Six-Degree-of-Freedom Accelerations: Linear Arrays Compared with Angular Rate Sensors

A 3-2-2-2 array of linear accelerometers and a combination of a triaxial linear accelerometer and a triaxial angular rate sensor were mounted into a Hybrid III 50th percentile male ATD head-form and compared in a variety of short- and long-duration events. An appropriate low-pass filter cutoff frequency for differentiating the angular rate sensor data into angular accelerations was found by using a residual analysis to find individual cutoff frequencies for the three center of mass (COM) linear accelerometer channels and the three angular rate sensor channels and taking the arithmetic mean of the six cutoffs. The angular rate sensors provide more accurate rotational rates than integrated angular accelerations calculated from arrays of linear accelerometers and are less cumbersome, especially for events lasting longer than 200 ms. The method of taking the arithmetic mean of the component cutoffs works because residual curves are reasonably insensitive to small variations in the cutoff frequency in the band between linear and rotational cutoff frequencies. Angular rate sensors also appear useful for integration into 3-2-1 arrays to provide a more robust nine-channel array than the predominant 3-2-2-2 linear array.