Nonlinear System Identification of Variable-Pitch Propellers Using a Wiener Model

Abstract

This work presents the system identification of a variable-pitch propeller (VPP) powertrain, encompassing the full actuation chain from PWM signals to thrust generation, with the aim of developing compact models suitable for real-time digital twinning and control applications. The identification is grounded in experimental data covering both static and dynamic responses of the system. The proposed model takes the form of a Wiener-like architecture, where the PWM inputs are first processed through linear first-order dynamics describing the motor and pitch actuation, and the resulting states are then mapped via a static nonlinear relation to the generated thrust. This structure naturally arises under the assumptions that the electronic actuation operates on a much faster time scale than the mechanical response, and that the contribution of the aerodynamically induced torque is negligible in the tested regime. The resulting parsimonious representation is shown to reproduce the measured dynamics with good accuracy while remaining interpretable and computationally light, thereby providing a practical basis for integration in control-oriented digital twin frameworks.

Figures (10)

• Figure 1: (a) Experimental setup with IR sensor, ESC, and load cell. (b) CAD model of the custom variable pitch mechanism, showing the linear actuator, rotor hub, blade roots, and lever pull rod.
• Figure 2: Block diagram for the closed-loop control architecture for motor RPM (PI controller) and blade pitch (custom PD + LAC controller).
• Figure 3: Block diagram of the closed-loop system.
• Figure 4: Thrust map averaged over 5000 samples. Blue dots represent the measured data, red surface is the fitted model, $\hat{T}(\omega,\beta)$, a), and the thrust coefficient, $C_T$, b).
• Figure 5: All fitted normalized responses to RPM steps. Colors represent measured data, and black lines are the fitted models.