FIELD OF THE INVENTION

This invention relates generally to the field 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

In recent years many individuals have turned to their own fitness 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 purportedly increases cardiopulmonary fitness, helps to lower blood pressure, decreases cholesterol and triglyercides associated with heart disease and reduces weight Jogging is also one ofthe 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 U S Pat No 3,540,344 to Veech and TJ S Pat No

SUBSTTΓUTE SHEET (RULE 26)

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 ofthe individual jogger

There are other running aids known in the prior art such as pedometers as disclosed in U.S. 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 U.S. 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 U.S. 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 deficient in several areas

For example, while ultra sound devices can measure the distance between two feet, this is not equivalent to the length of a step or a stride, which is defined as the distance traveled by the same foot from the beginning of a stride till the end ofthe same stride. For example, the difference 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 significant errors in measuring stride length. It is known that above a certain speed, stride length begins to increase as speed increases, and the relationship of stride length to speed is not directly proportional, and moreover, is different for each runner. In addition, most ofthe 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 difficult 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 ofthe prior art includes a measurement of height jumped Running and walking aids known in the prior art are often deficient and cumbersome to use and they often add weight to the runner or walker while providing only marginal utility in terms ofthe 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 ofthe prior art devices and substantially increases the amount and accuracy of information available to the jogger

A specific objective of this invention is to provide a new and improved running and walking measuring system, in which the speed ofthe runner can be easily and accurately determined

A further specific 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 specific 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 determined.

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.

SUMMARY OF THE INVENTION

In accordance with one aspect ofthe invention, a device for measuring the performance ofa runner utilizes accelerometers and rotational sensors to measure the speed, distance traveled, and height jumped of a person. It may be preferably placed in the sole ofa shoe and information signals may be transmitted to the user's watch for display. An indication signal may be configured to reset measurement values to zero coordinates with each step taken, and the system records accelerations relating to the movement ofthe foot to the next step. The accelerations recorded are multiplied by appropriate cosine and sine values of angles of rotation ofthe foot, and integrated twice to obtain displacement of each step Time is incoφorated with the acceleration to perform the integration Once the length of steps is determined, the elapsed time is used to obtain the speed ofthe person, and the sum ofthe step lengths is used to obtain the distance traveled The maximum value ofthe 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 ofthe foot

According to another aspect ofthe invention, substantially satisfactory measurements may be obtained with two accelerometers and one rotational sensor; or the system may be attached to the top portion ofthe user's shoe, instead of installation inside the sole ofthe shoe.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion ofthe specification. The invention, however, both as to organization and method of operation, together with features, objects, and advantages thereof may best be understood 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 ofthe system's components in the sole of

the shoe, in accordance with an embodiment ofthe invention.

FIG 3 is a coordinate system for the reference frame ofthe stationary ground, and the vectors of linear and rotational motion that are necessary to determine motion ofthe foot in accordance with one embodiment ofthe invention FIG. 4 is a side view diagram ofthe foot during running, illustrating information employed to resolve step length in two dimensions in accordance with one embodiment ofthe invention.

FIG. 5 is a vector diagram illustrating output acceleration, velocity and displacement of one embodiment ofthe invention during running FIG. 6 is a block diagram ofthe 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 different components ofthe system as illustrated herein. The shoe ofthe 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 alternately be located at a remote site so that the performance ofthe runner can be monitored by another person Incoφorated into the receiving unit may be a microprocessor for processing the received signals into the speed ofthe 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 different components ofthe measuring system in the sole ofthe user's shoe . However, the invention is not limited in scope in this respect, and, various components ofthe system in accordance with the present invention may be implemented in a variety of arrangements Rotational sensors 4 and a contact switch 8 are preferably placed in the ball-of-the-foot portion ofthe sole

ofthe 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. Measuring system 10 may include three rotational sensors 4, each configured to measure the angle ofthe 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 corresponding 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 accelerometers 2, each configured to measure the acceleration ofthe 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 ofthe user's shoe. Accelerometers 2 are well known, such as those provided by Analog Devices model ADXL05. Each accelerometer may convert the measured 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 ofthe shoe. For example, the measuring system may be placed at another location of the shoe.

