JPH0572223A - Detecting device of angular acceleration - Google Patents

Abstract

PURPOSE:To obtain a detecting device of angular acceleration which can detect the rotational angular acceleration of a moving body such as an automobile highly precisely, by using an acceleration sensor. CONSTITUTION:In the case when the rotational angular acceleration omega of an automobile 1 is detected by using first and second acceleration sensors 2 and 3, a means (a third acceleration sensor 4 or an acceleration estimating means) which detects acceleration in the direction perpendicular to the aforesaid sensors 2 and 3 is provided and thereby a detection error of the rotational angular acceleration caused by an error in angles of fitting of the first and second acceleration sensors 2 and 3 is corrected. Although the acceleration sensors are used, sufficiently accurate detection of the angular acceleration is enabled and a detecting device of the angular acceleration of low cost can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular acceleration detecting device using an acceleration sensor, and more particularly to an angular acceleration detecting device suitable for detecting the angular acceleration appearing on the body of an automobile.

[0002]

2. Description of the Related Art Angular velocity is a kind of physical quantity that represents the state of a moving object.
Optical fiber gyros, vibrating gyros, gas rate sensors, etc. were often used.

By the way, in recent years, as the performance of automobiles has improved, 4WS (four-wheel steering system), ABS (anti-skid brake system), ACTIVE-SUS (active suspension system), TCS (driving force control) System) and other control systems that make angular velocity and angular acceleration appearing in the body of an automobile a problem. With this, for example, in JP-A-62-70766, two acceleration sensors are used to detect these. Disclosed is a technique for calculating angular acceleration from the output difference of these two acceleration sensors, which are arranged equidistantly on both sides of the angular acceleration rotation axis of a vehicle such as an automobile so that the axes are parallel to each other. According to the technology, the cost is lower than that of the conventional detection device using a gyro, etc. Into, it has become possible to provide a possibility.

This publication also discloses that, when a physical quantity in the dimension of angular velocity is required, the angular acceleration obtained as described above should be integrated and used. Incidentally, as related devices of this type, further disclosed are JP-A-60-256065 and JP-A-6-26605.
Nos. 4-12272 and JP-A-2-37014 can be mentioned.

[0005]

The above-mentioned prior art does not give sufficient consideration to the fact that the mounting angle accuracy of the detection axes of the two acceleration sensors is a factor that determines the angular acceleration detection accuracy. There is a problem that it is difficult to improve the detection accuracy of.

That is, when the acceleration sensor is attached to a moving body such as a vehicle, it is inevitable that an error in the attachment angle is caused to a greater or lesser degree, and that the secular change is also inevitable. At this time, when the acceleration including the Y-axis component appears on the moving body with the angular acceleration detection surface as the XY plane, the Y-axis component of this acceleration is measured as the X-axis component due to the error in the mounting angle. As a result, the angular acceleration calculated by taking the difference between the output signals of the two acceleration sensors also contains an error, which lowers the accuracy.

An object of the present invention is to provide an angular acceleration detecting device capable of maintaining sufficient angular acceleration detection accuracy even if an error exists in the mounting angle of the acceleration sensor.

[0008]

In order to achieve the above object, two acceleration sensors, a first and a second acceleration sensor, whose angular acceleration detection surface is an XY plane and whose acceleration detection axis is parallel to the X axis, are used. In the angular acceleration detecting device for detecting the angular acceleration around the Z axis perpendicular to the plane, a means for detecting the acceleration in the Y axis direction is provided, and it is determined that the angular acceleration around the Z axis of the moving body is zero. At this time, the acceleration detection values detected by the first and second acceleration sensors are stored as a function of the detection value of the Y-axis direction acceleration at that time, and thereafter, each time the acceleration in the Y-axis direction is detected, The function of the detected value is used as a correction value to correct the values of the first and second acceleration sensors.

[0009]

When the Y-axis direction acceleration is applied to the moving body and the Y-axis direction acceleration is detected as the X-axis direction acceleration due to the mounting angle error between the first and second acceleration sensors, it is
It is given as a function of the Y-axis direction acceleration at this time, and the detection values of the first and second acceleration sensors are corrected by this. Therefore, even if the angular acceleration is calculated by taking the difference between the two acceleration sensors, the error Will not occur.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The angular acceleration detecting device according to the present invention will be described in detail below with reference to the illustrated embodiments. FIG. 1 is an embodiment in which the present invention is applied to detection of yaw angular acceleration of an automobile. FIG. 1 (a) is a top view and FIG. 1 (b) is a side view. Direction is X-axis, left-right direction is Y
Axis, and the vertical direction is the Z axis, and the first acceleration sensor 2
The second acceleration sensor 3 and the second acceleration sensor 3 are arranged at equal intervals in the Y axis direction from the center of gravity of the vehicle body of the automobile 1 and are fixed so that the acceleration detection direction of each sensor is the X axis direction. .. Further, the third correction acceleration sensor 4 is fixed in the middle of the first and second acceleration sensors 2 and 3 so that the acceleration detection direction is the Y-axis direction.

