JP2001296122A - Detector for road grade - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make precisely detectable a road-surface grade without delay, with respect to a change in an actual road grade. SOLUTION: A G sensor is arranged on the axle of a vehicle. The road- surface grade is detected, on the basis of the acceleration of the vehicle and on the basis of the output value of the G sensor. When the rate of change of the road-surface grade calculated by a road-surface-grade detection means is a value which cannot be an actual value, the calculated value of the road- surface grade prior to the change is continued to be output, until the calculated value of the road-surface grade returns to a value before the change. Even in a running state where the vehicle is subjected to disturbance from a road surface or the like and that the accuracy of the input value of the G sensor is lowered, an abnormal road-surface grade value which is generated by the disturbance is removed, without delays with reference to the change in the actual road grade, and the road-surface grade can be detected precisely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, there is known a technique of detecting a gradient of a road surface on which a vehicle is traveling and using the detected gradient as an input element for vehicle control. Recently, a method of calculating a road surface inclination angle from a G sensor installed in the traveling direction of a vehicle and an acceleration with respect to the road surface calculated from a wheel speed sensor as disclosed in Japanese Patent No. 2626003 has been considered.

[0003] In addition, G in the vehicle traveling direction of the actual vehicle.
In order to stably obtain a sensor output value, it is common to attach this G sensor to a position that is hardly subject to vibration from an engine, wheels, or the like. For example, it is conceivable to provide a small room at the bottom of the console box and attach it there.

[0004]

In the case where the G sensor is mounted on a position hardly subject to vibration from an engine or wheels, for example, when the G sensor is mounted on a body above a suspension of a vehicle (specifically, a console box) Medium), although the output value of the G sensor has the advantage of changing stably, the output of the G sensor is compared with the change in the actual road gradient due to the change in vehicle weight and the deflection of the suspension due to the road gradient. Values tend to lag.

[0005] In frame vehicles such as trucks and commercial vehicles, the frame is distorted due to the road gradient.
The location of the sensor may not be parallel to the actual road surface. As described above, the output value of the G sensor is greatly affected by the installation location, and a sufficiently accurate output value of the G sensor may not be obtained. For this reason, the road gradient calculated based on the output value of the G sensor is a value delayed from the actual road gradient, and there is a problem that its responsiveness and its accuracy are not sufficient.

The present invention has been made in view of such a problem, and provides a road gradient detecting device capable of detecting an accurate road gradient without delay with respect to an actual road gradient change. The purpose is to:

[0007]

According to a first aspect of the present invention, there is provided a road slope detecting apparatus according to the present invention, wherein a G sensor is disposed on an axle of a vehicle to detect a rotation speed of a drive system of the vehicle. The road gradient is detected based on the vehicle acceleration calculated based on the vehicle acceleration and the output value of the G sensor, so that it is delayed from the actual road gradient change without being affected by changes in vehicle weight or suspension deflection due to road gradient or the like. It is possible to detect the following road gradient without the need.

Further, in the road gradient detecting apparatus according to the present invention, when the variation of the road gradient calculated by the road gradient detecting means is equal to or more than a predetermined value, the calculated value of the road gradient is set to the value before the change. Until the vehicle returns to the state, the road surface gradient calculation value before the change is maintained, so even if the vehicle is in a running state in which the output value accuracy of the G sensor is reduced due to disturbance from the road surface or the like, the G sensor The road gradient calculated based on the output value is not used as the road gradient, but a highly reliable road gradient before the change is employed. By removing the abnormal road gradient value generated by the above, an accurate road gradient can be detected.

According to a third aspect of the present invention, when the amount of change in the road surface gradient calculated by the road surface gradient detecting means is equal to or greater than a predetermined value, the calculated value of the road surface gradient value before the change for a predetermined period of time. In order to keep the road gradient, the road gradient calculated based on the output value of the G sensor is not used as the road gradient due to the disturbance from the road surface or the like, and a highly reliable road gradient before the change is adopted. By doing so, it is possible to detect an accurate road surface gradient without delaying the actual road gradient change and removing an abnormal road surface gradient value generated by disturbance.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
The road surface gradient detecting device according to the embodiment will be described. 1 is an overall configuration diagram schematically showing the overall configuration of the present invention, and FIG. 2 is a rear view of the vehicle in FIG. In the present embodiment, a case will be described in which the road surface gradient detecting device is applied to a large truck, particularly a rear two-axle vehicle.

