KR20220036480A - Method And Apparatus for Controlling Electro-Mechanical Brake - Google Patents

Abstract

According to an embodiment of the present disclosure, a drive unit including a motor for generating a driving force and a brake pad for braking a vehicle by generating a friction force by contacting with a disk using the driving force ); a sensor unit including at least one of a position sensor for measuring a distance of the motor and a current sensor for measuring a current flowing through the motor; and calculating a braking force for braking the vehicle based on the braking input, estimating a contact point between the brake pad and the disk based on the current value, and after the brake pad reaches the contact point, based on the operating distance To provide an electric brake device comprising a control unit (ECU: Electronic Control Unit) for estimating the clamping force.

Description

Electric brake device and control method {Method And Apparatus for Controlling Electro-Mechanical Brake}

An embodiment of the present disclosure relates to an electric brake device and a control method.

The content described in this section merely provides background information for the present disclosure and does not constitute the prior art.

Electro-Mechanical Brake (EMB) has been developed and is widely used. The electric brake has been developed as an Electronic Parking Brake (EPB), but its use area has recently been expanded for a main brake replacing the conventional hydraulic brake. The EMB is a device in which an actuator driven by a motor is mounted on a brake caliper, and the vehicle is directly braked by motor driving force without a medium such as brake fluid. The EMB has a mechanism similar to that of the Electronic Parking Brake (EPB), but unlike the EPB, it is mainly used for main braking, and thus requires higher braking response and operational durability than the EPB. In addition, the electric brake has a simpler structure, faster braking response speed, and more precise control than a hydraulic brake, thereby improving braking safety.

6 is a graph showing the current flowing through the motor and the clamping force acting on the brake pad over time.

Referring to FIG. 6 , when the controller forms a clamping force on the brake pad, it can be seen that the current flowing through the motor increases as the clamping force increases. That is, the clamping force increases in proportion to the strength of the current flowing through the motor.

The EMB uses a load sensor to form a target braking force required by the driver. An electric brake equipped with a load sensor can accurately measure the clamping force. However, when the EMB is equipped with a load sensor, the design of the part where the sensor is mounted becomes complicated, and the manufacturing cost increases. In addition, an increase in the size of the EMB according to the sensor mounting is also inevitable.

In addition to the method of measuring the clamping force using a load sensor, the clamping force can be measured or estimated based on the current flowing through the motor that generates the braking force. However, in the method of estimating the clamping force by measuring the current flowing through the motor, as can be seen from the current graph of FIG. 6 , inrush occurs without maintaining a constant value. In other words, since the current sensor value is unstable and the signal has a large noise, the error is larger than when using a load sensor, and the accuracy in estimating the clamping force is lowered, and there is a problem in securing the stable braking performance of the vehicle. there is.

Accordingly, an object of the present disclosure is to reduce the size of the EMB by simplifying the design of the EMB by removing the load sensor from the EMB, and to reduce the manufacturing cost of the EMB.

In addition, the present disclosure estimates the clamping force using the current value of the motor, but finds the position of the contacting point based on the time when the brake pad contacts the disk. Thereafter, another main purpose is to secure stable performance when the vehicle brakes by performing position control with a small error instead of unstable current control based on the contact point.

According to an embodiment of the present disclosure, a drive unit including a motor for generating a driving force and a brake pad for braking a vehicle by generating a friction force by contacting with a disk using the driving force ); a sensor unit including at least one of a position sensor for measuring a distance of the motor and a current sensor for measuring a current flowing through the motor; and calculating a braking force for braking the vehicle based on the braking input, estimating a contact point between the brake pad and the disk based on the current value, and after the brake pad reaches the contact point, based on the operating distance To provide an electric brake device comprising a control unit (ECU: Electronic Control Unit) for estimating the clamping force.

In addition, a calculation process of calculating a braking force required for the vehicle by detecting the braking request of the vehicle; a contact point determination process of determining a contact point between the brake pad and the disk based on the current flowing through the motor; a mode conversion process of changing the mode from the current control mode to the position control mode when it is determined that the brake pad has reached the contact point; and a clamping force estimation process of estimating a clamping force applied to the brake pad based on the operating distance of the motor. It provides an electric brake control method comprising a.

