Side-slip angle calculation device

Abstract

To provide a lateral slip angle calculation device capable of more accurately calculating the lateral slip angle.SOLUTION: A lateral slip angle calculation device includes: a variable adjustment unit 22; and a calculation unit 23. When the yaw rate is denoted as ω, the vehicle speed as V, the gravitational acceleration as g, and the roll angle of the vehicle body as φ, the calculation unit 23 calculates the lateral slip angle β by multiplying the conversion coefficient GB by α=ωV-gφ-k. The conversion coefficient GB is a variable inversely proportional to the square of the vehicle speed V. The variable adjustment unit 22 changes the value of the gradient parameter k that constitutes α according to the roll angle φ. When φ=0, the variable adjustment unit 22 sets k=0, when φ>0 and ωV<gφ, the variable adjustment unit sets k=gφ-ωV, when φ>0 and ωV≥gφ, the variable adjustment unit sets k to a non-zero predetermined value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This disclosure relates to a vehicle skid angle calculation device for calculating the skid angle of a vehicle. [Background technology]

[0002] When a vehicle turns, a sideslip angle occurs. Yaw rate can only detect the direction the vehicle is facing, so in order to estimate the direction of travel of the vehicle, it is necessary to estimate the sideslip angle of the vehicle. Patent Document 1 shows a method for estimating the sideslip angle by combining yaw rate, travel speed, and numerous vehicle parameters. The vehicle parameters include the mass of the vehicle, the distance from the center of gravity to the front axle, the distance from the center of gravity to the rear axle, and cornering power.

[0003] Patent document 2 describes a device for estimating the sideslip angle by further multiplying the product of vehicle speed and yaw rate by a coefficient corresponding to vehicle parameters. Non-patent document 1, paragraphs 13 to 19, describes the normalization of vehicle parameters. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 3368713 [Patent Document 2] Japanese Patent Publication No. 2023-23180 [Non-patent literature]

[0005] [Non-Patent Document 1] "Research on the basic design of automobile handling stability and chassis control based thereon," Masaki Yamamoto, University of Tokyo, Doctoral dissertation (2015) [Overview of the project] [Problems that the invention aims to solve]

[0006] The configuration disclosed in Patent Document 1 requires correct values ​​for vehicle parameters. If the values ​​of the vehicle parameters used to calculate the sideslip angle deviate from the actual values, the error in the sideslip angle will increase. Furthermore, the sideslip angle can be affected by the transverse gradient (so-called cant) of the roadway. The calculation methods disclosed in Patent Documents 1 and 2, etc., do not take into account the effect of the transverse gradient.

[0007] This disclosure is based on the above considerations or observations, and one of its purposes is to provide a lateral slip angle calculation device that can calculate the lateral slip angle more accurately. [Means for solving the problem]

[0008] The skid angle calculation device disclosed herein includes a communication unit (14) that acquires the vehicle speed (V), rotational angular velocity (ω), and roll angle (φ) of the vehicle based on the output signals of an on-board sensor, and a center of gravity parameter (d) that represents the ratio of the distance from the rear axle to the center of gravity to the assumed value of the wheelbase (L). f A memory unit (25) that stores the normalized cornering power (C) and gravitational acceleration (g), an adjustment unit (22) that adjusts the value of the gradient parameter (k), which is a variable for correcting the influence of the transverse gradient of the road on the side-slip angle (β), according to the roll angle (φ), and vehicle speed (V), rotational angular velocity (ω), roll angle (φ), assumed value of wheelbase (L), and center of gravity parameter (d f The system includes a calculation unit (23) that calculates the sideslip angle (β) using the following: ), cornering power (C), gradient parameter (k), and gravitational acceleration (g). The calculation unit calculates a first parameter related to the force acting laterally on the vehicle based on a first multiplication value which is the product of the vehicle speed (V) and rotational angular velocity (ω), a second multiplication value which is the product of the roll angle (φ) and gravitational acceleration (g), and gradient parameter (k). The calculation unit also includes a calculation unit (23) that calculates the sideslip angle (β) using the following: the vehicle speed (V) and the assumed value of the wheelbase (L), and the center of gravity parameter (d fBased on the first parameter, the gravitational acceleration (g), and the cornering power (C), a second parameter, which is a coefficient for approximating the first parameter to the side slip angle, is calculated, and the side slip angle is calculated by multiplying the first parameter by the second parameter.

[0009] According to the above configuration, the value of the gradient parameter (k) that constitutes the first parameter is changed according to the roll angle. The roll angle of the vehicle is a parameter derived from the cross slope. Therefore, according to the above configuration, a more appropriate side slip angle considering the influence of the cross slope can be calculated.

[0010] The reference numerals in parentheses described in the claims indicate the correspondence with the specific means described in the embodiments to be described later as one aspect, and do not limit the technical scope of the present disclosure.

Brief Description of the Drawings

[0011] [Figure 1] It is a block diagram showing the configuration of the side slip angle calculation device. [Figure 2] It is a functional block diagram of the side slip angle calculation device. [Figure 3] It is a diagram showing the lateral force acting on the vehicle during turning. [Figure 4] It is a functional block diagram of the side slip angle calculation device in other embodiments. [Figure 5] It is a functional block diagram of the third calculation module.

Modes for Carrying Out the Invention

[0012] Embodiments of this disclosure will be described below with reference to drawings. This disclosure is not limited to the embodiments described below. The configurations disclosed below may be partially modified without departing from the gist of the work. Multiple modifications included in this disclosure may be combined as appropriate, without creating a technical inconsistency. This disclosure also includes configurations not explicitly stated, which are combinations of multiple modifications. In the following description, components having the same function will be denoted by the same reference numeral, and their specific descriptions may be omitted. If only a part of a configuration is referred to, the descriptions of other parts may apply elsewhere.

