Fig. 14. The measured control characteristics of the bumblebee system are compared with the characteristics of a human pilot-vehicle system (McRuer and Jex, 1967). For the human system, the control characteristics are fitted with a transfer function, H(s)= _gc,human/s·e^-e,humanS (the crossover model). On the other hand, the control characteristics in the bumblebee system can be approximated as B(s)=[_gc,bumblebee/(s+3)]^2.e^{-e,bumblebeeS}, which could be called `the square crossover model'. The bumblebee system is observed to possess higher gain at <_gc than the human system, indicating higher performance in terms of the steady-state characteristics. The gain crossover frequency in the bumblebee system (_gc,bumblebee) is approximately twice as large as that in the human pilot-vehicle system (_gc,human). Because larger _gc causes larger bandwidth in the system, the bumblebee system is revealed to possess superior quick response characteristics. We already verified that the bumblebee system possesses substantial phase margin (PM; Fig. 13), indicating that the system possesses excellent damping characteristics. The bumblebee system was, therefore, revealed to have superiority in terms of the steady-state and transient (i.e. quick response and damping) characteristics, in comparison with the human pilot-vehicle system.