Patent ID: 7404454

Claim:
A system for selectively orienting a bit at the end of a drillstring, the system comprising motive apparatus for rotating a drillstring and a bit, the bit connected to an end of the drillstring, the drillstring in a wellbore, the wellbore extending from an earth surface into the earth, the bit at a location beneath the earth surface, a control member apparatus including a control member manually movable by a person to effect a change in orientation of the bit in the wellbore, the control member apparatus including signal apparatus for producing a movement signal indicative of manual movement of the control member, a control system in communication with the motive apparatus and the control member, the control system for translating a movement signal from the control member apparatus into a command to the motive apparatus, the command commanding the motive apparatus to rotate the drillstring and the bit in correspondence to the movement of the control member, the control system including computing apparatus programmed for receiving a speed limit input and a torque limit input by an operator person, the speed limit input comprising a signal indicative of a limit on speed of movement of the drillstring, the torque limit input comprising a signal indicative of a limit on torque applied to the drillstring, the control system controlling movement by the motive apparatus so that the speed limit is not exceeded and so that the torque limit is not exceeded, wherein the motive apparatus comprises a top drive system, the top drive system includes a top drive and driving of the top drive is done by a variable frequency drive, a variable frequency drive controller controls the variable frequency drive, the control system controls the variable frequency drive controller, the variable frequency drive controller provides feedback to the control system indicative of actual speed of a drive shaft of the top drive, the drive shaft connected to the drillstring to rotate the drillstring and the bit, and feedback indicative of the actual torque applied to the drillstring by the top drive shaft, the bit is to be moved to a destination position from a starting position, wherein the control system controls the motive apparatus so that overshooting of the destination position by the bit is eliminated or minimized, and wherein the control system calculates a constant acceleration for initial movement by the motive apparatus of the drillstring and bit, a constant velocity for movement by the motive apparatus of the drillstring and bit following movement at a constant acceleration, and a constant deceleration for movement by the motive apparatus of the drillstring and bit to move the bit to a destination position with no or minimal overshooting of the destination position.