JPH10282138A - Slip angular velocity correcting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct the error of a sensor which detects the moving state of a vehicle caused by an offset when the offset occurs in the sensor. SOLUTION: The slip angular velocity β(.)+Δβ(.) of a vehicle is calculated from the lateral acceleration y(..), yaw rate θ(.), and car speed V of the vehicle (100). On the other hand, the estimated value βh of the slip angle of the vehicle is found from the steering angle δf, car speed V, and a prestored vehicle model (102) and the estimated value βh (.) of the slip angular velocity is calculated by differentiating the estimated value βh (106). Then an offset error Δβ(.) is obtained by eliminating a modeling error by removing s high-frequency component from the deviation Δβg (.) between the calculated and estimated values of the slip angular velocity (108). Finally, a slip angular velocity containing no offset error is obtained by subtracting the offset error Δβ(.) from the slip angular velocity β(.)+Δβ(.) (110).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for calculating a slip angular velocity of a vehicle based on an output of a sensor provided in the vehicle.

[0002]

2. Description of the Related Art In recent years, devices and systems that supplement a driver's steering operation and brake operation to realize stable running of a vehicle have been put to practical use. For example, an antilock brake system (ABS), a four-wheel steering system (4WS), a vehicle stability control system, and the like correspond to this. In such a system, it is necessary to accurately grasp the current behavior of the vehicle and accurately control each device in response to this behavior.

[0003] One of the behaviors of the vehicle is a slip angle. The slip angle is a yaw rate which is an angular velocity of the vehicle around the center of gravity of the vehicle, a lateral acceleration (hereinafter referred to as a lateral acceleration), and a vehicle speed. It is required based on. The yaw rate sensor for detecting the yaw rate and the lateral acceleration sensor for detecting the lateral acceleration detect the yaw rate and the lateral acceleration at that time based on a relative value with respect to a certain reference value. Normally, the reference values are both yaw rate and lateral acceleration.
This is when the value is 0. Therefore, when the reference value deviates, the output of the yaw rate sensor and the lateral acceleration sensor output a value offset by the deviation. Therefore, the slip angle calculated based on this offset value differs from the actual value.

Japanese Patent Publication No. 7-58295 discloses a method of detecting an offset value based on the output of a yaw rate sensor while the vehicle is stopped.

[0005]

According to the method described in the above publication, the offset value can be detected only when the vehicle is stopped. Therefore, the offset generated in the sensor cannot be corrected during long-time continuous running such as running on a highway. Also, on highways, etc., cants are provided at the curves,
This causes an offset in the sensor (particularly the lateral acceleration sensor), but this offset cannot be corrected by the method described in the above-mentioned publication. As a result,
The slip angular velocity calculated based on the offset value causes an error. Then, based on the slip angular velocity including the error, the ABS, the 4WS, the vehicle stability control system, and the like are operated, and when the vehicle behavior is controlled, a deviation from the vehicle behavior felt by the driver occurs, and the driver feels discomfort. There was a problem that sometimes.

The present invention has been made to solve the above-described problem, and has as its object to provide a slip angular velocity correction device that corrects a slip angular velocity in consideration of an offset generated in a sensor.

[0007]

In order to solve the above-mentioned problems, a slip angular velocity correcting device according to the present invention comprises a slip angular velocity calculating means for calculating a slip angular velocity based on an output of at least one sensor provided in a vehicle. And a model storage means for storing a model relating to the vehicle behavior, and a slip based on an output of at least one sensor and the model, the output including at least one sensor other than the sensor used for calculating the slip angular velocity provided in the vehicle. The vehicle has a slip angular velocity estimating means for estimating an angular velocity, and a slip angular velocity correcting means for correcting the slip angular velocity based on the calculated slip angular velocity and the estimated slip angular velocity.

Further, the slip angular velocity correcting means subtracts an estimated slip angular velocity from the calculated slip angular velocity, and eliminates an error caused by modeling from the value obtained by the subtraction. Modeling error elimination means, and second subtraction means for subtracting the value from which the modeling error has been eliminated from the calculated slip angular velocity to calculate a corrected slip angular velocity. .

A slip angular velocity correcting method according to another aspect of the present invention calculates a slip angular velocity based on an output of at least one sensor provided in the vehicle, and stores a vehicle behavior model stored in advance and a vehicle behavior model stored in advance. Is provided, including at least one sensor other than the sensor used when calculating the slip angular velocity, the slip angular velocity is estimated based on the output of at least one sensor, the calculation using the estimated slip angular velocity The corrected slip angular velocity is corrected.

