Patent Application
20250074371
The present application claims priority to Patent Application No. 10-2023-0116135, filed on Sep. 1, 2023 in Korea, the entire contents of which are incorporated herein by reference.
The present disclosure relates to an electro-mechanical brake and a control method therefor.
The content described in this section simply provides background information for the present disclosure and does not constitute related art.
An electro-mechanical brake (EMB) is a brake apparatus that generates friction braking force. In the electro-mechanical brake, an actuator driven by a motor is mounted on a brake caliper. The electro-mechanical brake presses a wheel disc using a motor, gear box, screw, piston, brake pad, or the like without a medium called a brake fluid.
The electro-mechanical brake has a similar mechanism to an electronic parking brake (EPB), but since the electro-mechanical brake is a main brake apparatus that is used while traveling, the electro-mechanical brake requires higher reliability and durability.
When a driver steps on a pedal, the electro-mechanical brake calculates a required braking force and applies a brake command to each wheel. When the brake command is applied, a motor starts to rotate to move a piston forward, and the piston presses a brake pad. The brake pad presses the wheel disc so that the braking force is generated.
An electro-mechanical brake (EMB) of the related art measures the braking force using a force sensor and controls the braking force. The force sensor mounted on the electro-mechanical brake is expensive. In addition, the force sensor has a disadvantage that the force sensor does not accurately measure the braking force depending on a mounting position of the force sensor. To overcome such disadvantages, a force sensorless system is used.
The force sensorless system refers to a system that estimates braking force without using a force sensor. An electro-mechanical brake having a force sensorless system applied thereto perform calibration. Here, the calibration refers to a process of setting the electro-mechanical brake. The electro-mechanical brakes can perform the calibration to ascertain a braking force value corresponding to a position of the piston. A map in which the braking force value corresponding to the position of the piston is indexed is called a force map. With the force map, the electro-mechanical brake can ascertain without the force sensor and adjust the braking force.
Since a state of the electro-mechanical brake such as wearing of the brake pad changes with use, the calibration must be performed each time the vehicle is used to update information on the electro-mechanical brake. The calibration is preferably performed before driving starts. For example, when the driver opens a door of the vehicle or starts up the vehicle, the calibration can be performed and the force map can be generated.
That is, the electro-mechanical brake using the force sensorless system can perform the calibration to ascertain a current state of the electro-mechanical brake and generate data for estimation of the braking force. It is important to end the calibration quickly. This is because the driver can drive after the calibration is completed.
The calibration is usually performed only when the driver opens the door or starts up the vehicle. It is not preferable to perform the calibration during traveling. This is because a process of performing the calibration includes a process of driving a motor to move the piston and the brake pad, and a process of generating braking force. When the calibration is performed regardless of the driver's will during traveling, the driver may feel uncomfortable in braking, and a traffic accident may occur.
A force map generated when the driver opens the door or starts up the vehicle reflects only a state of the electro-mechanical brake at a point in time when the force map is generated. The force map does not reflect, in real time, a state of the electro-mechanical brake changing due to braking performed during traveling. For example, when braking is performed during traveling, the brake pad may wear and stiffness of the brake pad may change. Thus, when the state of the electro-mechanical brake is different from a state at a point in time when the force map is generated due to braking performed during traveling, a method of accurately estimating the braking force without performing additional calibration is required. This is because it is not preferable to perform the calibration during driving as described above. That is, a method capable of accurately estimating the braking force during driving is required.
The present disclosure is intended to solve these problems, and a main object of the present disclosure is to provide a method capable of accurately detecting braking force without performing additional calibration when a state of an electro-mechanical brake changes from a state before traveling due to braking performed during traveling.
As described above, according to the present embodiment, there is an effect that the electro-mechanical brake can accurately detect an actual braking force value without performing additional calibration after stopping a vehicle when a state of the electro-mechanical brake changes from a state before traveling due to braking performed during traveling.
Hereinafter, some exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, like reference numerals preferably designate like elements, although the elements are shown in different drawings. Further, in the following description of some embodiments, a detailed description of known functions and configurations incorporated therein will be omitted for the purpose of clarity and for brevity.
