Electromechanical brake

Abstract

An electromechanical brake is disclosed, configured such that a piston pulls a brake pad toward a wheel disc via a drive motor. The electromechanical brake includes: a hysteresis data storage unit storing rising interval function data over a rising interval and falling interval function data over a falling interval, wherein the braking force increases as the piston moves toward the wheel disc and decreases as the piston moves away from the wheel disc; a position detection unit detecting the position of the piston; a calculation unit calculating the differential value of the detected piston position relative to time; a past state data storage unit storing data over a previous interval corresponding to the previous piston position; and a braking force calculation unit calculating the braking force based on the differential value of the piston position and the data over the previous interval.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2021-0119721, filed on September 8, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to an electromechanical brake. Background Technology

[0004] The content described in this section is only to provide background information for this disclosure and does not constitute prior art.

[0005] Electro-mechanical brakes (EMBs) are becoming increasingly common. Originally developed as electronic parking brakes (EPBs), their applications are expanding to replace traditional hydraulic brakes as main brakes. An EMB is a device that mounts an electric motor-driven actuator on the brake caliper, allowing direct braking of the vehicle using the motor's driving force without the need for a medium such as brake fluid. While EMBs share a similar mechanism with EPBs, they are primarily used for main braking, thus requiring higher braking response and operational durability. Furthermore, compared to hydraulic brakes, electro-mechanical brakes can be structurally simpler and offer faster and more precise control in braking response, thereby improving braking stability.

[0006] An EMB equipped with a load sensor can accurately measure clamping force. However, equipping an EMB with a load sensor complicates the design of the sensor mounting components and increases manufacturing costs. Furthermore, the size of the EMB may inevitably increase due to sensor mounting.

[0007] To prevent increased manufacturing costs and size of the EMB, a current sensor can be used instead of a load sensor to estimate the clamping force. The EMB can be designed so that the current sensor measures the current flowing through the motor that generates the braking force, and the clamping force is estimated based on the measured current value. However, the problem with estimating the clamping force by measuring the current flowing through the motor is that the estimation accuracy deteriorates compared to using a load sensor due to measurement noise from the current sensor.

[0008] Figure 11A , 11B Figures 11 and 11C are schematic diagrams illustrating the configuration of a conventional electromechanical brake.

[0009] refer to Figure 11A, 11B Like 11C, the EMB includes a wheel 11_c, a pair of brake pads 11_b disposed on both sides of the wheel 11_c, and a piston 11_a configured to press the brake pads 11_b toward the wheel 11_c. When the piston 11_a moves toward the wheel 11_c, the braking force increases. Even if the relative positions of the piston 11_a and the brake pads 11_b are the same, the braking force has different values ​​depending on the movement path of the piston 11_a. That is, the braking force for the position of the piston 11_a has a hysteresis characteristic. Therefore, the braking force of the EMB cannot be accurately estimated without considering the movement path of the piston 11_a. Summary of the Invention

[0010] In view of the above, the electromechanical brake according to the embodiment can estimate the clamping force with high accuracy by estimating the clamping force based on the position of the piston that detects a specific current value.

[0011] According to the embodiment of the electromechanical brake, by taking into account the hysteresis characteristics of the braking force relative to the position of the piston, the braking force can be calculated more accurately so that the calculated braking force can be used to control the electromechanical brake.

[0012] The problems to be solved by this disclosure are not limited to those described above, and other unmentioned problems will be clearly understood by those skilled in the art through the following description.

[0013] According to at least one embodiment, this disclosure provides an electromechanical brake configured such that a piston pulls a brake pad toward a wheel disc via a drive motor. The electromechanical brake includes: a hysteresis data storage unit storing rising interval function data over a rising interval, wherein the braking force increases as the piston moves toward the wheel disc, and falling interval function data over a falling interval, wherein the braking force decreases as the piston moves away from the wheel disc; a position detection unit detecting the position of the piston; a calculation unit calculating the differential value of the piston's position relative to time; a past state data storage unit storing data over a previous interval corresponding to a previous piston position; and a braking force calculation unit calculating the braking force based on the differential value of the piston position and the data over the previous interval.