Further, the slip angular velocity is corrected by calculating a deviation between the calculated slip angular velocity and the estimated value, excluding a modeling error from the deviation, and subtracting the deviation excluding the modeling error from the calculated slip angular velocity. You can do it.

Furthermore, the elimination of the modeling error is as follows:
This can be performed by removing the high frequency component of the deviation.

In the present invention, the calculation of the slip angular velocity of the vehicle preferably includes a vehicle speed sensor for detecting a vehicle speed, a yaw rate sensor for detecting a rotational angular speed around the center of gravity of the vehicle,
It is calculated based on the output of each of the lateral acceleration sensors that detect the lateral acceleration of the vehicle. On the other hand, the slip angular velocity is preferably estimated by calculating the slip angle estimated based on the vehicle model based on the characteristics of the vehicle measured in advance, the output of the vehicle speed sensor, and the output of the steering angle sensor that detects the steering angle of the front wheels. This is done by differentiating. If there is no error in the output of the sensor and the vehicle model accurately represents the characteristics of the actual vehicle, the calculated value of the slip angular velocity matches the estimated value. However, the lateral acceleration sensor and the yaw rate sensor do not calculate the absolute values of the lateral acceleration and the yaw rate, but output the detected values as relative values from a known reference value. Usually, the reference value is
The reference value is set in a state where the vehicle is stopped and neither the lateral acceleration nor the yaw rate is generated, in this case, 0. If the position of the zero point shifts, an error is included in the calculated value of the slip angular velocity. At this time, if an error is not included in the estimated value of the slip angular velocity, the difference between the calculated value and the estimated value is the error. However, since the estimated value also includes an error due to modeling, the error between the calculated value and the estimated value also includes an error due to modeling. Error due to deviation of sensor reference point (offset error)
Appear constantly, while errors due to modeling (modeling errors) relatively fluctuate. In other words, in each sampling period, the offset error is considered to be the same value every time, while the modeling error is considered to be a different value. Therefore, by passing the difference output between the calculated value of the slip angular velocity and the estimated value through a low-pass filter, the modeling error which is a fluctuation component can be eliminated, and only the offset error can be extracted.

By subtracting the extracted offset error from the calculated slip angular velocity, it becomes possible to correct the slip angular velocity offset error.

[0014]

Embodiments of the present invention (hereinafter, referred to as embodiments) will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a vehicle according to the present embodiment. This vehicle includes a vehicle body 10, two front wheels 12 disposed on the left and right of a front part of the vehicle body, and two rear wheels 14 disposed on the left and right of a rear part. The distance (wheel base) between the axle of the front wheel 12 and the axle of the rear wheel 14 is L. Front wheel 12
Is mechanically coupled to a steering wheel 16 operated by the driver, and a steering angle δf reduced by a gear ratio is given to the rotation angle of the steering wheel 16.

The front and rear wheels 12 and 14 are provided with a braking force in accordance with the operation of a brake pedal (not shown) by the driver. It can be controlled. The operation of the brake pedal is transmitted by a hydraulic pressure to a braking force generator 22 provided on the front and rear wheels 12, 14, where a braking force corresponding to the pedal operation amount is generated. The braking force generation unit 22 includes a brake pad that is specifically controlled by a hydraulic cylinder to advance and retreat, and a brake disk that rotates together with the front and rear wheels 12 and 14. Then, the brake pad is pressed against the brake disk by the hydraulic pressure generated by operating the brake pedal, and a braking force is generated by friction. Especially,
In the control of the braking force by the vehicle behavior control unit 18, the hydraulic pressure generated by the operation of the brake pedal is controlled by a hydraulic control unit that increases or decreases the hydraulic pressure.
Also, in this case, it is possible to apply a different braking force to each of the four wheels, so that when the behavior of the vehicle indicates an excessive oversteer or an excessive understeer state, a moment for canceling the steer state is provided. Can be generated. This is known as a vehicle stability control system (VSC®).

