Abstract: Method, apparatus and systems for drilling wells, such as for production of petroleum products and ensuring efficient well drilling and protection of well drilling systems during drilling operations. A closed-loop drilling control system, including a digital switching control regulator (SCR) module is provided for automated actuation of selected drilling rig controls responsive to downhole and surface measurements of drilling parameters. The closed-loop drilling control system is responsive to digital data from a measuring-while-drilling (MWD) tool for refining the drilling controls by automated correction of driller inputs to the drilling controls of the well drilling system during drilling operations. The downhole data, such as surface weight on bit, downhole weight on bit, pressure and flow rate of downhole drilling fluid hydraulics, etc.