A vehicle longitudinal reference speed estimation method and system suitable for multiple working conditions, and a vehicle

Abstract

The present invention relates to the field of vehicle speed estimation, and specifically discloses a vehicle longitudinal reference speed estimation method and system applicable to multiple working conditions, as well as a vehicle. The method detects whether the vehicle is in a low-speed running state. If so, a first longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed. Otherwise, a brake pedal signal is detected. If so, an ABS status flag is used to detect whether the vehicle is in an ABS control working state. Otherwise, a turning working state is detected. If in the ABS control working state, a second longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed. If in a turning working state, a third longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed. A fourth longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed in other working conditions. The present invention considers different working conditions when estimating the vehicle longitudinal reference speed, thereby improving the accuracy of the vehicle longitudinal reference speed estimation result and the vehicle operation stability.

Description

Technical Field

[0001] The present invention relates to the field of vehicle speed estimation, and in particular to a vehicle longitudinal reference speed estimation method and system applicable to multiple working conditions, and a vehicle. Background Art

[0002] Estimating vehicle parameters and states during motion is a key component of chassis control technology. Estimating the vehicle's longitudinal reference speed is crucial for the anti-lock braking system (ABS) and electronic stability control (ESC). Currently, most commercial vehicles lack the ability to equip themselves with higher-precision speed and longitudinal acceleration sensors due to cost constraints or sensor installation process limitations. Therefore, in practical applications, a state estimation algorithm must be employed based on the sensor configuration of mass-produced vehicles to estimate the vehicle's longitudinal reference speed. Furthermore, to ensure system reliability, the estimated longitudinal speed obtained using the state estimation method can be compared with the actual speed sensor measurement. This allows for real-time and effective identification of potential sensor faults, further ensuring the accuracy of the vehicle speed information used by the system.

[0003] However, traditional vehicle longitudinal reference speed estimation methods fail to consider the impact of various operating conditions. Patent application publication number CN113635908A discloses a method for calculating ABS reference speed, which employs fuzzy logic to calculate a first reference speed; employs other methods to calculate a second reference speed, where the other methods are methods other than the fuzzy logic method; employs fuzzy logic to determine a first reference speed fusion weight and a second reference speed fusion weight; and determines the ABS reference speed based on the first reference speed fusion weight, the second reference speed fusion weight, the first reference speed, and the second reference speed. However, this method fails to consider the complexity of vehicle operating conditions, and establishes fuzzy rules for the credibility of each wheel speed under different driving conditions, such as acceleration, deceleration, and coasting. This affects the accuracy of the vehicle longitudinal reference speed estimation results, and thus the vehicle's operational stability. Summary of the Invention

[0004] To solve the above problems, the present invention provides a vehicle longitudinal reference speed estimation method and system, and a vehicle applicable to multiple working conditions. Taking into account the operating conditions under different working conditions, separate estimation strategies are formulated for different working conditions to estimate the vehicle longitudinal reference speed, thereby improving the accuracy of the vehicle longitudinal reference speed estimation results and thus improving the vehicle operation stability.

[0005] In a first aspect, the technical solution of the present invention provides a method for estimating a vehicle longitudinal reference speed applicable to multiple working conditions, comprising the following steps:

[0006] S1, detecting whether the vehicle is in a low-speed running state, and if so, estimating the vehicle longitudinal reference speed using a first longitudinal reference speed estimation strategy, otherwise executing step S2;

[0007] S2, detect whether there is a brake pedal signal, if so, go to step S3, otherwise go to step S4;

[0008] S3, detecting whether the vehicle is in an ABS control condition based on the ABS status flag, and if so, estimating the vehicle longitudinal reference speed using the second longitudinal reference speed estimation strategy; otherwise, estimating the vehicle longitudinal reference speed using the fourth longitudinal reference speed estimation strategy;

[0009] S4, detecting whether the vehicle is in a turning condition, and if so, estimating the vehicle longitudinal reference speed using the third longitudinal reference speed estimation strategy; otherwise, estimating the vehicle longitudinal reference speed using the fourth longitudinal reference speed estimation strategy.

[0010] In an optional embodiment, step S1 detects whether the vehicle is in a low-speed running state, specifically including:

[0011] Get the current wheel speed of all wheels , and filter out the current maximum wheel speed ;in is the number of wheels;

[0012] Determine the current maximum wheel speed Is it less than the wheel speed threshold?

[0013] If so, it is determined that the vehicle is in a low-speed running state; otherwise, it is determined that the vehicle is not in a low-speed running state.