[0013] (First Embodiment) Figure 1 is a block diagram showing the configuration of the lateral slip angle calculation device 10 according to the first embodiment. The lateral slip angle calculation device 10 is a computer that calculates the lateral slip angle β based on input signals from an in-vehicle device. The lateral slip angle calculation device 10 includes a processor 11, memory 12, storage 13, and a communication interface 14. The lateral slip angle calculation device 10 may also include an IC (Integrated Circuit) or an FPGA (Field-Programmable Gate Array). Hereafter, "vehicle" may be understood as a vehicle on which the lateral slip angle calculation device 10 is installed.

[0014] The processor 11 is configured to perform calculations based on data received from other in-vehicle devices. The processor 11 may be a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), etc. The memory 12 is a rewritable volatile storage medium. The memory 12 may be RAM (Random Access Memory). The memory 12 may be a component for temporarily holding data received from other in-vehicle devices, as well as calculation results from the processor 11, programs, etc.

[0015] Storage 13 is a rewritable non-volatile memory. Storage 13 is implemented using at least one type of non-transitory tangible storage medium, such as semiconductor memory, magnetic media, and optical media. Storage 13 may include multiple types of storage media, such as ROM (Read Only Memory) and flash memory. Storage 13 stores a sideslip angle calculation program executed by the processor 11. The sideslip angle calculation program may be a program that implements at least some of the functions of the sideslip angle calculation device 10, which is shown as a block in Figure 2. When the processor 11 executes the sideslip angle calculation program, it is equivalent to executing the sideslip angle calculation method.

[0016] The communication interface 14 is a circuit module for the processor 11 to communicate with other in-vehicle devices. The communication interface 14 may include a PHY chip or the like that conforms to the communication standards of the in-vehicle network. The communication interface 14 corresponds to the communication unit.

[0017] The yaw angle calculation device 10 is communicated with the yaw rate sensor 1, the vehicle speed sensor 2, the attitude estimator 3, and the yaw skid prevention device 4. Other ECUs (Electronic Control Units) may be interposed between the yaw rate sensor 10 and the yaw rate sensor 1, etc. The yaw angle calculation device 10 receives the output signals from the yaw rate sensor 1, the vehicle speed sensor 2, and the attitude estimator 3. The yaw rate sensor 1, the vehicle speed sensor 2, the attitude estimator 3, etc., may be configured to receive signals from other sensors in addition to, or instead of, the above-mentioned sensors, as needed. The yaw rate sensor 1, the vehicle speed sensor 2, the attitude estimator 3, etc., are examples of on-board sensors.

[0018] The yaw rate sensor 1 is a sensor that detects the rotational angular velocity (yaw rate) ω in the turning direction of the vehicle. The yaw rate sensor 1 may also be a gyro sensor having three detection axes. The output signal of the yaw rate sensor 1 may be input to the sideslip angle calculation device 10 via a bandpass filter. The bandpass filter block is a circuit for removing high-frequency and low-frequency noise superimposed on the yaw rate ω.

[0019] The vehicle speed sensor 2 is a sensor that outputs a signal indicating the vehicle's travel speed (hereinafter referred to as vehicle speed) V. The vehicle speed sensor 2 may be a so-called wheel speed sensor that detects the speed at which the vehicle's wheels rotate. The vehicle speed sensor 2 may be implemented, for example, using a rotor with multiple teeth formed on its outer circumference and an electromagnetic pickup. Note that the vehicle speed sensor 2 is not limited to the type described above, but may be a sensor of other type as well.

[0020] The attitude estimator 3 is a device that estimates the attitude of a vehicle. For example, the attitude estimator 3 estimates the roll angle φ of the vehicle. The attitude estimator 3 may also be configured to estimate the pitch angle of the vehicle. The attitude estimator 3 outputs data indicating the estimated vehicle attitude, such as the roll angle φ, to the sideslip angle calculation device 10. The output signal of the attitude estimator 3 indicating the roll angle φ may be input to the sideslip angle calculation device 10 via a bandpass filter. The bandpass filter block is a circuit for removing high-frequency and low-frequency noise superimposed on the roll angle φ.

[0021] Vehicle attitude may be estimated (calculated) using various methods. Furthermore, the attitude estimator 3 may be a locator, a navigation device, an inertial measurement unit (IMU), etc. In this embodiment, as an example, the attitude estimator 3 is a locator.

[0022] A locator is a device that generates highly accurate positional information for a vehicle by combining multiple types of sensor data related to the vehicle's behavior through composite positioning. The locator may include a GNSS (Global Navigation Satellite System) receiver, a map memory device, and an inertial sensor. The GNSS receiver is a device that calculates its current position by receiving navigation signals transmitted from positioning satellites that constitute the GNSS. The map memory device is a device that stores map data showing road shapes and road networks. The map data may include data on the curvature and cross gradient (so-called cant) of roads for each road section. The cross gradient may be expressed in angle, radians, or percentage. Note that the map memory device is an optional element and may be omitted. The inertial sensor is a sensor that detects three-dimensional inertial motion. The inertial sensor may include a three-axis accelerometer and a three-axis gyroscope. The aforementioned yaw rate sensor 1 may be integrated with the locator's inertial sensor.

