JPH09229697A - Self-position orienting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out self-position orientation even at a site where no GPS radio waves reach by carrying out computation processing using output signals from a high-pass filter through which only high frequency components of output signals of a gyroscope can pass, a low pass filter through which only low frequency of output signals of a flux gate compass can pass, and an odometer. SOLUTION: A high pass filter 6 removes low frequency wave components from output of a gyroscope 2 and the output of the filter 6 is supplied to a computing process apparatus 5. A flux gate compass 7 detects the North and sends out the deflection from the North as an electric signal. A low pass filter 8 removes high frequency components from the output of the flux-gate compass 7 and the output of the filter 8 is supplied to the computing process apparatus 5. The total of the angular signals processed by the filters 6, 8 becomes an angle formed between the proceeding direction of a vehicle 1 and a standard line for a certain time duration and the angle is sent to the computing process apparatus 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for locating a self-position of a moving body such as automating a carrier vehicle.

[0002]

2. Description of the Related Art Conventionally, a global positioning system (Global Positioning System) has been used as an apparatus of this type.
ysystem, hereinafter referred to as GPS), a method of calculating a self-position from an angle detected by a gyro and a traveling distance of an odometer, and a method of calculating a self-position from an angle detected by a gyro and a traveling distance of an odometer and correcting it by GPS. , There is a method of correcting the self-position obtained from GPS with an azimuth sensor. As is well known, GPS is a general term for a system which receives radio waves transmitted from a plurality of artificial satellites and calculates the latitude, longitude and altitude of its own position from the time difference between the radio waves based on the principle of triangulation. In recent years, these self-positioning devices have been often used for automobile navigation (hereinafter referred to as car navigation). In car navigation, it is important to detect that a vehicle traveling on the road is traveling correctly on the road and display it on a CRT or the like.

For example, as a vehicle-mounted position display device, which is one form of a self-locating device for a car navigation system, Japanese Patent Publication No.
There is a structure as shown in FIG. 11 disclosed in Japanese Patent No. 66052. In FIG. 11, 30 is a direction sensor,
Reference numeral 31 includes an antenna unit for receiving radio waves from a satellite by a GPS positioning unit, a reception radio wave processing unit, a signal processing unit, and the like. The outputs of the direction sensor 30 and the GPS positioning means 31 are CP
The data is input to U32, and the output of the CPU 32 is further input to the map information storage means 33. One output of the map information storage means 33 is input to the display processing means 35 including the display memory 34, and the other output is input to the geodetic system correction means 36. The output of the geodetic system correction means 36 is input to the display processing means 35. Reference numeral 37 is a display device which is connected to the output side of the display processing means 35 and simultaneously displays the map information and the current position of the positioned vehicle. Here, the map information storage means 33 stores a map relating to the road of the traveling automobile including the position data of the branch point of the road direction.

Next, the operation will be described. The GPS positioning means 31 receives radio waves from artificial satellites (not shown) constituting a plurality of GPSs and measures the current position of the running vehicle. On the other hand, the map information stored in the map information storage means 33 is generally measured and created irrespective of GPS. Therefore, the GPS positioning means 31
If the position measured by is stored in the display memory 34 together with the map information stored in the map information storage means 33 and is to be displayed on the display 37, a difference due to the difference in the geodetic system will appear. Therefore, the CPU 32 is introduced with the information on the traveling azimuth measured by the azimuth sensor 30 and the position information measured by the GPS positioning means 31. The CPU 32 uses the map information storage unit 33 to store both pieces of information obtained by the direction sensor 30 and the GPS positioning unit 31 in the geodetic system correction unit 3.
6 The geodetic correction means 36 changes the traveling direction from the direction sensor 30 when the traveling direction of the vehicle changes, and changes the road orientation of the road connected to the branch point near the position of the vehicle measured by the GPS positioning means 31. Compare.

