Force plate

Force plate A plate used for holding plugs in place in compression molding. 

Gold, H. Czupryna, G. Robinson, J. M. Levy, R. D. Purifying Air Force Plating Baths by Chelate Ion Exchange Final Report to Headquarters, Air Force Engineering and Service Center, Tyndall AFB, FL, Foster-Miller, Inc., July 1985. 

The 3-D ground reaction force vector, the vertical ground reaction torque and the point of application of the ground reaction force vector (i.e., center of pressure) are measured with force platforms embedded in the walkway. Force plates with typical measurement surface dimensions of 0.5 x 0.5 m are comprised of several strain gauges or piezoelectric sensor arrays rigidly mounted together. 

A strike-through is whenever the blade comes into contact with the force plate. This is depicted in the graph by the red lines, with a value of 1 when there is a strike-though and 0 when there is no strike-through. 

The high value of 234.4 N in the coursewise direction in the jersey structure was closely analysed and it was conclnded that it had a valid result. There was a cut-through even before the contact point at 234.4N, but the blade did not make contact with the force plate as the fabric was pulled by the blade and the accumulation of the loops made the blade to jump. 

The accelerations and the information about other forces exerted on the body (e.g., the recordings from a force plate) can be input to the equations of motion to compute the correspfonding joint reaction forces and moments. 

Commercially available force platforms use one of two different measuring principles to determine the applied load. The first type of force plate uses strain gauge technology to indirectly measure the force applied to the plate (e.g., AMTl and Bertec), while the second type uses piezoelectric quartz (e.g., Kistler). Piezoelectric materials produce an electrical charge directly proportional to the magnitude of the applied load. In this section we focus on how the output of a force platform is used in an inverse dynamics analysis, without considering how the forces and moments detected by the plate are calculated. 

Force plate n. The plate that carries the plunger or force plug of a mold and the guide pins or bushings. Since the force plate is usually drilled for steam or water lines, it is sometimes called the steam plate. 

After setup and calibration of the Selspot system and the force plate, subjects were instrumented as follows ... 

Have subject stand centered on the force plate in a relaxed position and position the 4 cameras so that each LED can be seen by at least two cameras. 

Place calibration frame on force plate and calibrate the camera setup. Place a sheet of paper on the force plate and draw 2 crosshairs from the corners of the plate to identify the center of the plate. Hang a wire (radio opaque) from an IV pole with a plumb bob near the floor with 3 LEDs attached to the wire at about shoulder, mid-spine and hip levels. Center the plumb bob within 1 mm of the center of the force plate and place an LED at the FP center. Record with the Selspot system for 2 seconds to identify the location of the origin of the FPCS with respect to the origin of the SCS. This is achieved by measuring the distance between the LED at the hip level and the center of the force platform. 

Have the subject stand with feet apart in as a relaxed position as possible, centered on the force plate. Have the subject concentrate on relaxation and rotate slightly over the hip joints to minimize the sensation of hip joint forces stabilizing the trunk. (It is our experience that this procedure creates the best reproducibility for relaxed standing posture.) Trace the foot positions of the subject on the paper over the force plate. Record a measurement for the Selspot and the force platform for three seconds at the rate of 125 frames per second in this relaxed position and label this data position 1, run 1. 

Have the subject walk around and return to the same position on the force plate and redo the same relaxation procedure aligning the feet to the previously traced foot positions. Record the Selspot and force plate measurements for three seconds at the rate of 125 frames per seconds and label this data set position 1, run 2. Repeat this procedure 3 more times, completing 5 runs in the relaxed position 1, runs 1-5. 

Have the subject stand with their feet in the same position centered on the force plate and then have them place their hands on the IV pole at the level of their nose (in Europe the standard position used to X-ray a subject s spine in the sagittal projection) so that their arms are completely above and in front of their spine. This position assures an X-ray with all the vertebral bodies viewable. Mark the level of the hands on the pole so that the subject can easily reproduce this position for subsequent runs. Have the subject concentrate on relaxation and rotate slightly over the hip joints to minimize the sensation of hip joint forces stabilizing the trunk in this position. Record a measurement for the Selspot and the force platform for three seconds at the rate of 125 frames per second in this relaxed position and label this data position 2, run 1. Have the subject walk around and return to the same position on the force plate and redo the same positioning procedure. Record the Selspot and force plate measurements for three seconds at the rate of 125 frames per second position 2, run 2. Repeat this procedure 3 more times, completing 5 runs in the relaxed position 2, runs 1-5. 

Transport the plumb line on the IV pole with its hand position marked, the force plate paper with force plate center and foot positions marked and the subject to the X-ray facilities at the Spine Institute of the Orthopaedic Department at Doctors Hospital (about 2 blocks away from the Biomechanics Laboratory) with all of the LEDs in place. Have the subject stand in the second position, with arms out of the path of the X-ray in the sagittal plane view. Align the subject as closely to the true sagittal plane as possible by viewing along the sight of the X-ray beam and noting the position of the shoulders and patellas as in the plane of the... 

Preliminary Resuits to Date. For the 3 subjects measured the arm positioning maneuver for sagittal X-rays seems to alter the spine curvature only a few millimeters. The force plate vector aligns very closely to the hip joint center (estimated from boney landmarks) and slightly anterior to the L3 and L4 vertebral body centers. 

PUNCH Oft FORCE PLATE PUNCH OW FOftCE SUPPORT PLATE... 

Upper Force Plate 8. Pin Plate 14. Molded Article... 

---