As described above, according to the present embodiment, as the load sensor is removed, the design of the electric brake is simplified and the size thereof is reduced.

Also, according to the present embodiment, the clamping force is estimated using the current value of the motor, but the position of the contacting point is found based on the time when the brake pad contacts the disk. Then, there is another effect of securing stable performance when the vehicle brakes by performing position control with a small error instead of unstable current control based on the contact point.

1 is a block diagram of a brake device according to an embodiment of the present disclosure.
2 is a graph showing the relationship between the operating distance of the motor and the force.
3 is a flowchart illustrating an algorithm of a controller according to an embodiment of the present disclosure.
4 is a graph showing the current measurement value and the position of the piston over time according to an embodiment of the present disclosure.
5 is a graph illustrating a current flowing through a motor and an operating distance of the motor over time according to an exemplary embodiment of the present disclosure.
6 is a graph showing the current flowing through the motor and the clamping force acting on the brake pad over time.

Hereinafter, some embodiments of the present disclosure will be described in detail with reference to exemplary drawings. In adding reference numerals to components in each drawing, it should be noted that the same components are given the same reference numerals as much as possible even though they are indicated in different drawings. In addition, in describing the present disclosure, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present disclosure, the detailed description thereof will be omitted.

In describing the components of the embodiment according to the present disclosure, reference numerals such as first, second, i), ii), a), b) may be used. These signs are only for distinguishing the elements from other elements, and the essence, order, or order of the elements are not limited by the signs. When a part in the specification 'includes' or 'includes' a certain component, it means that other components may be further included, rather than excluding other components, unless explicitly stated to the contrary. .

1 is a block diagram of a brake device according to an embodiment of the present disclosure.

Referring to Figure 1, according to an embodiment of the present disclosure, an electric brake (EMB: Electronic Mechanical Brake, 100) is a sensor unit (sensor unit, 110), a control unit (ECU: Electronic Control Unit, 120) and a drive unit (drive unit) , 130) in whole or in part.

The sensor unit 110 includes all or part of a position sensor 112 and a current sensor 114 .

The position sensor 112 measures an operating distance of the motor 132 . Here, the operating distance refers to a linear movement of the piston 136 of the electric brake 100 as the motor 132 rotates. Here, the operating distance of the motor 132 means a linear movement distance of the piston 136 .

Meanwhile, in order for the electric brake 100 to generate a braking force, the piston 136 presses the brake pad 138 , where the force that the piston 136 presses the brake pad 138 is referred to as a clamping force. define.

A current sensor 114 measures a current flowing through the motor 132 .

The control unit 120 includes a braking input determining unit 121, a braking force calculation unit 122, a contact point estimating unit 123, and a mode change determining unit. , 124 ), and all or part of a drive controller unit 125 .

The controller 120 according to an embodiment of the present disclosure estimates the clamping force using current control and position control. Here, the current control is a control method for estimating the clamping force based on the current flowing through the motor. On the other hand, the position control is a control method for estimating the clamping force based on the operating distance of the motor.

However, since the reference position value, ie, a contact point, is changed according to the wear state of the brake pad 138 in the position control, the contact point must be initially found using current control. Here, the contact point means a point where the brake pad 138 and the disk start contact.

The braking input determination unit 121 determines whether braking is required for the vehicle. Whether braking is required for the vehicle is determined based on various factors, for example, a stroke of a brake pedal.

When the braking input determining unit 121 determines that braking is required, the braking force calculating unit 122 calculates a braking force required to brake the vehicle. When the braking force calculating unit 122 calculates the braking force, the driving unit 130 supplies a braking force corresponding to the calculated braking force to a plurality of wheel brakes (not shown).

The contact point determination unit 123 determines a position where a brake pad 138 and a disk (not shown) contact each other, that is, a contact point.

