Vehicle longitudinal reference speed estimation method and system suitable for multiple working conditions and vehicle

Abstract

The invention relates to the field of vehicle speed estimation, and particularly discloses a vehicle longitudinal reference speed estimation method and system suitable for multiple working conditions and a vehicle. Whether the vehicle is in a low-speed running state is detected, if yes, the vehicle longitudinal reference speed is estimated by using a first longitudinal reference speed estimation strategy, and if not, whether a brake pedal signal exists is detected; if yes, whether the vehicle is in an ABS control working condition or not is detected according to the ABS state flag bit, and if not, whether the vehicle is in a turning working condition or not is detected; if the vehicle is in the ABS control working condition, the second longitudinal reference vehicle speed estimation strategy is used for estimating the longitudinal reference vehicle speed of the vehicle, if the vehicle is in the turning working condition, the third longitudinal reference vehicle speed estimation strategy is used for estimating the longitudinal reference vehicle speed of the vehicle, and the fourth longitudinal reference vehicle speed estimation strategy is used for estimating the longitudinal reference vehicle speed of the vehicle. Vehicle longitudinal reference speed estimation is carried out by considering different working conditions, and the accuracy of the vehicle longitudinal reference speed estimation result and the vehicle operation stability are improved.

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] The estimation of parameters and states during vehicle motion is one of the keys to chassis domain control technology. Among them, the estimation and calculation of the longitudinal reference speed of the vehicle is crucial in the vehicle's anti-lock braking system (ABS) and electronic stability control system (ESC). At present, most commercial vehicles are not equipped with higher-precision speed sensors and longitudinal acceleration sensors due to cost issues or sensor installation process limitations. Therefore, in practical applications, it is necessary to use a certain state estimation algorithm based on the sensor configuration of mass-produced models to estimate the longitudinal reference speed of the whole vehicle. In addition, from the perspective of system reliability requirements, the estimated longitudinal speed of the whole vehicle obtained by the state estimation method can be compared with the physical value measured by the actual speed sensor, so as to identify the possible faults of the current sensor in real time and effectively, and further ensure the accuracy of the whole vehicle speed information used by the system.

[0003] However, the traditional method for estimating the longitudinal reference speed of a vehicle does not consider the influence of various working conditions. The patent application with publication number CN113635908A discloses a method for calculating the reference speed of an ABS, which uses fuzzy logic to calculate the first reference speed; uses other methods to calculate the second reference speed, and the other methods refer to methods for calculating the speed other than the fuzzy logic method; uses fuzzy logic to determine the first reference speed fusion weight and the second reference speed fusion weight respectively; and determines the ABS reference speed according to the first reference speed fusion weight, the second reference speed fusion weight, the first reference speed and the second reference speed. However, the complexity of the vehicle's driving conditions is not considered, and the fuzzy rules for the credibility of the wheel speed of each wheel are established under different driving conditions such as vehicle acceleration, deceleration, and gliding, which affects the accuracy of the estimation result of the longitudinal reference speed of the vehicle, and further affects the stability of vehicle operation. 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, estimation strategies are separately formulated for different working conditions to estimate the vehicle longitudinal reference speed, thereby improving the accuracy of the vehicle longitudinal reference speed estimation result 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 longitudinal reference speed of a vehicle applicable to multiple working conditions, comprising the following steps: S1, detecting whether the vehicle is in a low-speed running state, if so, using the first longitudinal reference vehicle speed estimation strategy to estimate the longitudinal reference vehicle speed of the vehicle, otherwise executing step S2; S2, detect whether there is a brake pedal signal, if yes, go to step S3, otherwise go to step S4; S3, detecting whether the vehicle is in an ABS control condition according to the ABS state flag, and if so, estimating the longitudinal reference speed of the vehicle using the second longitudinal reference speed estimation strategy, otherwise estimating the longitudinal reference speed of the vehicle using the fourth longitudinal reference speed estimation strategy; S4, detecting whether the vehicle is in a turning condition, and if so, using the third longitudinal reference vehicle speed estimation strategy to estimate the vehicle longitudinal reference vehicle speed, otherwise using the fourth longitudinal reference vehicle speed estimation strategy to estimate the vehicle longitudinal reference vehicle speed.

[0006] In an optional implementation, 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 ;in is the number of wheels; 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.

