Vehicle braking control method and device, new energy vehicle and storage medium

Abstract

The invention relates to a vehicle braking control method and device, a new energy vehicle and a storage medium, and relates to the technical field of new energy vehicles. The method comprises the steps that under the condition that the electric braking function of a vehicle is activated, vehicle braking is controlled based on a motor, the vehicle speed change rate and the electric braking target torque of the vehicle are determined in the process, and the corresponding target switching vehicle speed and the target torque switching gradient are obtained based on the vehicle speed change rate; and based on the target switching vehicle speed and the target torque switching gradient, the motor torque is adjusted to be output to the electric braking target torque so as to control vehicle braking. By adopting the method, the problems of zero-crossing impact of the torque control motor and the like can be avoided, and sudden deceleration change or slope parking speed fluctuation can be optimized at the same time.

Description

Technical Field

[0001] The present application relates to the technical field of new energy vehicles, and in particular to a vehicle braking control method, device, new energy vehicle, storage medium and computer program product. Background Art

[0002] New energy vehicle technology is updated day by day, and it is very necessary to improve the safety of new energy vehicles, especially the safety of the vehicle's braking process.

[0003] At present, the braking control of vehicles is mainly carried out by the driver operating the braking system. However, in the event of a failure of the braking system, in order to ensure that the vehicle has sufficient deceleration, the maximum recovery torque available from the motor is generally used as the target torque for electric braking. During the process, there may be a sudden change in the motor output torque, which may affect braking safety. Summary of the invention

[0004] Based on this, it is necessary to provide a vehicle braking control method, device, new energy vehicle, computer-readable storage medium and computer program product to address the above technical problems.

[0005] In a first aspect, the present application provides a vehicle braking control method, comprising:

[0006] When the electric brake function of the vehicle is activated, the target holding torque is determined based on the slope of the road the vehicle is currently on, the vehicle mass and the preset rolling resistance coefficient;

[0007] During the vehicle electric braking process, the vehicle speed change rate is obtained, and the corresponding switching speed and torque switching gradient are obtained based on the vehicle speed change rate; the switching speed is positively correlated with the absolute value of the vehicle speed change rate, and the torque switching gradient is negatively correlated with the absolute value of the vehicle speed change rate;

[0008] Based on the switching vehicle speed and the torque switching gradient, the motor torque output is adjusted to the hill-holding target torque to control vehicle braking.

[0009] In one embodiment, before determining the hill-holding target torque, the method further includes:

[0010] During the electric braking process of the vehicle, the vehicle speed relative to the ground and the longitudinal acceleration collected by the sensor are obtained, and the vehicle speed relative to the ground is derived to obtain the actual acceleration;

[0011] Based on the difference between the longitudinal acceleration and the actual acceleration, a table is looked up to determine the slope of the road surface on which the vehicle is currently located, and a previously determined slope is updated based on the slope.

[0012] In one embodiment, it also includes:

[0013] During the electric braking of the vehicle, determining the slope of the road on which the vehicle is located based on the first method and / or the second method;

[0014] In the first mode, an intermediate value is determined based on the vehicle speed relative to the ground, the wheel end torque and the tire radius, and the slope is determined by looking up a table based on the intermediate value;

[0015] In the second mode, an intermediate value is determined based on the vehicle speed relative to the ground, the wheel end torque and the tire radius, and the intermediate value is substituted into a preset calculation model to determine the slope.

[0016] In one embodiment, determining the slope of the road on which the vehicle is located based on the first method and / or the second method includes:

[0017] Acquire multiple slopes determined based on the second method within a preset time before the current time;

[0018] When the variance values ​​of the multiple slopes are smaller than the set variance threshold, the second method is selected to determine the slope; otherwise, the first method is selected to determine the slope.

[0019] In one embodiment, the vehicle speed over the ground is obtained as follows:

[0020] Acquiring a motor speed of the vehicle, and determining a vehicle speed based on the motor speed;

[0021] Acquire the driving direction of the vehicle; the driving direction is forward or reverse;

[0022] A ground speed of the vehicle is determined based on the driving direction and the vehicle speed.

[0023] In one embodiment, the method of obtaining the driving direction of the vehicle includes:

[0024] The vehicle's driving direction is determined based on the wheel speed direction when any of the following conditions are met:

[0025] The vehicle speed is less than the preset forward speed;

[0026] The driving direction of the vehicle changes.

[0027] In one embodiment, it also includes:

[0028] Activating the electric braking function when at least one of the following conditions is met:

[0029] A first condition that a key press duration of a target key of the vehicle is greater than a preset duration threshold;

[0030] A second condition that the number of key presses on the target key within a preset time period is greater than a preset key press number threshold;

[0031] The third condition is that the relative distance between the vehicle and the preceding vehicle is less than a preset relative distance threshold, and the relative speed is greater than a preset relative speed threshold.

[0032] In one embodiment, it also includes:

[0033] When the accelerator pedal opening is greater than a preset proportional value or the vehicle speed relative to the ground is less than a preset reverse vehicle speed, the electric braking function is exited.

[0034] In a second aspect, the present application provides a vehicle braking control device, comprising:

[0035] A torque determination module, used to determine a target holding torque based on the slope of the road the vehicle is currently on, the vehicle mass and a preset rolling resistance coefficient when the electric braking function of the vehicle is activated;

[0036] An adjustment parameter determination module is used to obtain a vehicle speed change rate of the vehicle during the vehicle electric braking process, and obtain a corresponding switching speed and torque switching gradient based on the vehicle speed change rate; the switching speed is positively correlated with the absolute value of the vehicle speed change rate, and the torque switching gradient is negatively correlated with the absolute value of the vehicle speed change rate;

[0037] The torque adjustment module is used to adjust the motor torque output to the hill-holding target torque based on the switching vehicle speed and the torque switching gradient to control vehicle braking.

