KR20180034162A - Electro-Mechanical Brake System by using current control and initiating Method thereof - Google Patents

Abstract

An electro-mechanical brake (EMB) system using current control according to an aspect of the present invention comprises: a caliper disposed outside a pad serving as a housing; a disk present between an outer pad and an inner pad and applying a braking force to wheels; the outer pad and the inner pad disposed adjacent to the disk to absorb shock; a head touching the inner pad; a motor connected to a lead screw to adjust the position of the lead screw; and a sensor sensing the number of rotations of the motor. An initialization method for an EMB system using current control comprises the following steps of: applying power to the motor so that the motor can be rotated; measuring current from the applied power; detecting a first number of rotations of the motor corresponding to a current value having the minimum braking force; detecting a second number of rotations of the motor corresponding to a current value having the maximum braking force; mapping the first number of rotations and the second number of rotations with the position of a brake pedal; and blocking the applied power and switching into a drive mode controlling the position of the motor according to the position of the brake pedal in order to apply the braking force. Thus, a safe and efficient EMB system can be provided.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromechanical braking system using a current control,

The present invention relates to an electromechanical brake system using current control and motor control and a method of initializing the same.

In recent years, studies on an electromechanical brake (EMB) system using a motor replacing a hydraulic brake have been actively conducted. In an electromechanical brake system (EMB system), a technique for controlling a motor is required in order to generate a braking force.

The EMB system drives the actuator using a motor according to the position of the brake pedal instead of the hydraulic pressure, and generates the braking force by pushing the head toward the disk.

A sensor is required to control the motor according to the position of the brake pedal, and the sensor may be a Hall sensor or an encoder. However, there is a problem that it is difficult to precisely control the position of the motor by only the sensor, and there is a problem of initializing the reference position of the motor in order to control the position of the motor.

In the EMB initialization method using the current, the EMB system driven by the motor instead of the hydraulic pressure controls the rotation of the motor according to the position of the brake pedal, and the position of the motor is controlled through the information of the hall sensor or the encoder. It is impossible to know the absolute position of the motor when the power is first applied to the EMB system. That is, when the absolute position of the motor is not known, there is a problem that it is difficult to know how much the desired braking force is generated by driving the motor according to the position of the brake pedal.

It is an object of the present invention to provide a safe and efficient EMB system by providing a method of initializing the position of a motor included in an electromechanical brake system in order to replace existing mechanical or hydraulic braking devices with electromechanical brake devices.

A caliper disposed outside the pad serving as a housing according to an aspect of the present invention for achieving the above object; A disk existing between the outer pad and the inner pad and applying a braking force to the wheel; An outer pad and an inner pad which are adjacent to the disk and have a buffering function; A head in contact with the inner pad; A motor connected to the lead screw to adjust the position of the lead screw; And a sensor for sensing the number of revolutions of the motor, the method comprising: applying power to the motor such that the motor rotates; Measuring a current of the applied power source; Detecting a first rotational speed of the motor corresponding to a current value having a minimum braking force; Detecting a second rotational speed of the motor corresponding to a current value having a maximum braking force; Mapping the first rotation speed and the second rotation speed to a position of a brake pedal; And switching to an operation mode for controlling the position of the motor according to the position of the pedal in order to cut off the applied power and apply the braking force.

A caliper on the outside of the pad serving as a housing according to another aspect of the present invention; A disk existing between the outer pad and the inner pad and applying a braking force to the wheel; An outer pad and an inner pad which are adjacent to the disk and have a buffering function; A head in contact with the inner pad; A motor connected to the lead screw to adjust the position of the lead screw; And a sensor for sensing the number of revolutions of the motor, the method comprising: applying power to the motor such that the motor rotates; Measuring a current of the applied power source; Comparing the measured current graph with one or more pre-generated current graphs to map the rotational speed of the motor and the position of the brake pedal; And switching to an operation mode for controlling the position of the motor according to the position of the pedal in order to cut off the applied power and apply the braking force.