As shown in FIGS. 1 and 2, the vehicle has a G sensor 1 for detecting the longitudinal acceleration of the vehicle on an axle 3 at the rear rear axle to detect the rotational speed of the drive system of the vehicle. Wheel speed sensors 5 functioning as sensors are provided, respectively, and detect the rotation speed of the wheels 15. Information from these sensor outputs is taken into a control unit 7 (hereinafter, referred to as ECU) that functions as a road surface gradient detecting device.

The axle 3 is suspended by a suspension 13 on a frame 11 supporting a rear body 9, and the G sensor 1 is disposed on the axle 3.
The wheel speed sensor 5 is provided at the end of the axle 3 to detect the number of revolutions of a drive shaft or wheels 15 (not shown) and supply information to the ECU 7, and is generally used for an antilock brake system (ABS). It has the same configuration as that used in general.

Here, instead of the wheel speed sensor 5,
As a rotation speed sensor that detects the rotation speed of the drive system of the vehicle,
A vehicle speed sensor that detects the vehicle speed from the output rotation speed of a transmission (not shown) may be used, and is particularly suitable when the present invention is applied to a vehicle without an ABS.
Next, the ECU 7 of the present invention will be described with reference to FIG.

The ECU receives a wheel speed signal Wl, which is a detection value of the wheel speed sensor 5, and a G sensor signal G, which is a detection value of the G sensor 1. The wheel speed signal Wl is time-differentiated by the acceleration calculating means 21 according to the following equation (1) to calculate the vehicle acceleration αv.

[0015]

(Equation 1)
Equation (1)

Thereafter, the gradient detecting means 23 calculates a gradient obtained by dividing by the gravitational acceleration g based on the difference between the G sensor signal αs and the vehicle acceleration αv. Here, the following formula (2), which is a known method, is generally used as a gradient calculation method. sin θ = (αs−αv) / g Equation (2) Also, the road gradient is generally represented by tan θ, but the gradient at which the vehicle can travel is up to about 10%. Since ≒ sin θ, in the present invention, the value of sin θ is directly used as the road surface gradient value i.

Next, the gradient change monitoring means 25 calculates the time derivative of the road surface gradient value i as the time differential value i of the road surface gradient value i.
t is calculated, and when the time derivative it is equal to or larger than a predetermined value (for example, 7% in the present invention), an instruction to hold the road surface gradient value i is issued. When the time derivative it of the road surface gradient value i is smaller than a predetermined value, the non-holding of the road surface gradient value i is instructed. The time derivative it of the road surface gradient value i is calculated by the following equation (3).

[0018]

(Equation 2)
Equation (3)

That is, when the road surface gradient value i indicates a change that cannot be considered as an actual change in the road surface gradient, an instruction to hold the road surface gradient value i is issued. Therefore, as the above-mentioned predetermined value, a change rate which is not considered as an actual change of the road surface gradient is set in advance by experiments or the like, and the value is stored in the ECU. Further, in the present invention, the predetermined value is set to 7% as described above. However, since the present invention is a road surface gradient detecting device for a large truck, the value determined in advance by experiment is a road surface gradient on which the large truck actually travels. Since the range of the road surface gradient on which the vehicle travels varies depending on other vehicles, a value suitable for the vehicle may be stored in the ECU.

When the gradient change monitoring means 25 instructs to output the road surface gradient value i, the gradient value switching unit 27 outputs the road surface gradient value i calculated by the gradient calculation unit 23 as it is, and outputs the output road surface gradient value i. i is stored. on the other hand,
When the gradient change monitoring unit 25 instructs to hold the road surface gradient value, that is, instructs to output the stored value I, the gradient value switching unit 27
Outputs the stored road surface gradient value i without outputting the value calculated by the gradient detecting means 23.

