Abstract:
An electronic pedometer to accurately measure stride length of a walker includes a processing unit with an ultrasonic sound wave receiver attached to one foot and an ultrasonic sound wave generator attached to the other foot. Pressure sensitive switches close when each foot makes a step, providing signals to the processing unit to record the number of strides. The processing unit computes stride length by calculating distances using the ultrasonic sound waves.

Description:
TECHNICAL FIELD 
     The technical field relates to pedometers and more particularly to a pedometer that can measure the distance a user walks or runs by accurately measuring the stride the user takes. 
     BACKGROUND 
     Pedometers have been in use for many years and most indirectly measure the distance traveled by the user by counting the number of steps taken. The user preprograms a stride distance into the device and then by calculating the number of strides taken multiplied by the predetermined stride length, a distance is recorded by the pedometer. Such pedometers have a drawback, however, in that during the course of a run or walk, the user may not take a stride which is equal to the preset stride distance. Accordingly, only a rough approximation of the distance traveled can be made by these pedometers. 
     In addition, prior art pedometers also rely on a number of techniques to count the number of steps taken by the user. Most of these techniques rely on a change in acceleration each time a user&#39;s foot contacts the ground. These changes are detected by a number of different acceleration sensitive devices. All of these devices rely on mechanical means to both count the number of steps or strides taken and to determine the distance of each stride. 
     These prior art pedometers have limitations which result in inaccurate data. For example, using the assumption that a stride length is constant results in errors in distance measurement because actual stride length may vary considerably as a function of the terrain traversed and the speed at which the user is traveling. 
     Further, the use of mechanical devices for sensing and counting steps is unreliable under the varied conditions of running, jogging and walking. 
     SUMMARY 
     In one embodiment an electronic pedometer is used to measure the stride length of a user. The pedometer has a first unit associated with one foot of the user including a pressure sensitive switch and a sound wave generator. The pedometer also includes a second unit associated with the second foot of the user including a pressure sensitive switch and a sound wave receiver. A processor is used to process sensed signals from each of the pressure sensitive switches and the sound wave generator. The processor is programmed to count each activation of the pressure sensitive switches and determines a point of maximum signal strength received from the sound wave generator. The processor also calculates the distance between the point of sensed maximum signal strength and the sound wave receiver, and the distance between activation of the pressure sensitive switch of the first unit and the last activation of the pressure sensitive switch of the second unit. The measurements calculated by the processor are used to calculate the stride length of the user. 
     In another embodiment a system is used to determine a distance traveled. The system uses an emitter for emitting a signal associated with one foot of the user and a signal sensor associated with the second foot of the user for receiving the emitted signal. The system also uses a processor for processing signals and calculating the stride length of the user. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The detailed description will refer to the following drawings, wherein like numerals refer to like elements, and wherein: 
     FIG. 1 illustrates a foot of a user with an embodiment of a processing unit in accordance with the present invention strapped to the ankle of the user; 
     FIG. 2 is a perspective view of an embodiment of an insole in accordance with the present invention provided with a pressure sensitive switch; 
     FIG. 3 is a plan view of the processing unit of FIG. 1; 
     FIG. 4 is a plan view of an embodiment of a ultrasonic sound generator in accordance with the present invention; 
     FIG. 5 is a diagrammatic view showing calculations of the distance traveled using the pedometer of the present invention; 
     FIG. 6A is a block diagram of an embodiment of the present invention illustrating the interaction of components of the pedometer; and 
     FIG. 6B is a flow chart of an embodiment of the present invention illustrating operation for determining distance traveled. 
    
    
     DETAILED DESCRIPTION 
     In operation, the electronic pedometer calculates stride length electronically. A pressure sensitive switch, which may be embedded in an insole, inserted in a shoe, or located in the shoe itself, is activated each time pressure is applied during a walk or a run. The pressure sensitive switch may be disposed under the balls of the user&#39;s foot so that each time pressure is applied by the weight of the user on the ball of the foot a signal is sent to an electronic recording device. The pressure sensitive switches may be disposed in each shoe of the user and are connected to receiving devices which may be attached to the shoe or strapped about the ankle of the user. 