Additionally, various terms such as first, second, A, B, (a), (b), etc., are used solely to differentiate one component from the other but not to imply or suggest the substances, order, or sequence of the components. Throughout this specification, when a part ‘includes’ or ‘comprises’ a component, the part is meant to further include other components, not to exclude thereof unless specifically stated to the contrary. The terms such as ‘unit’, ‘module’, and the like refer to one or more units for processing at least one function or operation, which may be implemented by hardware, software, or a combination thereof.
Each element of the apparatus or method in accordance with the present invention may be implemented in hardware or software, or a combination of hardware and software. The functions of the respective elements may be implemented in software, and a microprocessor may be implemented to execute the software functions corresponding to the respective elements.
Referring to
When the driver steps on a brake pedal (not illustrated), the braking force generating unit 100 calculates required braking force on the basis of a stroke of a driver and then generates the braking force. The braking force generating unit 100 may be mounted on a wheel of a vehicle to generate the braking force. The braking force generating unit 100 may 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 force to change kinetic energy of the vehicle into heat energy to brake the vehicle.
The braking force generating unit 100 may include all or some 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 drawings. For example, a shape, size, and disposition of the motor 210, the gear box 220, the power transfer unit 230, the piston 240, the brake pad 250, the rotation shaft 270, and the wheel disc 260 are not limited by the disclosure of the drawings.
The motor 210 rotates to move the piston 240. A direction of the piston 240 that is used in the present specification is defined. Forward movement means that the piston 240 moves toward the wheel disc 260. Backward movement means that the piston 240 moves in a direction away from the wheel disc 260.
According to an embodiment, the motor 210 is a direct current motor (DC Motor), an alternating current motor (AC Motor), an induction motor, a synchronous motor, a step motor, a servo motor, a brushless direct current motor (BLDC motor), a linear motor, a permanent magnet synchronous motor (PMSM), or the like.
One side of the gear box 220 is connected to the motor 210, and the other side of the gear box 220 is connected to the power transfer unit 230. The gear box 220 is configured to transfer power of the motor 210 to the power transfer unit 230. The gear box 220 includes a plurality of gears 221 therein. In the gear box 220, the plurality of gears 221 are engaged and rotated so that rotational force is amplified. A shape and disposition of the gear box 220 are not limited by the drawings. Each of the plurality of gears 221 is not limited to the shape and number illustrated in the drawings.
The power transfer unit 230 may receive the power from the gear box 220. The power transfer unit 230 may provide the power to the piston 240.
According to an embodiment, the power transfer unit 230 may be a screw shaft. In this case, the piston 240 may be screw-coupled to 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 piston 240 moves by receiving the power transferred from the power transfer unit 230. When the piston 240 moves forward, the piston 240 presses the brake pad 250. The brake pad 250 brakes the vehicle by pressing the rotating wheel disc 260.
There may be a pair of brake pads 250. The pair of brake pads 250 may be disposed on both sides of the wheel disc 260. The wheel disc 260 is coupled to the wheel of the vehicle and rotates 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 the braking force is generated. Since force with which the brake pad 250 presses the wheel disc 260 increases as a forward movement distance of the piston 240 increases, the braking force increases.
The sensor unit 110 may include a current detection unit 113 and a position detection unit 115.
According to an embodiment, the current detection unit 113 may include a current sensor (not illustrated) to detect a current flowing through the motor 210. The electro-mechanical brake 1 can control the current flowing through the motor 210 using the current detection unit 113.
According to an embodiment, the position detection unit 115 may include a motor rotation angle sensor (not illustrated) to detect the rotation angle of the motor 210. As the motor 210 rotates, the piston 240 moves forward or backward. That is, since a position of the piston 240 is determined from the rotation angle of the motor 210, the electro-mechanical brake 1 may detect the position of the piston 240 using the position detection unit 115 including the motor rotation angle sensor.
A state of the electro-mechanical brake 1 used in the present specification will be defined. A first state refers to a state of the electro-mechanical brake 1 when power is applied to the vehicle due to start-up. That is, the first state is a state when no traveling or braking is performed. When the braking is performed during traveling, the state of the electro-mechanical brake 1 may change from the first state. For example, when the brake pad 250 wears, a physical property of the brake pad 250 may change. That is, stiffness of the brake pad 250 can change.
