Abstract:
Taught herein is an apparatus for measurement of floating body posture of a person wearing a life jacket, comprising a backpack frame having a plurality of reference points, an image collecting system, and an image processing system; wherein the image collecting system collects image sequence information of the person wearing the life jacket via the reference points; the image processing system processes the image sequence information, so as to obtain the dynamics of a movement of the person and the quasi-static parameters of such movement. The system is capable of reflecting the dynamics of a movement of a body in water and the quasi-static parameters thereof.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Chinese Patent Application No. 200610088838.6 filed on Jul. 19, 2006, the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an apparatus for measurement of posture, and particularly to an apparatus for measurement of floating body posture of a person wearing a life jacket. 
     2. Description of the Related Art 
     Posture of a person wearing a life jacket in water is an important factor in evaluating performance of a life jacket, and how to accurately obtain various posture parameters is of great importance for the evaluation. Conventionally, posture parameters of a person wearing a life jacket in water are obtained by expert evaluation and static testing. Safety standards of various countries define that when a person wearing a life jacket is in a balance state, the distance between the person&#39;s mouth and the water surface is measured first, the overturn time of the person is calculated using a stopwatch, and then a float angle is obtained via a protractor. However, this method is too simplistic to accurately reflect the dynamics of a movement of the person&#39;s body in water and the quasi-static parameters associated therewith. 
     SUMMARY OF THE INVENTION 
     In view of the above-described problems, it is one objective of the invention to provide a system that is capable of reflecting a movement of a person&#39;s body wearing a life jacket in water and the quasi-static parameters thereof. 
     To achieve the above objectives, one embodiment of the invention provides an apparatus for measurement of floating body posture of a person wearing a life jacket, comprising a backpack frame having a plurality of reference points, an image collecting system, and an image processing system; wherein the image collecting system collects image sequence information of the person wearing a life jacket from the reference points; the image processing system processes the image sequence information, so as to obtain a dynamics of a movement of the person and the quasi-static parameters associated therewith. 
     In certain classes of this embodiment, the image collecting system comprises a pair of cameras, and a pair of image collecting cards connected to the cameras via a pair of data lines. 
     In certain classes of this embodiment, the backpack frame is located in an overlapping view field of the cameras. 
     In certain classes of this embodiment, the image processing system comprises software for performing image processing and a computer (incl. CPU). 
     In certain classes of this embodiment, the backpack frame comprises a plurality of bellows, a plurality of supporting plates, a plurality of reference points, a shoulder armor plate, a plurality of aluminum pipes, a haunch armor plate, a plurality of steel bars, a plurality of rivets, a waistband, a plurality of welding spot, a first connector and a second connector. 
     In certain classes of this embodiment, the bellows are jointly connected to the aluminum pipes via the shoulder armor plate. 
     In certain classes of this embodiment, the haunch armor plate is connected to the steel bar via the rivet. 
     In certain classes of this embodiment, the aluminum pipe is connected to the bellows via the first connector. 
     In certain classes of this embodiment, the aluminum pipe is connected to the supporting plates and the reference point via the second connector. 
     In certain classes of this embodiment, a surface of the supporting plate is coated with one or more low-reflectivity materials. 
     In certain classes of this embodiment, the supporting plate is fixed to the first connector via a screw thread. 
     In certain classes of this embodiment, the reference point is fixed to the first connector with glue. 
     In certain classes of this embodiment, the shoulder armor plate operates to fix the backpack frame to a shoulder of the person wearing the life jacket. 
     Compared with prior art, the invention has the following advantages: (1) The backpack frame features strong and flexible characteristics, high rigidity, small weight, convenient and reliable connection, compatibility with various devices, adaptability to different postures, along with no effects on movement of a person in water, which meet the testing requirements and enhance flexibility; (2) An image recognition algorithm of the reference point makes it possible to accurately locate the center of a circle even if the reference point is partly shaded, which greatly improves reliability of the system. The supporting plate coated with low-reflectivity materials is disposed at the bottom of the reference point, and helps to overcome the light reflection effect in a complex circumstance, which bring great convenience and reliability for object recognition; (3) The body movement posture in water is optically measured via reference points in a non-contacting manner, which transforms the body posture into a spacial position of a reference point. In this way, an expected dynamic movement of any time duration can be obtained, and the limitation of manual sampling is overcome; (4) A fast and precise circular object recognition algorithm based on a reference point recognition algorithm and a curvature scale-space technique is provided; (5) The precision of the circular object recognition algorithm is higher than that of a classical Hough transform, and it is more reliable than a block-based processing and recognition algorithm. The circular object robust recognition algorithm overcomes problems caused by shading of the reference point and a complex background, and reduces time spent on calculation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described hereinafter with reference to accompanying drawings, in which: 
         FIG. 1  is a schematic diagram of an apparatus for measurement of floating body posture of a person wearing a life jacket according to one embodiment of the invention; 
         FIG. 2  is a schematic diagram of a backpack frame according to one embodiment of the invention; 
         FIG. 3  is a schematic diagram of a testing gauge according to one embodiment of the invention; 
         FIG. 4  illustrates a diagram for connecting a bellows with a connector according to one embodiment of the invention; 
         FIG. 5  is a cross-sectional view of a connector according to one embodiment of the invention; 
         FIG. 6  is a cross-sectional view of a connector according to another embodiment of the invention; and 
         FIG. 7  is a schematic diagram of body coordinates used in calculations according to one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIG. 1 , an apparatus for measurement of floating body posture of a person wearing a life jacket comprises a first camera  5 , a second camera  3 , a first data line  2 , a second data line  1 , a synchronization control line  4 , a bracket  6 , a backpack frame  7  with a reference point  7 ′, a support pipe  8 , a shoulder strap  9 , a waistband  10 , a display  11 , and a host computer  12 . The bracket  6  is located at the edge of a water pool. The display  11  and the host computer  12  are located on one side of the bracket  6 . The cameras  3  and  5  are fixed on the bracket  6 . The bracket  6  may move in two coordinate planes. A pitching angle and a fling angle of each of the cameras  3  and  5  can be adjusted. The cameras  3  and  5  are connected to a pair of OK_C30S image collecting cards in the host computer  12  via the data lines  1  and  2 . The cameras  3  and  5  are adjusted to face downward the water surface, so that an overlapping view field therebetween is a movement region of a person wearing a life jacket in the water. External synchronization trigger ports of the cameras  3  and  5  are connected to each other via the synchronization control line  4  to ensure synchronous data collection. It is required that the person wearing life jacket put the backpack frame  7  on his/her back via the shoulder strap  9  and the waistband  10  before getting into water, and it should be ensured that the reference point  7 ′ on the backpack frame  7  is located in the overlapping view field of the cameras  3  and  5  after the person gets into water. The cameras  3  and  5  should be adjusted based on a function of “double card synchronous real-time display” for collecting software run on the computer display  11 . A human-computer interaction is processed by an image collecting program in a sampling mode designated by a user, the sampling mode comprising selecting different collecting objects (i.e. memory, hard disk), sample time, sample frequencies and so on. 
