JP2002039784A - Method and apparatus for measurement of moving body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position measuring apparatus by which the position of a moving body can be found on the basis of the orientation of the moving body and on the basis of the movement distance of a steering wheel without using a steering angle as far as possible. SOLUTION: The position measuring apparatus is provided with a judgment part 10-1 which judges whether the moving body is swiveled and moved and a position calculation and processing part 10-2. When the judgment part 10-1 judges that the moving body is not swiveled and moved the processing part 10-2 measures the position of the moving body by a dead reckoning operation while a front-steering-wheel movement amount, a front-steeringwheel steering angle, a rear-steering-wheel movement amount, a rear-steering-wheel steering angle, a posture-angle change amount and the wheel-base length of the moving body are used. When the judgment judges that the moving body is swiveled and moved, the slewing radius of a measuring point which is set on a wheel base is found by using the front-steering-wheel movement amount, the rear-steering-wheel movement amount, the posture-angle change amount and the wheel-base length while the moving body is swiveled and moved. The position of the moving body is measured on the basis of the movement amount during the swiveling motion calculated from the found slewing radius and the found posture-angle charge amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the position of a moving object such as an automatic guided vehicle.

[0002]

2. Description of the Related Art Automated guided vehicles (hereinafter referred to as "moving bodies") in AGV and AGF do not require fixed equipment such as rails on the ground and can be used as a main component of a transport system because they can share space with people and vehicles. I have been.

[0003] Conventionally, electromagnetic induction, magnetic induction, and optical reflection methods have been widely used as guidance methods for moving bodies. However, these methods use guide wire, magnetic tape,
Since the optical tape is installed on the running path, it cannot easily cope with layout changes. Further, the durability of the magnetic tape or the optical reflection tape attached to the floor is poor.

In addition to the above-described guidance system, the position of a moving body is measured by using an internal sensor attached to the moving body.
So-called dead reckoning is known.

With reference to FIG. 7, a description will be given of a typical dead reckoning navigation in the case of a moving body 60 having a front steered wheel 61 and a rear steered wheel 62. Of course, the moving body 60 includes the front steered wheels 61.
One or more fixed wheels (not shown) in addition to the rear steering wheel 62 and
Having. Here, the front and rear steering angles are the moving body 6
0 can be freely changed. In order to calculate the position of the moving body 60, the front steering angle and the moving distance of the front steered wheels 61, the rear steering angle and the moving distance of the rear steered wheels 62, and the direction of the moving body 60 are measured. As the measuring means, a pulse encoder provided in the drive unit of each steered wheel is used for measuring the front and rear steering angles and the moving distance of the front and rear steered wheels, and an internal field sensor such as a gyro sensor is used for measuring the direction of the moving body 60. It is common to do.

[0006] Here, the direction of the moving body 60 at a certain time is θ
Assuming that L, the front steering angle is α, and the moving speed of the front steered wheels 61 is VS, the moving speed VXS in the X direction and the moving speed VYS in the Y direction of the front steered wheels 61 can be obtained by the following equations.

VXS = VS × cos (θL + α) VYS = VS × sin (θL + α) The position (movement amount) of the front steered wheel 61 can be calculated by integrating these movement speeds. The position of the rear steered wheels 62 depends on the direction of the moving body 60 and the front steered wheels 61.
And the dimensions of the moving body 60, for example, the geometrical relationship using the wheel base L.

At this time, if the direction θL of the moving body 60, the front steering angle α, and the moving speed VS of the front steered wheels 61 can be correctly measured, no error occurs in the calculation result of the position of the moving body 60.

[0009]

However, in general, the measurement of the steering angle α is an unacceptable error due to an error due to backlash of a speed reducer included in the steering mechanism and an accurate zero adjustment of the steering angle. Often have. For this reason, a measurement error of the moving body position due to the steering angle measurement error occurs, which is a practical problem.

