JPH11271042A - Measuring apparatus for position of moving body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a measuring apparatus by which the position of a moving body is found on the basis of the direction of the moving body and on the basis of the movement distance of a steering wheel by a method wherein the direction and the swivel angular velocity of the moving body are measured, the movement speed of the steering wheel is measured and the position of the moving body is computed by using the measured values and by using the car body size of the moving body. SOLUTION: A position measuring apparatus is applied to a moving body in which the degree of freedom of the axle of a steering wheel is 1, e.g. to a moving body in which the steering axle of a steering wheel 21 is one axle or to a moving body in which steering axles of two steering wheels 31a, 31b are connected to a mechanism. In this case, an imaginary fixed wheel is assumed between two fixed wheels 22 or between the steering wheels 31a, 31b. Then, a gyro sensor 11 measures the direction and the swievel angular velocity of the moving body. A running-distance encoder 12 measures the movement distance and the movement speed of the steering wheel at the moving body. A position computing part 13 finds the position and the direction of the moving body on the basis of output data from the gyro sensor 11 and from the running-distance encoder 12 and on the basis of known moving-body size data which is stored in advance in a storage device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, automation has been advanced in the manufacturing industry, and an assembly part is mounted on an automatic guided vehicle (hereinafter, referred to as a moving body) on a production line and is automatically driven, and the assembly part has a desired purpose. An automatic transport system that transports to the ground is adopted. As a guidance method for a moving body in such an automatic transport system, a guidance method using a fixed traveling route such as an electromagnetic induction method or an optical guidance method is known.

[0003] As a method of measuring the position of such a moving body, an inner field sensor attached to the moving body is used.
So-called dead reckoning is known.

A typical dead reckoning navigation will be described with reference to a moving body 60 having a wheel arrangement of a steered wheel 61 and a fixed wheel 62 as shown in FIG. Here, the direction of the steered wheels 61 can be freely changed with respect to the moving body 60, and the direction of the fixed wheels 62 can be changed with respect to the moving body 60.
Is assumed to be parallel to the direction of.

In order to calculate the position of the moving body 60, the steering angle of the steered wheels 61 of the moving body 60, the moving distance of the steered wheels 61,
The direction of the moving body 60 is measured. As the measuring means, a pulse encoder provided in a drive unit of the steering wheel 61 is used to measure the steering angle and the moving distance of the steering wheel 61, and an internal sensor such as a gyro sensor is used to measure the direction of the moving body 60. General.

Now, the direction of the moving body 60 at a certain time is represented by θ _L ,
Assuming that the steering angle is α and the moving speed of the steered wheels 61 is V _S , the moving speed V _{XS of the} steered wheels 61 in the X direction and the moving speed V of the steered wheels 61 in the Y direction are obtained.
_YS is obtained by the following equation.

V _XS = V _S × cos (θ _L + α) V _YS = V _S × sin (θ _L + α) The position of the steered wheel 61 can be calculated by integrating these moving speeds. Note that the position of the fixed wheel 62 can be obtained from a geometric relationship using the steering angle and the size of the moving body, for example, the wheel base L.

[0008]

At this time, the moving body 60
If the direction θ _L , the steering angle α, and the moving speed V _S of the steered wheels 61 can be correctly measured, no error occurs in the calculation result of the moving body position. However, in general, the measurement of the steering angle α often has an unacceptable error due to an error due to a backlash of a speed reducer included in the steering mechanism and an accurate zero adjustment of the steering angle. For this reason, a measurement error of the position of the moving body caused by the measurement error of the steering angle occurs, which is a practical problem.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a position measuring device which can determine the position of a moving object from the direction of the moving object and the moving distance of a steered wheel.

[0010]

According to the present invention, there is provided a position measuring apparatus for a moving object having at least one steered wheel and a fixed wheel, wherein a first measurement for measuring a direction and a turning angular velocity of the moving object is performed. Means for measuring a moving speed of the steered wheels;
Measuring means for calculating the position of the moving body by using the measurement results of the first and second measuring means and the vehicle body size of the moving body. An apparatus is provided.

It is preferable that the first measuring means is a gyro sensor and the second measuring means is a traveling distance encoder.