[0014] According to an embodiment, the advantage of the electromechanical brake is that it can estimate the clamping force with high accuracy by estimating the position of the piston based on the detected specific current value.

[0015] According to the embodiments, the advantage of the electromechanical brake is that it can calculate the braking force more accurately by taking into account the hysteresis characteristics of the braking force relative to the position of the piston. Attached Figure Description

[0016] Figure 1This is a schematic diagram illustrating the configuration of an electromechanical brake according to an embodiment of the present disclosure.

[0017] Figure 2A , 2B Figures 2C and 2C are diagrams illustrating the driving state of an electromechanical brake according to an embodiment of the present disclosure.

[0018] Figure 3 It is a curve of current measured based on the operating distance of the brake pad.

[0019] Figure 4 This is a graph illustrating the method for estimating the location of the contact point.

[0020] Figure 5 This is a graph showing the motor control time used to detect the contact point.

[0021] Figure 6 It is a graph showing the magnitude of the braking force based on the piston's position and direction of movement.

[0022] Figure 7 It is a graph illustrating the process of determining the function followed by the electromechanical brake according to an embodiment of the present disclosure to calculate the braking force.

[0023] Figure 8A and 8B This is a graph illustrating the transition interval function according to an embodiment of the present disclosure.

[0024] Figure 9 This is a graph showing the rising interval function, the falling interval function, and the transition interval function according to embodiments of the present disclosure.

[0025] Figure 10 It is a graph showing the change in braking force function with respect to piston position as the brake pads wear.

[0026] Figure 11A , Figure 11B and Figure 11C This is a schematic diagram showing the configuration of a conventional electromechanical brake. Detailed Implementation

[0027] Some exemplary embodiments of this disclosure are described below with reference to the accompanying drawings. In the following description, similar reference numerals preferably denote similar elements, even though these elements are shown in different drawings. Furthermore, in the following description of some embodiments, detailed descriptions of known functions and configurations incorporated herein will be omitted for the purpose of clarity and brevity.

[0028] Furthermore, the alphanumeric codes in part numbering, such as first, second, i), ii), a), b), etc., are used only to distinguish one part from another, and do not imply or suggest the material, order, or sequence of the parts. Throughout the specification, when a part is described as "comprising" or "containing" a part, it means that other parts are also included, without excluding other parts, unless specifically described to the contrary.

[0029] Figure 1 This is a schematic diagram illustrating the configuration of an electromechanical brake according to an embodiment of the present disclosure.

[0030] refer to Figure 1 According to embodiments of the present disclosure, the electromechanical brake includes all or some of the following: a wheel disc 150, a brake pad 140, a piston 131, a motor 120, a current detection unit 180, a position detection unit 170, and a control unit 160.

[0031] A wheel disc 150 is connected to the vehicle's wheels. The wheel disc 150 rotates together with the vehicle's wheels. The vehicle can be braked by limiting the rotation of the wheel disc 150. A brake pad 140 is disposed on one side of the wheel disc 150. A piston 131 is configured to push the brake pad 140 against the wheel disc 150 via a drive motor 120. When the piston 131 presses the brake pad 140 against the wheel disc 150, friction is generated between the brake pad 140 and the wheel disc 150. Due to the friction generated between the brake pad 140 and the wheel disc 150, the rotation of the wheel disc 150 is limited. The motor 120 provides power to the piston 131.

[0032] The process by which piston 131 receives power from motor 120 and is then driven will be described. Driven by motor 120, drive gear 134 rotates together with the rotating shaft 121 of motor 120. Drive gear 134 meshes with driven gear 133. When drive gear 134 rotates, driven gear 133 also rotates. Driven gear 133 is connected to helical shaft 132. Helical shaft 132 rotates with the rotation of driven gear 133. Threads are formed on the outer circumference of helical shaft 132. Helical grooves with a shape corresponding to the thread shape of helical shaft 132 are formed on the inner circumference of piston 131. If helical shaft 132 rotates together with driven gear 133, piston 131 moves linearly, simultaneously being fastened to or released from helical shaft 132. If piston 131 moves linearly toward wheel 150, brake pad 140 is pushed toward wheel 150 by piston 131.