The contact point determination unit 123 according to an embodiment of the present disclosure uses the current measurement value to determine the contact point.

The mode change determination unit 124 determines whether to switch a mode in which the control unit estimates a force. Here, the mode means a current control mode and a position control mode in the detailed description of the present disclosure. Here, the force means a clamping force.

When the mode change determination unit 124 determines the mode conversion time point, the mode change determination unit 124 determines that the brake pad 138 has reached the contact point determined by the contact point determination unit 123, and sets the clamping force mode. Change from current control mode to position control mode. The process of changing to the position control mode will be described in more detail with reference to FIG. 3 .

In addition, one embodiment of the present disclosure is not limited thereto, and includes another embodiment in which the position control mode is performed from the beginning without changing the mode. In a situation where emergency braking is required instead of a general braking situation, the control process of the contact point determination unit 123 and the mode change determination unit 124 may have a negative effect on braking responsiveness. Therefore, when emergency braking is required, the contact point determination process and the control mode switching process are not performed, but only the position control is performed in the entire section to estimate the force.

The driving control unit 125 controls the driving unit 130 so that the driving unit 130 generates the braking force calculated by the braking force calculating unit 122 .

The driving unit 130 includes a motor 132 , a gear box 134 , a piston 136 , a brake pad 138 , and a caliper body (not shown).

The motor 132 rotates in a forward or reverse direction as current flows to generate a driving force. Here, the driving force means a rotational force of the motor 132 . The rotational force of the motor 132 is transmitted to a screw (not shown) of the gearbox 134 to form a braking force.

The gearbox 134 includes a plurality of gears and screws for linear motion of a spindle (not shown) by the rotational force of the motor 132 . When the spindle of the gearbox makes a linear motion, the piston 136 attached to one end of the caliper body moves forward or backward, and accordingly, the brake pad 138 connected to the piston presses the disk (disc, not shown). to form a braking force.

In the present disclosure, a typical configuration related to the driving of the gearbox 134 is a technique that is obvious to those skilled in the art, and thus the illustration and description thereof will be omitted.

Although the electric brake (EMB, 100) described in the present disclosure has been developed as an electric parking brake (EPB), its use area has recently been expanded for a main brake replacing a conventional hydraulic brake. .

The electric brake 100 generally has an integrated parking function, but an embodiment of the present disclosure includes both a main brake without a parking function and a main brake equipped with a parking function.

2 is a graph showing the relationship between the operating distance of the motor and the force.

Referring to FIG. 2 , the horizontal axis of the graph indicates the operating distance of the motor 132 , and the vertical axis of the graph indicates force.

The force estimation method according to an embodiment of the present disclosure may estimate the force based on the motor operating distance measured by the position sensor.

The electric brake according to an embodiment of the present disclosure is characterized in that the force is estimated using a position sensor or a current sensor without a load sensor.

Comparing a general braking device including a load sensor and an exemplary embodiment of the present disclosure, the general braking device may accurately find the point b using the load sensor. Here, point b means the force of the contact point. Meanwhile, a denotes a contact point and an air gap between the brake pad 138 and the disc. Here, the air gap refers to a gap of a certain distance between the friction material, for example, the brake pad 138 and the disc before generating a braking force, and this gap is referred to as an air gap.

The reason that a means an air gap is that the brake pad 138 and the disc do not contact from the initial braking state to the contact point, where the brake pad 138 and the disc are spaced apart from each other while maintaining a constant distance. That is, because a represents the distance the brake pad moves from the initial state to the contact point.

On the other hand, the electric brake according to an embodiment of the present disclosure has to estimate the point b, where when the point b is estimated, the contact point varies depending on the wear state of the brake pad 138, so the estimation error is Occurs. Here, the estimation error means a difference between the estimated value of the clamping force according to the operating distance of the motor 132 and the clamping force applied by the actual piston 136 to the brake pad 138 .

When the electric brake 100 generates braking force, if the operating distance of the motor 132 is the same, the same clamping force should be transmitted to the brake pad 138 , and the actual piston is transmitted to the brake pad 138 according to various factors. The clamping force is different.