At this time, the first and second acceleration sensors 2,
It is difficult to exactly match the detection axis of 3 with the X-axis direction, and if distortion of the vehicle body over time is also included, it is inevitably 0 ± 2.
An angle error of about ° is expected. Therefore, regarding the second acceleration sensor 3, the mounting angle errors around the X axis, the Y axis, and the Z axis are defined as Δθx, Δθy, and Δθz, respectively.
Of these, the mounting error around the X axis does not affect the acceleration detection value, so only Δθy and Δθz are considered.

FIG. 2 shows an embodiment of a signal processing device. The signals of the first acceleration sensor 2, the second acceleration sensor 3 and the third acceleration sensor 4 for correction are respectively A / D converters. It is converted into a digital signal in 21 and input to the CPU 20. In addition, the steering wheel steering angle sensor 22 and the vehicle speed sensor 2
The signal No. 3 is also input to the CPU 20. The vehicle speed sensor 23 may be a plurality of wheel speed sensors.

The CPU 20 constitutes a computer together with the ROM 24 and the RAM 25. The computer is a computer used for other purposes such as the ABS (anti-skid brake system) of the automobile 1 and the attitude control device of the aircraft. Alternatively, the calculation process of the angular acceleration according to the present invention may be incorporated therein in the form of software. Of course, it goes without saying that it may be provided only for the calculation processing of the angular acceleration.

Here, the CPU 20 performs arithmetic processing, and the software, OS, maps and the like for that purpose are stored in the ROM 24, and the RAM 25 has a role of storing work data. The CPU 20 may be a DSP (digital signal processor).

First, the principle of detection of yaw angular acceleration in this embodiment will be described. As shown in FIG. 1, if angular acceleration ω ′ occurs in the vehicle body 1, this causes acceleration in the positive direction in the first acceleration sensor 2 and in the negative direction in the second acceleration sensor 3, The absolute value of the acceleration generated at this time can be expressed by the following equation.

G (ω ′) = (L * ω ′) / 2 (1) G (ω ′): Acceleration generated by ω ′ L: Distance between the first and second acceleration sensors ω ′ The acceleration detected by each acceleration sensor is as follows in the acceleration sensor 2 in consideration of the longitudinal acceleration Gbx at the center of gravity.

G1 = Gbx + (L * ω ') / 2 (2) G1: acceleration measured by the acceleration sensor 2 Gbx: longitudinal acceleration at the vehicle center of gravity Next, in the acceleration sensor 3, It becomes the following equation in which only the sign of the second term of the equation (2) is reversed.

G2 = Gbx− (L * ω ′) / 2 (3) G2: Acceleration measured by the acceleration sensor 3 Then, the yaw angular acceleration is the measured acceleration G
1 and G2 are calculated by the following equation.

Ω '= (G1-G2) / L (4) In other words, in principle, the yaw angular acceleration can be obtained by the calculation of the equation (4), and if there is no mounting angle error, It can be seen that it is sufficient to use only the first and second acceleration sensors 2 and 3.

Next, the case where these acceleration sensors have a mounting angle error will be described. For simplification of description, it is assumed here that only the acceleration sensor 3 has a mounting angle error. Then, equation (3) can be rewritten as equation (5) below.

G2 = {Gbx- (L * ω ') / 2} * COS (Δθy) * COS (Δθz) -Gg * SIN (Δθy) -Gby * SIN (Δθz) (5) Gg: Gravity G Gby: lateral acceleration at the center of gravity of the vehicle In the equation (5), the mounting angle errors Δθy and Δθz are
As mentioned above, since it is a fairly small value,
When COS (Δθy) * COS (Δθz) in the term is approximated to COS (Δθy) * COS (Δθz) = 1, the second and third terms become an error, and when calculated by substituting in the equation (4), The error Δω ′ is given by the following equation.

Δω ′ = {Gg * SIN (Δθy) + Gby * SIN (Δθz)} / L (6) Therefore, in order to calculate the accurate yaw angular acceleration, (6)
It is necessary to perform processing for canceling the equation, that is, the second and third terms of equation (5) to zero. Hereinafter, in the examples of the present invention
The canceling method for the second and third terms of equation (5) will be described in order.