[0023] The locator, acting as an attitude estimator 3, sequentially calculates the direction and amount of vehicle movement based on the output of the inertial sensor and performs a so-called dead reckoning process to determine the current position by combining these calculation results with past estimated positions. The amount of movement per unit time generated based on the output of the inertial sensor corresponds to the vehicle speed V. The locator may estimate the vehicle speed V based on the Doppler velocity observed by the GNSS receiver. The sideslip angle calculation device 10 may also obtain the vehicle speed V from the locator. The sideslip angle calculation device 10 may also use the vehicle speed V detected by the vehicle speed sensor 2 after correcting it based on the speed information obtained by the GNSS receiver / locator. Furthermore, the locator, acting as an attitude estimator 3, calculates the vehicle's roll angle φ based on the detected value of the inertial sensor.

[0024] Furthermore, the attitude estimator 3 may identify the transverse gradient of the road on which the vehicle is traveling based on its position on the map, and output this transverse gradient as the roll angle φ to the lateral slip angle calculation device 10. In addition, the attitude estimator 3 may be configured to identify any of the vehicle speed V, yaw rate ω, and roll angle φ based on the amount of change in position over time within the image frame of one or more landmarks captured by the front camera. The front camera is an on-board camera that captures images of the area in front of the vehicle. Landmarks may be, for example, signs such as traffic signs or road markings such as white lines.

[0025] The anti-skid device 4 is a device that performs anti-skid control. The anti-skid control may include decelerating the vehicle. The anti-skid control may also include automatic control of the steering angle. The anti-skid device 4 performs deceleration control or predetermined steering control when the anti-skid angle β input from the anti-skid angle calculation device 10 exceeds a predetermined value. Note that the anti-skid device 4 is an example of a device that uses the anti-skid angle β. The anti-skid device 4 is an optional element and may be omitted.

[0026] As shown in Figure 2, the lateral slip angle calculation device 10 comprises a scene determination unit 21, a variable adjustment unit 22, a calculation unit 23, and an output value determination unit 24 as functional blocks. The lateral slip angle calculation device 10 uses the assumed value L of the wheelbase and the center of gravity parameter d. f The system includes a storage unit 25 that stores design parameters necessary for calculating the sideslip angle β, such as the normalized cornering power C and the gravitational acceleration g. The storage unit 25 may be implemented using a part of the memory 12 or storage 13.

[0027] The assumed wheelbase value L is the assumed distance between the front axle and the rear axle. If the vehicle is a passenger car, the assumed wheelbase value L may be set to 2.5m, 3.0m, or 3.5m, etc. Center of gravity parameter d f This parameter represents the ratio of the distance from the rear axle to the vehicle's center of gravity to the assumed wheelbase value L. (Center of gravity parameter d) fmay be interpreted as the front-to-rear axle load distribution ratio for the front wheels. Let the load on the front wheels at rest be W f , and the load on the rear wheels be W r . Then, d f = W f / (W f + W r ). W f and W r may be appropriately designed. When the vehicle is a passenger car, the center of gravity parameter d f may be set to 0.5, 0.55, 0.6, etc. The center of gravity parameter d f corresponds to the parameter d f in Non-Patent Document 1.

[0028] The normalized cornering power C is a parameter obtained by dividing the cornering power by the load applied to the wheel. In the present disclosure, the cornering power C may be interpreted as the cornering power of the rear wheels. The cornering power C corresponds to the cornering power C r in Non-Patent Document 1. The gravitational acceleration g may be set to 9.8 (m / sec^2). The data stored in the storage unit 25 is referred to by the scene determination unit 21 and the calculation unit 23.

[0029] The scene determination unit 21 discriminates the driving scene based on the vehicle speed V, dividing it into a stopped state and a driving state. The driving scene may be referred to as the driving state. During driving, it is classified into a straight-ahead state, a turning state, and others. The straight-ahead state is a state where the vehicle is moving straight. The turning state is a state where the vehicle is turning. The scene determination unit 21 may determine whether the current state is a straight-ahead state or a turning state based on the yaw rate ω or the steering angle detected by the steering sensor.

[0030] The scene determination unit 21 may determine that the current state is a straight-ahead state if the yaw rate ω is less than a predetermined value or the steering angle is less than a predetermined value. The scene determination unit 21 may also determine that the current state is a turning state if the yaw rate ω is greater than or equal to a predetermined value or the steering angle is greater than or equal to a predetermined value. If the scene determination unit 21 determines that the current state is a straight-ahead state, it may output a signal to the output value determination unit 24 instructing it to set the sideslip angle β to 0.

[0031] Furthermore, the scene determination unit 21 distinguishes the turning state into a first turning state, a second turning state, a third turning state, and a fourth turning state based on either or both of the roll angle φ and the vehicle speed V. The first turning state is when turning on a road surface with no transverse gradient (i.e., a flat road surface). Turning right or left at an intersection, and changing lanes on a flat road surface correspond to the first turning state.

[0032] In this embodiment, the scene determination unit 21 treats the roll angle φ as a transverse gradient. The roll angle φ used by the lateral slip angle calculation device 10 may be characterized based on dead reckoning processing, reference to map data, or analysis of camera images, as described above. The scene determination unit 21 may determine that a first turning state is occurring if the yaw rate ω is greater than or equal to a predetermined value, or the steering angle is greater than or equal to a predetermined value, and the roll angle φ is 0. The case where the roll angle φ is 0 includes the case where the roll angle φ is small enough to be considered as 0, i.e., approximately 0. The case where the roll angle φ is 0 may also be interpreted as the roll angle φ being less than the gradient threshold ThC. The gradient threshold ThC may be set to a value corresponding to 1.0°, 1.5°, 2.0°, or 2.5°, etc. Note that the roll angle φ may be converted to radians (rad) as appropriate.