     To obtain a relationship between a two-dimensional plane coordinate of the reference point on the backpack frame  7  and a three-dimension space coordinate thereof, the cameras  3  and  5  need to be calibrated, which comprises collecting moving sequence images on a calibration plate as shown in  FIG. 7  by the cameras; then processing the moving sequence images according to a calibration program guideline of the cameras to obtain parameters of the cameras; and finally saving the parameters to a data file for further calculation. 
     As shown in  FIG. 2 , a backpack frame  7  comprises a plurality of bellows  13 , a plurality of supporting plates  14 , a plurality of reference points  7 ′, a shoulder armor plate  16 , a plurality of aluminum pipes  17 , a haunch armor plate  18 , a plurality of steel bars  19 , a plurality of rivets  20 , a waistband  21 , a plurality of welding spots  22  and a plurality of connectors  32 . 
     The bellows  13  are jointly connected to the aluminum pipes  17  via the shoulder armor plate  16 , and the haunch armor plate  18  is connected to the steel bars  19  via the rivets  20 . The aluminum pipe  17  is connected to the bellows  13  via the connector  32 , and to the supporting plates  14  and the reference point  7 ′ via the connector  32  with a length of about 20 cm. A surface of the supporting plate  14  is coated with low-reflectivity materials, and the supporting plate  14  is fixed to the connector  31  via a screw thread. The reference point  29  is a standard ping pong ball, and is fixed to the connector  31  with glue. The shoulder armor plate  16  operates to fix the backpack frame to a shoulder of the person wearing the life jacket. 
     As shown in  FIG. 3 , a testing gauge of the invention measures distances between the reference points and a mouth of the person wearing the life jacket. A lower end of the pole  24  is interference fit with a glass post  23  of 5 cm in length. A portion of the pole  24  within a range of 3 cm away from the top thereof is rolled flat and drilled, and then connected to a left part of a pole  26  which is rolled flat via a plurality of bolts and nuts. A groove with a length of 3 cm and a width of 1.5 cm is disposed at a lower part of the pole  27 , so as to receive a rectangular aluminum board  28  with a thickness of 1.5 mm. The groove is interference fit with the aluminum board  28 . A portion of the pole  27  within a range of 3 cm away from the top thereof is rolled flat and drilled, and then connected to the pole  26  via a plurality of bolts and nuts. In this way, by adjusting an angle among the poles  24 ,  27  and  26 , the organic glass post may abut against the mouth and the aluminum board  28  may be tangent with the reference point  7 ′. Then, nuts on both sides of the poles  24  and  27  are fastened, so that the angle among the poles  24 ,  27  and  26  is fixed. Finally, the bracket is removed, a distance between the lower part of the organic glass post  23  and the aluminum board  28  is measured, and the distance between the reference point  7 ′ and the mouth is determined. 
     As shown in  FIG. 4 , the radius of the supporting plate  14  is 8 cm, a center of the supporting plate  14  is drilled and tapped, and then the supporting plate  14  is connected to the connector  31  via a screw thread, and the reference  7 ′ is fixedly connected with glue to a bolt at the top of the connector  31 . As the bellows  13  are inset into the connector  31 , the bellows  33  are fixed via four bolts uniformly distributed at the bottom of the connector  31 . 
     As shown in  FIG. 7 , it is defined that the chest-back axis is the X direction, the left-right axis is the Y direction, the head-haunch axis is the Z direction, the three reference point planes on the top of the backpack frame constitute an X-Y plane of the backpack frame coordinate system, and a normal of the X-Y plane is the Z direction of the backpack frame coordinate system. Because a transformation matrix between the backpack frame coordinate system and the body coordinate system does not change with a movement of the body, the position of every coordinate of the backpack frame coordinate system can be obtained from the reference points indirectly, and a space position can be obtained from the transformation. If the collected image is a time sequence, the dynamic movement of the body posture with time is determined, and reliable data for evaluating floating performance of a life jacket are obtained by analyzing static values of the body posture. 
     The process of measuring of floating body posture of a person wearing a life jacket comprises: starting the computer and powering on the cameras; activating the image collecting software; selecting the option “two way real-time display”; adjusting the cameras to appropriate positions as described above, and determining a testing region; implementing software-assisted image collecting and data processing; displaying and analyzing results; saving the results in a database in the form of data and diagrams; and reading and/or displaying analysis results via the “show result” interface option. 
     While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.