Umted States Patent [19]
`Hutchings
`
`[11] Patent Number:
`[45] Date of Patent:
`
`5,724,265
`Mar. 3, 1998
`
`[54] SYSTEM AND NIETHOI) FOR MEASURING
`MOVEMENT 0F OBJECTS
`
`[76] Inventor: Lawrence J. Hntchings. 18729 Brickell
`Way Castro Valley Calif. 94546
`’
`'
`
`[21] Appl. No: 570,759
`,
`Dec- 12’ 1995
`[22] Flled‘
`[51] Im, c1.6 ................................................... .. G01C 22/00
`[52] US. Cl. ........................ .. 364/565; 364/410; 364/561;
`340/323 R; 235/105
`
`7/1991 Kato et a1, ............................ .. 364/561
`5,033,013
`5/1992 Sutton et a1. .
`377/242
`5,117,444
`4/1993 Hoyt et al. . . . .
`. . . .. 342/52
`5,206,652
`9/ 1993 Barber ----- --
`- 364/410
`5,245,537
`3/1995 Wilson ..
`372/38
`5,396,510
`9/1995 Mounce
`. 364/449
`5,452,216
`5,471,405 11/1995 Marsh
`. 364/556
`5,516,334
`5/1996 Easton
`..... .. 482/8
`5,524,637
`6/1996 Erickson
`128/779
`5,574,669 11/1996 Marshall
`364/569
`5583776 12/1996 Levi at al- ---------------------------- -- 364/450
`FOREIGN PATENT DOCUMENTS
`
`
`
`364/410 449 , , ................................... .. [58] Field of Search 364/450, 561, 565. 569. 556, 559, 143,
`
`
`
`
`
`
`
`
`
`_ iapan ........................... .. apan 60200119 10/1985 J
`
`
`
`
`
`
`
`G01C 22/00
`
`443, 460; 128/670, 779; 482/3,_ 3, 74, 902;
`342/52; 324/171; 340/384.71, 323 R; 377/24,
`242; 73/490; 235/105
`
`1
`
`[56]
`
`_
`References cued
`U.S_ PATENT DOCUMENTS
`
`02121219 12/1983 United Kingdom ......... .. G01C 22/00
`
`apan ....................... ..
`
`OTHER PUBLICATIONS
`Britting, Kenneth R., Inertial Navigation Systems Analysis,
`Wiley-Interscience, A of John Wiley & Sons, Inc., pp. 1-10,
`156-163 (1971, Library of Congress, No. 70-168635).
`
`3,789,402
`3,797,010
`
`1/1974 Heywood et a1. .
`3/1974 Adler et al.
`
`340/38471
`.. 340/323 R
`
`(List Continued 011 1191911489)
`Primary Examiner_JaIncS R Tr
`611
`
`3,865,305
`
`2/1975 Sampey . . . . . .
`
`. . . . . . .. 377/24 .
`
`.
`
`.
`
`4,053,755 10/1977 Sherrill ......... ..
`4,094,199
`6/1978 Holdren et a1.
`4,180,726 12/1979 DeCrescent
`4,220,996 9/1980 Searcy
`4,312,358
`1/1982 Barney ----- "
`2221i:
`maizzlvskl '
`4’387’437
`6/1983 Low: ei
`4’449’191
`5/1984 Meme}; ____
`4:46O:823 7/1934 Ruehlmm
`4,560,361 12/1985 Kato et a1_ _
`4,571,680 2/1986 Wu ........... ..
`4,573,769
`3/1936 Fredelick ----- -.
`4,627,011 12/1935 Spencer 6'1 a1~
`4,630,226 12/1936 Tanaka ----- "
`Easier
`4,1988 Miss er
`4’741’0O1
`8/1988
`4:763:237
`4,821,218 4/1989 Potsch ...... ..
`4,855,942
`8/1989 Bianco ..... ..