[0033] The second turning state is a state in which a road with a transverse gradient of at least the gradient threshold ThC is being turned at a speed of at least the first speed threshold Vth1 and less than the second speed threshold Vth2. The first speed threshold Vth1 may be set to 5 km / h, 10 km / h, etc. The second speed threshold Vth2 may be set to 20 km / h, 30 km / h, or 40 km / h, etc. The second turning state corresponds to a state in which a road with a transverse gradient is being turned at a speed within a predetermined range. The speed range defining the second turning state may be set to a range where no lateral slip angle occurs, either on the inner side or the outer side of the turning direction. A state where a road connecting a highway and a general road or a road connecting two highways (so-called rampway) is being traveled at a low speed to the legal speed corresponds to the second turning state. The scene determination unit 21 may determine that it is the second turning state when the yaw rate ω (or steering angle) is at least a predetermined value, and φ ≧ ThC, and Vth1 < V < Vth2.

[0034] Such a second turning state may be a state in which the centripetal force associated with the turning is provided by the component F1 of gravity parallel to the slope, and no lateral slip angle β occurs either in the inner direction or the outer direction of the turning. When the centripetal force is provided by the component F1 of gravity parallel to the slope, in other words, it may be understood as the case where the component F1 parallel to the slope is greater than the centrifugal force F2. When the mass of the vehicle is m and the turning radius is r, the component F1 of gravity parallel to the slope is F1 = mg·sinφ = mgφ, and the centrifugal force F2 is mV^2 / r = mωV. Fig. 3 conceptually shows the lateral force (i.e., lateral force) acting on the vehicle when turning on a road surface with a transverse gradient. The second turning state may be understood as a state having the relationship of gφ ≧ ωV > 0. In Fig. 3, the illustration of the vertical resistance force and the road surface friction force, etc. is omitted.

[0035] The third turning state is a state in which a road with a transverse gradient of at least the gradient threshold ThC is being turned at a speed of at least the second speed threshold Vth2. The scene determination unit 21 may determine that it is the third turning state when the yaw rate ω (or steering angle) is at least a predetermined value, and φ ≧ ThC, and V ≧ Vth2. The third turning state may be understood as a state where a lateral slip angle β occurs, that is, a scene where the centrifugal force F2 can be greater than the component F1 parallel to the slope.

[0036] The fourth turning state is a state in which a vehicle is turning on a road where the transverse gradient is greater than or equal to the gradient threshold ThC, at a speed less than the first speed threshold Vth1. The fourth turning state corresponds to a state in which a side-slip angle toward the inside may occur, in other words, a state in which the driver needs to turn the steering wheel in the opposite direction to the turning direction. Note that both or either of the first speed threshold Vth1 and the second speed threshold Vth2 may be adjusted according to the roll angle φ. The larger the roll angle φ, the larger the first speed threshold Vth1 and the second speed threshold Vth2 may be set to. Also, if the roll angle φ is less than a predetermined value, the first speed threshold Vth1 may be set to 0. The threshold for a roll angle φ for which Vth1=0 may be set to a value larger than the gradient threshold ThC, such as 2 or 3 times the gradient threshold ThC. In other words, the side-slip angle calculation device 10 may be configured to set Vth1=0 on a normal road.

[0037] The scene determination unit 21 outputs the determination result related to the turning state to the variable adjustment unit 22. Specifically, the scene determination unit 21 outputs a signal to the variable adjustment unit 22 indicating whether the current state is a straight-ahead state, a first turning state, a second turning state, or a third turning state.

[0038] The variable adjustment unit 22 is a block that adjusts the value of the gradient parameter k based on the determination result of the scene determination unit 21. The gradient parameter k is one of the parameters used by the calculation unit 23 when calculating the lateral slip angle β. The gradient parameter k can be understood as a variable for correcting the influence of the transverse gradient of the roadway on the lateral slip angle β. The operation of the variable adjustment unit 22 will be explained together with the operation of the calculation unit 23. The variable adjustment unit 22 inputs the value of the gradient parameter k according to the determination result of the scene determination unit 21 to the calculation unit 23. The variable adjustment unit 22 may be integrated with the scene determination unit 21.

[0039] The calculation unit 23 uses vehicle speed V, yaw rate ω, roll angle φ, assumed wheelbase L, and center of gravity parameter d. fThis block calculates the sideslip angle β using the cornering power C, gradient parameter k, and gravitational acceleration g. The calculation unit 23 calculates the sideslip angle β using the following equations 1 and 2. Equation 1a is the conversion coefficient G defined in equation 2. B This is obtained by substituting into Equation 1. The roll angle φ is expressed in radians. α shown in Equation 3 is G in Equation 1. B It is the element to be multiplied by.

[0040]

number

[0041]

number

[0042]

number

[0043]

number

[0044] For convenience, in this disclosure, α expressed by the following Equation 3 will be referred to as the lateral force-related value. The lateral force-related value α corresponds to the first parameter. The ωV-gφ that constitutes the lateral force-related value α is obtained by subtracting the slope-parallel component F1 from the centrifugal force F2 and dividing the result by the mass m. The first multiplicative value (ωV), which is the product of the vehicle speed V and the yaw rate ω, is a component derived from the centrifugal force F2. The second multiplicative value (gφ), which is the product of the gravitational acceleration g and the roll angle φ, is a component derived from the slope-parallel component F1. The difference between the first and second multiplicative values, ωV-gφ, can be understood as an element corresponding to the force (actually acceleration) that causes the vehicle to slide outward, assuming that friction between the tire and the road surface is ignored. For convenience, ωV-gφ will also be referred to as the differential lateral acceleration.