First, the second term of the equation (5) is because the acceleration sensor has a mounting error angle Δθy about the Y axis, in other words, the detection direction is upward or downward, It is an error to pick up G.
Therefore, in order to cancel this component, the output value of the acceleration sensor 3 may be stored as an offset when the vehicle is stopped, and thereafter subtracted from the entire output value range.

The processing operation by the CPU 20 necessary for this is shown in a flow chart in FIG. The series of processes shown in blocks 301 to 306 of FIG.
It is executed periodically by a timer interrupt. First, in block 301, the vehicle speed or wheel speed value is read,
In block 302, the X-axis direction accelerations G1 and G2 are read.
In block 303, in order to recognize that the vehicle is stopped, it is determined whether the vehicle speed is zero or the rotation speeds of all the wheels are zero.

However, with this alone, the correction is performed even when all the wheels are locked, such as at the time of full braking. Therefore, in block 304, the accelerations G1 and G2 in the X-axis direction detected by the acceleration sensors 2 and 3 are detected. Average X
The axial acceleration is calculated, and if it is within the range of 0 ± A, the offset value is updated in block 305. Where A
The value of is a small value of about 0.1G.

In block 306, the offset value is subtracted from the values of the accelerations G1 and G2 regardless of whether the vehicle is stationary or running, and these correction values G1 'and G2 are obtained.
Ask for 2 '. By performing the above processing, the second term of the equation (5) can be canceled.

Next, a method of canceling the third term of the equation (5) will be described.

FIG. 4 shows how the lateral G occurs when the automobile 1 makes a steady circular turn. The distance between the rotation center 42 and the center of gravity 41 of the vehicle, that is, the turning radius is R. At this time, if the vehicle turns at an angular velocity of ω, the ball-center acceleration shown by the following equation (7) is generated.

Gby = R * ω ² (7) Therefore, in this embodiment, in order to cancel the third term of the equation (5), a correction function as shown in FIG. 5 is used. ing. This FIG. 5 is created as a correction function by learning the value of G2 ′, which should not appear for the spherical center acceleration Gby which is the lateral G, that is, the error G2 ₀ ′, at the time of steady circle turning, in this embodiment, hereinafter, shows G2 ₀ determined by the correction function which was configured to perform the correction by subtracting the 'a, the measured value G2', 6 by the operation of this embodiment in the flow chart ..

In FIG. 6, first in block 601,
The vehicle speed V, steering wheel steering angle θ, longitudinal acceleration correction values G1 ′, G2 ′, and lateral acceleration G3 of the automobile 1 are read. Subsequent blocks 602 to 604 are processes for determining that the vehicle is making a steady circle turn, and when all of these conditions are satisfied, it is determined that the automobile 1 is making a steady circle turn. First, block 60
At 2, it is determined whether the steering angle θ of the steering wheel is turned to the right or left by a predetermined value θth or more. Note that this predetermined value θth
For this, an angle of about 5 ° may be set.

In block 603, it is determined whether or not the steering angle θ of the steering wheel is kept constant during turning. here,
As the judgment value θth ′, an angular velocity of about 1 ° / sec is used. Then, in block 604, it is determined whether or not the vehicle speed V is kept constant during turning.

In blocks 605 and 606, processing is performed when the automobile 1 is in a steady circle turning state. First, in block 605, the lateral acceleration G3 and the corrected longitudinal accelerations G1 ′ and G2 ′ are stored in respective memory areas as Gby.
Store as ₀ , G1 ₀ 'and G2 ₀ '. Next, in block 606, two types of correction gains GAIN1 and GAIN
Ask for 2. After that, in block 607, the correction values G1 ″ and G2 ″ are constantly obtained by subtracting the acceleration for the error obtained from the value of the lateral acceleration G3.

By performing the above processing, the third term of the equation (5) can be canceled and the calculated correction values G1 "and G2" are obtained.
By substituting Eq. (4) into equation (4), an accurate yaw angular acceleration can be obtained. Therefore, according to this embodiment, the acceleration sensor can detect the angular acceleration with high accuracy, and the low-cost angular acceleration detecting device can be easily obtained.

Next, another embodiment of the present invention will be described. In this embodiment, correction is performed based on the estimated lateral G without using the third acceleration sensor 4 in the above embodiment. First, in the vehicle in the steady circular turn shown in FIG. 4, the function shown in the following equation (8) is established.

V = R * ω (8) Then, by substituting this into the equation (7), the equation (9) is obtained.

