CubeSat attitude and position control systems based on LPV and sliding mode methods

Spacecraft are subject to strict requirements in terms of angular position and actuation limits so good control performances combined to small inputs must be achieved. The robustness properties of both sliding-mode controllers (SMC) and Linear Parameter Varying controllers (LPV) make them suitable for many real situations corroborated by their solid mathematical bases. On the other hand, real SMC exhibit high-frequency oscillations in the plant output, called chattering, which lead to excitement of unmodeled dynamics. This issue can be mitigated both by exploiting an higher order sliding mode controller and by substituting the classical sliding mode control law with an approximated smoother function. This is what it has been described in this paper: a second order twisting sliding mode controller has been designed in order to achieve an optimal combination between control law flexibility, robustness and precise attitude control of a CubeSat. Then an LPV (Linear parameter varying) controller has been implemented for the same case in order to compare performances and uncertainty rejections, both actuated by reaction wheels. Finally, a first order sliding mode controller has been partially implemented for the position control of the analyzed spacecraft, by exploiting cold gas thrusters as actuators.