[0033] The position detection unit 170 detects the position of piston 131. The position of piston 131 represents the distance from the lowest point of piston 131's stroke to piston 131. Here, the lowest point of stroke refers to the position of brake pad 140 when the distance between brake pad 140 and wheel disc 150 is at its maximum.

[0034] The position detection unit 170 may include an angle sensor. The angle sensor measures the angular displacement of the rotation shaft 121 of the motor 120. The position detection unit 170 can use the angular displacement of the rotation shaft 121 sensed by the angle sensor to calculate the linear travel distance of the piston 131. The linear travel distance of the piston 131, depending on the rotation angle of the motor 120, can vary depending on the design of the electromechanical brake. For example, the electromechanical brake can be designed such that when the rotation shaft 121 of the motor 120 rotates 360 degrees, the linear travel distance of the piston 131 is 1 mm.

[0035] Figure 2A , 2B Figures 2C and 2C are diagrams illustrating the driving state of an electromechanical brake according to an embodiment of the present disclosure.

[0036] refer to Figure 2A When the brake pad 140 is spaced apart from the wheel disc 150, no braking force is generated. Here, braking force is the force used to brake the vehicle. Figure 2B As shown, when piston 131 pushes brake pad 140 to contact wheel disc 150, friction is generated between brake pad 140 and wheel disc 150. This friction acts as the braking force. The position where piston 131 begins to contact wheel disc 150 is called the contact point. Figure 2C As shown, when piston 131 passes the contact point and moves toward wheel disc 150, the force of piston 131 pressing against brake pad 140 increases. Here, the force of piston 131 pressing against brake pad 140 is called clamping force. If the clamping force increases, the frictional force generated between brake pad 140 and wheel disc 150 increases. That is, the braking force increases.

[0037] According to embodiments of the present disclosure, the electromechanical brake can estimate the clamping force using a current sensor and a position sensor instead of a load sensor.

[0038] The position detection unit 170 can accurately measure the position of the piston 131 using an angle sensor. However, since the contact point varies depending on the wear condition of the brake pad 140, the position of the contact point cannot be identified solely by the position of the piston 131. Without identifying the contact point, it is difficult to accurately estimate the clamping force based on the position of the piston 131.

[0039] The current detection unit 180 detects the value of the current flowing through the motor 120. The control unit 160 feeds back the current value detected by the current detection unit 180 to control the motor 120. The electromechanical braking device according to an embodiment of this disclosure uses current control to identify the position of the contact point.

[0040] Figure 3 It is a curve of current measured based on the operating distance of the brake pad.

[0041] refer to Figure 3 The intensity of the current flowing through motor 120 increases proportionally to the magnitude of the clamping force. Because the current sensor's measurements have a large error range, it is difficult to accurately estimate the clamping force. See also... Figure 3 When the current sensor detects value i x When a contact point is identified, a large error range e occurs due to measurement noise from the current sensor. The current detection unit 180 according to an embodiment of this disclosure includes a current sensor that measures the current flowing through the motor 120 and a low-pass filter (not shown) that eliminates noise from the current value measured using the current sensor. When only the current sensor is used, a first current value can be measured at multiple locations on the piston 131 due to measurement noise. The contact point calculation unit 165 uses the current value, in which noise is reduced by applying the low-pass filter, to detect the first position.

[0042] Figure 4 This is a graph illustrating the method for estimating the location of the contact point.

[0043] refer to Figure 4 The horizontal axis of the graph represents the position of piston 131, while the vertical axis represents the current flowing through motor 120. As the graph moves to the right on the horizontal axis, the gap g between brake pad 140 and wheel disc 150 (see...) Figure 1 () decrease.

[0044] The current value of motor 120 remains essentially constant in the interval before contact point X, but the current value decreases after contact point X. Figure 4 The current increases non-linearly within the non-linear interval a shown. If the operating distance increases further beyond the non-linear interval a, the current value will increase non-linearly. Figure 4 The current increases linearly within the linear interval b shown. Here, the linear interval b refers to the interval in which the current value detected by the current detection unit 180 changes linearly within a predetermined error range of the position of the piston 131.

