Figure 3

Theoretical transfer function and estimated frequency response functions $\left(C_{{\mathit{\theta }}_A\to T_A}\mathbf{,}{C}_{{\mathit{\theta }}_A\to T_H}\mathbf{,}{C}_{{\mathit{\theta }}_H\to T_A}\mathbf{\text{and}}{C}_{{\mathit{\theta }}_H\to T_H}\right)$. Results of the model simulations in the presence of pink and white noise during the condition with a platform acceleration and perturbation torque around the ankle are depicted (PLT-N; open dots) and during the condition with one perturbation (PL-N; solid grey dots). The bold solid line represents the model transfer function of the stabilizing mechanisms. Applying two independent perturbations in combination with a multivariate closed-loop system identification method resulted in a correct estimation of the stabilizing mechanisms (FRF 2 perturbations, indicated with open dots), whereas one perturbation resulted in an erroneous estimate (FRF 1 perturbation, indicated with solid grey dots).