[0014] In an optional embodiment, estimating the longitudinal reference speed of the vehicle using a first longitudinal reference speed estimation strategy specifically includes:

[0015] The current vehicle longitudinal reference speed is calculated using the following formula ,

[0016] .

[0017] In an optional embodiment, estimating the vehicle longitudinal reference speed using the second longitudinal reference speed estimation strategy specifically includes:

[0018] Detect whether the vehicle wheel speed is at the peak point;

[0019] If so, estimating the vehicle longitudinal reference speed using a fourth longitudinal reference speed estimation strategy;

[0020] If not, calculate the peak interval reference speed deceleration using the following formula ,

[0021]

[0022] Where, is the maximum wheel speed at the previous peak point at the current sampling moment, is the maximum wheel speed of the first two peak points at the current sampling moment, is a constant value;

[0023] The current vehicle longitudinal reference speed is calculated using the following formula ,

[0024]

[0025] Where, is the vehicle longitudinal reference speed at the previous sampling moment, is the time interval between two samplings.

[0026] In an optional embodiment, detecting whether the vehicle wheel speed is at a peak point specifically includes:

[0027] By the current maximum wheel speed Calculate the current maximum wheel acceleration ;

[0028] Determine the current maximum wheel acceleration Whether the conditions are met , and the vehicle is in ABS step-boost state; is the maximum wheel acceleration at the previous sampling moment;

[0029] If so, the vehicle wheel speed is at the peak point, otherwise it is not at the peak point.

[0030] In an optional embodiment, estimating the vehicle longitudinal reference speed using a third longitudinal reference speed estimation strategy specifically includes:

[0031] Get the vehicle's yaw rate , half wheelbase and the radius of the vehicle's circular motion around the center of the turning circle ;

[0032] The centripetal acceleration of the outer wheel is calculated using the following formula: ,

[0033]

[0034] Where, is the wheel speed of the outer non-driven rear wheel;

[0035] The current vehicle longitudinal reference speed is calculated using the following formula ,

[0036] .

[0037] In an optional embodiment, after obtaining the vehicle parameters, the vehicle parameters are filtered, wherein the vehicle parameters include the current wheel speeds of all wheels. , vehicle yaw rate , the centripetal acceleration of the outer wheel during movement .

[0038] In an optional embodiment, estimating the longitudinal reference speed of the vehicle using a fourth longitudinal reference speed estimation strategy specifically includes:

[0039] The current maximum wheel speed As the current vehicle longitudinal reference speed .

[0040] In a second aspect, the technical solution of the present invention provides a vehicle longitudinal reference speed estimation system applicable to multiple working conditions, the system being implemented based on any of the above-described methods, including:

[0041] Vehicle low-speed state detection module: detects whether the vehicle is in a low-speed running state. If so, it triggers the first longitudinal reference vehicle speed estimation module; otherwise, it triggers the brake pedal signal detection module;

[0042] Brake pedal signal detection module: detects whether there is a brake pedal signal. If so, it triggers the ABS control condition detection module; otherwise, it triggers the turning condition detection module;

[0043] ABS control working condition detection module: detects whether the vehicle is in the ABS control working condition according to the ABS status flag bit, and triggers the second longitudinal reference vehicle speed estimation module if it is, otherwise triggers the fourth longitudinal reference vehicle speed estimation module;

[0044] Turning condition detection module: detects whether the vehicle is in a turning condition, and if so, triggers the third longitudinal reference vehicle speed estimation module; otherwise, triggers the fourth longitudinal reference vehicle speed estimation module;

[0045] A first longitudinal reference vehicle speed estimation module is configured to estimate the vehicle longitudinal reference vehicle speed using a first longitudinal reference vehicle speed estimation strategy;

[0046] A second longitudinal reference vehicle speed estimation module is configured to estimate the vehicle longitudinal reference vehicle speed using a second longitudinal reference vehicle speed estimation strategy;

[0047] A third longitudinal reference vehicle speed estimation module is configured to estimate the vehicle longitudinal reference vehicle speed using a third longitudinal reference vehicle speed estimation strategy;

[0048] The fourth longitudinal reference vehicle speed estimation module estimates the vehicle longitudinal reference vehicle speed using the fourth longitudinal reference vehicle speed estimation strategy.

[0049] In a third aspect, the technical solution of the present invention provides a vehicle equipped with the above-mentioned system and executing any of the methods described above.

