Electro Mechanical Brake And Control Method Therefor

Abstract

An electric brake and a method for controlling the same are disclosed. According to one embodiment of the present disclosure, a control method for an electric brake comprising a piston that presses a brake pad toward a wheel disc side by driving a motor comprises: a process of generating a plurality of braking data corresponding to a current of the motor measured during braking and a position of the measured piston; a process of determining a correction value for changing a preset home position based on the plurality of braking data; a process of changing the preset home position by the correction value to set a new home position; and a process of calculating an actual braking force value based on the distance the piston has moved from the new home position, wherein each of the plurality of braking data includes a target braking force value and a current-based estimated braking force value, and each of the plurality of braking data is classified into one of a first area braking data, a second area braking data, and a third area braking data according to the magnitude of the target braking force value.

Description

Technology Field

[0001] The present disclosure relates to an electric brake and a method for controlling the same. Background Technology

[0002] The content described in this section merely provides background information regarding the present disclosure and does not constitute prior art.

[0003] An electro-mechanical brake (EMB) is a braking apparatus that generates friction brake force. In an electro-mechanical brake, an actuator driven by a motor is mounted on the brake caliper. The electro-mechanical brake applies pressure to the wheel disk using a motor, gearbox, screw, piston, brake pad, etc., without the medium of brake fluid.

[0004] Electric brakes have a mechanism similar to the Electronic Parking Brake (EPB), but because they are the main braking system used while driving, they require higher reliability and durability.

[0005] When the driver presses the brake pedal, the electric brake calculates the required braking force and applies a brake command to each wheel. When the brake command is applied, the motor starts to rotate and advances the piston, and the piston presses the brake pad. The brake pad presses the wheel disc, generating braking force.

[0006] Conventional electro-mechanical brakes (EMBs) measure and control braking force using force sensors. Force sensors installed in electric brakes are expensive. In addition, force sensors have the disadvantage of not being able to accurately measure braking force depending on their mounting location. To overcome these disadvantages, force sensor-less systems are used.

[0007] A force sensorless system refers to a system that estimates braking force without using a force sensor. An electric brake equipped with a force sensorless system performs calibration. Here, calibration refers to the process of setting the electric brake. By performing calibration, the electric brake can determine the braking force value corresponding to the piston position. A map indexed with braking force values ​​corresponding to the piston position is called a force map. Based on the force map, the electric brake can determine and adjust the braking force without a force sensor.

[0008] Since the condition of the electric brake changes with use, such as as the brake pads wear out, the electric brake information must be updated by performing a new calibration every time the vehicle is used. It is desirable to perform the calibration before starting to drive. For example, calibration can be performed and a force map generated when the driver opens the vehicle door or starts the vehicle.

[0009] In other words, electric brakes utilizing a force sensorless system can perform calibration to determine the current state of the electric brake and generate data for estimating braking force. It is important that the calibration be completed quickly, as the driver can drive after the calibration is complete.

[0010] Calibration is generally performed only when the driver opens the vehicle door or starts the engine. It is not advisable to perform calibration while driving. This is because the calibration process involves driving a motor to move the piston and brake pads, as well as pressurizing the wheel disc to generate braking force. If calibration is performed involuntarily while driving, the driver may experience an unnatural braking sensation, and a traffic accident may occur.

[0011] The force map generated when the driver opens the vehicle door or starts the engine reflects only the state of the electric brake at the time of generation. The force map cannot reflect in real time the state of the electric brake that changes due to braking while driving. For example, when braking while driving, the brake pads may wear down, causing a change in their stiffness. When braking while driving, the brake pads may expand due to heat. In cold environments, the brake pads may contract as they cool down.

[0012] As such, when the state of the electric brake changes from the state at the time the force map was generated due to braking performed while driving, a method is required to accurately estimate the braking force during driving without performing additional calibration. This is because, as explained above, performing calibration while driving is not desirable. In other words, when the state of the electric brake changes from the initial state due to braking performed while driving, a method is required to accurately estimate the braking force by reflecting the changed state. The problem to be solved

[0013] Accordingly, the present disclosure aims to solve these problems and has the primary objective of providing a method to accurately detect braking force during driving when the state of the electric brake changes from the state prior to driving due to braking performed during driving.

[0014] In other words, the main purpose is to provide a method that can accurately detect braking force by identifying the state of the electric brake, which has changed due to driving, without performing calibration.

[0015] The problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description below. means of solving the problem

[0016] According to one embodiment of the present disclosure for achieving the above purpose, a control method for an electric brake comprising a piston that presses a brake pad toward a wheel disc side by driving a motor, the method comprises: generating a plurality of braking data corresponding to the current of the motor measured during braking and corresponding to the position of the measured piston; determining a correction value for changing a preset home position based on the plurality of braking data; changing the preset home position by the correction value to set a new home position; and calculating an actual braking force value based on the distance the piston has moved from the new home position, wherein each of the plurality of braking data includes a target braking force value and a current-based estimated braking force value, and each of the plurality of braking data is classified into one of a first area braking data, a second area braking data, and a third area braking data according to the magnitude of the target braking force value.

[0017] According to one embodiment of the present disclosure for achieving the purpose, an electric brake comprising a piston that presses a brake pad toward a wheel disc by driving a motor, the electric brake comprises: a sensor unit that measures the current of the motor and measures the position of the piston; and a processor that generates a plurality of braking data corresponding to the measured current of the motor and the measured position of the piston while performing braking, determines a correction value for changing a preset home position based on the plurality of braking data, changes the preset home position by the correction value to set a new home position, and calculates an actual braking force value based on the distance the piston has moved from the new home position, wherein each of the plurality of braking data includes a target braking force value and a current-based estimated braking force value, and each of the plurality of braking data is classified into one of a first area braking data, a second area braking data, and a third area braking data according to the magnitude of the target braking force value. Effects of the invention

[0018] As explained above, according to the present embodiment, the electric brake has the effect of accurately detecting the actual braking force value during driving when the state of the electric brake changes from the state before driving due to braking performed during driving.

