JP2021187176A - Vehicle state detection device - Google Patents

Abstract

To provide a vehicle state detection device which can detect a spin behavior without requiring a detection value of a steering angle sensor.SOLUTION: A vehicle state detection device 10 acquires information about a vehicle body speed Vx, lateral acceleration Ay and a yaw rate Yr of a vehicle from a sensor mounted on the vehicle. The vehicle state detection device calculates an actual lateral speed differential value dVy indicating an actual lateral speed differential value of the vehicle and a standard lateral speed differential value dVyStd indicating a lateral speed differential value of a vehicle becoming the standard from the acquired information about the vehicle body speed Vx, lateral acceleration Ay and raw rate Yr. The vehicle state detection device determines that the vehicle performs a spin behavior when a difference dVyError obtained by subtracting the standard lateral speed differential value dVyStd from the actual lateral speed differential value dVy exceeds a prescribed threshold.SELECTED DRAWING: Figure 3

Description

The present invention relates to a vehicle state detection device that detects the state of a vehicle.

Patent Document 1 discloses a technique relating to a turning state estimation device that estimates whether a vehicle is oversteer or understeer with high accuracy. This turning state estimation device calculates the normative side slip angular velocity (hereinafter, also referred to as "normative side slip angular velocity") based on the vehicle speed and steering angle of the vehicle, and calculates the normative skid angle speed from the absolute value of the actual vehicle side slip angular velocity. If the difference obtained by subtracting the absolute value of the angular velocity exceeds a predetermined positive threshold, it is estimated to be oversteer, and if it is below a predetermined negative threshold, it is estimated to be understeer.

Japanese Unexamined Patent Publication No. 2008-0875448

To detect the oversteer or understeer state of the vehicle or the unstable state of the vehicle such as the spin behavior of the vehicle with high accuracy is a vehicle using a device represented by an electronic stability control (ESC). It is necessary to properly control the behavior stabilization during turning. Such detection is generally performed based on a value calculated from vehicle state information such as vehicle speed and acceleration detected by a sensor mounted on the vehicle.

In the above-mentioned technique, in order to calculate the standard side slip angular velocity, a vehicle speed sensor for detecting the speed of the vehicle and a steering angle sensor for detecting the steering angle of the steering are required. However, when excessive steering that may cause spin behavior (for example, when steering 270 deg while traveling straight at 80 kph in the ESC test of Federal Motor Vehicle Safety Standards (FMVSS)), the steering angle sensor The detected value of is calculated as an excessive standard side slip angle velocity, and there is a possibility that the detection of the spin behavior is delayed or inaccurate, and is not performed properly. In addition, if the rudder angle sensor fails, the device cannot detect it or it becomes inaccurate.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a vehicle state detection device capable of detecting spin behavior without requiring a detection value of a steering angle sensor.

The present invention relates to a vehicle condition detection device.
The vehicle condition detector is
It includes a processor and a memory that stores information on the vehicle body speed, lateral acceleration, and yaw rate detected by sensors mounted on the vehicle.

The processor uses the actual lateral speed differential value calculation process that calculates the actual lateral speed differential value indicating the actual lateral speed differential value of the vehicle from the vehicle body speed, lateral acceleration and yaw rate, and the vehicle that becomes the standard from the vehicle body speed, lateral acceleration and yaw rate. When the difference between the normative lateral velocity differential value calculation process for calculating the normative lateral velocity differential value and the difference obtained by subtracting the normative lateral velocity differential value from the actual lateral velocity differential value exceeds a predetermined threshold, the vehicle Is configured to perform spin behavior determination processing for determining that is performing spin behavior.

The lateral speed differential value of the vehicle is one value indicating the degree of turning when the vehicle makes a turning motion, and is defined as the actual lateral speed differential value of the vehicle (hereinafter, also referred to as "actual lateral speed differential value"). It is possible to determine whether or not the vehicle is performing spin behavior by evaluating the deviation of the lateral velocity differential value (hereinafter, also referred to as "normative lateral velocity differential value") of the vehicle. The present inventor has found that the normative lateral velocity derivative value obtained by using a linear two-wheel model which is a mathematical model of a vehicle can be calculated from the vehicle body speed, the lateral acceleration and the yaw rate regardless of the steering angle.