[0038] In a third aspect, the present application provides a new energy vehicle, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of any of the methods described above when executing the computer program.

[0039] In a fourth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of any of the methods described above.

[0040] In a fifth aspect, the present application provides a computer program product, including a computer program, which implements the steps of any of the methods described above when executed by a processor.

[0041] The above-mentioned vehicle braking control method, device, new energy vehicle, storage medium and computer program product, when the vehicle's electric braking function is activated, control the vehicle braking based on the motor, determine the vehicle speed change rate and electric braking target torque in the process, and obtain the corresponding target switching speed and target torque switching gradient based on the speed change rate, and adjust the motor torque output to the electric braking target torque based on the target switching speed and target torque switching gradient to control the vehicle braking. Since the target switching speed is positively correlated with the absolute value of the vehicle speed change rate, and the target torque switching gradient is negatively correlated with the absolute value of the vehicle speed change rate, during the electric braking process, when it is found that the absolute value of the current vehicle speed change rate is large, the vehicle braking can be controlled at a larger target switching speed, and the output torque of the motor can be adjusted with a smaller target torque switching gradient. Alternatively, when it is found that the absolute value of the current vehicle speed change rate is small, the vehicle braking can be controlled at a smaller target switching speed, and the output torque of the motor can be adjusted with a larger target torque switching gradient. This avoids sudden changes in the motor output torque when decelerating to a lower speed, avoids problems such as zero-crossing impact of the torque control motor, and simultaneously optimizes sudden changes in deceleration or speed fluctuations when parking on a slope, ensures vehicle braking within a reasonable time and distance, improves the safety of the vehicle's electric braking process, and can improve the riding experience during the vehicle's electric braking process. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, the drawings required for use in the embodiments or the related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 A diagram showing an application environment of a vehicle braking control method in an embodiment;

[0044] Figure 2 A schematic flow chart of a vehicle braking control method in one embodiment;

[0045] Figure 3 A schematic flow chart of a vehicle braking control method in another embodiment;

[0046] Figure 4 is a structural block diagram of a vehicle brake control device in one embodiment;

[0047] Figure 5 1 is a structural diagram of a new energy vehicle in one embodiment. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0049] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0050] Before starting to describe the embodiments of the present application in detail, the terms / nouns involved in the embodiments of the present application are explained as follows.

[0051] The three-dimensional coordinate system of a car has three directions: the lateral x direction refers to the left and right direction of the vehicle; the longitudinal y direction refers to the front and back direction of the vehicle; the up and down direction (vertical direction) of the vehicle is the z direction; among them, the synthesis of the lateral speed and the longitudinal speed is the speed of the vehicle.

[0052] The yaw rate of a vehicle refers to the speed at which the vehicle rotates around a vertical axis; the yaw rate describes the speed at which the vehicle rotates when turning.

[0053] D gear (Drive gear): The vehicle's forward gear. Normally, the motor should rotate forward at this time and the motor speed should be a positive value. If the motor rotates backward at this time, it indicates that the motor is reversed.

[0054] R gear (Reverse gear): The reverse gear of the vehicle. Under normal circumstances, the motor should rotate backward at this time and the motor speed should be a negative value; if the motor rotates forward at this time, it indicates that the motor is reversed.

[0055] The vehicle speed and motor speed are connected through a transmission system, and the two are directly proportional. For example, when the motor speed increases, the vehicle speed will increase accordingly.

[0056] Motor torque, also known as the output torque of the motor, is one of the basic parameters of the motor and is commonly expressed in Nm (Newton-meter). The motor speed and output torque are usually inversely proportional. For example, at starting or low speed, the vehicle speed is low, the motor speed is low, and the motor output torque is high to provide sufficient driving force to overcome inertia and resistance; at high speed, the vehicle speed is high, the motor speed is high, and the output torque is low to meet cruising needs while improving efficiency. The maximum available recovery torque of the motor refers to the maximum value of the negative torque generated by the motor during energy recovery. When the driver releases the accelerator pedal or steps on the brake pedal, the motor control will generate a negative torque to slow down the car and achieve energy recovery. The size of this value depends on factors such as the vehicle's control strategy, driving status, and the battery's energy storage capacity.

[0057] The target torque of electric braking is divided into deceleration torque and hill-holding torque. Generally speaking, the deceleration torque, dynamic torque or braking torque is used when the vehicle is dynamic, and the hill-holding torque is used when the vehicle is static. The hill-holding torque can make the vehicle stationary on different slopes. The main goal of the braking torque is deceleration, which can be dynamically adjusted according to the deceleration requirements. The braking torque can occur at various speeds of the vehicle and is not limited to use when stopped. The main function of the hill-holding torque is not to decelerate the vehicle, but to maintain the vehicle's stationary state. It is usually applied when the vehicle speed is low or even close to 0. In some cases, the hill-holding torque can be continuously increased from 0 to ensure that the vehicle remains as stationary as possible on uphill or downhill road conditions, thereby obtaining a suitable hill-holding torque.

[0058] Stalled rotor: A situation in which the motor still outputs torque when the speed is 0 rpm.

[0059] The vehicle braking control method provided in the embodiment of the present application can be applied to Figure 1 In the application environment shown, the vehicle includes a cockpit software system 101, a vehicle interconnection terminal T-BOX (Telematics BOX) 102, a vehicle controller 103, a traditional braking system 104, a power battery system 105, a motor and a motor controller 106, etc. connected via a bus 100.

[0060] The cockpit software system 101 can be used to control the user interface in the car, including the instrument panel, touch screen, entertainment system and navigation system, and provide interactive functions for the driver and passengers.

[0061] As the vehicle's telematics unit, T-BOX 102 can connect the vehicle and the cloud through a communication network and is responsible for collecting, uploading and remotely controlling vehicle data.

