Discrete-time flatness-based control for a twin rotor helicopter with an Extended Kalman filter

Abstract

In this paper, a discrete-time flatness-based control for a twin rotor aerodynamic system with two degrees of freedom is proposed that outperforms a standard quasi-continuous implementation, cf. [1]. A control-oriented state-space model is derived using Lagrange's equations. The resulting nonlinear fourth-order model possesses two control inputs, and is affected by two unknown disturbance torques due to modelling simplifications and unmeasurable torques. Accordingly, a discrete-time Extended Kalman Filter is employed to estimate these lumped disturbances and unmeasurable states as well. The proposed control approach in combination with the discrete-time Extended Kalman Filter is implemented and validated on a laboratory test rig. The effectiveness of the discrete-time flatness-based control is highlighted by experimental results showing an excellent tracking behaviour.