Referring to
The section A will be described in greater detail. The section A is a section in which the piston 240 is moved forward by the motor 210 and the piston 240 that has been moved forward presses the brake pad 250. The section A is a section in which the brake pad 250 moves forward to press the wheel disc 260 and generate the braking force. The section A is a section in which the braking force increases linearly as the current increases. The position of the piston 240 when the piston 240 starts to move forward using the motor 210 and the brake pad 250 and the wheel disc 260 spaced apart from each other start to come into contact with each other is referred to as a contact point. In the section A, a magnitude of the current flowing through the motor 210 increases as the piston 240 moves forward. As the piston 240 moves further away from the contact point, the magnitude of the current increases. The electro-mechanical brake 1 according to the present disclosure may detect a current value for the position of the piston 240, convert a correlation between the position of the piston 240, the current flowing through the motor 210, and the braking force into data, and generate a first map 123 and/or a second map 125. This will be described in greater detail with reference to
Referring to
In order to collect data regarding the current flowing through the motor 210, the position of the piston 240, and the braking force, the electro-mechanical brake 1 can perform RAMP control. Here, the RAMP control means performing control so that the current flowing through the motor 210 and/or the position of the piston 240 gradually increase in the first state. When STEP control for rapidly changing the position of the piston 240 is performed, a current according to the position of the piston 240 cannot be accurately measured, and thus, the electro-mechanical brake 1 according to the present disclosure performs the RAMP control to collect the data regarding the current flowing through the motor 210, the position of the piston 240, and the braking force. In the RAMP control, an inrush current TO is generated at a moment when the brake pad 250 comes into contact into the wheel disc 260 and the braking force is generated. Referring to a section TI of
The electro-mechanical brake 1 can collect data in the TI section in which the current flowing through the motor 210, the position of the piston 240, and the braking force increase with time. The electro-mechanical brake 1 may generate the first map 123 and/or the second map 125 on the basis of the collected data.
In a process of collecting data, the current flowing through the motor 210 can be detected using the current detection unit 113, and the position of the piston 240 can be detected using the position detection unit 115. As described in
The first map 123 and/or the second map 125 may be stored in the memory 120. The first map 123 is a map in which a correlation among the current flowing through the motor 210, the position of the piston 240, and braking force is converted into data with reference to the first state. The second map 125 is a map in which the current flowing through the motor 210 and a factor are converted into data with reference to the first state. The factor is a ratio of the braking force to the current flowing through the motor 210. That is, the factor is the braking force divided by the current.
Table 1 shows an example of the first map 123 generated on the basis of the data collected by performing the RAMP control. According to an embodiment, the first map 123 may be a look-up table. When the first map 123 is a look-up table, an output value can be obtained quickly. For example, when a position value of 0.55 of the piston 240 is input to the first map 123, a current value of 2.6 and a braking force value of 2254 corresponding to the position value of 0.55 of the piston 240 can be quickly output.
Table 2 illustrates an example of the second map 125 generated on the basis of the data collected by performing the RAMP control. The factor in Table 2 is the braking force divided by the current flowing through the motor 210. The factor may be used to detect accurate actual braking force when the state of the electro-mechanical brake 1 changes from the first state. According to an embodiment, the second map 125 may be a look-up table. When the second map 125 is the look-up table, the output value can be obtained quickly. For example, when the current value of 2.6 flowing through the motor 210 is input to the second map 125, a factor value of 867 corresponding to the current value of 2.6 can be quickly output.
The processor 130 may include a map generating unit 131 and an actual braking force value detection unit 133.
The map generating unit 131 may generate the first map 123 in the first state. Since the first map 123 is the map in which the correlation among the current flowing through the motor 210, the position of the piston 240, and braking force is converted into data with reference to the first state, it is preferable for the first map 123 to be generated before the traveling of the vehicle starts. This is because, when driving or braking is performed, the state of the electro-mechanical brake 1 changes from the first state. According to an embodiment, the map generating unit 131 may start to generate the first map 123 from a moment when a user opens a door of the vehicle. According to an embodiment, the map generating unit 131 may start to generate the first map 123 immediately after power is applied to the vehicle due to start-up.
The map generating unit 131 may generate the second map 125 in the first state. Since the second map 125 is a map in which the factor which is a ratio of the braking force to the current flowing through the motor 210 is converted into data with reference to the first state, it is preferable for the second map 125 to be generated before the vehicle starts to travel. This is because, when driving or braking is performed, the state of the electro-mechanical brake 1 changes from the first state. According to an embodiment, the map generating unit 131 may start to generate the second map 125 from a moment when the user opens the door of the vehicle. According to an embodiment, the map generating unit 131 may start to generate the second map 125 immediately after power is applied to the vehicle due to start-up.