[0050] The present invention provides a vehicle longitudinal reference speed estimation method, system, and vehicle applicable to multiple operating conditions. Compared with the prior art, the method and system have the following advantages: first, the method detects whether the vehicle is in a low-speed operating state. If the vehicle is in a low-speed operating state, a first longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed. If the vehicle is not in a low-speed operating state, a further method detects whether a brake pedal signal is present. If a brake pedal signal is present, the method detects whether the vehicle is in an ABS control operating state again. If no brake pedal signal is present, the method detects whether the vehicle is in a turning operating state again. Under the ABS control operating state, a second longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed. Under the turning operating state, a third longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed. Under other operating conditions, a fourth longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed. The method considers multiple operating conditions such as low-speed operation, ABS control operating state, and turning operating state, and considers the operating conditions under different operating conditions. Separate estimation strategies are formulated for different operating conditions to estimate the vehicle longitudinal reference speed, thereby improving the accuracy of the vehicle longitudinal reference speed estimation result and thereby improving the vehicle's operating stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0052] Figure 1 This is a flow chart of a method for estimating a vehicle longitudinal reference speed applicable to multiple working conditions, provided by an embodiment of the present invention.

[0053] Figure 2 This is a schematic diagram of the changes in wheel-end control pressure and speed during ABS control.

[0054] Figure 3 The figure is a flow chart of a specific embodiment of a method for estimating a vehicle longitudinal reference speed applicable to multiple working conditions provided by the present invention.

[0055] Figure 4 The present invention provides a schematic block diagram of a vehicle longitudinal reference speed estimation system applicable to multiple working conditions. DETAILED DESCRIPTION

[0056] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0058] Figure 1 This is a flow chart of a method for estimating the longitudinal reference speed of a vehicle applicable to multiple working conditions provided by an embodiment of the present invention. Figure 1 The execution entity may be a vehicle longitudinal reference speed estimation system applicable to multiple operating conditions. The vehicle longitudinal reference speed estimation method applicable to multiple operating conditions provided in embodiments of the present invention is executed by a computer device. Accordingly, the vehicle longitudinal reference speed estimation system applicable to multiple operating conditions runs on the computer device. The order of the steps in this flowchart may be changed, and some steps may be omitted, depending on different requirements.

[0059] like Figure 1 As shown, the method includes the following steps.

[0060] S1, detecting whether the vehicle is in a low-speed running state, and if so, estimating the longitudinal reference speed of the vehicle using a first longitudinal reference speed estimation strategy, otherwise executing step S2.

[0061] In this embodiment, the reference vehicle speed calculation takes into account the extremely low vehicle speed situation, analyzes the characteristics of the wheel speed signal in the extremely low vehicle speed situation, and provides a calculation formula for the reference vehicle speed in this situation.

[0062] This embodiment first detects whether the vehicle is in a low-speed running state, and determines whether it is in a low-speed running state by the wheel speed of all wheels, including obtaining the current wheel speed of all wheels. , and filter out the current maximum wheel speed , determine the current maximum wheel speed Is it less than the wheel speed threshold? If so, it is determined that the vehicle is in a low-speed running state. Otherwise, it is determined that the vehicle is not in a low-speed running state. is the number of wheels, For the The current wheel speed of each wheel.

[0063] When the vehicle is in a low-speed running state, the first longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed, specifically including calculating the current vehicle longitudinal reference speed by the following formula ,

[0064] .

[0065] S2, detect whether there is a brake pedal signal, if so, go to step S3, otherwise go to step S4.

[0066] In this embodiment, the brake pedal signal is detected again when the vehicle is not in a low-speed running state. When a brake pedal signal is present, the vehicle longitudinal reference speed is estimated based on the ABS control condition. When no brake pedal signal is present, the vehicle longitudinal reference speed is estimated based on the turning condition.

[0067] S3, detecting whether the vehicle is in the ABS control condition according to the ABS status flag. If so, the second longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed; otherwise, the fourth longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed.

[0068] In this embodiment, when there is a brake pedal signal, the second longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed in the ABS control condition; otherwise, the fourth longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed.

[0069] The method of estimating the longitudinal reference speed of the vehicle using the second longitudinal reference speed estimation strategy specifically includes the following steps.

[0070] Step 1: Detect whether the vehicle wheel speed is at a peak point.

