Brake-by-wire system vehicle static braking limit control method and device and vehicle

Abstract

The invention discloses a brake-by-wire system vehicle static braking limit control method and device and a vehicle, and belongs to the technical field of vehicles. The method comprises the steps that under the condition that the vehicle speed is smaller than a low-speed threshold value, the vehicle state is obtained; determining a gradient of a brake torque change according to the vehicle state; and vehicle control is conducted according to the gradient of the brake torque change. When the vehicle is in a low-speed and static state, in order to enable a driver to have better NVH experience and reduce the electric energy consumption of the whole vehicle, on the premise that unexpected vehicle sliding of the vehicle is avoided, the over-high braking torque request of the vehicle in the low-speed and static state is limited so as to reduce the electric energy consumption of the whole vehicle; meanwhile, the brake increasing and releasing torque gradient is limited, and the working rotating speed of the brake-by-wire motor is reduced so as to reduce the brake noise.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of vehicles, and particularly relates to a brake-by-wire system vehicle static braking limiting control method, device and vehicle. BACKGROUND

[0002] Currently, new energy vehicles mostly adopt brake-by-wire systems, and the brake-by-wire motors are powered by the whole vehicle to provide braking assistance. New energy vehicles adopt electric drive systems, and the vehicle environment is relatively quiet at low speed and at rest. Since the vehicle also needs to be braked at rest to prevent the vehicle from rolling, if the braking torque is too high at low speed and at rest, a large noise will be generated and the normal power consumption will be increased. SUMMARY

[0003] An object of the present application is to provide a brake-by-wire system vehicle static braking limiting control method, device and vehicle, which can solve the technical problem of generating a large noise and increasing normal power consumption due to a too high braking torque at low speed and at rest in the prior art.

[0004] According to a first aspect of the present application, a brake-by-wire system vehicle static braking limiting control method is provided, comprising: obtaining a vehicle state when the vehicle speed is less than a low speed threshold value; determining a gradient of braking torque change according to the vehicle state; controlling the vehicle according to the gradient of braking torque change.

[0005] Optionally, the determining of the gradient of braking torque change according to the vehicle state comprises: determining a target deceleration when the vehicle is in braking; when the brake pedal force reaches a preset target, the braking capacity is increased to a normal braking level; when the brake pedal force does not reach the preset target, determining a gradient of braking torque increase according to a first limiting condition and the target deceleration, wherein the first limiting condition is that the braking time is less than a first preset time.

[0006] Optionally, the determining of the gradient of braking torque increase according to the first limiting condition and the target deceleration comprises: determining a maximum value of the gradient of braking torque increase according to the target deceleration and the first limiting condition; determining the gradient of braking torque increase according to the maximum value of the gradient of braking torque increase and a first coefficient set in advance.

[0007] Optionally, the determining of the gradient of braking torque change according to the vehicle state comprises: determining a target acceleration when the vehicle is in a state of starting release braking; determining a gradient of braking torque reduction according to a second limit condition and the target acceleration, wherein the second limit condition is that a time of releasing braking is less than a second preset time.

[0008] Optionally, the determining of the gradient of braking torque reduction according to the second limit condition and the target acceleration comprises: determining a minimum value of the gradient of braking torque reduction according to the target acceleration and the second limit condition; determining the gradient of braking torque reduction according to the minimum value of the gradient of braking torque reduction and a second preset coefficient.

[0009] Optionally, the determining of the gradient of braking torque change according to the vehicle state comprises: in a case that no wheel speed change is detected within a target time, limiting a braking torque intensity of the vehicle to a braking torque intensity value of a preset static braking limit function, and limiting a gradient of braking torque increase of the vehicle to a gradient value of braking torque increase of the preset static braking limit function.

[0010] Optionally, the method further comprises: in a case that vehicle movement is detected during the parking limiting process, using a higher braking intensity limit value until the next power-on restart of the vehicle to prevent vehicle rolling; if vehicle movement is detected again, using a regular braking before the next power-on restart of the vehicle, and disabling the static braking limit function of the vehicle.

