Electromechanical brake

Abstract

This disclosure provides an electromechanical brake in several embodiments, configured such that a piston, under the action of a drive motor, pulls brake pads toward a brake disc. The electromechanical brake includes: a hysteresis data storage unit for storing: rising interval function data regarding a rising interval, wherein, in the rising interval, the braking force increases as the piston moves toward the brake disc; and falling interval function data regarding a falling interval, wherein, in the falling interval, the braking force decreases as the piston moves away from the brake disc; a transition interval function data generation unit for generating data related to a transition interval function, wherein, in the transition interval, as the piston's movement direction changes, the braking force is transferred from either the rising or falling interval to the other interval; a position detection unit; and a braking force calculation unit.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2021-0119776, 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) have a wide range of applications. Developed as electronic parking brakes (EPBs), their use is 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 the vehicle to be braked directly by the motor's force, without the need for brake fluid or other media. Because the mechanism of an EMB is similar to that of an EPB, the only difference being that it is primarily used as a main brake, EMBs require higher braking response and operational durability compared to EPBs. Furthermore, compared to hydraulic brakes, electro-mechanical brakes have a simpler structure, faster braking response, and more precise control, thus 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 inevitably increases due to the sensor mounting.

[0007] To prevent increased manufacturing costs and EMB size, 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, estimating the clamping force by measuring the current flowing through the motor has problems because the estimation accuracy is reduced due to the measurement noise of the current sensor compared to using a load sensor.

[0008] Figure 11A , Figure 11B and Figure 11C This is a schematic diagram showing the structure of a conventional electromechanical brake.

[0009] refer to Figure 11A, Figure 11B and Figure 11C The EMB includes a brake disc 11_c, a pair of brake pads 11_b disposed on both sides of the brake disc 11_c, and a piston 11_a for pressing the brake pads 11_b against the brake disc 11_c. As the piston 11_a moves toward the brake disc 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 varies depending on the movement path of the piston 11_a. That is, the braking force at the position of the piston 11_a exhibits hysteresis. 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, an electromechanical brake according to one 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 one embodiment, the electromechanical brake calculates the braking force by taking into account the hysteresis of the braking force at the piston position, thereby calculating the braking force 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 problems not mentioned can 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 brake pads toward a brake disc via a drive motor. The electromechanical brake includes: a hysteresis data storage unit for storing rising interval function data regarding a rising interval, wherein the braking force increases as the piston moves toward the brake disc; and falling interval function data regarding a falling interval, wherein the braking force decreases as the piston moves away from the brake disc; a transition interval function data generation unit for generating data related to a transition interval function for a transition interval, wherein the braking force transitions from either the rising interval or the falling interval to the remaining interval of the rising and falling intervals as the piston's movement direction changes; a position detection unit for detecting the piston's position; and a braking force calculation unit for calculating the braking force based on the detected piston position.

[0014] According to one embodiment, an electromechanical brake has the advantage that the clamping force can be estimated more accurately by estimating the clamping force based on the position of the piston that detects a specific current value.

[0015] According to one embodiment, the advantage of an electromechanical brake is that the braking force can be calculated more accurately by taking into account the hysteresis of the braking force at the piston position. Attached Figure Description

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

[0017] Figure 2A , Figure 2B and Figure 2C This is a schematic diagram 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 working distance of the brake pads.

[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 Figure 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 This is a graph showing how the braking force function changes with the piston position as the brake pads wear.

[0026] Figure 11A , Figure 11B and Figure 11C This is a schematic diagram showing the structure 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, the same reference numerals preferably denote the same elements, although these elements are shown in different drawings. Furthermore, in the following description of some embodiments, detailed descriptions of known functions and configurations contained herein will be omitted for clarity and brevity.

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

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

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

[0031] A brake disc 150 is connected to the wheel and rotates with it. By restricting the rotation of the brake disc 150, the vehicle can be braked. Brake pads 140 are disposed on the side of the brake disc 150. A piston 131 is configured to push the brake pads 140 against the brake disc 150 via a motor 120. When the piston 131 presses the brake pads 140 against the brake disc 150, friction is generated between the brake pads 140 and the brake disc 150. Due to the friction generated between the brake pads 140 and the brake disc 150, the rotation of the brake disc 150 is restricted. 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 below. 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 screw shaft 132. Screw shaft 132 rotates with driven gear 133. A thread is formed on the outer circumference of screw shaft 132. A threaded groove corresponding to the thread shape of screw 132 is formed on the inner circumference of piston 131. If screw shaft 132 rotates together with driven gear 133, piston 131 moves linearly while being screwed into or out of screw shaft 132. If piston 131 moves linearly toward brake disc 150, brake pad 140 is pushed against brake disc 150 by piston 131.