Accordingly, an object of the present invention is to provide a position measuring method and a measuring device which can determine the position of a moving object from the direction of the moving object and the moving distance of the steered wheels without using the steering angle as much as possible. It is in.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a method for measuring the position of a moving body having front and rear steered wheels in front and rear,
During the turning movement of the moving body, the amount of front steering wheel movement,
Using the post-steering wheel movement amount, the change amount of the posture angle of the moving body, and the length of the wheel base of the moving body, the turning radius of the measurement point set on the wheel base is obtained, and the obtained turning radius and the amount of change in the posture angle are obtained. The position of the moving object is measured based on the amount of movement during the turning movement calculated from.

According to the present invention, there is also provided a position measuring device for a moving body having front and rear steered wheels and rear steered wheels in front and rear, wherein a signal indicating a posture angle change amount of the moving body from a direction measuring means for measuring a direction of the moving body; Position calculation processing means for receiving a signal indicating the amount of movement of the front steered wheel from the front steered wheel mileage measuring means and a signal indicating the movement amount of the rear steered wheel from the rear steered wheel mileage measuring means; Means for moving a wheel base using the moving amount of the front steered wheels, the moving amount of the rear steered wheels, the change amount of the attitude angle, and the wheel base length of the moving body during the turning movement of the moving body. The turning radius of the measurement point set above is obtained, and the position of the moving object is measured based on the movement amount during the turning motion calculated from the obtained turning radius and the attitude angle change amount.

According to the present invention, it is also determined whether or not the moving body is making a turning movement. If it is determined that the moving body is not making a turning movement, the front steering wheel movement amount, the front steering wheel steering angle, The position of the moving body is measured by dead reckoning navigation using the rear steering wheel movement amount, the rear steering wheel steering angle, the change amount of the posture angle of the moving body, and the wheelbase length of the moving body, and it is determined that the vehicle is turning. In the case where the moving body is making a turning motion, the front steering wheel movement amount, the rear steering wheel movement amount, the posture angle change amount, and the wheel base length are used to adjust the position on the wheel base. Determining the turning radius of the set measurement point, and measuring the position of the moving object based on the amount of movement during the turning movement calculated from the obtained turning radius and the amount of change in the posture angle; A measurement method is provided.

In this position measuring method, the determination as to whether or not the moving body is making a turning motion is performed by comparing the amount of change in the attitude angle with a predetermined threshold value.

In this position measuring method, the position measurement when it is determined that the turning motion is performed includes the change in the posture angle in a short time, the moving amount of the front steered wheels, and the moving amount of the rear steered wheels. Calculating the turning radii of the front steered wheels and the rear steered wheels, and turning radii of the measurement points from the calculated turning radii of the front steered wheels, the turning radii of the rear steered wheels and the wheel base length. Calculating
From the calculated turning radius of the measurement point, the wheelbase length, the turning radius of the front steered wheel or the turning radius of the rear steered wheel, a line segment connecting the measuring point and the turning center and a line of the wheel base Calculating the angle C between the measurement point and the amount of movement of the measurement point in the x direction in a coordinate system set on the moving body from the turning radius of the measurement point and the amount of change in the attitude angle during the short time. Calculating the amount of movement in the y direction, and calculating the amount of movement in the x direction and the amount of movement in the y direction.
Correcting the rotation using the angle C to calculate the rotation-corrected x-direction movement amount and y-direction movement amount; and measuring the rotation-corrected x-direction movement amount and y-direction movement amount and the direction measurement. The amount of movement of the measurement point in the X direction in a coordinate system set on the ground from the direction of the moving object measured by the means, Y
Calculating the directional movement amount.

