Precision Landing and Testing of Aerospace Vehicles.
Planetary precision landing in non cooperative sites has been a major challenge. An indoor novel planetary precision landing facility known as Surrey Precision Landing Facility (SPLF) has been developed to bridge the gap between software simulations and outdoor expensive UAV based planetary precision landing testbeds. The 3D motion capture system provides real time accurate navigation data by removing the uncertainty in the position, and thus allows the flexibility to test the planetary terminal descent based Guidance and Control algorithms on quadrotors safely, rapidly, repeatedly with very low operating cost. Quadrotors can follow the trajectory of a planetary lander during its terminal descent. Model Predictive Control (MPC) incorporates input/output constraints in the calculation of the control law and thus can be used for the planetary terminal descent scenarios. Feasibility and computation time have been a key hindrance in practical validation of MPC for quadrotor control. Therefore, a novel single stage linear MPC algorithm in a state space framework has been developed to improve feasibility and computation time over Optimal MPC (OMPC) Laguerre OMPC (LOMPC) and Steady State (SS) OMPC (SSOMPC) by linking reference governor, Closed Loop Paradigm, Steady State Target Optimization and Laguerre function techniques. The novel SSLOMPC algorithm is simulated to test its performance on a simple two state model, and then has been implemented in simulation and practically validated at SPLF on a quadrotor for the set point tracking scenarios. Disturbance rejection and offset free tracking is achieved via a Kalman filter. Simulated and practical implementations of PID, LQR and MPC control laws on a quadrotor helicopter for the Mars terminal descent phase has been performed at SPLF, where SSOMPC/SSLOMPC successfully demonstrates the ability to respect the control input and output constraints. The conclusion is that the use of Steady State OMPC with Laguerre functions improves feasibility and computation time. MPC can be used as a practical candidate controller for planetary precision landing scenarios. The tracking errors for PID, LQR and MPC control laws were less than 10 cm in the practical tests.