Hardware

The Ariel Performance Analysis System (APAS-2000) is designed to be a modular system. The basic system consists of the Ariel Enhanced Computer, 2D/3D Ariel Software and optional Color Monitor. Additional hardware is listed as options since much of this equipment is readily available in many clinical and biomechanical facilities.

1. Components:
   
   
   • Pentium Computer consisting of a Pentium II 300 Megahertz Intel Micro Processor. The processor is upgradable to Pentium Micro Processors of the future. The following components are included:
     • 10 GB Hard Disk Drive for Programming and Data Storage
     • 64 MB Random Access Memory (RAM)
     • 3.5 Inch (1.44 Megabyte) Floppy Diskette Drive
     • Multi-Media Compatible Frame Grabber for grabbing S-VHS video fields in NTSC and PAL formats.
     • Multi-Media Package (48X CD-ROM, Sound Card and Speakers)
     • Modem/Fax/Internet connection which allows electronic communications. (And Internet Digitizing).
     • APAS-Zip Drive With APAS Workstation/Backup Software
   • High resolution (1024/768) Color video monitor to display video images and data at the highest level of resolution.

    

2. Options:
   
   
   • Analog to Digital Converter:
     The APAS supports up to 32-channels of simultaneously Analog sampling. Software drivers and programs are available for all the commercially available force platforms and EMG systems.
   • Tape Backup:
     Magnetic tape drives provide a cost effective method for backing up important data. Up to 400 MB (800 MB compressed) can be recorded to a single tape. This can be upgraded to 1.3 GB.
   • Video Cassette Recorders:
     The VCR is used for advancing and capturing the video sequence under field-by-field computer control. There are currently two options for S-VHS VCRs sold with the APAS. The VCR can utilize videos obtained from nearly any type of camera. Thus, cameras with speeds ranging from 30 to 1000 fields per second can be utilized.
   • Cameras:
     For most applications, two VHS or S-VHS video cameras with a variable shutter of up 1/8000 second, are more than adequate to provide accurate 2D/3D biomechanical data. The high speed shutter allows fast moving objects as would be encountered in sporting activities, such as golf, baseball, or tennis, to be recorded with minimal "blurring" effects. High Speed video cameras are also available if required.
   • Force Plates:
     Any of the currently available force plates are available for the most economical price. The customer can choose his/her preferred platform and utilize it in conjunction with the Ariel signal processing software. These hardware/software combinations are commercially unbeatable.
   • NoteBook:
     A fully portable APAS system is available on a Notebook computer. The Ariel NoteBook system can perform all of the same functions which are available with the APAS desktop model. This includes on-site data collection, digitizing, analysis, and analog signal processing. As with the desktop model, the Notebook APAS System can operate any forceplate or EMG System.
   • Workstation:
     The Workstation provides APAS software installation(s) on all compatible computers at the customer's site. This allows satellite computers to be used to digitize, quantify, plot, etc. any APAS data. Thus, a laboratory's biomechanical capacity can be expanded tremendously without a heavy financial burden. The Workstation software capabilities are available to all APAS customers who have additional computers on-site.

Software

The greatest strength of the Ariel Performance Analysis System is its software. Only some of the unique features of the APAS have been selected to illustrate the software powers included in the Basic System:

1. Frame Grabbing Module:
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   • The Ariel Performance Analysis System captures Full Color fields to the computer hard disk storage in a digital form at speeds of 3 fields per second. Brightness, contrast, saturation and color can be changed by the user to actually grab a better video picture than the original video. This allows special software to correct for inherent inconsistencies of the VCR by utilizing the Retrace signal to adjust and correct these problems digitally. All other systems utilize "On the fly" video digitizing. Unfortunately, this method permits inconsistencies in the video field timing and synchronization since the field advance depends upon the mechanical moving heads of the VCR. The Ariel system overcomes this problem under normal procedures, however, any Ariel user who prefers "on-the-fly" digitizing also has the ability to select that option. For more detail of the CAPTURE Program see the on line Manual.
   • Since the fields are stored in digital format, the Ariel software includes an option to Zoom the data. Small objects in the field can be magnified to a real life scale. This feature enables the user to place the cameras far from the object and still magnify the desired joint for increased accuracy in the digitizing process.
   • Tape back up provides convenient storage capabilities since the video signal is converted to digital data and stored on the disk. This is a very useful feature since the investigator does not have to carry the video tape with him/her. This feature also allows users to transfer video data and the corresponding digitized data into the same format to enhance cooperative studies between investigators.
   • High speed modem communication allows the video signal stored on the hard disk to be transmitted through the Internet over regular phone lines.
   • A special compression program minimizes the data storage space utilized by the Ariel system. This feature also enhances modem communication since sending and receiving large quantities of video data through the phone lines can be costly.
   • Another advantage of digital video storage is the ability to display multiple images on the video monitor. For example, the front view and side view can be shown on the monitor simultaneously for "real time" 3D digitizing. This method helps the researcher to see the same activity from multiple views which can aid the digitizing process.
   • There is no need to time code the video tape before grabbing. Although some other motion analysis systems do require a time coding process, the APAS does NOT. Time coding consumes a tremendous amount of time and is not required by the Ariel Performance Analysis System. Should a user want to time code the data, it has been provided as a selectable option.