As shown in FIG. 12, when a vehicle is traveling on a road R1 along a direction of an angle α1 from a reference line indicated by a broken line, it approaches a branch point, and then an angle α2 from the reference line. Road R
When the course is changed to 2, the point where the traveling direction from the direction sensor 30 has changed is the branch point Q. Therefore, the fact that the vehicle has passed the branch point Q can be recognized by the change in the traveling direction from the direction sensor 30. At the branch point Q found by the change in the running direction from the direction sensor 30, the road branch point on the map information near the position of the vehicle measured by the GPS positioning means 31 is found. When the change in the road direction between the roads connected to the branch point of the road found on the map information matches the change in the running direction from the direction sensor 30, it is determined that both branch points are the same. Even if there are a plurality of branch points on the map information in the vicinity, a branch point in which the change in the road direction matches the change in the running direction from the direction sensor 30 is determined.

From the position of the vehicle measured by the GPS positioning means 31 and the position of the branch point of the map information stored in the map information storage means 33, the deviation in latitude and longitude caused by the difference in the geodetic system is calculated. Calculate Then, this deviation is added to the position data of the vehicle measured by the GPS positioning means 31. As a result, the geodetic system correction means 36 corrects the GPS geodetic system to position data suitable for the map geodetic system. The corrected position data is sent to the display processing means 35, stored in the display memory 34, and displayed on the display 37. That is, the display 37 can display the current position of the automobile on the road map without any deviation in association with the map information.

In such a vehicle-mounted position display device, the current position of the automobile is displayed on the road map for the purpose of teaching the driver's own position. However, except for the portion related to the display, it is one of the self-position locating devices. It can be considered as a form.

FIG. 13 shows another form of the conventional self-locating apparatus, which is an improved version of what is called dead-reckoning navigation, integral navigation or self-contained navigation, and FIG. 14 is a block diagram thereof. In FIGS. 13 and 14, 1 is a vehicle body, 2 is a gyro that detects an angle of the vehicle body 1 in the yaw direction, 3 is a wheel that is a component of an odometer, 4 is an encoder that is a component of an odometer, and an axle of the wheel 3 Is attached to. 5
Is an arithmetic processor for calculating the self-position by inputting the signal from the gyro 2 and the signal from the encoder 4. Now car body 1
It is assumed that the current position (x0, y0) of is known. The angle β1 formed by the traveling direction of the vehicle body 1 and the reference line during the time τ1 of the gyro 2 is detected, and the angle β1 is input to the arithmetic processing unit 5. The moving distance λ1 during the time τ1 is obtained from the circumferential length L of the wheel 3 and the rotation speed ν1. The rotation speed ν1 is input to the arithmetic processing unit 5 as an output pulse from the encoder 4. The position (x1, y1) after the time τ1 is the moving distance λ
1, the angle β1 and the current position (x0, y0) have a relationship as shown in FIG.

[0009]

[Equation 1]

The following relationship holds. The arithmetic processor 5 performs this calculation and outputs the position (x1, y1) after the time τ1.

Thereafter, the vehicle body 1 is turned for a time τ2.
Assuming that the traveling direction of is an angle β2 with the reference line, the angle β2 and the movement distance λ2 are detected and input to the arithmetic processing unit 5 in the same manner as above. In the arithmetic processing unit 5, the time τ1 +
The position (x2, y2) after τ2 is calculated. However, since the gyro 2 has a drift, it is inevitable that an error is included in the detected value of the angle. As can be seen from FIG. 15, it is clear that this error is cumulative. In order to correct the deterioration of the orientation accuracy of the position due to the accumulation of this error, G
Correct by PS.

[0012]

Since the conventional device is constructed as described above, the position cannot be located or the position cannot be corrected in a place where GPS radio waves cannot be received. However, GPS is used in buildings under construction.
There was a problem that the radio wave of could not be received. In addition, there is a problem that the location cannot be located in a place where there is no road map such as a site of civil engineering work. This invention uses GPS
The purpose is to enable the self-localization of a moving body even in a building under construction where radio waves do not reach or where there is no map.

[0013]

A self-locating device according to the present invention comprises a gyro for detecting an angle, a high-pass filter, a fluxgate compass for detecting north, a low-pass filter, an odometer for detecting a traveling distance, and a gyro. It is composed of an arithmetic processing unit for inputting a signal obtained by processing a signal from the fluxgate compass with a filter and a signal from an odometer and calculating a self-position so that errors are not accumulated without the aid of GPS.

Further, the self-locating device according to the present invention comprises an odometer for detecting a traveling distance, which is composed of wheels and an encoder mounted on an axle of the wheels.

Further, the self-locating device according to the present invention uses the wheels constituting the odometer as detection wheels different from those for traveling.

Further, the self-locating apparatus according to the present invention has the detection wheel mounted so as to be freely rotatable with respect to the vehicle body, and detects the rotation angle of the detection wheel with respect to the vehicle body.

Further, the self-locating apparatus according to the present invention has a gyro for detecting the angles of the three axes of the vehicle body, three high pass filters, a fluxgate compass for detecting the north, and an inclination for detecting the inclination of the two axes of the vehicle body. Meter, three low-pass filters, an odometer for detecting the distance traveled, an arithmetic processor for calculating the self-position by inputting the signal from the gyro / fluxgate compass and the signal from the inclinometer with a filter and the signal from the odometer. It is designed to prevent the error due to inclination from accumulating even when traveling on a sloping ground.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. 1 shows a self-positioning apparatus according to Embodiment 1 of the present invention, and FIG. 2 shows a block diagram thereof. 1 and 2, 1 to 5 are the same as those of the conventional self-positioning apparatus. A high-pass filter 6 removes low-frequency components from the output of the gyro 2, and its output is supplied to the arithmetic processor 5. Reference numeral 7 is a flux gate compass that detects north and outputs a deviation from north as an electric signal, and 8 is a low pass filter that removes high frequency components from the output of the flux gate compass 7, and the output thereof is also supplied to the arithmetic processing unit 5.

FIG. 3 is a diagram for explaining the operating principle of the flux gate compass 7. In the figure, 71 is a toroidal core made of a magnetic material, 72 is a detection winding 1, 73 is a detection winding 2 and 74 is a drive winding, and two sets are wound as shown. When a magnetic field is applied to a core made of magnetic material, the magnetic flux bends along the core, but when the core is magnetically saturated, the magnetic flux of the external magnetic field is not affected by the core. But,
The magnetic flux inside the core changes under the influence of the external magnetic field. The change is detected by the two detection windings 72 and 73, and north is calculated. The drive winding 74 is for magnetically saturating the magnetic flux inside the toroidal core 71. The output of Fluxgate Compass 7 is

[0020]

[Equation 2]

Is given by Here, θ and ω are the pitch angle and roll angle of the fluxgate compass 7, ψ _mag is the magnetic azimuth angle, and f _x , f _y , and f _z are the x, y, and z outputs of the fluxgate compass, respectively. If both pitch and roll are zero, north can be easily detected.

Next, the operation will be described. The drift of the gyro 2 appears as a low frequency component of the output signal of the gyro 2. The signal obtained by processing the output signal of the gyro 2 with the high-pass filter 6 does not include a low-frequency signal component due to drift. The output signal of the gyro 2 when the vehicle body slowly changes its traveling direction becomes a low-frequency signal component, which is not included in the signal after being processed by the high-pass filter 6. The fluxgate compass 7 detects the angle formed with the reference line of the vehicle body 1 from the change in magnetism as described above. Fluxgate compass 7
Is, in principle, vulnerable to magnetic noise, and its output will fluctuate at high frequencies.

The signal after the output signal of the fluxgate compass 7 is processed by the low-pass filter 8 does not contain a high frequency signal component due to magnetic noise. Only the low-frequency signal component is included in the signal after being processed by the low-pass filter 8, such as the change in the angle with respect to the earth's magnetism when the vehicle body slowly changes its traveling direction. It is assumed that the current position (x0, y0) is known.
The sum of the angle signal detected by the gyro 2 and processed by the high-pass filter 6 and the angle signal detected by the fluxgate compass 7 and processed by the low-pass filter 8 indicates that the traveling direction of the vehicle body 1 during a certain time τ1 is the reference line. Angle β1. The angle β1 is input to the arithmetic processor 5. That time τ1
The moving distance λ1 between them is obtained from the circumferential length L of the wheel 3 and the rotation speed ν1 as in the conventional device. The rotation speed ν1 is input to the arithmetic processing unit 5 as an output pulse from the encoder 4. The arithmetic processing unit 5 performs the calculation of "Equation 1", and the time τ
The position (x1, y1) after 1 is output.

