Inertially compensated force plate: a means for quantifying subject's ground reaction forces in non-inertial conditions.

A system for the measurement of forces in noninertial reference systems, and a possible solution to compensate force plate readings by means of accelerometers were investigated. If the force plate can be considered a rigid body, six linear accelerometers can measure all linear and angular accelerations of the instrument in 3-D space. However, by using nine accelerometers in a proper layout, the force and moment generated by the movement of the plate can be quantified in a way that eliminates the errors due to the time integration of the accelerations. By doing so, no temporal limits are imposed to the compensation. A one degree of freedom numerical model was implemented to evaluate the importance of main error sources in the estimation of inertial forces using accelerometers with different technical characteristics. The inertial compensation of the force plate along one axis was tested, and the performances of a piezoelectric accelerometer and a capacitive accelerometer were compared. With the proposed inertially compensated force plate, accelerations up to 5 g's in amplitude and frequencies from 0 to 100 Hz can be compensated by means of capacitive accelerometers. Such a device can be used for force measurements in moving vehicles, or any situation where the surface on which the instrument is mounted is moving or vibrating.