According to the present invention, since the existing brake system is replaced with an electro-mechanical brake system (EMB system), it is possible to reduce the weight of the vehicle and precisely control it, thereby improving fuel economy and reducing pollution And helps to implement various and convenient functions.

According to the present invention, it is possible to set the absolute position of the motor by initializing the EMB system using the current, and it is possible to control the motor position according to the position of the brake pedal.

The conventional hydraulic brake system includes a function to compensate for wear of the pad after a certain period of time since the pad is worn according to the use of the brake. However, since the position of the motor is set according to the current value measured in the initialization process according to the present invention, even if the wear of the brake pad occurs, the initialization is performed irrespective of the degree of wear in the initialization process. That is, regardless of the degree of wear of the brake pads, a reference point at which the highest braking force is generated as the pad is worn during system initialization is set, thereby compensating the wear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exemplary diagram illustrating a configuration of a computer system in which an electromechanical brake system initializing method using current control according to the present invention is implemented. FIG.
2 is a schematic diagram of an EMB system applied to a vehicle;
3 is a configuration diagram of an EMB system according to the present invention.
4 is a graph of experimental data for current control of an EMB system according to the present invention.
5 is a flow chart of a method for initializing an electromechanical braking system using current control according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. As used herein, the terms " comprises, " and / or "comprising" refer to the presence or absence of one or more other components, steps, operations, and / Or additions.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is an exemplary diagram illustrating a configuration of a computer system in which an electromechanical brake system initializing method using current control according to the present invention is implemented.

Meanwhile, the electromechanical brake system initializing method using current control according to the embodiment of the present invention can be implemented in a computer system or recorded on a recording medium. 1, a computer system includes at least one processor 110, a memory 120, a user input device 150, a data communication bus 130, a user output device 160, And may include a storage 140. Each of the above-described components performs data communication via the data communication bus 130. [

The computer system may further include a network interface 170 coupled to the network 180. The processor 110 may be a central processing unit (CPU) or a semiconductor device that processes instructions stored in the memory 130 and / or the storage 140.

The memory 120 and the storage 140 may include various forms of volatile or non-volatile storage media. For example, the memory 120 may include a ROM 123 and a RAM 126.

Thus, the method of initializing an electromechanical braking system using current control according to an embodiment of the present invention can be implemented in a computer-executable method. When an electromechanical braking system initialization method using current control according to an embodiment of the present invention is performed in a computer device, computer-readable instructions can perform an operating method according to the present invention.

Meanwhile, the electromechanical brake system initializing method using the current control according to the present invention can be implemented as a computer-readable code on a computer-readable recording medium. The computer-readable recording medium includes all kinds of recording media storing data that can be decoded by a computer system. For example, there may be a ROM (Read Only Memory), a RAM (Random Access Memory), a magnetic tape, a magnetic disk, a flash memory, an optical data storage device and the like. The computer-readable recording medium may also be distributed and executed in a computer system connected to a computer network and stored and executed as a code that can be read in a distributed manner.

2 is a schematic diagram of an EMB system applied to a vehicle.

The vehicle equipped with the EBM system according to the present invention includes a main ECU; One or more EMB ECUs; One or more EMB devices; One or more wheels; And a pedal.

The main ECU 210 transmits a braking signal to each of the EMB ECUs 220 according to the signal of the pedal 240 and the EMB ECU 220 controls the EMB device 200 to move to the wheels 230 Apply braking force to braking.

It is possible to implement more safe and various functions through fast reaction speed and precise control using motor.

Since the EMB ECU 220 is provided separately for each wheel of the vehicle, it has an advantage that the braking force can be applied to each wheel differently, and the braking force applied to each wheel varies depending on the curve length, the uphill road and the downhill road, can do.

3 is a block diagram of the EMB device 200 according to the present invention.