[0007] In an optional implementation, estimating the longitudinal reference speed of the vehicle using the first longitudinal reference speed estimation strategy specifically includes: The current vehicle longitudinal reference speed is calculated by the following formula , .

[0008] In an optional implementation, estimating the longitudinal reference vehicle speed of the vehicle using the second longitudinal reference vehicle speed estimation strategy specifically includes: Detect whether the vehicle wheel speed is at the peak point; If so, estimating the longitudinal reference speed of the vehicle using a fourth longitudinal reference speed estimation strategy; If not, calculate the peak interval reference speed deceleration using the following formula ,

[0009] In the formula, 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 by the following formula ,

[0010] In the formula, is the longitudinal reference speed of the vehicle at the previous sampling moment, is the time interval between two samplings.

[0011] In an optional implementation, detecting whether the vehicle wheel speed is at a peak point specifically includes: By 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.

[0012] In an optional implementation, estimating the longitudinal reference speed of the vehicle using a third longitudinal reference speed estimation strategy specifically includes: 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 by the following formula: ,

[0013] In the formula, is the wheel speed of the outer non-driven rear wheel; The current vehicle longitudinal reference speed is calculated by the following formula , .

[0014] 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 motion .

[0015] In an optional implementation, estimating the longitudinal reference vehicle speed of the vehicle using a fourth longitudinal reference vehicle speed estimation strategy specifically includes: The current maximum wheel speed As the current vehicle longitudinal reference speed .

[0016] 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 is implemented based on any of the above methods, 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 state flag, and if so, triggers the second longitudinal reference vehicle speed estimation module, 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: estimates the longitudinal reference vehicle speed of the vehicle using a first longitudinal reference vehicle speed estimation strategy; A second longitudinal reference vehicle speed estimation module: estimates the longitudinal reference vehicle speed of the vehicle using a second longitudinal reference vehicle speed estimation strategy; A third longitudinal reference vehicle speed estimation module: estimates 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 longitudinal reference vehicle speed of the vehicle using the fourth longitudinal reference vehicle speed estimation strategy.

[0017] 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.

[0018] The invention provides a method and system for estimating longitudinal reference speed of a vehicle applicable to multiple working conditions, and a vehicle. Compared with the prior art, the invention has the following beneficial effects: first, whether the vehicle is in a low-speed running state is detected. If the vehicle is in a low-speed running state, the first longitudinal reference speed estimation strategy is used to estimate the longitudinal reference speed of the vehicle. If the vehicle is not in a low-speed running state, the vehicle further detects whether there is a brake pedal signal. If there is a brake pedal signal, the vehicle is again detected to be in an ABS control working condition. If there is no brake pedal signal, the vehicle is again detected to be in a turning working condition. The second longitudinal reference speed estimation strategy is used to estimate the longitudinal reference speed of the vehicle under the ABS control working condition. The third longitudinal reference speed estimation strategy is used to estimate the longitudinal reference speed of the vehicle under the turning working condition. The fourth longitudinal reference speed estimation strategy is used to estimate the longitudinal reference speed of the vehicle under other working conditions. The invention considers multiple working conditions such as low-speed running, ABS control working condition, turning working condition, etc., considers the running conditions under different working conditions, and separately formulates estimation strategies for different working conditions to estimate the longitudinal reference speed of the vehicle, thereby improving the accuracy of the longitudinal reference speed estimation result of the vehicle, and thus improving the running stability of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0020] Figure 1 It 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.

[0021] Figure 2 It is a schematic diagram of the changes in wheel-end control pressure and speed during ABS control.

[0022] Figure 3 It is a flow chart of a specific embodiment of a method for estimating longitudinal reference vehicle speed of a vehicle applicable to multiple working conditions provided by the present invention.

[0023] Figure 4 The present invention is a schematic block diagram of a vehicle longitudinal reference speed estimation system applicable to multiple working conditions provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] 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 the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0026] Figure 1 1 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 subject may be a vehicle longitudinal reference speed estimation system applicable to multiple working conditions. The vehicle longitudinal reference speed estimation method applicable to multiple working conditions provided in the embodiment of the present invention is executed by a computer device, and accordingly, the vehicle longitudinal reference speed estimation system applicable to multiple working conditions runs in the computer device. According to different requirements, the order of the steps in the flowchart can be changed, and some can be omitted.

[0027] like Figure 1 As shown, the method includes the following steps.