[0019] In other words, since the state of the electric brake, which has changed due to driving, can be identified without performing calibration, the actual braking force value can be accurately detected without stopping driving. Brief explanation of the drawing

[0020] FIG. 1 is a functional block diagram of an electric brake according to one embodiment of the present disclosure. FIG. 2 is a drawing illustrating a braking force generating unit according to one embodiment of the present disclosure. FIG. 3 is a graph showing a first map according to one embodiment of the present disclosure. FIG. 4 is a graph illustrating the correlation between the current and the braking force of a motor according to one embodiment of the present disclosure. FIG. 5 is a drawing illustrating various braking force curves over time when the brake pedal is pressed in a first state according to one embodiment of the present disclosure. FIG. 6 is a drawing illustrating a first brake pad and a second brake pad when a piston according to one embodiment of the present disclosure is positioned in a preset home position. FIG. 7 is a drawing illustrating a case where a previously set home position is changed to a new home position according to one embodiment of the present disclosure. FIG. 8 is a flowchart illustrating a control method for an electric brake according to one embodiment of the present disclosure. FIG. 9 is a flowchart showing one example of the detailed process of S830 of FIG. 8. FIG. 10 is a graph illustrating data of a first map according to one embodiment of the present disclosure, and is a diagram for explaining a method of calculating each difference value of a plurality of difference values ​​using the graph of the first map data. Specific details for implementing the invention

[0021] Some embodiments of the present disclosure are described in detail below with reference to exemplary drawings. It should be noted that in assigning reference numerals to the components of each drawing, the same components are given the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the present disclosure, if it is determined that a detailed description of related known components or functions could obscure the essence of the present disclosure, such detailed description is omitted.

[0022] In describing the components of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are used merely to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by the terms.

[0023] Where it is stated that one component is 'connected', 'combined', or 'joined' to another component, it should be understood that while the component may be directly connected or joined to the other component, another component may also be 'connected', 'combined', or 'joined' between each component.

[0024] Throughout the specification, when a part is described as 'including' or 'equipped' with a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0025] Terms such as 'part', 'module', etc., as described in the specification refer to a unit that processes at least one function or operation, and this may be implemented in hardware, software, or a combination of hardware and software.

[0026] It should be noted that, unless otherwise stated, the description of any one embodiment may also apply to other embodiments.

[0027] The description of the invention disclosed below, together with the accompanying drawings, is intended to describe exemplary embodiments of the invention and is not intended to represent the only embodiment in which the invention may be practiced.

[0028] FIG. 1 is a functional block diagram of an electric brake according to one embodiment of the present disclosure.

[0029] FIG. 2 is a drawing illustrating a braking force generating unit according to one embodiment of the present disclosure.

[0030] Referring to FIGS. 1 and 2, the electro-mechanical brake (EMB, 1) may include a brake force generating unit (100), a sensor unit (110), a memory (120), and a processor (130). The electro-mechanical brake (1) generates a friction brake force. Since the electro-mechanical brake (1) does not use hydraulics, it has a fast response speed and is more environmentally friendly than a hydraulic brake (not shown). The electro-mechanical brake (1) enables independent control of each wheel (not shown), resulting in high braking stability.

[0031] The braking force generating unit (100) calculates the required braking force based on the driver's stroke amount when the driver presses the brake pedal (not shown) and then generates the braking force. The braking force generating unit (100) can be mounted on the wheels of the vehicle to generate braking force. The braking force generating unit (100) can be mounted on each wheel of the vehicle. The braking force generating unit (100) is capable of independent braking force generation and independent control for each wheel. The braking force generating unit (100) uses friction to convert the vehicle's kinetic energy into thermal energy to brake the vehicle.

[0032] The braking force generating unit (100) may include all or part of a motor (210), a gear box (220), a power transfer unit (230), a piston (240), a brake pad (250), a rotation shaft (270), and a wheel disc (260). The braking force generating unit (100) is not limited by the disclosure of the drawing. For example, the shape, size, arrangement, etc. of the motor (210), gear box (220), power transfer unit (230), piston (240), brake pad (250), rotation shaft (270), and wheel disc (260) are not limited by the disclosure of the drawing.

[0033] The motor (210) rotates to move the piston (240). The direction of the piston (240) as used in this specification is defined. Forward movement means the case where the piston (240) moves toward the wheel disk (260). Reverse movement means the case where the piston (240) moves toward the opposite direction of the wheel disk (260). The rotation direction of the motor (210) is defined. When the motor (210) rotates in the forward direction, the piston (240) moves forward. When the motor (210) rotates in the reverse direction, the piston (240) moves backward.

[0034] According to one embodiment, the motor (210) may be a DC motor, an AC motor, an induction motor, a synchronous motor, a step motor, a servo motor, a BLDC motor (Brushless Direct Current motor), a linear motor, or a Permanent Magnet Synchronous Motor (PMSM), etc.

[0035] One side of the gearbox (220) is connected to the motor (210), and the other side of the gearbox (220) is connected to the power transmission unit (230). The gearbox (220) is configured to transmit power from the motor (210) to the power transmission unit (230). The gearbox (220) includes a plurality of gears (221) inside. The gearbox (220) can distribute rotational power by meshing and rotating the plurality of gears (221). The shape and arrangement of the gearbox (220) are not limited by the drawings. Each of the plurality of gears (221) is not limited to the shape and number disclosed in the drawings.

[0036] The power transmission unit (230) can receive power from the gearbox (220). The power transmission unit (230) can provide power to the piston (240).

[0037] According to one embodiment, the power transmission unit (230) may be a screw shaft. In this case, the piston (240) may be screw-coupled with the screw shaft. In this case, when the screw shaft rotates, the screw coupling is connected or disconnected, and the piston (240) moves forward or backward. The shape, size, position, etc. of the power transmission unit (230) are not limited by the disclosure of the drawings.

[0038] The piston (240) moves by receiving power from the power transmission unit (230). When the piston (240) moves forward, the piston (240) presses the brake pad (250). The brake pad (250) presses the rotating wheel disc (260) to brake the vehicle.

