Electromagnet control mode for parking mechanism of electromechanical brake

Abstract

An electromagnet control mode for an electronic mechanical brake parking mechanism comprises the following steps that S1, after a parking / releasing instruction is sent out, the real-time temperature of an electromagnet is estimated, and the real-time resistance of an electromagnet coil is calculated; s2, ideal driving current is obtained, the net driving force is larger than the minimum value, and target driving voltage is calculated; s3, if the target driving voltage is smaller than the working voltage of the power supply, PWM is used for adjusting the duty ratio to control an electromagnet driving power supply, and an equivalent target driving voltage is obtained; s4, the electromagnet works under the target driving voltage, the parking mechanism is driven to be locked or released, and the net driving force is larger than the minimum value; and S5, after the parking / releasing action is completed, judging whether the parking / releasing action is successful or not based on the stroke of the motor, if so, ending the whole process, and if not, properly increasing (during locking) or reducing (during releasing) the target driving voltage, and repeating the parking / releasing action. According to the electromagnet control mode for the parking mechanism of the electronic mechanical brake, impact and noise generated when the parking electromagnet is locked and released are reduced.

Description

Technical Field

[0001] The present invention belongs to the field of wire control braking systems, and particularly relates to an electromagnetic control method for a parking mechanism of an electromechanical brake. Background Art

[0002] In the field of wire control braking systems, an electromechanical brake (EMB, Electro Mechanical Brake) realizes braking by driving a mechanical actuator with a motor. Most of the existing EMBs achieve the electronic parking function through an integrated parking mechanism, and the driving of locking and releasing of the parking mechanism is generally driven by an electromagnet.

[0003] Ideally, the electromagnetic thrust of the electromagnet should be slightly higher than the system resistance. At this time, the working process of the electromagnet is stable and the system impact is minimized. The electromagnetic force of the electromagnet is proportional to the product of the current of the electromagnet coil and the number of coil turns, that is, ampere-turn. Therefore, the electromagnet can obtain a relatively accurate electromagnetic force by being driven by a constant current source. Currently, the parking electromagnets of EMBs are all powered and driven by a vehicle-mounted power supply, which is an atmospheric pressure power supply. On the other hand, the working temperature range of the electromagnet is usually between -40 and 120, and the coil resistance is affected by temperature, resulting in that when driven by an atmospheric pressure power supply, the working current of the electromagnet will vary with temperature, that is, the electromagnetic force varies with temperature, but the system resistance (permanent magnet suction force, return spring force, friction force, etc.) usually varies little with temperature.

[0004] In order to ensure that the parking mechanism can work normally in all working temperature ranges, usually the design of the parking electromagnet is considered based on the maximum working temperature. At this time, the resistance value of the electromagnet coil is the largest and the electromagnetic force is the smallest; the consequent problem is that at normal temperature and low temperature, the electromagnetic force of the electromagnet is overly redundant, and large impact and noise will be generated during driving or releasing.

[0005] Therefore, it is of practical significance to develop an electromagnetic control method for the electromagnet that can effectively reduce the parking and releasing noise. Summary of the Invention

[0006] Object of the Invention: To overcome the above deficiencies, the object of the present invention is to provide an electromagnetic control method for a parking mechanism of an electromechanical brake, which is reasonably designed and can achieve precise control of the driving force of the electromagnet without adding hardware, thereby effectively reducing the impact and noise during the parking / releasing process and having a wide application prospect.

[0007] The object of the present invention is achieved by the following technical solutions: An electromagnetic control method for a parking mechanism of an electromechanical brake, comprising the following steps: S1: After the parking / release instruction is issued, read the temperature signal to estimate the real-time temperature of the electromagnet, and calculate the real-time resistance of the electromagnet coil according to the metal resistivity-temperature relationship formula. S2: Obtain the ideal driving current through electromagnetic simulation or actual measurement, so that the net driving force is greater than a preset minimum value. Based on the real-time coil resistance and the ideal driving current, calculate the target driving voltage. S3: When the target driving voltage is less than the power supply operating voltage, control the electromagnet driving power supply based on the PWM method of adjusting the duty cycle to obtain an equivalent target driving voltage. S4: Make the electromagnet work at the target driving voltage to drive the parking mechanism to lock or release. At this time, the net driving force is greater than the preset minimum value. S5: After the parking / release action is completed, judge whether the parking / release action is successful based on the motor stroke. If it is successful, the whole process ends; if the parking action fails, increase the target driving voltage; if the release action fails, decrease the target driving voltage, and repeat the parking / release action.

