Abstract:
Described are an automated system, an apparatus, and a method adapted to tracking and dynamically measuring locations in a volume for determining a size and a position of a body during a performance of a repetitive motion, such as in using sporting equipment. The sporting equipment may be a bicycle, and the body may be a cyclist. The apparatus comprises a plurality of markers attached to the body, a three-dimensional marker tracking system, and a processing unit. The apparatus, system, or method computes a dimensional statistic from computed measurements of all strokes of at least two strokes included in a period of time of the repetitive motion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This a US non-provisional patent application claiming priority to the provisional patent application filed by Simms, et al, on Sep. 23, 2008, with Ser. No. 61/099,490. 
     
    
     FIELD OF INVENTION 
       [0002]    This invention relates to an automated method and system for tracking and dynamically measuring locations in 3-dimensional space to determine one or more dimensions or one or more positions of a body during the performance of a repetitive motion. 
       BACKGROUND 
       [0003]    Prior art optical-based measurement systems have been employed to measure or analyze motion of a body-including a performance of a repetitious action during some period of time. One example is the Motus system of Vicon Motion Systems (Centennial, Colo.), which employs retro-reflective markers attached to the joints or other locations of a human body and viewed by one or more video cameras. Some systems can track and analyze the motion in 3 dimensions (3-d). 
         [0004]    For example, prior art systems may search for a single maximum extension angle of a joint during a motion recording period, and upon conclusion of the recording period, typically report only a one isolated maximum extension angle which was captured. This may be because the system is not specialized for recording and analyzing repetitive—or cyclical—motion. Furthermore, a prior art system may not actually estimate—such as through interpolation—what the actual maximum was, but only the maximum angle of all the body positions which were captured and recorded by the system. That is, motion capture systems acquire and record only discrete body positions, not continuous motion of the body, so that the actual maximum angle in generally may have occurred between two consecutive acquired samples. Other examples include measuring the minimum or flexion angle of a joint, the angle of the joint at some point in a repetitive stroke, a minimum or maximum distance between points on a body, or a distance between body points based on the recorded point locations acquired at discrete instants in time. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    Described herein are a system, an apparatus, and a method, among other embodiments, adapted to obtain dynamic sizing measurements. As used herein, the term “dynamic sizing measurements” refers to one or more body dimensions taken during the performance of a repetitive—or cyclic—action. Dynamic sizing measurements may be used in a variety of applications. One application that employs dynamic sizing measurements is the fitting of sporting equipment to specific users. One type of sporting equipment which may use dynamic sizing measurements to properly fit the equipment to a specific user is a bicycle. It is to be appreciated that the systems, apparatus, methods, and other embodiments described herein may be applied to other sporting equipment and non-sporting equipment. Furthermore, the systems, apparatus, methods, and other embodiments described herein may be applied in non-fitting applications such as, but not limited to, other biomechanical or healthcare applications. 
         [0006]    One embodiment comprises a method of taking measurements of a cyclist  1  situated on a bicycle  2  while the cyclist  1  is operating the bicycle  2  in a stationary position—such, as, but not limited to, on a trainer  3 , as shown in  FIG. 1 . In order to obtain dynamic sizing measurements, a plurality of markers  10   f,    10   a,    10   k,    10   h,    10   s,    10   w  may be placed on the body of the cyclist  1 . In one embodiment, the placement of markers  10   a - 10   w  is determined by the equipment that is being fit for the user. For example, in  FIG. 1 , six markers  10   a - 10   w  are located on the cyclist&#39;s body parts in order to calculate various angles between certain body parts during pedaling of the bicycle. However, it is contemplated that more than or less than six markers  10   a - 10   w  may be used. 
         [0007]    In a method called Stroke Intelligence, the method—or an apparatus or system implementing the method—determines at least one dimensional statistic such as an average minimum and/or an average maximum angle or distance over a plurality of strokes—or cycles—of repetitive motion. The minimum or maximum dimensional statistic is not based on a single measurement location at a single instant of time within a single stroke, but the dimensional statistic is really an average of the minimal or an average of the maximal dimensions computed from the marker locations determined during a plurality of the strokes of the repetitive motion. 
         [0008]    The motion may be represented by a sequence of coordinates and corresponding timestamps for each marker, where the coordinates represent the locations, and where the timestamps represent the instants in time when the locations were determined. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0009]    The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate a preferred embodiment of the present invention and, together with the description, serve to explain the principle of the invention. 
           [0010]      FIG. 1  is a simplified perspective view of the major components of this invention. 
           [0011]      FIG. 2  is a side view illustrating measurement of an angle formed at the knee of a cyclist on a bicycle. 
           [0012]      FIG. 3  is a simplified diagram illustrating interpolation of discrete locations. 
           [0013]      FIG. 4  provides an example of a display of measurements computed by an embodiment. 
       