[0011] Optionally, the method further comprises: in a case that a wheel speed signal of the vehicle is detected to be faulty, disabling the static braking limit function of the vehicle.

[0012] According to a second aspect of the present application, an electronic device is provided, comprising a processor and a memory, the memory storing programs or instructions executable on the processor, the programs or instructions being executed by the processor to implement the steps of the vehicle static braking limit control method of the line control braking system according to the first aspect of the present application.

[0013] According to a third aspect of the present application, a vehicle is provided, comprising an electronic device according to the second aspect of the present application.

[0014] The application has the beneficial effect that the application is used to limit the high brake torque request of the vehicle at low speed and static state to reduce the vehicle electric energy consumption, to improve the NVH experience of the driver and to avoid the unintended vehicle rolling, and to limit the brake increase and release torque gradient and to reduce the brake motor working speed to reduce the brake noise. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a flow chart of the vehicle static brake limiting control method of the application. DETAILED DESCRIPTION

[0016] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of the components and steps, numerical expressions, and numerical values set forth in these embodiments are not limiting to the scope of the present application unless otherwise specifically stated.

[0017] The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the scope of the application its application or uses.

[0018] Techniques, methods, and devices known to those of ordinary skill in the relevant art can not be discussed in detail herein. However, where appropriate, such techniques, methods, and devices can be viewed as part of the specification and can form part of the present application. In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as a limitation of the application. Thus, other examples of the exemplary embodiments can have different values.

[0019] It should be noted that like reference numerals and letters in the various figures indicate similar items, and, thus, where appropriate, reference numerals and letters in one figure can be discussed with respect to other figures if they appear therein.

[0020] In the description of the application, the features related to the terms "first", "second" can be explicitly or implicitly included one or more of the features. In the description of the application, unless otherwise specified, the meaning of "a plurality of" is two or more. In addition, "and / or" in the specification means at least one of the connected objects, and the character " / ", generally means that the front and rear associated objects are in an "or" relationship.

[0021] As shown in Figure 1 The embodiment introduces a vehicle static brake limiting control method of the brake-by-wire system, including steps 1100-1300.

[0022] Step 1100: Obtain the vehicle state when the vehicle speed is less than the low speed threshold.

[0023] When the vehicle speed is less than a low-speed threshold, a static brake limiting function of the vehicle is started to limit the brake torque and a gradient of change of the brake torque when the vehicle is at a low speed. Meanwhile, the safety concept requirements also need to be met to prevent the occurrence of the vehicle sliding. When the vehicle is stationary, the braking strength specified by the regulations should be ensured, such as not being lower than 6.43 m / s 2 level corresponding to 500 N. The low-speed threshold can be set to 2 km / h, and when the vehicle speed is less than 2 km / h, the static brake limiting function of the vehicle is started.

[0024] Step 1200: determining a gradient of change of brake torque according to the vehicle state.

[0025] The gradient of change of brake torque includes a gradient of increase of brake torque and a gradient of decrease of brake torque. The gradient of change of brake torque is used to reflect the rate of increase or decrease of brake torque change, and a gentle gradient means slow torque change.

[0026] The vehicle state includes applying brake and releasing brake, and the time of applying brake and the time of releasing brake are specified in the relevant regulations. The gradient of change of brake torque will affect the time of applying brake and the time of releasing brake, so the gradient of change of brake torque is determined according to the vehicle state, so that the time of applying brake and the time of releasing brake meet the relevant regulations and safety is ensured.

[0027] Step 1300: vehicle control according to the gradient of change of brake torque.

[0028] After determining the gradient of change of brake torque, the torque is controlled according to the gradient of change of brake torque.

[0029] The application is used to limit the high brake torque request of the vehicle at low speed and stationary state to reduce the vehicle electric energy consumption, avoid the occurrence of unexpected vehicle sliding, limit the brake increase and release torque gradient, reduce the working speed of the brake-by-wire motor to reduce the brake noise, and provide the driver with better NVH (Noise, Vibration, Harshness) experience.

