JP2878498B2 - Angular acceleration detector - Google Patents

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 an angular acceleration appearing on a car body.

[0002]

2. Description of the Related Art Angular velocity is one type of physical quantity representing the state of a moving object.
Optical fiber gyros, vibrating gyros, gas rate sensors, and the like have often been used.

In recent years, with the improvement of automobile performance, 4WS (four-wheel steering system), ABS (anti-skid brake system), ACTIVE-SUS (active suspension system), TCS (driving force control) (E.g., a system), a control system that considers angular velocity and angular acceleration appearing in the body of an automobile has been increasingly equipped. With this, for example, in Japanese Patent Application Laid-Open No. 62-70666, two acceleration sensors are used to detect A technique for calculating angular acceleration from the output difference of these two acceleration sensors is disclosed, in which the axes are parallel to each other and arranged at equal distances on both sides of the rotational axis of the angular acceleration of a vehicle such as an automobile. According to the technology, it is inexpensive as compared with a conventional gyro-based detection device. 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 may be integrated and used. It should be noted that as related devices of this type, Japanese Patent Application Laid-Open Nos.
Nos. 4-12272 and JP-A-2-37014.

[0005]

In the above prior art, sufficient consideration is not given to the fact that the mounting angle accuracy of the detection axes of the two acceleration sensors is a factor determining the angular acceleration detection accuracy. However, there is a problem that it is difficult to improve the detection accuracy.

That is, when mounting the acceleration sensor on a moving body such as a vehicle, it is inevitable that an error occurs in the mounting angle more or less, and aging is also unavoidable. 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 an 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 includes an error, and the accuracy is reduced.

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

[0008]

In order to achieve the above-mentioned object, first and second two acceleration sensors having an XY plane as an angular acceleration detecting surface and an acceleration detecting axis 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, 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 0. At this time, the acceleration detection values detected by the first and second acceleration sensors are stored as a function of the detected value of the acceleration in the Y-axis direction 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 a Y-axis direction acceleration is applied to a moving body and the Y-axis direction acceleration is detected as an X-axis direction acceleration due to a mounting angle error between the first and second acceleration sensors,
This is given as a function of the acceleration in the Y-axis direction at this time, and the detection values of the first and second acceleration sensors are corrected. Therefore, even if the difference between the two acceleration sensors is calculated to calculate the angular acceleration, the error is calculated. Does not occur.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an angular acceleration detecting device according to the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 shows an embodiment in which the present invention is applied to the 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 and right direction is Y
Axis, the vertical direction is the Z axis, and the first acceleration sensor 2
And the second acceleration sensor 3 are arranged at equal intervals in the Y-axis direction and at a distance L from the center of gravity of the vehicle body of the automobile 1, and fixed so that the acceleration detection direction of each sensor is in the X-axis direction. . Furthermore, the third acceleration sensor 4 for correction is fixed so that it is located between the first and second acceleration sensors 2 and 3 and the acceleration detection direction is the Y-axis direction.

At this time, the first and second acceleration sensors 2,
It is difficult to accurately match the detection axis of No. 3 with the X-axis direction.
An angle error of about ° is expected. Therefore, for 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 the signal processing apparatus. The signals of the first acceleration sensor 2, the second acceleration sensor 3, and the third acceleration sensor 4 for correction are respectively converted by an A / D converter. The signal is converted into a digital signal at 21 and input to the CPU 20. The steering angle sensor 22 and the vehicle speed sensor 2
The signal of No. 3 is also input to the CPU 20. Note that 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. This computer is a computer used for other purposes, such as an anti-skid brake system (ABS) of the automobile 1 or an attitude control device of an aircraft. Alternatively, the arithmetic processing of the angular acceleration according to the present invention may be incorporated 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 software, an OS, a map, and the like therefor are stored in the ROM 24, and the RAM 25 has a role of storing work data. Note that the CPU 20 may be a DSP (Digital Signal Processor).

First, the principle of detecting the yaw angular acceleration in this embodiment will be described. Now, as shown in FIG. 1, assuming that an angular acceleration ω ′ is generated in the vehicle body 1, an acceleration is generated in the first acceleration sensor 2 in the positive direction and in the second acceleration sensor 3 in the negative direction. 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 first and second acceleration sensors ω ′ : Yaw angular acceleration The acceleration detected by each acceleration sensor is actually as follows for 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, ( Only the sign of the second term in equation (2) is reversed:

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

Ω ′ = (G1−G2) / L (4) That is, in principle, the yaw angular acceleration can be obtained by the calculation of equation (4), and if there is no mounting angle error, It can be seen that only the first and second acceleration sensors 2 and 3 need to be used.

Next, a case where there is a mounting angle error in these acceleration sensors 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 into the following equation (5).

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 described above, since the value is quite small, the first
If COS (Δθy) * COS (Δθz) in the term is approximated as COS (Δθy) * COS (Δθz) = 1, the second and third terms result in an error. The error Δω ′ is given by the following equation.

Δω ′ = {Gg * SIN (Δθy) + Gby * SIN (Δθz)} / L (6) In order to calculate an accurate yaw angular acceleration, (6)
A process of canceling the second term and the third term of the equation, that is, the equation (5), to zero is required. Hereinafter, in Examples of the present invention
The cancellation method of the second and third terms of the equation (5) will be described in order.