[0008] Furthermore, for the above-mentioned electromagnet control method for the parking mechanism of the electromechanical brake, in S1, the real-time temperature of the electromagnet is estimated by reading the temperature signal of the chip or the temperature sensor.

[0009] The real-time temperature of the electromagnet is estimated by reading the temperature signal of PCBA chips such as the MCU or the power management chip or the temperature sensor. Most chips have temperature measurement and temperature signal reading functions. At the same time, some designs will add additional temperature sensors on the PCBA. Therefore, the temperature can be read from the chip or the temperature sensor.

[0010] Preferably, based on the temperature signals of multiple chips or temperature sensors, logical operations are performed to estimate the real-time temperature of the electromagnet.

[0011] The above design can obtain a more accurate estimated value of the real-time temperature of the electromagnet.

[0012] Furthermore, for the above-mentioned electromagnet control method for the parking mechanism of the electromechanical brake, in S1, the metal resistivity-temperature relationship formula is as follows: ; In the formula, is the coil resistance at temperature, is the resistivity at 0 degrees, is the resistance temperature coefficient of the coil wire, is the length of the coil wire, is the cross-sectional area of the coil.

[0013] Further, for the electromagnetic control method of the parking mechanism of the electromechanical brake, when locking, the net driving force expression is as follows: ; When releasing, the net driving force expression is as follows: ; In the formula, is the net driving force, is the electromagnetic force, is the return force, and f is the system comprehensive friction force.

[0014] Further, for the electromagnetic control method of the parking mechanism of the electromechanical brake, when the parking mechanism locks or releases, is greater than 0, and the parking system can work normally. At the same time, the smaller it is, the smaller the impact noise of the parking system is.

[0015] Further, for the electromagnetic control method of the parking mechanism of the electromechanical brake, in S2, the formula for calculating the target drive voltage is as follows: ; In the formula, is the target drive voltage at is the ideal drive current, is the coil resistance at

[0016] Further, for the electromagnetic control method of the parking mechanism of the electromechanical brake, in S2 and S4, the minimum value approaches 0.

[0017] Further, for the electromagnetic control method of the parking mechanism of the electromechanical brake, the electromagnet is a monostable parking electromagnet, including a push rod, a housing, a return spring, a static iron core, a moving iron core, a coil, and a coil skeleton; when the electromagnet is energized, an attractive force is generated between the static iron core and the moving iron core, and the moving iron core drives the push rod to move forward to push the parking mechanism to lock. At this time, collisions occur between the push rod and the driven part, and between the moving iron core and the static iron core; when releasing, the return spring pushes the moving iron core and the static iron core to separate, and collisions occur between the moving iron core, the static iron core and the coil skeleton.

[0018] Further, the electromagnetic control method for the parking mechanism of the electromechanical brake described above is not only applicable to the parking electromagnet in the wire control braking system, but also can be applied to other fields that require precise control of electromagnetic force (such as industrial automation, robots, etc.).