`4,885,710 12/1989 Hersberger et a1.
`
`'
`
`'
`
`.. 364/561
`. 73/517 B
`250/222 R
`364/561
`123/670
`
`364561
`364,559
`235/105
`235/105
`364/410
`3641565
`364/566
`364/561
`
`377,24 2
`364/56'1
`. 364/566
`364/561
`........ .. 364/565
`
`Asm’a’" Em‘"e’—§3“°ng H' Nguyen
`Attorney, Agent, 0' Flrm—S0fer & HaIOHH, LLP
`
`ABSTRACT
`[57]
`A device that measures the distance traveled. speed, and
`height jumped of a person while running or walln'ng. Accel
`erometers and rotational sensors are placed in the sole of one
`shoe along with an electronic circuit that performs math
`ematical calculations to determine the distance and height of
`each step. A radio frequency transmitter sends the distance
`and height information to a wristwatch or other central
`receiving unit. A radio frequency receiver in the wristwatch
`or other unit is coupled to a microprocessor that calculates
`an output speed based upon step-distance and elapsed time,
`and the distance traveled of the runner from the sum of all
`previous step distances. The output of the microprocessor is
`coupled to a display that shows the distance traveled. speed,
`of h?ight jumpcd 0f the runner of Walker
`
`22 Claims, 5 Drawing Sheets
`
`/////////////////////////////
`
`1
`
`

`

`5,724,265
`Page 2
`
`OTHER PUBLICATIONS
`
`Goldstein, Herbert. Classical Machanics, Ch. 4,pp.
`124-132, Addison Wesley Publishing, Reading, MA 1956.
`
`Van Bronkhorst. A., Euler Angle Strapped-Down Computer,
`Advisory Group for Aerospace Research and Development
`(AGARD), Inertial Navigation Systems and Components,
`pp. 253-257 North Atlantic Treaty Organization, May 1968.
`
`Casio product, “JC-lO-IBV Jog & Walk Calorie”. Web site,
`http://www.starnetinc.comlglobalproducts/casio/
`jc10lbv.html, 1997.
`Airline International Home Page, “Electronic Pedomete ”,
`httpJ/www.ishops.comlairline/el-ped.html_ 1997.
`Meijer. et a1. “Methods to Assess Physical activity with
`Special Reference to Motion Sensors and Accelerometers”,
`IEEE Trans. on Biomedical Engineering, Vol.38, No.3. Mar.
`1991.
`'
`
`2
`
`

`

`US. Patent
`US. Patent
`
`Mar. 3, 1993
`Mar. 3, 1998
`
`Sheet 1 0f 5
`Sheet‘ 1 of 5
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`5,724,265
`5,724,265
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`FIG. 2
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`4
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`8
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`3
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`US. Patent
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`Mar. 3, 1998
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`Sheet 2 of 5
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`5,724,265
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`FIG. 3
`
`Z
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`ez
`
`Z
`
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`US. Patent
`US. Patent
`
`Mar. 3, 1998
`Mar. 3, 1998
`
`Sheet 3 of 5
`Sheet 3 of 5
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`5,724,265
`5,724,265
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`FIG. 4
`FIG. 4
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`5
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`

`US. Patent
`US. Patent
`
`Mar. 3, 1998
`Mar. 3, 1998
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`Sheet 4 of 5
`Sheet 4 or 5
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`5,724,265
`5,724,265
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`FIG. 5
`FIG. 5
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`6
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`US. Patent
`
`Mar. 3, 1998
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`Sheet 50f 5
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`5,724,265
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`5,724,265
`
`1
`SYSTEM AND METHOD FOR MEASURING
`MOVEMENT OF OBJECTS
`
`FIELD OF THE INVENTION
`
`This invention relates generally to the ?eld of measuring
`instruments and is particularly directed to a system and
`method for determining the speed, distance traversed, and
`height jumped by a person while running or walking.