[0039] The brake pads (250) may be a pair. A pair of brake pads (250) may be placed on both sides of the wheel disc (260). The wheel disc (260) is coupled to the wheel of the vehicle and rotates together with the wheel. When the piston (240) presses the brake pad (250), the brake pad (250) can press the wheel disc (260). When the brake pad (250) presses the wheel disc (260), the brake pad (250) is compressed and a braking force is generated. As the distance the piston (240) advances increases, the force with which the brake pad (250) presses the wheel disc (260) increases, and thus the braking force increases.

[0040] The sensor unit (110) may include a motor current sensor (not shown), a motor rotation angle sensor (not shown), a brake pedal sensor (not shown), a wheel speed sensor (not shown), etc.

[0041] According to one embodiment, the motor current sensor can measure the current flowing through the motor (210).

[0042] According to one embodiment, the motor rotation angle sensor can measure the rotation angle of the motor (210). The piston (240) moves forward or backward due to the rotation of the motor (210). That is, since the position of the piston (240) is determined by the rotation angle of the motor (210), the electric brake (1) can determine the position of the piston (240) using the motor rotation angle sensor.

[0043] According to one embodiment, the brake pedal sensor generates a brake pedal signal based on the amount of pressure applied to the brake pedal. The electric brake (1) can calculate a target braking force to be generated based on the signal from the brake pedal sensor. The target braking force refers to the braking force required for the electric brake (1) to exert.

[0044] According to one embodiment, a wheel speed sensor measures the wheel speed of a vehicle's wheel. The wheel speed sensor can transmit the measured wheel speed to a processor (130).

[0045] A first map (123) is stored in the memory (120). The first map (123) may be a force map representing the correlation between the position of the piston (240) and the braking force based on an initial state (= first state). Further details regarding the first map (123) will be described later.

[0046] The state of the electric brake (1) used in this specification is defined. The first state refers to the state of the electric brake (1) when driving and braking have not yet been performed. For example, the first state may be the state of the electric brake (1) when power is supplied to the vehicle by starting it. For example, the first state may be the state of the electric brake (1) when opening the door of a vehicle with the engine off.

[0047] The term "initial state" as used in this specification is used with the same meaning as the first state described above. When braking is performed while driving, the state of the electric brake (1) may change from the first state (=initial state) to another state. For example, the brake pad (250) may expand due to heat. For example, the brake pad (250) may contract due to a cold environment. For example, the brake pad (250) may wear out and its thickness may decrease.

[0048] In the following, the actual braking force refers to the braking force actually generated by the electric brake (1) according to the present disclosure. Since the electric brake (1) according to the present disclosure employs a force sensor-less system that does not include a force sensor, the electric brake (1) cannot directly measure the actual braking force. Therefore, the processor (130) of the electric brake (1) according to the present disclosure uses the position of a contact point, the distance traveled by the piston (240) from the home position, the position of the piston (240), the current of the motor (210), a force map, etc., to calculate the actual braking force value. The more accurately the actual braking force is calculated, the more precise the braking control becomes, and thus safer braking becomes possible.

[0049] The contact point refers to the position of the piston (240) when the brake pad (250) begins to contact the wheel disc (260) and braking force begins to be generated.

[0050] The home position refers to a position where the piston (240) is positioned when not braking. When not in a braking situation or when braking is finished, the piston (240) is set to return to the home position.

[0051] The processor (130) of the electric brake (1) according to the present disclosure can calculate an actual braking force value based on a plurality of braking data even when the first state (initial state) is not reached due to braking performed during driving. An explanation of the plurality of braking data and a specific method for calculating the actual braking force value will be described later.

[0052] FIG. 3 is a graph showing a first map according to one embodiment of the present disclosure.

[0053] FIG. 4 is a graph illustrating the correlation between the current and the braking force of a motor according to one embodiment of the present disclosure.

[0054] FIG. 5 is a drawing illustrating various braking force curves over time when the brake pedal is pressed in a first state according to one embodiment of the present disclosure.

[0055] The various braking force curves disclosed in FIG. 5 are merely examples, and the various braking force curves of the electric brake (1) of the present disclosure are not limited by the graph of FIG. 5. The shape of the graph may vary depending on the driver's habit of pressing the brake pedal, braking situation (e.g., sudden braking, complete braking), etc.

[0056] In FIG. 5, a graph is disclosed in which all of the braking data from the first area to the third area, which will be described later, are present, but there may also be a graph in which only some of the braking data from the first area to the third area are present.

[0057] For example, it is possible for only the first region braking data to exist. This is the case where the driver presses the brake pedal relatively slowly, and only the target braking force corresponding to the first region braking data is calculated. In this case, the second region braking data and the third region braking data are not generated, and only the first region braking data can be generated.

[0058] For example, it is possible for only the second-region braking data to exist. This is the case where the driver presses the brake pedal relatively quickly, and only the target braking force corresponding to the second-region braking data is calculated. In this case, the first-region braking data and the third-region braking data are not generated, and only the second-region braking data can be generated.

[0059] For example, it is possible for only third-region braking data to exist. This occurs when the driver presses the brake pedal relatively faster, and only the target braking force corresponding to the third-region braking data is calculated. In this case, the first-region braking data and the second-region braking data are not generated, and only the third-region braking data can be generated.

[0060] By the same principle, only the braking data of the first area and the braking data of the second area may exist. By the same principle, only the braking data of the first area and the braking data of the third area may exist. By the same principle, only the braking data of the second area and the braking data of the third area may exist. By the same principle, all of the braking data of the first area, the braking data of the second area, and the braking data of the third area may exist. As such, the presence or absence of the braking data of the first area through the third area has various possibilities.

[0061] With parallel reference to FIGS. 3 to 5, piston position-based estimated braking force and current-based estimated braking force, etc., will be explained.

[0062] Referring to FIG. 4, the current flowing through the motor (210) has a correlation proportional to the braking force. As the current flowing through the motor (210) increases and the piston (240) advances further, the force with which the brake pad (250) presses against the wheel disc (260) increases, thereby increasing the braking force. Thus, since the current of the motor (210) and the braking force have a correlation proportional to each other, the electric brake (1) of the present disclosure can estimate the braking force value by measuring the current value of the motor (210). The braking force value estimated by the processor (130) after the sensor unit (110) measures the current value of the motor (210) is defined as the current-based estimated braking force value.

