Modelling and multivariable control of a gearless, electrically actuated vibrator

Derivation of a generic dynamic model of a novel, gearless electromechanical vibratory pile-driver, in which the vibratory force is generated by four independently driven eccentric masses, is described. Theoretical predictions for the circulating and oscillatory power flows throughout the system, and the load torque disturbances which are imposed on the individual drives, are used to determine the required rating of the vector-controlled induction machine drive systems. The dynamic models are subsequently used for the design of linear quadratic multivariable controllers which provide real-time synchronisation of both the angular velocity and relative phase-displacement of the eccentric masses, so that both the amplitude and frequency of the resulting vibration can be independently controlled, and for trade-off studies between the system efficiency and performance regulation and the steady-state and peak power flows. Results from onsite trials are used to verify the predicted dynamic behaviour of the developed vibratory pile-driver in terms of both the vibration characteristics and power management, and thus validate the derived theoretical models.