The present invention relates to a method of initializing the initial position of a motor of an electromechanical brake system (EMB system) which is one of automotive electric parts, the EMB system includes an EMB device, FIG.

An EMB device according to a further embodiment of the present invention includes a caliper located outside a pad serving as a housing; A disk existing between the outer pad and the inner pad and applying a braking force to the wheel; An outer pad and an inner pad which are adjacent to the disk and perform a buffering action; A head in contact with the inner pad; A motor connected to the lead screw to adjust the position of the lead screw; And a sensor for sensing the number of revolutions of the motor.

The sensor may be a hall sensor or an encoder.

The motor may be a BLDC motor. When the motor is operated and the head portion of the lead screw contacts the inner pad, the braking force starts to be applied. When the motor further rotates and the head contacts the inner pad as much as possible, do. However, the position where the head is in contact with the inner pads can not be made a slight difference, and the minute difference is caused by the elasticity of the pad, the disk and the head. In order to measure a slight difference, . In the case of the BLDC motor, since the head has a function of decelerating as it comes in close contact with the inner pad, when the reference position is set, the braking force can be controlled by precisely adjusting the position of the lead screw by the number of revolutions of the motor.

In order to obtain the desired braking force, the EMB apparatus moves the head on the lead screw through the rotation of the motor so that the pad presses the disk. When the power is applied, the position of the head may be somewhere on the lead screw, and the head must be moved in the disk direction (inner pad direction) in order to generate a desired braking force. That is, the braking force is generated by adjusting the position of the relative motor that moves the head, and the relative position of the motor can be obtained through the hall sensor or the encoder. However, the absolute value indicating the position of the head can not be obtained with only the Hall sensor and the encoder, and a special method is required to know the absolute position of the head.

In the conventional brake system, the braking force is generated by friction between the head and the disk by using the hydraulic pressure according to the position of the brake pedal. In the EMB system, instead of the hydraulic pressure, the actuator is driven by the motor according to the position of the pedal, Push in the direction of the disk to generate braking force.

In the EMB system, the pressure of the head applied to the disc is adjusted by rotating or reversing the motor according to the position of the brake pedal in order to increase or decrease the braking force. The number of revolutions of the motor according to the position of the brake pedal is an important factor for generating a constant braking force.

The number of revolutions of the motor is measured by using the encoder and the Hall sensor. The encoder and the Hall sensor measure the relative number of revolutions of the motor (forward or reverse), but it is not known which position of the head is on the lead screw. That is, the motor absolute number of revolutions (the absolute position of the motor) in which the reference point exists can not be known.

In order to know the absolute number of revolutions of the motor when power is applied to the system, in order to determine the absolute number of revolutions of the motor so that a constant braking force corresponding to the position of the brake pedal is generated when the power is applied to the system, An initialization process is required to set the location.

4 is a graph of experimental data for current control of the EMB system according to the present invention.

In a typical brake system, there is no load cell that can directly measure braking force. The brittle sensor is a sensor that directly measures the clamping force between the inner pad and the head. Normally, the bite force is used in combination with the braking force in proportion to the braking force. It is not easy to check the braking force numerically on an on-going vehicle because the brittle sensor is expensive and it generates a lot of heat during use and it is difficult to install on a running vehicle.

The method for initializing an electromechanical braking system using current control according to the present invention uses a method of estimating a maximum force (braking force) K that can be generated by a motor in accordance with a current load applied to the motor through a preliminary experiment. That is, a brittle sensor is attached to a preliminary experimental vehicle, and a current value at which the minimum braking force and the maximum braking force are generated is measured by comparing the change of the current value with the change of the bite value. The braking force application condition can be set precisely by mapping the position of the brake pedal.