`
`BACKGROUND OF THE INVENTION
`
`10
`
`2
`two feet, this is not equivalent to the length of a step or a
`stride, which is de?ned as the distance traveled by the same
`foot ?'om the beginning of a stride till the end of the same
`snide. For example, the diiference between (1) separation
`between feet. as measured by the ultra sound device. and (2)
`stride length, is different for each person and will vary for
`different speeds of running.
`Furthermore, devices that employ elapsed-foot-contact
`time measurements, have signi?cant errors in measuring
`stride length. It is known that above a certain speed, stride
`length begins to increase as speed increases. and the rela
`tionship of stride length to speed is not directly proportional,
`and moreover, is dilferent for each runner. In addition, most
`of the devices mentioned above require calibration, which
`may prove to be a difficult task. For example, many of these
`devices need to be calibrated by the manufacturer or by
`specially designed equipment.
`It is, therefore. a di?icult task to determine the correct
`stride length for an individual runner at various speeds.
`Thus. pacing timers can provide no more than a constant
`running pace, and pedometer measurements are only useful
`as an approximation of distance traversed. Also, ultra sound
`and elapsed-foot-time-distance devices provide only a rough
`approximation of actual distance traveled and speed of the
`person. Also, none of the prior art includes a measurement
`of height jumped. Running and walking aids known in the
`prior art are often de?cient and cumbersome to use and they
`often add weight to the mnner or walker while providing
`only marginal utility in terms of the amount of information
`available and its accuracy.
`With the foregoing in mind, the ideal running aid should,
`therefore: be light in weight; serve a number of useful
`functions; be inexpensive; provide measurements that are
`readily available to the user; be reliable and easy to use; and
`provide accurate measurements of speed, distance traversed.
`height jumped, and other useful information.
`
`OBJECT OF THE INVENTION
`
`It is the overall objective of this invention to provide a
`new and improved running and walking measuring system,
`which overcomes the disadvantages of the prior art devices
`and substantially increases the amount and accuracy of
`information available to the jogger.
`A speci?c objective of this invention is to provide a new
`and improved running and walking measuring system, in
`which the speed of the runner can be easily and accurately
`determined.
`A further speci?c objective of this invention is to provide
`a new and improved running and walking measuring system,
`in which the distance traversed by the runner can be easily
`and accurately determined.
`Another speci?c objective of this invention is to provide
`a new and improved running measuring system, in which the
`height jumped by the runner or jogger can be easily deter
`mined.
`A still further objective of this invention is to provide a
`new and improved running and walking measuring system
`having the above advantages which is light in weight.
`relatively inexpensive and convenient to use.
`
`In recent years many individuals have mined to their own
`?tness program of regular jogging. As used herein, jogging
`is also intended to include running and walking and the
`words are used interchangeably. Jogging has long been
`recognized for its therapeutic effects on the body. It pur
`portedly increases cardiopulmonary ?tness, helps to lower
`blood pressure, decreases cholesterol and triglyercides asso
`ciated with heart disease and reduces weight. Jogging is also
`one of the easiest exercises to do. It requires no athletic
`ability and can be done almost any time and any place with
`a minimum of equipment and without assistance. In more
`recent times, jogging has also gained acceptance for its
`recreational value as well and is recognized as a positive
`factor in promoting psychological well-being.
`The popularity of jogging today is well documented by
`the large numbers of products and literature available to the
`public. As in many exercise and sporting endeavors, there
`exists in the prior art a wide variety of devices for aiding
`those who jog. Many people who run. jog or walk regularly
`desire to know their progress over time. Therefore. it is
`desirable to know the accurate distance and speed traveled
`during an exercise session. This information allows a jogger
`to monitor his or her progress and accordingly pursue a
`regular course of exercise designed to enhance performance.
