Fig. 2. Block diagram of simplified control model. The `mechanics' box represents the torsional dynamics, and relates the body moment, u, to the body angle, . The antenna box is a simplified model of the antenna sensing kinematics, and it dynamically relates the cockroach angle, , to the antenna sensor measurement, d. We fit a simplified neural controller (in the broken box), in which the error between a nominal `desired' wall-following distance, d, and the measured distance, d, is fed back through a PD-controller. This control model enabled us to test PD-control (K_D=0) against P-control (K_D=0).