[0062] The vehicle controller 103, as the brain of the new energy vehicle, is responsible for coordinating and controlling the operation of components such as batteries, motors, motor controllers, and thermal management systems, to achieve intelligent control of the vehicle's power distribution, energy management, and vehicle functions.

[0063] The conventional braking system 104, including the conventional brake system, mainly controls the deceleration and parking process of the vehicle by adjusting the clamping torque.

[0064] The power battery system 105 is mainly used to provide a main power source for the vehicle and to provide power for the motor when driving.

[0065] The motor and motor controller 106, where the motor is the core component that converts electrical energy into mechanical energy and provides power when the vehicle is driving, and the motor controller is responsible for controlling the speed and torque output of the motor. It receives instructions from the vehicle control system and adjusts the working state of the motor so that the motor can achieve the functions of acceleration, deceleration and braking. Specifically, the motor controller can change the working state of the motor by adjusting the current and voltage, and decide whether the motor drives the vehicle forward or recovers energy.

[0066] Among them, the motor and the motor controller 106 can also constitute an electric braking system. The electric braking system can be understood as adjusting the reverse torque of the motor through the motor controller to achieve vehicle deceleration or parking. In this process, the vehicle is braked by converting electrical energy into mechanical energy. The principles involved include energy recovery and braking control. Energy recovery can be understood as when the vehicle decelerates or stops, the motor controller controls the motor to generate reverse torque, converts the vehicle's kinetic energy into electrical energy, and stores it back in the battery, thereby extending the cruising range. This control method can reduce dependence on traditional mechanical brakes. Correspondingly, the electric braking process can be understood as the process of braking the vehicle mainly through the electric braking system.

[0067] For new energy vehicles, braking can be performed through the traditional braking system. When the traditional braking system fails, in order to ensure driving safety, the electric braking function can be activated, so that the vehicle's electric braking can be achieved through the motor. In the embodiment of the present application, when the electric braking function of the vehicle is activated, the target torque required for the vehicle to stop can be preliminarily determined. Considering the different driving conditions of different vehicles, the response accuracy of the motor controller and the motor may also be different. Therefore, during the vehicle's electric braking process, the vehicle speed change rate is dynamically obtained, and the switching speed and torque switching gradient adapted to the current vehicle are determined with reference to the speed change rate. Based on the switching speed and torque switching gradient, the motor is controlled to perform torque switching, thereby achieving the timeliness and stability of the vehicle's braking stop.

[0068] In an exemplary embodiment, Figure 2 As shown, a vehicle braking control method is provided, which is applied to Figure 1 The vehicle controller of the vehicle in the embodiment is used as an example for explanation. In other embodiments, the method can also be implemented by a motor controller, or by a vehicle controller and a motor controller in cooperation. The method includes the following steps S201 to S203. Among them:

[0069] S201, when the electric braking function of the vehicle is activated, determine the hill-holding target torque based on the slope of the current road surface on which the vehicle is located, the vehicle mass and a preset rolling resistance coefficient.

[0070] Among them, the electric braking function and the activation conditions of the electric braking function can be pre-configured in the vehicle in the present application. The electric braking function can be understood as a function of controlling vehicle braking based on the above-mentioned electric braking system. When this function is activated, it can replace the traditional braking system to achieve vehicle deceleration and parking. The activation conditions of the electric braking function can include one or more conditions.

[0071] In the embodiment of the present application, the motor under the electric braking function is the same motor as the motor during normal driving of the vehicle. It can be understood that the electric braking function and the vehicle driving function are two working modes of the motor. The motor can switch to the electric braking function mode, or exit the electric braking function mode and switch to the vehicle driving function mode based on the preset activation conditions and return conditions of the electric braking function.

[0072] In some embodiments, during vehicle driving, the vehicle controller can obtain multiple status information of the vehicle in real time or periodically, and determine whether the activation conditions of the electric braking function are met based on one or more of the multiple status information. If it is determined that the activation conditions are met, the aforementioned electric braking function can be activated.

[0073] In some embodiments, during the driving process of the vehicle, the vehicle controller obtains multiple status information of the vehicle in real time, matches the multiple status information with the activation conditions of the electric braking function, and determines whether the activation conditions of the electric braking function are met. If they are met, the slope of the road on which the vehicle is currently located, the vehicle mass, and the preset rolling resistance coefficient are obtained or calculated, and these data can be brought into the pre-built torque determination model to determine the target torque for holding the slope through the torque determination model. Among them, the torque determination model can include a relational model, a mathematical model, a neural network model, etc.

[0074] In the embodiment of the present application, the hill-holding target torque needs to be within the maximum recoverable torque range of the motor.

[0075] S202, during the vehicle electric braking process, the vehicle speed change rate is obtained, and the corresponding switching speed and torque switching gradient are obtained based on the speed change rate; the switching speed is positively correlated with the absolute value of the speed change rate, and the torque switching gradient is negatively correlated with the absolute value of the speed change rate.

[0076] In the embodiment of the present application, the vehicle speed change rate can be understood as the vehicle acceleration, which represents the change in vehicle speed per unit time, and its unit can be m / s². During the process of the vehicle braking by motor control, the vehicle controller can obtain the vehicle speed change rate in real time or periodically.

[0077] The switching speed represents the timing of controlling the motor torque to switch to the target torque for holding the hill, and its unit can be km / h. For example, the switching speed can be set to 5 km / h. When the vehicle speed decelerates from 20 km / h to 5 km / h, the timing of controlling the motor torque to switch to the target torque for holding the hill is met, and the motor controller controls the motor torque to switch to the target torque for holding the hill.

[0078] The torque switching gradient represents the amount of change in the motor torque allowed per unit time, and its unit can be Nm / s. For example, when the torque switching gradient is 2Nm / s, the amount of change in the motor torque allowed per second is 2Nm. The torque switching gradient can prevent the motor torque from changing suddenly in a short period of time.