`Further. it has become desirable to accurately measure the
`speed of amateur and professional runners, both in training
`and during competition. In the prior art, such measurements
`were made with a stop watch timing the runner over a known
`distance. Heretofore, it has not been possible to obtain
`accurate instantaneous speeds of runners or height jumped
`using the measuring devices currently known in the prior art.
`The simplest jogging aids for measuring movements are
`basic pacing timers such as those disclosed in US. Pat. No.
`3,540,344 to Veech and US. Pat. No. 3.882.480 to Greber.
`Pacing timers generate a repetitive audio tone signal at
`selected intervals for pacing the strides of the jogging, where
`the length of the interval between tones is adjusted to suit the
`pace of the individual jogger.
`There are other running aids known in the prior art such
`as pedometers as disclosed in US. Pat. No. 4,053,755 to
`Sherrill. These devices usually count the number of steps
`taken and for a particular stride length, the approximate
`distance traversed can be determined.
`Human speedometers and odometers that measure the
`speed and distance traveled by a person include devices that
`utilize ultrasound to measure the distance between each foot
`such as disclosed in US. Pat. No. 4.736.312 to Dassler. Also
`used is a device that measures the elapsed time of shoe in
`contact with the ground and converts this to the length of
`step and speed as disclosed In US. Pat. No. 4,578,769 to
`Frederick.
`While pacing timers. pedometers, ultra sound, and
`elapsed foot-time-distance devices are useful to the runner
`and walker. they are de?cient in several areas. For example.
`while ultra sound devices can measure the distance between
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`SUMMARY OF THE INVENTION
`
`65
`
`In accordance with one aspect of the invention, a device
`for measuring the performance of a runner utilizes acceler
`ometers and rotational sensors to measure the speed. dis
`tance traveled. and height jumped of a person. It may be
`
`8
`
`

`

`5,724,265
`
`3
`preferably placed in the sole of a shoe and information
`signals may be transmitted to the user’s watch for display.
`An indication signal may be con?gured to reset measure
`ment values to zero coordinates with each step taken. and the
`system records accelerations relating to the movement of the
`foot to the next step. The accelerations recorded are multi
`plied by appropriate cosine and sine values of angles of
`rotation of the foot. and integrated twice to obtain displace
`ment of each step. Time is incorporated with the acceleration
`to perform the integration. Once the length of steps is
`determined. the elapsed time is used to obtain the speed of
`the person. and the sum of the step lengths is used to obtain
`the distance traveled. The maximum value of the vertical
`displacement is used to determine the height jumped. One
`set of three-component linear accelerometers and one set of
`three-component rotational sensors are necessary to fully
`resolve the absolute motion of a person from the motion of
`the foot.
`According to another aspect of the invention. substan
`tially satisfactory measurements may be obtained with two
`accelerometers and one rotational sensor; or the system may
`be attached to the top portion of the user’s shoe, instead of
`installation inside the sole of the shoe.
`
`15
`
`20
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`25
`
`The subject matter regarded as the invention is particu
`larly pointed out and distinctly claimed in the concluding
`portion of the speci?cation. The invention. however. both as
`to organization and method of operation. together with
`features. objects. and advantages thereof may best be under
`stood by reference to the following detailed description
`when read with the accompanying drawings in which:
`FIG. 1 illustrates one embodiment of the invention as
`employed by a user.
`FIG. 2 illustrates the location of the system’s components
`in the sole of the shoe. in accordance with an embodiment
`of the invention.
`FIG. 3 is a coordinate system for the reference frame of
`the stationary ground. and the vectors of linear and rotational
`motion that are necessary to determine motion of the foot in
`accordance with one embodiment of the invention.
`FIG. 4 is a side view diagram of the foot during running,
`illustrating information employed to resolve step length in
`two dimensions in accordance with one embodiment of the
`invention.
`FIG. 5 is a vector diagram illustrating output acceleration.
`velocity and displacement of one embodiment of the inven
`tion during running.