When power is applied to the BLDC motor as shown in FIG. 4, the current is kept constant for a predetermined time. For example, in FIG. 4, the current value is constant up to around t = 1.977 seconds. From t = 0 to t = 1.977 sec, the motor does not rotate due to the coefficient of static friction of the motor and is in a stopped state. As the current continues to be supplied to the motor, the kinetic friction coefficient of the motor is applied near t = 1.977 seconds. When the motor begins to rotate, the current value begins to decrease and the current value drops to 0.03 A until about t = 3 seconds . After the lead screw contacts the inner pad by the rotation of the motor in the vicinity of t = 3 seconds, the current value begins to increase. The current value increased to 4.00 A during the process of the leadscrew sticking to the inner pad as much as possible, and the maximum fastening force was 20,349 N using a bimodal sensor.

If it is determined that the maximum fastening force is generated, the power supply is stopped and the current value and fastening force are rapidly reduced. From Fig. 4, it can be seen that the time taken to initialize the EMB device from power-on to test completion is within 8 seconds.

After the power is applied, the current data is analyzed and the number of revolutions of the motor when the current value exceeds the first level increases as the motor rotates after the current drops to a small level becomes the minimum braking force reference point. That is, it is set as a reference point at the time when the brake pedal starts to be depressed. For example, the first level may be 0.05 A.

According to FIG. 4, it is experimentally obtained that the maximum clamping force occurs when the average current value for a certain time reaches the third level after the current value exceeds the second level. The second level and the third level are experimentally obtained to know the number of revolutions of the motor in which the maximum clamping force is generated, and predetermined time information for measuring the second level, the third level, will be. For example, referring to FIG. 4, the second level is 3.80 A, the third level is 3.90 A, and the time required to confirm whether the average current value is the third level can be set to 1 second. The power is applied for a predetermined time when the automobile is started by using the predetermined time information for measuring the second level, the third level and the average current value obtained by the preliminary test, and the first rotation of the motor corresponding to the changed current value And the second number of revolutions.

Wherein the third level is greater than the second level and the second level is greater than the first level.

The relative rotation number of the motor can be known by the Hall sensor or the encoder and the relative position of the head part of the lead screw can be known from the relative rotation number of the motor. Therefore, the position of the lead screw when the maximum fastening force is generated (100% operating position of the brake) when the pedal is fully stepped on, as the reference (maximum braking force reference point) as the number of revolutions per minute And maps the pedal position when the pedal starts to be depressed (0% operating position of the brake) with the position (first rotation speed as the relative rotation number of the motor) as the reference (minimum braking force reference point). The position of the brake pedal mapped to the motor reference rotational speed at the upper end of Fig. 4 is indicated at the bottom.

5 is a flow chart of a procedure for initializing an electromechanical braking system using current control according to the present invention.

The motor of the EMB system according to the present invention operates by controlling the number of revolutions of the motor by a Hall sensor or an encoder. However, when the EMB system is initialized after the vehicle is started, . As shown in FIG. 4, when the motor is driven by applying a current for which the maximum target braking force is generated for the first time under the control of the current for a predetermined time, and the brake pedal presses the motor position to the maximum at the time when the motor generates the maximum clamping force Position.

Follow the procedure below.

① Calculate the current upper limit for the target braking force.

② Motor is driven for a certain time by the current value set by current control.

(3) After a predetermined time, the position of the brake pedal is mapped according to the position (number of revolutions) of the motor as shown in FIG. 4 (mapping section A and section B in FIG. 4).

④ When initialization process (reference point setting process) is completed, switch to operation mode

A method of initializing an electromechanical braking system using current control according to the present invention includes: applying power to the motor to rotate the motor; Measuring a current of an applied power supply; Determining whether a predetermined value of the current value is reduced to a value close to a predetermined value and decreasing to a first level or higher; Determining whether the current value is equal to or higher than a second level; Determining whether the average current value is equal to or higher than a third level for a predetermined time period when the current value is equal to or higher than the first level; Setting the number of revolutions of the motor when the average current value is equal to or more than the second level for a predetermined time to a position of a pedal for applying a maximum braking force; And switching to an operation mode for controlling the position of the motor in accordance with the position of the pedal in order to apply the braking force.