[0071] This embodiment determines whether the vehicle wheel speed is at the peak point by wheel speed acceleration, and the current maximum wheel speed is Calculate the current maximum wheel acceleration ; Determine the current maximum wheel acceleration Whether the conditions are met , and the vehicle is in ABS step-boost state; is the maximum wheel acceleration at the previous sampling moment; if yes, the vehicle wheel speed is at the peak point, otherwise it is not at the peak point.

[0072] Step 2: If yes, estimate the vehicle longitudinal reference speed using the fourth longitudinal reference speed estimation strategy.

[0073] Step 3, if not, calculate the peak interval reference speed deceleration using the following formula ,

[0074]

[0075] Where, is the maximum wheel speed at the previous peak point at the current sampling moment, is the maximum wheel speed of the first two peak points at the current sampling moment, Is a constant value.

[0076] Step 4: Calculate the current vehicle longitudinal reference speed using the following formula: ,

[0077]

[0078] Where, is the vehicle longitudinal reference speed at the previous sampling moment, is the time interval between two samplings.

[0079] This embodiment takes into account the wheel speed changes and pressure control process in the ABS control cycle, and observes that the wheel speed peak point always appears during the period when the wheel starts step-by-step pressure increase. Based on this, the identified pseudo peaks can be filtered out to reduce the interference of noise peaks on the reference vehicle speed calculation.

[0080] In this embodiment, using the fourth longitudinal reference vehicle speed estimation strategy to estimate the vehicle longitudinal reference vehicle speed means that the current maximum wheel speed As the current vehicle longitudinal reference speed .

[0081] S4, detecting whether the vehicle is in a turning condition, and if so, estimating the vehicle longitudinal reference speed using the third longitudinal reference speed estimation strategy; otherwise, estimating the vehicle longitudinal reference speed using the fourth longitudinal reference speed estimation strategy.

[0082] In this embodiment, when there is no brake pedal signal, it is detected whether the vehicle is in a turning condition. In the turning condition, the third longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed. In the non-turning condition, the fourth longitudinal reference speed estimation strategy is used to estimate the vehicle longitudinal reference speed.

[0083] In this embodiment, the third longitudinal reference vehicle speed estimation strategy is used to estimate the vehicle longitudinal reference vehicle speed, which specifically includes the following steps.

[0084] Step 1: Get the vehicle's yaw rate , half wheelbase and the radius of the vehicle's circular motion around the center of the turning circle .

[0085] Step 2: Calculate the centripetal acceleration of the outer wheel using the following formula: ,

[0086]

[0087] Where, is the speed of the outside non-driven rear wheel.

[0088] Step 3: Calculate the current vehicle longitudinal reference speed using the following formula: ,

[0089] .

[0090] This embodiment takes into account cornering conditions (including ESC activation) when calculating the reference speed. By analyzing the vehicle's kinematics under cornering conditions and providing a formula for calculating the reference speed in these conditions, the reference speed calculation for ESC activation uses the IMU sensor signal as the input source. The reference speed is calculated based on the speed of the outer non-driven rear wheel, the yaw rate and lateral acceleration measured by the IMU, and the vehicle's wheelbase. This minimizes the impact of significant wheel speed variations under extreme conditions on the reference speed calculation.

[0091] In order to further understand the present invention, each operating condition is described in further detail below.

[0092] 1. Reference speed estimation under full braking

[0093] When all vehicles are braked due to the driver pressing the brake pedal, the estimation of the reference vehicle speed during the ABS control process should be considered. The ABS system is designed to control the tire slip rate to keep it within the optimal range to obtain maximum friction and maintain the lateral stability of the vehicle. Figure 2 As shown in the figure, during the ABS control process, the changes in wheel end brake pressure and wheel speed include the following stages:

[0094] 1) Braking begins. This is the initial peak point of wheel speed, brake pressure builds up, and wheel speed begins to decrease.

[0095] 2) When the wheel-end acceleration is lower than threshold value 1, the brake pressure enters the high-pressure holding stage and the wheel speed continues to decrease;

[0096] 3) When the slip rate reaches the threshold value, the wheel becomes unstable and the brake pressure enters the decompression stage. The wheel speed continues to decrease, but the wheel end acceleration begins to increase.

[0097] 4) When the wheel-end acceleration increases and exceeds threshold value 1, the brake pressure enters the low-pressure holding stage; when the wheel-end acceleration continues to increase and exceeds threshold value 2, the brake pressure remains in the low-pressure holding state, the wheel speed gradually recovers, and the wheel-end acceleration will decrease;

[0098] 5) When the wheel-end acceleration decreases and falls below threshold 2, the wheel stabilizes and the brake pressure enters the step-up phase. The wheel speed continues to increase, and the wheel-end acceleration gradually decreases. At this point, the wheel has gone through the previous phase of decompression and pressure maintenance. Due to the hysteresis of the air flow, the wheel speed will reach a local peak point before entering the step-up phase.