[0012] The calculating means may include a first step of obtaining a moving speed of the fixed wheel at a certain time based on a first coordinate system defined for the moving body, And a second step of obtaining a position of the fixed wheel in a fixed second coordinate system, wherein the first step uses a position of the steered wheel as an origin on a moving body, Defining the first coordinate system with the direction in which the steered wheels face as the X axis, and determining a turning radius R _S of the steered wheels from the moving speed and the turning angular velocity of the steered wheels;
Obtaining a turning radius r _L of the fixed wheel from the turning radius R _S and the wheel base of the moving body; and obtaining a moving speed of the fixed wheel from the turning angular velocity and the turning radius r _L. Calculating the moving speed in the X direction and the moving speed in the Y direction of the fixed wheel from the direction of the moving body at a certain time and the moving speed of the fixed wheel in the second coordinate system; Calculating the position of the fixed wheel by integrating the moving speeds of the fixed wheel in the X direction and the Y direction.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A position measuring apparatus according to the present invention is a moving body having one degree of freedom of the axis of a steered wheel, for example, a moving body having one steered axis of a steered wheel 21 as shown in FIG. And
As shown in FIG. 3, the present invention is applied to a moving body in which the steering shafts of two steered wheels 31a and 31b are mechanically connected. FIG.
In this case, by assuming a virtual fixed wheel between the two fixed wheels 22, it can be considered that this corresponds to a wheel arrangement similar to that in FIG. Also, in FIG. 3, the front steered wheels 31
a is the main steering wheel, and the rear steering wheel 31b is the slave steering wheel.
By assuming a virtual fixed wheel between these, it can be considered that this corresponds to a wheel arrangement similar to that in FIG. Further, it is assumed that the steering angles of the steered wheels 31a and 31b are the same and the directions are opposite.

Referring to FIG. 1, a position measuring device includes a gyro sensor 11 for measuring a direction and a turning angular velocity of a moving body,
A traveling distance encoder 12 for measuring the traveling distance and traveling speed of the steered wheels of the moving body, output data from the gyro sensor 11 and the traveling distance encoder 12 installed on the moving body, and are stored in a storage device in advance. It is composed of a known moving body size data (wheel base) and a position calculation unit 13 for obtaining the position and orientation of the moving body.

Hereinafter, the number of the steered wheels 41 as shown in FIG.
First, a description will be given of an example of a moving body using a single fixed wheel 42 as a model. The turning motion of the moving body is a turning motion centered on an intersection Pc between the extension of the axle of the steered wheels 41 and the extension of the axles of the fixed wheels 42. Here, the fixed wheel 42 fixed to the moving body
Is used as a reference point for measuring the position of the moving body, and a method of obtaining the position of the fixed wheel 42 will be described below.

In this method, the following preconditions are required.

(1) The direction of the steered wheels 41 can be freely operated regardless of the direction of the moving body.

(2) The direction of the fixed wheel 42 is fixed to the moving body.

(3) The direction of the moving body is determined by the gyro sensor 1
1 can be measured.

(4) The movement distance is measured by measuring the number of rotations of the steered wheels.

At this time, the moving direction of the fixed wheel 42 is the direction in which the moving body faces regardless of the steering angle. It is clear that the position of an arbitrary point on the moving body can be obtained by a geometric calculation from the position of the fixed wheel 42 and the direction of the moving body.

Referring to FIG. 5, first, the moving speed of fixed wheel 42 at a certain time is obtained.

Now, a first coordinate system is defined in which the position of the steered wheel 41 at a certain time is the origin and the direction in which the steered wheel 41 faces is the X-axis direction.

[0024] The turning radius R _s of the steering wheel 41, the steering wheel 4
1 is obtained from the following equation from the moving speed V _S and the turning angular velocity ωθ of the moving body.

R _s = V _s / ωθ Therefore, the coordinates of the turning center O of the moving body in this coordinate system are (O, R _s ).

Assuming that the distance (wheel base) between the steered wheel 41 and the fixed wheel 42 is L, the position of the fixed wheel 42 is located on the circumference of a circle A having a radius L centered on the steered wheel 41 (origin). I do.

The direction of the fixed wheel 42 does not depend on the steering angle.
It faces the center of the circle A (the direction of the center position of the steering wheel) due to the geometric constraints of the moving body. Therefore, the direction of the axle of the fixed wheel 42 is the tangential direction of the circle A.