[0028] S1, detecting whether the vehicle is in a low-speed running state, if so, using the first longitudinal reference vehicle speed estimation strategy to estimate the longitudinal reference vehicle speed of the vehicle, otherwise executing step S2.

[0029] In this embodiment, the reference vehicle speed calculation takes into account the situation where the vehicle speed is extremely low, analyzes the characteristics of the wheel speed signal under the situation where the vehicle speed is extremely low, and provides a calculation formula for the reference vehicle speed under this situation.

[0030] 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.

[0031] When the vehicle is in a low-speed running state, the first longitudinal reference vehicle speed estimation strategy is used to estimate the vehicle longitudinal reference vehicle speed, specifically including calculating the current vehicle longitudinal reference vehicle speed by the following formula: , .

[0032] S2, detect whether there is a brake pedal signal, if so, go to step S3, otherwise go to step S4.

[0033] 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 according to the ABS control condition. When no brake pedal signal is present, the vehicle longitudinal reference speed is estimated according to the turning condition.

[0034] S3, detecting whether the vehicle is in an ABS control condition according to the ABS status flag, and if so, using the second longitudinal reference speed estimation strategy to estimate the vehicle's longitudinal reference speed, otherwise using the fourth longitudinal reference speed estimation strategy to estimate the vehicle's longitudinal reference speed.

[0035] In this embodiment, when there is a brake pedal signal, the second longitudinal reference vehicle speed estimation strategy is used to estimate the vehicle longitudinal reference vehicle speed in the ABS control condition, otherwise the fourth longitudinal reference vehicle speed estimation strategy is used to estimate the vehicle longitudinal reference vehicle speed.

[0036] The method of estimating the longitudinal reference speed of the vehicle using the second longitudinal reference speed estimation strategy specifically includes the following steps.

[0037] Step 1: Detect whether the vehicle wheel speed is at a peak point.

[0038] In this embodiment, the wheel speed acceleration is used to determine whether the vehicle wheel speed is at the peak point. 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.

[0039] Step 2: If yes, use the fourth longitudinal reference vehicle speed estimation strategy to estimate the vehicle longitudinal reference vehicle speed.

[0040] Step 3, if not, calculate the peak interval reference speed deceleration using the following formula ,

[0041] In the formula, 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.

[0042] Step 4: Calculate the current vehicle longitudinal reference speed using the following formula: ,

[0043] In the formula, is the longitudinal reference speed of the vehicle at the previous sampling moment, is the time interval between two samplings.

[0044] This embodiment takes into account the wheel speed change 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 pressurization. Based on this, the identified pseudo peaks can be filtered to reduce the interference of noise peaks on the reference vehicle speed calculation.

[0045] 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 .

[0046] S4, detecting whether the vehicle is in a turning condition, and if so, using the third longitudinal reference vehicle speed estimation strategy to estimate the vehicle longitudinal reference vehicle speed, otherwise using the fourth longitudinal reference vehicle speed estimation strategy to estimate the vehicle longitudinal reference vehicle speed.

[0047] 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.

[0048] In this embodiment, the third longitudinal reference vehicle speed estimation strategy is used to estimate the longitudinal reference vehicle speed of the vehicle, which specifically includes the following steps.

[0049] 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 .

[0050] Step 2: Calculate the centripetal acceleration of the outer wheel using the following formula: ,

[0051] In the formula, is the speed of the outside non-driven rear wheel.

[0052] Step 3: Calculate the current vehicle longitudinal reference speed using the following formula: , .

[0053] The reference speed calculation of this embodiment takes into account the vehicle turning condition (including ESC activation), performs vehicle kinematic analysis under turning conditions, and provides a calculation formula for the reference speed under such conditions. At the same time, when ESC is activated, the reference speed calculation selects the IMU sensor signal as the input source, and the reference speed can be obtained through the outer non-driven rear wheel speed, the yaw rate and lateral acceleration measured by the IMU, and the wheelbase of the vehicle, avoiding the influence of large wheel speed differences under extreme conditions on the reference speed calculation.

[0054] In order to further understand the present invention, each operating condition is described in further detail below.