[0099] 6) The wheels will then continue the control cycle of "decompression-maintaining pressure-step-increasing pressure", and the peak wheel speed point will always appear during the step-increasing pressure period.

[0100] Based on the dynamic analysis of a single wheel of the vehicle, the following dynamic equations (1.1) and (1.2) can be obtained. For quality, is the wheel speed, is the ground friction, is the rolling resistance, is the air resistance, is the road adhesion coefficient, is the normal force between the wheel and the ground.

[0101] (1.1)

[0102] (1.2)

[0103] Ignoring the effects of rolling resistance and air resistance, we can obtain formula (1.3):

[0104] (1.3)

[0105] According to the relationship between the road adhesion coefficient and the tire slip rate, when the tire slip rate is slightly less than the optimal slip rate control point, that is, when the wheel is in the peak range of the road adhesion coefficient, the road adhesion coefficient Tire slip rate The relationship is as follows (1.4). is the road adhesion coefficient at peak wheel speed, is the optimal slip rate control point.

[0106] (1.4)

[0107] Substituting equation (1.4) into equation (1.3), we get equation (1.5):

[0108] (1.5)

[0109] because 、 、 and are all constant values. It can be seen that when the wheel is in the stable range of road adhesion coefficient, the wheel acceleration and slip rate The smaller the tire slip rate, the smaller the wheel acceleration and the slower the wheel speed decreases.

[0110] Therefore, refer to Figure 2 , the reference vehicle speed estimation method during ABS control is as follows:

[0111] 1) At the peak wheel speed point, the wheel acceleration approaches 0. According to formula (1.5), the slip rate also approaches the minimum value. The difference between the vehicle speed and the wheel speed is small. The current maximum wheel speed can be taken. As a reference speed :

[0112] (1.6)

[0113] 2) For the interval between adjacent peak points, assuming that the time interval between two adjacent local peak points is short enough, the slip rate always remains at the minimum value; according to formula (1.5), the wheel acceleration also remains at a fixed value, and the vehicle is decelerating uniformly. At this time, the line connecting the two adjacent peak points is approximately a straight line. Since the slip rate always remains at the minimum value, the difference between the vehicle speed and the wheel speed is small. Therefore, the slope between the adjacent peak points can be taken as the deceleration of the reference speed. ,in, is the maximum wheel speed at the previous peak point, The time interval between adjacent peak points:

[0114] (1.7)

[0115] It should be noted that for the reference deceleration of the first adjacent peak point interval, the difference in road adhesion coefficient should be assigned Different constant values ; For the other adjacent peak point intervals, the previous speed peak point exists, that is, When exists, use formula (1.7) to calculate . is the maximum wheel speed at the previous peak point at the current sampling moment, It is the maximum wheel speed of the first two peak points at the current sampling moment.

[0116] 3) Based on the reference vehicle speed at the peak point and the reference deceleration within the adjacent peak interval, the estimated vehicle speed during the entire ABS control process can be calculated; in particular, when the estimated vehicle speed is less than the current wheel speed, the current maximum wheel speed should be used. As the reference speed. is the reference speed at the previous moment, is the reference deceleration calculated according to formula (1.7), The time difference between the current moment and the previous moment:

[0117] (1.8)

[0118] 4) For the selection of peak point, according to the current maximum wheel speed Calculate the current maximum wheel acceleration in real time ,when Meet the conditions When the wheel speed reaches its local maximum, it is closest to the actual vehicle speed. Furthermore, since the wheel speed peak in the ABS control cycle always occurs during the initial step-by-step pressure increase, this can be used to filter out any identified false peaks, reducing the interference of noise peaks on the reference vehicle speed calculation.

[0119] 2. Reference speed estimation under vehicle turning conditions

[0120] Under extreme conditions such as braking, accelerating, and turning, the vehicle's lateral acceleration increases, and the roll and steering angles become excessive. On low-adhesion roads, oversteer or understeer can easily occur. In severe cases, this can cause the vehicle to roll over, resulting in an accident and being extremely dangerous. Therefore, most heavy-duty vehicles are currently equipped with an ESC module to prevent this. The ESC module uses an IMU to measure the vehicle's longitudinal acceleration, lateral acceleration, and yaw rate during driving, compares the vehicle's actual driving state with the driver's expectations, and controls the vehicle's motion by controlling engine torque and applying braking force to the wheels.

