Abstract:
An apparatus in one example comprises one or more sensors that produce one or more signals based on one or more joint motions of an individual, and one or more processing components that employ one or more of the one or more signals to make a determination of a positional change of the individual.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority of U.S. utility patent application Ser. No. 10/681,529, filed by Robert E. Stewart on Oct. 8, 2003 and entitled “JOINT MOTION SENSING TO MAKE A DETERMINATION OF A POSITIONAL CHANGE OF AN INDIVIDUAL” and claims the priority of U.S. provisional patent application 60/418,119, filed by Robert E. Stewart on Oct. 11, 2002, and entitled “STRAIN SENSOR EMPLOYMENT OF JOINT MOTION TO DETERMINE LOCATION OF BODY” of which the entire contents of both applications are incorporated herein by reference. 
     TECHNICAL FIELD 
     The invention in one example relates generally to sensing and more particularly to motion detection. 
     BACKGROUND 
     An inertial navigation system (“INS”) and a global positioning system (“GPS”) generate position information on an individual. The inertial navigation system and the global positioning system generate complementary position information. The position information generated by the global positioning system may be used to correct the position information generated by the inertial navigation system for some measurements. The position information generated by the inertial navigation system may be used during reacquisition of satellites by the global positioning system. A filter (e.g., a Kalman filter) is used to weigh and combine the position information received from the inertial navigation system and the global positioning system. The accuracy of the position information on the individual is dependent on the reliability and availability of the inertial navigation system and the global positioning system. If either the inertial navigation system or the global positioning system become unreliable and/or unavailable, then the position information determined by the filter becomes less accurate. If both the inertial navigation system and the global positioning system become unreliable and/or unavailable, then no position information is generated. 
     As one shortcoming, the inertial navigation system has a position error (e.g., drift) that builds up over time. As the elapsed time of operation increases, the position information generated by the inertial navigation system becomes less accurate. There are times when the elapsed time of operation is long compared to the drift performance of the inertial navigation system. During such times, the position information determined by the filter becomes less accurate. 
     As another shortcoming, there are times when the global positioning system is unavailable due to jamming or interference. During such times, the position information determined by the filter becomes less accurate. 
     As yet another shortcoming, upon initialization and/or re-initialization, the inertial navigation system requires a starting and/or restarting position to begin generating the position information of the individual. Without the external input of the starting and/or restarting position, the inertial navigation system is unable to begin navigation. Also, upon initialization and/or re-initialization, a delay exists between the start of initialization and/or re-initialization and when the global positioning system is able to begin navigation. The delay is reduced if upon initialization and/or re-initialization the starting and/or restarting position of the global positioning system is available. There are times when an accurate starting and/or restarting position is unavailable. 
     SUMMARY 
     The invention in one implementation encompasses an apparatus. The apparatus comprises one or more sensors that produce one or more signals based on one or more joint motions of an individual, and one or more processing components that employ one or more of the one or more signals to make a determination of a positional change of the individual. 
     Another implementation of the invention encompasses a method. One or more movements of one or more joints of an individual are measured. The one or more movements are translated into a positional change of the individual. 
     Yet another implementation of the invention encompasses an article. The article comprises a computer-readable signal-bearing medium. The article includes means in the medium for measuring one or more movements of one or more joints of an individual. The article includes means in the medium for translating the one or more movements into a positional change of the individual. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Features of exemplary implementations of the invention will become apparent from the description and the accompanying drawings in which: 
         FIG. 1  is a representation of one exemplary implementation of an apparatus that comprises one or more sensors, a processing component, and a navigation component. 
         FIG. 2  is a representation of one exemplary flow diagram employable by the apparatus of  FIG. 1 . 
         FIG. 3  is a representation of another exemplary flow diagram employable by the apparatus of  FIG. 1 . 
         FIG. 4  is another representation of one exemplary implementation of the apparatus that comprises one or more sensors, the processing component, and the navigation component. 
     
    
    
     DETAILED DESCRIPTION 
     Turning to  FIG. 1 , an apparatus  100  in one example comprises one or more sensors and a processing component for measuring a movement of a body, for example an individual. The one or more sensors are strategically located on one or more joints of the individual. The one or more sensors measure movements of the one or more joints in one or more directions. The processing component translates (e.g., calculates, converts, infers, deduces, determines, and/or extrapolates) the movements of the one or more joints into a general movement of the individual. The general movement represents an overall movement of the individual. The apparatus  100  includes a plurality of hardware and/or software components. A number of such components can be combined or divided in the apparatus  100 . 
     In one example, the apparatus  100  employs at least one computer-readable signal-bearing medium. One example of a computer-readable signal-bearing medium for the apparatus  100  comprises an instance of a recordable data storage medium  201  ( FIG. 2 ) such as one or more of a magnetic, electrical, optical, biological, and atomic data storage medium. In another example, a computer-readable signal-bearing medium for the apparatus  100  comprises a modulated carrier signal transmitted over a network comprising or coupled with the apparatus  100 , for instance, one or more of a telephone network, a local area network (“LAN”), the internet, and a wireless network. An exemplary component of the apparatus  100  employs and/or comprises a set and/or series of computer instructions written in or implemented with any of a number of programming languages, as will be appreciated by those skilled in the art. 
