Ariel Performance Analysis System (APAS)
APAS is a 3-D high speed video motion analysis system developed for conducting biomechanical measurement. The system provides a means to quantify motion utilizing input from the following media: video, electromyography, and force platforms.
It consists of two cameras and a computer for data analysis. A special calibration cube is used to define the 3-D space in which the movements are recorded. The device models human body as a mechanical system of segments in motion and they are affected by gravity and reactive force. It is a non-invasive method (www.aierlnet.com).
What follows is the analysis of 3-D video system use.
- A specific video should be used to record motions for biomechanical analysis. If the recording is not in AVI format which uses file format extensions it must be converted. For a 2-D analysis one recording being perpendicular to the motion plane is enough. For a 3-D recording minimum two recordings are needed so that the planes of the cameras would be perpendicular to each other. Editing should be done in a way that the instant and motion of frames could be seen from and other angle with the same number.
- The menu offers options for different phases of analysis.
- Digitize menu is for entering recordings into a computer. Before the analysis the characteristics of frames should be entered (e.g. Units, Type, #Joints-; #Control, Height and Weight) in the icon of Enter Sequence Parameters. Switching to Joint ID’s and Control XYZs the markers and reference joints should be given. The Create Multiple Views menu contains the number of cameras. In the View Info icon the place of cameras are entered. Frame Rate, Camera ID and the place of the Camera (x y, z) should be given. First the fix point and the reference frame must be defined. It is then when digitization can start from point to point, from frame to frame. Video window/windows contain/s the number of frames (Im:), time of frames (T:) and specification of the point which are indicated in a frame. Correct icon is used to correct mistakes. After indicating the points ►Advance icon must be clicked forward (◄ - reverse icon is for clicking backward) then data will be recorded. All the points must be entered appropriately in each frame. ‘Auto mode” can be started and stopped by clicking on Start and Stop. This time only frames should be “scrolled” and the program will recognize the markers. When all the frames have been recorded Digitize window can be closed and the entered information will be automatically saved.
- The next step is entering the Transform menu. Here are the points transferred into D2 or D3 movements. In the Trace Files window the transferable frames can be chosen. Then the program automatically saves information.
- Filter serves as a means of reducing errors. Top graphic refers to “x” axis, the middle to “y” and the bottoms to “z”. Under File menu it is signalled which data of points are shown by diagrams. These can be changed by switching to ► (Next) and ◄ (Previous) icons. All the errors of digitalization can be filtered. Sliders will help to do this. A red line on the diagrams signals the entered data through the process of digitalization. If the blue line approximates the red one it means that sliders are in their right place. When all the points have been corrected and filtered then the program can be closed as the information is automatically saved.
- Data can be gained from Display menu Switching to Open 3D files being created in the above procedures can be chosen. Then new 3D- must be opened in the Channels window. Specify 3D Data Trial is for choosing the needed data according to Tape, Quantity, and Joint/seg #1: #2, Component. Data are revealed in Table or in Graph menus. Stick Figures or Video + Stick forms are also available. Data can be copied into Excel table.