FIG. 3 illustrates a plot ofthe coordinate systems necessary to resolve step length and height. In the present context, a first coordinate system, such as (x,y,z)

22, is referred to as the reference frame coordinate system ofthe stationary ground. (Y _{x J} Y _y ) ^{are tne} rotational coordinates about x and y axis of the reference frame. In one embodiment ofthe invention, rotation about the z axis may not be measured. These values advantageously indicate the slope ofthe ground at the beginning ofthe step. Preferably, the reference frame coordinate system is reset at the initiation ofa

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 ofthe sole ofthe 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 z axis may be normal to the plane ofthe sole ofthe shoe The arrows in FIG 3 indicate the 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 ofthe linear accelerometers This coordinate system moves with the foot and may be centered at the location ofthe sensors FIG 3 further illustrates rotational coordinates , such as (θ _x ,θ _y ,θj about the axes X, Y and Z These rotational coordinates may be employed advantageously to keep track ofthe orientation ofthe (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 ofthe 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 indicated

FIG 4 illustrates an example of a motion ofthe foot and how the length ofthe step is resolved for a motion in one plane, along two dimensions (here, the plane ofthe 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 trajectory 29, as described in FIG 3 FIG 4 also illustrates acceleration vectors (Ax, Az) in the translational coordinate system These accelerations are represented by arrows aligned along the X and Z axes ofthe translation coordinate system, respectively The length ofthe arrows

represent the amount of acceleration for each component (30 and 32, respectively) The angle of rotation about the y axis relative to the reference frame coordinate system is θ _y 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 frame (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 ofthe foot For example, if motion remains in the (z,x) plane and the surface is hoπzontal (Fig 4), then

(1) ax = Ax cos θ _y + Az sin θ _y

(2) az = -Ax sin θ _y + Az cos θ _y + g

Where g is the acceleration due to gravity, which is preferably 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 Acceleration 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 effect of gravity For example, if the user ofthe system is standing still, θ _y = 0 and Az = -g, then az = 0 If the user is moving up at g, Az will read 0, and az = g If the user moves down at g and θ _y = 180, Az =-2g, and az =- g. For horizontal motion, for example, θ _y = 45°, Az and Ax would be positive and substantially equal from motion, but there would be an added negative g cos θ _y component added to Az and an added positive g sin θ _y component added to Ax, and their sum would be such that az = 0 The length ofthe 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 ofthe foot motion in three dimensions The reference frame is established from the foot contact at the beginning of a step 40 The reference frame z axis may

not be aligned with the direction of gravity if the ground (x,y plane) is not horizontal γ _y 42 is the angle ofthe x axis from the horizontal plane, and γ _x 44 is the angle ofthe y axis from the horizontal plane. These values are unknown, as they depend on the slope ofthe 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 determined from the linear accelerometers and rotational sensors in the translational coordinate system 46

(3) ax = Ax Cos θ y Cos θ z - Ay Cos θ x Sin θ z + Az Cos θ x Sin θy + g sin γ _y (4) ay = Ax Cos θ y Sιn θ z + Ay Cos θ x Cos θ z - Az Stn θ x Cos θ y + g sin γ„

(5) az = -Ax Sin θy Cos θ z + Ay Sin θx Cos θ z + Az Cos θ y Cos θ x + g cos γ _χ cos γ _y

As explained in reference with FIG 4, the terms involving gravity g counteract the accelerations in gravity recorded by the linear accelerometers The values for γ _x and y _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 accelerometer such as the ADXL05, from Analog Devices)

(6) γ _x = Sin-' (Ax/ g)

(7) γ _y = Sin-' (Ay/ g)

In order to assure accurate measurements, the accelerometers 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 ofthe earth, and provides a substantially constant value in a direction substantially aligned towards the center ofthe earth Therefore, an accelerometer 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 configured so as to advantageously reset the value generated by the accelerometers to substantially represent gravity, g, when the user's foot is resting on a surface. As such, the accelerometers employed in accordance with the present invention may remain substantially calibrated at all times.