After that, assuming that the direction of travel of the vehicle body 1 during a certain time τ2 of changing direction is the angle β2 with the reference line, the angle β2
And the moving distance λ2 is detected and inputted to the arithmetic processing unit 5 in the same manner as described above. The arithmetic processing unit 5 performs the same calculation as above to calculate the position (x2, y2) after the time τ1 + τ2. The drift of the gyro 2 will be corrected by the flux gate compass 7 in this way.

Embodiment 2 FIG. 4 shows a self-locating device according to Embodiment 2 of the present invention. In FIG. 1, the wheel 3 is not particularly limited and may be shared with the traveling wheel. However, the traveling wheel needs to transmit the driving force to the ground or the like, and slipping is inevitable depending on the relationship between the ground condition and the driving force to be transmitted. FIG. 4 is one of the solutions in that case, and the block diagram is the same as FIG. Reference numeral 3 denotes a detection wheel provided separately from the traveling wheel 9. This wheel rotates along the ground as the moving body advances due to the frictional force between the ground and the wheel. Since this wheel has no driving force itself, the friction with the ground is always static friction, and the friction with the ground is dynamic friction (static friction torque >> dynamic friction torque). Strength is obtained and it is difficult to slip. By providing the detection wheel 3 separately from the traveling wheel 9 in this way, the detection wheel 3 rotates without slipping regardless of the magnitude of the driving force or the ground condition and the moving distance is accurately measured. be able to. In this embodiment, the traveling wheels are not limited to this, and there is no problem even if the track is a track or the like.

Embodiment 3 FIG. FIG. 5 shows a self-locating device according to Embodiment 3 of the present invention. When the detection wheel is provided separately from the traveling wheel 9 as in the second embodiment, the odometer may be installed on a ready-made traveling vehicle. FIG. 5 is one of the solutions in that case, FIG. 6 is a detailed view of the odometer, and FIG. 7 is a block diagram in that case. Reference numeral 10 is a support for attaching the detection wheel 3 to the vehicle body 1. 11 is a support tool 1
The shaft is attached so as to rotate freely with respect to 0, and the detection wheel 3 is attached to one end thereof. Reference numeral 12 is an angle detector for detecting the rotation angle of the shaft 11 with respect to the support 10, and is a potentiometer here. As described above, the detection wheel 3 is attached to the vehicle body 1 so as to be freely rotatable, and the angle with respect to the vehicle body 1 is detected. For detection 3
The can rotate without slipping in the lateral direction, so the moving distance can be accurately measured. Travel distance λ during time τ1
1 is the circumferential length L of the wheel 3, the rotational speed ν from the encoder 4
1, the rotation angle of the shaft 11 with respect to the support tool 10 provided by the potentiometer 12 is γ1,

[0027]

(Equation 3)

It is calculated by In this way, time τ1
The position (x1, y1) after the time τ1 can be obtained by using "Equation 1" by calculating the moving distance λ1 between.

The left and right endless tracks are turned in the opposite direction in the car body 1 having the endless track, and the shaft 11 rotates even when the in-situ rotation called super-spinning turning is performed, and the axle of the wheel 3 for detection is the vehicle body 1. The wheel 3 for detection can be rotated by rotating the wheel 3 at a right angle with respect to. At that time, even if the wheel 3 for detection is rotated, γ is approximately 90 in "Equation 3".
Since it is a degree, it becomes almost 0, and the reality that it hardly moves can be measured.