[0079] In one embodiment, the vehicle controller can periodically determine the vehicle speed change rate, and each time a new vehicle speed change rate is determined, the switching vehicle speed and torque switching gradient corresponding to the current vehicle speed change rate are re-acquired, for example, by looking up a preset corresponding table to determine the switching vehicle speed and torque switching gradient corresponding to the absolute value of the current vehicle speed change rate, and in the preset corresponding table, a larger absolute value of the vehicle speed change rate corresponds to a higher switching vehicle speed and a smaller torque switching gradient. When the vehicle decelerates quickly, the motor controller can advance the timing of switching the motor torque to the target torque for holding the slope, and reduce the amount of change in the motor torque allowed per unit time, thereby taking into account both the timeliness and stability of the vehicle deceleration and braking process.

[0080] S203, based on the switching vehicle speed and the torque switching gradient, adjusting the motor torque output to the hill-holding target torque to control vehicle braking.

[0081] In the embodiment of the present application, the vehicle controller can detect the vehicle's ground speed in real time. When the ground speed has slowed down to the switching speed (for example, 5 km / h), the motor controller is controlled to adjust the motor switching torque, with the hill-holding target torque as the target value, and the torque switching gradient is used to control the torque change of the motor per unit time, so that the torque of the motor gradually switches to the hill-holding target torque, so that the motor completes the torque switching within the expected time, and avoids sudden changes in the motor torque in a short time.

[0082] Based on the method of the above embodiment, when the electric braking function of the vehicle is activated, the vehicle braking is controlled based on the motor, and the vehicle speed change rate and the electric braking target torque of the vehicle are determined in the process, and the corresponding target switching vehicle speed and target torque switching gradient are obtained based on the vehicle speed change rate, and then the motor torque is adjusted to the electric braking target torque based on the target switching vehicle speed and the target torque switching gradient to control the vehicle braking. Since the target switching vehicle speed is positively correlated with the absolute value of the vehicle speed change rate, and the target torque switching gradient is negatively correlated with the absolute value of the vehicle speed change rate, during the electric braking process, when it is found that the absolute value of the current vehicle speed change rate is large, the vehicle braking is started to be controlled with a larger target switching vehicle speed, and the output torque of the motor is adjusted with a smaller target torque switching gradient, or, when it is found that the absolute value of the current vehicle speed change rate is small, the vehicle braking is started to be controlled with a smaller target switching vehicle speed, and the output torque of the motor is adjusted with a larger target torque switching gradient, thereby avoiding the sudden change of the motor output torque when the vehicle speed is decelerated to a small speed, and at the same time ensuring the vehicle braking within a reasonable time and distance, which not only improves the safety of the vehicle braking process, but also improves the riding experience during the vehicle braking process.

[0083] In one embodiment, before determining the hill-holding target torque, the method further includes:

[0084] During the electric braking process of the vehicle, the vehicle's ground speed and the longitudinal acceleration collected by the sensor are obtained, and the ground speed is derived to obtain the actual acceleration;

[0085] Based on the difference between the longitudinal acceleration and the actual acceleration, the slope of the road the vehicle is currently on is determined by looking up the table.

[0086] The accuracy of the sensor's measurement of longitudinal acceleration may be related to its posture. For example, when the vehicle is on a slope, the sensor installed on the vehicle may be in a non-horizontal state, and the longitudinal acceleration measured by the sensor may not be accurate enough. Therefore, there may be a certain deviation between the longitudinal acceleration and the actual acceleration calculated based on the vehicle's ground speed. Therefore, based on the difference between the two, the current slope of the vehicle can be reversely inferred.

[0087] As an implementation method, a correspondence table may be pre-established, which includes a correspondence between multiple sets of difference values ​​(longitudinal acceleration and actual acceleration) and slopes. For example, as shown in the following table:

[0088] Difference (unit: m / s²) 1 2 3 Slope (unit: degrees) 2 4 6

[0089] It can be seen from this representation that the greater the difference between the longitudinal acceleration and the actual acceleration, the greater the current road slope; the smaller the difference between the longitudinal acceleration and the actual acceleration, the smaller the current road slope. The table lookup method is simple and efficient, and the current road slope of the vehicle can be quickly determined.

[0090] In some embodiments, since both the longitudinal acceleration and the actual acceleration can be determined or calculated in real time, the corresponding slope can be determined in real time based on the latest determined longitudinal acceleration and the actual acceleration, and the latest determined slope can be used to update the previously determined slope to ensure that the recorded slope better matches the actual situation.

[0091] In another embodiment, the slope of the road on which the vehicle is currently located may also be determined by other methods, including:

[0092] During the electric braking process of the vehicle, the slope of the road on which the vehicle is located is determined based on a predefined first mode and / or a second mode. In the first mode, an intermediate value is determined based on the vehicle speed relative to the ground, the wheel end torque and the tire radius, and the corresponding slope is determined by looking up the table based on the intermediate value; in the second mode, an intermediate value is determined based on the vehicle speed relative to the ground, the wheel end torque, the tire radius and a preset corresponding relationship, and the intermediate value is substituted into a preset calculation model to determine the slope through the calculation model.

[0093] As a specific example, based on the vehicle speed over the ground, the wheel end torque and the tire radius, the process of determining the intermediate value may be:

[0094]

[0095] in, Wheel end torque (unit: Nm), r is the tire radius of the vehicle (unit: m), is the air resistance coefficient, is the frontal area of ​​the vehicle (unit: square meters), is a constant of 1.2258, is the rotation mass conversion factor, is the vehicle speed relative to the ground (unit: km / h), m is the vehicle weight (unit: kilograms), and F1 is the intermediate value to be calculated.