[0063] Referring to Fig. 5, the experimental data obtained in the first state is represented as the first curve (cv1) and the second curve (cv2). The first curve (cv1) is a curve that simultaneously represents the target braking force curve, the actual braking force curve, and the piston position-based estimated braking force curve.

[0064] Specifically, the processor (130) calculates the target braking force based on the amount of pressure applied to the brake pedal. As the amount of pressure applied to the brake pedal changes over time, the target braking force calculated by the processor (130) also changes. The processor (130) changes the actual braking force according to the change in the target braking force. Although a discrepancy may occur between the target braking force value and the actual braking force value in very short time units, the present disclosure does not deal with time units short enough to cause a discrepancy. Therefore, in the present disclosure, the target braking force value is treated as having the same value as the actual braking force value. In addition, since FIG. 5 is a graph representing the first state (=initial state), the piston position-based estimated braking force value has the same value as the actual braking force value. As will be described later, this is because the piston position-based estimated braking force in the first state is almost identical to the actual braking force. That is, the first curve (cv1) disclosed in FIG. 5 is a curve that represents the target braking force curve, the actual braking force curve, and the piston position-based estimated braking force curve having the same value all at once. This is because the three curves are drawn overlapping anyway, so there is no need to represent each of them as a separate graph.

[0065] The second curve (cv2) is a current-based estimated braking force curve, and there is a gap (gap, g1) that is an error with the first curve (cv1). The current-based estimated braking force has an error with the actual braking force regardless of the state of the electric brake (1). That is, an error can occur even in the first state. That is, an error can occur even when it is not in the first state. If it were an ideal situation where the current of the motor (210) could be accurately measured, the possibility of an error occurring would be low, and unlike in FIG. 5, the gap (g1) would be small or non-existent, so the second curve (cv2) should appear to be the same as or nearly identical to the first curve (cv1). In actual situations, because it is difficult to accurately measure the current value flowing through the motor (210), a gap (g1) corresponding to the error occurs.

[0066] Referring to FIG. 3, the position of the piston (240) and the magnitude of the braking force of the electric brake (1) have a proportional relationship. That is, the greater the distance the piston (240) moves toward the brake pad (250), the greater the braking force generated.

[0067] When the positions of the piston (240) measured during braking are input into the first map (123, map), which is a pre-stored force map, the output braking force values ​​can be defined as piston position-based estimated braking force values. Here, the first map (123) is a map in which the braking force values ​​of the electric brake corresponding to the position of the piston (240) are indexed when in the initial state. When in the initial state (= first state), the electric brake (1) can perform calibration to generate the first map (123). That is, the first map (123) reflects the correlation between the position of the piston (240) and the braking force values ​​collected when performing calibration in the initial state.

[0068] By driving the motor (210), the piston (240) pushes the brake pad (250) toward the wheel disc (260), and when the brake pad (250) comes into contact with the wheel disc (260), a braking force is generated. The position of the piston (240) at the time when the brake pad (250) begins to come into contact with the wheel disc (260) is called the contact point. Since the braking force of the electric brake (1) increases in proportion to the distance the piston (240) has moved from the contact point, the braking force generated can be determined by detecting the contact point and measuring how far the piston (240) has moved from the contact point. That is, the first map (123) is a data representation of the correlation between the position of the piston (240) in the initial state and the braking force generated. When a contact point is detected, the processor (130) may set a home position by considering the drag phenomenon, rattle noise, braking responsiveness, etc., between the brake pad (250) and the wheel disc (260). The closer the home position is to the wheel disc (260), the more the braking responsiveness is improved. The further the home position is from the wheel disc (260), the more effectively the drag phenomenon is prevented.

[0070] Piston position (=distance the piston has moved from the home position) Piston position-based estimated braking force value 0 (Home Position) 0 0.016 4588 0.709 7216 0.789 9961 0.829 11468 0.876 13098 0.923 14641 0.97 16295 1.017 17896 1.063 19683

[0072] Table 1 is an example of a table showing the correlation between the position of the piston (240) and the braking force according to the first map (123). The processor (130) can input the positions of the piston (240) measured during actual braking into the first map (123) that has been stored, and output the values ​​output according to the input as piston position-based estimated braking force values. For example, if the position of the piston (240) is measured as 1.063 at a specific braking point during actual driving, the processor (130) can input 1.063 into the first map (123) and output the piston position-based estimated braking force value at that specific point as 19683.

[0073] Since the first map (123) is a map that reflects the relationship between the position of the piston (240) and the braking force when the electric brake (1) is in an initial state, the piston position-based estimated braking force value is equal to or nearly identical to the actual braking force value when the electric brake (1) is in an initial state. That is, when it is in an initial state (= first state), the electric brake (1) can determine the actual braking force value using the first map (123) (Fig. 3). On the other hand, when braking is performed multiple times and the state of the electric brake (1) changes so that it is not in an initial state, the piston position-based estimated braking force value output by the first map (123) is not the same as the actual braking force value. That is, when the state of the electric brake (1) is not in an initial state, there is a limitation in that the actual braking force value cannot be accurately derived using only the first map (123). For example, when the brake pad (250) is worn out and not in its initial state, if the position of the piston (240) is 1.063, the actual braking force value will be smaller than the piston position-based estimated braking force value of 19683 derived by inputting the position of the piston (240) of 1.063 into Table 1. This is because the force exerted by the brake pad (250) on the wheel disc (260) decreases by the thickness of the brake pad (250) that has worn down.

[0074] Referring to FIG. 4, the current of the motor (210) and the magnitude of the braking force of the electric brake (1) have a proportional relationship. However, the proportional relationship between the current of the motor (210) and the magnitude of the braking force is established only when the motor (210) rotates forward and the piston (240) moves forward, or when it is in an apply-holding state. The apply-holding state refers to the case where the motor (210) stops in a state of forward rotation and maintains a stopped state.

[0075] When the motor (210) rotates in reverse and the piston moves backward, the current of the motor (210) does not have a correlation proportional to the magnitude of the braking force. Additionally, it does not have a proportional correlation when in a release-holding state. A release-holding state means that the motor (210) stops while rotating in reverse and maintains a stopped state.