[0045] Transformation coefficient G BThis parameter is used to convert the lateral acceleration acting on the vehicle into a sideslip angle β. The conversion coefficient G B This corresponds to the second parameter. Transformation coefficient G B This corresponds to the steady-state slip angle gain per unit lateral acceleration. The developers of this disclosure consider a conversion coefficient G to the differential lateral acceleration (ωV-gφ) as one configuration. B They considered calculating the sideslip angle by multiplying by (ωV-gφ)·G. As a result, the developers found that (ωV-gφ)·G B We found that the estimated lateral slip angle can deviate from the true value due to the influence of factors such as transverse gradient, vehicle speed V, road surface friction coefficient, or other factors.

[0046] The gradient parameter k is a parameter introduced based on the above findings. The variable adjustment unit 22 changes the value of the gradient parameter k according to the vehicle's driving state to reduce the error between the estimated value and the true value. Specifically, the variable adjustment unit 22 sets k = gφ - ωV when the vehicle is moving straight, in a second turn, or stationary. When the vehicle is moving straight, stationary, or in a second turn, the sideslip angle β should be 0. By setting k = gφ - ωV, α = 0, which reduces the likelihood of the calculation result of the calculation unit 23 (i.e., the sideslip angle β) being an inappropriate value.

[0047] Ideally, in a straight-line motion, φ=0 and ω=0. Therefore, even if k is a constant value (0), α can be 0. However, in reality, the sensor output value is superimposed with noise or contains errors. Therefore, even in a straight-line motion, φ≠0 and ω≠0 may occur. As a result, if k=0 in a straight-line motion, α≠0 in a real environment. To address this issue, by setting k=gφ-ωV, the risk of the calculation unit 23 outputting a non-zero value as the sideslip angle β in a straight-line motion can be reduced.

[0048] Furthermore, when the vehicle is stopped, β=0, and in practice, α=0 is also required. Since V=0 when the vehicle is stopped, the second term of α, the -gφ component, needs to be canceled out by k. By setting k=gφ-ωV, α=0 even when the vehicle is stopped, and the risk of the calculation unit 23 outputting a non-zero value can be reduced. In another embodiment, in a configuration where the output value of the output value determination unit 24, that is, the estimated value of the final sideslip angle β, is forcibly set to 0 when the vehicle is stopped or moving straight, k can be any value when the vehicle is stopped or moving straight.

[0049] Furthermore, the variable adjustment unit 22 is set to k=0 when the vehicle is in the first turning state. When the vehicle is in the first turning state, that is, when there is no cant, the sideslip angle β is not affected by the transverse slope. Therefore, k can be 0. Note that when there is no cant, φ=0, so the gφ component is also 0, and β=ωV·G B It will be calculated by the following. 0 corresponds to the base value for the gradient parameter k.

[0050] Furthermore, the variable adjustment unit 22 sets k to a predetermined value other than 0 when the current state is the third turning state. For example, when the current state is the third turning state, the variable adjustment unit 22 sets k to a value less than 0, such as -0.05, -0.10, or -0.15. In another embodiment, when the current state is the third turning state, the variable adjustment unit 22 may set k to a value greater than 0, such as 0.05, 0.08, or 0.10. The value of k when the current state is the third turning state may be determined based on tests / simulations to minimize the error between the estimated value and the true value.

[0051] Furthermore, the variable adjustment unit 22 may set k to a predetermined value other than 0 when the current state is the fourth turning state. Note that the first set value, which is the value of k applied when the state is the third turning state, may be different from the second set value, which is the value of k applied when the state is the fourth turning state. The second set value may also be determined based on tests / simulations to minimize the error between the estimated value and the true value.

[0052] Note that the determination result of the driving scene by the scene determination unit 21 is determined according to the roll angle φ. Therefore, changing the setting of the gradient parameter k according to the determination result of the driving state corresponds to changing the setting of the gradient parameter k according to the roll angle φ. In other embodiments, the variable adjustment unit 22 may be configured to change the gradient parameter k according to the roll angle φ or a combination of the roll angle φ and the vehicle speed V without using the determination result of the driving scene.

[0053] When φ = 0, the variable adjustment unit 22 may set k = 0, and when φ > 0, the gradient parameter k may be changed according to the magnitude relationship between the first multiplication value (ωV) and the second multiplication value (gφ). Specifically, when φ > 0 and ωV < gφ, k may be set to gφ - ωV, and when φ > 0 and ωV ≥ gφ, k may be set to a non-zero predetermined value. Note that when φ > 0 and ωV < gφ, it may be understood as the case where ωV / g < φ. Also, when φ > 0 and ωV ≥ gφ, it may be understood as the case where ωV / g ≥ φ > 0.

[0054] The output value determination unit 24 is configured to determine the value of the lateral slip angle β to be output to other devices such as the anti-lateral-slip device 4. The output value determination unit 24 may be configured to output a predetermined error value when the lateral slip angle β calculated by the calculation unit 23 is greater than or equal to a predetermined upper limit value. The upper limit value may be, for example, 0.3 or 0.4. The error value may be the upper limit value, a value slightly smaller than the upper limit value by a predetermined amount, or a predetermined value representing indeterminacy. When the lateral slip angle β calculated by the calculation unit 23 is less than the upper limit value, that is, when it is within the normal range, the output value determination unit 24 may output the lateral slip angle β calculated by the calculation unit 23. For the sake of convenience, the value of the lateral slip angle β output by the output value determination unit 24 is denoted as the lateral slip angle output value βo.

[0055] According to the above configuration, since the value of the gradient parameter k is dynamically changed according to the driving scene, the possibility that the estimated value of the lateral slip angle β deviates from the true value can be reduced. In other words, the estimation accuracy of the lateral slip angle β can be improved.