[0055] 1. Reference vehicle speed estimation under full braking When the vehicle brakes due to the driver pressing the brake pedal, the estimation of the reference vehicle speed during ABS control should be considered. The ABS system is designed to control the tire slip rate to maintain 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: 1) Braking starts. This is the initial peak point of wheel speed. Braking pressure builds up and wheel speed starts to decrease. 2) When the wheel end acceleration is lower than the threshold value 1, the brake pressure enters the high pressure holding stage and the wheel speed continues to decrease; 3) When the slip rate reaches the threshold value, the wheel becomes unstable, the brake pressure enters the decompression stage, the wheel speed continues to decrease, but the wheel end acceleration begins to increase; 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; 5) When the wheel-end acceleration decreases and is lower than the threshold value 2, the wheel is stable, the brake pressure enters the step-up stage, the wheel speed continues to increase, and the wheel-end acceleration gradually decreases. At this time, the wheel has gone through the decompression and pressure maintenance of the previous stage. Due to the hysteresis of the air flow, the wheel speed will reach a local peak point when entering the step-up stage; 6) The wheels will then continue the control cycle of "decompression-maintaining pressure-step pressure increase", and the peak wheel speed point will always appear during the step pressure increase period.

[0056] Based on the dynamic analysis of a single wheel of the vehicle, the following dynamic equations (1.1) and (1.2) can be obtained. Among them, 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.

[0057] (1.1) (1.2) Ignoring the effects of rolling resistance and air resistance, we can obtain equation (1.3): (1.3) 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). Among them, is the road adhesion coefficient at the peak wheel speed, is the optimal slip rate control point.

[0058] (1.4) Substituting equation (1.4) into equation (1.3), we get equation (1.5): (1.5) because , , and are all constant values. It can be seen that when the wheel is in the stable range of the 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.

[0059] Therefore, refer to Figure 2 , the reference vehicle speed estimation method during ABS control is as follows: 1) At the peak point of wheel speed, 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 : (1.6) 2) For the interval within adjacent peak points, assuming that the time interval between two adjacent local peak points is short enough, the slip rate will always remain at the minimum value; according to formula (1.5), the wheel acceleration will also remain at a fixed value, and the vehicle will decelerate uniformly. At this time, the line between the two adjacent peak points is approximately a straight line, and because the slip rate has always remained at the minimum value, the difference between the vehicle speed and the wheel speed is small, so the slope between adjacent peak points can be taken as the deceleration of the reference speed. ,in, is the maximum wheel speed at the previous peak point, is the time interval between adjacent peak points: (1.7) 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 round speed peak point exists, that is, When it 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.

[0060] 3) Based on the reference vehicle speed at the peak point and the reference deceleration in 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 taken. 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: (1.8) 4) For the selection of the peak point, according to the current maximum wheel speed Calculate the current maximum wheel acceleration in real time ,when Satisfy the conditions When the wheel speed reaches the local maximum point, the wheel speed is closest to the actual vehicle speed. In addition, since the peak point of the wheel speed in the ABS control cycle always appears during the period when the wheel starts step-by-step pressure increase, the identified pseudo peak value can be filtered out to reduce the interference of the noise peak on the reference vehicle speed calculation.

[0061] 2. Reference vehicle speed estimation under vehicle turning conditions In extreme conditions such as steering braking, steering acceleration, and sharp turns, the vehicle's lateral acceleration increases, and the roll angle and steering angle are too large. On low-adhesion roads, oversteering or understeering is likely to occur, which can cause the vehicle to roll over in severe cases, causing accidents and great danger. Therefore, most heavy-duty vehicles are currently equipped with ESC function modules to prevent the above situations from happening. The ESC module uses IMU to measure the longitudinal acceleration, lateral acceleration, and yaw rate information during vehicle driving, compares the difference between the actual driving state of the vehicle and the driver's expectations, and controls the body's motion posture by controlling the engine torque and applying braking force to the wheels.

[0062] Under extreme conditions of excessive lateral acceleration and steering angle, the wheel speeds of the vehicle vary greatly. In addition, when ESC applies braking force to a single wheel, the speed of one wheel will drop sharply, and it is impossible to obtain a more accurate reference speed by selecting a certain wheel speed or filtering all wheel speeds, which is very different from the calculation of the reference speed during ABS control. Therefore, the lateral acceleration and yaw rate signals of the IMU can be used to perform dynamic analysis of the vehicle's turning process and select the most suitable wheel speed for reference speed calculation.

[0063] 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 direction; when the vehicle understeers, ESC will apply instant braking to the inner front wheel, generating a yaw moment in the same direction as the yaw direction. On low-adhesion roads, when the vehicle has a tendency to roll, the inner wheels and drive wheels will also slip. Therefore, the wheel speed of the outer non-driven rear wheel should be 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 center of the turning circle 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 moving in a circle 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.