[0076] By utilizing the principle that the current of the motor (210) and the magnitude of the braking force are proportional to each other, the processor (130) can calculate a current-based estimated braking force value corresponding to the current value of the motor (210) measured during braking. However, since the current-based estimated braking force value is an estimate of the braking force value based on the measured current value, an error occurs with the actual braking force value. This is because it is difficult to accurately measure the current value of the motor (210). While the piston position-based estimated braking force value described earlier accurately reflects the actual braking force value in the initial state (first state), the current-based estimated braking force value does not accurately reflect the actual braking force value regardless of the state of the vehicle. In Figure 5, which shows the experimental results in the first state, it can be seen that the second curve (cv2) has a gap (g1) with the first curve (cv1).

[0077] The reason an error such as a gap (g1) occurs in the current-based estimated braking force value is that, unlike the calibration situation where the current of the motor (210) is stably applied, in the actual braking situation, the current value of the motor (210) changes rapidly and noise is generated, making it difficult to accurately measure the current. For example, if the RPM of the motor (210) changes rapidly in the actual braking situation, the variability of the current is large, making it difficult to accurately measure the current value of the motor (210). As such, the current-based estimated braking force value has limitations in that it is not identical to the actual braking force in various situations.

[0078] FIG. 6 is a drawing illustrating a first brake pad and a second brake pad when a piston according to one embodiment of the present disclosure is positioned in a preset home position.

[0079] Referring to FIG. 6, the first brake pad (250A) refers to the brake pad when in the first state. The second brake pad (250B) refers to the brake pad when not in the first state. For example, the first brake pad (250A) may wear out and become the second brake pad (250B). The thickness of the first brake pad (250A) is thicker than that of the second brake pad (250B) by the wear thickness (th). Both of the two pistons (240) disclosed in FIG. 6 are positioned in a pre-set home position.

[0080] As explained above, to determine the actual braking force value in the first state, the processor (130) can derive the piston position-based estimated braking force value using the measured position of the piston (240) and the first map (123). This is because in the first state, the actual braking force value is the same as the piston position-based estimated braking force value.

[0081] However, when the brake pad (250) is worn out and not in the first state, the piston position-based estimated braking force value according to the first map (123) is not the same as the actual braking force value. Specifically, in FIG. 6, the first brake pad (250A) comes into contact with the wheel disc (260) when it advances by a first distance (m1). On the other hand, the second brake pad (250B) comes into contact with the wheel disc (260) only when it advances by a second distance (m2). Here, the second distance (m2) is greater than the first distance (m1) by the wear thickness (th).

[0082] Assuming that the piston (240) moves more than a first distance (m1) and less than a second distance (m2) from the home position, the first brake pad (250A) presses the wheel disc (260) to generate braking force, while the second brake pad (250B) does not come into contact with the wheel disc (260) and therefore does not generate braking force. That is, in order for braking force to be generated when the brake pad (250) is worn out (i.e., not in the first state), the piston (240) must advance further than in the first state. Thus, the actual braking force value generated differs between the first state and the first state, even if the piston (240) moves the same distance from the preset home position.

[0083] The first map (123) is a map generated when in the first state. Therefore, when the electric brake (1) is in the first state because no wear occurs, such as with the first brake pad (250A) of FIG. 6, the piston position-based estimated braking force value output using the first map (123) can be treated as the same as the actual braking force value.

[0084] However, as in the second brake pad (250B) of FIG. 6, when the thickness changes due to wear and is not in the first state, the piston position-based estimated braking force value output using the first map (123) is different from the actual braking force value. This is because the first map (123) reflects the first state in which there is no wear of the brake pad (250) due to braking.

[0085] FIG. 7 is a drawing illustrating a case where a previously set home position is changed to a new home position according to one embodiment of the present disclosure.

[0086] Referring to FIG. 7, it is explained that when the processor (130) sets a new home position considering the wear of the brake pad, the processor (130) can calculate the actual braking force using the first map (123). When the home position is set a new home position, the piston position-based estimated braking force value output from the first map (123) can be treated as the same as the actual braking force value.

[0087] FIG. 7 shows that the processor (130) has set a new home position of the piston (240) by advancing from the preset home position by a wear thickness (th). When the piston (240) is in the preset home position, the second brake pad (250B) and the wheel disc (260) are separated from each other by a second distance (m2). When the piston (240) is in the new home position, the second brake pad (250B) and the wheel disc (260) are separated from each other by a first distance (m1). That is, when the home position is changed by the wear thickness (th) of the second brake pad (250B), the second brake pad (250B) can move by the first distance (m1) and come into contact with the wheel disc (260). This is the same as the first brake pad (250A) of FIG. 6 moving by a first distance (m1) to come into contact with the wheel disc (260).

[0088] In this way, even when not in the first state, if the processor (130) changes the pre-set home position to a new home position by considering the worn thickness of the brake pad (250), the processor (130) can determine that the piston position-based estimated braking force value output by inputting the position of the piston (240) into the first map (123) is the same as the actual braking force value. For example, in the case of FIG. 7, although it is not in the first state (=initial state), the home position is newly changed, and the gap between the second brake pad (250B) and the wheel disc (260) is changed from m2 to m1. In this way, because the gap between the brake pad (250B) and the wheel disc (260) is adjusted to m1, which is the same as in the first state, by changing the home position considering the wear of the brake pad, even when not in the first state, the piston position-based estimated braking force value output by inputting the measured position of the piston (240) into the first map (123) can be treated as the same as the actual braking force value. This is because the piston position-based estimated braking force value is a value output based on how far the piston (240) has advanced from the home position. That is, if the gap between the brake pad (250) and the wheel disc (260) changes due to the wear of the brake pad (250), by adjusting the gap between the brake pad (250) and the wheel disc (260) by setting a new home position, the first map (123) can be applied even when not in the first state, and the actual braking force value can be determined.

[0089] Below, a specific method for changing a previously set home position to a new home position is described.

[0090] FIG. 8 is a flowchart illustrating a control method for an electric brake according to one embodiment of the present disclosure.

[0091] FIG. 9 is a flowchart showing one example of the detailed process of S830 of FIG. 8.

