estimating step of estimating the braking force generated on the steered wheel during braking from the distance between the steered wheel and the rotation axis of the steer actuator.

According to the brake force estimating device and the brake force estimating method according to the present invention, the brake force generated during braking is determined by the steer reaction force of the steer actuator and the distance between the steered wheel and the rotation axis of the steer actuator. Since the brake force is estimated by , the brake force can be controlled with high precision. In addition, since the braking force can be controlled with high precision, by correcting each braking force of the regenerative braking device and the friction braking device, the ratio of regenerative braking force and frictional braking force can be optimized and the regenerative braking device can obtain This makes it possible to maximize the amount of power generated and improve vehicle electricity costs.

1 is a schematic diagram of a vehicle equipped with a brake force estimating device according to an embodiment of the present invention. 1 is a perspective view for explaining a steering device for a vehicle including a brake force estimating device according to an embodiment of the present invention. FIG. 2 is a diagram for explaining the operation of a steering system of a vehicle equipped with a brake force estimating device according to an embodiment of the present invention, in which (a) is a straight-ahead state, (b) is a right-turning state, and (c) is a braking state. Diagram showing the state. 1 is a diagram showing the configuration of a brake force estimating device according to an embodiment of the present invention. FIG. 3 is a flow diagram for explaining the operation of the brake force estimating device according to the embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a brake force estimating device according to the present invention will be described with reference to the drawings. Note that the following embodiments do not limit the inventions claimed in each claim, and not all combinations of features described in the embodiments are essential to the solution of the invention. .

FIG. 1 is a schematic diagram of a vehicle equipped with a brake force estimating device according to an embodiment of the present invention, and FIG. 2 is a schematic diagram for explaining a steering device of a vehicle equipped with a brake force estimating device according to an embodiment of the present invention. 3 is a perspective view, and FIG. 3 is a diagram for explaining the operation of a steering system of a vehicle equipped with a brake force estimating device according to an embodiment of the present invention, in which (a) is a state in which the vehicle is traveling straight, and (b) is a state in which the vehicle is turning right. FIG. 4 is a diagram showing the configuration of the brake force estimating device according to the embodiment of the present invention, and FIG. 5 is a diagram showing the configuration of the brake force estimating device according to the embodiment of the present invention. FIG. 3 is a flow diagram for explaining the operation of the brake force estimating device.

As shown in FIG. 1, a vehicle 1 equipped with a brake force estimating device according to the present embodiment has wheels 2 disposed at the front, rear, left, and right corners of the vehicle 1. The wheel 2 has a friction brake means 3 that brakes the rotation of the wheel 2 using frictional force. The wheels 2 are rotatably mounted, for example, by a drive motor 4 arranged to drive the rear wheels. Further, the front wheels are equipped with steering actuators 10 that tilt the wheels 2 in the direction of steering, and function as steered wheels.

The steering actuator 10 is wired so that it can receive a signal from an electronic control unit 7 that performs predetermined processing in response to a signal from an operation unit 6 that has a handle 5 that is operated by the driver. The steering angle is controlled so that the steering angle corresponds to the steering wheel 5 operated by the person.

Further, the electronic control unit 7 is connected to a brake control unit 8, and when the driver operates the brake pedal 9a, the electronic control unit 7 operates the friction brake means 3 and the drive motor 4 as a regenerative brake means in response to the brake operation. control so that

The friction brake means 3 includes a disc-shaped brake disc 3a attached coaxially with the axle of the wheel 2, and a caliper 3b equipped with a brake pad that grips the brake disc 3a from the axial direction. The caliper 3b is connected to a master cylinder (not shown) that is activated when the driver operates the brake pedal 9a, and is pressed against the brake disc 3a by the amplification effect of hydraulic pressure, air pressure, etc. by the master cylinder, and generates frictional force. to occur. The friction brake means 3 receives a signal from the brake control unit 8 and reduces the friction force between the brake pad and the brake disc 3a as necessary, regardless of the pedal force applied by the driver to the brake pedal 9a. The degree of pressing of the caliper 3b can be adjusted accordingly.

The drive motor 4 receives a signal from the electronic control unit 7 according to the opening degree of an accelerator pedal 9b operated by the driver, and rotates so that the vehicle 1 moves forward or backward in the direction of travel. In addition, during braking when the brake pedal 9a is operated, the drive motor 4 inputs shaft rotation and operates as a generator, converting kinetic energy into electrical energy and recovering or consuming it to perform braking. It is also used as a regenerative braking means.

The electronic control unit 7 and the brake control unit 8 have a microprocessor as a control means, and are operated by power supplied from a battery (not shown). The electronic control unit 7 receives signals from the operating unit 6, the brake pedal 9a, the accelerator pedal 9b, etc., processes various signals, and transmits signals to drive the drive motor 4 at a predetermined rotation speed.