`FIG, 6 is a block diagram of the electronic units necessary
`to solve equations for step length in accordance with the
`invention.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`FIG. 1 shows an embodiment of a measuring system 10
`as employed by a user. although the invention is not limited
`in scope to the location of diiferent components of the
`system as illustrated herein. The shoe of the user may
`include interrelated elements such as linear accelerometers;
`rotational sensors; a microprocessor to calculate the distance
`and height of each step; a foot impact switch; battery; and a
`radio transmitter 12. as will be explained in more detail
`below.
`As shown in FIG. 1. the user may wear a hand display
`having a radio receiver 14. The radio receiver may alter
`
`4
`nately be located at a remote site so that the performance of
`the runner can be monitored by another person. Incorporated
`into the receiving unit may be a microprocessor for proces 5
`ing the received signals into the speed of the runner. the
`distance traversed and the height jumped. The processed
`information may be selectively displayed on display 18. The
`hand display may also perform other functions. for example.
`it may selectively display normal Watch functions, such as
`time of day, date, alarm and stop watch signals.
`FIG. 2 shows one possible location of di?erent compo
`nents of the measuring system in the sole of the user’s shoe.
`However. the invention is not limited in scope in this
`respect. and, various components of the system in accor
`dance with the present invention may be implemented in a
`variety of arrangements. Accelerometers 2. rotational sen
`sors 4, and a contact switch 8 are preferably placed in the
`ball-of-the-foot portion of the sole of the shoe so that they
`may come in contact with the ground for each step during
`either walking or running. As it will explained in more detail
`below. the measuring system in accordance with the present
`invention may also operate without contact switch 8. Mea
`suring system 10 may include three rotational sensors 4.
`each con?gured to measure the angle of the user’s foot with
`respect to a reference frame as will be explained in more
`detail below. Rotational sensors 4 are well known. such as
`those provided by AMP model numbers ACH-04-08. Each
`rotational sensor converts the measured angle into a corre
`sponding signal. which is employed by a microprocessor 6
`to calculate information related to the user’s movements.
`such as user’s speed. distance traveled and the height
`jumped. It will be appreciated that the present invention is
`not limited in scope to the components illustrated in FIG. 2.
`For example. instead of contact switch 8. other means may
`be employed so as to generate a signal to indicate the
`beginning of each step.
`Measuring system 10 preferably includes three acceler
`ometers 2. each con?gured to measure the acceleration of
`the user’s foot with respect to a reference frame as will be
`explained in more detail below. The accelerometers may
`also be located in the sole of the user’ 5 shoe. Accelerometers
`2 are well known. such as those provided by Analog Devices
`model ADXLOS. Each accelerometer may convert the mea
`sured acceleration into a corresponding signal. which may
`be preferably employed by microprocessor 6 to accomplish
`movement measurements.
`Also, other components may be separated and placed in
`another portion of the shoe. For example. the measuring
`system may be placed at another location of the shoe.
`FIG. 3 illustrates a plot of the coordinate systems neces
`sary to resolve step length and height. In the present context.
`a ?rst coordinate system. such as (x,y.z) 22. is referred to as
`the reference frame coordinate system of the stationary
`ground (Y,,. Yy) are the rotational coordinates about x and
`y axis of the reference frame. In one embodiment of the
`invention. rotation about the z axis may not be measured.
`These values advantageously indicate the slope of the
`ground at the beginning of the step. Preferably. the reference
`frame coordinate system is reset at the initiation of a new
`step and remains stationary throughout the time the same
`foot leaves and touches the ground again. ‘The orientation of
`the reference frame coordinate system with respect to the
`foot is arbitrary, but it is preferably selected so that at the
`beginning of the step the positive x direction may be aligned
`with the axis of the sole of the shoe. the positive y axis may
`be in the same plane as the sole and at right angles to the x
`axis. and the positive 2 axis may be normal to the plane of
`the sole of the shoe. The arrows in FIG. 3 indicate the
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
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`‘5,724,265
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`6
`stantially equal from motion. but there would be an added
`positive g cos 9, component added to Az and an added
`negative g sin 9y component added to Ax. and their sum
`would be such that az=0. The length of the step is obtained
`by integration as discussed in reference with FIG. 5.