According to the present invention, further, a determination means for determining whether or not the moving body is making a turning movement, and a signal indicating a posture angle change amount of the moving body from a direction measuring means for measuring the direction of the moving body. A signal indicating the amount of movement of the front steered wheel from the front steered wheel mileage measuring means, a signal indicating the steering angle of the front steered wheel from the front steered wheel steering angle measuring means, and Position calculating means for receiving a signal indicating the amount of movement of the wheel and a signal indicating the steering angle of the rear steered wheel from the rear steered wheel steering angle measuring means; If it is determined that there is no front steering wheel movement amount, the front steering wheel steering angle, the rear steering wheel movement amount, the rear steering wheel steering angle, the attitude angle change amount, and the wheel base length of the moving body Of the moving object by dead reckoning navigation The measurement is performed, and when it is determined that the vehicle is turning, the front steering wheel movement amount, the rear steering wheel movement amount, the posture angle change amount, and the Using the wheelbase length, the turning radius of the measurement point set on the wheelbase is determined, and the position of the moving object is determined based on the amount of movement during the turning motion calculated from the determined turning radius and the amount of change in the attitude angle. Is provided, and a position measuring device for a mobile object is provided.

The determination means makes a determination by comparing the amount of change in the attitude angle with a predetermined threshold value.

The position measurement by the position calculation processing means when it is determined that the vehicle is making the turning motion is based on the amount of change in the attitude angle in a very short time, the amount of front steering wheel movement, and the amount of rear steering wheel movement. Calculating a turning radius of the front steering wheel and the rear steering wheel; and calculating a turning radius of the measurement point from the calculated turning radius of the front steering wheel, the turning radius of the rear steering wheel, and the wheel base length. And the calculated turning radius of the measurement point, the wheelbase length, the turning radius of the front steered wheels or the turning radius of the rear steered wheels, a line segment connecting the measuring point and the turning center and the Calculating an angle C between the line segment of the wheel base and the turning radius of the measurement point and the amount of change in the attitude angle in the short time, the coordinate point of the measurement point in a coordinate system set on a moving body. x direction movement amount, y Calculating a direction moving amount, x-direction movement amount calculated for y-direction movement amount,
Correcting the rotation using the angle C to calculate the rotation-corrected x-direction movement amount and the y-direction movement amount; and calculating the rotation-corrected x-direction movement amount and the y-direction movement amount and the moving object. Calculating the X-direction movement amount and the Y-direction movement amount of the measurement point in a coordinate system set on the ground from the orientation.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. Position measuring device 10 according to the present invention
Has a determination unit 10-1 and a position calculation processing unit 10-2,
The position calculation processing unit 10-2 performs the calculation of the position measurement by a different method according to the determination result of the determination unit 10-1. That is, the determination unit 10-1 determines whether the moving body is performing a turning motion, and determines the determination result as the position calculation processing unit 10-2.
Give to. If the result of the determination is that the vehicle is not turning, the position calculation processing unit 10-2 measures the position using the same measurement method as the dead reckoning described in the related art using signals from the following various sensors. On the other hand, when the determination result indicates that the vehicle is turning, the position calculation processing unit 10-2 performs position measurement by the method described below without using the signal indicating the steering angle among the signals from the following various sensors. Do.

A gyro sensor 21 is provided on the moving body to measure the direction of the moving body. A front steering wheel traveling distance encoder 22 for measuring a moving distance of the front steering wheel and a front steering wheel steering angle encoder 23 for measuring a steering angle of the front steering wheel are attached to the front steering wheel of the moving body. A rear steering wheel traveling distance encoder 24 for measuring the moving distance of the rear steering wheel and a rear steering wheel steering angle encoder 25 for measuring the steering angle of the rear steering wheel are attached to the rear steering wheel of the moving body.

The position measuring device 10 calculates the current position using the above-mentioned measurement data and the vehicle body data (for example, the wheel base L) of the moving body contained therein, and outputs the moving body position.

The moving body 30 shown in FIG. 2 performs a turning motion when the steering angle of the front steered wheels 31 and the steering angle of the rear steered wheels 32 are different.