    
    
       [0014]    Table 1 lists various possible computed measurements using locations of markers measured by the system. 
       DETAILED DESCRIPTION 
       [0015]    One embodiment uses an optical measurement system. With respect to  FIG. 1 , for example, one optical measuring system comprises markers  10   a - 10   w  adapted to emit light which may be received by a reception unit  22 . One example of a reception unit  22  may be the 3DCreator system of Boulder Innovation Group (Boulder, Colo.). One reception unit  22  may have a plurality of reception ports in order to triangularly determine the source of light emitted by each marker  10   a - 10   w.  The reception ports may be adapted to determine angles of the light source within a three-dimensional space. One reception unit  22  may be adapted to receive rays of light from each of a plurality of light-emitting diode (LED) markers  10   a - 10   w.  LED markers  10   a - 10   w  may receive power through a power and synchronization cable from the reception unit  22 . Alternatively, battery-powered LED markers  10   a - 10   w  may be flashed upon wirelessly-transmitted signals to a receiver  21  using radio or infrared transmission. 
         [0016]    In one embodiment, each marker  10   a - 1   0   w  is adapted to sequentially flash and emit light. For example, as shown in  FIGS. 1 and 2 , a first marker may comprise a hip marker  10   h,  a second marker may comprise a knee marker  10   k,  and a third marker may comprise an ankle marker  10   a.  Together, these three markers  10   h,    10   k,    10   a  may be so affixed onto the cyclist to indicate a knee extension angle  40  in 3-dimensional space. 
         [0017]    In one embodiment, it may be advantageous to calculate a maximum knee extension angle in order to properly fit a bicycle  2  to a cyclist  1 . In order to calculate an accurate maximum knee extension angle  40 , the maximum knee extension angle  40  is calculated for each stroke in a series of consecutive strokes, wherein, a single stroke—or cycle of motion may be characterized as a complete revolution of a pedal crank  5 . In determining one knee extension angle  40 , the first marker  10   h  may emit light for 3.5 ms at a first time, the second marker  10   k  may emit light for  3 . 5 ms at a second time, wherein the second time follows the first time, and the third marker  10   a  may emit light for 3.5 ms at a third time, the third time immediately following the second time. Longer or shorter light emitting periods may be used, the markers may emit light in some other order, and/or additional markers  10   f,    10   s,    10   w  may sequentially emit light. In one embodiment, the location of these markers  10   a - 10   w  during a stroke is digitized by the reception unit  22  and then a signal characterizing a location for each marker  10   a - 10   w  is sent via a cable  23  to a processing unit  24 . One processing unit  24  may be a laptop, some other personal computer, or a stand-alone embedded computer. The processing unit  24  is adapted to acquire the marker location data received from the reception unit  22  and process the acquired data into 3-dimensional coordinate values. These 3-d coordinate values may then be used for further processing and data manipulation by the processing unit or a separate computer. 
         [0018]    In a process called “stroke intelligence”, further explained below, one embodiment may take sets of measurements from each stroke and average together the corresponding measurements. In one embodiment, a system may have knowledge of the expected repetitive movements of the cyclist and thus can respond to specific key measurement positions of the cyclist. For example, a pedal and a foot coupled to the pedal may generally follow an approximately circular pattern as diagrammed in  FIG. 3 . However, a marker  10   f  coupled to the foot may only momentarily emit light at a specified, optimal point in time. Therefore each marker  10   a - 10   w  is not continuously providing location data to the reception unit  20 . In particular, the markers  10   a - 10   w  may not emit light exactly at a desired measurement position of the cyclist. Nevertheless, the location of the markers  10   a - 10   w  in-between the light emitting positions of each stroke may be estimated-based on the known repetitive motion. For example, if the coordinates and the corresponding timestamps of three or more consecutive locations  80   a,   80   b,   80   c  of a given marker  10   f  are known for corresponding instants in time, a continuous circle or a polynomial function may be fit to these locations of the marker  10   f,  where the coordinates of the locations are a function of the time of the timestamps. For 2- or 3-dimensional coordinates, each coordinate component (X, Y, or Z) may be described by a single real-valued function. Then, all points on the circle or function correspond to estimated locations at various instants in time. So given an instant in time, an estimated location is defined. Conversely, given a location, a corresponding instant of time may be estimated. 