     In one example, the apparatus  100  comprises an anthropometric dead reckoning motion detector for a body. “Anthropometric” as used herein in one example refers to measurement of the body. “Dead reckoning” as used herein in one example refers to navigating by measuring the course and distance traveled from a known point. In one example, the body comprises an individual  102 . For example, the individual  102  comprises a person, animal, or robot. The anthropometric dead reckoning motion detector takes measurements of the individual  102  and converts the measurements to a position change starting from a known location. 
     The apparatus  100  comprises one or more sensors, for example one or more of bi-lateral ankle sensors  104  and  106 , knee sensors  108  and  110 , hip sensors  111  and  112 , waist sensors  113  and  114 , wrist sensors  115  and  116 , elbow sensors  118  and  120 , shoulder sensors  122  and  124 , a processing component  126 , and a navigation component  128 . In one example, one or more of the sensors comprise strain sensors, as described herein. In another example, one or more of the sensors comprise rate sensors, for example, low cost rate sensors. The one or more sensors serve to measure a movement of one or more joints of the individual  102 . For example, the one or more sensors measure three dimensional motion of the one or more joints, such as the ankle, knee, hip, waist, wrist, elbow, and/or shoulder of the individual  102 . 
     As the individual  102  traverses a path from a known starting location, the apparatus  100  serves to measure the movement of the one or more joints of the individual  102  and record the movement. Subsequently, the movement of the one or more joints of the individual  102  is reconstructed to determine the path of the individual  102 . 
     The one or more sensors are arranged bi-laterally on the individual  102 . The one or more sensors may be arranged symmetrically or asymmetrically on the individual  102 . The one or more sensors may measure other joint locations, in addition to the ankle, knee, hip, waist, wrist, elbow, and/or shoulder of the individual  102 . The one or more sensors monitoring the one more joints on the lower body of the individual  102  provide information to reconstruct a locomotion of the individual  102 . For example, the information generated by the ankle sensors  104  and  106 , knee sensors  108  and  110 , hip sensors  111  and  112 , and waist sensors  113  and  114  translate to the locomotion of the individual  102 . The information generated by the one or more sensors may also be translated to measure critical points along the path such as abrupt turns or elevation changes. 
     The one or more sensors measure a direction and a displacement of the movement. In one example, a first sensor measures the direction of the movement and a second sensor measures the displacement of the movement. In another example, the first and second  25  sensors measure both the displacement and direction of the movement. 
     The one or more sensors comprise strain sensors. The strain sensors detect a bending strain and/or a twisting strain due to the movement of the one or more joints of the individual  102 . For example, the ankle sensors  104  and  106  detect the bending strain and/or the twisting strain due to the movement of the ankle joint. The bending strain corresponds to, and may be translated to, the displacement (e.g., meters) of the movement. The twisting strain corresponds to, and may be translated to, the direction (e.g., degrees) of the movement. 
     In one example, the one or more sensors are embedded in a suit  130  at the one or more joints of the individual  102 . The suit  130  is worn by the individual  102 . The suit  130  may be worn as outerwear, an undergarment, or incorporated into another suit. The suit  130  may be incorporated into a second suit used to monitor other information such as biological functions of the individual  102  (e.g., heart rate, body temperature, etc.). 
     Referring to  FIGS. 1-2 , the processing component  126  employs one or more algorithms for translating measurements from the one or more sensors into a position change of the individual  102 . A first algorithm  202  takes as an input a bending component of the strain experienced by the one or more sensors. The first algorithm  202  translates the bending component into a displacement component of the position change. A second algorithm  204  takes as an input a twisting component of the strain experienced by the one or more sensors. The second algorithm  204  translates the twisting component into a direction component of the position change. A third algorithm  206  takes as inputs the displacement component, the direction component, and a starting location of the position change. The third algorithm  206  translates the displacement component, the direction component, and the starting location of the position change into an updated position of the individual  102 . The one or more algorithms and the one or more sensors may be calibrated to the specific motions of the individual  102  by having the individual  102  traverse a known path. The measurements by the one or more sensors generated during traversal of the known path will tune the one or more algorithms to the specific motion of the individual  102 . The first, second, and third algorithms may be combined or divided. 