[0030] In this embodiment, step 1200 includes steps 1210-1230.

[0031] Step 1210: determining a target deceleration when the vehicle is in the state of applying brake.

[0032] Step 1220: when the brake pedal force reaches the preset target, the brake capacity is increased to the conventional brake level.

[0033] Step 1230: When the brake pedal force does not reach the preset target, determine the gradient of the increase in braking torque according to the first limiting condition and the target deceleration, wherein the first limiting condition is that the braking time is less than the first preset time.

[0034] When a braking request is received, the vehicle is considered to be in a braking state. If the brake pedal force reaches a preset target, such as close to 500N, it indicates that the driver's braking request is relatively strong and a collision may be imminent. In this case, braking cannot be restricted, and conventional braking methods should be used to avoid a collision.

[0035] If the brake pedal force does not reach the preset target, it indicates that there is no significant braking demand. In this case, noise can be reduced by limiting the braking gradient. Relevant regulations limit the time for vehicle braking, requiring it not to exceed a certain time, i.e., a first preset time, to prevent accidents caused by delayed braking. For example, the first preset time is 600ms. If the gradient of braking torque change is set unreasonably, it will lead to the vehicle applying brakes for too long, exceeding the relevant regulations.

[0036] The target deceleration can be determined based on the braking request. The time required for the vehicle to apply braking is the time needed to reach the target deceleration. The braking time is related to the target deceleration and the gradient of the braking torque increase. The greater the target deceleration, the longer the braking time will be. For example, to apply a relatively large deceleration of 10 m / s²... 2 If using 28m / s 3 The gradient is expected to be applied in 350ms, which is lower than the regulatory requirement of 600ms and meets the requirements.

[0037] Specifically, step 1230 includes: determining the maximum value of the gradient of the increase in braking torque based on the target deceleration and the first constraint; and determining the gradient of the increase in braking torque based on the maximum value of the gradient of the increase in braking torque and a pre-set first coefficient.

[0038] When braking is applied at the maximum value of the gradient of increasing braking torque, the braking time required to reach the target deceleration is the first preset time.

[0039] Braking is applied by a brushless motor. The larger the gradient, the slower the motor speed and the lower the noise. To improve the driving experience and reduce noise, theoretically, within the legally required range, the larger the gradient of braking torque increase, the better. If minimizing noise is the primary goal, then the maximum value of the braking torque increase gradient should be selected for braking. However, in real-world scenarios, using the maximum value of the braking torque increase gradient may cause the braking time to exceed the first preset time due to various unforeseen circumstances, thus affecting driving safety.

[0040] To address this issue and minimize noise while ensuring safety, this embodiment sets a first coefficient. The gradient of the increase in braking torque is calculated based on the first coefficient and the maximum value of the gradient of the increase in braking torque. When braking is applied using this calculated gradient of the increase in braking torque, the braking time is less than a first preset time, for example, 90% of the first preset time, with the remaining 10% reserved to handle possible unexpected situations.

[0041] This approach ensures that, in the event of an emergency, the braking time complies with relevant regulations, thus guaranteeing driving safety. Furthermore, it minimizes braking noise and enhances the driving experience.

[0042] In this embodiment, step 1200 includes steps 1230-1240.

[0043] Step 1230: Determine the target acceleration when the vehicle is in the state of starting and releasing the brake.

[0044] Step 1240: Determine the gradient of the reduction in braking torque based on the second constraint and the target acceleration, wherein the second constraint is that the time to release the brake is less than a second preset time.

[0045] Regarding brake release, relevant regulations also stipulate the time required for brake release, requiring it to be less than a certain time, namely a second preset time, to prevent delayed brake release. If the gradient of braking torque change is not set appropriately, it can lead to excessively long brake release time, exceeding the regulations. The brake release time is also related to the gradient of braking torque change. By limiting the gradient of braking torque change, the brake release time is ensured to comply with regulations.

