WO2004018971A1

WO2004018971A1 - An instrument for measuring the traveled distance

Info

Publication number: WO2004018971A1
Application number: PCT/SE2002/001495
Authority: WO
Inventors: Sven Milton
Original assignee: Milton Medicinteknik Kb
Priority date: 2002-08-22
Filing date: 2002-08-22
Publication date: 2004-03-04
Also published as: AU2002326267A1

Abstract

Measuring instrument with batteries, display and buttons where the distance that the instrument is moved from one measuring point to another is calculated from acceleration readings delivered by one or more acceleration sensing devices.

Description

An instrument for measuring the traveled distance.

In order to measure distances it is known to use tape measures or rulers of different types and it is even known to use devices based on the emitting of light or sound that is reflected and returned to a device in order to measure distances. These later devices are practical when for instance measuring distances between walls in furnished rooms and the height of ceilings, but can on the other hand not be used to measure irregular objects from the outside. Tape measures are extremely useful in many applications but are frequently too short, and longer tape measures sometimes even require two persons to hold the ends. The real problems however arise when you wish to measure outside dimensions, for instance the length of a car or distances where there are objects obstructing the straight measuring line. Also, these measurements require a combination of several measurements to be taken, and thus increase measurement errors and take more time to perform.

As apparent from the above there exists a need for a measuring instrument that overcomes the above drawbacks providing more versatile measuring instrument.

In accordance with the invention this is solved by using a number of sensors for acceleration in the measuring instrument together with a computing unit that from the acceleration data computes the distance that the unit is moved or travels from one measuring point to another.

Preferably the invented measuring instrument is handheld.

A particular problem that has to be addressed in the invented instrument is that the instrument in itself, when moved by the user, will inevitably be rotated. As the instrument is rotated, acceleration signals will be acquired that are different to those otherwise obtained.

In order to compensate for this, the device needs to measure its own rotational movements.

One way of solving this problem is to provide it with one or several gyro devices. Another way is by use of gravity signals sensed by the accelerometers, allowing in the following calculation compensation for the rotation.

Another way to solve the above problem is to suspend the acceleration measuring sensor or sensors in such a way that they always have the same direction to gravity, even if the instrument is rotated. This can be achieved by housing the sensor or sensors in a spherical housing, that is fitted in yet another spherical housing, and utilizing a liquid or steel balls etc. between these housings, allowing the inner spherical housing to freely rotate in the outer housing. This enables the center of mass of the inner sphere always to be below the center of the inner sphere. Communication with the acceleration sensing devices can for instance be achieved with electromagnetic field transfer, or light communication if the spheres are translucent. Power to the acceleration sensing devices can be transferred with an electromagnetic field. The acceleration measuring devices can as an alternative be suspended in a swing/pendulum arrangement. In these latter cases, the rotation of the instrument around the rotation of the instrument around the vertical axis may be measured with optical sensors, sensing the rotation of the outer spherical housing in relation to the inner spherical housing, or rotational sensors.

If the acceleration measuring sensor or sensors sense the different acceleration vector components (X; Y; Z) in one and the same point, the computation the device and computation is comparatively simple. However the sensors available on the market displaying this feature are comparatively inaccurate.

In a preferable embodiment of the invention the accelerometers are of a two axle type and the number of accelerometers is three and they are arranged at different locations in the instrument, and at for this purpose optimal angles to each other, preferably perpendicular.

The invented instrument thus solves the problem of measuring outside measurements of objects that are not made up of right angles only.

The invented measuring instrument has however turned out to be capable of even more complicated tasks, since it actually functions as a "hand held coordinate measuring instrument" it can keep track of levels, parallellity and coinciding locations inside and outside of walls, for the drilling of holes etc. This means that a lot of different types of measuring can be made faster and more easily than today.

When the instrument is used as a leveling instrument instead of a water level it should be noted that the level indication will not be influenced by light falling from the left or right side or if lighting is poor or if the person doing it is untrained or has impaired eye-sight.

By providing the invented measuring instrument with sighting means, measurements out of reach can also be taken, for instance heights of trees before taking them down etc. , by providing the instrument with appropriate calculation programs.

With appropriate simple programs areas and volumes can also be measured/calculated.

Furthermore, the instrument can measure a sum of several distances. This is very useful when measuring the total length of plumbing, electrical wiring etc.

Of course it is also possible to check if a house's concrete foundation form is rectangular as well as if the continued building of it follows the intentions of the builder. If so desired the instrument may download intended measurements through an appropriate interface and then on measuring (during building) indicate occurring deviations for possible correction.