[0056] Furthermore, vehicle parameters such as cornering power C can fluctuate after the vehicle leaves the factory. Therefore, in a configuration that estimates the lateral slip angle using precise vehicle parameters, the accuracy of the lateral slip angle estimation may deteriorate over time. This is because the fluctuations in vehicle parameters after factory shipment have a significant impact on the estimation accuracy. To address this issue, the above estimation formula uses normalized vehicle parameters, in other words, approximate vehicle parameters. The above estimation formula does not require precise vehicle parameter values. With the above configuration, the deterioration of the lateral slip angle estimation accuracy due to fluctuations in vehicle parameters can be reduced. As a result, the stability of the lateral slip angle β estimation capability can be improved.

[0057] <Other Embodiments> The lateral slip angle calculation device 10 may be configured to update the value of the cornering power C used in equations 1 and 2 based on the lateral slip angle β calculated by other methods. For example, as shown in Figure 4, the lateral slip angle calculation device 10 may include a second calculation module 30, a third calculation module 40, a VP adjustment unit 50, and a guard value setting unit 60 in addition to the first calculation module 20 and the output value determination unit 24. "VP" in the component names is an abbreviation for Vehicle Parameters. The VP adjustment unit 50 may be referred to as the vehicle parameter adjustment unit.

[0058] The first calculation module 20 is a module that includes the aforementioned scene determination unit 21, variable adjustment unit 22, and calculation unit 23. The first calculation module 20 can be understood as a module that estimates the sideslip angle β using the above equations 1 and 2. Hereinafter, the sideslip angle β calculated by the first calculation module 20 will also be referred to as the first estimated value. The calculation unit 23 included in the first calculation module 20 corresponds to the first calculation unit. The determination result of the scene determination unit 21 may also be provided to the second calculation module 30, the third calculation module 40, the VP adjustment unit 50, and the guard value setting unit 60.

[0059] The second calculation module 30 is a module that estimates the sideslip angle β by multiplying the product of the yaw rate ω and the vehicle speed V, ωV, by an approximation coefficient Kv. The approximation coefficient Kv is the same as the conversion coefficient G mentioned above. B These are different parameters. The approximation coefficient Kv used by the second calculation module 30 is dynamically determined using the calculation results of the third calculation module 40. The second calculation module 30 corresponds to the second calculation unit.

[0060] The third calculation module 40 calculates the differential value dβ of the sideslip angle according to the generally known equation 5 for the derivative of the sideslip angle, and then calculates the sideslip angle β by integrating the said differential value dβ. The third calculation module 40 corresponds to the third calculation unit.

[0061]

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[0062] The subtractor 42 is configured to subtract the yaw rate ω from the output (a / V) of the divider 41. The output (a / V-ω) of the subtractor 42 corresponds to the derivative dβ of the sideslip angle β, as shown in Equation 4. The integrator 43 is configured to calculate the sideslip angle β by integrating the output of the subtractor 42. For convenience, the sideslip angle β calculated by the integrator 43 and thus the third calculation module 40 will also be referred to as the third estimated value β3.

[0063] The third calculation module 40 repeatedly calculates the derivative value dβ and the third estimated value β3 and outputs them to the second calculation module 30 only when the scene determination unit 21 determines that the vehicle is in a turning state. The calculation interval for the derivative value dβ and the sideslip angle β may be several tens of milliseconds.

[0064] The second calculation module 30 identifies the maximum third estimate, which is the maximum value among several third estimates repeatedly calculated by the third calculation module 40 while the vehicle is turning. The second calculation module 30 also repeatedly calculates the product of the vehicle speed V and the yaw rate ω (i.e., the first multiplier) while the vehicle is turning, and obtains the maximum first multiplier, which is the maximum value of the first multiplier during the turn. The second calculation module 30 then adopts the value obtained by dividing the maximum third estimate by the maximum first multiplier as the approximation coefficient Kv. The approximation coefficient Kv is a coefficient that approximates the first multiplier (ωV) to the sideslip angle β. The approximation coefficient Kv can be understood as a (comprehensive) parameter that rounds off various vehicle parameters. The approximation coefficient Kv corresponds to the vehicle parameter (K) in Patent Document 2. A more detailed method for calculating the approximation coefficient Kv may be derived from the method disclosed in Patent Document 2. The contents disclosed in Patent Document 2 and Non-Patent Document 1 may be incorporated into this disclosure by reference.

[0065] Once the second calculation module 30 determines the approximate coefficient Kv, the sideslip angle calculation device 10 repeatedly calculates the second estimated value β2 by multiplying the approximate coefficient Kv, the vehicle speed V, and the yaw rate ω, respectively, while the scene determination unit 21 determines that the vehicle is in a turning state. The second calculation module 30 sequentially outputs the second estimated value β2 to the output value determination unit 24 and the VP adjustment unit 50. In this disclosure, the configuration including the second calculation module 30 and the third calculation module 40 is also referred to as the coefficient automatic adaptation system. The coefficient automatic adaptation system is a system that dynamically calculates and updates the approximate coefficient Kv.

[0066] The VP adjustment unit 50 is a module that changes the set value of the cornering power C used in Equation 2 based on the fact that the difference between the first estimated value β1 and the second estimated value β2 remains constant for a predetermined time. Here, "constant" can be understood as approximately constant. The VP adjustment unit 50 adjusts the cornering power C so that the first estimated value β1 matches the second estimated value β2 when the difference between the first estimated value β1 and the second estimated value β2 remains constant for a predetermined time. The VP adjustment unit 50 is a component of the calculation unit 23. Therefore, the calculation unit 23 may have the same function as the VP adjustment unit 50. In other words, the VP adjustment unit 50 may be inherent in the calculation unit 23 as the first calculation unit.