[0092] FIG. 10 is a graph illustrating data of a first map according to one embodiment of the present disclosure, and is a diagram for explaining a method of calculating each difference value of a plurality of difference values ​​using the graph of the first map data.

[0093] When the electric brake (1) of the present disclosure is not in the first state, the processor (130) cannot determine the actual braking force using the first map (123) unless the home position is changed. As previously explained, this is because the piston position-based estimated braking force value output by inputting the measured position of the piston (240) into the first map (123) differs from the actual braking force value. The electric brake (1) can change the home position anew so that the piston position-based estimated braking force value becomes identical to the actual braking force value. That is, the processor (130) changes the home position anew so that the actual braking force can be calculated using the first map (123) even when the brake pad (250) is worn out and is not in the first state.

[0094] Referring to FIGS. 8 to 10, the electric brake (1) according to the present disclosure can perform processes S810 to S850 and S910 to S930 using a braking force generating unit (100), a sensor unit (110), a memory (120), a processor (130), etc., to set a new home position and accurately calculate an actual braking force value based on the distance the piston (240) has moved from the new home position. Each process disclosed in FIGS. 8 and 9 will be described.

[0095] In the process of S810, the electric brake (1) measures the current of the motor (210) and the position of the piston (240) in real time while performing braking using the sensor unit (110). According to one embodiment, the processor (130) may use only a portion of the current of the motor (210) measured by the sensor unit (110) as data, and may not use the remainder by determining it as noise. For example, the processor (130) may use the current value of the motor (210) measured when the motor (210) rotates in the forward direction and the current value of the motor (210) measured when it is in a engaged-holding state as data. For example, the processor (130) may determine the current value of the motor (210) measured when the motor (210) rotates in the reverse direction and the current value of the motor (210) measured when it is in a released-holding state as noise.

[0096] In the S820 process, the electric brake (1) generates multiple braking data corresponding to the measured current of the motor (210) and the measured position of the piston (240) using the processor (130).

[0097] Each of the plurality of braking data may include a target braking force value, a current-based estimated braking force value, etc. Each of the plurality of braking data may be divided into at least one region. Specifically, as shown in Table 2 below, it may be divided into one of the first region braking data to the third region braking data depending on the magnitude of the target braking force. For example, braking data in which the magnitude of the target braking force is greater than 0 N and less than or equal to 8,000 N may be classified as first region braking data. For example, braking data in which the magnitude of the target braking force is greater than 8,000 N and less than or equal to 20,000 N may be classified as second region braking data. For example, braking data in which the magnitude of the target braking force is greater than 20,000 N may be classified as third region braking data. Table 2 shows a portion of the braking data corresponding to the graph in FIG. 5 for the purpose of explanation.

[0098] As such, the reason for dividing multiple braking data into one or more regions is that the magnitude of the error between the target braking force and the current-based estimated braking force value varies depending on the magnitude of the target braking force. That is, the size and trend of the gap (g1) vary depending on the magnitude of the target braking force. Compared to the braking data of the first region and the braking data of the third region, the braking data of the second region tends to have a relatively smaller gap (g1).

[0100] Braking data collected in the initial state Area separation Target braking force value Current-based estimated braking force value Area 1 braking data 2,500 1,274 5,000 2,336 7,500 4,824 Area 2 braking data 12,000 10,678 14,000 12,984 18,000 17,219 Area 3 braking data 24,000 22,147 28,000 28,927 32,000 33,427

[0102] Table 2 is merely an example for illustrative purposes, and the multiple braking data that can be generated by the electric brake (1) of the present disclosure are not limited by Table 2. There are various braking methods that can be performed by the electric brake (1). For example, the electric brake (1) can perform braking that reduces the speed of the vehicle at a constant deceleration rate. For example, the electric brake (1) can perform emergency braking that rapidly reduces the speed of the vehicle at a very large deceleration rate. For example, the electric brake (1) can perform braking using an ABS (Anti-lock Braking System) to prevent wheel lock on wet roads. The multiple braking data that can be generated by the electric brake (1) of the present disclosure are not limited to the above examples, and the multiple braking data will be generated differently depending on the various braking methods that can actually be performed.

[0103] In process S830, the processor (130) of the electric brake (1) determines a correction value for changing a preset home position based on a plurality of braking data. The specific process for determining the correction value is explained with parallel reference to FIGS. 9 and FIGS. 10.

[0104] In the S910 process, the processor (130) of the electric brake (1) inputs the current-based estimated braking force value (①) of each of the plurality of braking data into the first map (123) that has been stored, and outputs the current-based piston position (②) of each of the plurality of braking data (Fig. 10).

[0105] In the process of S920, the processor (130) of the electric brake (1) calculates a plurality of difference values ​​and calculates an average value among the calculated plurality of difference values. Here, each difference value of the plurality of difference values ​​refers to the difference value (④) between the measured piston position (③) of each of the plurality of braking data and the current-based piston position (②) of each of the plurality of braking data (Fig. 10). That is, the average value is the average value of each difference value calculated from each of the braking data.

[0106] In the process of S930, the processor (130) of the electric brake (1) determines the value obtained by multiplying the average value by a correction factor as the correction value. The correction factor is a coefficient that controls the magnitude of the correction value. The correction factor has a value of 0 or greater and 1 or less. Since the correction factor is 0 or greater and 1 or less, the processor (130) determines the correction value as a value less than or equal to the average value.

[0107] The processor (130) may determine a relatively large correction factor to change the position of the home position significantly at once. The processor (130) may also determine a relatively small correction factor to change the position of the home position in small increments multiple times, rather than changing the position significantly at once.

[0108] When the correction factor is set relatively large, the frequency of home position changes is relatively low, so the likelihood of home position change failure or error is relatively lower. When the correction factor is set relatively small, home position changes frequently, so abrupt changes do not occur, preventing a braking inconsistency.

[0109] Below, the method by which the processor (130) determines the correction factor is further explained.

[0110] According to one embodiment, the processor (130) of the electric brake (1) can determine a correction factor with a different value depending on the presence and number of each of the first area braking data, the second area braking data, and the third area braking data.