There are many factors that cause estimation error, but the main three factors will be described in more detail.

First, in the pressing process of generating braking force by operating the electric brake 100 and the decompression process of dissipating the braking force by releasing the operation of the electric brake 100, the clamping force at the same point as the operating distance of the motor 132 There is a difference. That is, since there is a difference between the clamping force that increases when pressurizing and the clamping force that decreases when decompression is applied, an error in estimating the clamping force occurs.

Second, the estimation error of the clamping force occurs depending on the condition of the air gap. For example, when the gap between the disc and the brake pad 138 increases as the brake pad 138 is worn, the air gap increases. That is, since there is a difference in the condition of the air gap for each wheel brake, an error in the estimation of the clamping force occurs.

Third, an estimation error of the braking force occurs according to the temperature of the brake pad 138 . The process in which the brake pad 138 generates the braking force is a process in which the brake pad 138 comes into contact with the disk to generate frictional force, and a portion of kinetic energy is converted into thermal energy by the frictional force, thereby reducing the rotational speed of the disk. . Here, a difference occurs in the amount of decrease in the rotational speed in the case where the temperature of the brake pad 138 is high and when the temperature is low. That is, since there is a difference in the temperature of the brake pad 138 for each wheel brake, an error in estimation of the braking force occurs.

Accordingly, an embodiment of the present disclosure finds a contact point by minimizing an estimation error by appropriately using a current sensor and a position sensor.

3 is a flowchart illustrating an algorithm of a controller according to an embodiment of the present disclosure.

4 is a graph showing the current measurement value and the position of the piston over time according to an embodiment of the present disclosure.

3 and 4 , the controller 120 determines whether there is a braking input to the vehicle (S310). The controller 120 determines whether a braking input is required according to various input signals of the vehicle, for example, whether a brake pedal is depressed.

When it is determined that the vehicle has no braking input, the present algorithm is terminated.

Meanwhile, when it is determined that the vehicle has a braking input, the controller 120 calculates a braking force required to brake the vehicle in response to the braking input ( S320 ). The process of calculating the braking force includes, for example, a clamping force required for braking.

The control unit 120 flows a preset current to the motor to generate the calculated braking force (S330). Here, the preset current is a current for the brake pad 138 to reach a contact point in contact with the disk, and is a value set in advance based on the braking force. For example, if a point where a clamping force of about 100 N is generated is defined as a contact point, a value of the phase current of the three-phase motor to which the clamping force can reach 100 N is preset in advance.

The controller 120 determines whether the brake pad 138 has reached the contact point by the supply of current (S340).

Here, in order to determine whether the brake pad 139 has reached the contact point, the current measurement value graph of FIG. 4 is used. In Fig. 4, a denotes a contact point.

The error decreases before and after point a in the current flowing through the motor. That is, before reaching point a, the error of the current flowing through the motor is large, but after reaching point a, the error decreases. That is, the controller 120 determines that the brake pad 138 has reached the contact point when the error range of the current measurement value flowing through the motor within a predetermined time is smaller than the predetermined reference.

When it is determined that the brake pad 138 has not reached the contact point, the controller 120 repeats the process S330 to continuously supply current to the motor until the contact point is reached.

On the other hand, when it is determined that the brake pad 138 has reached the contact point, the controller 120 stores the current measured value flowing at the contact point (S350). That is, the position of the contact point is stored.

The stored values can be used to reduce the margin of error.

After completing the storage, the controller 120 changes the mode from the current control mode to the position control mode (S360).

Here, the control method according to an exemplary embodiment of the present disclosure is not limited thereto, and when the vehicle performs emergency braking, the contact point determination process, the storage process, and the switching process of the controller 120 may negatively affect the braking responsiveness. Therefore, when emergency braking is required, the contact point determination process, the storage process, and the control mode switching process are not performed, but only the position control is performed in the entire section to estimate the force.

When the controller 120 changes the mode to the position control mode, it is determined whether the brake pad 138 has reached a target position (S370).

