A master thesis from Aalborg University
Linear Parameter-Varying Control of the VEGA Launch Vehicle
[Lineær Parameter-Varierende Kontrol af VEGA-raketten]
Author(s)
Term
4. term
Education
Publication year
2021
Submitted on
2021-06-02
Pages
75 pages
Abstract
Fokus for denne afhandling har været at designe et Lineær Parameter-Variende (LPV) kontrolsystem til den europæiske raket VEGA. Mere præcist har målet været at stabilisere raketten under dens atmosfæriske flyvning fra liftoff til Main Engine Cut Off (MECO), når der er forstyrrelser, såsom vindstød, sensorstøj og beregningsforsinkelser. Specialet dækker en afledning af en raket-model i 3D og teori, design og simulering af en LPV-controller. Raket-modellen er afledt af translationelle og rotationsdynamiske ligninger, der påvirker en seks grader af frihed raket. Raketten er forenklet til en 2D-model, og Jacobian lineariseringer udføres på en systematisk måde for at udlede en lineær tilstandsrepræsentation. Denne rapport opstiller derefter velkendte krav til en typisk raket under opsendelse. En LPV-controller-model er designet med en lower Linear Fractional Transform (LFT) -konfiguration og suppleres med et udvalg af frekvensafhængige filtre på input- og outputkanalerne designet til at opfylde de opstillede krav. Endelig simuleres Raket-kontrolsystemet gennem en lineær LPV-simulering med brugerdefinerede input. Resultatet fra simuleringen konkluderer, at raketten er stabil og fungerer som forventet, samtidig med at den opfylder dens krav.
The focus of this thesis has been to design a Linear Parameter-Varying (LPV) control system for the European Launch Vehicle (LV) VEGA. More exactly, the objective has been to stabilize the LV during its atmospheric flight from liftoff to Main Engine Cut Off (MECO) when disturbances are present, such as wind gusts, sensor noise and computational delays. The thesis covers a derivation of a 3D LV model and theory, design, and simulation of an LPV controller. The LV model is derived from translational and rotational dynamic equations affecting a six Degrees of Freedom (DoF) LV. The LV is simplified to a 2D model and Jacobian linearizations are conducted in a systematic manner to derive a linear state space representation. This report then establishes wellknown requirements for a typical LV during ascent. An LPV controller model is designed with a lower Linear Fractional Transform (LFT) configuration and is augmented with a selection of frequency dependent filters on the input and output channels designed to satisfy the requirements. Lastly, the LV control system is simulated through a linear LPV simulation with user specified inputs. The result from the simulation concludes the LV is stable and is operating as intended while satisfying its requirements.
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