Gby = V * ω ... (9) Here, since the yaw angular velocity ω is a function of the velocity V and the steering angle θ of the steering wheel, as shown in FIG. The map is stored in the ROM 24 in advance, and the map is searched by the speed V and the steering wheel steering angle θ, and the yaw angular speed ω
Gby can be estimated by the equation (9) by calculating
By substituting the estimated Gby into G3 and executing the processing of FIG. 6, the correction values G1 ″ and G2 ″ of the longitudinal acceleration can be obtained in the same manner as when the third acceleration sensor 4 is used. ..

By the way, in the above embodiment, as shown in FIG. 1, the acceleration sensors 2, 3 are arranged on the left and right sides of the automobile 1.
However, as shown in FIGS. 8A and 8B, the same yaw angular acceleration can be obtained by performing the same correction even when the vehicle 1 is mounted before and after the vehicle 1. it can. Therefore, according to this embodiment, the third acceleration sensor is unnecessary, so that it is possible to provide a highly accurate angular acceleration detection device at a lower cost.

Next, another embodiment of the present invention will be described. In the embodiment of FIG. 1, the first, second and third three
Although the output of each acceleration sensor is used only for detecting the yaw angular velocity ω, these acceleration sensors are
As described above, for example, 4WS (four-wheel steering system), A
BS (Anti-skid brake system), ACTI
It can be used for various other controls such as a control system such as VE-SUS (active suspension system) or TCS (driving force control system) that makes the angular velocity and angular acceleration appearing in the body of an automobile a problem.

Therefore, in the embodiments described below, the outputs of these acceleration sensors are sent to the ACTIVE-SU of the automobile.
It is also used for S and ABS.

In FIG. 9, 90 is an ACTIVE-SU.
The S control unit (C / U) controls the suspension of the automobile 1 by using the lateral G of the automobile 1 detected by the acceleration sensor 4 here. Reference numeral 91 is an ABS control unit (C / U), which uses the front and rear G of the automobile 1 detected by the acceleration sensor 2 and the acceleration sensor 3 for brake control.

On the other hand, in this embodiment, the ABS controller 9
1 is configured to obtain an accurate yaw angular acceleration ω ′, and then a lateral G signal is required. Therefore, the active-SUS controller 90 and the ABS controller 91 can communicate with each other. I am doing it.

As a result, the ABS control device 91 can obtain the signal of the acceleration sensor 4 in addition to the signals of the acceleration sensor 2 and the acceleration sensor 3, so that the yaw angular acceleration can be detected and corrected as described above. ..

At this time, the ACTIVE-SUS controller 90 not only sends the signal of the acceleration sensor 4 to the ABS controller 91, but also receives the yaw angular acceleration ω'calculated by the ABS controller 91. It is also possible to use this for suspension control. Therefore, according to this embodiment, high performance of the automobile can be sufficiently satisfied.

[0044]

According to the present invention, since it is possible to detect highly accurate angular acceleration simply by using an acceleration sensor, the cost is lower than that of a conventional detection device using a gyro or the like, and it is applied to an automobile or the like. Thus, it can sufficiently contribute to the practical application of various control systems such as 4WS.

Further, according to the present invention, when applied to an automobile, lateral G can be estimated by a vehicle speed signal and a steering wheel steering angle signal for correction processing, and an accurate yaw angular acceleration can be detected at a lower cost. Therefore, accurate control can be performed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of a rotational angular acceleration detecting device according to the present invention.

FIG. 2 is a block diagram of a signal processing system according to an embodiment of the present invention.

FIG. 3 is a flowchart for explaining the operation of the embodiment of the present invention.

FIG. 4 is an explanatory diagram of a state in which a lateral G is generated during a steady turn in an automobile.

FIG. 5 is an explanatory diagram of a correction function according to an embodiment of the present invention.

FIG. 6 is a flow chart for explaining the operation of the embodiment of the present invention.

FIG. 7 is an explanatory diagram of a steady yaw angular velocity map used in an embodiment of the present invention.

FIG. 8 is an explanatory diagram showing another embodiment of the present invention.

FIG. 9 is an explanatory diagram showing still another embodiment of the present invention.

[Explanation of symbols]

 1 Automotive 2 1st acceleration sensor 3 2nd acceleration sensor 4 3rd acceleration sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Horikoshi 2520, Takaba, Katsuta-shi, Ibaraki Hitachi, Ltd. Automotive Equipment Division (72) Inventor Kenji Ota 2520, Takata, Katsuta-shi, Ibaraki Hitachi, Ltd. (72) Inventor Hayato Sugawara, Katsuta City, Ibaraki 2520, Takaba, Hitachi Automotive Engineering Co., Ltd.