[0064] (2.1) From formula (2.1), we can get the angular velocity of circular motion: The expression (2.2) is: (2.2) Due to the lateral acceleration of the vehicle, that is, the centripetal acceleration of the outer wheel when moving , we get formula (2.3): (2.3) The speed of the center of mass of the vehicle when it is moving, that is, the vehicle reference speed for: (2.4) Substituting equation (2.2) and equation (2.3) into equation (2.4), we get: (2.5) 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.

[0065] 3. Reference speed estimation under other working conditions In real vehicles, the wheel speed of the vehicle is obtained through the wheel speed sensor signal. Common wheel speed sensors are magnetoelectric / inductive wheel speed sensor (WSS) and Hall wheel speed sensor (AWSS). Whether it is WSS or AWSS, the original sensor signal output by it must be filtered, amplified, and shaped into a square wave pulse signal by the signal processing circuit before being passed to the ECU software bottom layer for wheel speed calculation. When the wheel speed is low, the wheel speed calculation recognizes fewer wheel speed pulses in each cycle, and the calculation error is large; at this time, it is not suitable to use the wheel speed for complex calculations. Therefore, when the vehicle speed is low, refer to the vehicle speed calculation reference formula (3.1), and give priority to selecting the average wheel speed of several sets of vehicle wheel speed information as the reference vehicle speed, where n is the number of wheels.

[0066] (3.1) It should be noted that when using the vehicle wheel speed , yaw rate 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: (3.2) Figure 3 This is a flow chart of a specific embodiment. First, the input signal is filtered by sampling formula (3.2), and 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 formula (3.1). Otherwise, the brake pedal signal is detected. If there is a brake pedal signal, the ABS status flag is detected. If there is an ABS status flag, the ABS status flag is calculated according to The ABS step boost state determines whether it is at the peak point. When it is at the peak point, the reference vehicle speed is the maximum wheel speed. When it is not at the peak point, the reference vehicle speed is calculated according to formula (1.8). When there is no ABS state flag, the reference vehicle speed is the maximum wheel speed. When there is no brake pedal signal, it detects whether it is in a turning condition. When it is in a turning condition, the reference vehicle speed is calculated according to formula (2.5). Otherwise, the reference vehicle speed is the maximum wheel speed.

[0067] An embodiment of a method for estimating a longitudinal reference speed of a vehicle applicable to multiple working conditions is described in detail above. Based on the method for estimating a 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 a longitudinal reference speed of a vehicle applicable to multiple working conditions corresponding to the method.

[0068] Figure 4 The present invention provides a schematic block diagram of a vehicle longitudinal reference speed estimation system applicable to multiple working conditions. The vehicle longitudinal reference speed estimation system applicable to multiple working conditions can be divided into multiple functional modules according to the functions performed. The module referred to in the present invention refers to a series of computer program segments that can be executed by at least one processor and can complete fixed functions, which are stored in a memory.

[0069] 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.

[0070] 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.

[0071] ABS control working condition detection module: detects whether the vehicle is in the ABS control working condition according to the ABS state flag, and if so, triggers the second longitudinal reference vehicle speed estimation module, otherwise triggers the fourth longitudinal reference vehicle speed estimation module.

[0072] 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.

[0073] The first longitudinal reference vehicle speed estimation module estimates the longitudinal reference vehicle speed of the vehicle using the first longitudinal reference vehicle speed estimation strategy.

[0074] The second longitudinal reference vehicle speed estimation module estimates the longitudinal reference vehicle speed of the vehicle using the second longitudinal reference vehicle speed estimation strategy.

[0075] The third longitudinal reference vehicle speed estimation module estimates the longitudinal reference vehicle speed of the vehicle using the third longitudinal reference vehicle speed estimation strategy.

[0076] The fourth longitudinal reference vehicle speed estimation module estimates the longitudinal reference vehicle speed of the vehicle using the fourth longitudinal reference vehicle speed estimation strategy.

[0077] The vehicle longitudinal reference speed estimation system applicable to multiple working conditions of the present embodiment is used to implement the aforementioned vehicle longitudinal reference speed estimation method applicable to multiple working conditions. Therefore, the specific implementation method of the system can be seen in the embodiment part of the vehicle longitudinal reference speed estimation method applicable to multiple working conditions in the previous text. Therefore, its specific implementation method can refer to the description of the corresponding embodiments of each part, which will not be elaborated here.