When braking is performed during traveling, the actual braking force value detection unit 133 may detect the actual braking force value on the basis of an actual piston position, an actual current value, the first map 123, and the second map 125. The actual piston position refers to an actual position of the piston 240 detected by the position detection unit 115 when braking is performed during traveling. The actual current value refers to a value of an actual current flowing through the motor 210 detected by the current detection unit 113 when braking is performed during traveling. The actual braking force value refers to a value of actual braking force generated by the electro-mechanical brake 1 when braking is performed during traveling.
The electro-mechanical brake 1 of the related art without a force sensor estimates the braking force with reference to the first state. Since the state of the electro-mechanical brake 1 continuously changes from the first state due to braking performed during traveling, the electro-mechanical brake 1 of the related art has a disadvantage that the accuracy of the detected actual braking force value decreases as traveling continues.
The electro-mechanical brake 1 according to the present disclosure can overcome disadvantages of the electro-mechanical brake of the related art. Specifically, the actual braking force value detection unit 133 can accurately detect the actual braking force value even when the state of the electro-mechanical brake 1 is not the first state. That is, even when the state of the electro-mechanical brake 1 continuously changes due to braking performed during traveling, the electro-mechanical brake 1 can accurately detect the actual braking force value.
The actual braking force value detection unit 133 includes all or some of a first braking force value detection unit 134, a difference value detection unit 135, and a compensation value determination unit 136.
The first braking force value detection unit 134 determines a first braking force value on the basis of the actual piston position detected by the position detection unit 115 and the first map 123. Specifically, the first braking force value detection unit 134 determines a value of the braking force output when the actual piston position is input to the first map 123, as the first braking force value.
When the electro-mechanical brake 1 performs braking, the state of the electro-mechanical brake 1 changes from the first state, and thus, the first braking force value detected by the first braking force value detection unit 134 is different from the actual braking force value generated by the electro-mechanical brake 1. The electro-mechanical brake 1 according to the present disclosure compensates for the first braking force value to detect the actual braking force value. This will be described below.
The difference value detection unit 135 detects a difference between the actual current value detected by the current detection unit 113 and the first current value. The first current value refers to a value of a current that is output when the actual piston position detected by the position detection unit 115 is input to the first map 123.
The compensation value determination unit 136 determines the difference value multiplied by a first factor value as a compensation value. The first factor value refers to a value of a factor output when the actual current value detected by the current detection unit 113 is input to the second map 125. The compensation value may be used for accurate detection of the actual braking force value in a state other than the first state.
In a case in which the braking is performed during traveling and the state of the electro-mechanical brake 1 changes from the first state, the actual braking force value detection unit 133 may detect a sum of the compensation value and the first braking force value as the actual braking force value generated by the electro-mechanical brake 1. Here, the case in which the braking is performed during traveling and the state of the electro-mechanical brake 1 changes from the first state may be a case in which a temperature of the brake pad 250 changes and a volume of the brake pad 250 changes, or a case in which the brake pad 250 wears. Thus, the electro-mechanical brake 1 according to the present disclosure can accurately detect the actual braking force value even when the state of the electro-mechanical brake 1 changes from the first state due to braking performed during traveling.
Referring to
According to an embodiment, the electro-mechanical brake 1 may decide whether the state of the electro-mechanical brake 1 has changed from the first state (S520). When the state of the electro-mechanical brake 1 is the first state, the electro-mechanical brake 1 may detect the actual braking force value on the basis of the first map 123. Among the steps disclosed in
The electro-mechanical brake 1 may determine the first braking force value using the first map 123 (S530). Specifically, when braking is performed during traveling, the electro-mechanical brake 1 detects the actual piston position. The electro-mechanical brake 1 may determine the value of the braking force output when the detected actual piston position is input to the first map 123, as the first braking force value.
The electro-mechanical brake 1 can determine the first current value using the first map 123 (S540). Specifically, when braking is performed during traveling, the electro-mechanical brake 1 detects the actual piston position. The electro-mechanical brake 1 may determine a value of the current output when the detected actual piston position is input to the first map 123, as the first current value. Steps S530 and S540 may be performed simultaneously.