In order to practice the present invention, it is necessary to measure the braking force corresponding to the current value changing in advance, and the current graph is generated as the measurement result comparison data. A difference in section between the pad and the head portion is caused when the brake pad is worn due to the use period of the vehicle, the travel distance, the number of brakes used, and the like. EMB apparatus designed to have the axis of the lead screw perpendicular to the pad surface may cause a slight angular difference due to abrasion. Since the EMB apparatus can not recognize such a point before disassembling and repairing the vehicle, The shape of the current graph may differ. Various current graph forms can be generated under various environmental conditions, and the current graph form is similar if the wear states are similar. Since the measured current graph may differ depending on the use of the vehicle, it is necessary to generate the current graph under various conditions.

Generally, one or more current graphs as shown in FIG. 4 are generated in advance by varying the period of use, the travel distance, and the number of times of using the brakes. By comparing the measured current graph shape with the previously generated current graph, By mapping the number of revolutions of the motor and the position of the brake pedal as a reference, the EMB system can be initialized more suited to the state of the vehicle.

If there is no similarity between the measured current graph and the previously generated current graph, then there may be a problem with the current EMB device. Select the most similar current graph, classify the normal level, warning level, and risk level according to the level of similarity, and if warning level, output warning message, but if warning level, warning message is displayed So that the safe driving of the vehicle user can be promoted.

The method of comparing the similarity of the current graph can utilize various statistical techniques. However, the measured current value is maintained at a constant value according to time t, 2) a process in which the held current value falls to a value close to 0 A, 3) a process in which the current value rises again, 4) The process of decreasing the current value by stopping the power supply is performed in the order of decreasing the current value and the step 3) of the above process is most important as the interval for mapping the number of revolutions of the motor and the position of the brake pedal. After dividing, the scale is adjusted, and the time scale of the current graph part corresponding to step 3) is matched, and then the current value is compared.

For example, an adaptation-rejection test method, which is a distribution test method, can be used statistically. In the present invention, since the mechanical structure of the EMB device and the absolute value of the current depending on the BLDC motor are important, only the scale adjustment of the time interval is performed. And the scale is not adjusted for the current value. That is, since the normalization process is not performed, the problem of including most of the curve to be compared occurs, so that the adoption-rejection test method can be calculated in both directions and the similarity degree can be determined by multiplying the calculated area ratio.

Specifically, a first area ratio including a currently measured current value change graph is calculated based on a previously measured current value change graph, and a current value change graph including a pre-measured current value change graph based on the currently measured current value change graph The second area ratio can be calculated, and the degree of similarity can be calculated as the product of the first area ratio and the second area ratio. After calculating the similarity for all of the graphs of the current values measured in one or more dictionaries, time information for measuring the second level, the third level, and the average current value of the current values is extracted using the current value variation graph having the greatest similarity . However, the safety level, the warning level, and the risk level are classified according to the value calculated with the greatest similarity as described above. In the case of the warning level, a warning message is outputted and the operation is allowed. The message is printed and can not be operated. If the level of similarity is at a dangerous level, it may be a problem with the EMB device, so that the safety inspection of the EMB device may be performed to enable the safe driving of the vehicle user.

The embodiments of the present invention are not limited to the above-described apparatuses and / or methods, but may be implemented through a program for realizing functions corresponding to the configuration of the embodiment of the present invention, a recording medium on which the program is recorded And such an embodiment can be easily implemented by those skilled in the art from the description of the embodiments described above.

While the present invention has been described in detail with reference to the accompanying drawings, it is to be understood that the invention is not limited to the above-described embodiments. Those skilled in the art will appreciate that various modifications, Of course, this is possible. Accordingly, the scope of protection of the present invention should not be limited to the above-described embodiments, but should be determined by the description of the following claims.