According to the present invention, whether or not the spin behavior is performed by evaluating the difference obtained by subtracting the normative lateral velocity differential value calculated from the vehicle body speed, the lateral acceleration and the yaw rate from the actual lateral velocity differential value of the vehicle. Is determined. This makes it possible to detect the spin behavior without the need for the detection value of the steering angle sensor, which is expected to improve safety.

It is a figure which shows typically the mathematical model of the vehicle which concerns on embodiment. It is a block diagram which shows the structural example of the vehicle state detection apparatus which concerns on embodiment. It is a figure which shows typically the process executed by the vehicle state detection apparatus which concerns on embodiment. It is a figure which shows the process executed by the real lateral velocity differential value calculation process. It is a figure which shows the process which is executed by the norm lateral velocity differential value calculation process. It is a flowchart which shows the process related to the spin behavior determination process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1. 1. Overview 1-1. Mathematical Model of Vehicle FIG. 1 is a diagram schematically showing a mathematical model of vehicle 1 according to an embodiment of the present invention. The vehicle 1 is turning left with the turning center C as the center along the turning track 2. In this embodiment, the vehicle 1 is modeled by a linear two-wheel model. The linear two-wheel model considers the vehicle 1 as one rigid body, considers only the plane motion in the yaw rotation direction and the lateral direction, and the left and right tire characteristics of the front and rear wheels are equal, and the front and rear wheels are one tire each. It is a mathematical model of the vehicle 1 linearized by reducing the degree of freedom of motion by assuming that it is represented by.

The respective values of the vehicle 1 shown in FIG. 1 will be described. V is the speed of the vehicle 1 (hereinafter, also referred to as “vehicle speed V”). Vx is a speed component of the vehicle speed V in the front-rear direction of the vehicle body axis (hereinafter, also referred to as “vehicle speed Vx”). Vy is a speed component of the vehicle speed V in the left-right direction of the vehicle body axis (hereinafter, also referred to as “lateral speed Vy”). Yr is a yaw rate with the center of gravity G of the vehicle 1 as the rotation axis. L is the distance (wheelbase) between the front wheel axle a1 and the rear wheel axle a2 of the vehicle 1. Lf is the distance between the front wheel axle a1 and the center of gravity axis a3 of the vehicle 1. Lr is the distance between the rear wheel axle a2 of the vehicle 1 and the center of gravity axis a3. β is the side slip angle of the vehicle 1. δ is the steering angle of the vehicle 1. Ff is a cornering force generated by the front tires. Fr is a cornering force generated by the tires of the rear wheels. Ay is a component of the acceleration of the vehicle 1 in the left-right direction of the vehicle body axis (hereinafter, also referred to as “lateral acceleration Ay”). The lateral acceleration Ay is the acceleration in the left-right direction of the vehicle body axis of the vehicle 1 detected by the acceleration sensor mounted on the vehicle 1.

The equation of motion of the vehicle 1 in the linear two-wheel model can be expressed by the following equations of motion of translational motion (1a) and equations of motion of rotational motion (2a).

Here, m is the vehicle mass, dVy is the time derivative of the lateral velocity Vy (hereinafter, also referred to as “lateral velocity differential value dVy”), I is the yaw moment of inertia around the center of gravity G, and dYr is the time derivative of the yaw rate Yr. , Represent each. Further, from the equation (1a), the lateral acceleration Ay becomes the following equation (3a).