`FIG. 5 shows the elements that may be employed to
`obtain a complete solution of the foot motion in three
`dimensions. The reference frame is established from the foot
`contact at the beginning of a step 40. The reference frame 2
`axis may not be aligned with the direction of gravity if the
`ground (x,y plane) is not horizontal. yy 42 is the angle of the
`x axis from the horizontal plane. and y, 44 is the angle of the
`y axis from the horizontal plane. These values are unknown.
`as they depend on the slope of the ground at the beginning
`of each step. and are calculated by measuring system 10. as
`explained below. At any point along the trajectory r, the
`components of motion in the reference frame can be deter
`mined from the linear accelerometers and rotational sensors
`in the translational coordinate system 46.
`
`10
`
`5
`direction of positive motion. The length and height of each
`step with respect to this coordinate system may be measured
`in accordance with the present invention as explained in
`more detail hereinafter.
`FIG. 3 also illustrates a second coordinate system. such as
`(X.Y.Z) 24. referred to as the translational coordinate system
`of the linear accelerometers. This coordinate system moves
`with the foot and may be centered at the location of the
`sensors. FIG. 3 further illustrates rotational coordinates,
`such as (erewez) about the axes X. Y and Z. These rotational
`coordinates may be employed advantageously to keep track
`of the orientation of the (X,Y.Z) coordinate system relative
`to the (x,y.z) coordinate system. as will be explained below.
`and to resolve the accelerations along the reference frame.
`In FIG. 3. an exemplary foot is shown part way through
`a step that moves along a trajectory r such as 25. The
`orientation of the translational coordinate system with
`respect to the foot is the same as described for the reference
`frame, but moves with the foot. Preferably, the reference and
`translational coordinate systems may be aligned together
`every time a new step is initiated.
`FIG. 4 illustrates an example of a motion of'the foot and
`how the length of the step is resolved for a motion in one
`plane. along two dimensions (here. the plane of the paper),
`and for a step along a horizontal surface. The reference
`frame coordinate system 26 is that described as 22 in FIG.
`3. and the translational coordinate system 28 is that
`described as 24 in FIG. 3. The foot is shown part way
`through a step having moved along trajectory r such as 29.
`The translational coordinate system is moving along trajec
`tory 29. as described in FIG. 4.
`FIG. 4 also illustrates acceleration vectors (Ax. A2) in the
`translational coordinate system. These accelerations are rep
`resented by arrows aligned along the X and Z axes of the
`translation coordinate system. respectively. The length of the
`arrows represent the amount of acceleration for each com
`ponent (30 and 32. respectively). The angle of rotation about
`the y axis relative to the reference frame coordinate system
`is 9y. From these components of motion the acceleration
`relative to the reference frame coordinate system can be
`resolved. This is shown as ax and az in the reference ?ame
`(34 and 36. respectively).
`The amount of acceleration and its direction (a vector
`solution) is preferably employed to keep track of forward
`and reverse motions of the foot. For example. if motion
`remains in the (z.x) plane and the surface is horizontal (FIG.
`4). then
`
`(4) ay=[Cos B, Cos 6). Sin 9z+Sin 9x Cos BJAx-[Sin 9, Cos 9,,
`Sin lit-Cos 9.. Cos 6, Cos 9_._]Ay+Sin 9, Sin OzAz
`
`(s) az=-cos a, Sin 9, Ax-Sin 9, Sin 0, Ay+Cos 9,.Az
`
`As explained in reference with FIG. 4. the terms involving
`gravity g counteract the accelerations in gravity recorded by
`the inertial linear accelerometers. The values for Y.‘ and y,
`may be determined at the initiation of each step. and are
`substantially equal to zero for a substantially horizontal
`surface. At this time the proportion of gravity recorded by
`the accelerometers is related. among other things, to the
`angle from the vertical coordinate (as resolved by an accel
`erometer such as the ADXLOS. from Analog Devices).
