JP2002081940A - Travel azimuth detector for vehicles - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly detect the travel azimuth, based on right and left wheel speeds even during slow running of a vehicle. SOLUTION: The travel azimuth detector for detecting the travel azimuth, based on the difference between the numbers of revolution of right and left wheels, comprises means (steps S4, S5, S9) for obtaining the travel azimuth, based on the number of rotation difference when the numbers of rotation of the wheels exceed specified values in a low vehicle speed condition below a specified vehicle speed.

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 traveling direction of a vehicle based on left and right wheel speeds.

[0002]

2. Description of the Related Art An example of this type of apparatus is disclosed in Japanese Patent Laid-Open No. 5-264.
No. 285. The device described in this publication calculates the rotation of the vehicle (change in heading) based on the difference between the number of pulse signal outputs from the left and right wheel speed sensors, and obtains the calculation result and the heading and geomagnetic sensors immediately before. It is configured to estimate the traveling direction by integrating the obtained direction. As the wheel speed sensor, for example, a sensor configured to count a pulse signal generated in an electromagnetic pickup arranged near the outer periphery of the pulse gear is used. However, such a sensor is relatively inexpensive, but is used at lower vehicle speeds. There is a characteristic that the error increases.

As described in the above-mentioned publication, when the traveling direction is detected from the wheel speed, the left and right wheel speeds are detected. Due to differences in the characteristics of
The detection error of the left and right wheel speeds at the time of low vehicle speed increases, which may increase the detection error of the traveling direction. Therefore, in the invention described in the above publication, in order to avoid such an estimation error of the traveling direction, at low vehicle speed, instead of using the wheel speed,
The traveling azimuth is estimated using the absolute azimuth detecting means.

[0004]

However, in addition to detecting the traveling direction using the wheel speed sensor and estimating the traveling direction using the absolute direction detecting means,
Two types of sensors or devices are required for detecting or estimating the traveling direction, which may hinder a reduction in vehicle cost.

The present invention has been made in view of the above technical problem, and has as its object to provide an apparatus capable of accurately detecting or estimating the traveling direction based on the wheel speed regardless of the vehicle speed. It is assumed that.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for detecting the right and left wheel speeds, that is, the rotational speed, after an unavoidable error caused by detecting the wheel speed has become relatively small. , The traveling azimuth of the vehicle is detected based on the rotational speed difference between the left and right wheels. More specifically, the invention of claim 1
In a traveling azimuth detecting device for detecting a traveling azimuth based on a rotation speed difference between left and right wheels for each predetermined period, in a low vehicle speed state equal to or lower than a predetermined vehicle speed, when the rotation speed of the wheel becomes equal to or higher than a predetermined value. An apparatus comprising means for obtaining a traveling direction based on a rotation speed difference.

Therefore, according to the first aspect of the present invention, when the vehicle turns, a difference occurs between the rotation speeds of the left and right wheels (cumulative rotation speeds within a predetermined period), that is, the rotation speed of the inner wheel in the turning direction is increased. , The change in the heading direction of the vehicle is detected based on the difference between the rotation speeds. The rotation speeds of the left and right wheels used for detecting the traveling azimuth in this manner are rotation speeds during a predetermined period, but in the case of low vehicle speed, the rotation speeds within the predetermined period are reduced. In that case, in that case, the traveling azimuth is obtained after the number of revolutions is accumulated to a predetermined value or more. As a result, the rotation number detection error is relatively reduced, and the traveling azimuth detection accuracy is improved.

According to a second aspect of the present invention, there is provided a traveling azimuth detecting apparatus for detecting a traveling azimuth based on a rotational speed difference between left and right wheels for each predetermined period, wherein the predetermined vehicle speed is less than a predetermined vehicle speed. The apparatus further comprises means for obtaining a traveling direction based on the rotation speed difference detected by extending the predetermined period from a higher vehicle speed state.

Therefore, according to the second aspect of the present invention, when the vehicle turns, a difference occurs in the rotation speeds of the left and right wheels (cumulative rotation speeds within a predetermined period), that is, the rotation speed of the inner wheel in the turning direction increases. , The change in the heading direction of the vehicle is detected based on the difference between the rotation speeds. The rotation speeds of the left and right wheels used for detecting the traveling azimuth in this manner are rotation speeds during a predetermined period, but in the case of low vehicle speed, the rotation speeds within the predetermined period are reduced. In this case, the predetermined period for accumulating the number of revolutions used for obtaining the traveling direction is longer than in the case of the high vehicle speed. Therefore, the accumulated rotation speed for obtaining the traveling azimuth increases, so that the detection error of the rotation speed relatively decreases, and the detection accuracy of the traveling azimuth improves.