The vehicle body speed Vx is positive in the front direction of the vehicle body axis. The cornering force Ff, the cornering force Fr, the lateral speed Vy, and the lateral acceleration Ay are positive in the left direction of the vehicle body axis, respectively. The yaw rate Yr, the side slip angle β, and the steering angle δ are positive in the clockwise direction, respectively. Therefore, in the case of left turn shown in FIG. 1, the vehicle body speed Vx is a positive value, the cornering force Ff and Fr are positive values, the lateral speed Vy and the lateral slip angle β are negative values, the yaw rate Yr, the lateral acceleration Ay and the steering angle δ are positive values. The value is.

When the side slip angle β is sufficiently small, the following approximate equations (4) and (5) can be given. At this time, the cornering forces Ff and Fr can be given by the following equations (6) and (7).

Here, dβ represents the time derivative value of the side slip angle β (hereinafter, also referred to as “side slip angular velocity dβ”), and Kf and Kr represent the proportional coefficients (cornering power) of the cornering force Ff and Fr determined by the characteristics of the vehicle 1, respectively. ing.

From the equation (5), the equation (3a) of the lateral acceleration Ay can also be expressed by the following equation (3b).

From the formulas (5) to (7), the formulas (1a) and (2a) are represented by the following formulas (1b) and (2b). Equations (1b) and (2b) are equations of motion represented by the mathematical model of the vehicle 1 according to the present embodiment.

1-2. Judgment of spin behavior When the vehicle 1 is performing a steady turning motion, the side slip angle β is stable and the turning motion is performed at a constant yaw rate Yr. On the other hand, the spin behavior is a state in which the side slip angle β of the vehicle 1 is not stable due to excessive steering, sudden turning, or the like, and an excessive yaw rate Yr is generated with respect to the turning motion. Spin behavior generally occurs when the vehicle is oversteered.

As described above, when the vehicle 1 is performing the spin behavior, the side slip angle β is not stable. Therefore, the spin behavior of the vehicle 1 can be determined by evaluating the magnitude of the side slip angular velocity dβ.

By the way, as shown in FIG. 1, when the absolute value of the lateral slip angle β becomes large, the absolute value of the lateral velocity Vy also becomes large. That is, the lateral slip angular velocity dβ correlates with the lateral velocity differential value dVy. Therefore, the spin behavior of the vehicle can also be determined by evaluating the magnitude of the lateral velocity differential value dVy.

As shown in FIG. 1, when the spin behavior occurs in the oversteer state during the left turn, the lateral velocity differential value dVy is negative. On the other hand, when the spin behavior occurs in the oversteer state during a right turn, the lateral velocity differential value dVy is positive. It can be said that the larger the absolute value of the lateral velocity differential value dVy is, the larger the absolute value of the lateral slip angular velocity dβ is, and the more excessive spin behavior is performed.

The vehicle state detection device according to the present embodiment determines the spin behavior of the vehicle 1 by evaluating the lateral velocity differential value dVy.

2. 2. Configuration FIG. 2 is a block diagram showing a configuration example of the vehicle state detection device 10 according to the embodiment of the present invention. The vehicle state detection device 10 is typically an ECU (Electronic Control Unit) mounted on the vehicle 1. The vehicle state detection device 10 may be a combination of a plurality of ECUs. Alternatively, the vehicle state detection device 10 may be an information processing device external to the vehicle 1.

The vehicle state detection device 10 is electrically or wirelessly connected to the sensor group 20 and the actuator group 30.

The processing circuit of the vehicle state detection device 10 includes an interface 11, a memory 12, and a processor 13. The interface 11 inputs the detection values of various sensors mounted on the vehicle 1 and outputs operation signals for various actuators included in the vehicle 1. The input detection values of the various sensors are stored in the memory 12. The memory 12 includes a RAM (Random Access Memory) for temporarily recording data and a ROM (Read Only Memory) for storing a control program, constant values of the control program, and the like. The processor 13 reads a control program or the like from the memory 12 and executes it, and generates an operation signal based on the captured input value.