[0019] The electromagnetic control method of the present invention has universality and can be widely applied to various scenarios.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) The electromagnet control method for the parking mechanism of the electro-mechanical brake disclosed by the present invention estimates the electromagnet temperature in real time and adjusts the driving voltage to ensure the stability of the electromagnetic force at different temperatures, solves the problem of the electromagnetic force fluctuating with temperature in the prior art, and improves the reliability and stability of the system. For example, in extremely high or low temperature environments, this mechanism can ensure the stability of the electromagnetic force and enable the system to operate normally; (2) The electromagnet control method for the parking mechanism of the electro-mechanical brake disclosed by the present invention precisely controls the driving voltage of the electromagnet, making the net driving force slightly greater than zero, reducing the impact and noise during the locking and releasing processes, solves the related problems caused by excessive surplus of the electromagnetic force in the prior art, and significantly improves the user experience; (3) The electromagnet control method for the parking mechanism of the electro-mechanical brake disclosed by the present invention has an adaptive control ability. Its control method can adaptively adjust the driving voltage according to the real-time temperature signal to ensure precise control of the electromagnet under different working environments, and guarantees the adaptability and accuracy of the system in complex and changeable environments; (4) The electromagnet control method for the parking mechanism of the electro-mechanical brake disclosed by the present invention realizes energy conservation and efficiency improvement. Precisely controlling the driving voltage avoids excessive surplus of the electromagnetic force, reduces unnecessary energy consumption, meets the current energy conservation and emission reduction requirements of the automotive industry, can reduce the vehicle energy consumption in the long term, and improves the energy utilization efficiency; (5) The electromagnet control method for the parking mechanism of the electro-mechanical brake disclosed by the present invention has a fault detection and fault tolerance function. After the parking / release action is completed, it judges whether the action is successful through the motor stroke. If it fails, it adjusts the driving voltage and repeats the action, improves the fault tolerance ability of the system, ensures the reliability of the parking / release action, and further improves the safety and stability of the system; (6) The electromagnet control method for the parking mechanism of the electro-mechanical brake disclosed by the present invention does not add hardware, and realizes precise control of the electromagnet driving force through the processing of the signals of existing chips and sensors, and has high practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram when the electromagnet of the electromagnet control method for the parking mechanism of the electro-mechanical brake described in the present invention is energized; Figure 2 is a schematic structural diagram when the electromagnet of the electromagnet control method for the parking mechanism of the electro-mechanical brake described in the present invention is released; Figure 3 is a parking locking flowchart of the electromagnet control method for the parking mechanism of the electro-mechanical brake described in the present invention; Figure 4The parking release flow chart for the electromagnetic control mode of the parking mechanism of the electro-mechanical brake described in the present invention; In the figure: push rod 1, housing 2, return spring 3, static iron core 4, moving iron core 5, coil 6, coil skeleton 7. Specific implementation mode

[0022] Next, Example 1 will be combined with the attached Figure 1 、 2 、3, 4 and specific experimental data to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention. The following Example 1 provides an electromagnetic control mode for the parking mechanism of an electro-mechanical brake.

[0023] Example 1 As Figure 1 、 2 described, a typical monostable parking electromagnet includes a push rod 1, a housing 2, a return spring 3, a static iron core 4, a moving iron core 5, a coil 6, and a coil skeleton 7.

[0024] As Figure 1 shown, when the electromagnet is energized, an attractive force is generated between the static iron core 4 and the moving iron core 5, and the moving iron core 5 drives the push rod 1 to move forward to lock the parking mechanism. At this time, there will be collisions between the push rod 1 and the driven part, and between the moving iron core 5 and the static iron core 4.

[0025] As Figure 2 shown, when releasing, the return spring 3 pushes the moving iron core 5 to separate from the static iron core 4. At this time, a collision occurs between the iron core and the coil skeleton 7.

[0026] When locking, the expression of the net driving force is as follows: ; When releasing, the expression of the net driving force is as follows: ; In the formula, is the net driving force; is the electromagnetic force, the magnitude of which is proportional to the current of the electromagnet coil; is the return force, generally the spring force or the attractive force of the permanent magnet, and its magnitude is little affected by the working environment; f is the system comprehensive friction force, and its value is usually very small.

[0027] When the parking mechanism locks or releases, is greater than 0, and the parking system can work normally. At the same time The smaller it is, the smaller the impact noise of the parking system.

[0028] As Figure 3 , 4 shown, the electromagnetic control method for the parking mechanism of the electromechanical brake in Embodiment 1 specifically includes the following steps: S1: After the parking / release command is issued, read the temperature sensor signal of the chip to estimate the real-time temperature of the electromagnet, and calculate the real-time resistance of the electromagnet coil according to the metal resistivity-temperature relationship formula. The metal resistivity-temperature relationship formula is as follows: ; In the formula, is the coil resistance at is the resistivity at 0 degrees, is the temperature coefficient of resistance of the coil wire, is the length of the coil wire, is the cross-sectional area of the coil; Preferably, certain logical operations can be performed based on the temperature signals of multiple chips or temperature sensors to obtain a more accurate estimated value of the real-time temperature of the electromagnet. S2: Obtain the ideal drive current through electromagnetic simulation or actual measurement, so that the net driving force is greater than a preset minimum value (the minimum value approaches 0). Based on the real-time coil resistance and the ideal drive current, calculate the target drive voltage. The formula for calculating the target drive voltage is as follows: ; In the formula, is the target drive voltage at is the ideal drive current, is the coil resistance at S3: When the target drive voltage is less than the power supply operating voltage, control the electromagnet drive power supply by adjusting the duty cycle based on PWM to obtain an equivalent target drive voltage. S4: Make the electromagnet work at the target drive voltage, drive the parking mechanism to lock or release. At this time, the net driving force is greater than a preset minimum value (the minimum value approaches 0), the electromagnet works smoothly, and the impact and noise of the parking system are minimized. S5: After the parking / release action is completed, judge whether the parking / release action is successful based on the motor stroke. If it is successful, the whole process ends; otherwise, appropriately increase (when locking) or decrease (when releasing) the target drive voltage, and repeat the parking / release action.