         [0019]    Furthermore, the locations of all the markers  10   a - 10   w  may be estimated for one and the same specific instant in time using the same technique. Then, the angle formed by any three of the markers  10   a - 10   w  will be, in effect, determined accurately from the three locations for the same given instant in time. 
         [0020]    All motion detection devices, 3D and video, have a set acquisition frequency and therefore do not capture all points continuously. One feature of the present invention is the ability to obtain sufficiently accurate estimates of locations, distances, and/or angles even when the reception unit  22  does not capture marker locations at the optimal time within a given stroke. The estimates may be reliably obtained through software interpolation based on a set of measurements acquired before and after the optimal time. For example, due to the known application-specific movements of the cyclist, such as the foot being attached to the pedal, and the pedal being attached to the crank  5 , the foot is known to move approximately in a circle and therefore, more accurate foot marker locations may be estimated. Other body parts may repetitively move along  3 -d geometrical curves other than a circle. This system of interpolation may be known as “Stroke Intelligence”. 
         [0021]      FIG. 3  illustrates how a circle may be used to interpolate between three consecutive measured locations  81 a, 81 b, 81 c of a marker such as marker  10   f.  The perpendicular bisectors  83   a  and  83   b  of the line segments joining the locations  81   a  and  81   b  and joining the locations  81   b  and  81   c  may be respectively computed using well-known analytic geometry. The intersection of the bisectors is the center  85  of the circle  80  which passed through the three points. Then the most-forward location  82  of the marker  10   f,  for example, may be estimated as being at the end of the radial  84  from the center  85  which is parallel to the forward direction of the bicycle  2 . Alternatively, given that the acquisition times of the locations  81   a,   81   b,   8   c  are known, standard linear interpolation may be used to estimate the location of the marker  10   f  at some specific time between the acquisition times of the locations  81   a  and  81   c.  Estimates of the location of the marker at times not within that range of acquisition times may not be accurate. The same interpolation technique may be used for all markers  10   a - 10   w,  as needed. 
         [0022]    Instead of a circle, some other curve, such as a parabola or other polynomial may be used to approximate the continuous 3-d path of a marker and estimate an extreme location or to estimate the location of the marker at some specified moment. 
         [0023]    In some embodiments, it may be preferred to obtain more than just the locations of markers on a cyclist&#39;s body parts. For example, collections of body positions that make up cyclically-changing angles are desired. A maximum or minimum of such an angle for each stroke may be estimated, such as the angle formed by markers  10   h,    10   k,    10   a,  which may represent the knee angle  40  formed by the thigh and calf. The maximum angles formed by marker locations—as calculated above—spanning a plurality of strokes may be averaged together. That is, one maximum angle may be estimated for each of the plurality of repetitive strokes. Then the average of the estimated maximum angles may be used as a substantially reliable and accurate measurement of the cyclist&#39;s knee extension angle. Similarly, the estimated minimum angles for all strokes may be averaged together to provide a substantially accurate measurement of the cyclist&#39;s knee flexion angle. Likewise, the measurement of an angle or a distance at a given point in each repetitive stroke may be combined with the corresponding measurements of all other strokes to form an average or consensus value. 
         [0024]    Further dimensional statistics besides average minima or average maxima—such as ranges, means and standard deviations of locations, distance, or angles—may be collected over a period of time. The statistics may be collected for any or all angles defined by three markers or for any or all distances between two given markers. Statistics may be gathered similarly for other measureable, dimensional attributes, such as area, volume, power output, or speed. 