The sensor group 20 includes a vehicle speed sensor 21, a lateral acceleration sensor 22, and a yaw rate sensor 23. The vehicle speed sensor 21 detects and outputs the vehicle body speed Vx. The vehicle speed sensor 21 is typically a wheel speed sensor. The lateral acceleration sensor 22 detects and outputs the lateral acceleration Ay. The lateral acceleration sensor 22 is typically a G sensor. The yaw rate sensor 23 detects and outputs the yaw rate Yr. The yaw rate sensor 23 is typically a gyro sensor.

The actuator group 30 includes a moment control actuator 31. The moment control actuator 31 generates a yaw moment in the vehicle 1 based on the input target moment. As a result, the movement of the vehicle 1 in the yaw direction can be controlled according to the state of the vehicle 1 and the behavior of the vehicle 1 is stabilized.

The vehicle state detection device 10 according to the embodiment of the present invention outputs a spin behavior determination value and a target moment to the actuator group 30 as described later. The moment control actuator 31 generates a yaw moment based on the target moment when the vehicle 1 is in a spin behavior. As a result, the spin behavior of the vehicle 1 can be suppressed.

The vehicle state detection device 10 acquires at least information on the vehicle body speed Vx, lateral acceleration Ay, and yaw rate Yr from the sensor group 20, and outputs at least the spin behavior determination value and the target moment to the actuator group 30. The spin behavior determination value is a value indicating whether or not the vehicle 1 is performing spin behavior. The spin behavior determination value is, for example, a Boolean value set to 0 when the vehicle 1 does not have a spin behavior and 1 when it is determined that the vehicle 1 has a spin behavior. As described above, the target moment is the target value of the yaw moment for suppressing the spin behavior.

3. 3. Functions of the Vehicle Condition Detection Device FIG. 3 is a diagram schematically showing a process executed by the processor 13 of the vehicle state detection device 10. The processes executed by the processor 13 of the vehicle state detection device 10 include the actual lateral velocity differential value calculation process S10, the normative lateral velocity differential value calculation process S20, the spin behavior determination process S30, and the target moment calculation process S40. Includes.

In the actual lateral velocity differential value calculation process S10, the processor 13 calculates the actual lateral velocity differential value dVy (actual lateral velocity differential value dVy) of the vehicle 1. In the normative lateral velocity differential value calculation process S20, the processor 13 calculates the normative lateral velocity differential value dVyStd of the vehicle 1. The normative lateral velocity differential value dVyStd is a normative lateral velocity differential value dVy, and is calculated from the vehicle body speed Vx, the lateral acceleration Ay, and the yaw rate Yr using a linear two-wheel model, as will be described later. After the actual lateral velocity differential value calculation process S10 and the standard lateral velocity differential value calculation process S20, the processor 13 calculates the difference dVyError obtained by subtracting the nominal lateral velocity differential value dVyStd from the actual lateral velocity differential value dVy. In the spin behavior determination process S30, the processor 13 determines whether or not the vehicle 1 is performing the spin behavior based on the difference dVyError, and outputs the spin behavior determination value. In the target moment calculation process S40, the processor 13 calculates and outputs a target moment for suppressing the spin behavior based on the difference dVyError.

3-1. From the actual lateral velocity differential value calculation processing equation (3a), the actual lateral velocity differential value dVy can be calculated by the following equation (8). It can be seen that the actual lateral velocity differential value dVy can be calculated from the vehicle body velocity Vx, the lateral acceleration Ay, and the yaw rate Yr. FIG. 4 shows the process of the actual lateral velocity differential value calculation process S10.

3-2. Normative lateral velocity differential value calculation process The normative lateral velocity differential value dVyStd calculated by the linear two-wheel model will be described below. From the equations (1b) and (2b), the transfer function G _δ ^β _{(s) of the side slip angle β with respect to the steering angle δ and the transfer function G δ} ^r (s) of the yaw rate Yr with respect to the steering angle δ are obtained by the following equations (s), respectively. It can be expressed by 9) and the equation (10).