By the provision of extensions or handles, measuring to or from points that you can not reach easily also becomes possible.

Results can be stored in the memory of the instrument for later use, such as further calculations.

The invented instrument is preferably provided with a display and software that cannot only show measured figures, but also visualize for the user how to use the instrument in different applications. For instance how and in which order to step by step conduct the different measurements when, for instance, measuring the height of a tree by first sighting at the top, and then measuring the distance from the sighting point to the tree trunk by walking to it. The display may also, while measuring, continuously display the distance the instrument has been moved from a first measuring point, and/or spatial coordinates in three axis.

Further advantages of the invention will become apparent in the description below of an embodiment of the invention shown in the appended drawings. In the drawings fig 1 shows the general appearance of an instrument in accordance with the invention, fig 2 depicts a block scheme of the instrument, Fig 3 shows the instrument with front cover removed, fig 4 is a side view, Fig. 5 shows the effect of gravity as the instrument is rotated around one axis, and. Fig. 6 shows an example of use.

As shown in fig. 2, the accelerometers (1) are connected to a digital signal processor/micro- controler arrangement (2). This forwards data to a display driver (3), which in turn forwards appropriate signals to the display (4). The instrument is powered by a battery pack (5), which in turn is controlled by the power controller (6).

In fig. 3 and fig. 4 the instrument is shown with its front cover removed to show the instrument's principle, and an example of locations for the accelerometers. The long arrows shows the force of gravity, and the thinner arrows show the directions of sensitivity of the accelerometers.

Fig. 6 shows an example of use: measuring distance, surface area and volume of a box.

Description:

The invented electronic measuring instrument is a small and handheld instrument and basically measures the nearest distance between two points in space through movement of the instrument.

These points in space are defined as the point where the upper right corner of the instrument casing is located at the time of pressing the "Measure" button on the instrument's panel for the first point, and second time for the second point. The distance between these points is derived from signals from accelerometers or gyroscopes or a combination thereof.

When the instrument is held with the assigned measuring tip at a measuring point the instrument should be held as still as possible while the instrument takes a number of accelerometer readings in order to assess a very precise gravity vector and assess the signals for no movement. If the instrument finds that readings differ from expected calculated figures, or if the measurement is made in such way that an unacceptable error may occur, a correction may be calculated, and or the estimated error may be indicated. If the possible error is too great, the measuring points may be retraced in the reverse order or the original order or in a more appropriate fashion, until the error is reduced sufficiently. Alternatively of course every separate distance may be remeasured until sufficiently precise figures are obtained.

By moving and rotating a new instrument along a known distance or path in different directions and rotating in a known angle, the instrument can be calibrated thus increasing the precision of the instrument.

Also the number of accelerometers or other measuring instruments may be increased in order to increase the accuracy of the instrument.

The instrument measures the distance by double integration of the acceleration measured preferably by a set of accelerometers. Single integration derives speed. Conceptually, the accelerometers are arranged to measure acceleration in all three basic geometrical axis. Also, the instrument must be able to identify the angle to the force of gravity, as gravity is interpreted as acceleration by the accelerometers. As the instrument is rotated, in any of the three geometrical axis, or combinations thereof, while being moved from one measuring point to another, gravity inflicted in the accelerometers' measuring axis will variably change. This furnishes that gravity can be used in the signal processing to assess necessary information of how the instrument is tilted and/or turned while measuring. Also, the direction of movement will be measured by different accelerometers, as the signals from each axis on the accelerometers will shift between themselves as the instrument is rotated. The assessment of direction to gravity can be used to calculate the instruments' rotations, and thus establish said shifts of movement data between the accelerometers. Data acquisition, all calculations and the display of results on a display is performed by a digital signal processor or a microcontroler or a combination thereof.

In the measuring algorithm, the geometry of the instrument is defined as the points where the accelerometers are located, and a measuring point, preferably a corner of the instrument casing. The measuring point can however be redefined by the user, by use of the instrument's menu functions to select any corner or other physically easily defined tip on the instrument casing. This said tip can optionally be substituted for measuring tips of various lengths and shapes.

The instrument shown in fig. 1 is provided with one key for activation (on/off) of the instrument, one key for starting and stopping measurements (Measure) and a menu selection key.

The instrument is turned on by pressing the "On/Off" button, and turned off by prolonged pressing of the "On/Off" button. With the "Menu" button various operation modes can be selected. The button "Measure" initiates measurements and is to be pressed at the first and second measuring points for ordinary measurements of distance, and is to be pressed for each measuring point alongside an object to be measured to acquire surface area, and volume. Thus, for example, to measure the volume of a rectangular box, the button is pressed first as the measuring point of the instrument is at one corner of the box, which is illustrated in fig. 6, (1). The button is pressed a second time as the measuring point of the instrument is at a second corner as the length of the box is displayed (3). After moving the instrument perpendicularly to the first and second move, the button is pressed a third time as the measuring point of the instrument is at a third corner as the surface of the box is displayed (4), and finally after moving the instrument once again perpendicularly to both other movements, the button is to be pressed a fourth time as the measuring point of the instrument is at the corner most far away from the starting point (5). The volume of the box will then be displayed. At this point, by use of the "Menu" button, the box' diagonal lengths can be displayed (6). At another press of the "Menu" button, the box' surface areas can be displayed.

The diagonal is also calculated and displayed when a flat surface area is measured as described above.

By means of the derived acceleration values and an algorithm, the display can continuously show room coordinates as X-Y-Z after the first press of the "Measure" button as described if Fig. 6 (2). At this point, the speed of the instrument's movement can be displayed, as this is calculated as single integration of acceleration. A remote cable can be connected to the instrument. Said cable can be used to remotely press the "Measure" button. This is very useful when the height of inaccessible windows are measured, from a roof (or ladder) or as the instrument is lowered down a well, the measurement also can be made without the necessity of immediate access to the instrument.

The instrument is capable of using a multiple of algorithms and calculations. Measurement of one area can be related by another measured area. The result of dividing these two areas can be displayed.

By use of the "Menu" button, settings can be made to change user language, units (ISO/Imperial etc.) The main function of the "Menu" button is to switch between function modes as described below.

Examples of uses:

Distance: Measurements for carpentry work, etc. Measuring distances between posts to be erected (fencing) and distance between plants for gardening. In the latter example an audio signal indicating a preset distance is useful for repeated positioning.

To measure the depth of a well (to the water level) a remote cable is used for the "Measure" button. The instrument can be lowered into the well or down from a roof etc. by means of the cable.

Coordinates: After the first press of the "Measure" button the room coordinates can be continuously displayed from the starting point. This is useful when making an estimate where to drill through a wall, flooring, leveling, plantations etc. In this phase of use of the instrument, its speed can be displayed.

Area: To measure a square surface area, the lengths of the two sides are measured by the press of the "Measure" button a third time at the end of the second side of the area to be measured. The diagonal is also calculated. This is useful for gardening, farming, calculation of paint needed and house or apartment area for real estate sales. Combined length: In this measurement mode, the second, third etc. pressing of the "Measure" button does not result in calculations of area, volume etc., but sums up lengths for each pressing to be made as the measurement path makes any turn. This is for measuring length for cables to install, plumbing or the length of a walk path. Any measurement of any length along a surface is possible such as the circumference of a tree, a confined small forest area or envelope.

Polygons: This measurement function is a combination of Combined length and Area: The "Measure" button is pressed at a starting point. Thereafter it is to be pressed every time the instrument is moved in a new direction in one plane. The measurement is terminated by pressing the "Measure" button a prolonged time, and the surface of the measured polygon is displayed.

Volume: A function to measure boxes for shipping, excavations, in forestry, pallets, volume of goods for sale (such as sand) etc. Useful for the transport industry such as estimating residual load capacity of a truck.

Volume of spheres: By measuring the radius or diameter of a sphere, the surface area and volume of the sphere is displayed.

Tracking: In this mode , as the radius or diameter is defined, the instrument can be used in a fashion resembling "Coordinates" previously described: As the instrument is moved, the deviations from a circle - or other predefined shape - can be indicated on the display for tracking along a line of that shape. Useful when drawing circles in carpentry work, defiiiing where to dig to make a well or a circular pool.

Volume of cubes: By measuring the length of a cube, the surface area, diagonals and volume of the cube is displayed.

Volume of cylinders: By measuring the radius or diameter and length of a cylinder, the surface area and volume of the cylinder is displayed. Tiles: Measurement of the necessary quantity of tiles needed for a defined area. It is, under this menu function, possible to measure one tile for reference and thereafter the area to be tiled, and thus obtain the quantity of tiles. Useful for roof or kitchen tiles or for gardening.

Height of buildings can be measured by pointing at the top of the roof alongside the instrument for reference, at approximately a 45 degree angle, and then by walking to the base of the building (mast, tree....) and press the "Measure" button again.

Distance by scale: A map or drawing ratio can be set on the instrument. The instrument can be used to measure directly on maps, drawings etc. For example, the result would be 5 kilometers for a measurement of actual 100 mm on a map with a scale of 1:50000.