         [0025]    An example of Stroke Intelligence computation is measuring the knee extension angle  40 . Nevertheless, as shown in Table 1 and  FIG. 4 , the knee extension angle  40  is only one of many measurement statistics that Stroke Intelligence may be used to obtain and report. During a 15 second timing period a cyclist may take about 18-20 full strokes of motion. Prior art systems may search for a single maximum knee extension angle  40  during the full 15 second recording time, and upon conclusion of the recording period, report the single maximum extension angle  40 . In that case, a single, anomalous or inaccurate measurement may cause an erroneous maximum angle. Conversely, in one embodiment of the current invention, the system watches each stroke, estimates the maximum knee extension angle  40  for that stroke using an interpolation function, and then the system saves the angle for later reporting. The system repeats this estimation for each stroke. In order to obtain the true maximum angle for each stroke, the system checks each stroke to find an interpolated maximum, since more often than not the system will not really acquire data at the exact moment of maximum extension. The system interpolates marker locations and estimates therefrom the maximum extension angle which actually did occur and saves the value of the angle. This interpolation and estimation may be performed for each of many strokes during a period of time. Upon the end of the period, the system is adapted to immediately compute the average of all the saved estimated angles and report the average as the value of the cyclist&#39;s mean knee extension angle  40 . Immediately-averaged measurements provide more accurate sizing measurements compared to providing a single measurement over a period of time, because the averaged positions account for small anomalies due to normal minor variations of body position during repetitive motion. A single measurement fails to guard against any anomalies and minor variations or for the effect of some “outlier” measurement captured when the cyclist sneezed. Prior art systems may fail to perform the automatic, immediate real-time calculation of averaged measurements. 
         [0026]    Distance dimensions as well as angles may be estimated using Stroke Intelligence, and dimensional statistics may be computed therefrom. For example, it may be useful to measure the horizontal distance of the foot with respect to the knee when the foot is at the most-forward position. That is when the pedal crank is at the “3 o&#39;clock” angle for the right side of the cyclist, or at the “9 o&#39;clock” angle for the left side. Few, if any, of the locations of the foot marker may have been acquired with the foot exactly in this location. However, stoke intelligence can use three or more foot locations  81   a,   81   b,   81   c  of the marker  10   f  to estimate when and where the foot marker  81   c  would have reached its most forward location  82  during each stroke by using non-linear circular or polynomial functions to estimate the minimum or maximum of the function. Finding a minimum or maximum of a function is a well known method in elementary calculus. 
         [0027]    Incorporated into the calculations is “marker intelligence”. This means that the system knows which marker is which. In other words, the system knows that light received by the reception unit  20  at a certain instant in time applies to a specific marker  10 . In prior art video systems, a video system operator would have to manually seek each marker and calculate the desired measurement for each stroke and then average the measurements together. The prior art method ignores the problem of interpolation when no captured video frame aligns with the desired cyclist position. Further inaccuracy is introduced by the unreliability of manually selecting the desired markers repeatably on a small computer screen. 
         [0028]    The description above has assumed that the locations—specifically the location coordinates—of the markers and the measurements based on the locations are within a 3-dimensional space. The system, apparatus, and method can be equally applied to locations and measurements within a 2-dimensional space. 
         [0029]    Those skilled in the art can readily recognize that numerous variations and substitutions may be made in the invention, its use, and its configuration to achieve substantially the same results as achieved by the embodiments described herein. Accordingly, there is no intention to limit the invention to the disclosed exemplary forms. Many other variations, modifications, and alternative constructions fall within the scope and spirit of the disclosed invention as expressed in the claims. 
         [0000]    
       