[0121] Under extreme conditions of excessive lateral acceleration and steering angle, wheel speeds can vary significantly. Furthermore, when ESC applies braking force to a single wheel, the speed of that particular wheel can drop dramatically. This makes it impossible to accurately calculate a reference speed by selecting a single wheel speed or filtering all wheel speeds. This is significantly different from the reference speed calculation used during ABS control. Therefore, the lateral acceleration and yaw rate signals from the IMU can be used to analyze the vehicle's cornering dynamics and select the most appropriate wheel speed for reference speed calculation.

[0122] For commercial vehicles, when the vehicle oversteers, ESC will apply instant braking to the outer front wheel, generating a yaw moment in the opposite direction of the yaw; when the vehicle understeers, ESC will apply instant braking to the inner front wheel, generating a yaw moment in the same direction of the yaw. On low-adhesion roads, when the vehicle has a tendency to roll, the inner wheel and the drive wheel will also slip. Therefore, the wheel speed of the outer non-driven rear wheel is selected. Calculate the reference vehicle speed. The turning process of the vehicle can be regarded as multiple motion intervals with very small time intervals. The vehicle motion in each interval is the superposition of the circular motion around the turning center and the vehicle's own yaw motion. Then, the wheel speed of the outer non-driven rear wheel is It can be expressed by formula (2.1), where is the angular velocity of the vehicle in circular motion around the center of the turning circle, is the radius of the vehicle's circular motion around the center of the turning circle, is the vehicle yaw angular velocity, Half wheelbase.

[0123] (2.1)

[0124] From formula (2.1), we can get the angular velocity of circular motion: The expression (2.2):

[0125] (2.2)

[0126] Due to the lateral acceleration of the vehicle, that is, the centripetal acceleration of the outer wheels , we get formula (2.3):

[0127] (2.3)

[0128] The speed of the vehicle's center of mass when it is traveling, that is, the vehicle's reference speed for:

[0129] (2.4)

[0130] Substituting equations (2.2) and (2.3) into equation (2.4), we get:

[0131] (2.5)

[0132] According to formula (2.5), the reference vehicle speed can be obtained by the wheel speed measured by the outer non-driven rear wheel speed sensor, the yaw angular velocity and lateral acceleration measured by the IMU, and the vehicle's wheelbase.

[0133] 3. Reference speed estimation under other working conditions

[0134] In real vehicles, wheel speed is determined through wheel speed sensor signals. Common wheel speed sensors include magnetoelectric / inductive wheel speed sensors (WSS) and Hall-effect wheel speed sensors (AWSS). Both WSS and AWSS output raw sensor signals that are filtered, amplified, and shaped into square wave pulses by signal processing circuits before being transmitted to the ECU software for wheel speed calculation. At low wheel speeds, the wheel speed calculation recognizes fewer wheel speed pulses per cycle, resulting in large calculation errors. Complex wheel speed calculations are unsuitable at these times. Therefore, at low vehicle speeds, the average wheel speed among several sets of wheel speed information is prioritized as the reference speed, referring to equation (3.1), where n is the number of wheels.

[0135] (3.1)

[0136] It should be noted that when using the vehicle wheel speed , yaw angular velocity and lateral acceleration Before calculating the reference speed, the original signal can be processed by a first-order low-pass filter. The filtering formula is (3.2), where: For output, is the signal input, is the output at the previous moment, is the execution step length, For the delay time parameter:

[0137] (3.2)

[0138] Figure 3 This is a flow chart of a specific embodiment. First, the input signal is filtered using the sampling formula (3.2). Then the wheel speed is detected to see if it is too low. If it is too low, the reference vehicle speed is calculated according to the formula (3.1). Otherwise, the brake pedal signal is detected. If the brake pedal signal exists, the ABS status flag is detected. If the ABS status flag exists, the ABS status flag is detected according to the The ABS step-boost state determines whether it is at its peak. If it is at its peak, the reference speed is the maximum wheel speed. If it is not at its peak, the reference speed is calculated according to Equation (1.8). If the ABS status flag is not present, the reference speed is the maximum wheel speed. If there is no brake pedal signal, the vehicle detects whether it is in a cornering condition. If so, the reference speed is calculated according to Equation (2.5). Otherwise, the reference speed is the maximum wheel speed.

