Evaluation of Time-Shifted Feedforward Control for Unmanned Helicopter Path Tracking

Abstract

A novel approach to improve the path tracking performance based on time shifted feed-forward signals is presented. It uses approximately linear closed-loop dynamics through feedback linearization of the ARTIS unmanned helicopter. The flight controller is currently in use to track nonlinear trajectories represented by piece-wise cubic splines. Feedforward signals shifted in time with varying and constant time-shifts are evaluated to improve the suboptimal tracking behavior. The problem is illustrated for a representative path and the process of determining the time shift is discussed. Having runtime performance advantages, the constant variant of time-shifted feedforward signals is chosen for onboard implementation. To validate the approach, it is implemented onboard our flying rotorcraft test bed and flight test results showing the improved tracking performance are presented.