100: Computer system
110: Processor
120: Memory
123: ROM
126: RAM
130: Data communication bus
140: Store
150: User input device
160: User output device
170: Network interface
180: Network
200: EMB ECU
210: main ECU
220: EMB
230: Wheels
240: Pedal
310: caliper
320: outer pad
330: disk
340: Inner pad
350: Head
360: Lead screw
370: Motor
380: Sensor

Claims (7)

A caliper on the outside of the pad serving as a housing; A disk existing between the outer pad and the inner pad and applying a braking force to the wheel; An outer pad and an inner pad which are adjacent to the disk and have a buffering function; A head in contact with the inner pad; A motor connected to the lead screw to adjust the position of the lead screw; And a sensor for sensing the number of revolutions of the motor, the method comprising the steps of:
Power is applied to the motor to rotate the motor;
Measuring a current of the applied power source;
Detecting a first rotational speed of the motor corresponding to a current value having a minimum braking force;
Detecting a second rotational speed of the motor corresponding to a current value having a maximum braking force;
Mapping the first rotation speed and the second rotation speed to a position of a brake pedal;
Switching to an operation mode for controlling the position of the motor according to the position of the pedal in order to cut off the applied electric power and apply the braking force;
Wherein said step of controlling said electromechanical braking system comprises the steps of: The method according to claim 1,
Wherein the measured current value
2) the process of keeping the current value close to 0 A, 3) the process of the current value rising again, 4) if the current value reaches the maximum value, the power supply is stopped and the current value And a process of decreasing the temperature of the fuel cell,
Wherein the first rotation number
The current value is the number of revolutions of the motor when it exceeds the first level in the process of rising again,
Wherein the second rotation number
Which is the number of revolutions of the motor when the average current value for a predetermined time reaches the third level after exceeding the second level in the process of raising the current value again
Method of initializing an electromechanical braking system using inrush current control.
The method according to claim 1,
Wherein the mapping comprises:
Maps the first number of revolutions to the 0% operating position of the brake,
Mapping the second number of revolutions to a 100% operating position of the brake
Method of initializing an electromechanical braking system using inrush current control.
A caliper on the outside of the pad serving as a housing; A disk existing between the outer pad and the inner pad and applying a braking force to the wheel; An outer pad and an inner pad which are adjacent to the disk and have a buffering function; A head in contact with the inner pad; A motor connected to the lead screw to adjust the position of the lead screw; And a sensor for sensing the number of revolutions of the motor, the method comprising the steps of:
Power is applied to the motor to rotate the motor;
Measuring a current of the applied power source;
Comparing the measured current graph with one or more pre-generated current graphs to map the rotational speed of the motor and the position of the brake pedal;
Switching to an operation mode for controlling the position of the motor according to the position of the pedal in order to cut off the applied power and apply the braking force;
Wherein said step of controlling said electromechanical braking system comprises the steps of:
5. The method of claim 4,
The pre-generated current graph may include:
A current graph considering anticipated wear for each service period, a current graph considering anticipated wear for each travel distance, and a current graph considering anticipated wear due to a brake usage amount.
Wherein the mapping comprises:
Comparing the measured current graph with the one or more pre-generated current graphs to select a graph most similar to the measured current graph among the pre-generated current graphs, extracting a reference number of rotations of the motor from the selected graph And maps the rotational speed of the motor on the measured current graph corresponding to the reference rotational speed of the motor to the position of the brake pedal
Method of initializing an electromechanical braking system using current control.

6. The method of claim 5,
The method of selecting the most similar graph comprises:
The scale is adjusted for each corresponding section on the time axis,
For the section from the time when the minimum braking force is generated to the time when the maximum braking force is generated, the ratio of the overlapping area between the previously generated current graph and the measured current graph is calculated in both directions to select the most similar graph Characterized by
Method of initializing an electromechanical braking system using current control.
6. The method of claim 5,
Wherein the mapping comprises:
And outputting an initialization failure warning message when the graphs most similar to the measured current graph are not similar among the pre-generated current graphs
Method of initializing an electromechanical braking system using current control.

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