[0045] The current detection unit 180 detects the first current value i. set The position of piston 131 is defined as the first position Y1. The first current value i is a preset value. set It can be the current value over the linear interval b. When the first current value i set When the current value is in the linear interval b, the error range in the linear interval b is narrower than the error range e in the nonlinear interval a, so the contact point can be calculated more accurately.

[0046] The control unit 160 includes a processor (e.g., a computer, microprocessor, CPU, ASIC, circuit, logic circuit, etc.) and associated non-transitory memory storing software instructions that, when executed by the processor, provide all or part of the functions of the hysteresis data storage unit 161, the calculation unit 162, the past state data storage unit 163, the transition interval function data generation unit 164, the contact point calculation unit 165, the braking force calculation unit 166, and the motor controller 167. Here, the memory and processor can be implemented as separate semiconductor circuits. Alternatively, the memory and processor can be implemented as a single integrated semiconductor circuit. The processor may contain one or more processors.

[0047] The contact point calculation unit 165 calculates the contact point X based on a first position Y1, which is the position of the piston 131 when the current detection unit 180 detects a first current value. The contact point calculation unit 165 calculates the contact point X at a preset distance d from the first position Y1 in a direction away from the wheel 150. set The second position is designated as contact point X. According to the specifications of the electromechanical brake, the preset distance d is used as the interval for experimental measurements. set The value may vary. Based on the determined contact point X, the control unit 160 can use a position sensor to determine the relative position of the brake pad 140 and the wheel disc 150, as well as the size of the air gap.

[0048] When the vehicle stops, the motor controller 167 drives the motor 120 for a preset time, causing the piston 131 to move toward the wheel 150. When the vehicle is parked and the door is open, the motor controller 167 can drive the motor 120 for a preset time, causing the piston 131 to move toward the wheel 150. If the vehicle is parked and the door is open, the motor controller 167 can drive the motor 120 at a preset angular velocity for a preset time. The contact point calculation unit 165 can calculate the contact point X based on the current value data collected over the preset time regarding the position of the piston 131.

[0049] When the driver depresses the brake pedal before a preset time has elapsed, the motor controller 167 drives the motor 120 at a preset angular velocity for a preset time after the door opens, thereby causing the piston 131 to move toward the wheel disc 150. After the preset time has elapsed, the motor controller 167 controls the motor 120 to immediately generate braking force corresponding to the braking signal.

[0050] Figure 5 This is a graph showing the motor control time used to detect the contact point.

[0051] refer to Figure 5If the door is opened while the vehicle is stationary, the motor controller 167 drives the motor 120 at a predetermined angular velocity for approximately 2 seconds to move the piston 131 toward the wheel 150. In this disclosure, the operation of the motor controller 167 driving the motor 120 at a predetermined angular velocity for a predetermined time is referred to as ramp driving. The contact point calculation unit 165 identifies the contact point based on the current value data for the position of the piston 131 obtained through ramp driving.

[0052] If the driver depresses the pedal before the hill start assist ends, the motor controller 167 controls the motor 120 to generate a braking force corresponding to the braking signal input when the brake pedal is used immediately after the hill start assist ends. The hill start assist is performed while the vehicle is stationary. Therefore, even if a braking force not corresponding to the driver's braking signal is generated during the hill start assist, the driver will not perceive the generation of such a braking force.

[0053] The motor controller 167 controls the motor 120, so that the electromechanical brake generates the required braking force based on the braking force calculated by the braking force calculation unit 166.

[0054] Figure 6 It is a graph showing the magnitude of the braking force based on the piston's position and direction of movement.

[0055] refer to Figure 6 The horizontal axis of the graph represents the position of piston 131. When piston 131 is at the lowest point of the stroke, its position is set to 0. The vertical axis of the graph represents the braking force. The braking force is not determined solely by the position of piston 131. Even when piston 131 is in the same position, the braking force when piston 131 moves toward wheel 150 is different from the braking force when piston 131 moves away from wheel 150. Therefore, to accurately estimate the braking force, both the position of piston 131 and its movement path need to be considered. In this disclosure, the function of the increase in braking force as piston 131 moves toward wheel 150 is called the rise interval function f. a (see Figure 6 The function of the descending interval, in which the braking force decreases as the piston 131 moves away from the wheel 150, is called the descending interval function f. r (see Figure 6 ).

