LQR based attitude control of sun pointing space capsule using magnetic torquers
- Paper number
IAC-08.C1.8.2
- Author
Mrs. Chinna Ponnu, ISRO Satellite Centre (ISAC), India
- Coauthor
Mr. P. Natarajan, Indian Space Research Organisation (ISRO), India
- Coauthor
Dr. N.K. Philip, Control Systems Group, ISRO Satellite Centre, India
- Coauthor
Dr. Agrawal V.K., Indian Space Research Organisation (ISRO), India
- Coauthor
Dr. N.K. Malik, Indian Space Research Organisation (ISRO), India
- Year
2008
- Abstract
A new three axis fully magnetic attitude controller based on a time varying, full state feedback Linear Quadratic Regulator (LQR) Control law is designed for ISRO’s Space Capsule Recovery Experiment (SRE) on orbit phase control which requires roll axis sun pointing. The under actuated nature of the system along with its approximate periodicity generates a challenging feedback controller design problem. The goal of this system is to achieve microgravity environment for the payloads of SRE. This paper describes the system modelling, LQR design and onboard implementation and simulation details. To avoid onboard solving of Riccati equation, solution of Riccati equation is computed on ground based on time slice approach. This gain scheduler is stored onboard. The roll axis sun pointing requirement results in different attitude in inertial frame with respect to season / time of year. A simple scheme was evolved to shift the index in the gain scheduler table. The computation of Sun vector, Orientation quaternion for the sun pointing orbit frame with respect to ECI frame, gravity gradient torque computation, IGRF model based Geomagnetic field are also implemented in the simulation program. Inspite of extensive testing on ground, on orbit flight performance gives new surprises. The flight experience related to magnetic attitude controller performance are discussed. Digital simulation results as well as actual in flight performance are provided. The controller is robust with respect to the satellite’s moments and products of inertia and also for different seasons / time of the year. This three axis attitude control with magnetic torquers alone scheme can be implemented for spacecrafts having microgravity requirements with relaxation on attitude pointing accuracy.
- Abstract document
- Manuscript document
(absent)