Therefore, the road surface gradient detecting device of the present invention is provided with the G sensor 1 on the axle 3 suspended under the suspension 13 so as to be affected by the flexure of the suspension due to a change in vehicle weight. And a G sensor output value that follows a change in road gradient can be obtained. On the other hand, even when the G sensor is disposed on an axle under a suspension that is easily affected by road surface disturbance, it cannot be actually caused by disturbance. When a road surface gradient value having a road surface gradient change is calculated, the immediately preceding normal value stored is used without using the road surface gradient value.
A highly reliable road gradient can be detected.

Next, the functions of the gradient change monitoring means 25 and the gradient value switching means 27 of the road surface gradient detecting device of the present invention will be described with reference to the flowchart of FIG. First, in this flowchart, the gradient change monitoring means 25 determines in step S1
01 to step S105, and the gradient value switching means performs steps S201 to S208.

In step S101, the gradient calculating means 23
The road surface gradient value i calculated in step S10 is fetched, and step S10
Based on the road surface gradient value i fetched in 2, the road surface gradient value change rate it which is a time derivative thereof is calculated. It should be noted that the road surface gradient change rate it is determined based on the above equation (3). In step S103, it is determined whether the road surface gradient change rate it calculated in step S102 is equal to or greater than a predetermined value K (for example, 7%). When the road surface gradient change rate it is equal to or greater than the predetermined value K, an output instruction is issued to output the stored value I stored in the gradient value switching means 27. On the other hand, when the road surface gradient change rate it is smaller than the predetermined value K, the road surface gradient value i is
Is instructed to output as it is.

Next, at step S201, the flag F
It is determined whether or not is standing. Here, the flag F is used without actually using the gradient value calculated by the gradient detecting means 23.
Step S2 when the stored value I is output as the road surface gradient value
It will be launched at 05. In the initial state, the flag F is 0. When the flag F is 0, that is, when the gradient value calculated by the gradient calculating unit 23 is continuously output as the road surface gradient value, the process proceeds to step S202. In step S202, it is determined whether or not the gradient change monitoring unit 25 outputs the road surface gradient value i calculated by the gradient calculation unit 23. When the output of the road surface gradient value i is instructed, the road surface gradient value i is output in step S203, and the process proceeds to step S203.
At 204, the road surface gradient value i is stored as the storage value I, and a series of detection flow of road surface gradient detection is ended.

If the gradient change monitoring means 25 does not output the road surface gradient value i in step S202, that is, if the storage value I is instructed to be output, the flag F is set to 1 in step S205. In step S206, the stored value I stored in the gradient switching means 27 is output as the road surface gradient value i. This stored value I is updated in step S204.

On the other hand, when the flag F is 1 in step S201, that is, in step S202, the gradient change monitoring means 25
Determines that the stored value I is instructed to be output, and
Is output as the road surface gradient value i, the road surface gradient value i detected by the gradient calculation unit 23 in step S207.
Is a stored value I. Here, when it is determined that the road surface gradient value i is the stored value I, it is determined that the value of the G sensor value αs has returned to the normal value, and that the road surface gradient value i has also returned to the normal value. Is returned to 1, the road surface gradient value i is output in step S203, and the road surface gradient value i is stored as the storage value I.

If it is determined in step S207 that the road surface gradient value i is not the stored value I, the stored value I stored in the gradient switching means 27 is output as the road surface gradient value i in step S206. According to the road surface gradient detecting device of the present invention described with reference to the above-described flowchart, the effects as shown in FIG. 5 are obtained. FIG. 5 shows the detection of the road surface gradient value i at the time of shifting when traveling uphill. Since the driving force changes suddenly during shifting, an abnormal value where the value of the G sensor value αs cannot be in a normal state until the shifting is completed and a stable acceleration state is detected. If the detected road surface gradient value i detects an abnormal value and the rate of change it is equal to or greater than a predetermined value (point A in the figure), the gradient value switching means 27
Is output as the road surface gradient value i (thick line in the figure), which is more reliable than the road surface gradient i (thin line in the figure) that is used as it is. The gradient can be detected.

When the road surface gradient value i becomes equal to the stored value I (point B in the figure), it is determined that the road surface gradient value is normal, and the use of the stored value I is terminated. It is possible to obtain the road surface gradient value i that follows the change in the road gradient. Next, a second embodiment of the present invention will be described with reference to the flowchart of FIG. Since the second embodiment is the same as the first embodiment except for the gradient switching means 27, the control steps already described in the first embodiment (FIG. 4) have the same reference numerals. And the description is omitted.