     The third algorithm  206  may additionally take inputs from a magnetic heading sensor  208  and a barometric altitude sensor  210 . The magnetic heading sensor  208  provides additional information on the direction of the movement of the individual  102  to supplement the twisting component of the strain sensors. The magnetic heading sensor  208  would use the Earth&#39;s magnetic field to sense the direction of the movement. A change in magnetic field measured by the magnetic heading sensor  208  would correspond to a change of direction by the individual  102 . The barometric altitude sensor  210  would measure an atmospheric pressure for altitude position changes. A change in atmospheric pressure measured by the barometric altitude sensor  210  would correspond to a change of altitude by the individual  102 . The position information generated by the magnetic heading sensor  208  and the barometric altitude sensor  210  would assist the anthropometric dead reckoning motion detector during motion of the individual  102  while the one or more joints of the individual  102  are not in motion. The third algorithm  206  would weigh and combine the position information generated by the magnetic heading sensor  208  and the barometric altitude sensor  210  with the position information generated by the first and second algorithms  202  and  204 . 
     The navigation component  128  in one example comprises an inertial navigation system  212  (“INS”) and/or a global positioning system  214  (“GPS”). The navigation component  128  provides position information of the individual  102  to supplement the position information generated by the processing component  126 . In one example, the navigation component  128  is attached to the waist of the individual  102 . For example, the navigation component  128  is integrated into a belt for the individual  102 . 
     Referring to  FIG. 4 , in another example, the navigation component  128  is located at a heel of the foot of the individual  102 . For example, the navigation component  128  is mounted into a shoe or boot worn by the individual  102 . Additionally, the processing component  126  and other electronic components may be located with the navigation component  128  in the shoe worn by the individual  102 . Locating the navigation component  128  in the shoe allows for zero velocity updates or zero position change updates for the navigation component  128 . For example, at a time when the foot of the individual  102  is planted or substantially stationary, the navigation component  128  may initiate the zero velocity update to correct for error or bias in measurements of the navigation component  128 . 
     Referring to  FIGS. 1-2 , a filtering component  216  comprises an algorithm to weigh and combine the position information generated by the processing component  126 , the inertial navigation system  212 , and the global positioning system  214 . The weighing and combination of the position information is based on the respective reliabilities of the processing component  126 , the inertial navigation system  212 , and the global positioning system  214 . The algorithm processes the measurements of the processing component  126 , the inertial navigation system  212 , and the global positioning system  214  to deduce an estimate of the position of the individual  102  by using a time sequence of measurements of the system behavior, plus a statistical model that characterizes the system and measurement errors, plus initial condition information. In one example, the filtering component  216  comprises a Kalman filter. In one example, the processing component  126  and the filtering component  216  are combined with the navigation component  128 , for example in the inertial navigation system  212 . The output of the filtering component  216  may be passed to one or more of a display  218  and a recording device  140 . 
     The recording device  140  stores the position information output from the filtering component  216 . A path of the individual  102  may be reconstructed from the known starting location and the recorded position information. The path may be used to create a map of an area previously unmapped, incorrectly mapped, or update outdated maps. Using dead reckoning navigation to provide information for cartography is especially useful in remote areas where the global positioning system  214  is unavailable, or in areas where the global positioning system  214  in experiencing jamming or interference. 
     Upon initialization and/or re-initialization, the inertial navigation system  212  requires a starting and/or restarting location to begin generating the position information of the individual  102 . The dead reckoning position information generated by the processing component  126  may be used as an estimate of the starting and/or restarting location for the inertial navigation system  212 . Upon initialization and/or re-initialization, the global positioning system  214  would benefit from the starting and/or restarting position to lock onto satellites. The dead reckoning position information generated by the processing component  126  may be used as an estimate of the starting and/or restarting location for the global positioning system  214 . 
     During the run times, the inertial navigation system  212  and the global positioning system  214  may provide corrections to the one or more sensors and/or the processing component  126 . Therefore, the position information generated by the inertial navigation system  212 , the global positioning system  214 , and the processing component  126  would be in better agreement. Due to the corrections, at a time when the inertial navigation system  212  and/or the global positioning system  214  become unavailable, the processing component  126  would be more able to alone generate an estimate of the position information. 
     Referring to  FIG. 3 , in one example the navigation component  128  comprises a signal conditioning component  302 , a signal processor  304 , and zero or more of the inertial navigation system  212  and the global positioning system  214 . The one or more sensors of the suit  130  pass information to the navigation component  128 . The signal conditioning component  302  receives the information from the one or more sensors. The signal conditioning component  302  converts the information from one or more analog signals to one or more digital signals. The one or more digital signals represent the motion of the one or more joints of the individual  102 . The one or more digital signals are multiplexed to the signal processor  304 . The signal processor  304  converts the one or more digital signals to the position information of the individual  102 . The position information of the individual  102  derived from the signal processor  304  and the global positioning system  2   14  are passed to the inertial navigation system  212 . The inertial navigation system  212  comprises an algorithm to weigh and combine the position information generated internally, and generated by the global positioning system  214  and the signal processor  304 . 
     The steps or operations described herein are just exemplary. There may be many variations to these steps or operations without departing from the spirit of the invention. For instance, the steps may be performed in a differing order, or steps may be added, deleted, or modified. 
     Although exemplary implementations of the invention have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions, and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention.