JPH1183532A - Location system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a location system wherein correction of an angular sensor is automated by an earth magnetism sensor. SOLUTION: Relating to a location system wherein, with a distance sensor 14 and an angular sensor 12 mounted on a carrier, a calculation circuit 11 for calculating a position coordinate caused by carrier's movement from the measured data with the sensors is provided, an earth magnetism sensor 13 is mounted on the carrier, and at such position as earth magnetism can be measured, an azimuth angle obtained from the measured data of the angular sensor 12 is replaced by that obtained from the measured data of the earth magnetism sensor 13 for correcting the azimuth angle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a location system for obtaining a moving position by using a distance sensor and an angle sensor, and more particularly to a location system for automatically correcting an angle sensor by a geomagnetic sensor.

[0002]

2. Description of the Related Art A location system is used to determine the current position of a manned carrier such as a forklift.
In this location system, an angle sensor for detecting a traveling direction is mounted on a transport vehicle. Angle sensors include:
There are a vibrating gyroscope and an optical fiber gyroscope, and a low drift and high accuracy optical fiber gyroscope is used for a location system.

[0003] In the angle sensor, even if the instantaneous measurement error is small, the error accumulates during long-time operation for a long time. For this reason, in the related art, a specific place in an area to which the location system is applied is determined as a correction place, and position correction and angle correction are performed at this position. At this time, in the angle correction method, the carrier is directed to a specific direction, for example, the direction of a mark such as a white line drawn at the location, and the angle is corrected based on the direction (this operation is referred to as reference adjustment). .

[0004] The error θ between the output angle of the angle sensor in the above location system and the actual direction angle of the transport vehicle.
And the error S between the position coordinates (using the xy coordinates) obtained by the location system and the travel distance L of the transport vehicle can be expressed by the following equation.

Sx = L × sin θ Sy = L × cos θ Therefore, even if the angle error θ is small, the error S of the position coordinates increases in proportion to the traveling distance L. Therefore, it is necessary to correct the angle sensor as frequently as possible.

A geomagnetic sensor is known as a means for obtaining an azimuth different from that of an angle sensor. Since the geomagnetic sensor detects the earth's magnetic field, it can determine the absolute azimuth. However, when a geomagnetic sensor is used in the above location system, the output azimuth causes an error with respect to the true azimuth due to the magnetization of the carrier. Therefore, when the geomagnetic sensor is used, a correction called a magnetization correction is performed.

FIG. 5 shows the principle of magnetization correction. When the output voltage of the geomagnetic sensor is considered as a vector, the output voltage is composed of the vector component of the vector earth magnetic field and the vector component of the magnetization of the carrier. When the carrier rotates 360 degrees or more, only the vector of the earth's magnetic field rotates. At this time, the output voltages (V _X , V _Y ) of the geomagnetic sensor draw a circle as shown in the figure. From the output voltages (V _X , V _Y ), the center coordinates of the earth magnetic field vector are calculated from the following equation.

Z _X0 = (V _X max + V _X min) / 2 Z _Y0 = (V _Y max + V _Y min) / 2 where Z _X0 : X coordinate of the center of the earth magnetic field vector Z _Y0 : of the earth magnetic field vector Y coordinate of center V _X max: maximum value of the output voltage of the geomagnetic sensor in the X-axis direction V _X min: minimum value of the output voltage of the geomagnetic sensor in the X-axis direction V _Y max: maximum value of the output voltage of the geomagnetic sensor in the Y-axis direction V _Y min: the minimum value of the output voltage of the geomagnetic sensor in the Y-axis direction.

The azimuth angle θ of the geomagnetic sensor is calculated by the following equation.

Θ = tan ⁻¹ {(V _X −Z _X0 ) / (V _Y −Z _Y0 ) × K} where V _X and V _Y are the _X and V of the geomagnetic sensor in each direction.
This is the output in the Y-axis direction.

[0011] In addition, K _{is, K = (V X max-} V X min) / (V Y max-V Y min) ... a.

As described above, it is possible to determine the azimuth angle θ by performing the magnetization correction on the influence of the magnetization of the carrier. However, when there is a magnetic field other than the terrestrial magnetic field around the carrier or when the magnetic field is distorted due to the influence of an object, such influence of the surrounding magnetic field cannot be corrected. Therefore,
Generally, in an environment where a transport vehicle is used, it is difficult to use a geomagnetic sensor as a means for obtaining an azimuth because there is an ambient magnetic field depending on a place. However, it can be used only where there is no surrounding magnetic field (where only the earth's magnetic field exists).

[0013]

The conventional location system has the following problems.

1) The operation of turning the carrier in a specific direction is as follows.
It is troublesome work.

2) Since it is necessary to adjust the reference with high accuracy, this operation requires time.

3) Usually, since the driver of the carrier adjusts the direction visually, accuracy is limited and there are individual differences.

4) Since the correction of the angle sensor cannot be automated, the above work is relied on. Even if the location system is introduced, until the skill of the worker is established,
Conversely, it lowers work efficiency.

Further, it is difficult to use a geomagnetic sensor for the location system because of the influence of the surrounding magnetic field as described above.

It is an object of the present invention to solve the above-mentioned problems and to provide a location system for automatically correcting the angle sensor by a geomagnetic sensor.

[0020]

According to the present invention, a distance sensor and an angle sensor are mounted on a carrier, and the position coordinates of the carrier are calculated from the measurement data of these sensors. In a location system provided with an arithmetic circuit, a geomagnetic sensor is mounted on the carrier,
At positions where geomagnetic measurement is possible, the azimuth is corrected by replacing the azimuth obtained from the measurement data of the angle sensor with the azimuth obtained from the measurement data of the geomagnetic sensor.

A coordinate range in which geomagnetism can be measured is stored in advance, and the correction may be performed only when the position coordinates obtained by the arithmetic circuit are within the coordinate range.

[0022]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a configuration diagram of the location system of the present invention. This location system is mounted on a carrier (not shown). This location system
A host computer 11 of the system that executes coordinate calculation and control of a steered wheel, an angle sensor 12 such as an optical fiber gyro, a geomagnetic sensor 13 for correcting the angle sensor 12, a distance sensor 14 for measuring a traveling distance, It comprises a position recognition display 15 for the driver of the carrier and a transmitter 16 for transmitting the position (coordinates) of the carrier to a base (not shown).

In this embodiment, an arithmetic circuit for calculating and correcting position coordinates is constituted by the host computer 11. The general arithmetic processing performed by the host computer 11 will be described with reference to FIG. First, the data of the azimuth sensor (the angle sensor 12) is captured, and the data of the distance meter (distance sensor 14) is captured. Next, as an operation of the location system, a coordinate calculation of the transporter (transportation vehicle) is executed. It is determined whether or not the obtained coordinates are within a specified coordinate range. If not, the data acquisition and the coordinate calculation are continued. If it is within the specified range, the data of the geomagnetic sensor 13 is fetched, the absolute azimuth is calculated, and the absolute azimuth θF is obtained. Direction sensor (angle sensor 1
The correction is performed by replacing the azimuth according to 2) with the absolute azimuth θF.

As described above, the location system of the present invention replaces the azimuth obtained from the measurement data of the angle sensor with the azimuth obtained from the measurement data of the geomagnetic sensor only when it is within the coordinate range where geomagnetic measurement is possible. It is to be corrected. Since the geomagnetic sensor is greatly affected by the surrounding magnetic field, it is unsuitable as an azimuth angle sensor in an environment where a normal transport vehicle or the like operates, but can be used as an absolute azimuth sensor in a place where there is no surrounding magnetic field. Therefore, the angle sensor 12 which is not normally affected by the surrounding magnetic field is used as the azimuth angle sensor, and in a place where the geomagnetic sensor can be used, the geomagnetic sensor is used for correction. In a place where a geomagnetic sensor can be used, a magnetic field is measured in advance and stored as coordinates in a location system. This makes it possible to determine whether or not the transport vehicle is located within a coordinate range where the geomagnetic sensor can be used.

Next, detailed arithmetic processing performed by the host computer 11 will be described with reference to FIGS. First, operation parameters are set as initial settings of the system. next,
As an initial operation, the azimuth angle θ ′ is obtained by the geomagnetic sensor 13 (performed at a location where geomagnetism can be measured).
The output angle (azimuth angle) θ1 of the optical fiber gyro is made to match the azimuth angle θ ′ obtained by the geomagnetic sensor 13. That is, θ1 = θ ′. Thereafter, the operation of obtaining the position coordinates due to the movement of the carrier starts.

The output angle θ _i of the optical fiber gyro (i represents a value obtained by sampling at regular time intervals)
Then, the number of pulses P of the distance meter (the distance sensor 14 outputs one pulse for every constant traveling distance lp) is retrieved, and the traveling distance L is calculated. The arithmetic expression is as follows: L _i = P × lp.

