Fig. 7. Average cockroach distance to the wall y (A,B) and body angle (C,D) as a function of distance traveled along the 45° angled wall for two different speed groups: Slow (A,C) and Fast (B,D). The actual cockroach data (black) are compared to predictions from the PD-control model (red) using the parameters from Table 1. To show the importance of the derivative gain, K_D, we tested the controller with the K_D=0 (P-control, blue); note that for P-control, performance degrades with increasing speed as expected. The derivative gain significantly improved the fit for the speeds tested.