  Previous results reported in the robotics literature show the relationship
between time-delay control (TDC) and proportional-integral-derivative control
(PID). In this paper, we show that incremental nonlinear dynamic inversion
(INDI) - more familiar in the aerospace community - are in fact equivalent to
TDC. This leads to a meaningful and systematic method for PI(D)-control tuning
of robust nonlinear flight control systems via INDI. We considered a
reformulation of the plant dynamics inversion which removes effector blending
models from the resulting control law, resulting in robust model-free control
laws like PI(D)-control.
