Spin.Works has recently developed new high-performance nonlinear guidance and control laws applicable to atmospheric entry flights. The first application of this new approach was targeted towards a precision-landing Mars mission with a low lift-to-drag vehicle (Huygens-like capsule).
The limited aerodynamic manoeuverability of the vehicle, together with the high initial position and velocity uncertainties and the exceedingly uncertain Martian atmosphere provided the perfect backdrop to a demonstration of this guidance and control system’s potential, with the 6DOF Monte Carlo results showing a strong trajectory tracking performance followed by systematically safe and highly precise parachute deployment events.
The nonlinear guidance and control essentially relies on a technique known as nonlinear dynamic inversion, whereby the inverse functions of the translational (guidance) and angular (attitude control) equations of motion are derived with the purpose of calculating the system inputs required to obtain a set of specific system outputs.
In this case, the attitude control laws involve obtaining the inverse function to both the equations for the kinematics and the dynamics of angular motion, which results on a direct relation between required attitude and the necessary angular moment to track it. The guidance laws, on the other hand, involve the inversion of the translational equations of motion, with the goal of relating the range, drag and heading with the bank angle needed to track them.
The project included the following tasks:
Credit: NASA JPL