[0096] As another specific example, the intermediate value is substituted into a preset calculation model, and the slope is determined by the calculation model, as shown below:

[0097]

[0098] Where m is the vehicle weight (unit: kilograms), g is the gravity coefficient, f is the rolling resistance coefficient, F1 is the calculated intermediate value, and θ represents the calculated slope (unit: degree).

[0099] The calculation formula for the above slope θ can be derived by combining the force balance when the vehicle is stationary on a slope, as described below.

[0100] The force F when standing on a slope:

[0101] F = slope resistance + rolling resistance + air resistance + acceleration resistance

[0102] Right now, = m·g·sinθ + m·g·f·cosθ+ +

[0103] ∴ The intermediate value F1 = m·g·sinθ + m·g·f·cosθ, which can be used to inversely solve for the slope θ.

[0104] In the first mode described above, the slope determination method needs to look up the table in combination with the intermediate value F1, and the slope is determined by looking up the table with the intermediate value F1 as the horizontal coordinate and the vehicle speed relative to the ground as the vertical coordinate. The larger F1 is and the smaller the vehicle speed is, the larger the slope obtained by looking up the table is. In the second mode, the slope θ is further calculated in combination with the intermediate value F1. The larger F1 is, the larger the calculated slope θ is.

[0105] The slope determination method of the above embodiment of the present application determines the slope by the first method, which has better robustness, is more practical and simple, and determines the slope by the second method, and the determined slope may be more accurate. Therefore, when the computing power of the corresponding controller is insufficient, the first method can be selected to determine the slope. When the computing power of the controller is sufficient, the two methods can be used together or one method can be selected based on the set rules. For example: the efficiency of determining the slope by looking up the table based on the intermediate value F1 is high, and the slope is further calculated based on the intermediate value F1, which may be more accurate, but requires more computing resources. Therefore, the accuracy of the slope can be determined based on the two methods. The corresponding weights are determined for the two methods, and the final slope is obtained by weighted fusion of the results of the two methods; or one of them can be set as the default method, and the default method is preferably selected to determine the slope. In this way, the method with the best comprehensive accuracy and efficiency can be determined from a variety of methods for determining the slope. At the same time, even if the vehicle's sensor is abnormal and the slope cannot be determined by collecting the longitudinal acceleration, the slope of the road where the vehicle is located can still be determined more accurately.

[0106] In one embodiment, the method currently selected to determine the slope may be determined based on the stability of the slope values ​​determined by different methods within a set time period. Correspondingly, the above-mentioned determination of the slope of the road on which the vehicle is located based on the first method and / or the second method includes:

[0107] Acquire multiple slopes determined based on the second method within a preset time before the current time; when the variance values ​​of the multiple slopes are less than a set variance threshold, select the second method to determine the slope; otherwise, select the first method to determine the slope.

[0108] In other embodiments, weights can also be selected based on the actual accuracy of the two methods, and the final slope is calculated based on the results of the weight fusion of the two methods. One way of calculating the weight is: by calculating the variance value of multiple θ calculated over a period of time, if the variance value is less than the set threshold, it means that the calculated θ value has entered a steady state, and the calculated θ is preferentially selected, otherwise the F1 table lookup value is preferentially selected as the slope. Among them, the way to preferentially select θ can include: assigning a larger weight to θ and assigning a smaller weight to the slope determined by F1. Similarly, the preferential selection of the F1 table lookup value can include: assigning a larger weight to the slope determined by F1 and assigning a larger weight to θ.

[0109] The embodiments of the present application provide a variety of ways to determine the slope. In actual application, one or more ways to determine the slope can be selected based on actual conditions.

[0110] To better illustrate the technology of this application, please refer to Figure 3 , the vehicle braking control method of the present application will be described in conjunction with a detailed embodiment.

[0111] Step S301: The vehicle controller VCU monitors the vehicle motor speed n, gear position, and longitudinal acceleration in real time , vehicle mass m, and the maximum available recovery torque of the motor.

[0112] Step S302: Calculate the vehicle speed based on the motor speed. The basic principle is as follows:

[0113]

[0114] Where V is the vehicle speed (unit: km / h), r is the tire radius (unit: meter), i is the speed ratio, is the conversion factor from rotational speed to vehicle speed.

[0115] Step S303: Determine the vehicle's driving direction based on the motor speed and wheel speed direction The basic principle is as follows:

[0116] The vehicle's driving direction is determined when any of the following conditions are met:

[0117] ① The vehicle speed is less than 5 km / h. The threshold can be set to other values ​​based on actual needs, but the driving direction is generally determined when the absolute value of the vehicle speed relative to the ground is small.

[0118] ②The vehicle's driving direction changes.

[0119] In the embodiment of the present application, the vehicle driving direction is divided into forward and reverse. In some embodiments, the vehicle driving direction can be determined by the forward and reverse rotation of the motor. For example, a positive motor speed can correspond to a forward driving direction, and a negative motor speed can correspond to a reverse driving direction. For example, when the motor speed is less than -50 rpm, it is determined that the driving direction is reverse, then Equal to -1, when the motor speed is greater than 50rpm, the driving direction is determined to be forward. Equal to 1. The thresholds -50rpm and 50rpm can be set to other values ​​according to actual conditions. In order to ensure the accuracy of judgment, the threshold is generally not close to 0.

[0120] In other embodiments, when the wheel speed direction is positive, it is determined When equal to 1 and the wheel speed direction is reverse, determine Equal to -1.

[0121] Among them, forward and reverse can refer to the direction of the vehicle head, the direction the vehicle head is facing is the forward direction, and the direction opposite to the vehicle head is the reverse direction.

[0122] Step S304: Calculate the vehicle speed relative to the ground based on the driving direction and the motor speed, which is used to determine whether the vehicle is driving in the reverse direction. The basic principle is as follows:

[0123]

[0124] In the formula, is the vehicle speed over the ground (unit: km / h), is the vehicle's driving direction. As mentioned above, 1 and -1 can be used to represent the forward direction and the reverse direction respectively.

