Teflon impactor were (β, γ) ¼(4.0 0.5, 0.70 0.05). Force histories obtained from original CZ theory, experiment, and modified CZ theory are displayed side by side in Fig. 11.6. It can be seen that the exaggerated transient force histories obtain from original CZ theory (see Fig. 11.6a) for soft material impactors are modified (see Fig. 11.6c) based on the understanding obtained from experiments (see Fig. 11.6b). In addition, the force peaks of the profiles where modified using a universal ς and ε value found to be (ς, ε) ¼(1.50 0.10, 1.460 0.005) for best matched results. Notice that the dissipation parameter γ and solution time discrepancy parameter β depend on the impactor material. Delrin Acetal has a higher γ - parameter than Teflon because, as physically witness in our lab experiments although not measured, its restitution coefficient is significantly and visibly greater than Teflon’s. Delrin Acetal impactor behaves like a tennis ball, restoring a significant amount of energy during impact which other impactor materials transmit to the plate. On the other hand, Teflon has greater β-parameter due to its soft polymeric nature that is quantized by its low elastic modulus. Inspecting Eqs. 11.10 and 11.13, it can be observed that a low elastic modulus will lead to divergence of the solution in the time domain, resulting in the need for the β-parameter to mitigate the mathematical bias. 11.7 Conclusion In this work, we have successfully shown that CZ theory can be modified to obtain more accurate solutions by implementing a novel spiral sensor array called Theodorus spiral sensor cluster (TSSC) and two ad-hoc AUS processing techniques called the lag index (LI) and dominant frequency band (DFB) for impactor type, low velocity impact classification and the consequent application of empirically determined modification parameters. 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