Fourth Embodiment FIG. 8 shows a self-locating apparatus according to Embodiment 4 of the present invention. In the embodiments described so far, the angle on the plane is detected, but the movement distance is detected from the rotation speed of the wheel, so a flat place such as a building under construction or a place with no undulations. Then there was no such error. However, when used outdoors such as in a place with many slopes, as shown in FIG. 9, the measurement of the moving distance is the length of the slope of the slope detected from the rotation speed of the wheels, not the length projected on the horizontal plane. It included the problem. FIG. 8 is one of the solutions in that case, and FIG. 10 shows a block diagram. Reference numerals 13 and 14 denote gyros for detecting the pitch and roll angle of the vehicle body 1, and are referred to as a yaw gyro 2, a pitch gyro 13, and a roll gyro 14 in order to distinguish the gyros from each other. Reference numerals 15 and 16 are inclinometers for detecting the pitch and the inclination of the roll, and are also called a pitch inclinometer 15 and a roll inclinometer 16 for distinction. 17,
Reference numeral 18 denotes second and third high-pass filters that remove low-frequency components including signal components due to drift from the outputs of the pitch gyro 13 and the roll gyro 14, and the high-pass filter 6 is called a first high-pass filter for distinction. These first high-pass filter 6 and second high-pass filter 1
7, the output of the third high-pass filter 18 is the arithmetic processor 5
Is supplied to Reference numerals 19 and 20 are for removing high frequency components from the outputs of the pitch inclinometer 15 and the roll inclinometer 16.
The low-pass filter 8 is referred to as a first low-pass filter for distinction by the third low-pass filter. These first low-pass filter 8, second low-pass filter 19, third
The output of the low-pass filter 20 is also supplied to the arithmetic processing unit 5.

The actual world is developed in a three-dimensional space, and the space in which the car body 1 moves around is also three-dimensional.
When locating its own position or pointing a target on a map, two-dimensional coordinates obtained by projecting the three-dimensional space on a horizontal plane are used. As shown in FIG. 9, the difference appears as a difference in the moving distance λ. That is, in FIG. 9, A, B, C, and D are actual ground surfaces, and E, F, G, and H are surfaces obtained by projecting A, B, C, and D on a horizontal plane. Points S and T are points on the planes A, B, C, and D, which are the starting point and the ending point of the movement. The moving distance λ measured on the ground surface matches the length of the line segment ST. If the point L is the projection point of the point S and the point M is the projection point of the point T on the surfaces E, F, G, and H, the line segment LM
The length of is the moving distance κ on the horizontal plane. Let θ be the pitch angle of the vehicle body 1 when moving on the line segment ST

[0032]

(Equation 4)

By performing coordinate conversion as represented by, the moving distance κ on the horizontal plane can be obtained. The fluctuation of the roll angle is not related to the moving distance. The Fluxgate compass 7 detects north on the surface where it is installed. Body 1
Has an angle of roll and pitch, the fluxgate compass 7 also has that angle, which causes an error.

The pitch angle θ and the roll angle ω of the vehicle body 1 can be detected by the pitch gyro 13 and the roll gyro 14. Since the gyro has a drift, the second high-pass filter 17 and the third high-pass filter 18 remove low-frequency components including a signal component due to the drift from the outputs of the pitch gyro 13 and the roll gyro 14 in order to correct the drift. The pitch inclinometer 15 and the roll inclinometer 16 detect a change in angle including a case where the traveling inclination and the vehicle body posture are slowly changed. Since the inclinometer has a long time constant and the output cannot catch up with a rapid angle change, the signal after the output is processed by the second low-pass filter 19 and the third low-pass filter 20 has a slow running inclination and a vehicle body. Only the change in angle when the posture is changed remains. In this way, the pitch angle θ and the roll angle ω can be detected while removing the influence of the drift of the gyro. Using the signal, the output of the fluxgate compass is coordinate-transformed as in "Equation 2" to detect the north.

[0035]

Since the present invention is configured as described above, it has the following effects.

A gyro signal for detecting an angle is processed by a high-pass filter to eliminate the influence of drift, and a signal for a fluxgate compass for detecting north is processed by a low-pass filter so that the vehicle body slowly changes its traveling direction. In this case, an error is not accumulated without the aid of GPS by outputting a signal in the case of being operated and inputting a signal from an odometer for detecting a traveling distance to an arithmetic processing unit to calculate a self position.

Further, since the odometer for detecting the traveling distance is composed of the wheel and the encoder attached to the axle of the wheel, there is an effect that the electrical interface can be simplified.

Further, by making the wheels constituting the odometer be detection wheels different from those for running, it is possible to eliminate the influence of wheel slippage and the like.

Further, the detection wheel is attached so as to be freely rotatable with respect to the vehicle body, and the rotation angle of the detection wheel with respect to the vehicle body is detected, so that there is an effect that this device can be incorporated into a ready-made vehicle body.

