Amplitude and frequency control of a vibratory pile driver

This paper describes the digital control of a vibratory pile driver in whic h the vibration is generated via two tandem pairs of electrically driven, g eared, contra-rotating eccentrics. Experimental results are included to sho w the controller-induced system dynamics for a variety of load conditions, and to highlight the fact that, if the relative phase of the eccentric pair s is not controlled, the natural tendency at high excitation frequency is f or the pile driver to operate with a low vibration amplitude. An analytical technique for identifying the system parameters is presented, and analytic al performance predictions are compared with experimental results. Analysis of the power flow in the system shows that, although significant power tra nsfer occurs between the two electrical drives, the net power dissipation d uring pile driving is relatively low.