[0067] Furthermore, the second estimated value β2 may be affected by the detection accuracy of the sensors. In scenarios where the accuracy of the yaw rate sensor 1 and the vehicle speed sensor 2 deteriorates, the second estimated value β2 may contain a relatively large error. Therefore, in such scenarios, the adjustment of cornering power C based on the second estimated value β2 may be discontinued. For example, when the vehicle speed V is unstable (during acceleration or deceleration), the adjustment of cornering power C based on the second estimated value β2 may be discontinued.

[0068] The VP adjustment unit 50 may be configured to adjust the cornering power C based on the second estimated value β2 only when the vehicle behavior satisfies specific update conditions. The update conditions may define scenes in which the values ​​of the yaw rate sensor 1 and the vehicle speed sensor 2 are highly accurate. For example, this may be when both the vehicle speed V and the yaw rate ω are stable within a predetermined range. When the GNSS receiver receives signals from multiple GNSS satellites, the locator can estimate the vehicle speed V and yaw rate ω with high accuracy based on those signals. Therefore, the VP adjustment unit 50 may determine that the update conditions are met when the GNSS receiver receives signals from multiple GNSS satellites.

[0069] The guard value setting unit 60 is configured to change the upper limit of the sideslip angle β that the output value determination unit 24 can output, based on the steering angle θ and the vehicle speed V. The upper limit of the sideslip angle β can be referred to as the guard value. The guard value setting unit 60 increases the upper limit as the vehicle speed V increases. In other words, the guard value setting unit 60 decreases the upper limit as the vehicle speed V decreases. The guard value setting unit 60 may also decrease the upper limit as the steering angle θ decreases. In another embodiment, the guard value setting unit 60 may adjust the upper limit according to the product of the vehicle speed V and the steering angle θ (θV). For example, the guard value setting unit 60 may decrease the upper limit as the product of the vehicle speed V and the steering angle θ decreases. The guard value setting unit 60 may be configured to change not only the upper limit but also the lower limit based on the steering angle θ and the vehicle speed V.

[0070] The output value determination unit 24 basically adopts the first estimated value β1 as the sideslip angle output value βo when the vehicle is in a turning state. However, if the first estimated value β1 reaches the upper limit set by the guard value setting unit 60, the output value determination unit 24 adopts that upper limit as the sideslip angle output value βo.

[0071] The above-described lateral slip angle calculation device 10 corrects the value of the cornering power C used to calculate the first estimated value β1 and the second estimated value β2. This further improves the accuracy of the lateral slip angle β estimation. In addition, the above-described lateral slip angle calculation device 10 adjusts the upper limit of the lateral slip angle β based on the steering angle θ and the vehicle speed V. This reduces the risk of an inappropriate value being output as the lateral slip angle output value βo.

[0072] The sideslip angle output value βo generated by the sideslip angle calculation device 10 may be used for various processes / controls, such as dead reckoning and autonomous driving. Furthermore, the method for calculating the sideslip angle β in the second calculation module 30 is not limited to the method described above. The second calculation module 30 may be a module that estimates the parameters necessary for estimating the sideslip angle using the GNSS Doppler, which is the relative velocity between the GNSS satellite and the GNSS receiver, and determines the sideslip angle. Alternatively, the second calculation module 30 may be configured to estimate the sideslip angle β from the difference between the direction of movement of the vehicle determined by analyzing camera images and the direction of movement determined from the output of the yaw rate sensor 1.

[0073] Furthermore, the scene determination unit 21 does not necessarily have to classify the turning state into the first to fourth turning states for determination. The fourth turning state only occurs when driving on a special road with a large bank. Therefore, the determination of the fourth turning state may be omitted. In other words, the fourth turning state may be integrated into the first turning state.

[0074] The calculation unit 23 calculates a conversion coefficient G according to the vehicle speed V. B The formula defining this can be changed. When the vehicle speed V is small, the first term of formula 2 (LD f / V 2 ) becomes sufficiently larger than the second term (1 / gC). Therefore, when the vehicle speed V is sufficiently small, the second term can be omitted. For example, when the vehicle speed V is less than the threshold Va, the calculation unit 23 calculates the conversion coefficient G determined by the following equation 2a, which is obtained by omitting the second term. B The sideslip angle β may be calculated using the following method. The conversion coefficient G depends on the vehicle speed V. B By changing the definition formula, the processing load of the calculation unit 23 can be reduced. The calculation unit 23 determines the conversion coefficient G, which is determined by the above-mentioned formula 2, when the vehicle speed V is equal to or greater than the threshold Va. B The sideslip angle β is calculated using [this method]. The threshold Va can be set to 18 km / h (5 m / s), 20 km / h (5.5 m / s), 22 km / h (approximately 6 m / s), etc.

number

[0075] <Additional Note> The acquisition of certain data by the lateral slip angle calculation device 10 may include the generation of such data based on signals input from other devices / sensors. The functional arrangement may be changed as appropriate. The lateral slip angle calculation device 10 may be subdivided into multiple devices. Some functions of the lateral slip angle calculation device 10 may be provided by other devices. The devices, systems, and methods described in this disclosure may be implemented by a dedicated computer comprising a processor programmed to execute one or more functions embodied by a computer program. The devices and methods described in this disclosure may be implemented using dedicated hardware logic circuits. The devices and methods described in this disclosure may be implemented by one or more dedicated computers comprising a combination of a processor that executes a computer program and one or more hardware logic circuits. The processor may be any arithmetic core, such as a CPU, MPU, GPU, or DFP (Data Flow Processor). Some or all of the functions of the lateral slip angle calculation device 10 may be implemented as hardware. Some or all of the functions of the lateral slip angle calculation device 10 may be implemented using a system-on-a-chip (SoC), an integrated circuit (IC), or an FPGA. The computer program includes instructions executed by the computer. The computer program may be stored on a computer-readable non-transitory tangible storage medium. The storage medium for the computer program may be a variety of media, such as an HDD (hard-disk drive), an SSD (solid-state drive), or flash memory. [Explanation of symbols]