The brake control unit 8 receives a signal from the brake pedal 9a and transmits the signal to the friction brake means 3 and the drive motor 4 which operates as a regenerative brake means. At this time, as will be described later, the friction brake means 3 and the regenerative brake means operate at appropriate ratios so that the vehicle 1 can be safely stopped or decelerated.

Next, the steering actuator 10 used in the brake force estimating device according to this embodiment will be described with reference to FIG. 2. The steer actuator 10 includes a shaft member 12 and a rotating member 11 rotatably attached to the shaft member 12 in the circumferential direction, and the rotating member 11 and the shaft member 12 are contained in a case 10a. .

The rotating member 11 can adopt various conventionally known configurations as long as it can receive a signal from the electronic control unit 7 and rotate the case 10a to a steering angle corresponding to the signal. It is preferable to configure it so that it is driven.

The shaft member 12 is held by an upper connecting member 13 and a lower connecting member 14 attached to the body of the vehicle 1. Further, the rotating member 11 has a transmission member 15 extending from the lower end of the case 10a to the outside of the case 10a, and the transmission member 15 is connected to an axle 16 that rotatably holds the wheel 2.

As shown in FIG. 3, when the vehicle 1 is traveling straight, the steering actuator 10 controls the wheels 2 to face in the traveling direction without changing the steering angle, as shown in FIG. When the steering wheel 5 is operated, the wheels 2 are steered to a steering angle corresponding to the steering wheel operation, as shown in (b).

Furthermore, during braking when the driver operates the brake pedal 9a, a braking force F is generated on the wheel 2, as shown in FIG. The steering actuator 10 receives the brake force F and is controlled to generate a steering reaction force C in order to maintain the steering angle (in FIG. 3(c), the straight traveling state). This steering reaction force C can be detected from the current value generated in the steering actuator 10.

Specifically, the brake force F can be calculated by the following formula from the steering reaction force C and the distance L from the center of the wheel 2 serving as the steered wheel to the rotation axis of the steering actuator 10.
Steering reaction force C = Brake force F x Axial center distance L (1)

In this way, the steering reaction force C can be detected from the current value generated in the steering actuator 10, so the steering reaction force can be detected with high accuracy without adding a new means for measuring the steering reaction force C. It becomes possible to calculate the brake force F with high precision.

Next, an overview of the brake force estimating device according to this embodiment will be explained with reference to FIG. 4. As shown in FIG. 4, the brake force estimating device according to the present embodiment includes a brake pedal 9a operated by a driver, and a master that is operated by the operation of the brake pedal 9a and amplifies the hydraulic pressure or air pressure applied to the caliper piston 3c. A friction brake means 3 consisting of a cylinder 3d, a caliper piston 3c that applies pressing force to the brake pad 3b, and a brake pad 3b that is pressed against the brake disc 3a and generates a frictional force, and It has regenerative braking means 4 which inputs shaft rotation in the opposite direction to the motor 4 to operate it as a generator, converts kinetic energy into electrical energy, recovers or consumes it, and uses it for braking.

Furthermore, when the brake force estimating device according to the present embodiment receives a signal from the brake sensor 23 that detects that the driver is braking by operating the brake pedal 9a, the brake force estimating device calculates the steering reaction force C of the steering actuator 10. The brake force estimator 21 estimates the brake force F exerted on the wheel 2 from the steering reaction force C detected. Furthermore, after the brake force F is estimated, a brake force correction unit 22 is provided which determines the ratio of the friction brake means 3 and the regenerative brake means 4 according to the estimated brake force F.

It is preferable that the brake force estimation section 21 and the brake force correction section 22 undergo signal processing in the brake control unit 8. It is preferable that the brake force correction unit 22 includes a storage unit that stores the estimated brake force F. By including the storage unit, it is possible to store the current state of the brake force of the wheels 2. It is possible to learn the braking force of , and correct the ratio of the friction braking means 3 and the regenerative braking means 4 according to the learned braking force.

Further, the brake force correction unit 22 adjusts the friction force of the friction brake means 3 by adjusting the master cylinder 3d to adjust the pressing force of the brake pad 3b according to the ratio of the friction brake means 3 and the regenerative brake means 4. By controlling the current value of the regenerative braking means 4 or adjusting the current value of the regenerative braking means 4, the amount of power generated by the regenerative braking means 4 can be adjusted.

At this time, the ratio of the regenerative braking means 4 and the friction braking means 3 is such that the friction braking means 3 is used to the extent that the vehicle 1 can be safely stopped or decelerated, and the remaining braking force is provided by the regenerative braking means 3. By controlling to use the regenerative braking means 4, the proportion of the regenerative braking means 4 can be secured as much as possible, and the amount of power generated by the regenerative braking means 4 can be secured.

Next, the operation of the brake force estimating device according to this embodiment will be explained with reference to FIG. First, the driver operates the brake pedal 9a to determine whether the vehicle 1 is braking (S101). It is preferable to determine whether or not braking is in progress by receiving a signal from a brake sensor or the like included in the brake pedal 9a. Here, if it is determined that the vehicle is not braking, the process ends.