In step S202, the gradient change monitoring means 25
Outputs the stored value I without outputting the road surface gradient i,
In step S205, the flag F is set to 1 and in step S2
At 09, the timer is turned on. Then, after the timer is turned on, the flag F is 1, so that YES is determined in the step S201, and it is determined whether or not the timer elapsed time t has elapsed in a step S210. If the time t has elapsed,
In step S211, the timer is turned off, and
At 203, the road surface gradient is output. On the other hand, step S210
If the timer has not passed the time t, the process proceeds to step S
At 206, the stored value I is output as the road surface gradient value i.

As a result, the G sensor value α
When s becomes inaccurate and the gradient change monitoring unit 25 determines that the road surface gradient value i calculated by the gradient calculation unit 23 has changed unpredictably, the time t at which the disturbance will be improved is determined. During that time, the stored value I is output as the road surface gradient value i, so that an accurate road surface gradient can be detected without delay in the change of the road surface gradient.

Next, an example that embodies the present embodiment and its effects will be described. FIG. 7 illustrates detection of a road surface gradient value i when the vehicle passes through a place having a road surface step such as a drainage ditch. Even when the vehicle passes through a road surface step such as a drain ditch, the G sensor value αs detects an abnormal value that cannot be considered in a normal state, and the road surface gradient value i calculated by the gradient calculating means 23 is abnormal. Values may be detected. When the rate of change it is equal to or greater than a predetermined value (C in FIG.
Point), and outputs the reliable stored value gradient I stored in the gradient value switching means 27 as the road surface gradient value i (thick line in the figure).
Thus, a more reliable road surface gradient can be detected as compared with the case where the road surface gradient i (the thin line in the figure) is used as it is.

When the elapsed time t has elapsed since the stored value I was output as the road surface gradient value i (in the figure,
At point D), it is estimated that the road surface gradient value will have returned to normal, and the use of the stored value I is terminated, so that the road surface gradient value i that follows the change in the road gradient can be obtained. In particular,
Disturbance due to such a road surface step rarely elapses for a long time, and setting the stored value I to the road surface gradient value i during the timer elapsed time t can be performed by a simple method, which is effective in the system.

Next, a third embodiment of the present invention will be described with reference to FIGS. The same reference numerals are given to the components already described, and the description is omitted. In the present embodiment, a curve traveling is specified as a traveling state in which it is expected that the output of the G sensor 1 cannot detect an accurate value. Since the G sensor can only measure G in the front-rear direction of the vehicle, it is known that the value of the G sensor outputs a value different from the actual G due to the centrifugal force when the vehicle turns, such as when traveling on a curve.

When the curve detecting means 31 determines that the vehicle is traveling on a curve based on the information input from the camera 59, a signal indicating that the vehicle is traveling on a curve is output to the gradient value switching means 27. Then, in the gradient value switching means 27,
When a signal is input while the vehicle is traveling on a curve, the stored storage value I is used instead of the road surface gradient value i calculated by the gradient calculation means 23 based on the G sensor value αs which is the output value of the G sensor 1. It is output as the road surface gradient value i.

Next, the flow of the switching of the road surface gradient value by the gradient value switching means 23 will be described with reference to the flowchart of FIG. First, in step S301, the curve information from the curve detecting means 31 and the road surface gradient value i calculated by the gradient calculating means are fetched. Step S302
Then, it is determined whether or not the vehicle is traveling on a curve based on the acquired information. When it is determined that the vehicle is traveling on a curve, the process proceeds to step S302, and the stored stored value I is output as the road surface gradient value i. On the other hand, when it is determined in step S302 that the vehicle is not running on a curve,
The road surface gradient value i calculated by the gradient calculation means 23 is output as the road surface gradient value i. Then, in step S305, the road surface gradient value i output at this time is stored as a new storage value I.

Thus, the stored value I used during the curve running is the road surface gradient value i immediately before it is determined that the vehicle is running on the curve.
Is stored, and a more accurate road surface gradient value i can be output even during a curve running. still,
In the present embodiment, the camera 59 is used as a means for inputting curve information. However, the present invention is not limited to this, and information from a steering angle sensor or a navigation system may be used.

