The MPC Attitude Control with Integration for VELOX-II

Abstract

VELOX-II that has been launched on 16th December 2015 is the second CubeSat built by the Satellite Research Centre (SaRC) of Nanyang Technological University (NTU). However, according to the operation data of VELOX-II in orbit, it can be observed that there is a large steady state error and the error becomes the most crucial factor for the pointing error. In this paper, Model Predictive Control (MPC) with integration was proposed in order to offset the steady state error. At first, the MPC with integration was based on a state space model with an incremental input aiming to add an integral item. Secondly, a quadratic cost function was designed to derive the control law of MPC with integration. Finally, a series of analysis and simulations were implemented for VELOX-II’s MPC, PD, Sliding Mode Control (SMC) and MPC with integration, respectively. The theory analysis and simulation results revealed that the steady state error is from environmental and actuator’s disturbances, and it can not be offset by VELOX-II’s MPC, PD and SMC controllers, but can be eliminated by the MPC controller with integration; comparing with PID, the MPC has much improved attitude tracking performance, especially in the aspect of time delay; different with SMC, the MPC with integration is easy to be come true on the 8051 chip because of the smaller amount of computations and codes; VELOX-II using the MPC controller with integration can achieve a higher pointing accuracy.