Abstract: An improved controller for vibratory seismic energy sources insures that the energy imparted to the ground by the source is in phase with the reference signal. Phase lock is achieved in a manner which minimizes the effects of the attendant frequency distortion. On upsweeps when the phase error is greater than some threshold level, phase lock is achieved by slowing down the drive signal, thereby introducing frequency distortion which falls below the bandpass of the sweep signal. On downsweeps when the phase error is above some selected threshold, phase lock is achieved by speeding up the drive signal, thereby resulting in frequency distortion which falls above the bandpass of the sweep signal.

Abstract: There has been provided an improved process control optimizer for regulating at least one parameter of the process relative to optimum utilization of available energy. Temperature responsive open loop control means regulates the fuel flow and the optimizer is operatively responsive to the fuel flow for regulating air flow for combustion of fuels such that the fuel air mixture is minimized. The improvement includes a means for delivering a digital output code for governing the air mixture in accordance with the optimum characteristic of the process and digitally responsive means receive said codes for decreasing air at a selected first rate and increasing air at a relatively faster second rate, the rates corresponding to respective reductions and increases in fuel flow about a selected optimum operating point.