As described above, according to each embodiment of the present invention, the G sensor 1 is
Even if the response of the output value of the sensor 1 is improved and the output of the G sensor 1 is different from the actual value due to the arrangement of the G sensor 1 on the axle 3, , An accurate road gradient value can be supplied using the immediately preceding normal value.

By supplying such a responsive and accurate road surface gradient value, it can be widely used for engine control, transmission control, braking control and the like.

[0039]

As described above in detail, in the road surface gradient detecting device according to the first aspect of the present invention, a G sensor is disposed on the axle of the vehicle, and the rotational speed sensor detects the rotational speed of the drive system of the vehicle. The road gradient is detected based on the vehicle acceleration calculated based on the vehicle acceleration and the output value of the G sensor, so that it is delayed from the actual road gradient change without being affected by changes in vehicle weight or suspension deflection due to road gradient or the like. It is possible to detect the following road gradient without the need.

According to the second aspect of the present invention, when the amount of change in the road surface gradient calculated by the road surface gradient detecting means is equal to or more than a predetermined value, the calculated value of the road surface gradient is changed to the value before the change. Until the vehicle returns to the state, the road surface gradient calculation value before the change is maintained, so even if the vehicle is in a running state in which the output value accuracy of the G sensor is reduced due to disturbance from the road surface or the like, the G sensor By adopting a highly reliable road surface gradient before the change without using the road surface gradient calculated based on the output value, there is no delay with respect to the actual road gradient change and abnormalities caused by disturbance It is possible to detect an accurate road surface gradient by removing an unnecessary road surface gradient value.

According to the third aspect of the present invention, when the amount of change in the road surface gradient calculated by the road surface gradient detecting means is equal to or more than a predetermined value, the calculated value of the road surface gradient value before the change for a predetermined period of time is obtained. In order to continue to hold, by receiving a disturbance from a road surface or the like, instead of using the road surface gradient calculated based on the G sensor output value, by adopting a highly reliable road surface gradient before the change, An accurate road surface gradient can be detected without delay with respect to an actual road gradient change and by removing an abnormal road surface gradient value generated by disturbance.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing a configuration of a road surface gradient detecting device according to each embodiment of the present invention.

FIG. 2 is a conceptual diagram showing an arrangement of a G sensor according to the present invention.

FIG. 3 is a schematic functional block diagram illustrating a main configuration of a road surface gradient detecting device according to the first embodiment of the present invention.

FIG. 4 is a flowchart for explaining the operation of the road surface gradient detecting device according to the first embodiment of the present invention.

FIG. 5 is a time chart showing an effect of the road surface gradient detecting device according to the first embodiment of the present invention.

FIG. 6 is a flowchart for explaining the operation of the road surface gradient detecting device according to the second embodiment of the present invention.

FIG. 7 is a time chart showing an effect of the road surface gradient detecting device according to the second embodiment of the present invention.

FIG. 8 is a schematic functional block diagram illustrating a main configuration of a road surface gradient detecting device according to a third embodiment of the present invention.

FIG. 9 is a flowchart for explaining the operation of the road surface gradient detecting device according to the third embodiment of the present invention.

[Description of Signs] 1 G sensor 5 Rotation speed sensor (wheel speed sensor) 7 Road surface gradient detection device (ECU)

Claims (3)

[Claims] 1. A G sensor disposed on an axle of a vehicle, a rotation speed sensor for detecting a rotation speed of a drive system of the vehicle, and a vehicle acceleration calculated based on an output of the rotation speed sensor. A road surface gradient detecting device comprising: road surface gradient detecting means for detecting a road surface gradient based on a difference between an acceleration and an output value of the G sensor. 2. The method according to claim 1, wherein when the calculated amount of change in the road surface gradient is equal to or more than a predetermined value, the road surface gradient detection means returns the calculated value of the road surface gradient to a value before the change.
Characterized by continuing to maintain the road surface gradient value before the change,
The road surface gradient detecting device according to claim 1. 3. The road surface gradient detecting means according to claim 3, wherein when the calculated amount of change in the road surface gradient is equal to or more than a predetermined value, the road surface gradient value is maintained for a predetermined time. The road surface gradient detecting device according to claim 1.