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

FIG. 3 is a flowchart showing the necessary processing operation of the CPU 20 for this. A series of processes shown in blocks 301 to 306 in FIG.
It is executed periodically by a timer interrupt. First, at block 301, the vehicle speed or wheel speed value is read,
In block 302, X-axis direction accelerations G1 and G2 are read.
In block 303, in order to recognize that the vehicle is in a stopped state, it is determined whether the vehicle speed is zero or the rotation speeds of all the wheels are zero.

However, if this is the only case, the correction is performed even when all the wheels are locked during full braking or the like. Therefore, in block 304, the accelerations G1 and G2 in the X-axis direction detected by the acceleration sensors 2 and 3 are detected. X on average
The axial acceleration is obtained, and if this is in the range of 0 ± A, the offset value is updated in block 305. Where A
Is a small value of about 0.1 G.

In block 306, the offset values are subtracted from the values of the accelerations G1 and G2 regardless of whether the vehicle is stopped or running, and these correction values G1 ', G
Find 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 is making a steady circular turn. The distance between the center of rotation 42 and the center of gravity 41 of the vehicle, that is, the turning radius is R. When the vehicle turns at an angular velocity of ω, a spherical acceleration represented by the following equation (7) is generated.

Gby = R * ω ² (7) In this embodiment, a correction function as shown in FIG. 5 is used in order to cancel the third term of the equation (5). ing. FIG. 5 shows a value obtained by learning the value of G2 ′, which should not appear for the ball-center acceleration Gby, which is the lateral G, at the time of steady circular turning, that is, the error G2 ₀ ′, as a correction function. In this embodiment, the correction is performed by subtracting G2 ₀ ′ obtained by the correction function from the measured value G2 ′. The operation of this embodiment is shown in a flowchart of FIG. .

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

In block 603, it is determined whether or not the steering angle θ 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 vehicle 1 is in a steady circular turning state. First, in block 605, the lateral acceleration G3 and the corrected longitudinal accelerations G1 ′ and G2 ′ are stored in the respective memory areas by Gby.
₀ , G1 ₀ ′, and G2 ₀ ′. Next, in block 606, two types of correction gains GAIN1 and GAIN
Ask for 2. Thereafter, in block 607, the correction values G1 "and G2" are always obtained by subtracting the acceleration corresponding to 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 obtained correction values G1 ", G2"
Is substituted into equation (4), an accurate yaw angular acceleration can be obtained. Therefore, according to this embodiment, high-accuracy angular acceleration can be detected by the acceleration sensor, and a low-cost angular acceleration detector can be easily obtained.

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

V = R * ω (8) Then, when this is substituted into the expression (7), the expression (9) is obtained.

Gby = V * ω (9) Here, since the yaw angular velocity ω is a function of the velocity V and the steering wheel angle θ, these relations are determined as shown in FIG. A map is stored in advance in the ROM 24, and a map search is performed based on the speed V and the steering angle θ to obtain the yaw angular velocity ω.
Is calculated, Gby can be estimated by the equation (9).
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 in the case where the third acceleration sensor 4 is used. .

By the way, in the above embodiment, as shown in FIG.
8 (a) and 8 (b), it is possible to obtain an accurate yaw angular acceleration by performing the same correction even when the vehicle 1 is mounted in front of and behind the vehicle 1. it can. Therefore, according to this embodiment, since the third acceleration sensor becomes unnecessary, a high-accuracy angular acceleration detecting device can be provided at a lower cost.

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

Therefore, in the embodiment described below, the outputs of these acceleration sensors are used in the ACTIVE-SU of the automobile.
It is shared by S and ABS.

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

On the other hand, in this embodiment, the ABS control device 9
1 to obtain an accurate yaw angular acceleration ω ′, which requires a lateral G signal. For this reason, the communication between the ACTIVE-SUS control device 90 and the ABS control device 91 can be performed. It is.

Thus, 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 detection and correction of the yaw angular acceleration can be performed as described above. .

At this time, the ACTIVE-SUS control device 90 not only transmits the signal of the acceleration sensor 4 to the ABS control device 91 but also receives the yaw angular acceleration ω ′ calculated by the ABS control device 91, This can be used for suspension control. Therefore, according to this embodiment, it is possible to sufficiently respond to high performance of an automobile.

[0044]

According to the present invention, it is possible to detect angular acceleration with high accuracy only by using an acceleration sensor, so that the cost is lower than that of a conventional detecting device using a gyro or the like, and the present invention is applied to automobiles and the like. Thus, it is possible to sufficiently contribute to the practical use of various control systems such as 4WS.

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

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one 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 one embodiment of the present invention.

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

FIG. 5 is an explanatory diagram of a correction function in one embodiment of the present invention.

FIG. 6 is a flowchart for explaining the operation of one embodiment of the present invention.

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

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

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

[Explanation of symbols]

 Reference Signs List 1 automobile 2 first acceleration sensor 3 second acceleration sensor 4 third acceleration sensor

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Ota 2520 Oaza Takaba, Katsuta-shi, Ibaraki Hitachi, Ltd.Automotive Equipment Division (72) Inventor Hayato Sugawara 2520 Odaikaba, Katsuta-shi, Ibaraki Hitachi (56) References JP-A-55-18959 (JP, A) JP-A-63-134319 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) ) G01P 15/00-15/135 G01P 21/00

Claims (9)

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