Since the accelerometers and rotation sensors are connected 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:

(9) _Ly = j ay(t)dU

(10) Lz = Jj az(t)dt2

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 ofthe beginning of the step, and would be significant if a person, for example, climbed a step. To obtain the length ofthe step,

The maximum height H jumped is,

(12) H = ax(Lz)

FIG. 6 is a block diagram ofthe components employed to solve the equations, although the invention is not limited in scope in this respect. Therefore, any hardware or software system configured 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 filters (not shown) Such filters may be used to reduce high frequency components in measured acceleration signals The linear accelerometers are configured to measure accelerations in three dimensions, along the direction ofthe foot as it travels during each step

Unit 50 may preferably contain rotational sensors employed to measure θxθy and θz signals. Thus the rotational sensors provide the angle of rotation along each axis ofthe translational coordinate. The output terminals of units 48 and 50 are coupled to input terminals ofa 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 ofthe invention, processor 52 may process the received signals digitally by employing an analog to digital converter and a microprocessor that calculates equations, 3-7 Yet, In accordance with another embodiments ofthe invention, the output 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 1 In another embodiment of the invention, analog to digital converter 54 may be part of microprocessor 56, such as one provided by Motorola MC68HC11E9

Microprocessor 56 is preferably configured to measure the distance L traversed after each step and the maximum height H jumped during that step. It will be appreciated that these measurements may be employed in either analog or digital format.

In accordance with one embodiment ofthe invention, a foot switch (not shown) may be employed so as to reset the accelerometers and rotational sensors contained in units 48 and 50, when the user's shoe contacts the ground Information relating to the length and height ofa step, and the contacts with ground may then be transmitted by transmitter 58 to a remote receiver unit 60 However, the invention is not limited in scope in this respect For example, instead of a foot switch, the

accelerometers or the rotational sensors may be configured to reset themselves, whenever their 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 microprocessor 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 ofthe type already known in the art such as the RF Monolithics model HX2000. Transmitter 58 may operate on any frequency selected amplitude or frequency modulation The transmitted signal from transmitter 58 is received and decoded by receiver 62. Receiver

62 may also be ofthe 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 different transmitters operating on different 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

MC68HC05L1.

A typical run mode sequence will now be described with reference to FIG.6. Mode select unit 66 is employed at the start ofthe 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 ofthe runner comes into contact with the surface, a first output signal is generated by accelerometers contained in unit 48 representing that a foot ofthe runner is in contact with the surface. Unit 52 begins to calculate the initial location ofthe 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 ofthe user's foot along the translational coordinate system. Thereafter, unit 52 measures instantaneous acceleration of the foot along the reference 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 ofthe 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 ofa microprocessor to signals suitable to drive display 68

Speed is continuously calculated by measuring the distance of each step and is instantaneously available for display. Microprocessor 64 also maintains running elapsed time Microprocessor 64 may be configured to calculate distance traversed by summing the length of all steps taken. It may further be configured to calculate the instantaneous and the average speed ofthe 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 read only memory (not shown) associated with microprocessor 64 for virtually an indefinite period of time

For calibration puφoses, microprocessor 56 may be desirably configured 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, microcontroller 56 may provide a feedback signal so as to reset the values ofthe accelerometers to provide a desired signal representing gravity, g.

In the watch mode, microprocessor 64 selectively provides to display 68, normal watch functions such as time of day, date, an alarm signal when a preselected time occurs. Obviously, many modifications and variations ofthe above preferred embodiment ofthe invention will become apparent to those skilled in the art from a reading of this disclosure For example, a less expensive embodiment may be implemented where all electronic components are disposed on the shoe In that case, there may be no desire for a transmitter and a receiver circuit It may also be possible to combine the functions performed by microprocessors 56 and 64 into one microprocessor, such as a Motorola model MC68HC05L In the alternative it is also possible to combine the functions performed by signal processor 52, and microprocessors 56 and 64 into one such microprocessor

It should be realized that the invention is not limited to the particular

embodiment disclosed, but its scope is intended to be governed only by the scope of the appended claims