[0125] Step S305: Based on the target button, the accelerator, and the vehicle speed relative to the ground, determine the activation flag of the electric brake function.

[0126] The target button may be a physical button or a virtual button inside the vehicle, and the association between the target button and the electric brake function is predefined. The target button may be a dedicated button for activating or deactivating the electric brake function, or may be a button that realizes other functions and is configured to activate or deactivate the electric brake function under specific operating conditions.

[0127] The activation conditions of the electric brake function include:

[0128] (1) A first condition that the duration of pressing a target control of the vehicle is greater than a preset duration threshold;

[0129] (2) A second condition that the number of key presses on the target control within a preset time period is greater than a preset key press threshold;

[0130] (3) The third condition that the relative distance between the vehicle and the preceding vehicle is less than a preset relative distance threshold and the relative speed is greater than a preset relative speed threshold;

[0131] When at least one of the first condition, the second condition, and the third condition is met, the electric braking function is activated. For example, if the driver often presses the target button for more than 1 second, it means that there is a need to decelerate.

[0132] The exit conditions of the electric brake function include: when the accelerator pedal opening is greater than a preset ratio or the vehicle speed to the ground is less than a preset reverse speed, the electric brake function is exited. For example, the driver's accelerator pedal opening is greater than 20%; or the vehicle speed to the ground is less than -5km / h. When the driver pedals with a large amplitude, it means that there is a need for acceleration. When the vehicle speed to the ground is less than -5km / h, it means that the vehicle has reversed. In order to avoid unexpected movement, the electric brake function is forced to exit.

[0133] Step S306: Calculate the slope based on the longitudinal acceleration a and the vehicle speed relative to the ground. The basic principle is as follows:

[0134] Based on ground speed Derivative, get the rate of change of vehicle speed .

[0135] Based on the longitudinal acceleration a and the vehicle speed change rate The difference is calculated by looking up the table.

[0136] In one embodiment, the slope is determined by looking up the table below with the difference as the horizontal coordinate. The greater the difference between the longitudinal acceleration a and the vehicle speed change rate, the greater the slope determined by looking up the table.

[0137] Slope table

[0138] Difference (unit: m / s²) 1 2 3 Slope (unit: degrees) 2 4 6

[0139] Step S307: Calculate the electric braking target torque / hill-holding target torque based on the function flag, vehicle speed over the ground, slope, vehicle mass, and the maximum regenerative torque available from the motor.

[0140] In one embodiment, when the flag of the electric brake function is activated, the electric brake target torque is determined by looking up the table with the ground speed as the horizontal coordinate and the slope as the vertical coordinate. To ensure that the vehicle has sufficient deceleration, the maximum recovery torque available from the motor can also be used as the electric brake target torque during driving. To ensure that the current vehicle is on a slope and the driver has a need to stay on the slope, the electric brake target torque must ensure that the vehicle can stay on the current slope when the ground speed is 0. To achieve this goal, the electric brake target torque at 0 speed can be set to an initial value in combination with vehicle dynamics. The formula when the vehicle is stationary is as follows:

[0141]

[0142] In the formula, is the required initial electric brake torque (unit: Nm), r is the tire radius of the vehicle (unit: meter), G=mg, m is the vehicle weight (unit: kilogram), g is the gravity coefficient, f is the rolling resistance coefficient, The slope of the road.

[0143] In the embodiment of the present application, various motor torques determined in the embodiment of the present application, including initialization values, target values, etc., must be within the range of the maximum recoverable torque of the motor.

[0144] Step S308: Determine the switching vehicle speed and torque switching gradient based on the vehicle speed change rate and the current road slope.

[0145] In order to avoid the motor torque suddenly changing to the maximum available recovery torque of the motor or the initial torque or target torque of the electric brake when the electric brake function is activated or exited, filtering processing can be set, and when the wheel-end torque or the motor torque is in the zero-crossing interval [-50,50]Nm, the filtering processing is enhanced.

[0146] For example, in order to avoid a sudden change in torque from the maximum available recovery torque of the motor to the required torque for electric braking, that is, the initial value of the electric braking torque or the target torque for electric braking, during the activation of the electric braking function, the speed switching and torque switching gradient need to be processed in combination with the speed change rate. If the absolute value of the speed change rate is too large, it means that the deceleration is too strong. At this time, the switching speed needs to be increased and the torque switching gradient needs to be reduced to avoid the loss of deceleration caused by the sudden change in torque.

[0147] Among them, the specific method of processing the switching speed and torque switching gradient in combination with the vehicle speed change rate can be: using the vehicle speed change rate as the horizontal coordinate, and determining the corresponding switching speed by querying the switching speed schematic table; using the vehicle speed change rate as the horizontal coordinate, and determining the corresponding torque switching gradient by querying the torque gradient schematic table.

[0148] Switching speedometer

[0149] Vehicle speed change rate (unit: m / s²) -0.1 -0.2 Switch vehicle speed (unit: km / h) 2 3

[0150] Torque gradient diagram

[0151] Vehicle speed change rate (unit: m / s²) -0.1 -0.2 Torque switching gradient (unit: Nm / s) 10 5

[0152] It can be understood that the execution order of the above steps S307 and S308 is not limited to the order shown in the figure, and S308 can be executed first and then S307, or steps S307 and S308 can be executed in parallel.

[0153] Step S309: Based on the switching vehicle speed and torque switching gradient determined in the above steps, the motor torque output is gradually adjusted to the hill-holding target torque to control the vehicle to complete braking on the current road slope.