[0029] In summary, by adopting the technical solution of the present invention, precise control of the driving force of the electromagnet is achieved without adding hardware, thereby effectively reducing the impact and noise during the parking / release process.

[0030] The specific application scenarios of the present invention are numerous. The above description is only the preferred implementation mode of the present invention. It should be noted that the above embodiments are only used to illustrate the present invention and do not limit the protection scope of the present invention. For those of ordinary skill in the art in this technical field, several improvements can be made without departing from the principle of the present invention, and these improvements should also be regarded as within the protection scope of the present invention.

Claims

1. An electromagnet control method for an electromechanical brake parking mechanism, characterized in that: The steps include: S1: After the parking / release command is issued, the temperature signal is read to estimate the real-time temperature of the electromagnet, and the real-time resistance of the electromagnet coil is calculated according to the metal resistivity-temperature relationship formula; S2: Obtain an ideal driving current through electromagnetic simulation or actual measurement so that the net driving force is greater than a preset minimum value, and calculate the target driving voltage based on the real-time resistance of the coil and the ideal driving current; S3: When the target driving voltage is less than the power supply working voltage, the electromagnet driving power supply is controlled by adjusting the duty cycle based on PWM to obtain an equivalent target driving voltage; S4: The electromagnet is operated at the target driving voltage to drive the parking mechanism to lock or release. At this time, the net driving force is greater than the preset minimum value; S5: After the parking / release action is completed, it is determined whether the parking / release action is successful based on the motor stroke. If successful, the whole process ends; if the parking action fails, the target drive voltage is increased; if the release action fails, the target drive voltage is reduced and the parking / release action is repeated.

2. The electromagnet control method for an electromechanical brake parking mechanism according to claim 1, characterized in that: In S1, the real-time temperature of the electromagnet is estimated by reading the temperature signal of the chip or the temperature sensor.

3. The electromagnet control method for an electronic mechanical brake parking mechanism according to claim 1, characterized in that: In S1, the metal resistivity-temperature relationship formula is as follows: ; In the formula, for Coil resistance at temperature, is the resistivity at 0 degrees, is the resistance temperature coefficient of the coil wire, is the coil wire length, is the cross-sectional area of ​​the coil.

4. The electromagnet control method for an electronic mechanical brake parking mechanism according to claim 1, characterized in that: When locked, the net driving force is expressed as follows: ; When released, the net driving force expression is as follows: ; In the formula, is the net driving force, is the electromagnetic force, is the return force, and f is the comprehensive friction force of the system.

5. The electromagnet control method for an electronic mechanical brake parking mechanism according to claim 4, characterized in that: When the parking mechanism is locked or released, If it is greater than 0, the parking system can work normally. The smaller it is, the less impact noise the parking system will produce.

6. The electromagnet control method for an electronic mechanical brake parking mechanism according to claim 1, characterized in that: In S2, the formula for calculating the target driving voltage is as follows: ; In the formula, for Target drive voltage at temperature, is the ideal driving current, for Coil resistance at temperature.

7. The electromagnet control method for an electronic mechanical brake parking mechanism according to claim 1, characterized in that: In S2 and S4, the minimum value approaches 0.

8. The electromagnet control method for an electronic mechanical brake parking mechanism according to claim 1, characterized in that: The electromagnet is a monostable parking electromagnet, comprising a push rod (1), a housing (2), a return spring (3), a static iron core (4), a moving iron core (5), a coil (6), and a coil frame (7); when the electromagnet is energized, an attractive force is generated between the static iron core (4) and the moving iron core (5), and the moving iron core (5) drives the push rod (1) to move forward, pushing the parking mechanism to lock, and at this time, a collision is generated between the push rod (1) and the driven part, and between the moving iron core (5) and the static iron core (4); when released, the return spring (3) pushes the moving iron core (5) and the static iron core (4) to separate, and a collision is generated between the moving iron core (5), the static iron core (4), and the coil frame (7).

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