The position coordinates (X _i , Y _i ) of the carrier are obtained from the travel distance of the carrier within a certain time and the angle change θ (θ = θ _i −θ _i-1 ) of the optical fiber gyro during that time. It is calculated from the following equation.

X _i = L _i × cos θ + X _i-1 ... Y _i = L _i × sin θ + Y _i-1 ... Θ = θ _i −θ _i-1 , And it is determined whether or not this carrier is within a coordinate range (areas A and B) stored in advance. That is,
For example if A area to determine whether or not to satisfy the _{XA1 <X i <XA2 YA1 <} Y i <YA2.

If the position coordinates of the carrier are not within the above-mentioned coordinate range, the coordinate calculation based on the direction of the angle sensor 12 is continued. Within the coordinate range, for example, within the A area,
The azimuth θ _i of the optical fiber gyro is made to coincide with the azimuth θA of the geomagnetic sensor 13. That is, θ _i = θA. The correction is performed in this manner.

At this time, since the terrestrial magnetism sensor 13 is an absolute azimuth sensor, the carrier may be in any direction as long as the carrier is in the area A. Therefore, there is no need to align the transport vehicle in a fixed direction as in the related art.

Thereafter, when the vehicle exits the area A, the influence of the surrounding magnetic field may be present. Therefore, the coordinate calculation based on the azimuth of the angle sensor 12 is continued. However, the accumulation error of the azimuth up to that point is eliminated by the correction. Therefore, the position coordinates of the carrier can be obtained with high accuracy.

The areas A and B are areas where the influence of the surrounding magnetic field and the change over time of the magnetic field are small, and the output direction of the geomagnetic sensor 13 can be regarded as correct. As such a place, specifically, near the entrance without iron lump or motor,
A resting place, a material storage area, and the like can be considered. You can find such places even indoors. When introducing this system, it is preferable to measure the azimuth at several places using a geomagnetic sensor and compare this azimuth with the true azimuth derived from optical surveying or the like to select an appropriate place with a small error.

An angle sensor 12 such as an optical fiber gyro
The error from the true azimuth accumulates as the travel time and travel distance increase. However, in the location system of the present invention, if the azimuth of the angle sensor 12 is corrected at any time or at regular intervals, such as by causing the transport vehicle to pass through the area at any time or at regular intervals, no error is accumulated. Therefore, the azimuth accuracy can always be maintained at a certain level or more, and the angle sensor 12 can indicate the direction of the carrier.

Further, when the carrier enters an area designated in advance, the angle correction is automatically executed, so that the present invention can be applied to an unmanned carrier and the like. When the location system of the present invention is mounted on an automatic guided vehicle, the track securing tape conventionally installed on the track of the guided vehicle can be eliminated. For example,
It is suitable for a device such as a cleaning robot in which a tape cannot be placed on a track.

In this embodiment, an optical fiber gyro is used for the angle sensor 12, but a vibration gyro may be used, or the angle of a steered wheel may be monitored by an encoder to measure the angle.

[0037]

The present invention exhibits the following excellent effects.

(1) Since the geomagnetic sensor is an absolute direction sensor, it can be corrected easily and with high accuracy.

(2) Whether or not to correct the angle by the angle sensor is determined in the coordinate range where the carrier is located, so that the correction can be completely automated.

(3) The present invention can be applied to an automatic guided vehicle as well as an automatic guided vehicle.

[Brief description of the drawings]

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

FIG. 2 is a schematic flowchart of the arithmetic processing of the present invention.

FIG. 3 is a detailed flowchart of the arithmetic processing of the present invention.

FIG. 4 is a diagram of a coordinate system showing position coordinates of a transport vehicle according to the present invention.

FIG. 5 is a principle diagram of magnetization correction.

[Explanation of symbols]

 11 Host computer 12 Angle sensor 13 Geomagnetic sensor 14 Distance sensor

Claims (2)

[Claims] 1. A location system in which a distance sensor and an angle sensor are mounted on a carrier and an arithmetic circuit is provided for calculating position coordinates of the carrier based on measurement data of these sensors. And a azimuth angle correction unit that replaces the azimuth angle obtained from the measurement data of the angle sensor with the azimuth angle obtained from the measurement data of the geomagnetic sensor at a position where geomagnetism can be measured. 2. The apparatus according to claim 1, wherein a coordinate range in which geomagnetism can be measured is stored in advance, and said correction is performed only when the position coordinates obtained by said arithmetic circuit are within the coordinate range. Location system.