Here, s is a complex number and is a variable of the function by Laplace transform. β (s), Yr (s) and δ (s) are image functions obtained by Laplace transform of the side slip angle β, the yaw rate Yr and the steering angle δ, respectively. G _δ ^β (0) and G _δ ^r (0) are the transfer function of the side slip angle β with respect to the steering angle δ and the transfer function of the yaw rate Yr with respect to the steering angle δ in the steady state, respectively. It is represented by 12). ω _n and ζ are natural frequencies and attenuation factors in the mathematical model of vehicle 1, respectively. T _β and _Tr are the time constants of the linear advancing elements of the transfer function G _δ ^β (s) and the transfer function G _δ ^r (s), respectively, and are represented by the following equations (13) and (14). .. Kh is a stability factor of the vehicle 1 and is expressed by the following equation (15).

From the equations (3b), (9) and (10), the transfer function G _δ ^y (s) of the lateral acceleration Ay with respect to the steering angle δ is expressed by the following equation (16). Hy (s) and G (s) are the following equations (17) and (18).

On the other hand, the following equation (19) can be given from the equation (3b). dβ (s) is an image function by Laplace transform of the lateral slip angular velocity dβ.

From the formula (10), the formula (16) and the formula (19), the following formula (20) can be given.

Vx · dβ in the equation (20) means the lateral velocity differential value dVy as shown in the equation (5). Using the equation (20), the normative lateral velocity differential value calculation process S20 calculates and outputs the normative lateral velocity differential value dVyStd. It can be seen that the normative lateral velocity differential value dVyStd can be calculated by the vehicle body speed Vx, the lateral acceleration Ay and the yaw rate Yr without using the steering angle δ as shown in the equation (20). FIG. 5 shows the process of the normative lateral velocity differential value calculation process S20.

3-3. Spin behavior determination process FIG. 6 is a flowchart showing a process related to the spin behavior determination process S30. The processing flow shown in FIG. 6 is repeatedly executed at regular intervals.

In step S31, the processor 13 determines whether the vehicle 1 is turning left or turning right. Whether it is turning left or turning right can be determined, for example, by the sign of the lateral acceleration Ay detected by the lateral acceleration sensor 22. Alternatively, it may be a code of the yaw rate Yr detected by the yaw rate sensor 23. As described above, when turning left, the lateral acceleration Ay and the yaw rate Yr become positive values, and when turning right, the lateral acceleration Ay and the yaw rate Yr become negative values. If it is determined that the vehicle is turning left (step S31; Yes), the process proceeds to step S32. If it is determined that the vehicle is turning to the right (step S31; No), the process proceeds to step S33.

In step S32, the processor 13 determines whether or not the vehicle 1 is spinning while turning left. During the spin behavior during left turn, the lateral velocity differential value dVy becomes a negative value as described above. Therefore, when the difference dVyError becomes smaller than the negative number of the predetermined threshold value dVyTh, the processor 13 determines that the vehicle 1 is in the spin behavior. If it is determined that the vehicle 1 is spinning (step S32; Yes), the process proceeds to step S34. If it is determined that the vehicle 1 is not spinning (step S32; No), the process proceeds to step S36.

In step S33, the processor 13 determines whether or not the vehicle 1 is spinning during a right turn. During the spin behavior during a right turn, the lateral velocity differential value dVy becomes a positive value as described above. Therefore, when the difference dVyError becomes larger than the positive number of the predetermined threshold value dVyTh, the processor 13 determines that the vehicle 1 is in the spin behavior. When it is determined that the vehicle 1 is performing the spin behavior (step S33; Yes), the process proceeds to step S35. If it is determined that the vehicle 1 is not performing the spin behavior (step S33; No), the process proceeds to step S36.

The threshold value dVyTh is an intervention threshold value for spin behavior suppression control, and is a value determined by, for example, adapting to an actual vehicle. Further, the threshold value dVyTh in step S32 and the threshold value dVyTh in step S33 may be set to be different values.

In addition, "the difference dVyError exceeds the threshold value dVyThh" means "the difference dVyError becomes smaller than the negative number of the threshold value dVyThh during the left turn" and "the difference dVyError becomes larger than the positive number of the threshold value dVyThh during the right turn". That means both.

