Vibration Control of a Structure and a Rotor Using One-sided Magnetic Actuator and a Digital Proportional-derivative Control

The present work aims at vibration control of a structure/rotor using a one-sided magnetic actuator. For such an actuator, the actuator force is a nonlinear function of current through the coil of the actuator and the gap between the actuator and the structure/rotor. Though the actuator introduces sufficient nonlinearity to the system, it has the advantage that, for applying force in a direction, this actuator needs to be placed in only one side of the structure/rotor. For vibration control of the structure/rotor, a simple digital proportional derivative (PD) control technique is suggested here. It is considered that the displacement signal from the sensor is sampled at specific instants of time and a series of discrete values of displacement is made available to the digital controller. The controller processes the above values of displacement to compute the values of control current that produces the values of appropriate control force at the corresponding instants. The input current to the actuator is kept constant between two consecutive sampling instants. The response of the controlled system (the structure/rotor along with the digital controller) is computed using standard time-marching algorithms (with time steps much smaller than the sampling interval). The effect of the sampling interval in the response pattern is observed for a single-degree-of-freedom (SDOF) system, a finite element model of a beam and a four degree-of-freedom model of a rotor.