JPH05272974A - Surface grade detector for automobile - Google Patents

Abstract

PURPOSE:To detect a surface grade irrespective of a traveling state of an automobile wherein the detector is simple in structure, highly vibration-proof and durable, while no accumulated error occurs even after a long time measurement. CONSTITUTION:A surface grade theta is calculated in a controller 4 based on an acceleration signal alphax supplied from an acceleration sensor 2 and a velocity signal V supplied from a velocity sensor 3 according to an equation of theta=-sin<-1>{alphax+dv/dt)/g}, where (g) is acceleration of free fall.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a slope of a road surface on which a vehicle runs.

[0002]

2. Description of the Related Art Conventionally, as a device for detecting a road gradient, there are various devices such as a gradient meter using gravity, a gradient meter using a mechanical gyro, and a gradient meter using an optical fiber gyro (for example, , JP-A-61-104218).

[0003]

However, the gradient meter utilizing gravity can detect the gradient in a stationary state or a state where the vehicle is traveling at a constant vehicle speed, but cannot detect the gradient in an acceleration / deceleration state. is there. In addition, the gradiometer using the mechanical gyro has a complicated structure and is inferior in vibration resistance and wear resistance, and it takes time to reach a detectable state. And a gradiometer using an optical fiber gyro,
Since the gradient is obtained by integrating the angular velocities, the cumulative error increases due to long-term measurement, and it is necessary to periodically correct the horizontal plane.

The present invention has been made by paying attention to the technical problem of such a conventional inclinometer, and it has a simple structure and can detect whether the vehicle is driving, braking, or stationary. It is an object of the present invention to provide a road surface gradient detecting device for a vehicle that is capable of performing the above-mentioned measurement and that does not cause a cumulative error or the like even when the measurement is performed for a long time.

[0005]

In order to achieve the above object, a vehicle road surface gradient detecting device of the present invention detects a vehicle acceleration V and a longitudinal acceleration detecting means for detecting a longitudinal acceleration α _x of the vehicle. Vehicle speed detection means and the longitudinal acceleration α
_x , the vehicle speed V and the gravitational acceleration g, and a road surface gradient calculating means for calculating a road surface gradient θ according to the formula θ = −sin ⁻¹ {(α _x + dV / dt) / g}.

[0006]

As shown in FIG. 3, it is assumed that the vehicle A is traveling on a road surface R having a road surface gradient θ with respect to the horizontal plane H. The front-back direction with respect to the vehicle body is the x direction (the front of the vehicle is positive), the inertial force in the x direction is F _x , the acceleration generated at the mass point of the mass m by this inertial force F _x is α _x , the vehicle speed is V, and the gravity is if the acceleration a _{g, F x = mα x ......} (1) F x = -mg · sinθ-m · dV / dt ...... (2) motion equation that is satisfied.

From these equations (1) and (2), α _x = −g · sin θ−dV / dt and sin θ = (− α _x −dV / dt) / g. Therefore, the road surface gradient θ is θ = Sin ^-1 {(-α _x -dV / dt) / g} = -sin ^-1 {(α _x + dV / dt) / g} (3) However, −π / 2 ≦ θ ≦ π / 2.

Therefore, according to the present invention, when the longitudinal acceleration α _x of the vehicle is detected by the longitudinal acceleration detecting means and the vehicle speed V is detected by the vehicle speed detecting means, the road surface slope calculating means (3) is used. The road gradient θ is calculated based on the equation.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. First, the configuration will be described. The road surface gradient detecting device 1 includes an acceleration sensor 2 as a longitudinal acceleration detecting means for detecting a longitudinal acceleration of a vehicle, a vehicle speed sensor 3 as a vehicle speed detecting means for detecting a vehicle speed, and an acceleration. A controller 4 that calculates a road surface slope θ based on an acceleration signal α _x output from the sensor 2 and a vehicle speed signal V output from the vehicle speed sensor 3, and a display device 5 that displays the road surface slope θ obtained by the controller 4. And are equipped with.

For the acceleration sensor 2, for example, a strain type accelerometer or the like arranged at the center of rotation of the vehicle in the vehicle yaw direction of the coordinate system fixed to the vehicle body (usually the center of the rear axle) is applied. If the vehicle is equipped with an automatic transmission, an anti-lock brake device, or the like, the longitudinal acceleration sensor provided for them may also be used.

The output of the acceleration sensor 2 is supplied to the controller 4 via a low pass filter 6 in order to remove unnecessary high frequency components. On the other hand, as the vehicle speed sensor 3, an electromagnetic pickup installed to face the speedometer pinion gear (worm gear) in the transmission is applied. Since the output of the electromagnetic pickup is a pulse wave, the output of the vehicle speed sensor 3 is once input to the F / V converter 7 that converts the frequency into a voltage value, and passes through a low-pass filter 8 that removes unnecessary high-frequency components therefrom. Are supplied to the controller 4.

The controller 4 is connected to A (not shown).
A D / D converter, a microcomputer, and the like, and performs a predetermined calculation process described later based on the supplied acceleration signal α _x and vehicle speed signal V to obtain a road surface gradient θ, and obtains the result as a driver seat. The data is output to the display device 5 including a display mounted on the front part. FIG. 2 is a flowchart showing an outline of processing executed by the microcomputer in the controller 4, and the operation of this embodiment will be described below with reference to the flowchart.