[0033] The position detection unit 170 detects the position of the piston 131. The position of the piston 131 represents the distance from the lowest point of the piston 131's stroke to the piston 131. Here, the lowest point of the stroke refers to the position of the brake pad 140 when the distance between the brake pad 140 and the brake 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 21 sensed by the angle sensor to calculate the linear travel distance of the piston 131. The linear travel distance of the piston 131 based 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 piston 131 moves a linear distance of 1 mm.

[0035] Figure 2A , Figure 2B and Figure 2C This is a schematic diagram illustrating the driving state of an electromechanical brake according to an embodiment of the present disclosure.

[0036] Reference Figure 2A When the brake pads 140 are spaced apart from the brake disc 150, no braking force is generated. Here, the braking force is used to brake the vehicle. When the piston 131 pushes the brake pads 140 to contact the brake disc 150, as... Figure 2B As shown, friction is generated between the brake pad 140 and the brake disc 150. This friction serves as the braking force. The position of the piston 131 when the brake pad 140 begins to contact the brake disc 150 is called the contact point. Figure 2C As shown, when piston 131 continues to move towards brake disc 150 past the contact point, the force with which piston 131 presses against brake pad 140 increases. This force is referred to as clamping force. If the clamping force increases, the frictional force between brake pad 140 and brake disc 150 increases. That is, the braking force increases.

[0037] The electromechanical brake according to embodiments of this disclosure can estimate the clamping force by using current sensors and position sensors, rather than by using load sensors.

[0038] The position detection unit 170 can accurately measure the position of the piston 131 using an angle sensor. However, since the contact point changes 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 current value 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 working distance of the brake pads.

[0041] Reference Figure 3 The current flowing through motor 120 increases proportionally to the clamping force. Because the current sensor's measurements have a large error range, it is difficult to accurately estimate the clamping force. (Refer to...) Figure 3 When the current sensor detects i x When the value is determined to be a contact point, 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, the first current value may be measured at multiple locations on the piston 131 due to measurement noise. The contact point calculation unit 165 uses the current value to detect the first position, wherein noise in the current value is reduced by using a low-pass filter.

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

[0043] Reference Figure 4 In the diagram, the horizontal axis represents the position of piston 131, and the vertical axis represents the current flowing through motor 120. As the piston moves to the right along the horizontal axis, the clearance g between brake pad 140 and brake disc 150 (see...) Figure 1 () decrease.

[0044] Before contact point X, the current value of motor 120 remains basically constant, but after contact point X, the current value of motor 120... Figure 4 In the nonlinear interval 'a' shown, the current value increases nonlinearly. If the working distance further increases beyond the nonlinear interval 'a', the current value will... 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] When the current detection unit 180 detects the first current value i set At that time, 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 smaller than the error range e in the nonlinear interval a, thus 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. When the processor executes the software instructions, the software instructions provide all or some of the following functions: hysteresis data storage unit 161, calculation unit 162, past state data storage unit 163, transition interval function data generation unit 164, contact point calculation unit 165, braking force calculation unit 166, and motor controller 167. Here, the memory and processor can be implemented as separate semiconductor circuits. Alternatively, the memory and processor can also 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, where the first position Y1 is the position of the piston 131 when the current detection unit 180 detects a first current value. The contact point calculation unit 165 then calculates a second position, which is located away from the brake disc 150 and is a preset distance d from the first position Y1. set The second position is taken as the contact point X. The preset distance d... set The value is an experimentally measured value and will vary depending on the specifications of the electromechanical brake. The control unit 160 can determine the relative position of the brake pad 140 and the brake disc 150, as well as the size of the air gap, based on a defined contact point X using a position sensor.

[0048] When the vehicle stops, the motor controller 167 drives the motor 120 for a preset time period, causing the piston 131 to move towards the brake disc 150. When the vehicle is parked and the door is open, the motor controller 167 can drive the motor 120 for a preset time period, causing the piston 131 to move towards the brake disc 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 period. Based on the current value data about the position of the piston 131 collected within a preset time period, the contact point calculation unit 165 can calculate the contact point X.