`
`In order to assure accurate measurements. the accelerom
`eters employed in the present invention are desired to be
`properly calibrated. The embodiments described herein may
`be conveniently calibrated in accordance with the present
`invention. This follows because gravity g only varies by less
`than 0.3% throughout the surface of the earth. and provides
`a substantially constant value in a direction substantially
`aligned towards the center of the earth. Therefore. an accel
`erometer employed in accordance with the present invention
`must generate an acceleration signal substantially equal to
`gravity g. when the user’s foot is resting on a surface. It will
`be appreciated that an embodiment in accordance with the
`present invention may be con?gured so as to advantageously
`reset the value generated by the accelerometers to substan
`tially represent gravity. g. when the user’s foot is resting on
`a surface. As such. the accelerometers employed in accor
`dance with the present invention may remain substantially
`calibrated at all times.
`Since the accelerometers and‘ rotation sensors are con
`nected to a timing device. their values may be known as a
`function of time. The horizontal and vertical displacement
`may then be obtained by integrating by time as they traverse
`the path:
`
`(a) apllmrw
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`35
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`40
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`45
`
`Where g is the acceleration due to gravity. which is prefer
`ably considered as a factor due to the use of accelerometers.
`Gravity may be assumed to be a constant as explained in
`more detail below. Here. acceleration az is assumed to be
`vertical and aligned with the orientation of gravity. Accel
`eration az may be aligned at an angle from the direction of
`gravity. such as on a hill, as explained in more detail below.
`The —g factor added to the az component of equation 2 is to
`balance the e?ect of gravity on an inertial linear accelerom
`eter. For example. if the user of the system is standing still.
`9 =0 and Az=+g. then az=0. Ifthe user is moving up at g. Az
`will read 2g. and az=g. If the user moves down at g and
`- 6y=l80. Az=0. and a2 —g. For forward horizontal motion. for
`example. 6y=45°. AZ and Ax would be positive and sub
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`

`5,724,265
`
`The integration is performed twice to obtain Lx, Ly. Lz
`shown in the equations. Lz would be zero if the ground
`remained at the slope of the beginning of the step, and would
`be signi?cant if a person. for example. climbed a step. To
`obtain the length of the step.
`
`(11)L= \iLx2+Ly2+ L12
`
`The maximum height H jumped is.
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`10
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`8
`output signal levels indicate that the user’s foot has touched
`the running surface again.
`Unit 60 is the remote device. which may be located in the
`user’s wrist watch. and contains a receiver 62. a micropro
`cessor 64, a mode select switch 66 and a display 68.
`Transmitter 58 includes a means for encoding the output
`signals provided by a microprocessor 56 into a transmitted
`signal. Transmitter 58 may also be of the type already known
`in the art such as the RF Monolithics model HX2000.
`Transmitter 58 may operate on any frequency selected and
`use amplitude or frequency modulation. The transmitted
`signal from transmitter 58 is received and decoded by
`receiver 62. Receiver 62 may also be of the type known in
`the prior art such as the RF Monolithics model RX2010.
`Receiver 62 may also be selectively tuned to receive the
`signals of several di?erent transmitters operating on differ
`ent frequencies so that the performance of several runners
`may be monitored from a remote location. Microprocessor
`64 may be selected from various microprocessors known in
`the prior art, such as Motorola model MC68HCO5L1.
`A typical run mode sequence will now be described with
`reference to FIG. 6. Mode select unit 66 is employed at the
`start of the run or jog by depressing an appropriate switch.