First, in step, the acceleration signal α _x supplied from the acceleration sensor 2 and the vehicle speed signal V supplied from the vehicle speed sensor 3 are read, and the process proceeds to step. The acceleration signal α _x and the vehicle speed signal V are read after being converted into digital values.
Although the sampling interval of the / D conversion becomes a problem, the fluctuation of the road surface gradient θ finally calculated is generally gradual, so that the sampling interval of the A / D conversion does not need to be so high. According to an experiment conducted by the present inventor, 10H
It has been confirmed that sufficient accuracy can be obtained at a sampling interval of about z.

In step, an average value α _x 'of the acceleration signal α _x within a predetermined time is calculated. This is because the noise and the like are canceled more accurately when the acceleration signal α _x as the instantaneous value is applied to the calculation described later as it is as the average value α _x ′ within a predetermined time. Is obtained. According to an experiment conducted by the present inventor, the time interval for obtaining the average value α _x 'is 0.5.
It has been confirmed that sufficient accuracy can be obtained within about 2.0 seconds.

Then, the process proceeds to step and the vehicle speed signal V
Is differentiated to calculate dV / dt, the process proceeds to step, and the road surface gradient θ is calculated based on the following equation (4). θ = −sin ⁻¹ {(α _x '+ dV / dt) / g} (4) When the road surface gradient θ is obtained, the process proceeds to step and the calculation result is output and displayed on the display device 5. In the present embodiment, the steps from step to step correspond to the road surface gradient calculating means.

Here, as can be seen from FIG. 3 and the above equations (1) and (2), the acceleration signal α _x is not only the acceleration dV / dt which is the value obtained by differentiating the vehicle speed V, but also the gravitational acceleration g. A component (first term on the right-hand side of the above equation (2)) that varies due to the influence of (1) is also included. Therefore, if the vehicle A is in the horizontal plane H,
Assuming that the vehicle is traveling at an acceleration / deceleration on a road surface parallel to the road surface, the road surface gradient θ = 0.
Therefore, the acceleration signal α _x and the acceleration dV / dt, which is the value obtained by differentiating the vehicle speed V, have the same magnitude, although the signs are opposite.

Therefore, in the above equation (4), since α _x '+ dV / dt = 0, the calculation result is 0, and the accurate road surface gradient θ is obtained. Even when the vehicle A is traveling (or stopped) at a constant speed on the road surface parallel to the horizontal plane H, the acceleration signal α _x = 0 and dV / dt = 0 are obtained. Therefore, the result of the equation (4) is obtained. Becomes 0, and an accurate road surface slope θ can be obtained.

On the other hand, when the vehicle A is accelerating and decelerating on the road surface R which is not parallel to the horizontal plane H, the acceleration signal α _x contains a component (-mg · sin θ) based on the gravitational acceleration g. Therefore, since α _x '+ dV / dt = −g · sin θ (≠ 0), the road surface slope θ is calculated based on the above equation (4).

When the vehicle A is traveling (or stopped) on the road surface R at a constant speed, dV / dt = 0. In this case, α _x '= -g · sin θ Therefore, the accurate road surface slope θ can be obtained based on the equation (4). As described above, in the present embodiment, based on the longitudinal acceleration α _x of the vehicle and the vehicle speed V,
Since the road surface gradient θ is calculated according to the above equation (4), the road surface gradient θ can be accurately obtained even when the vehicle is in an acceleration / deceleration state, and even when continuously measured for a long time,
No cumulative error will occur.

Moreover, since only the acceleration sensor 2 and the vehicle speed sensor 3 are required as the sensor, the structure is simple and advantageous in terms of vibration resistance and durability. If the vehicle is already equipped with these sensors, the outputs of these sensors may be used, so that the cost is not significantly increased.

[0021]

As described above, according to the present invention,
Since the road surface gradient θ is calculated based on the longitudinal acceleration and the vehicle speed V, the road surface gradient θ can be accurately obtained even when the vehicle is in an acceleration / deceleration state, and the road surface gradient θ can be continuously measured for a long time. However, there is an effect that a cumulative error does not occur, the structure is simple, and it is advantageous in terms of vibration resistance and durability.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing an outline of processing executed in a controller.

FIG. 3 is a diagram illustrating the operation of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Road gradient detection device 2 Acceleration sensor (front-back acceleration detection means) 3 Vehicle speed sensor (vehicle speed detection means) 4 Controller 5 Display device 6,8 Low-pass filter 7 F / V converter

Claims (1)

[Claims] 1. A longitudinal acceleration detecting means for detecting a longitudinal acceleration α _x of a vehicle, a vehicle speed detecting means for detecting a vehicle speed V, and θ = based on the longitudinal acceleration α _x , the vehicle speed V and a gravitational acceleration g. A road surface gradient detecting device for a vehicle, comprising: a road surface gradient calculating means for calculating a road surface gradient θ according to the expression −sin ⁻¹ {(α _x + dV / dt) / g}.