[0049] When the driver depresses the brake pedal before the preset time expires, the motor controller 167 drives the motor 120 at a preset angular velocity for a preset time length after the door opens, thereby causing the piston 131 to move towards the brake disc 150. After the preset time is reached, the motor controller 167 immediately controls the motor 120 to 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] Reference Figure 5If the vehicle is parked and the door is open, the motor controller 167 drives the motor 120 at a predetermined angular velocity for approximately 2 seconds, thereby moving the piston 131 toward the brake disc 150. In this disclosure, the operation of the motor controller 167 driving the motor 120 at a predetermined angular velocity for a preset time length is referred to as ramp driving. The contact point calculation unit 165 identifies the contact point based on the current value data of the piston 131 position obtained through ramp driving.

[0052] If the driver depresses the pedal before the hill start is complete, the motor controller 167 immediately controls the motor 120 to generate a braking force corresponding to the braking signal input using the brake pedal after the hill start is complete. The hill start is performed while the vehicle is stationary. Therefore, even if a braking force that does not correspond to the driver's braking signal is generated during the hill start, the driver will not perceive the braking force that does not correspond to the braking signal.

[0053] The motor controller 167 controls the motor 120, causing the electromechanical brake to generate 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] Reference Figure 6 The horizontal axis of the graph represents the position of piston 131. When piston 131 is at the lowest point of its stroke, its position is set to 0. The vertical axis of the graph represents the braking force. The braking force is not solely determined by the position of piston 131. Even when piston 131 is in the same position, the braking force when piston 131 moves towards brake disc 150 is different from the braking force when piston 131 moves away from brake disc 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 towards brake disc 150 is called the increase interval function f. a (See Figure 6 The function of the decreasing range of braking force as the piston 131 moves away from the brake disc 150 is called the decreasing range 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] Reference 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 movement state of piston 131 in the electromechanical brake can be divided into four types. In state ①, piston 131 moves towards brake disc 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. In other words, the differential value of piston 131's position with respect to time is 0. States ② and ④ are defined based on the movement state of piston 131 before it stops. Before piston 131 stops, if the differential value of piston 131's position is positive, it can be defined as state ②; if the differential value of piston 131's position is negative, it can be defined as state ④. When the movement state of piston 131 is state ① or state ②, the braking force of piston 131's position is determined according to the rising interval function. When the piston 131 is in state ③ or state ④, the braking force of the piston 131 is determined according to the descending interval function.

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

[0060] The calculation unit 162 calculates the differential value of the position of piston 131 with respect to time. The past state data storage unit 163 may also be a storage medium or memory, which stores data of the previous interval corresponding to the position of the previous 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 data about 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 previous piston 131's 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 previous piston 131's position is a descending interval, the braking force calculation unit calculates the braking force according to a descending interval function. In this way, the braking force can be calculated using an appropriate function based on the movement state of the piston 131. By using an appropriate function to calculate the braking force, the braking force can be calculated more accurately.

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

[0063] Reference Figure 8A and Figure 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 will continue to change according to the transition interval function path II. Here, the transition interval refers to the interval in which the braking force changes from either the rising interval or the falling interval to another interval as the direction of movement of piston 131 changes.

[0064] Figure 8A It is a graph showing the path of the braking force as the piston moves from the brake disc to the brake disc and then away from it, according to the distance the piston moves.

[0065] When the piston moves towards the brake disc first and then moves away from the brake disc, the magnitude of the braking force when the piston moves towards the brake disc varies along path I according to the distance the piston moves; after changing direction, the magnitude of the braking force changes along path II in the transition interval; after the transition interval, it changes along path III.

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

[0067] As the piston moves away from the brake disc and then toward the brake disc, the magnitude of the braking force varies according to the distance the piston moves: along path I when the piston moves away from the brake disc; along path II during the transition zone; and along path III after the transition zone.

[0068] The function value of the transition interval function is greater than that of the descent interval function f. r (See Figure 6 And less than the ascending interval function f a (See Figure 6 The value of the function f. 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 regarding the transition interval. After obtaining the transition interval function data experimentally, the data can be converted into a look-up table (LUT) format 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), which calculates the transition interval function based on the real-time 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] When piston 131 moves toward brake disc 150, the position of piston 131 can be substituted into the ascending interval function f. a (See Figure 6 The braking force is calculated using a transition interval function. However, when the piston 131 moves away from and towards the brake disc 150, the braking force is calculated using the transition interval function of the piston 131 during its transition interval, where the transition interval function value is less than the rising interval function f. a (See Figure 6The value of ). In other words, when the direction of movement of piston 131 changes from away from brake disc 150 to towards brake disc 150, braking force calculation unit 166 calculates the braking force according to the transition interval function and the rising interval function f. a (See Figure 6 The braking force is calculated using a function with a smaller function value in the ().