Further, the turning center of the fixed wheel 42 is
1, the position of the fixed wheel 42 is equal to the circle A and the rotation center O (O, R) of the steering wheel 41.
_s ) is a contact point C with a tangent line of a circle A passing through.

From above, the turning radius r _{L of the} fixed wheel 42
Is determined by the following equation.

R _L = (R _S ² −L ² ) ^1/2 The turning angular velocity of the fixed wheel 42 is the turning angular velocity ωθ of the moving body.
Therefore, the moving speed _VL of the fixed wheel 42 is obtained by the following equation.

[0031] _{V L = r L × ωθ =} {(V S / ωθ) 2 -L 2} 1/2 × ωθ = {V S 2 - (L × ωθ) 2} 1/2 Then, fixed to the ground position (X _L, Y _L) of the stationary ring 42 in the second coordinate system is determined. This can be explained with reference to FIG.

Now, the direction of the moving body (same as the direction of the fixed wheel 42) at a certain time in the X direction is θ _L ,
The moving speed of 2 is _VL .

The moving speed V _XL , Y of the fixed wheel 42 in the X direction
The moving speed V _{YL in the} direction is obtained by the following equation.

[0034] _{V XL = V L × cosθ L} = (V S 2 - (L × ωθ) 2} 1/2 × cosθ L V YL = V L × sinθ L = (V S 2 - (L × ωθ) 2 ｝ ^1/2 × sin θ _L Therefore, the position (X _L , Y _L ) of the fixed wheel 42 is obtained by integrating the respective moving speeds V _XL and V _YL .

The present invention can be applied to an automatic guided vehicle, an unmanned forklift, an unmanned tractor, and the like.

[0036]

As described above, according to the present invention,
Since it is not necessary to measure the steering angle to estimate the position of the moving body, the position of the moving body can be correctly estimated even when the steering angle cannot be accurately measured.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a configuration of a position measuring device according to the present invention.

FIG. 2 is a diagram for explaining a first example of a wheel arrangement in a moving object to which the present invention is applied.

FIG. 3 is a diagram illustrating a first example of a wheel arrangement in a moving object to which the present invention is applied.

FIG. 4 is a diagram for explaining a position measurement operation according to the present invention.

FIG. 5 is a diagram for explaining a position measurement operation according to the present invention.

FIG. 6 is a diagram for explaining a conventional position measurement operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Gyro sensor 12 Mileage encoder 13 Position calculation device 21, 31a, 31b, 41, 61 Steering wheel 22, 42, 62 Fixed wheel

Claims (4)

[Claims] 1. A position measuring device for a moving body comprising at least one steered wheel and one fixed wheel, wherein: a first measuring means for measuring a direction and a turning angular velocity of the moving body; A movement comprising: a second measuring means for measuring; and a calculating means for calculating the position of the moving body using the measurement results of the first and second measuring means and the vehicle body size of the moving body. Body position measurement device. 2. The position measuring device according to claim 1, wherein
The first measuring means is a gyro sensor, and the second measuring means is a gyro sensor.
Wherein the measuring means is a travel distance encoder. 3. The position measuring device according to claim 1, wherein
The position measuring device for a moving body, wherein the steered wheels have one degree of freedom. 4. The position measuring device according to claim 1, wherein
The calculating means includes: a first step of obtaining a moving speed of the fixed wheel at a certain time based on a first coordinate system defined for a moving object; and a second step fixed to a ground different from the coordinate system. And a second step of obtaining the position of the fixed wheel in the coordinate system of the following. The first step is to set the position of the steered wheel on the moving body as the origin, and to set the direction in which the steered wheel faces. the defining said first coordinate system with X-axis, determining a turning radius R _S of the steering wheel from moving speed and the turning angular velocity of the steering wheel, and the wheel base of the turning radius R _S with the mobile Calculating the turning radius r _L of the fixed wheel from the following, and obtaining the moving speed of the fixed wheel from the turning angular velocity and the turning radius r _L , wherein the second step is the second coordinate In the system, the direction and the front of the mobile at a certain time Calculating the moving speed in the X direction and the moving speed in the Y direction of the fixed wheel from the moving speed of the fixed wheel, and integrating the moving speeds in the X and Y directions of the fixed wheel to determine the position of the fixed wheel. And a step of performing the obtaining step.