In the determination section 10-1, the gyro sensor 21
The change amount .DELTA..theta. Of the posture angle within a very short time is measured based on the signal from the controller, and it is determined whether or not the turning motion is performed based on the measured change amount .DELTA..theta. In particular, when the change amount Δθ> the threshold value d, the determination unit 10-1 determines that the vehicle is in a turning motion, and outputs the fact to the position calculation processing unit 10-2. In this case, the position calculation processing unit 10-2 performs the position measurement without using the steering angle by the measurement method according to the present invention described below.

On the other hand, when Δθ ≦ threshold value d, the determination unit 10-1 determines that the vehicle is not making a turning motion (a state in which the vehicle is traveling without changing the posture), and the position calculation processing is performed. Output to the unit 10-2. In this case, the position calculation processing unit 10-2 performs the position measurement by the same measurement method as the dead reckoning described in the related art.

Next, a description will be given of a position measurement calculation method when the moving body is performing a turning motion. The turning motion of the moving body is a turning operation in which the intersection of the extension of the axle of the front steered wheel 31 and the extension of the axle of the rear steered wheel 32 is the turning center Pc. Here, the wheel base intermediate position of the moving object is defined as a measurement point (reference point) Ps on the position measurement, and the measurement point Ps
A method for determining the position of the position will be described.

Step 1: The turning radius Rf of the front steered wheel 31 and the turning of the rear steered wheel 32 from the change amount Δθ (radian) of the posture angle in a very short time, the moving distance of the front steered wheel 31 and the moving distance of the rear steered wheel 32. Radius Rb
Is calculated.

Rf = (movement distance ΔLf / of front steered wheel 31
Posture angle change amount Δθ) Rb = (movement distance of rear steering wheel 32 ΔLr / posture angle change amount Δθ) Step 2 The turning radius Rc from the turning center Pc to the measurement point Ps is obtained.

[0028] Rc = Because ^{[(Rf 2 + Rb 2)} / 2-L 2/4] 1/2 step 3 the orientation of the moving body is Δθ change, movement amount DerutaLc measurement point Ps is, ΔLc = Rc × Δθ.

Step 4 The angle C between the line segment of the wheel base and the line segment connecting the measurement point Ps and the turning center Pc is determined.

C = cos ⁻¹ [(Rc ² + (L / 2) ² −
Rf ² ) / (2 × Rc × L / 2)] Note that Rb can be used instead of Rf.

Step 5 The amount of movement of the measurement point Ps is obtained in the coordinate system on the moving body (FIG. 3). In FIG. 4, x moving amount ΔLcx = Rc × sin (Δθ) y moving amount ΔLcy = Rc × [1.0−cos (Δθ)] Note that these equations indicate that the turning center Pc is y in the coordinate system on the moving body. It is when it is on the axis.

Step 6 The rotation of the moving amount is corrected in consideration of the case where the turning center Pc is not on the y-axis.

The rotation correction amount γ can be calculated from the angle C.

The rotation correction processing is represented by the following equation (1).

[0035]

(Equation 1)

In the case of FIG. 5, x correction movement amount ΔLcx ′ = ΔLcx × cosγ + ΔLc
y × sinγ y correction movement amount ΔLcy ′ = − ΔLcx × sinγ + ΔL
cy × cosγ Step 7 The position of the measurement point Ps in the coordinate system fixed on the ground is obtained.

Referring to FIG. 6, if the direction of the moving body at a certain time in the X direction (same as the direction of a fixed wheel not shown) is θL, the moving amount in the ground coordinate system is obtained by the following equation. .

X-direction movement amount ΔXL = ΔLcx ′ × cos
θL−ΔLcy ′ × sin θL Y-direction movement amount ΔYL = ΔLcx ′ × sin θL + ΔLc
y ′ × cos θL Therefore, the position (XL, YL) of the measurement point Ps is obtained by integrating each of the movement amounts ΔXL and ΔYL.

