A reduced rotor model using modified SEREP approach for vibration control of rotors

For analysis and control of dynamic behaviour of continua, equations of motion are usually obtained after discretizing the continuum into finite elements. Thus discretization gives rise to a set of simultaneous differential equations, the number of which increases with the fineness of discretization. As an associated effect, increasing fineness increases the number of states, many of which are difficult to measure and feedback, due to impracticability of location of measurement or non-availability of proper sensor, in addition to the constraint on the cost of sensors and computation. Solution to the above problem calls for a suitable scheme to reduce the problem size, however, keeping the modal information unspoilt as far as possible. For a vibratory system, a reduced model is built by retaining modes with higher participation factor and also choosing conveniently within the retained modes, a number of pre-decided measurable states. Fewer state equations are thus found helpful for formulating suitable control law, applicable for improving the system dynamic performance over uncontrolled condition. This paper attempts first to obtain a reduced model for a rotor–shaft system, generally a non-self-adjoint system, and next uses the reduced model to implement active vibration control action using a single, stator-mounted electromagnetic actuator suitably located at a section along the rotor–shaft.

► Modified SEREP proposed to reduce model size of non-self-adjoint linear time-invariant systems.
► The reduction scheme preserves important dynamic modes after eliminating immeasurable states.
► Controlled reduced model closely simulates dynamic behaviours of controlled un-reduced system.
► Dynamic simulation of a flexible rotor-bearing system confirms the efficacy of modified SEREP.