[0111] Referring to Table 2 and Figure 5, the current-based-estimated braking force value of the second region braking data approaches the target braking force value relatively more consistently than the current-based-estimated braking force value of the first region braking data and the current-based-estimated braking force value of the third region braking data. That is, the current-based-estimated braking force value of the second region braking data shows a trend that is relatively more similar to the target braking force value. In other words, the gap (g1) between the first curve (cv1) and the second curve (cv2) tends to be relatively smaller in the second region braking data than in the first region braking data and the third region braking data. That is, the second region braking data is relatively more reliable, while the first region braking data and the third region braking data are relatively less reliable.

[0112] Multiple braking data collected by the electric brake (1) are collected differently depending on the braking situation, such as the driver's braking habits, vehicle speed, road conditions, and the magnitude of the target braking force. That is, the presence and number of each of the first-area braking data to third-area braking data that can be collected while driving vary depending on the driving and braking situation.

[0113] The larger the correction factor, the larger the correction value. The processor (130) of the electric brake (1) can determine the correction factor to a relatively larger value as more reliable second-region braking data is collected. The processor (130) can determine the correction factor to a relatively smaller value as fewer reliable second-region braking data are collected. For example, if the multiple braking data collected by the electric brake (1) includes one or more of the first-region braking data and the third-region braking data, the processor (130) can determine that the correction factor has a value of 1 or less. For example, if the multiple braking data collected by the electric brake (1) includes the first-region braking data, the second-region braking data, and the third-region braking data, the processor (130) can determine that the correction factor has a value of 1.

[0114] Meanwhile, as the number of multiple braking data decreases, the processor (130) can determine the correction factor to a smaller value and thus determine the correction value to be smaller. For example, unlike the above description, even if the multiple braking data collected by the electric brake (1) includes the first area braking data, the second area braking data, and the third area braking data, if the number of collected multiple braking data itself is not greater than or equal to a threshold number, the processor (130) can determine that the correction factor has a value of 1 or less.

[0115] In this way, the processor (130) of the electric brake (1) of the present disclosure can adjust the size of the correction factor to prevent overcorrection that may occur when setting a new home position.

[0116] When the correction value is determined by the S830 process, the electric brake (1) performs the S840 process.

[0117] In the process of S840, the electric brake (1) sets a new home position by changing the pre-set home position by a correction value. As previously explained, the correction value is determined to be a different value depending on the average value and the correction coefficient. If the correction value is determined to be +0.042 mm, the processor (130) sets a position that is advanced by +0.042 mm from the pre-set home position as the new home position.

[0118] In the S850 process, the electric brake (1) calculates an actual braking force value based on the distance the piston (240) has moved from the new home position. Since the new home position is set considering the worn thickness of the brake pad (250), even if the brake pad is worn and not in the first state, the piston position-based estimated braking force value output by inputting the position of the piston (240) into the first map (123) can be treated as the same as the actual braking force value.

[0119] Thus, the electric brake (1) according to the present disclosure has the advantage of being able to calculate the actual braking force value without a force sensor by performing the S810 to S850 process.

[0120] In addition, the electric brake (1) according to the present disclosure has the advantage of being able to accurately calculate the actual braking force value by using the home position change and the first map (123) even when the brake pad (250) is worn out by braking performed during driving and is not in the first state.

[0121] Conventional electric brakes have a limitation in that, when not in the first state, the braking force can only be accurately calculated after the vehicle is stopped and recalibrated to update the state of the electric brake. The electric brake (1) according to the present disclosure has the effect of being able to calculate the actual braking force value without recalibrating, while continuing to drive without stopping when not in the first state.

[0122] In addition, the electric brake (1) according to the present disclosure can set a new home position in real time by taking into account the wear even when wear of the brake pad (250) occurs, and can calculate an accurate actual braking force value.

[0123] Alternatively, the electric brake (1) according to the present disclosure may not set a new home position in real time, but may periodically set a new home position at predetermined time intervals.

[0124] When a new home position is set in real-time, the position is changed more frequently than when it is set periodically, allowing for the calculation of a more accurate actual braking force value. Furthermore, since the magnitude of the correction value determined each time a new home position is set is small, the driver does not experience any unnatural braking sensation.

[0125] When the home position is overcorrected, there is a risk that the driver will feel a braking abnormality. However, when the home position is changed in real time, the home position changes frequently, so the magnitude of the correction value of the home position that changes at once is small, and thus the home position is not overcorrected, so the driver will not feel a braking abnormality.

[0126] When setting the home position periodically, the home position is changed at a relatively lower frequency than when setting a new home position in real time, so the likelihood of system errors due to frequent home position changes and failure of home position changes is relatively lower.

[0127] The case of periodically setting a new home position at preset time intervals is described. The processor (130) can determine a correction factor to a smaller value as the preset time interval becomes smaller. For example, when setting a new home position in real time, the correction factor can be determined to a smaller value than when setting a new home position at a longer time interval than real time.

[0128] The following describes the correction value and the wear thickness of the brake pad (250). According to one embodiment, when determining a correction value for setting a new home position, the processor (130) can adjust the correction factor so that the correction value is determined to be less than or equal to the wear thickness of the brake pad (250). For example, the thickness of the second brake pad (250B) in FIG. 6 is thinner than the first brake pad (250A) by the wear thickness (th). In this case, the processor (130) can adjust the correction factor so that the correction value is determined to be less than or equal to the wear thickness (th).

[0129] When the correction value is determined to be the same as the wear thickness (th), the electric brake (1) changes the home position by the determined correction value, and the processor (130) can determine that the piston position-based-estimated braking force value output by inputting the position of the piston (240) into the first map (123) is the same as the actual braking force value.

[0130] When the correction value is determined to be smaller than the wear thickness (th), the electric brake (1) changes the groove position by the determined correction value, and after the groove position is changed, the process S810 to S850 of FIG. 8 is performed again to change the groove position again. That is, when the correction value is determined to be smaller than the wear thickness (th), the electric brake (1) can change the groove position at least one more time. When the correction value is determined to be smaller than the wear thickness (th), the groove position is changed more frequently than when the correction value is determined to be equal to the wear thickness (th), so there is an advantage that the possibility of the groove position being overcorrected is low.

