Modelling and multivariable control of a gearless, electrically actuated vibrator

Derivation of a generic dynamic model of a novel, gearless electromechanica l vibratory pile-driver, in which the vibratory force is generated by four independently driven eccentric masses, is described. Theoretical prediction s for the circulating and oscillatory power flows throughout the system, an d the load torque disturbances which are imposed on the individual drives, are used to determine the required rating of the vector-controlled inductio n machine drive systems. The dynamic models are subsequently used for the d esign of linear quadratic multivariable controllers which provide real-time synchronisation of both the angular velocity and relative phase-displaceme nt of the eccentric masses, so that both the amplitude and frequency of the resulting vibration can be independently controlled, and for trade-off stu dies between the system efficiency and performance regulation and the stead y-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.