Further, the vehicle according to the present embodiment has a steering angle sensor 24, a vehicle speed sensor 26 for detecting the behavior of the vehicle,
A lateral acceleration sensor 28 and a yaw rate sensor 30 are provided. The steering angle sensor 24 detects a steering angle δf of the front wheels 12 based on the rotation angle of the steering 16. The vehicle speed sensor 26 preferably includes an acceleration sensor and a calculation unit that performs a predetermined calculation on the output of the acceleration sensor.
Is detected. The lateral acceleration sensor 28 detects the lateral acceleration y (‥) of the vehicle. The symbol (‥) represents the second derivative with respect to time, and for example, if y (‥), it represents the second derivative of the left-right coordinate y. Further, in the mathematical expressions described hereinafter, the symbol (‥) is represented by describing two dots above the character representing the variable. The lateral acceleration sensor 28 is preferably provided at the position of the center of gravity of the vehicle, but if this is not possible, the lateral acceleration sensor 28 is provided based on the distance from the position of the center of gravity to the installation position of the sensor 28 and the yaw rate θ (•) described later. The output of the acceleration sensor 28 is corrected, and the lateral acceleration y at the position of the center of gravity of the vehicle is calculated.
(‥) is calculated. The yaw rate sensor 30 is constituted by a gyro sensor and has an angular acceleration θ around the center of gravity of the vehicle.
(‥) is detected, and based on this, the angular velocity θ (·) around the center of gravity of the vehicle is calculated. The symbol (•) represents the first derivative with respect to time. For example, if θ (•), the rotation angle θ
Represents the first order differential value of. Further, in the mathematical expressions described below, a symbol (•) is represented by describing one dot above a character representing a variable.

The side slip angle β shown in FIG.
The angle between the longitudinal axis of 0 and the speed V of the vehicle is defined. When the vehicle is traveling at an extremely low speed, the steering angle δf and the sideslip angle β coincide when the rear wheel steering is not performed. I do. However, when the vehicle speed increases, the sideslip angle β does not match the steering angle δf, and the slip angle β cannot be immediately calculated from the steering angle δf.

FIG. 2 is a block diagram showing a method of correcting a slip angular velocity according to the present embodiment. Slip angular velocity β (・)
Is calculated from the lateral acceleration y (‥), the yaw rate θ (·) and the vehicle speed V.

(Equation 1) Can be calculated based on However, for example, on a road surface with a cant, that is, a road surface inclined in a direction perpendicular to the traveling direction, even when the vehicle is stopped, a lateral acceleration is detected by gravity, and a so-called offset error occurs. When traveling on such a road surface,
The lateral acceleration sensor 28 provided in the vehicle detects not the lateral acceleration in the horizontal plane but the lateral acceleration in a plane parallel to the road surface. Therefore, the detected lateral acceleration includes an error.

Assuming that the error of the lateral acceleration is Δy (‥) and the true value of the lateral acceleration is y (‥), equation (1) becomes

(Equation 2) Becomes In Expression (2), Δβ (·) is an error in the lateral slip angular velocity caused by the error included in the detected value of the lateral acceleration. The calculation of the slip angular velocity is performed based on the above equation (2) (100).

On the other hand, the estimation of the sideslip angular velocity by the vehicle model is performed as follows. The slip angle estimated value β _h by the vehicle model is

(Equation 3) (102). In the equation (3), T is a time constant, which is substantially the same as the vehicle time constant for steering.
And B are coefficients determined by vehicle constants such as cornering power and vehicle weight, and s is a Laplace operator.

The estimated slip angular velocity β _h (·) is

(Equation 4) (104). In equation (4), k indicates the current sampling point, and Δt is the sampling period.

Next, the slip angular velocity estimated value β _h (·) estimated from the vehicle model is subtracted from the slip angular velocity β (·) + Δβ (·) including the error calculated by the equation (2) (1).
06), and calculate the slip angular velocity deviation Δβ _g (·). The slip angular velocity deviation Δβ _g (·) is generated due to an offset error included in the lateral acceleration and an error due to modeling. Although the offset error does not cause a large variation due to its nature, the error due to modeling varies relatively sharply because it occurs separately in each sampling period. Therefore, the offset angular error Δβ (•) can be calculated by removing the high frequency of the slip angular velocity deviation Δβ _g (•) from a predetermined frequency or more to eliminate the error due to modeling (108). In order to eliminate errors due to modeling, a low-pass filter having a low cutoff frequency can be used.

This offset error Δβ (·) is calculated by the following equation (2).
When subtracted from the slip angular velocity β (•) + Δβ (•) calculated in the above equation, the slip angular velocity β with the offset error corrected
(•) can be obtained (110).