[0056] Figure 7 It is a graph illustrating the process of determining the function followed by the electromechanical brake according to an embodiment of the present disclosure to calculate the braking force.

[0057] refer to Figure 7 , Figure 7The vertical axis of the graph represents the position of piston 131. When piston 131 is at the lowest point of the stroke, its position is set to 0. The horizontal axis of the graph represents the elapsed time.

[0058] The motion state of piston 131 in the electromechanical brake can be divided into four states. In state ①, piston 131 moves towards wheel 150. That is, the differential value of piston 131's position with respect to time is positive. In state ③, the position of piston 131 decreases with time. That is, the differential value of piston 131's position with respect to time is negative. In states ② and ④, the position of piston 131 remains unchanged. That is, the differential value of piston 131's position with respect to time is 0. States ② and ④ are defined based on the motion state of piston 131 just before it stops. If the differential value of piston 131's position before it stops is positive, this can be defined as state ②. If the differential value of piston 131's position before it stops is negative, this can be defined as state ④. When the motion state of piston 131 is state ① or state ②, the braking force relative to the position of piston 131 is determined according to the rising interval function. When the piston 131 is in state ③ or state ④, the braking force for the position of the piston 131 is determined according to the descending interval function.

[0059] The hysteresis data storage unit 161 may be a storage medium or a memory, which stores the rising interval function f with respect to the rising interval. a Data (see) Figure 6 ) and the descending interval function f of the descending interval r Data (see) Figure 6 ).

[0060] The calculation unit 162 calculates the differential value of the position of the piston 131 with respect to time. The past state data storage unit 163 may also be a storage medium or memory, which stores data about the previous interval corresponding to the previous position of the piston 131.

[0061] The braking force calculation unit 166 can calculate the braking force based on the differential value of the piston 131's position and the data from the previous interval. When the differential value of the piston 131's position relative to time is positive, the braking force calculation unit 166 calculates the braking force according to an ascending interval function. When the differential value of the piston 131's position relative to time is negative, the braking force calculation unit calculates the braking force according to a descending interval function. If the differential value of the piston 131's position relative to time is 0, and the interval corresponding to the piston 131's previous position is an ascending interval, the braking force calculation unit calculates the braking force according to an ascending interval function. If the differential value of the piston 131's position relative to time is 0, and the interval corresponding to the piston 131's previous position is a descending interval, the braking force calculation unit calculates the braking force according to a descending interval function. Therefore, the braking force can be calculated using an appropriate function based on the piston 131's motion state. By using an appropriate function to calculate the braking force, the braking force can be calculated more accurately.

[0062] Figure 8A and 8B This is a graph illustrating the transition interval function according to an embodiment of the present disclosure.

[0063] refer to Figure 8A and 8B When the direction of movement of piston 131 changes to a position other than the highest or lowest point of braking force, the actual braking force changes continuously along path II, which follows the transition interval function. Here, the transition interval refers to the interval in which the braking force shifts from either the rising interval or the falling interval to another interval when the direction of movement of piston 131 changes.

[0064] Figure 8A It is a graph showing the path of how the braking force changes as the piston moves toward the wheel and then away from the wheel, depending on the distance the piston moves.

[0065] As the piston moves toward the wheel and then moves away from the wheel, the magnitude of the braking force varies along path I when the piston moves toward the wheel, along path II in the transition zone after changing direction, and along path III after the transition zone, depending on the distance the piston moves.

[0066] Figure 8B It is a graph showing the path of how the braking force changes as the piston moves away from the wheel and then toward the wheel.

[0067] As the piston moves away from the wheel and then toward the wheel, the braking force varies along path I when the piston moves away from the wheel, along path II in the transition zone after the change of direction, and along path III after the transition zone, depending on the distance the piston moves.