     One of the pressure sensitive switches may be connected to a sound wave generator which continuously emits ultrasonic waves during use. The other pressure sensitive switch may be connected to a receiving device which includes, among other electronic circuitry, an ultrasonic wave receiver to receive the waves emitted by the other device. Each time the pressure sensitive device associated with the ultrasonic wave generator is closed by the application of pressure, the generation of the ultrasonic waves is interrupted and can be recorded. 
     The other pressure sensitive switch may be connected to a main processing component which includes an ultrasonic sound wave receiver and a processor which records each time the pressure sensitive switch associated with the left foot and the pressure sensitive switch associated with the right foot is activated. A temperature sensor is included in the processor, and based on the speed of sound which is dependent upon temperature, the stride length is calculated and displayed on the display module associated with the processor unit. 
     The pedometer may operate according to the following sequence: if the main processing unit is associated with the left foot when the pressure sensitive switch of the left foot closes, a signal is sent to the processor. Simultaneously, the ultrasonic sound generator associated with the right foot sends ultrasonic sound waves to the receiver in the processor which senses the strength of the signal. As the right leg moves forward, the ultrasonic sound generator attached on the right foot sends ultrasonic sound signals to the receiver and the strength of the signal increases until it is at a point directly opposite the receiver and then recedes in strength as the right leg continues in its forward path. As the right leg continues in its path, the signal recedes in strength, thus the processor senses the maximum signal strength and records this incidence. When the right foot is placed in contact with the ground surface, the pressure sensitive switch is activated and again this event is recorded by the processor. A temperature sensor is provided to account for the varying speed of sound. The distance between the right foot and left foot at the point of maximum single strength can be calculated as well as the distance between the right foot and the left foot when the pressure sensitive switch of the right foot is activated. With the distance between the feet being calculated when maximum signal strength is sensed and the distance between the left foot and the right foot at the maximum extension of the right foot also being calculable, the processor calculates the distance between the point of maximum signal strength and the point where the pressure sensitive switch associated with the right foot impacts the surface being walked. By doubling this distance, the stride length is accurately calculated. 
     The embodiments of the system, method and apparatus for measuring walking and running distance will now be described in detail with reference to the following figures. With reference now to FIGS. 1 and 2, the pedometer includes a processing unit  10  which may be strapped to the ankle  12  of a user by straps  14  and  16  which are provided at each end with hook and loop fastener, such as, for example, Velcro®, securing elements  18  and  20  (See FIG.  3 ). Alternatively, the processing unit  10  may be affixed in any convenient manner to laces  22  of the user&#39;s shoe  24 . 
     An insole  26 ,  28  for each shoe  24  is provided and includes a pressure sensitive switch  30 ,  32 , respectively, for each insole, connected by an electrically conductive conduit  34 ,  36 , respectively, for each shoe to a plug  38 ,  40 , respectively, for each shoe. The plugs  38  and  40  have electrically conductive prongs for insertion to their respective processing unit  10  or ultrasonic sound generator  42  (see FIG.  4 ). 
     FIG. 3 is a plan view of the processing unit  10  which can be strapped to the ankle of the user or to the shoe in any suitable manner. FIG. 4 is a plan view of the ultrasonic sound generator  42  which can also be strapped around the ankle of the user or to the shoe in any suitable manner. The plug  38 ,  40  is inserted into receptacle  44  on the processing unit  10  and into the receptacle  46  on the ultrasonic sound generator  42 . Ultrasonic sound generator  42  is also provided with straps  48  and  50  provided with hook and loop attachment members  52  and  54 , respectively, for securement to the foot of a user. Processing unit  10  is provided with an on/off switch  56  and a reset switch  58  as well as a digital display indicator panel  60  which records distance traveled and a digital display  62  which records total distance traveled. The processor unit  10  also includes a temperature sensor  74  with the temperature reading being programmable within the processing unit  10  to calculate the distance between the left foot and the right foot. During the movement from the left foot and the right foot, the ultrasonic sound generator  42  emits ultrasonic waves which are received by an ultrasonic sound receiver  110  (illustrated in FIG. 6A) within the processing unit  10 . The ultrasonic generator  42  may be provided with an on/off switch  64 . 