    

2. Digitizing Module:
   
   
   • The digitizing software supports Manual or Automatic digitizing. In the Manual mode, the Ariel software provides a "learning" feature which uses previous digitizing frames to predict subsequent frames. The software utilizes location, brightness, and kinematic parameters, such as velocity and acceleration, to predict the next point.
   • In the Automatic mode, the Ariel System utilizes contrast, color, velocity and acceleration to locate specific markers. Any color (not limited to reflective white) can be used for markers. In fact, each body joints can be assigned a different color for more accurate automatic digitizing, especially when markers cross or conflict with each other. The Centroid method is used to locate the center of the marker with a tolerance band isolated around the marker. With the Centroid method, the algorithm does not search beyond the boundaries assigned by the investigator.
   • Both manual and the automatic modes can be utilized simultaneously with some markers automatically traced and others digitized manually. A learning mode can be assigned to a marker so that the automatic algorithm will "learn" the characteristics of each point. Therefore, after manually tracing several fields, the point will be "learned" and the digitizing will switch to the automatic mode.
   • The Ariel DIGI-4 program allows up to 4 views to be opened and digitized simultaneously in either "Manual" or "Automatic" modes. Options also exist to perform "Real-Time" transformation during the digitizing process. Three dimensional stick figures and/or graphs can be displayed as the digitizing is being performed! For more detailed description of the Digitizing Program see the "on line" Manual.

    

3. Panning Module:
   
   
   • "Panning" means to follow the object as it moves, left and right or up and down . This allow the investigator to position the camera closer to the individual and to follow the subject during movement in order to maximize the accuracy of the analysis. This technique is particularly useful for gait and sport analyses where the subject may cover a distance beyond the range of normal camera placement.
   • Specialized hardware was designed for the camera to allow panning. A special algorithm and unique software were designed to integrate software and hardware to allow for the panning of one or more cameras.

    

4. Transformation Module:
   
   
   • An unlimited number of cameras can be used in transforming the data into 2D and 3D coordinates. One of the methods utilized is the DLT for normal transformation. The Multiplier technique, for situations where no calibration cube was used and there were only a few objects in the background, can be used to calibrate the field. A third, specialized transformation technique, Physical Parameters is used for panning cameras and especially when greater accuracy is required. For more detailed description see the Transformation Chapter in the APAS Manual.
   • The uniqueness of the Ariel Performance Analysis System also lies in the fact that there is no separation between 2D and 3D modules . When one camera is used, only 2D coordinates are obtained. However, when two or more cameras are used (there is no limit on the number of cameras), the 2D and the 3D are accessible.

    

5. Analog Module:
   
   
   • The Analog Module used in the Ariel Performance Analysis System has extremely powerful software capabilities. The A/D system can handle as many as 32 analog input channels simultaneously.
   • Special parallel processing is used to maximize the sample rate per channel to 10,000 samples per second for 4 channels. Combinations of transducers, thermistors, accelerometers, force plates, EMG, EKG, and others can be combined for analysis and synchronized with the video system.
   • Each channel can be tailored specifically to the Units per Volt level and to the requested scaling. Therefore, EMG signals of Millivolts and Force Plate outputs of volts can be mixed and synchronized.
   • In addition, one very powerful function is the ability to mix the analog data with the video data so it is possible to show the video picture with force vectors from the force plate shown "inside the body". For a detailed description of the Analog Module, see the Analog Chapter in the APAS Manual.

    

6. Kinetic Module:
   
   
   • One of the most unique features of the Ariel Performance Analysis System is its capability to calculate Kinetic forces and moments from the kinematic parameters. By utilizing Anthropometric measurements from the biomechanical literature in the Anthro Module, the investigator may choose the kinetic Module to utilize the inverse dynamics model to calculate joint forces and moments. For more detailed description of the Kinetic Module, see the Kinetic Chapter in the APAS "on line" Manual.
   • Another feature of the Force plate is the utilization of the input ground reaction forces for improving the model. However, if the force plate is absence, it is still possible to calculate the reactions forces and the joint forces and moments utilizing the kinematic and anthropometric measurements.
   • In instances where external forces, such as holding a tennis racket, the Kinetic Module allows input of the racket parameters to calculate the joints forces and moments including the external forces from the tennis racket. The same procedure can be utilized for any other external force applied to the body, such as back packs, a shovel, or any other load applied to any point in the body.

    

7. Force Plate:
   
   
   • The Ariel Performance Analysis System permits the combination of as many as four (4) force plates simultaneously to calculate orthogonal forces and moments generated by the ground reaction forces. The center of pressure is calculated considering all the plates involved. Therefore, if four plates are involved, then the center of pressure will be calculated relative to all four plates. If only one plate is used, the center of pressure is calculated relative to this plate.
   • Another unique measurement is the calculation of the center of pressure relative to body perturbations and small movements for neurological disorder balance calculations.

    

8. EMG:
   
   
   • All parameters utilized in surface and needle EMG are calculated and displayed.
   • Power Spectrum, Fast Fourier Analysis, and many other kinds of integration are incorporated into the EMG software. Envelope, Time- and value-reset, area reset, accumulative integration, and other calculations can be performed.
   • Also, various time measurements for reaction time data as well as other neuromotor activities can be measured. Median and Mean frequencies are measured as a function of fatigue. This Module includes measurements which described in Muscles Alive by Basmajian and De Luca. Also, a detailed documentation of the Analog Module is described in the Analog Module Manual.