*6.3. Recursive Least-Squares*

The RLS model proposed in Section 4 was fed with the validation data in order to be compared with both previous models. The model output can be seen in Figures 9 and 10. RLS captured the overall behaviour of the neck within acceptable tolerance. The mismatch observed is attributed to the plant non-linearity. The fit values are 78.0448% for pitch and 82.7217% for roll. An overall comparison of the results can be found in Table 3.

**Figure 8.** Control signal for the validation test.

**Figure 9.** Validation of the pitch output.

**Figure 10.** Validation of the roll output.

**Table 3.** Fitness of models on the validation data.