         
               
               
               
               
             
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Physical 
                 Measurement 
                 Markers 
                   
               
               
                 Property 
                 Title 
                 Involved 
                 Measurement Definition 
               
               
                   
               
             
             
               
                 angle 
                 Knee Angle 
                 Hip, 
                 The average of each stroke&#39;s minimum 
               
               
                   
                 Flexion 
                 Knee, 
                 angle in 3D, defined by the hip, knee, and ankle. 
               
               
                   
                   
                 Ankle 
               
               
                 angle 
                 Knee Angle 
                 Hip, 
                 The average of each stroke&#39;s maximum 
               
               
                   
                 Extension 
                 Knee, 
                 angle in 3D, defined by the hip, knee, and 
               
               
                   
                   
                 Ankle 
                 ankle 
               
               
                 angle 
                 Back Angle 
                 Hip, 
                 The average of the 3D acute included 
               
               
                   
                   
                 Shoulder 
                 angle defined by the hip to shoulder line 
               
               
                   
                   
                   
                 segment and the horizon, for all body 
               
               
                   
                   
                   
                 measurement sets. 
               
               
                 angle 
                 Armpit Angle 
                 Hip, 
                 The average of the 3D included angle 
               
               
                   
                 to Elbow 
                 Shoulder, 
                 defined by the hip, shoulder, and elbow for 
               
               
                   
                   
                 Elbow 
                 all body measurement sets. 
               
               
                 angle 
                 Armpit Angle 
                 Hip, 
                 The average of the 3D included angle 
               
               
                   
                 to Wrist 
                 Shoulder, 
                 defined by the hip, shoulder, and wrist for 
               
               
                   
                   
                 Wrist 
                 all body measurement sets. 
               
               
                 angle 
                 Elbow Angle 
                 Shoulder, 
                 The average of the 3D included angle 
               
               
                   
                   
                 Elbow, 
                 defined by the shoulder, elbow, and wrist 
               
               
                   
                   
                 Wrist 
                 for all body measurement sets. 
               
               
                 angle 
                 Forearm 
                 Elbow, 
                 The average of the 3D acute included 
               
               
                   
                 Angle 
                 Wrist 
                 angle defined by the elbow to wrist line 
               
               
                   
                   
                   
                 segment and the horizon for all body 
               
               
                   
                   
                   
                 measurement sets, where positive angle 
               
               
                   
                   
                   
                 represent the wrist higher than the elbow. 
               
               
                 angle 
                 Ankling 
                 Knee, 
                 The average of each stroke&#39;s difference 
               
               
                   
                 Range 
                 Ankle, 
                 between the maximum and minimum 3D 
               
               
                   
                   
                 Foot 
                 included angle defined by the knee, ankle, 
               
               
                   
                   
                   
                 and foot. 
               
               
                 angle 
                 Ankle 
                 Knee, 
                 The average of each stroke&#39;s maximum 
               
               
                   
                 Plantarflexion 
                 Ankle, 
                 3D included angle defined by the knee to 
               
               
                   
                   
                 Foot, 
                 ankle line segment and the foot to heel 
               
               
                   
                   
                 Heel 
                 line segment. 
               
               
                 angle 
                 Ankle 
                 Knee, 
                 The average of each stroke&#39;s minimum 3D 
               
               
                   
                 Dorsiflexion 
                 Ankle, 
                 included angle defined by the knee to 
               
               
                   
                   
                 Foot, 
                 ankle line segment and the foot to heel 
               
               
                   
                   
                 Heel 
                 line segment. 
               
               
                 angle 
                 Hip Angle 
                 Knee, 
                 The average of each stroke&#39;s minimum 3D 
               
               
                   
                 Closed 
                 Hip, 
                 included angle defined by the knee, hip, 
               
               
                   
                   
                 Shoulder 
                 and shoulder. 
               
               
                 angle 
                 Hip Angle 
                 Knee, 
                 The average of each stroke&#39;s maximum 
               
               
                   
                 Open 
                 Hip, 
                 3D included angle defined by the knee, 
               
               
                   
                   
                 Shoulder 
                 hip, and shoulder. 
               
               
                 angle 
                 Knee Travel 
                 Knee 
                 The acute included angle in the frontal 
               
               
                   
                 Tilt 
                   
                 plane between the best fit axis of the 
               
               
                   
                   
                   
                 points of the knee during the recording 
               
               
                   
                   
                   
                 and the vertical axis. 
               
               
                 ang_velocity 
                 Cadence Ave 
                 Foot 
                 The average calculated number of strokes 
               
               
                   
                   
                   
                 per minute defined by the foot for all body 
               
               
                   
                   
                   
                 measurement sets. 
               
