1. The essential idea of incremental nonlinear control laws consists of a reformulation of (part of) the system dynamics. This reformulation was first used as a simplified nonlinear dynamic inversion technique,5,6and later more formally proposed by Sieberling et al. as incremental nonlinear dynamic inversion (INDI).7The method has primarily been used for angular rate tracking and is applied to fixed-wing aircraft, spacecraft, quadcopters and helicopters.8-11
2. When stability must be guaranteed for the cascaded nonlinear control systems, the Lyapunov-based backstepping procedure is a more promising method. The incremental descriptions were first applied to the backstepping control procedure by Acquatella et al.12,13Using backstepping control, adaptation strategies of model parameters are derived such that stability can still be guaranteed.14-17