US Patent 10895142 Controlling drill string rotation

Methods and apparatus for controlling drill string rotation. The apparatus may be a control system for controlling a driver operable to rotate a drill string to form a wellbore extending into a subterranean formation. The control system may include a first controller operable to control rotation of the driver and a second controller communicatively connected with the first controller. During the drilling operations the first and/or second controller may be operable to generate a rotational speed command based on status information indicative of operational status of the drill string, and thereby cause the driver to rotate the drill string based on the rotational speed command.