According to a third aspect of the present invention, in the first or the second aspect of the present invention, when the rotational speed difference occurs and the rotational speed difference is equal to or less than a predetermined value, the vehicle goes straight. The device further comprises means for determining that there is a device.

According to the third aspect of the present invention, even if there is a difference between the rotational speeds of the left and right wheels, if the rotational speed difference is equal to or less than a predetermined value, the traveling direction of the vehicle is not changed and the vehicle is traveling straight. Judge. That is, since a difference in the rotational speeds of the left and right wheels due to abrasion of the left and right wheels or an air pressure or an error in mounting the sensor is not taken in, erroneous detection of the traveling direction is prevented.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described based on a specific example shown in the drawings. First, a vehicle 1 to which the present invention can be applied will be described. The example shown in FIG. 3 is a rear-wheel drive vehicle, in which a prime mover 2 such as an engine is mounted on a front side and its power is transmitted to a transmission 3. The transmission is transmitted to the rear wheel 4 via the rear wheel 4. The front wheel 5 has a steering mechanism 6.
Are connected. The vehicle 1 is equipped with an antilock brake system (ABS) 7. The ABS 7 is a conventionally known device that increases or decreases the braking force so that the wheels 4 and 5 do not lock during braking, and is a rotation speed sensor 8 and 9 for detecting the rotation speed of each wheel 4 and 5. And a hydraulic mechanism (not shown) for adjusting the braking force of each wheel 4, 5. The rotation speed sensors 8 and 9 are configured to output a pulse signal accompanying the rotation of the wheels 4 and 5 by the above-described electromagnetic pickup, and to detect the rotation speed by counting the pulse signals.

Further, the vehicle 1 is provided with a navigation system 10 for detecting the position of the host vehicle, the planned road to the destination or the road conditions. The navigation system 10 uses a GPS (global positioning system), a geomagnetic sensor or autonomous navigation using wheel speeds to indicate the position of the vehicle on an electronic map and guide the vehicle to a destination. And various road traffic information systems that obtain various types of road information including traffic congestion information and information on facilities from beacons and sign posts installed in the facilities.

More specifically, as shown in FIG. 4, the navigation system 10 includes a player having an information recording medium 11 such as an optical disk or a magnetic disk loaded therein and reading information stored in the information recording medium 11. And a display unit 13 for displaying information read by the player 12 in a two-dimensional or three-dimensional image. Further, the navigation system 10 includes a first position detection unit 1 for detecting a current position of the vehicle and a road condition.
4 and a second position detector 15 and a speaker 16 for informing the driver of the road condition by voice. The display unit 13 includes a liquid crystal display provided on the side of an instrument panel or a glove box in the room,
In addition to RT and the like, it is possible to use an image projection unit or the like provided at a location that does not affect the field of view of the front window.

The player 12, the display unit 13, the first position detection unit 14, and the second position detection unit 15
And the speaker 16 are controlled by the electronic control device 17. The electronic control unit 17 includes a central processing unit (C
PU), storage devices (RAM, ROM), and a microcomputer mainly including an input / output interface.

The information recording medium 11 stores information necessary for the vehicle to travel, such as maps, place names, roads, and main buildings around the roads, as well as specific conditions of the roads, such as straight roads and roads. Curves or corners, uphill or downhill, and their respective slopes, general roads, highways,
Unpaved roads, gravel roads, deserts, riverbeds, forest roads, agricultural roads, low friction coefficient roads, and the like are stored.

The first position detector 14 includes a geomagnetic sensor 18 for detecting the direction in which the vehicle is traveling, and a vehicle speed sensor 1.
9, a steering sensor 20 for detecting a steering angle of a steering wheel, a distance sensor 21 for detecting a distance between a vehicle and surrounding objects, an acceleration sensor 22, and the like.
Further, the second position detection unit 15 includes a GPS antenna 24 for receiving a radio wave from the artificial satellite 23 and a GPS antenna 2
4 and an GPS receiver 26 connected to the amplifier 25.

The second position detecting unit 15 is installed on a roadside, at a traffic light, at a road surface at an intersection, and the like, and is provided with a ground detection system for detecting and transmitting an object, a beacon or signpost for outputting road information, a VICS, (Registered trademark) (Vehicle Information & Communication System), SSVS (Super Smart Vehicle System) and other ground-based information transmission systems 2
An antenna 28 for receiving a radio wave transmitted from the antenna 7, an amplifier 29 connected to the antenna 28, and a ground information receiver 30 connected to the amplifier 29.