`not shown. which is coupled to microprocessor 64 through
`an input switch control logic interface. As the shoe of the
`runner comes into contact with the surface. a ?rst output
`signal is generated by accelerometers contained in unit 48
`representing that a foot of the runner is in contact with the
`surface. Unit 52 begins to calculate the initial orientation of
`the user’s foot along the reference coordinate in accordance
`with equations (6) and (7).
`Thereafter unit 48 generates acceleration signals along the
`translational coordinates. Rotational sensors contained in
`unit 50 begin to track the rotation of the user’s foot along the
`translational coordinate system. Thereafter, unit 52 mea
`sures instantaneous acceleration of the foot along the refer
`ence coordinates as the foot travels in the air and contacts the
`surface again. Unit 54 receives these acceleration signals
`and unit 56 calculates the length of each step by integrating
`the acceleration signals. Unit 56 also calculates the height
`jumped by obtaining the maximum length measured along
`the z axis of the reference coordinate system. The output
`signals are coupled to RF transmitter 58 and transmitted to
`receiver 62. The signals received by receiver 62 are coupled
`to microprocessor 64. The microprocessor interface converts
`the output of a microprocessor to signals suitable to drive
`display 68.
`Speed is continuously calculated by measuring the dis
`tance of each step and is instantaneously available for
`display. Microprocessor 64 also maintains running elapsed
`time. Microprocessor 64 may be con?gured to calculate
`distance traversed by summing the length of all steps taken.
`It may further be con?gured to calculate the instantaneous
`and the average speed of the user. The running elapsed time.
`the distance traversed and the speed may be selectively
`displayed on display 68. These values may also be stored in
`a non-volatile memory (not shown) associated with micro
`processor 64 for virtually an inde?nite period of time.
`For calibration purposes. microprocessor 56 may be desir
`ably con?gured to monitor the value of signals provided by
`accelerometers of unit 48. Whenever it is determined that the
`user’s foot is on the running surface. the value of these
`signals may correspond to gravity. g. If. however. the value
`of the these signals does not correspond to gravity. g.
`microprocessor 56 may provide a feedback signal so as to
`reset the values of the accelerometers to provide a desired
`signal representing gravity, g.
`In the watch mode. microprocessor 64 selectively pro
`vides to display 68. normal watch functions such as time of
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`20
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`25
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`FIG. 6 is a block diagram of the components employed to
`solve the equations. although the invention is not limited in
`scope in this respect. Therefore. any hardware or software
`system con?gured to solve the above equations to measure
`the length of each step and the height jumped may be
`employed. In FIG. 6. unit 48 may preferably contain the
`linear accelerometers employed to measure accelerations
`Ax. Ay and Az and frequency ?lters (not shown). Such ?lters
`may be used to reduce high frequency components in
`measured acceleration signals. The linear accelerometers are
`con?gured to measure accelerations in three dimensions.
`along the direction of the foot as it travels during each step.
`Unit 50 may preferably contain rotational sensors
`employed to measure 6x By and 92 signals. Thus the
`rotational sensors provide the angie of rotation along each
`axis of the translational coordinate. The output tenninals of
`traits 48 and 50 are coupled to input terminals of a processor
`52. Processor 52 may be employed to make the calculations
`necessary to solve equations 3-7 mentioned above. For
`example. the sine and cosine of each measured angle may be
`computed by processor 52. The sine and cosine value signals
`are then coupled to input terminals of unit 54.
`Unit 52 may contain multipliers and adder processors to
`solve equations 3-7 in analog format. In accordance with
`another embodiment of the invention. processor 52 may
`process the received signals digitally by employing an
`analog to digital converter and a microprocessor that calcu
`lates equations. 3-7. Yet. in accordance with another
`embodiments of the invention. the ouptut terminals of units
`48 and 50 may be coupled directly to a microprocessor 56.
`via an analog to digital converter 54. Analog to digital
`converter 54 may be a separate integrated circuit. such as
`one provided by Linear Technology LTC 10