[0078] 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.

[0079] This embodiment provides a vehicle, which is equipped with the vehicle longitudinal reference speed estimation system applicable to multiple working conditions of the above embodiment, and executes the vehicle longitudinal reference speed estimation method applicable to multiple working conditions of the above embodiment.

[0080] 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 a person skilled in the art, as well as several improvements and modifications made without departing from the principle of the present invention, should fall within the protection scope of the present invention.

Claims

1. A method for estimating a vehicle longitudinal reference speed applicable to multiple working conditions, characterized in that: The following steps are involved: S1, detecting whether the vehicle is in a low-speed running state, if so, using the first longitudinal reference vehicle speed estimation strategy to estimate the longitudinal reference vehicle speed of the vehicle, otherwise executing step S2; S2, detect whether there is a brake pedal signal, if yes, go to step S3, otherwise go to step S4; S3, detecting whether the vehicle is in an ABS control condition according to the ABS state flag, and if so, estimating the longitudinal reference speed of the vehicle using the second longitudinal reference speed estimation strategy, otherwise estimating the longitudinal reference speed of the vehicle using the fourth longitudinal reference speed estimation strategy; S4, detecting whether the vehicle is in a turning condition, and if so, using the third longitudinal reference vehicle speed estimation strategy to estimate the vehicle longitudinal reference vehicle speed, otherwise using the fourth longitudinal reference vehicle speed estimation strategy to estimate the vehicle longitudinal reference vehicle 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 ;in is the number of wheels; 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 method for estimating the longitudinal reference speed of a vehicle applicable to multiple working conditions according to claim 2, characterized in that: The first longitudinal reference vehicle speed estimation strategy is used to estimate the longitudinal reference vehicle speed of the vehicle, specifically including: The current vehicle longitudinal reference speed is calculated by the following formula , 。 4. The method for estimating the longitudinal reference speed of a vehicle applicable to multiple working conditions according to claim 2, characterized in that: The second longitudinal reference vehicle speed estimation strategy is used to estimate the longitudinal reference vehicle speed of the vehicle, specifically including: Detect whether the vehicle wheel speed is at the peak point; If so, estimating the longitudinal reference speed of the vehicle using a fourth longitudinal reference speed estimation strategy; If not, calculate the peak interval reference speed deceleration using the following formula , In the formula, 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 by the following formula , In the formula, is the longitudinal reference speed of the vehicle at the previous sampling moment, is the time interval between two samplings.

5. The method for estimating the longitudinal reference speed of a vehicle applicable to multiple working conditions according to claim 4, characterized in that: Detect whether the vehicle wheel speed is at the peak point, including: By 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.

6. The method for estimating the longitudinal reference speed of a vehicle applicable to multiple working conditions according to claim 2, characterized in that: The third longitudinal reference vehicle speed estimation strategy is used to estimate the longitudinal reference vehicle speed of the vehicle, 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 by the following formula: , In the formula, is the wheel speed of the outer non-driven rear wheel; The current vehicle longitudinal reference speed is calculated by the following formula , 。 7. The method for estimating the longitudinal reference speed of a vehicle applicable to multiple working conditions according to claim 6, 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 motion .

8. The method for estimating longitudinal reference vehicle speed applicable to multiple working conditions according to any one of claims 2 to 7, characterized in that: The fourth longitudinal reference vehicle speed estimation strategy is used to estimate the longitudinal reference vehicle speed of the vehicle, specifically including: The current maximum wheel speed As the current vehicle longitudinal reference speed .

9. A vehicle longitudinal reference speed estimation system applicable to multiple working conditions, characterized in that: The system is implemented based on the method described in any one of claims 1 to 8, 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 state flag, and if so, triggers the second longitudinal reference vehicle speed estimation module, 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: estimates the longitudinal reference vehicle speed of the vehicle using a first longitudinal reference vehicle speed estimation strategy; A second longitudinal reference vehicle speed estimation module: estimates the longitudinal reference vehicle speed of the vehicle using a second longitudinal reference vehicle speed estimation strategy; A third longitudinal reference vehicle speed estimation module: estimates 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 longitudinal reference vehicle speed of the vehicle using the fourth longitudinal reference vehicle speed estimation strategy.

10. A vehicle, characterized in that: The system according to claim 9 is configured to execute the method according to any one of claims 1 to 8.

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