Options:

Measurements taken can be stored in the instrument for later retrieval and optionally further measurements.

For industrial applications, the instrument can be equipped with infrared, cable or radio transfer (for instance a Bluetooth™ technology) of data to or from a central storage or billing system.

The instrument can be equipped with a bar code reader, and means to store the data from said reader. Furthermore, the instrument can utilize software to execute calculations based on data from said reader, or transfer data over data transfer function mentioned above.

The instrument can be equipped with a speech circuit, with associated software functions, for the visually impaired.

The instrument can be equipped with a buzzer, or similar, to indicate low battery, when the instrument is moved to a preset distance, when the instrument is moved to a preset coordinate (for leveling etc.), when a button is pressed, or similar function. Also, tips for the measuring reference point to measure from can be replaced for different types of access. A light spot can be used for reference point in some cases.

The instrument can be programmed by the user for left-hand use.

One can even consider to arrange the sensors in a separate small and easily moveable body connected by wire, wireless or optically to the instrument. The instrument could in this case actually be a computor, in particular a hand held computor.

As is apparent from above the invented instrument is very versatile and the list of what it can not do is by far shorter than the list of what it can do.

Claims

1. A distance measuring instrument characterized in that, it comprises, acceleration measuring sensors such as accelerometers measuring acceleration and a calculation unit calculating from the acceleration values the traveled distance, that can then be indicated on a display.

2. Instrument according to claim 1, characterized in that it comprises a battery and is hand held.

3. Instrument according to claim 1 or 2, characterized in that a plurality, preferably three acceleration measuring sensors are arranged each at a plurality, preferably three, different locations in the instrument, or attached to it, or connected to it.

4. Instrument according to claim 1 or 2, characterized in that a three-axis acceleration measuring sensor is located in the instrument, or attached to it or connected to it.

5. Instrument according to claim 1, 2, 3, or 4 characterized in that it is provided with a memory means and that the calculation unit is programmed so that the direction of gravity in relation to the instrument is calculated and memorized so as to allow compensation for gravity while initializing measurement, measuring and terminating measurment, and programmed to continuously calculate the instrument's angles to gravity and to calculate the instrument's angle in relation to the direction of movement while measuring.

6. Instrument according to claim 1, 2, 3, or 4 characterized in that it is provided with a memory means and that the acceleration measuring sensors are suspended in such a way that they always have the same direction in relation to the force of gravity, and a transducer signaling the turning of the instrument or the housing for the acceleration measuring sensors around the vertical axis, and that the calculation unit is programmed to continuously calculate the instrument's angle of rotation around the vertical axis and the direction of movement while initializing measurement, measuring and terminating measurement.

7. Instrument according to claim 5 or 6, characterized in that the instrument has means to calculate area, volumes, body surface areas and diagonals by utilizing distance measurements.

8. Instrument according to claim 5 or 6, characterized in that the instrument has means to calculate a sum of distances by utilizing a plurality of distance measurements.

9. Instrument according to claim 5 or 6, characterized in that the instrument has means to continuously calculate room coordinates and points along predefined lines or geometrical shapes from an originating point.

10. Instrument according to claim 5, 6, 7, 8 or 9, characterized in that the instrument has software means to alternate measuring functions, algorithms, settings and the display of function descriptions by use of panel buttons.

11. Instrument according to claim 10, characterized in that the instrument has several detachable protruding points that can be defined as measuring reference by utilizing a plurality of calculation algorithms therefor, and sighting means to point the instrument at a target for measuring.

12. Instrument according to claim 10, characterized in that the instrument is furnished with a data transfer unit, utilizing wire, radio or infrared data transfer for data and settings of the instrument and software means therefor.

13. Instrument according to claim 12, characterized in that the instrument is furnished with a bar code reader and software means therefor.

14. Instrument according to claim 10, characterized in that the instrument has a buzzer and a speech circuit, and software means therefor.

15. Instrument according to claim 10, characterized in that the instrument has software to calculate and display the instrument's speed while measuring.

16. Method for calibration of the instrument according to claim 5 or 6, characterized in that the instrument is moved a well known exact distance from its original position, if a different position is calculated by the instrument, corrected calibration factors are stored in the instrument's memory, to be used to correct the mathematical expressions used for calculations.

17. Method for calibration of the instrument according to claim 5 or 6, characterized in that the instrument is rotated in all three geometrical axis from its original position, if a different angle is calculated by the instrument, corrected calibration factors are stored in the instrument's memory, to be used to correct the mathematical expressions used for calculations