The application of a smart landing gear oleo incorporating electrorheological fluid

The objectives of this paper are to outline the use of Electrorheological ( ER) fluid within an aerospace system. The advantages of ER fluid-based syst ems are given followed by design considerations which include those related to the non-linear behaviour of an ER fluid subjected to oscillatory shear. A control strategy is outlined for the use of a smart landing gear (LG) ol eo incorporating ER fluid. The paper also considers the issues associated w ith airworthiness requirements and ER fluid devices. For airworthiness approval a smart oleo based LG system must primarily be s hown to be safe and as such has to be fault tolerant. A major failure for t his application would be if the control strategy failed and the oleo dampin g coefficient was consistently too low; a backup system is therefore incorp orated into the design and other potential modes of failure considered. A semi-active control strategy applied to a variable damping coefficient LG oleo has specific requirements, partly due to the fact that for the take-o ff and landing phases of flight they are different. A semi-active control s trategy is outlined based on the requirements for the alteration of damping coefficient according to the phase of an aircraft's flight. The strategy i s the focus of current work to estimate the effectiveness of semi-active vi bration control as applied to an undercarriage.