Design and Experimental Characterization of Electromagnetic Shock Absorbers for Landing Gears

A fundamental step on planetary explorations is to achieve the capability to perform a safe landing on planet surface to perform the activities that are impossible to perform from orbit, including human settlement. The Active Shock Absorber (ASA) technology has been identified as a key issue enabling future planetary explorations. The ASA could lead to an efficiency improvement for Landers (e.g. reusable landing gear, hopping mobility exploitation, etc.), also could be used into Rover suspensions (e.g. the advantage of utilization of ASA technology into Rover suspension is the capability to harvest energy in the process of vibration reduction). Among different possible active shock absorbers technologies, electromagnetic actuators have been selected because of the relatively simple control architecture and for the absence of freezable fluid inside the mechanisms. An important improvement of ASA with respect to traditional dampers is the capability to work in a bidirectional way. In fact, during landing ASA works as a damper, assuring a safe landing and energy dissipation, after landing, ASA could be used to adjust the lander attitude and even to actuate the entire leg. The walking/hopping capability is not explored in this study, but is considered in the definition of leg kinematic scenario. The Moon South Pole is considered as reference scenario for its challenging morphology, due to its irregular surface. The optimal landing configuration (Tripod landing gear) has been identified using CAD drawings and multibody analyses and the load and energy scenario has been estimated. A design methodology based on a Simulink model of ASA has been developed this model has been used in co-simulation with the multibody software to optimize the design and verify the initial hypothesis. Prototypes have been realized and validated experimentally in active and passive configuration both at steady state and vibration conditions. A dedicated test rig has been developed for the purposes of the project. The good correlation between the experimental and the numerical results is a proof of the model robustness and the potential performance of the system. Finally a mass saving strategy has been assessed.