In this example, the intermediate point of the wheel base is set as the measurement point Ps of the position. However, even when the measurement point Ps is set at another position, the position can be calculated in the same way.
Further, the present invention can be applied to position measurement for an unmanned guided vehicle, an unmanned forklift, and an unmanned tractor.

[0040]

Conventionally, since the steering angle is used for all position measurements, a position measurement error always occurs when the steering angle cannot be accurately measured. However, according to the present invention,
During the turning motion, it is not necessary to measure the steering angle in the position calculation processing of the moving body. Therefore, even when the steering angle cannot be accurately measured, the position of the moving body can be correctly estimated.

Further, since the measurement method is switched by automatically determining whether or not the vehicle is turning, the position measurement error due to the steering angle can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the relationship between a position measurement device according to the present invention and various sensors for position measurement.

FIG. 2 is a diagram for explaining calculation of an amount of movement of a measurement point on a moving body during a turning movement of the moving body.

FIG. 3 is a diagram illustrating a relationship between a coordinate axis and a measurement point when a coordinate system is set for a moving object;

FIG. 4 is a diagram for explaining calculation of a movement amount of a measurement point with respect to a posture angle change amount Δθ of a moving body in a coordinate system.

FIG. 5 is a diagram for describing rotation correction of a movement amount.

FIG. 6 is a diagram for explaining position measurement when a coordinate system is set on the ground.

FIG. 7 is a diagram for describing a case where position measurement is performed by conventional dead reckoning navigation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Position measuring device 10-1 Judgment part 10-2 Position calculation processing part 30, 60 Moving body 31, 61 Front steering wheel 32, 62 Rear steering wheel

Claims (8)