In the above description, the case where an offset error has occurred in the lateral acceleration has been described.
Even if the cause of the occurrence of Δβ (•) is another sensor, and in this embodiment, an offset error occurs in the yaw rate sensor, the correction can be similarly performed. The same applies when an offset error occurs in both the lateral acceleration and the yaw rate.

FIGS. 3 to 6 show simulation results when the steering angle is ± 60 deg, the steering frequency is 0.2 Hz, the offset amount of the lateral acceleration sensor is 0.5 m / s ² , and the cutoff frequency of the low-pass filter is 0.5 Hz. It is shown.

In the simulation, it is assumed that an offset of the lateral acceleration sensor occurs stepwise while a steering input is given in a sine wave shape, and the estimation result of the slip angle β at this time is examined. The slip angle β is the slip angular velocity β calculated by the method described in the present embodiment.
(・)

(Equation 5) Estimated by The result is shown in FIG.
As shown in FIG. 3, the estimated slip angle when the offset error is corrected is closer to the true value than in the case where the offset error is not corrected, and is within the range required by the vehicle stability control system shown in the figure. Therefore, control can be performed without giving the driver an unnatural feeling.

FIG. 4 shows a simulation result of an estimated value of the slip angle when the offset error is corrected according to the present embodiment when no offset error occurs in the sensor. From the figure, it is understood that the estimation result sufficiently close to the true value can be obtained regardless of whether the offset is corrected or not. 3 and 4
From this, it can be seen that the present offset correction method works effectively when an offset occurs, and does not affect the previous control when the offset does not occur.

FIGS. 5 and 6 show simulation results when the cornering power of the vehicle is reduced by half, that is, when the vehicle model is different from the actual vehicle. The conditions are the same as those in FIGS. From the results shown in FIGS. 5 and 6, it is understood that no major problem occurs even if the vehicle model is different from the actual vehicle. This is because only a stationary error is extracted from the deviation Δβ _g (·) between the calculated value of the slip angular velocity and the estimated value using a low-pass filter having a low cutoff frequency.

As described above, by correcting the offset error of the sensor, the behavior of the vehicle can be grasped more accurately, and the vehicle stability control can be performed without causing the driver to feel unnatural. Become.

Although the above-described embodiment has been described with respect to a so-called 2WS vehicle that does not perform rear wheel steering, it can be applied to a four-wheel steering system (4WS) vehicle.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a vehicle according to an embodiment.

FIG. 2 is a block diagram illustrating a correction method according to the embodiment.

FIG. 3 is a diagram showing a simulation result of the present embodiment.

FIG. 4 is a diagram showing a simulation result of the present embodiment.

FIG. 5 is a diagram showing a simulation result of the embodiment.

FIG. 6 is a diagram showing a simulation result of the present embodiment.

[Explanation of symbols]

24 steering angle sensor, 26 vehicle speed sensor, 28 lateral acceleration sensor, 30 yaw rate sensor, 100 slip angular velocity calculating means, 102 model storage means, slip angular velocity estimating means, 104 slip angular velocity estimating means, 106, 10
8,110 Slip angular velocity correction means.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B62D 113: 00 (72) Inventor Katsuhiro Asano 41-cho, Yokomichi, Oku-cho, Nagakute-cho, Aichi-gun, Aichi 1 Toyota Central Research Laboratory Co., Ltd. (72) Inventor Kenji Totsu 2-1-1 Asahi-cho, Kariya-shi, Aichi Prefecture, Aisin Seiki Co., Ltd. (72) Inventor Yoshiyuki Yasui 2-1-1, Asahi-cho, Kariya-shi, Aichi Prefecture, Aisin Seiki Co., Ltd. (72 Inventor Takayuki Ito 2-1-1 Asahicho, Kariya City, Aichi Prefecture Inside Aisin Seiki Co., Ltd.

Claims (1)

[Claims] 1. A slip angular velocity calculation means for calculating a slip angular velocity based on an output of at least one sensor provided in a vehicle; a model storage means for storing a model relating to a vehicle behavior; and a slip angular velocity calculation provided in the vehicle. A slip angular velocity estimating means for estimating a slip angular velocity based on an output of at least one sensor and the model, including at least one sensor other than the sensor used for the above, and the calculated slip angular velocity and the estimated slip angular velocity A slip angular velocity correcting device that corrects the slip angular velocity based on the slip angular velocity.