[0046] Specifically, step 1240 includes: determining the minimum value of the gradient of the reduction of braking torque based on the target acceleration and the second constraint; and determining the gradient of the reduction of braking torque based on the minimum value of the gradient of the reduction of braking torque and a pre-set second coefficient.

[0047] When control is applied based on the maximum value of the braking torque reduction gradient, the brake release time required to reach the target acceleration is a second preset time. To minimize noise while ensuring safety, a second coefficient is set in this embodiment. The braking torque reduction gradient is calculated based on this second coefficient and the maximum value of the braking torque reduction gradient. When control is applied based on this calculated braking torque reduction gradient, the brake release time is less than the second preset time, with the excess used to handle potential unforeseen circumstances.

[0048] In this embodiment, step 1200 includes: if no wheel speed change is detected within the target time, limiting the braking torque intensity of the vehicle to the braking torque intensity value of the preset static braking limit function, and limiting the gradient of the increase in the braking torque of the vehicle to the gradient value of the increase in the braking torque of the preset static braking limit function.

[0049] If the wheel speed remains unchanged within a certain time, it indicates that the vehicle is in a safe stationary state. This means the vehicle has been completely stationary for a period of time; for example, even if there is a tendency to roll backward on a slope, it is suppressed by the system, and the wheel speed is 0. The braking torque intensity value of the static braking limiting function can meet the braking requirements of the vehicle in a safe stationary state, for example, it can be 7 m / s. 2 By limiting the intensity of the braking torque, unnecessary energy consumption is avoided due to increased braking torque caused by system malfunctions or misoperation.

[0050] The static braking limit function's gradient value for increasing braking torque can respond promptly to braking requests when the brake pedal speed is less than 80 mm / s, covering 99% of situations. This limit will remain effective until the brake pedal is released.

[0051] When the vehicle is stationary, the driver may unintentionally make slight movements or press the brake pedal harder. A gentle gradient limit can filter out these minor actions, preventing the system from frequently adjusting torque and improving the static NVH experience. At the same time, this gradient can respond to normal, conscious braking requests without making the driver feel like they are not pressing the brake pedal at all.

[0052] In this embodiment, the method further includes: if vehicle movement is detected during the parking restriction process, using a higher braking intensity limit to prevent the vehicle from rolling away until the vehicle is powered on and restarted again; if vehicle movement is detected again, using conventional braking until the vehicle is powered on and restarted again, and disabling the static braking restriction function of the vehicle.

[0053] If vehicle movement is detected during parking, indicating that the braking force is insufficient and a higher braking force is needed to prevent further rolling, the system will no longer rely on the original standard limit and will instead use a higher braking torque with a greater safety margin to ensure the vehicle stops rolling.

[0054] If vehicle movement is detected again after applying higher braking intensity, it indicates that the system is still unable to reliably keep the vehicle stationary even with higher braking intensity. This is likely not due to external conditions, but rather an internal system malfunction. In this case, a function degradation is implemented, disabling the vehicle's static braking limitation function. Simultaneously, a backup is activated, using conventional braking. This means the system completely bypasses the optimized static braking logic, employing a more direct and basic, but less comfortable, braking method, such as continuously applying a fixed, large hydraulic pressure, fundamentally preventing the risk of continuous vehicle roll due to repeated failures of the same function.

[0055] The method further includes disabling the vehicle's static braking limit function when a fault is detected in the vehicle's wheel speed signal.

[0056] If the wheel speed signal malfunctions, the change in wheel speed cannot be accurately determined, and therefore the braking torque intensity value and the gradient value of the braking torque increase of the static braking limit function cannot be used. In this case, the static braking limit function should be turned off to improve safety.

[0057] This embodiment introduces an electronic device, including a processor and a memory, wherein the memory stores programs or instructions that can run on the processor, and when the programs or instructions are executed by the processor, they implement the steps of the vehicle stationary braking limit control method of the brake-by-wire system as described in any embodiment of the present invention.

[0058] This embodiment describes a vehicle that includes an electronic device as described in the above embodiments of the present invention.

[0059] While specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the invention.