[0131] Each component of the device or method according to the present disclosure may be implemented in hardware or software, or in a combination of hardware and software. Additionally, the function of each component may be implemented in software, and a microprocessor may be implemented to execute the function of the software corresponding to each component.

[0132] Various embodiments of the systems and techniques described herein may be realized as digital electronic circuits, integrated circuits, field programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include being implemented as one or more computer programs executable on a programmable system. A programmable system comprises a storage system, at least one input device, and at least one programmable processor (which may be a special-purpose processor or a general-purpose processor) coupled to receive data and instructions from and transmit data and instructions to at least one output device. Computer programs (which are also known as programs, software, software applications, or code) include instructions for the programmable processor and are stored on a "computer-readable recording medium."

[0133] Computer-readable recording media include all types of recording devices in which data that can be read by a computer system is stored. Such computer-readable recording media may be non-volatile or non-transitory media such as ROM, CD-ROM, magnetic tape, floppy disk, memory card, hard disk, magneto-optical disk, and storage device, and may also include transitory media such as data transmission media. Additionally, computer-readable recording media may be distributed across networked computer systems, and computer-readable code may be stored and executed in a distributed manner.

[0134] Although the flowcharts and timing diagrams in this specification describe each process as being executed sequentially, this is merely an illustrative explanation of the technical concept of one embodiment of the present disclosure. In other words, a person skilled in the art to which one embodiment of the present disclosure belongs may modify and adapt the flowcharts and timing diagrams in various ways, such as changing the order described in the flowcharts and timing diagrams or executing one or more of the processes in parallel, without departing from the essential characteristics of one embodiment of the present disclosure; therefore, the flowcharts and timing diagrams are not limited to a chronological order.

[0135] The above description is merely an illustrative explanation of the technical concept of the present embodiment, and a person skilled in the art to which the present embodiment belongs would be able to make various modifications and variations within the scope of the essential characteristics of the present embodiment. Accordingly, the present embodiments are intended to explain, not limit, the technical concept of the present embodiment, and the scope of the technical concept of the present embodiment is not limited by these embodiments. The scope of protection of the present embodiment shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present embodiment. Explanation of the symbols

[0136] 1: Electric brake 100: Braking force generating unit 110: Sensor section 120: Memory 123: Map 1 130: Processor 210: Motor 220: Gearbox 221: Multiple Gears 230: Power transmission unit 240: Piston 250: Brake pads 250A: 1st brake pad 250B: Second brake pad 260: Wheel disc 270: Rotation axis cv1: First curve cv2: second curve

Claims

Claim 1 A control method for an electric brake comprising a piston that presses a brake pad toward a wheel disc by driving a motor, the method comprising: generating a plurality of braking data corresponding to the current of the motor measured during braking and the position of the measured piston; determining a correction value for changing a preset home position based on the plurality of braking data; changing the preset home position by the correction value to set a new home position; and calculating an actual braking force value based on the distance the piston has moved from the new home position, wherein each of the plurality of braking data includes a target braking force value and a current-based estimated braking force value, and each of the plurality of braking data is classified into one of a first area braking data, a second area braking data, and a third area braking data according to the magnitude of the target braking force value. Claim 2 A method for controlling an electric brake according to claim 1, wherein the process of determining a correction value for changing a preset home position based on the plurality of braking data comprises: inputting a current-based estimated braking force value of each of the plurality of braking data into a preset first map to output a current-based piston position of each of the plurality of braking data; calculating a plurality of difference values ​​and calculating an average value between the plurality of difference values; and determining a value obtained by multiplying the average value by a correction coefficient as the correction value, wherein each of the plurality of difference values ​​represents a difference value between the measured position of the piston of each of the plurality of braking data and the current-based piston position of each of the plurality of braking data. Claim 3 A control method for an electric brake according to claim 2, wherein the correction factor is determined to a different value depending on the presence or absence of each of the first area braking data, the second area braking data, and the third area braking data. Claim 4 A control method for an electric brake according to claim 3, wherein the correction factor has a value of 1 or less when the plurality of braking data includes one or more of the first region braking data and the third region braking data. Claim 5 A control method for an electric brake according to claim 4, wherein the correction factor has a value of 1 when the plurality of braking data includes all of the first area braking data, the second area braking data, and the third area braking data. Claim 6 A method for controlling an electric brake according to claim 3, wherein the process of changing the previously set home position by the correction value to set a new home position is a process that is performed periodically at previously set time intervals. Claim 7 A control method for an electric brake according to claim 6, wherein the correction factor is determined to be a smaller value as the preset time interval becomes smaller. Claim 8 An electric brake device according to claim 3, wherein the correction factor is adjusted so that the correction value is determined to be less than or equal to the wear thickness of the brake pad. Claim 9 An electric brake comprising a piston that presses a brake pad toward a wheel disc by driving a motor, the electric brake comprising: a sensor unit that measures the current of the motor and measures the position of the piston; and a processor that generates a plurality of braking data corresponding to the current of the motor measured during braking and corresponding to the measured position of the piston, determines a correction value for changing a preset home position based on the plurality of braking data, changes the preset home position by the correction value to set a new home position, and calculates an actual braking force value based on the distance the piston has moved from the new home position, wherein each of the plurality of braking data includes a target braking force value and a current-based estimated braking force value, and each of the plurality of braking data is classified into one of a first area braking data, a second area braking data, and a third area braking data according to the magnitude of the target braking force value. Claim 10 In claim 9, in order to determine a correction value for changing a preset home position based on the plurality of braking data, the processor inputs the current-based-estimated braking force value of each of the plurality of braking data into a preset first map to output the current-based-piston position of each of the plurality of braking data, calculates a plurality of difference values, calculates an average value between the plurality of difference values, and determines the value obtained by multiplying the average value by a correction coefficient as the correction value, wherein each of the plurality of difference values ​​represents the difference value between the measured position of the piston of each of the plurality of braking data and the current-based-piston position of each of the plurality of braking data, and the correction coefficient is determined to be a different value depending on the presence or absence of each of the first area braking data, the second area braking data, and the third area braking data.

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