Soft Landing of a Hybrid Rocket Thruster Powered Platform: Hardware-in-the-Loop Simulation

Soft landing, defined as a controlled and gentle touchdown which prevents any damage, is a crucial phase of planetary landing modules and vertical take-off and landing aircraft. This paper discusses the soft landing of a hybrid rocket-thruster-powered platform using a hardware-in-the-loop simulation (HILS) framework. The concept of a hybrid rocket thruster-powered platform was conceived as part of a system development study aimed at bringing out an effective propulsion unit for achieving VTOL in aircraft and UAVs. To simplify the scope of the preliminary investigation, the platform’s movement was restricted to vertical translation. The hardware-in-the-loop simulation setup integrates a lab-scale hybrid rocket thruster in the hardware module with the simulated platform dynamics model. A control algorithm was implemented to regulate/tweak the real-time hardware—the thruster—to enable the simulated model of the platform to track a predefined descent velocity profile. A proportional-integral-derivative (PID) controller regulated the oxidiser valve opening, controlling the oxidiser flow rate to the hybrid rocket motor and, consequently, the thrust to maintain the desired velocity profile of the platform during the descent. The hardware-in-the-loop simulation setup demonstrated a successful soft landing of the platform with a touchdown velocity of less than 1 m/s.