               
                 ang_velocity 
                 Cadence Max 
                 Foot 
                 The maximum calculated number of 
               
               
                   
                   
                   
                 strokes per minute defined by the foot of 
               
               
                   
                   
                   
                 the recording time. 
               
               
                 power 
                 Power Output 
                 Button 
                 The average calculated power or user 
               
               
                   
                 Ave 
                   
                 input power during the recording time. 
               
               
                 power 
                 Power Output 
                 Button 
                 The maximum calculated power during the 
               
               
                   
                 Max 
                   
                 recording time. 
               
               
                 velocity 
                 Speed Ave 
                 Button 
                 The average calculated rear wheel speed 
               
               
                   
                   
                   
                 during the recording time. 
               
               
                 velocity 
                 Speed Max 
                 Button 
                 The maximum calculated rear wheel 
               
               
                   
                   
                   
                 speed during the recording time. 
               
               
                 distance 
                 Knee Forward 
                 Knee, 
                 The average of each stroke&#39;s difference 
               
               
                   
                 of Foot 
                 Foot 
                 between the horizontal locations of the 
               
               
                   
                   
                   
                 knee and foot when the foot is in the most 
               
               
                   
                   
                   
                 forward position where a positive number 
               
               
                   
                   
                   
                 represents the knee being more forward 
               
               
                   
                   
                   
                 then the foot. 
               
               
                 distance 
                 Hip Vertical 
                 Hip 
                 The average of each stroke&#39;s difference 
               
               
                   
                 Travel 
                   
                 between the maximum and minimum 
               
               
                   
                   
                   
                 vertical position of the hip. 
               
               
                 distance 
                 Knee Lateral 
                 Knee 
                 The average of each stroke&#39;s difference 
               
               
                   
                 Travel 
                   
                 between the maximum and minimum 
               
               
                   
                   
                   
                 lateral position of the knee. 
               
               
                 distance 
                 Hip to Wrist 
                 Hip, 
                 The average of the differences of the 
               
               
                   
                 Vertical 
                 Wrist 
                 vertical position of the hip and wrist for all 
               
               
                   
                   
                   
                 body measurement sets, where a positive 
               
               
                   
                   
                   
                 number represents the wrist being higher 
               
               
                   
                   
                   
                 than the hip. 
               
               
                 distance 
                 Hip to Wrist 
                 Hip, 
                 The average of the differences of the 
               
               
                   
                 Horizontal 
                 Wrist 
                 horizonal position of the hip and wrist for 
               
               
                   
                   
                   
                 all body measurement sets. 
               
               
                 distance 
                 Hip to Elbow 
                 Hip, 
                 The average of the differences of the 
               
               
                   
                 Vertical 
                 Elbow 
                 vertical position of the hip and elbow for all 
               
               
                   
                   
                   
                 body measurement sets, where a positive 
               
               
                   
                   
                   
                 number represents the elbow being higher 
               
               
                   
                   
                   
                 than the hip. 
               
               
                 distance 
                 Hip to Elbow 
                 Hip, 
                 The average of the differences of the 
               
               
                   
                 Horizontal 
                 Elbow 
                 horizonal position of the hip and elbow for 
               
               
                   
                   
                   
                 all body measurement sets. 
               
               
                 distance 
                 Hip Foot 
                 Hip Foot 
                 The average of the distances between the 
               
               
                   
                 Lateral Offset 
                   
                 lateral position of the hip and foot of each 
               
               
                   
                   
                   
                 body measurement where a positive 
               
               
                   
                   
                   
                 number represents the foot being further 
               
               
                   
                   
                   
                 from the plane of the bicycle than the hip. 
               
               
                 distance 
                 Thigh Length 
                 Hip, 
                 The average of the 3D distances between 
               
               
                   
                   
                 Knee 
                 the Hip and Knee for all body 
               
               
                   
                   
                   
                 measurement sets. 
               
               
                 distance 
                 Shin Length 
                 Knee, 
                 The average of the 3D distances between 
               
               
                   
                   
                 Ankle 
                 the Knee and Ankle for all body 
               
               
                   
                   
                   
                 measurement sets. 
               
             
          
           
               
                 end of Table 1