[0076] 10 Side-slip angle calculation device, 11 Processor, 12 Memory, 13 Storage, 14 Communication interface (communication unit), 21 Scene determination unit, 22 Variable adjustment unit (adjustment unit), 23 Calculation unit, 24 Output value determination unit, 25 Memory unit, 20 First calculation module, 30 Second calculation module (second calculation unit), 40 Third calculation module (third calculation unit), 50 VP adjustment unit

Claims

1. A communication unit (14) acquires the vehicle speed (V), rotational angular velocity (ω), and roll angle (φ) based on the output signals of the on-board sensors, The assumed value of the vehicle's wheelbase (L) and the center of gravity parameter (d) which represents the ratio of the distance from the rear axle to the center of gravity to the assumed value of the wheelbase. ｆ ) and a memory unit (25) that stores normalized cornering power (C) and gravitational acceleration (g), An adjustment unit (22) adjusts the value of a gradient parameter (k), which is a variable for correcting the influence of the transverse gradient of the travel path on the lateral slip angle (β), according to the roll angle (φ), The vehicle speed (V), the rotational angular velocity (ω), the roll angle (φ), the assumed value of the wheelbase (L), and the center of gravity parameter (d) ｆ The system includes a calculation unit (23) that calculates the sideslip angle (β) using the cornering power (C), the gradient parameter (k), and the gravitational acceleration (g), The calculation unit described above, Based on the first multiplicative value, which is the product of the vehicle speed (V) and the rotational angular velocity (ω), the second multiplicative value, which is the product of the roll angle (φ) and the gravitational acceleration (g), and the gradient parameter (k), a first parameter related to the force acting laterally on the vehicle is calculated. The vehicle speed (V), the assumed value of the wheelbase (L), and the center of gravity parameter (d ｆ Based on the gravitational acceleration (g) and the cornering power (C), a second parameter is calculated, which is a coefficient that approximates the first parameter to the sideslip angle. A lateral slip angle calculation device configured to calculate the lateral slip angle by multiplying the first parameter by the second parameter.

2. The lateral slip angle calculation device according to claim 1, wherein the calculation unit is configured to calculate the lateral slip angle (β) using the following formula. [Number 7]

3. The adjustment unit is, If the roll angle is less than a predetermined value, the value of the gradient parameter is set to a predetermined base value. The side-slip angle calculation device according to claim 1, wherein, when the roll angle is greater than or equal to a predetermined value, the value of the gradient parameter is set to a value obtained by subtracting the first multiplicative value, which is the product of the vehicle speed and the rotational angular velocity, from a second multiplicative value, which is the product of the roll angle and the acceleration due to gravity.

4. The adjustment unit is, If the roll angle is less than a predetermined value, the value of the gradient parameter is set to a predetermined base value. If the roll angle is greater than or equal to a predetermined value and the vehicle speed is less than a predetermined value, the gradient parameter is set to a value obtained by subtracting the first multiplicative value, which is the product of the vehicle speed and the rotational angular velocity, from the second multiplicative value, which is the product of the roll angle and the gravitational acceleration. The lateral slip angle calculation device according to claim 1, wherein the device is configured to set the gradient parameter to a predetermined value different from the basic value when the roll angle is greater than or equal to a predetermined value and the vehicle speed is greater than or equal to a predetermined value.

5. The lateral slip angle calculation device according to claim 3 or 4, wherein the aforementioned base value is 0.

6. The side-slip angle calculation device according to claim 3 or 4, wherein the adjustment unit is configured to set the gradient parameter to a value obtained by subtracting the first multiplication value, which is the product of the vehicle speed and the rotational angular velocity, from a second multiplication value, which is the product of the roll angle and the acceleration due to gravity.

7. The skid angle calculation device according to any one of claims 1 to 4, wherein the calculation unit is configured to change the formula for calculating the second parameter according to the vehicle speed (V).

8. In addition to the first calculation unit, which is the calculation unit, The system includes a second calculation unit (30) that calculates the sideslip angle by multiplying the product of the vehicle speed (V) and the rotational angular velocity (ω) by an approximation coefficient (Kv). A side-slip angle calculation device according to any one of claims 1 to 4, wherein the first calculation unit is configured to change the setting value of the cornering power (C) so that the difference between the first estimated value (β1) and the second estimated value (β2) calculated by the second calculation unit becomes smaller, based on the fact that the difference between the first estimated value (β1) and the second estimated value (β2) calculated by the second calculation unit remains constant for a predetermined period of time.

9. The vehicle is further provided with a third calculation unit (40) that calculates the sideslip angle by integrating the differential value of the sideslip angle, which is obtained by subtracting the rotational angular velocity (ω) from the forward angular velocity (a / V) obtained by dividing the lateral acceleration (a) acting on the vehicle by the vehicle speed (V). The second calculation unit is configured to adopt as the approximation coefficient the value obtained by dividing the third estimated value (β3), which is the sideslip angle calculated by the third calculation unit, by the product of the vehicle speed (V) and the rotational angular velocity (ω). The lateral slip angle calculation device according to claim 8, wherein the first calculation unit is configured to change the set value of the cornering power based on the fact that the difference between the first estimated value and the second estimated value remains constant for a predetermined period of time.

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