When the brake pad 138 does not reach the target position, the controller 120 continuously performs position control and supplies current until the brake pad 138 reaches the target position.

On the other hand, when it is determined that the brake pad 138 has reached the target position and it is determined that sufficient braking force is formed to allow the vehicle to brake, the present algorithm ends.

5 is a graph illustrating a current flowing through a motor and an operating distance of the motor over time according to an exemplary embodiment of the present disclosure.

Referring to FIG. 5 , the upper graph is a graph showing the current flowing in the motor over time when the controller 120 supplies braking force to the vehicle, and the lower graph is when the controller 120 releases the braking force formed in the vehicle. This is a graph showing the operating distance of the motor over time.

In section A of the upper graph, the controller prioritizes the current control mode over the position control mode, and in section B, the controller prioritizes the position control mode over the current control mode.

First, referring to section A of the upper graph, it is indicated according to the time of the process in which the driver's braking request is sensed and the braking force is formed in the vehicle. The controller 120 supplies a preset constant current value so that the brake pad 138 can reach the contact point.

When the brake pad 138 reaches the contact point, the controller 120 switches the current control mode to the position control mode. Accordingly, in section B, the controller 120 supplies a current to the motor based on the operating distance of the motor.

Meanwhile, referring to the graph at the bottom, when releasing the braking force formed in the vehicle, only the position control is performed in all sections regardless of sections A and B. When releasing the braking force, since the braking force is released while the brake pad 138 and the disk are in contact, only the position control is performed without changing a separate control mode.

The above description is merely illustrative of the technical idea of this embodiment, and various modifications and variations will be possible without departing from the essential characteristics of the present embodiment by those skilled in the art to which this embodiment belongs. Accordingly, the present embodiments are intended to explain rather than limit the technical spirit of the present embodiment, and the scope of the technical spirit of the present embodiment is not limited by these embodiments. The protection scope of this embodiment should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present embodiment.

110: sensor unit 120: control unit
130: driving unit

Claims (8)

a drive unit including a motor for generating a driving force, and including a brake pad for braking the vehicle by contacting a disc using the driving force to generate a friction force;
a sensor unit including at least one of a position sensor for measuring a distance of the motor and a current sensor for measuring a current flowing through the motor; and
A braking force for braking the vehicle is calculated based on a braking input, a contact point between the brake pad and the disk is estimated based on the current value, and after the brake pad reaches the contact point In the control unit (ECU: Electronic Control Unit) for estimating the clamping force based on the operating distance
Electric brake device comprising a. The method of claim 1,
The control unit is
When there is the braking input, a preset current is supplied to the motor based on the braking force;
The electric brake device, characterized in that the point at which the error of the current value is reduced is determined as the contact point. 3. The method of claim 2,
The control unit is
When the error does not change in the current value, the electric brake device, characterized in that the current is continuously supplied until the error changes. The method of claim 1,
The control unit is
Determining whether emergency braking is required for the vehicle,
When it is determined that the emergency braking is required, the clamping force is estimated based on the operating distance without estimating the contact point. The method of claim 1,
The braking input is a depression amount of the driver's brake pedal,
The control unit calculates the braking force based on the depression amount. a calculation process of detecting a braking request and calculating a braking force required for the vehicle;
a contact point determination process of determining a contact point between the brake pad and the disk based on a current value flowing through the motor;
a mode conversion process of changing a mode from a current control mode to a position control mode when it is determined that the brake pad has reached the contact point; and
Clamping force estimation process of estimating the clamping force applied to the brake pad based on the operating distance of the motor
Electric brake control method comprising a. 7. The method of claim 6,
The contact point determination process is
An electric brake control method, characterized in that it is determined that the point at which the error occurring in the current value is reduced is the contact point. 8. The method of claim 7,
The contact point determination process is
supplying a preset current to the motor based on the braking force;
When the error does not change in the current value, the electric brake control method, characterized in that the contact point is determined by continuously supplying current until an error occurs.

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