[0060] Those skilled in the art will recognize that the modules and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0061] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the above-described apparatus and equipment can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0062] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or modules may be electrical, mechanical, or other forms.

[0063] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules; that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of the embodiments of the present invention, depending on actual needs.

[0064] In addition, the functional modules in the embodiments of the present invention can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0065] If the aforementioned functions are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, ROM, RAM, magnetic disks, or optical disks.

[0066] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

[0067] It should be understood that the sequence numbers of the steps in the invention's content and embodiments do not absolutely imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention. The foregoing description of embodiments of this disclosure has been provided for illustrative and descriptive purposes. The foregoing description is not exhaustive and is not intended to limit this disclosure to the exact form disclosed. Various modifications and variations may exist based on the foregoing teachings, or various modifications and variations may be derived from the practice of this disclosure. These embodiments were chosen and described to illustrate the principles of this disclosure and its practical application, so that those skilled in the art can utilize this disclosure in various implementations and modifications suitable for the specific purpose of the concept.

Claims

1. A method for limiting vehicle stationary braking in a brake-by-wire system, characterized in that, include: When the vehicle speed is less than the low speed threshold, obtain the vehicle status; The gradient of the braking torque change is determined based on the vehicle's condition; Vehicle control is performed based on the gradient of the braking torque change.

2. The method according to claim 1, characterized in that, Determining the gradient of the braking torque change based on the vehicle state includes: Determine the target deceleration when the vehicle is under braking; When the brake pedal force reaches the preset target, the braking capacity is increased to the level of conventional braking. When the brake pedal force does not reach the preset target, the gradient of the increase in braking torque is determined according to the first limiting condition and the target deceleration, wherein the first limiting condition is that the braking time is less than the first preset time.

3. The method according to claim 2, characterized in that, Determining the gradient of the increase in braking torque based on the first constraint and the target deceleration includes: The maximum value of the gradient of the increase in braking torque is determined based on the target deceleration and the first constraint condition; The gradient of the increase in braking torque is determined based on the maximum value of the gradient of the increase in braking torque and a pre-set first coefficient.

4. The method according to claim 1, characterized in that, Determining the gradient of the braking torque change based on the vehicle state includes: Determine the target acceleration while the vehicle is in the state of starting and releasing the brakes; Based on the second constraint and the target acceleration, the gradient of the reduction in braking torque is determined, wherein the second constraint is that the time to release the brake is less than a second preset time.

5. The method according to claim 4, characterized in that, Determining the gradient of the reduction in braking torque based on the second constraint and the target acceleration includes: The minimum value of the gradient of the reduction in braking torque is determined based on the target acceleration and the second constraint. The gradient of the braking torque reduction is determined based on the minimum value of the gradient of the braking torque reduction and a pre-set second coefficient.

6. The method according to claim 1, characterized in that, Determining the gradient of the braking torque change based on the vehicle state includes: If no wheel speed change is detected within the target time, the braking torque intensity of the vehicle is limited to the braking torque intensity value of the pre-set static braking limit function, and the gradient of the increase in the braking torque of the vehicle is limited to the gradient value of the increase in the braking torque of the pre-set static braking limit function.

7. The method according to claim 6, characterized in that, The method further includes: If vehicle movement is detected during parking restrictions, a higher braking intensity limit will be used to prevent the vehicle from rolling away until the vehicle is next powered on and restarted. If vehicle movement is detected again, conventional braking will be used until the vehicle is powered on and restarted, and the static braking limitation function of the vehicle will be disabled.

8. The method according to claim 7, characterized in that, The method further includes: If a fault is detected in the wheel speed signal of the vehicle, the static braking limitation function of the vehicle shall be disabled.

9. An electronic device, characterized in that, It includes a processor and a memory, the memory storing a program or instructions that can run on the processor, the program or instructions being executed by the processor to implement the steps of the vehicle stationary braking limit control method for a brake-by-wire system as described in any one of claims 1 to 8.

10. A vehicle, characterized in that, Includes an electronic device as described in claim 9.

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