     Referring to FIG. 5, the operation of the pedometer will now be explained. FIG. 5 represents one sequence of a walking or running mode for the user. The sequence would be the right foot indicated on the right side of FIG. 5 at  66  as the completion of a stride, followed by an impact of the left foot to close pressure sensitive switch  30 , indicated at  68  and the movement of the right foot in a forward direction until impact and closure of the pressure sensitive switch  32 , indicated at  70 . During the stride as the right foot moves from position  66  to position  70 , it moves in a forward path and reaches a point  72  midway between the initiation of the stride  66  and the completion of the stride  70 . During this movement the ultrasonic sound generator  42  emits ultrasonic waves received by the ultrasonic sound receiver  110 . The shortest distance between processing unit  10  and ultrasonic generator  42  is at point  72  where ultrasonic generating unit  46  is directly opposite processing unit  10 . At this point, the signal strength will be strongest since the distance is shortest and the processor senses the maximum signal output and calculates the distance between the left foot and the right foot as indicated in FIG.  5 . Since the ultrasonic sound waves move at the speed of sound and are temperature sensitive, input from the temperature sensor  74  (illustrated in FIG. 6A) is used by the processor  10  in calculating the distance between the left foot and the right foot when the right foot is at the position  72  and the left foot is at position  68 . 
     It should be understood that a variety of energy generation devices may be employed to transmit the requisite signals. In one embodiment, the generation device may be an ultrasound generator which emanates ultrasonic waves from a transmission point generally outwards. These ultrasonic waves are then detected from a receiver in close proximity to the generation device regardless of the orientation of the generation and receiver devices. 
     As the right foot continues it&#39;s stride, when the weight on the right foot closes pressure sensitive switch  32  at position  70 , the ultrasonic sound generator  42  is interrupted and the interruption in the signal is received by the processor  10 , which then calculates the distance the right foot is at position  70  from the left foot. With the distance between positions  68  and  72  being calculated and the distance between positions  68  and  70  also being calculated, the distance between position  72  and  70  can be calculated since, as seen in FIG. 5, a right triangle is formed and the computed distance may be readily calculable using the Pythagorean theorem, i.e., the formula a 2 +b 2 =c 2 , where “a” is the known distance between positions  68  and  72  (a side) and “c” is the known distance between positions  68  and  70  (the hypotenuse). 
     Reference is now made to FIG. 6A which, in block diagram form, illustrates the interaction of components of the pedometer. Ultrasonic sound waves from generator  42  are received in processor  10 . As discussed, processor  10  may be located in the ultrasonic sound receiver  110 . These signals are sent to the processor  10  as well as signals representative of the sensed temperature by temperature sensor  74 . Signals are also sent upon the closure of pressure sensitive switch  30  in the left shoe and pressure sensitive switch  32  in the right shoe. By sequentially counting the closure of pressure sensitive switch  30  and pressure sensitive switch  32 , the processor  10  determines each step taken. 
     FIG. 6B is a flowchart illustrating the functionality of the processor unit  10 . Initially, the processor unit  10  determines each step (block  76 ), as discussed with respect to FIG.  5 . As explained above, the processor  10  continually monitors the strength or amplitude of the ultrasonic sound being received by receiver  110  and determines the point of maximum signal strength (block  78 ). Once the maximum signal strength has been detected, the processor  10  determines the distance between the user&#39;s left foot and right foot at the maximum signal strength point (block  80 ). The next time the right foot applies sufficient pressure to close pressure sensitive switch  32 , a signal is sent to the processor  10  and the processor  10  determines the distance from the point at which pressure sensitive switch  32  was closed to the last point at which pressure sensitive switch  30  associated with the left shoe was closed (block  82 ). The processor  10  then calculates the distance between the point the pressure sensitive switch  32 , associated with the right foot is closed, and the last position indicated by the closure of pressure sensitive switch  30 , associated with the left shoe was sensed (block  84 ). Based on these calculated distances, as shown in FIG. 5, the distance between the point of maximum signal strength and the next closure of pressure sensitive switch  32  may be calculated. The calculated distance can be doubled to indicate the distance traveled by one stride (block  86 ). 
     The terms and descriptions used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations are possible within the spirit and scope of the disclosure as defined in the following claims, and their equivalents, in which all terms are to be understood in their broadest possible sense unless otherwise indicated.