[0068] The function value of the transition interval function is greater than that of the descending interval function f. r The function value (see Figure 6 And less than the ascending interval function f a The function value (see Figure 6 The value of ). If the braking force calculation unit 166 only uses the rising interval function f a (see Figure 6 or the descending interval function f r (see Figure 6 If the braking force is calculated using the braking force calculation unit 166 during the transition interval, a difference will occur between the braking force calculated by the braking force calculation unit 166 and the actual braking force. Therefore, the electromechanical brake according to an embodiment of this disclosure includes a transition interval function data generation unit 164 for generating transition interval function data.

[0069] The transition interval function data generated by the transition interval function data generation unit 164 can be determined based on the wear amount of the brake pad 140.

[0070] The transition interval function data generation unit 164 according to an embodiment of the present disclosure may include a memory (not shown) for storing transition interval function data on the transition interval. After obtaining the transition interval function data experimentally, the data can be converted into a look-up table (LUT) and stored in the memory. The function data stored in the memory is retrieved and used to calculate the braking force. On the other hand, the transition interval function data generation unit 164 according to another embodiment of the present disclosure includes a transition interval function data calculation unit (not shown) that calculates the transition interval function in real time based on the position of the piston 131 to generate the function.

[0071] The braking force calculation unit 166 calculates the braking force based on the position of the piston 131.

[0072] As piston 131 moves toward wheel 150, its position can be substituted into the ascending interval function f. a To calculate braking force (see Figure 6 However, as piston 131 moves away from wheel 150 and then toward wheel 150, the braking force is calculated using a transition interval function within the position range of piston 131, where the value of the transition interval function is less than the value of the rising interval function f. a The value (see) Figure 6 In other words, when the direction of movement of piston 131 changes from away from wheel 150 to towards wheel 150, braking force calculation unit 166 follows the transition interval function and the rising interval function f. a (see Figure 6The braking force is calculated using a function with a smaller function value in the ().

[0073] As piston 131 moves away from wheel 150, its position can be substituted into the descending interval function f. r To calculate braking force (see Figure 6 However, as piston 131 moves toward and then away from wheel 150, the descending interval function f in the position interval of piston 131 is used. r (see Figure 6 The braking force is calculated using f, where the function value in the transition interval is less than the function value in the descent interval. r (see Figure 6 The value of ). In other words, when the direction of movement of piston 131 changes from toward wheel 150 to away from wheel 150, braking force calculation unit 166 follows the transition interval function and the descent interval function f. r (see Figure 6 The braking force is calculated using a function with a large function value. By configuring the electromechanical braking device in this way, the braking force can be accurately estimated even when the direction of movement of the piston 131 changes.

[0074] Figure 9 This is a graph showing the rising interval function, the falling interval function, and the transition interval function according to embodiments of the present disclosure.

[0075] refer to Figure 9 By reflecting the hysteresis characteristics of the braking force based on the position of piston 131, the transition interval function f t,1 and f t,2 It can have a positive slope. At any position of piston 131, the transition interval function f t,1 and f t,2 The differential value can be greater than that of the function f in the ascending interval. a (see Figure 9 The differential value of f and the function of decreasing interval. r (see Figure 9 The differential value of ).

[0076] To more easily generate the transition interval function f t,1 and f t,2 The transition interval function f t,1 and f t,2 It can be a linear function with a positive slope. It can also be a function f with multiple transition intervals between the rising and falling intervals. t,1 and f t,2 It can be a linear function with the same slope.

[0077] According to an embodiment of the present disclosure, the control unit 160 determines the degree of wear of the brake pad 140 by measuring the distance between the contact point and the lowest point of the stroke of the piston 131.

[0078] Figure 10 It is a graph showing the change in braking force function with respect to piston position as the brake pads wear.

[0079] refer to Figure 10 S1 is a graph showing the current intensity based on the position of piston 131. S2 is a graph showing the current intensity based on the position of piston 131 as brake pad 140 wears further compared to S1. Figure 10 In the diagram, to clearly show the relationship between the position of piston 131 and the braking force based on the wear of brake pad 140, hysteresis characteristics are not shown. However, the following description applies to the rising interval function f. a (see Figure 6 ), transition interval function and descent interval function f r (see Figure 6 ).