The first position detecting unit 14 and the second position detecting unit 15 detect the current position and prevent driving on existing roads, such as traffic jams, broken vehicles, under construction, snowfall, landslides, and flooding of rivers. It is possible to detect road closures, falling rocks, fallen trees, vehicles stopped at intersections, and the presence of people and animals.

The above-described vehicle control device operates in an ASV (Advanced Safety Vehicle) function, for example, by vibrating a seat when the vehicle approaches an object in the vicinity, in order to improve safety during traveling. It is also possible to add a function of notifying a person or a function of deploying an airbag when the vehicle comes into contact with a surrounding object.

The ABS 7 and the navigation system 10 are connected so as to be able to perform data communication. For example, the rotation speeds detected by the rotation speed sensors 8 and 9 input to the ABS 7 are used for the navigation system 10.
Has been transmitted to. And the navigation system 1
0 is configured to detect the traveling direction based on the input rotation speed difference between the left and right wheels in addition to the detection of the position and traveling direction of the vehicle by the GPS.

FIG. 1 is a flow chart for explaining a routine for detecting the traveling direction based on the difference in the number of rotations of the wheels, that is, an example of a detection routine executed by the apparatus of the present invention. The routine shown in FIG. 1 is configured to be executed every predetermined time ΔT seconds. First, the rotational speed of the front wheel 5 which is a non-driven wheel is detected (step S1). Specifically, the pulse signal Pr output from the rotation speed sensor 9 for the right front wheel 5 and the pulse signal Pl output from the rotation speed sensor 9 for the left front wheel 5 are constantly counted. Read. Since the routine shown in FIG. 1 is executed every ΔT seconds, these count values Pr and Pl represent the cumulative number of rotations during the ΔT seconds.

Next, it is determined whether the vehicle is turning left (step S2). That is, it is determined whether or not the pulse number Pl for the left front wheel is smaller than the pulse number Pr for the right front wheel. When making a left turn, the number of pulses is compared since the left wheel becomes an inner wheel and its rotation speed (cumulative rotation speed) becomes smaller than that of the right wheel which becomes an outer wheel. If an affirmative determination is made in step S2, it is determined whether the difference (Pr-Pl) is greater than a predetermined reference value Xl (step S3). The reference value Xl is a small integer of about "1", and is used to determine whether or not the rotational speed difference between the left and right wheels is caused by an error in mounting the sensors 8 and 9 or a difference in diameter. is there.

Therefore, if the difference between the rotational speeds of the left and right wheels is equal to or greater than the reference value Xl, and the determination in step S3 is affirmative, the vehicle 1 is turning left. In that case, it is determined whether the pulse number Pl for the left front wheel is greater than a predetermined reference value Yl (step S1).
4). This step S4 is a determination step for minimizing the influence of an unavoidable detection error, and detects the rotational speeds of the wheels 4 and 5 in the low rotational speed (low vehicle speed) state as described above. In this case, the influence of the unavoidable error relatively increases, so that it is determined in step S4 that the vehicle is not in the low vehicle speed state. That is, since the number of pulses output in ΔT seconds increases in proportion to the vehicle speed, if the pulse number Pl for the left wheel is smaller than the reference value Yl, the vehicle is running at a low vehicle speed.

Therefore, when the vehicle speed is low and a negative determination is made in step S4, the routine returns without performing any particular control, and the counting of the pulse signal for each wheel is continued. If the determination in step S4 in the next cycle or a subsequent cycle is affirmative, the traveling azimuth is obtained based on the detected rotational speeds of the left and right wheels (cumulative rotational speed or wheel speed) ( Step S5).

An example of the calculation will be described with reference to FIG. 2. If the number of pulses corresponding to the number of rotations of the inner wheel at the time of calculating the heading is Pl and the number of pulses corresponding to the number of rotations of the outer wheel is Pr. For example, the travel distance Lin of the inner wheel and the travel distance Lo of the outer wheel
ut is determined by multiplying the distance per pulse by the number of each pulse. And the rear wheel 4
The turning radius is R, the tread width is K, and the wheelbase is L
Then, the turning radius Rin of the inner front wheel and the turning radius Rout of the outer front wheel are

(Equation 1) Becomes Therefore, the turning angle θ (rad) is

(Equation 2) Becomes here,

(Equation 3) By solving for the turning radius R of the rear wheel 4,

(Equation 4) Becomes By substituting the turning radius R of the rear wheel 4 into the above equation 2, the turning angle θ can be obtained. Then, a new traveling azimuth is obtained by adding or subtracting the turning angle θ to or from the azimuth that has traveled so far.