When it is determined that the brake is being applied, the steering reaction force C of the steering actuator 10 is detected (steering reaction force detection step: S102). The steering reaction force C is detected from the current value generated in the steering actuator 10 (current value detection step). The current value detection step is preferably performed by the electronic control unit 7 that controls the steer actuator 10.

Next, the brake force F is calculated from the steering reaction force C detected in the steering reaction force detection step (S102) (brake force estimation step: S103). The brake force estimation step (S103) is preferably performed by the brake control unit 8, and is calculated using the above-mentioned equation (1).

The optimum ratio of the friction brake means 3 and the regenerative brake means 4 is determined according to the brake force F estimated in the brake force estimation step (S103), and the brake is applied to the friction brake means 3 and the regenerative brake means 4 at the optimum ratio. Each brake force is corrected by distributing the force (S104).

This optimum ratio is preferably controlled so that the minimum ratio of the friction brake means 3 necessary for braking is secured from the currently generated brake force F, and the regenerative brake means 4 is used to the maximum extent. Note that when the ratio of the friction brake means 3 to the regenerative brake means 4 at the time of control is low, the ratio of the friction brake means 3 is increased to ensure braking force. You can also do that. In this case, the brake control unit 8 transmits a signal to the master cylinder 3d to increase the amplification amount.

In addition, the latest state of the estimated braking force F is always stored, and by understanding the current braking force of the friction braking means 3, the ratio of the friction braking means 3 and the regenerative braking means 4 is always set at the optimum ratio. Brake force can be distributed.

In this way, in the vehicle 1 equipped with the friction brake means 3 and the regenerative brake means 4, the brake force F can be estimated with high accuracy from the steering reaction force C generated in the steer actuator 10. It is possible to control with high precision, and as a result, the ratio of the friction brake means 3 and the regenerative brake means 4 can be controlled to a ratio that allows the regenerative brake means 4 to be used to the maximum. It is possible to secure the amount of power that can be generated in the vehicle 1, thereby improving the electricity cost of the vehicle 1.

In the embodiment described above, a case has been described in which the estimated braking force is used to find the optimal ratio of the friction braking means 3 and the regenerative braking means 4, but the braking force estimation according to the present embodiment According to the method, the braking force of the friction brake means 3 can be controlled with high precision, so for example, by applying it to an ABS device (Anti-lock Braking System), it is possible to perform highly precise control that does not cause tire lock. It is possible.

Furthermore, by applying the brake force estimation method according to the present embodiment to a traction control system (TCS), it is possible to configure the method to detect the slipping state of the wheels 2 with high accuracy. Moreover, although the brake force estimating device and the brake force estimation method according to the present embodiment have been described in terms of learning the brake force by feeding back the estimated brake force to the electronic control unit 7, The estimation may be performed in real time without providing feedback to the electronic control unit 7. Alternatively, instead of estimating the brake force in real time, for example, the brake force may be estimated during the first braking after starting the vehicle, and the estimated brake force may be used during the start of the vehicle. It is clear from the claims that such modifications or improvements can be included within the technical scope of the present invention.

1 vehicle, 2 wheels, 3 friction brake means, 4 regenerative brake means (
10 Steering actuator, 21 Brake force estimation section (Brake force estimation means), 22 Brake correction section (Brake correction means), S102 Steering reaction force detection process, S103 Brake force estimation process, S104 Brake force correction process.

Claims (6)

A brake force estimation device for a vehicle equipped with a steer actuator that steers a steering wheel,
The vehicle is characterized by comprising a brake force estimating means for estimating the brake force generated during braking based on the steering reaction force of the steer actuator and the distance between the steered wheel and the rotation axis of the steer actuator. Brake force estimation device. The brake force estimating device according to claim 1,
The brake force estimating device is characterized in that the steering reaction force is obtained by a current value at which the steering actuator attempts to maintain a steering angle. The brake force estimating device according to claim 1 or 2,
The vehicle has regenerative braking means and friction braking means,
A braking force characterized by comprising a braking force correction means for feeding back the estimated braking force to the regenerative braking means and the friction braking means to correct the braking forces of the regenerative braking means and the friction braking means. Estimation device. The brake force estimating device according to claim 3,
The braking force estimating device is characterized in that the correction includes controlling the regenerative braking means so as to use the friction braking means to a minimum. A brake force estimation method for a vehicle equipped with a steer actuator for steering steering wheels, the method comprising:
a steering reaction force detection step of detecting a steering reaction force of the steering actuator;
A brake force estimation method comprising: a distance between the steered wheel and the rotation axis of the steer actuator; and a brake force estimation step of estimating a brake force generated at the steered wheel during braking. In the brake force estimation method according to claim 5,
The brake force estimation method is characterized in that the steering reaction force detection step includes a current value detection step of detecting a current value at which the steering actuator attempts to maintain a steering angle.

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