[Claims] 1. A method for measuring the position of a moving body having front and rear steered wheels and a rear steered wheel in front and back, comprising:
Using the post-steering wheel movement amount, the change amount of the posture angle of the moving body, and the length of the wheel base of the moving body, the turning radius of the measurement point set on the wheel base is obtained, and the obtained turning radius and the amount of change in the posture angle are obtained. A method for measuring the position of a moving object, comprising: measuring a position of the moving object based on a movement amount during a turning motion calculated from the moving object. 2. A position measuring device for a moving body having front and rear steered wheels and front and rear steered wheels, wherein a signal indicating an amount of change in the posture angle of the moving body from a direction measuring means for measuring a direction of the moving body; Position calculation processing means for receiving a signal indicating the amount of movement of the front steered wheels from the mileage measurement means and a signal indicating the movement amount of the rear steered wheels from the rear steering wheel mileage measurement means, During the turning movement of the moving body, the moving amount of the front steered wheels, the moving amount of the rear steered wheels,
Using the posture angle change amount and the wheel base length of the moving body, a turning radius of a measurement point set on the wheel base is obtained, and during the turning motion calculated from the obtained turning radius and the posture angle change amount. A position measuring device for a moving body, wherein the position of the moving body is measured based on a moving amount. 3. A method for measuring the position of a moving body having front and rear steered wheels before and after, determining whether or not the moving body is performing a turning movement. Is calculated by dead reckoning using the front steering wheel movement amount, the front steering wheel steering angle, the rear steering wheel movement amount, the rear steering wheel steering angle, the posture angle change amount of the moving body, and the wheel base length of the moving body. When it is determined that the vehicle is turning, the front steering wheel movement amount, the rear steering wheel movement amount, and the posture angle change amount during the turning movement of the moving body are determined. And the turning radius of the measurement point set on the wheel base using the wheel base length, and the moving body based on the moving amount during the turning motion calculated from the obtained turning radius and the attitude angle change amount. Measuring the position of a moving object Measurement method. 4. The method for measuring the position of a moving object according to claim 3, wherein the determination as to whether the moving object is performing a turning motion is performed by comparing the amount of change in the posture angle with a predetermined threshold value. A method for measuring the position of a moving object, characterized by being performed. 5. The position measurement method for a moving body according to claim 3, wherein the position measurement when it is determined that the vehicle is performing the turning motion includes the posture angle change amount in a short time, the front steered wheels. Amount of movement,
Calculating the turning radius of the front steering wheel and the rear steering wheel from the rear steering wheel movement amount; and calculating the turning radius of the front steering wheel, the turning radius of the rear steering wheel, and the wheel base length. Calculating a turning radius of the measurement point; turning the measurement point and the turning point from the calculated turning radius of the measurement point, the wheel base length, the turning radius of the front steered wheel or the turning radius of the rear steered wheel. Calculating an angle C between a line segment connecting the center and the line segment of the wheel base; and setting the angle C on the moving body from the turning radius of the measurement point and the amount of change in the posture angle in the short time. Calculating the x-direction movement amount and the y-direction movement amount of the measurement point in the coordinate system, and correcting the rotation using the angle C with respect to the calculated x-direction movement amount and the y-direction movement amount. X
Calculating a directional movement amount and a y-direction movement amount; and a coordinate system set on the ground from the rotation-corrected x-direction movement amount and the y-direction movement amount and the direction of the moving object measured by the direction measuring means. Calculating the amount of movement of the measurement point in the X direction and the amount of movement in the Y direction. 6. A position measuring device for a moving body having front and rear steered wheels and a rear steered wheel in front and back, a judging means for judging whether or not the moving body is turning, and a direction for measuring a direction of the moving body. The signal indicating the amount of change in the attitude of the moving body from the measuring means, the signal indicating the amount of movement of the front steered wheels from the front steered wheel traveling distance measuring means, and the steering angle of the front steered wheels from the front steered steering angle measuring means Position calculation processing means for receiving a signal indicating the amount of movement of the rear steered wheel from the rear steered wheel travel distance measuring means, and a signal indicating the steering angle of the rear steered wheel from the rear steered wheel steering angle measuring means. The position calculation processing means, when it is determined by the determination means not to make a turning motion, the front steering wheel movement amount, the front steering wheel steering angle, the rear steering wheel movement amount, the rear steering wheel steering angle. The amount of change in the attitude angle and the wheel of the moving body. Using the base length, the position of the moving body is measured by dead reckoning navigation, and when it is determined that the moving body is turning, the front steered wheel movement amount during the turning movement of the moving body, Using the post-steering wheel movement amount, the posture angle change amount, and the wheelbase length, a turning radius of a measurement point set on a wheel base is obtained, and the turning radius is calculated from the obtained turning radius and the posture angle change amount. A position measuring device for measuring a position of the moving body based on a moving amount during the turning motion. 7. The moving object position measuring apparatus according to claim 6, wherein the determination unit performs the determination by comparing the amount of change in the posture angle with a predetermined threshold value. Position measuring device. 8. The position measuring device for a moving object according to claim 6, wherein the position calculation by the position calculation processing means when it is determined that the turning motion is performed, comprises: changing the posture angle in a very short time. Amount, the amount of front steering wheel movement,
Calculating the turning radius of the front steering wheel and the rear steering wheel from the rear steering wheel movement amount; and calculating the turning radius of the front steering wheel, the turning radius of the rear steering wheel, and the wheel base length. Calculating a turning radius of the measurement point; turning the measurement point and the turning point from the calculated turning radius of the measurement point, the wheel base length, the turning radius of the front steered wheel or the turning radius of the rear steered wheel. Calculating an angle C between a line segment connecting the center and the line segment of the wheel base; and setting the angle C on the moving body from the turning radius of the measurement point and the amount of change in the posture angle in the short time. Calculating the x-direction movement amount and the y-direction movement amount of the measurement point in the coordinate system, and correcting the rotation using the angle C with respect to the calculated x-direction movement amount and the y-direction movement amount. X
Calculating the direction movement amount and the y direction movement amount; and moving the measurement point in the X direction in a coordinate system set on the ground based on the rotation corrected x direction movement amount and the y direction movement amount and the direction of the moving body. And a step of calculating the amount of movement in the Y direction.