Drag-Tracking Guidance for Entry Vehicles Without Drag Rate Measurement

TL;DR

This paper introduces a robust entry guidance law that achieves drag-tracking without direct drag rate measurement by using a high gain observer and state feedback control, ensuring stability despite uncertainties.

Contribution

The paper presents a novel drag-tracking guidance law that eliminates the need for direct drag rate measurement using a high gain observer and ISS-based control design.

Findings

The guidance law achieves input-to-state stability under uncertainties.

Simulation results confirm the effectiveness of the approach.

The method simplifies implementation by removing the need for drag rate sensors.

Abstract

A robust entry guidance law without drag rate measurement is designed for drag-tracking in this paper. The bank angle is regarded as the control variable. First, a state feedback guidance law (bank angle magnitude) that requires the drag and its rate as feedback information is designed to make the drag-tracking error be input-to-state stable (ISS) with respect to uncertainties. Then a high gain observer is utilized to estimate the drag rate which is difficult for a vehicle to measure accurately in practice. Stability analysis as well as simulation results show the efficiency of the presented approach.