[0139] The above describes in detail an embodiment of a method for estimating the longitudinal reference speed of a vehicle applicable to multiple working conditions. Based on the method for estimating the longitudinal reference speed of a vehicle applicable to multiple working conditions described in the above embodiment, an embodiment of the present invention also provides a system for estimating the longitudinal reference speed of a vehicle applicable to multiple working conditions corresponding to the method.

[0140] Figure 4 This is a schematic block diagram of the structure of a vehicle longitudinal reference speed estimation system applicable to multiple operating conditions, provided by an embodiment of the present invention. This system can be divided into multiple functional modules based on their functions. A module, as used herein, refers to a series of computer program segments stored in memory that can be executed by at least one processor and perform a fixed function.

[0141] Vehicle low-speed state detection module: detects whether the vehicle is in a low-speed running state. If so, it triggers the first longitudinal reference vehicle speed estimation module; otherwise, it triggers the brake pedal signal detection module.

[0142] Brake pedal signal detection module: detects whether there is a brake pedal signal. If so, it triggers the ABS control condition detection module; otherwise, it triggers the turning condition detection module.

[0143] ABS control working condition detection module: detects whether the vehicle is in the ABS control working condition according to the ABS status flag bit, and if so, triggers the second longitudinal reference vehicle speed estimation module, otherwise triggers the fourth longitudinal reference vehicle speed estimation module.

[0144] Turning condition detection module: detects whether the vehicle is in a turning condition, and if so, triggers the third longitudinal reference vehicle speed estimation module; otherwise, triggers the fourth longitudinal reference vehicle speed estimation module.

[0145] The first longitudinal reference vehicle speed estimation module estimates the vehicle longitudinal reference vehicle speed using a first longitudinal reference vehicle speed estimation strategy.

[0146] The second longitudinal reference vehicle speed estimation module estimates the vehicle longitudinal reference vehicle speed using the second longitudinal reference vehicle speed estimation strategy.

[0147] The third longitudinal reference vehicle speed estimation module estimates the vehicle longitudinal reference vehicle speed using the third longitudinal reference vehicle speed estimation strategy.

[0148] The fourth longitudinal reference vehicle speed estimation module estimates the vehicle longitudinal reference vehicle speed using the fourth longitudinal reference vehicle speed estimation strategy.

[0149] The vehicle longitudinal reference speed estimation system applicable to multiple working conditions of this embodiment is used to implement the aforementioned vehicle longitudinal reference speed estimation method applicable to multiple working conditions. Therefore, the specific implementation methods of this system can be seen in the embodiment section of the vehicle longitudinal reference speed estimation method applicable to multiple working conditions in the previous text. Therefore, its specific implementation methods can refer to the descriptions of the corresponding embodiments of each part and will not be elaborated here.

[0150] In addition, since the vehicle longitudinal reference speed estimation system applicable to multiple working conditions of this embodiment is used to implement the aforementioned vehicle longitudinal reference speed estimation method applicable to multiple working conditions, its function corresponds to that of the aforementioned method and will not be repeated here.

[0151] This embodiment provides a vehicle equipped with the vehicle longitudinal reference speed estimation system applicable to multiple working conditions according to the above embodiment, and executing the vehicle longitudinal reference speed estimation method applicable to multiple working conditions according to the above embodiment.

[0152] The above disclosure is only a preferred embodiment of the present invention, but the present invention is not limited thereto. Any non-creative changes that can be thought of by those skilled in the art, as well as several improvements and modifications made without departing from the principles of the present invention, should fall within the scope of protection of the present invention.