After the traveling azimuth is obtained as described above, the count values of the pulse signals for the left and right front wheels 5 are reset (step S6), and the routine returns.

If there is a difference between the rotational speeds of the left and right front wheels 5, but the rotational speed difference is smaller than the reference value Xl, and the determination in step S3 is negative, the rotational speed difference is determined. It is based on the diameter difference of the wheels 9 and the like,
The vehicle 1 is traveling straight, and therefore, in this case, the process proceeds to step S6, where the count value of the pulse signal is reset, and then the process returns.

Further, when the rotational speed of the front left wheel is equal to or higher than the rotational speed of the front right wheel, and the determination in step S2 is negative, the count number P1 of the pulse signal for the front left wheel is increased. Count number Pr of pulse signal
It is determined whether or not the value is greater than (step S7). That is, it is determined whether the vehicle is turning right. If a negative determination is made in step S7, the count values of the pulse signals for the left and right front wheels 5 are equal, and the vehicle 1 is traveling straight ahead. After resetting, return.

On the other hand, if a positive determination is made in step S7, it is determined whether the difference (Pl -Pr) is greater than a predetermined reference value Xr (step S7).
8). The reference value Xr is a small integer of about "1", and is used to determine whether or not the rotational speed difference between the left and right wheels is caused by an error in mounting the sensors 8, 9 or a difference in diameter. is there.

Therefore, if the difference between the rotational speeds of the left and right wheels is equal to or greater than the reference value Xr, and a positive determination is made in step S8, the vehicle 1 is turning right. In this case, it is determined whether the pulse number Pr for the right front wheel is greater than a predetermined reference value Yr (step S).
9). This step S9 is a determination step for minimizing the influence of an unavoidable detection error as much as the above-mentioned step S4, and the rotational speeds of the wheels 4 and 5 in the low rotational speed (low vehicle speed) state. Is detected, the influence of the unavoidable error relatively increases, so it is determined in step S9 that the vehicle is not in the low vehicle speed state. That is, since the number of pulses output in ΔT seconds increases in proportion to the vehicle speed, if the pulse number Pr for the right wheel is smaller than the reference value Yr, the vehicle is running at a low vehicle speed.

Therefore, when the vehicle speed is low and a negative determination is made in step S9, the routine returns without performing any particular control, and the counting of the pulse signal for each wheel is continued. Then, if the determination in step S9 in the next cycle or a subsequent cycle is affirmative, the traveling direction is obtained based on the detected rotational speeds of the left and right wheels (cumulative rotational speed or wheel speed) ( Step S6). The calculation is as described with reference to FIG.

As described above, the turning angle θ of the vehicle 1 can be obtained based on the difference between the rotation speeds of the left and right wheels (difference in the accumulated rotation speed or difference in running distance). In this case, if the actual speed of the left and right wheels is small due to the low vehicle speed, and the influence of the unavoidable error is relatively large, the detected left / right speed (the number of pulses in the above specific example) is equal to or greater than a predetermined value. After calculating the turning angle θ and obtaining the traveling direction, the traveling direction can be accurately obtained even at a low vehicle speed.

In steps S3 and S8, the difference between the rotational speeds of the left and right wheels is determined by the reference values Xl, X
If it is smaller than r, it is determined that the vehicle is traveling straight, so that it is possible to accurately detect the traveling direction by eliminating disturbance factors such as a difference in diameter between the left and right wheels. Therefore, for example, when it is received that an obstacle exists in front of the vehicle 1 and the vehicle subsequently deviates from the route for the obstacle, the route change, that is, the change in the heading direction, is accurately detected to avoid the obstacle. Nevertheless, it is possible to avoid a situation such as an alarm being issued in advance.

Further, in the above specific example, the existing ABS
Since the data obtained in step 7 is used, it is possible to implement with only new software without newly installing hardware such as sensors and actuators, so that an increase in the weight and cost of the vehicle 1 can be avoided or significantly suppressed. be able to. In the above specific example, the number of revolutions of the front wheel 5 which is a non-drive wheel is detected in order to eliminate the influence of the torque transmitted from the prime mover 2 and to perform accurate azimuth detection.