Claims (9)

[Claims] 1. A first and a second mounted on the XY plane of a moving body at a predetermined distance in the Y-axis direction and attached so that their respective detection directions are parallel to the X-axis. In the angular acceleration detection device of the type that uses an acceleration sensor to detect the rotational angular acceleration about the Z axis perpendicular to the XY plane from the difference between the outputs of these first and second acceleration sensors, A third acceleration sensor that detects acceleration in the Y-axis direction is provided on a straight line connecting the two acceleration sensors, and the output of the third acceleration sensor provides the Y-axis direction acceleration of the moving body and the first and second acceleration sensors. An angular acceleration detection device, characterized in that it is configured to correct a detection error of a rotational angular acceleration caused by a mounting angle error of the second acceleration sensor. 2. The invention according to claim 1, wherein the moving body is an automobile, and the X-axis direction is the longitudinal direction of the automobile,
The Y-axis direction is the left-right direction of the vehicle, and the Z-axis direction is the up-down direction of the vehicle. The first and second acceleration sensors detect longitudinal acceleration, and the yaw of the vehicle is calculated from the difference. An angular acceleration detecting device, which is configured to obtain an angular acceleration, and is configured to correct the yaw angular acceleration by the lateral acceleration detected by the third acceleration sensor. 3. The invention according to claim 1, wherein the moving body is an automobile, and the X-axis direction is the left-right direction of the automobile.
The Y-axis direction is the longitudinal direction of the vehicle, and the Z-axis direction is the vertical direction of the vehicle. The first and second acceleration sensors detect the lateral acceleration, and the yaw of the vehicle is calculated from the difference. Configured to determine angular acceleration,
An angular acceleration detecting device, wherein the yaw angular acceleration is corrected by the longitudinal acceleration detected by the third acceleration sensor. 4. A first and a second, which are arranged at a predetermined distance in the Y-axis direction on the XY plane of the moving body, and are attached so that the respective detection directions are parallel to the X-axis. In the angular acceleration detecting device of the type that uses an acceleration sensor to detect the rotational angular acceleration about the Z axis perpendicular to the XY plane from the difference between the outputs of the first and second acceleration sensors,
Acceleration estimating means for estimating the acceleration in the axial direction is provided, and the output of the acceleration estimating means is used to calculate the Y-axis direction acceleration of the moving body and the rotational angular acceleration caused by the mounting angle error between the first and second acceleration sensors. An angular acceleration detection device characterized in that it is configured to correct a detection error. 5. The invention according to claim 4, wherein the moving body is an automobile, and the X-axis direction is the front-back direction of the automobile,
The Y-axis direction is the left-right direction of the vehicle, and the Z-axis direction is the up-down direction of the vehicle. The first and second acceleration sensors detect longitudinal acceleration, and the yaw of the vehicle is calculated from the difference. The acceleration estimating means is configured to obtain an angular acceleration, and the acceleration estimating means is configured to estimate the lateral acceleration from the signals of the wheel speed sensor and the steering wheel steering angle sensor of the automobile to correct the yaw angular acceleration. An angular acceleration detection device characterized by the above. 6. The invention according to claim 4, wherein the moving body is an automobile, and the X-axis direction is the left-right direction of the automobile,
The Y-axis direction is the longitudinal direction of the vehicle, and the Z-axis direction is the vertical direction of the vehicle. The first and second acceleration sensors detect the lateral acceleration, and the yaw of the vehicle is calculated from the difference. Configured to determine angular acceleration,
An angular acceleration detecting device characterized in that the acceleration estimating means is configured to correct the yaw angular acceleration by estimating the longitudinal acceleration from the signals of the wheel speed sensor and the steering angle sensor of the automobile. .. 7. The invention according to claim 1, wherein the first control device receives signals from the first and second acceleration sensors as inputs, and the second control device receives signals from the third acceleration sensor as inputs. An angular acceleration detecting device, characterized in that the device is provided independently and a communication means is provided between these control devices. 8. The invention according to claim 4, wherein a first control device receives signals from the first and second acceleration sensors, and a second control device receives signals from the acceleration estimating means. Is independently provided, and a communication means is provided between these control devices. 9. The invention according to claim 1 or 4, wherein the moving body is an automobile, and the outputs of the first and second acceleration sensors are 4WS (four-wheel steering system) and ABS of the automobile.
(Anti-skid brake system), ACTIVE
-SUS (Active Suspension System), T
It is incorporated in 1 of the control devices including a CPU for CS (driving force control system) in the form of software, and is configured to commonly use the CPU of this control device to detect angular acceleration. An angular acceleration detection device.