Reprinted from the JOURNAL OF THE AERONAUTICAL SCIENCES Coupled Oscillations of Aircraft Engine- Propeller Systems
The coupled oscillations of a flexible propeller and an aircraft engine with arbitrary number of cranks is investigated. In the first part of this paper a practical method is developed to determine the complete dynamical characteristics of a rotating vibrating propeller of arbitrary shape, and the legitimacy of the approximations is checked with a numerical example. In the second part the first nine torsional frequencies of a V-12 engine, with a flexible propeller are calculated and compared to the frequencies of the free-wheeling propeller and those obtained by considering the propeller as rigid. The simultaneous influence of the engine speed on all nine frequencies and the general procedure to compute the complete critical speed spectrum are also indicated.
In this study the proximity hovering orbital dynamic model and control method are investigated. This dynamic model, constructed on the orbit elements, gives the relative motion between the chief satellite and the deputy satellite in the space. The continuous closed-loop orbital control law is developed based on the dynamic model, which means that through continuous limited thrust control the deputy satellite would transfer into a new maneuvering orbit, not the natural Kepler orbit. The simulation result shows the effectiveness of this dynamic model and the control law. The deputy satellite can proximity hover around the chief satellite with a little energy consume (3.79m/s velocity increment) when the desired radial distance is 500m during one orbit period.