[0154] In the above embodiment, the vehicle controller can determine whether to activate the electric braking function based on the buttons, throttle, and ground speed. When the electric braking function is activated, the ground speed and speed change rate are calculated based on the motor speed; the slope of the road where the vehicle is currently located can be calculated based on the longitudinal acceleration and speed change rate, and the appropriate target torque for staying on the slope can be determined based on the slope. At the same time, the appropriate switching speed and torque switching gradient can be determined based on the speed change rate, thereby gradually adjusting the motor torque output to the target torque for staying on the slope. In this way, the motor torque is controlled to provide a certain braking capacity for the vehicle after the braking system fails, especially to optimize the torque control motor zero impact and other problems, and optimize the deceleration mutation or the speed fluctuation of staying on the slope, thereby improving the driving safety of the vehicle.

[0155] It should be understood that, although the steps in the flowcharts involved in the above embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0156] Based on the same inventive concept, the embodiment of the present application also provides a vehicle brake control device for implementing the vehicle brake control method involved above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in one or more vehicle brake control device embodiments provided below can refer to the limitations of the vehicle brake control method above, and will not be repeated here.

[0157] In an exemplary embodiment, Figure 4 As shown, a vehicle braking control device is provided, comprising:

[0158] The torque determination module 401 is used to determine the hill-holding target torque based on the slope of the road the vehicle is currently on, the vehicle mass and a preset rolling resistance coefficient when the electric braking function of the vehicle is activated;

[0159] The adjustment parameter determination module 402 is used to obtain the vehicle speed change rate of the vehicle during the vehicle electric braking process, and obtain the corresponding switching speed and torque switching gradient based on the vehicle speed change rate; the switching speed is positively correlated with the absolute value of the vehicle speed change rate, and the torque switching gradient is negatively correlated with the absolute value of the vehicle speed change rate;

[0160] The torque adjustment module 403 is used to adjust the motor torque output to the aforementioned hill-holding target torque based on the switching vehicle speed and the torque switching gradient to control vehicle braking.

[0161] The vehicle braking control device of the embodiment of the present application, when the electric braking function of the vehicle is activated, determines the target torque for holding the hill based on the slope of the current road surface on which the vehicle is located, the vehicle mass and the preset rolling resistance coefficient through the torque determination module; in addition, the vehicle speed change rate of the vehicle is obtained during the vehicle electric braking process by adjusting the parameter determination module, and the corresponding switching speed and torque switching gradient are obtained based on the speed change rate; the switching speed is positively correlated with the absolute value of the speed change rate, and the torque switching gradient is negatively correlated with the absolute value of the speed change rate; on this basis, the motor torque output is adjusted to the aforementioned target torque for holding the hill based on the switching speed and the torque switching gradient through the torque adjustment module to control the vehicle braking. Therefore, during the vehicle electric braking process, when it is found that the absolute value of the current vehicle speed change rate is large, the vehicle braking is controlled by a larger target switching speed, and the output torque of the motor is adjusted with a smaller target torque switching gradient. Alternatively, when it is found that the absolute value of the current vehicle speed change rate is small, the vehicle braking is controlled by a smaller target switching speed, and the output torque of the motor is adjusted with a larger target torque switching gradient, thereby avoiding the problem of motor zero impact, as well as the problem of sudden deceleration or speed fluctuation when parking on a slope, which not only improves the safety of the vehicle braking process, but also improves the riding experience during the vehicle braking process.

[0162] In one embodiment, the aforementioned vehicle braking control device further includes a slope determination module, which is used to:

[0163] During the vehicle's electric braking process, the vehicle's ground speed and the longitudinal acceleration collected by the sensor are obtained, and the ground speed is derived to obtain the actual acceleration; based on the difference between the aforementioned longitudinal acceleration and the actual acceleration, the slope of the road the vehicle is currently on is determined by looking up the table, and the previously determined slope is updated based on the slope.

[0164] In one embodiment, the aforementioned slope determination module may be specifically used to:

[0165] During the vehicle electric braking process, the slope of the road on which the vehicle is located is determined based on the first method and / or the second method; in the first method, an intermediate value is determined based on the vehicle speed relative to the ground, the wheel-end torque and the tire radius, and the slope is determined by looking up the table based on the intermediate value; in the second method, an intermediate value is determined based on the vehicle speed relative to the ground, the wheel-end torque and the tire radius, and the intermediate value is substituted into a preset calculation model to determine the slope.

[0166] In one embodiment, the aforementioned slope determination module can be specifically used to: obtain multiple slopes determined based on the second method within a preset time before the current time; when the variance value of the multiple slopes is less than the set variance threshold, select the second method to determine the slope; otherwise, select the aforementioned first method to determine the slope.

[0167] In one embodiment, the aforementioned vehicle braking control device further includes a vehicle speed over ground determining module, which is used to:

[0168] The motor speed of the vehicle is obtained, and the vehicle speed is determined based on the motor speed; the driving direction of the vehicle is obtained; the driving direction is forward or reverse; and the vehicle speed relative to the ground is determined based on the driving direction and the vehicle speed.

[0169] In one embodiment, the aforementioned vehicle braking control device further includes a direction determination module, which is used to:

[0170] The vehicle's driving direction is determined based on the wheel speed direction when any of the following conditions are met: the vehicle speed is less than the preset forward speed; the vehicle's driving direction changes.

[0171] In one embodiment, the aforementioned vehicle brake control device further includes an electric brake function management module, which is used to: activate the electric brake function when at least one of the following conditions is met;

[0172] A first condition that the key pressing duration of a target key of the vehicle is greater than a preset duration threshold;

[0173] A second condition that the number of key presses on the target key within a preset time period is greater than a preset key press number threshold;

[0174] The third condition is that the relative distance between the vehicle and the preceding vehicle is less than a preset relative distance threshold, and the relative speed is greater than a preset relative speed threshold.