Claims

1. A vehicle longitudinal reference speed estimation method applicable to multiple working conditions, characterized in that: The following steps are involved: S1, detect whether the vehicle is in a low-speed running state, if the first longitudinal reference speed estimation strategy is used to estimate the longitudinal reference speed of the vehicle, including the formula Calculate the current vehicle longitudinal reference speed ,in is the current wheel speed of all wheels, is the number of wheels, otherwise go to step S2; S2, detect whether there is a brake pedal signal, if so, go to step S3, otherwise go to step S4; S3, detecting whether the vehicle is in an ABS control condition based on the ABS status flag, and if so, estimating the vehicle longitudinal reference speed using the second longitudinal reference speed estimation strategy; otherwise, estimating the vehicle longitudinal reference speed using the fourth longitudinal reference speed estimation strategy; The second longitudinal reference vehicle speed estimation strategy is used to estimate the vehicle longitudinal reference vehicle speed, specifically including: Detect whether the vehicle wheel speed is at the peak point; If so, estimating the vehicle longitudinal reference speed using a fourth longitudinal reference speed estimation strategy; If not, calculate the peak interval reference speed deceleration using the following formula , Where, is the maximum wheel speed at the previous peak point at the current sampling moment, is the maximum wheel speed of the first two peak points at the current sampling moment, is a constant value; The current vehicle longitudinal reference speed is calculated using the following formula , Where, is the vehicle longitudinal reference speed at the previous sampling moment, is the time interval between two samplings; S4, detecting whether the vehicle is in a turning condition, and if so, estimating the vehicle longitudinal reference speed using the third longitudinal reference speed estimation strategy; otherwise, estimating the vehicle longitudinal reference speed using the fourth longitudinal reference speed estimation strategy; The third longitudinal reference vehicle speed estimation strategy is used to estimate the vehicle longitudinal reference vehicle speed, specifically including: Get the vehicle's yaw rate , half wheelbase and the radius of the vehicle's circular motion around the center of the turning circle ; The centripetal acceleration of the outer wheel is calculated using the following formula: , Where, is the wheel speed of the outer non-driven rear wheel; The current vehicle longitudinal reference speed is calculated using the following formula , ； The fourth longitudinal reference speed estimation strategy is used to estimate the longitudinal reference speed of the vehicle, specifically including: As the current vehicle longitudinal reference speed .

2. The vehicle longitudinal reference speed estimation method applicable to multiple working conditions according to claim 1, characterized in that: Step S1 detects whether the vehicle is in a low-speed running state, specifically including: Get the current wheel speed of all wheels , and filter out the current maximum wheel speed ; Determine the current maximum wheel speed Is it less than the wheel speed threshold? If so, it is determined that the vehicle is in a low-speed running state; otherwise, it is determined that the vehicle is not in a low-speed running state.

3. The vehicle longitudinal reference speed estimation method applicable to multiple working conditions according to claim 1, characterized in that: Detect whether the vehicle wheel speed is at the peak point, specifically including: By the current maximum wheel speed Calculate the current maximum wheel acceleration ; Determine the current maximum wheel acceleration Whether the conditions are met , and the vehicle is in ABS step-boost state; is the maximum wheel acceleration at the previous sampling moment; If so, the vehicle wheel speed is at the peak point, otherwise it is not at the peak point.

4. The vehicle longitudinal reference speed estimation method applicable to multiple working conditions according to claim 1, characterized in that: After obtaining the vehicle parameters, the vehicle parameters are filtered, where the vehicle parameters include the current wheel speed of all wheels , vehicle yaw rate , the centripetal acceleration of the outer wheel during movement .

5. A vehicle longitudinal reference speed estimation system applicable to multiple working conditions, characterized in that: The system is implemented based on the method according to any one of claims 1 to 4, including: Vehicle low-speed state detection module: detects whether the vehicle is in a low-speed running state, and if so, triggers the first longitudinal reference vehicle speed estimation module; otherwise, triggers the brake pedal signal detection module; Brake pedal signal detection module: detects whether there is a brake pedal signal. If so, it triggers the ABS control condition detection module; otherwise, it triggers the turning condition detection module; ABS control working condition detection module: detects whether the vehicle is in the ABS control working condition according to the ABS status flag bit, and triggers the second longitudinal reference vehicle speed estimation module if it is, otherwise triggers the fourth longitudinal reference vehicle speed estimation module; Turning condition detection module: detects whether the vehicle is in a turning condition, and if so, triggers the third longitudinal reference vehicle speed estimation module; otherwise, triggers the fourth longitudinal reference vehicle speed estimation module; A first longitudinal reference vehicle speed estimation module is configured to estimate the vehicle longitudinal reference vehicle speed using a first longitudinal reference vehicle speed estimation strategy; A second longitudinal reference vehicle speed estimation module is configured to estimate the vehicle longitudinal reference vehicle speed using a second longitudinal reference vehicle speed estimation strategy; A third longitudinal reference vehicle speed estimation module is configured to estimate the vehicle longitudinal reference vehicle speed using a third longitudinal reference vehicle speed estimation strategy; The fourth longitudinal reference vehicle speed estimation module estimates the vehicle longitudinal reference vehicle speed using the fourth longitudinal reference vehicle speed estimation strategy.

6. A vehicle, characterized in that: The system according to claim 5 is configured to execute the method according to any one of claims 1 to 4.

Images