Here, the relationship between the above specific example and the present invention will be briefly described. The functional means of step S4 or step S9 and step S5 is the same as that of claim 1 except that "the low vehicle speed below a predetermined vehicle speed". In this state, it corresponds to "means for obtaining a traveling azimuth based on the rotational speed difference at the time when the rotational speed of the wheel has reached a predetermined value or more." The predetermined time Δ
During the T seconds, the count value of the pulse signal is set to a predetermined value Yl, Yr.
Is not reached, the count is continued without resetting the count value of the pulse signal, so that the predetermined period until the traveling azimuth is obtained is eventually extended. Therefore, the functional means of the above step S4 or step S9 and step S5 may detect that the predetermined period is longer than the high vehicle speed state higher than the predetermined vehicle speed in the low vehicle speed state below the predetermined vehicle speed. Means for determining the traveling direction based on the rotational speed difference. " Furthermore, the functional means of step S3 or step S8 determines that the vehicle is traveling straight when the rotational speed difference has occurred and the rotational speed difference is equal to or less than a predetermined value. Means ".

The present invention is not limited to the above specific example. For example, in the above specific example, each reference value X
Although the description has been made assuming that l, Xr, Yl, and Yr are fixed values, each of these reference values Xl, Xr, Yl, and Yr may be a variable according to the state of the vehicle such as the vehicle speed and acceleration, or by learning control. The value may be updated. Also,
The present invention can be applied to various vehicles such as FF vehicles and four-wheel drive vehicles in addition to so-called FR vehicles.

[0038]

As described above, according to the first aspect of the present invention, when the traveling direction is determined based on the rotational speeds of the left and right wheels (cumulative rotational speeds or wheel speeds within a predetermined period), a low vehicle speed is obtained. In this case, since the rotation speed within the predetermined period is small, the traveling azimuth is determined after the rotation speed is accumulated to a predetermined value or more. As a result, the detection error of the rotation speed relatively decreases, The detection accuracy of the traveling direction can be improved.

According to the second aspect of the present invention, the rotational speeds of the left and right wheels (cumulative rotational speeds or wheel speeds within a predetermined period)
When the traveling direction is obtained based on the following formula, since the number of revolutions within the predetermined period is small in the case of low vehicle speed, the predetermined period for accumulating the number of revolutions is lengthened to increase the number of revolutions used for obtaining the traveling direction. As a result, the detection error of the rotational speed is relatively reduced, and the detection accuracy of the traveling azimuth can be improved.

According to the third aspect of the present invention, even if there is a difference between the rotational speeds of the left and right wheels, if the rotational speed difference is equal to or less than a predetermined value, the traveling direction of the vehicle is not changed and the vehicle goes straight. It is possible to avoid taking in the difference in the rotational speed of the left and right wheels due to the diameter difference due to the wear and air pressure of the left and right wheels or the mounting error of the sensor, etc., or suppress the effect, and as a result, It is possible to prevent erroneous detection of the traveling azimuth or to detect the traveling azimuth with high accuracy.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining a control example by a control device of the present invention.

FIG. 2 is a diagram for explaining calculation of a traveling azimuth based on a rotational speed difference between left and right wheels.

FIG. 3 is a diagram schematically showing an example of a vehicle targeted by the present invention.

FIG. 4 is a control system diagram for explaining an example of the navigation device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vehicle, 4, 5 ... Wheel, 7 ... Anti-lock brake system, 8, 9 ... Rotation speed sensor, 10 ... Navigation system.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F029 AA02 AB01 AB07 AC02 AC13 AC18 AD01 5H180 AA01 BB13 CC12 FF04 FF05 FF13 FF22 FF25 FF32 FF38

Claims (3)

[Claims] 1. A traveling direction detecting device for a vehicle, which detects a traveling direction based on a rotation speed difference between left and right wheels for each predetermined period, wherein the rotation speed of the wheel is higher than a predetermined value in a low vehicle speed state below a predetermined vehicle speed. A traveling azimuth detecting device for a vehicle, comprising: means for obtaining a traveling azimuth based on the rotation speed difference at the time when the vehicle travels. 2. A traveling direction detection device for a vehicle, which detects a traveling direction based on a difference between the rotational speeds of right and left wheels at predetermined time intervals, wherein the low vehicle speed state below a predetermined vehicle speed is higher than the high vehicle speed state higher than the predetermined vehicle speed. A traveling azimuth detecting device for a vehicle, comprising: means for obtaining a traveling azimuth based on the rotation speed difference detected by extending a predetermined period. 3. The vehicle according to claim 2, further comprising: means for determining that the vehicle is traveling straight when the rotational speed difference has occurred and the rotational speed difference is equal to or less than a predetermined value. Item 3. The traveling direction detection device for a vehicle according to item 1 or 2.