[0175] In one embodiment, the electric brake function management module is further used to exit the electric brake function when the accelerator pedal opening is greater than a preset proportional value or the vehicle speed relative to the ground is less than a preset reverse vehicle speed.

[0176] Each module in the above vehicle brake control device can be implemented in whole or in part by software, hardware or a combination thereof. Each module can be embedded in or independent of the processor in the new energy vehicle in the form of hardware, or can be stored in the memory in the new energy vehicle in the form of software, so that the processor can call and execute the corresponding operations of each module.

[0177] In an exemplary embodiment, a new energy vehicle is provided, and its internal structure diagram can be as follows: Figure 5 As shown. The new energy vehicle includes a processor, a memory, an input / output interface, a communication interface, a display unit and an input device. Among them, the processor, the memory and the input / output interface are connected through a system bus, and the communication interface, the display unit and the input device are connected to the system bus through the input / output interface. Among them, the processor of the new energy vehicle is used to provide computing and control capabilities. The memory of the new energy vehicle includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The input / output interface of the new energy vehicle is used to exchange information between the processor and the external device. The communication interface of the new energy vehicle is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be realized through WIFI, a mobile cellular network, NFC (near field communication) or other technologies. When the computer program is executed by the processor, a vehicle braking control method is realized. The display unit of the new energy vehicle is used to form a visually visible picture, which can be a display screen, a projection device or a virtual reality imaging device. The display screen can be a liquid crystal display screen or an electronic ink display screen, and the input device of the new energy vehicle can be a touch layer covered on the display screen, or it can be a button, trackball or touchpad set in the new energy vehicle.

[0178] Those skilled in the art will understand that Figure 5 The structure shown in the figure is only a block diagram of a part of the structure related to the scheme of the present application, and does not constitute a limitation on the new energy vehicle to which the scheme of the present application is applied. A specific new energy vehicle may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0179] In an exemplary embodiment, a new energy vehicle is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps in the above-mentioned vehicle braking control method embodiments when executing the computer program.

[0180] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0181] In one embodiment, a computer program product is provided, including a computer program, which implements the steps in the above method embodiments when executed by a processor.

[0182] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but are not limited to this.

[0183] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0184] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A vehicle braking control method, characterized in that: include: When the electric brake function of the vehicle is activated, the target holding torque is determined based on the slope of the road the vehicle is currently on, the vehicle mass and the preset rolling resistance coefficient; During the vehicle electric braking process, the vehicle speed change rate is obtained, and the corresponding switching speed and torque switching gradient are obtained based on the vehicle speed change rate; the switching speed is positively correlated with the absolute value of the vehicle speed change rate, and the torque switching gradient is negatively correlated with the absolute value of the vehicle speed change rate; Based on the switching vehicle speed and the torque switching gradient, the motor torque output is adjusted to the hill-holding target torque to control vehicle braking.

2. The method according to claim 1, characterized in that Before determining the target torque for hill-holding, it also includes: During the electric braking process of the vehicle, the vehicle speed relative to the ground and the longitudinal acceleration collected by the sensor are obtained, and the vehicle speed relative to the ground is derived to obtain the actual acceleration; Based on the difference between the longitudinal acceleration and the actual acceleration, a table is looked up to determine the slope of the road on which the vehicle is currently located.

3. The method according to claim 1, characterized in that Also includes: During the electric braking of the vehicle, determining the slope of the road on which the vehicle is located based on the first method and / or the second method; In the first mode, an intermediate value is determined based on the vehicle speed relative to the ground, the wheel end torque and the tire radius, and the slope is determined by looking up a table based on the intermediate value; In the second mode, an intermediate value is determined based on the vehicle speed relative to the ground, the wheel end torque and the tire radius, and the intermediate value is substituted into a preset calculation model to determine the slope.

4. The method according to claim 3, characterized in that The determining the slope of the road on which the vehicle is located based on the first method and / or the second method includes: Acquire multiple slopes determined based on the second method within a preset time before the current time; When the variance values ​​of the multiple slopes are smaller than the set variance threshold, the second method is selected to determine the slope; otherwise, the first method is selected to determine the slope.

5. The method according to claim 2, characterized in that: The method for obtaining the ground speed is as follows: Acquiring a motor speed of the vehicle, and determining a vehicle speed based on the motor speed; Acquire the driving direction of the vehicle; the driving direction is forward or reverse; A ground speed of the vehicle is determined based on the driving direction and the vehicle speed.

6. The method according to any one of claims 1 to 5, characterized in that: Also includes: Activating the electric braking function when at least one of the following conditions is met: A first condition that a key press duration of a target key of the vehicle is greater than a preset duration threshold; A second condition that the number of key presses on the target key within a preset time period is greater than a preset key press number threshold; The third condition is that the relative distance between the vehicle and the preceding vehicle is less than a preset relative distance threshold, and the relative speed is greater than a preset relative speed threshold.

7. The method according to claim 6, characterized in that Also includes: When the accelerator pedal opening is greater than a preset proportional value or the vehicle speed relative to the ground is less than a preset reverse vehicle speed, the electric braking function is exited.

8. A vehicle brake control device, characterized in that: include: A torque determination module, used to determine a target holding torque based on the slope of the road the vehicle is currently on, the vehicle mass and a preset rolling resistance coefficient when the electric braking function of the vehicle is activated; An adjustment parameter determination module is used to obtain a vehicle speed change rate of the vehicle during the vehicle electric braking process, and obtain a corresponding switching speed and torque switching gradient based on the vehicle speed change rate; the switching speed is positively correlated with the absolute value of the vehicle speed change rate, and the torque switching gradient is negatively correlated with the absolute value of the vehicle speed change rate; The torque adjustment module is used to adjust the motor torque output to the hill-holding target torque based on the switching vehicle speed and the torque switching gradient to control vehicle braking.

9. A new energy vehicle, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

Images