[0073] When piston 131 moves in a direction away from brake disc 150, the position of piston 131 can be substituted into the descending interval function f. r (See Figure 6 The braking force is calculated using the transition interval function f. However, when the piston 131 first moves towards the brake disc 150 and then moves away from the brake disc 150, the descent interval function f in the transition interval of the piston 131 is used. r (See Figure 6 The braking force is calculated using the function f(x) in the transition interval, where the function value in the transition interval is less than that 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 brake disc 150 to away from brake disc 150, braking force calculation unit 166 calculates the braking force according to 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] Reference Figure 9 By reflecting the hysteresis of 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 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 existing 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 This is a graph showing how the braking force function changes with the piston position as the brake pads wear.

[0079] Reference 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 graph, to clearly show the relationship between the position of piston 131 and the braking force according to the wear of brake pad 140, hysteresis is not shown. However, the following description applies to all ascending interval functions 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 brake disc 150. As brake pad 140 wears, its rigidity increases, thus increasing the slope in the linear interval b (see...). Figure 5 The first checkpoint moves from Y1 to Y1'. Therefore, the preset distance, that is, the distance from the first position to the second position, should be from d. set Change it to: In other words, the preset distance should be set differently depending on the wear level of the brake pads 140.

[0081] The control unit 160 can measure the absolute distance of contact point X and determine that the wear degree of brake pad 140 increases as the absolute distance increases. Here, the absolute distance of contact point X refers to the working distance from the lowest point of the stroke to the contact point. The control unit 160 can determine and apply d based on the wear degree of brake pad 140. set The value of '. d set The changes in wear of brake pad 140 can be obtained experimentally, converted into a lookup table (LUT) format, and stored in the memory of control unit 160. That is, control unit 160 can calculate the absolute distance of brake pad 140 to determine the degree of wear of brake pad 140 and assign it to the appropriate value. 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 pads 140 wear, the differential value of the braking force function relative to 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 pads 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 based on the wear amount of the brake pad 140. a (See Figure 6 The data and the function f with multiple decreasing intervals determined based on the wear of brake pad 140. r (See Figure 6 (Data).

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

[0084] Although 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 of these embodiments is not limited by the illustrations. 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 claims and their equivalents.

Claims

1. An electromechanical brake for causing a piston, under the action of a drive motor, to pull a brake pad toward a brake disc, the electromechanical brake comprising: A hysteresis data storage unit is used to store: rising interval function data with respect to the rising interval, wherein, in the rising interval, the braking force increases as the piston moves toward the brake disc; and falling interval function data with respect to the falling interval, wherein, in the falling interval, the braking force decreases as the piston moves away from the brake disc; A transition interval function data generation unit is used to generate data about the transition interval function, wherein, in the transition interval, when the piston's movement direction changes, the braking force is switched from either the rising interval or the falling interval to the other interval between the rising interval and the falling interval. A position detection unit is used to detect the position of the piston; and A braking force calculation unit is used to calculate the braking force based on the detected position of the piston.

2. The electromechanical brake according to claim 1, wherein, The transition interval function data generation unit includes a memory for storing transition interval function data about the transition interval.

3. The electromechanical brake according to claim 1, wherein, The transition interval function data generation unit includes a calculation unit, which calculates the transition interval function based on the detected position of the piston.

4. The electromechanical brake according to claim 1, wherein, When the piston's direction of movement changes from toward the brake disc to away from the brake disc, the braking force calculation unit calculates the braking force according to the function with the larger function value among the transition interval function and the descending interval function.

5. The electromechanical brake according to claim 1, wherein, When the piston's direction of movement changes from away from the brake disc to towards the brake disc, the braking force calculation unit calculates the braking force according to the function with the smaller function value among the transition interval function and the rising interval function.

6. The electromechanical brake according to claim 1, wherein, The transition interval function has a positive slope.

7. The electromechanical brake according to claim 1, wherein, The transition interval function is a linear function with a positive slope.

8. The electromechanical brake according to claim 1, wherein, The multiple transition functions between the rising interval and the falling interval are all linear functions with the same slope.

9. The electromechanical brake according to claim 1, wherein, The differential value of the transition interval function is greater than the differential value of the rising interval function at any piston position and the differential value of the falling interval function at any piston position.

10. The electromechanical brake according to claim 1, wherein, The hysteresis data storage unit stores multiple rising functions and multiple falling functions that change according to the wear of the brake pads.

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