Step S34 and step S35 represent substantially the same processing. In step S34 and step S35, the processor 13 sets the spin behavior determination value to 1. After that, the process ends.

In step S36, the processor 13 sets the spin behavior determination value to 0. After that, the process ends.

3-4. Target moment calculation process The target moment calculation process S40 outputs a target moment by using, for example, a two-dimensional map that gives a target moment to the difference dVyError. The two-dimensional map can be created so as to give an appropriate target moment to the difference dVyError by, for example, adapting to the actual vehicle.

4. Effect As described above, according to the vehicle state detection device 10 of the present embodiment, whether or not the spin behavior is performed without requiring the detection value of the steering angle sensor by using the lateral velocity differential value dVy. Can be determined. As a result, the spin behavior can be determined even when excessive steering is performed or the steering angle sensor fails.

By the way, in the formula (20), 1 / Hy (s) and 1 / Hr (s) are low-pass filters. Therefore, the normative lateral velocity differential value dVyStd includes the high frequency components of the lateral acceleration Ay and the yaw rate Yr, and includes the sensor noise of the lateral acceleration sensor 22 and the yaw rate sensor 23. Therefore, the sensor noise is removed in the calculation of the difference dVyError. As described above, the vehicle state detection device 10 of the present embodiment has a noise canceling effect as a secondary effect. As a result, unnecessary output due to sensor noise of the lateral acceleration sensor 22 and the yaw rate sensor 23 due to road surface disturbance can be reduced, and robustness is improved. In addition, the intervention threshold dVyTh for spin suppression control can be set small.

5. Modification example of the vehicle state detection device of the embodiment The vehicle state detection device 10 of the embodiment may adopt the modified mode as follows.

The vehicle state detection device 10 may be configured to correct the cant angle of the road surface (hereinafter, also referred to as “cant correction”) for the detected value of the lateral acceleration sensor 22. When the vehicle 1 turns on a road surface having a cant angle, the G sensor, which is a typical lateral acceleration sensor 22, is affected by the gravitational acceleration due to the cant angle of the road surface. Therefore, the detected value of the G sensor may have a non-negligible deviation with respect to the lateral acceleration Ay. The vehicle state detection device 10 corrects this deviation. The cant correction is performed by estimating the cant angle using, for example, a roll rate sensor. The roll rate sensor is generally included in the gyro sensor. The sensor group 20 may further include a roll rate sensor. When the roll rate sensor is not mounted, the cant correction may be performed by estimating the cant angle using the low frequency component of the detected value of the G sensor.

1 Vehicle 10 Vehicle state detection device 11 Interface 12 Memory 13 Processor 20 Sensor group 21 Vehicle speed sensor 22 Lateral acceleration sensor 23 Yaw rate sensor 30 Actuator group 31 Moment control actuator S10 Actual lateral speed differential value calculation processing S20 Normal lateral speed differential value calculation processing S30 Spin behavior determination process S40 Target moment calculation process

Claims (1)

It is a vehicle condition detection device that detects the condition of the vehicle.
With the processor
A memory that stores information on the vehicle body speed, lateral acceleration, and yaw rate detected by the sensor mounted on the vehicle, and
Equipped with
The processor
The actual lateral speed differential value calculation process for calculating the actual lateral speed differential value indicating the actual lateral speed differential value of the vehicle from the vehicle body speed, the lateral acceleration, and the yaw rate, and
A normative lateral velocity differential value calculation process for calculating a normative lateral velocity differential value indicating the lateral velocity differential value of the vehicle as a norm from the vehicle body speed, the lateral acceleration, and the yaw rate.
When the difference obtained by subtracting the normative lateral velocity differential value from the actual lateral velocity differential value exceeds a predetermined threshold value, the spin behavior determination process for determining that the vehicle is performing spin behavior is performed. A vehicle condition detection device characterized by being

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