[0080] If brake pad 140 wears, the contact point moves from X to X'. That is, the contact point moves towards wheel disc 150. As brake pad 140 wears, the rigidity of brake pad 140 increases, causing the linear interval b (see...) Figure 4 The slope in () increases. The first checkpoint moves from Y1 to Y1′. Therefore, the preset distance, which is the distance from the first position to the second position, should be from d. set to d set 'Set differently. That is, the preset distance should be set differently according to the wear level of the brake pad 140.'

[0081] Control unit 160 can measure the absolute distance of contact point X and determine that the wear degree of brake pad 140 increases with the increase of the absolute distance. Here, the absolute distance of contact point X refers to the operating distance from the lowest point of the stroke to the contact point. Control unit 160 can find and apply d based on the wear degree of brake pad 140. set The value of '. Based on the wear level of brake pad 140, d set The changes can be obtained experimentally, converted into a lookup table (LUT) format, and stored in the memory of the control unit 160. That is, the control unit 160 can calculate the absolute distance of the brake pad 140 to determine the degree of wear of the brake pad 140, and then... set Convert the value to d set The value of ' is used to estimate the contact point X' of the worn brake pad 140.

[0082] As the brake pad 140 wears, the differential value of the braking force function based on the position of the piston 131 increases at any point on the piston 131. The electromechanical brake according to an embodiment of this disclosure determines the rising interval function f based on the amount of wear on the brake pad 140. a (see Figure 6 ), transition interval function and descent interval function f r (see Figure 6 According to an embodiment of this disclosure, the hysteresis data storage unit 161 stores a plurality of rising interval functions f determined based on the wear amount of the brake pad 140. a (see Figure 6 The data and the multiple descending interval functions f determined based on the wear of brake pad 140. r (see Figure 6 The data on ).

[0083] When the brake pad 140 begins to contact the wheel disc 150, the position P of the piston 131 can be measured from the lowest point of the stroke of the piston 131. x and P x' The distance is used to determine the amount of wear on the brake pad 140.

[0084] While exemplary embodiments of this disclosure have been described for illustrative purposes, those skilled in the art will understand that various modifications, additions, and substitutions are possible without departing from the spirit and scope of the claimed invention. Therefore, exemplary embodiments of this disclosure have been described for the sake of brevity and clarity. The scope of the technical concept in these embodiments is not limited to the examples. Therefore, those skilled in the art will understand that the scope of the claimed invention is not limited to the embodiments explicitly described above, but rather to the technical solutions of this disclosure and their equivalents.

Claims

1. An electromechanical brake configured such that a piston pulls a brake pad toward a wheel disc via a drive motor, the electromechanical brake comprising: A hysteresis data storage unit stores rising interval function data on the rising interval and falling interval function data on the falling interval, wherein the braking force increases as the piston moves toward the wheel, and wherein the braking force decreases as the piston moves away from the wheel; A position detection unit detects the position of the piston; A calculation unit that calculates the differential value of the piston's detection position relative to time; The past state data storage unit stores the data in the previous interval corresponding to the previous piston position; and The braking force calculation unit calculates the braking force based on the differential value of the piston position and the data in the previous interval.

2. The electromechanical brake according to claim 1, wherein, When the differential value of the piston position with respect to time is positive, the braking force calculation unit calculates the braking force by following the rising interval function.

3. The electromechanical brake according to claim 1, wherein, When the differential value of the piston position with respect to time is zero and the interval corresponding to the previous piston position is an ascending interval, the braking force calculation unit calculates the braking force by following the ascending interval function.

4. The electromechanical brake according to claim 1, wherein, When the differential value of the piston position with respect to time is zero and the interval corresponding to the previous piston position is a descending interval, the braking force calculation unit calculates the braking force by following the descending interval function.

5. The electromechanical brake according to claim 1, wherein, When the differential value of the piston position with respect to time is negative, the braking force calculation unit calculates the braking force by following the descending interval function.

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