The output signals of the gyroscope for detecting the angles of the three axes of the vehicle body are processed by three high-pass filters to eliminate the influence of drift, and the signal for changing the flux for detecting north is output to output the traveling distance. By inputting the signal from the odometer which detects the signal to the arithmetic processing unit and calculating the self-position, the error is detected by the output signal of the inclinometer which detects the inclination of the two axes of the gate compass and the car body without the aid of GPS.
By processing with one low-pass filter, there is an effect that the vehicle body does not slowly accumulate the running direction and tilt vehicle body posture.

[Brief description of drawings]

FIG. 1 is a diagram showing a vehicle body equipped with a self-locating device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of a self-locating device according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating an operation principle of a fluxgate compass.

FIG. 4 is a diagram showing a vehicle body equipped with a self-locating device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a vehicle body equipped with a self-locating device according to a third embodiment of the present invention.

FIG. 6 is a diagram showing details of an odometer according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a self-locating device according to a third embodiment of the present invention.

FIG. 8 is a diagram showing a vehicle body equipped with a self-locating device according to a fourth embodiment of the present invention.

FIG. 9 is an explanatory diagram when a slope is moved.

FIG. 10 is a block diagram showing a configuration of a self-locating device according to Embodiment 4 of the present invention.

FIG. 11 is a block diagram showing a configuration of a vehicle-mounted position display device, which is one form of a conventional self-locating device.

FIG. 12 is a diagram for explaining the operation of a vehicle-mounted position display device, which is one form of a conventional self-locating device.

FIG. 13 is a diagram showing a vehicle body equipped with a conventional self-locating device.

FIG. 14 is a block diagram showing a configuration of a conventional self-locating device.

FIG. 15 is a diagram for explaining a relationship between an angle and a coordinate.

[Explanation of symbols]

1 vehicle body, 2 gyro, 3 wheels (for detection), 4
Encoder, 5 arithmetic processor, 6 (first) high-pass filter, 7 fluxgate compass, 8 (first)
Low pass filter, 9 wheels for traveling, 10 supports, 11 shafts, 12 potentiometers, 13
Pitch gyro, 14 roll gyro, 15 pitch inclinometer, 16 roll inclinometer, 17 second high pass filter, 18 third high pass filter, 19 second low pass filter, 20 third low pass filter, 3
0 direction sensor, 31 GPS positioning means, 32 CP
U, 33 map information storage means, 34 display memory, 3
5 display processing means, 36 geodetic system correction means, 37 indicator, 71 toroidal core, 72 detection windings 1, 73
Detection winding 2,74 Drive winding.

Claims (5)

[Claims] 1. A gyro that detects a posture angle of a moving body on a plane, a high-pass filter that passes only high-frequency components of an output signal of the gyro, and a fluxgate compass that detects a true north direction with respect to a traveling direction of the moving body. , A low-pass filter that passes only the low-frequency component of the output signal of the fluxgate compass, an odometer that detects the traveling distance of the moving body, and a self-position of the moving body using the output signals from the high-pass filter, the low-pass filter, and the odometer. A self-position locating device comprising: an arithmetic processing unit for arithmetically processing. 2. The self-positioning apparatus according to claim 1, wherein the odometer for detecting the traveling distance is composed of a wheel of the moving body and an encoder attached to an axle of the wheel. 3. The self-positioning apparatus according to claim 2, wherein the wheels forming the odometer are detection wheels different from those for traveling. 4. The self-positioning apparatus according to claim 3, wherein the detection wheel is attached so as to be freely rotatable with respect to the vehicle body, and an angle detector for detecting a rotation angle of the detection wheel is provided. 5. A gyro that detects roll, pitch, and yaw triaxial angles of a vehicle body, three high-pass filters that pass only high-frequency components of the output signal of the gyro, and a true north direction with respect to the traveling direction of a moving body is detected. Fluxgate compass, inclinometer that detects the inclination of the two axes of roll and pitch of the vehicle body, three low-pass filters that pass only the low-frequency components of the output signals of the fluxgate compass and the inclinometer, and the travel distance Odometer to detect and above 3
A self-positioning device comprising: one high-pass filter, three low-pass filters, and an arithmetic processing unit that arithmetically processes the self-position of a moving body using output signals from an odometer.