The electro-mechanical brake 1 can detect the difference value (S550). The difference value refers to a difference value between the actual current value detected by the current detection unit 113 and the first current value. When the actual current value is greater than the first current value, this means that the stiffness of the brake pad 250 increases. When the actual current value is smaller than the first current value, this means that the stiffness of the brake pad 250 is reduced. Thus, the electro-mechanical brake 1 according to the present disclosure can decide whether the stiffness of the brake pad 250 has increased or decreased depending on the difference value between the actual current value and the first current value.
The electro-mechanical brake 1 can detect the first factor value using the second map 125 (S560). Specifically, the value of the factor that is output when the actual current value detected by the current detection unit 113 is input to the second map 125 may be determined as the first factor value.
The electro-mechanical brake 1 may determine the compensation value (S570). Specifically, the difference value multiplied by the first factor value may be determined as the compensation value. The electro-mechanical brake 1 can accurately detect the actual braking force value by using the compensation value even when the electro-mechanical brake 1 is not in the first state.
The electro-mechanical brake 1 can detect the actual braking force value (S580). Specifically, the sum of the compensation value and the first braking force value may be detected as the actual braking force value generated by the electro-mechanical brake 1.
Thus, the electro-mechanical brake 1 according to the present disclosure can accurately detect the actual braking force value without a force sensor, and can accurately adjust the braking force on the basis of the detected actual braking force value. In the electro-mechanical brake 1 according to the present disclosure, the braking force can be accurately adjusted for a stable vehicle behavior, and uncomfortable braking can be reduced for provision of a high-quality user experience.
The electro-mechanical brake 1 according to the present disclosure can accurately detect the braking force in a state other than the first state, unlike an electro-mechanical brake of the related art in which the accuracy of the detected braking force decreases as the state changes due to traveling and braking. The electro-mechanical brake 1 according to the present disclosure can accurately detect the braking force even when calibration cannot be performed due to traveling.
Referring to
The electro-mechanical brake 1 can detect the current flowing through the motor 210 and the position of the piston 240 while step S600 is performed, and convert a correlation between the current flowing through the motor 210 and the position of the piston 240 into data (S610).
The electro-mechanical brake 1 can convert braking force corresponding to the current flowing through the motor 210 and the position of the piston 240 into data (S620). In a section in which the electro-mechanical brake 1 is applied (section TI in
The electro-mechanical brake 1 may generate the first map 123 and/or the second map 125 using data acquired in steps S600 to S620.
Referring to
Referring to
Referring to
Referring to
The actual braking force values F7_3, F8_3, and F9_3 detected by the electro-mechanical brake 1 according to the present disclosure illustrated in
Various implementations of 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 implementations may include one or more computer programs executable on a programmable system. The programmable system includes at least one programmable processor (which may be a special-purpose processor or a general-purpose processor) coupled to receive and transmit data and instructions from and to a storage system, at least one input device, and at least one output device. The computer programs (also known as programs, software, software applications or codes) contain commands for a programmable processor and are stored in a “computer-readable recording medium”.
The computer-readable recording medium includes all types of recording devices in which data readable by a computer system is stored. Such a computer-readable recording medium may be a non-volatile or non-transitory medium, such as ROM, CD-ROM, magnetic tape, floppy disk, memory card, hard disk, magneto-optical disk, or a storage device, and may further include a transitory medium such as a data transmission medium. In addition, the computer-readable recording medium may be distributed in a computer system connected via a network, so that computer-readable codes may be stored and executed in a distributed manner.
Various implementations of systems and techniques described herein may be embodied by a programmable computer. Here, the computer includes a programmable processor, a data storage system (including volatile memory, non-volatile memory, or other types of storage systems, or combinations thereof) and at least one communication interface. For example, the programmable computer may be one of a server, a network device, a set top box, an embedded device, a computer expansion module, a personal computer, a laptop, a personal data assistant (PDA), a cloud computing system, or a mobile device.
Although exemplary embodiments of the present disclosure have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the idea and scope of the claimed invention. Therefore, exemplary embodiments of the present disclosure have been described for the sake of brevity and clarity. The scope of the technical idea of the present embodiments is not limited by the illustrations. Accordingly, one of ordinary skill would understand that the scope of the claimed invention is not to be limited by the above explicitly described embodiments but by the claims and equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2023-0116135 | Sep 2023 | KR | national |
