The present disclosure is directed to systems and methods for rotating a drill string to mitigate stick-slip oscillations. An embodiment includes a method of rotating a drill string driven by a drive system using a control system. The method includes measuring torque values of the drive system with a torque sensor. The method also includes determining a frequency of stick-slip oscillations at the drive system based on the torque values using the control system. The method also includes determining an estimated instantaneous rotational speed of the drive system with the control system based on at least the frequency of stick-slip oscillations and a characteristic impedance of the drill string. The method also includes adjusting the estimated instantaneous rotational speed based on changes in the torque values to define an adjusted estimated instantaneous rotation speed with the control system. The method also includes providing an output signal representing the adjusted estimated instantaneous rotational speed to the drive system. The method also includes controlling rotation of a quill of the drive system based on the output signal.

An axisymmetric clutch mechanism includes a drive clutch body having a drive bearing surface and a drive clutch surface; an intermediate clutch body having an intermediate clutch surface configured for sliding contacting engagement with the drive clutch surface; a driven clutch body having a driven bearing surface configured for transferring compressive axial force to the drive bearing surface; and rotational drag means for generating resistance to rotational slippage between the drive clutch surface and the intermediate clutch surface. The intermediate and driven clutch bodies are helically coupled in a first rotational direction, forming a first helical coupling having a first lead angle, and with the taper angle of the drive clutch surface and the intermediate clutch surfaces and the first lead angle being selected such that the clutch mechanism will lock when the drive clutch body is rotated relative to the driven clutch body in the first rotational direction.

An axisymmetric clutch mechanism includes a drive clutch body having a drive bearing surface and a drive clutch surface; an intermediate clutch body having an intermediate clutch surface configured for sliding contacting engagement with the drive clutch surface; a driven clutch body having a driven bearing surface configured for transferring compressive axial force to the drive bearing surface; and rotational drag means for generating resistance to rotational slippage between the drive clutch surface and the intermediate clutch surface. The intermediate and driven clutch bodies are helically coupled in a first rotational direction, forming a first helical coupling having a first lead angle, and with the taper angle of the drive clutch surface and the intermediate clutch surfaces and the first lead angle being selected such that the clutch mechanism will lock when the drive clutch body is rotated relative to the driven clutch body in the first rotational direction.

An axisymmetric clutch mechanism includes a drive clutch body having a drive bearing surface and a drive clutch surface; an intermediate clutch body having an intermediate clutch surface configured for sliding contacting engagement with the drive clutch surface; a driven clutch body having a driven bearing surface configured for transferring compressive axial force to the drive bearing surface; and rotational drag means for generating resistance to rotational slippage between the drive clutch surface and the intermediate clutch surface. The intermediate and driven clutch bodies are helically coupled in a first rotational direction, forming a first helical coupling having a first lead angle, and with the taper angle of the drive clutch surface and the intermediate clutch surfaces and the first lead angle being selected such that the clutch mechanism will lock when the drive clutch body is rotated relative to the driven clutch body in the first rotational direction.

An axisymmetric clutch mechanism includes a drive clutch body having a drive bearing surface and a drive clutch surface; an intermediate clutch body having an intermediate clutch surface configured for sliding contacting engagement with the drive clutch surface; a driven clutch body having a driven bearing surface configured for transferring compressive axial force to the drive bearing surface; and rotational drag means for generating resistance to rotational slippage between the drive clutch surface and the intermediate clutch surface. The intermediate and driven clutch bodies are helically coupled in a first rotational direction, forming a first helical coupling having a first lead angle, and with the taper angle of the drive clutch surface and the intermediate clutch surfaces and the first lead angle being selected such that the clutch mechanism will lock when the drive clutch body is rotated relative to the driven clutch body in the first rotational direction.

The present disclosure is directed to systems and methods for rotating a drill string to mitigate stick-slip oscillations. An embodiment includes a method of rotating a drill string driven by a drive system using a control system. The method includes measuring torque values of the drive system with a torque sensor. The method also includes determining a frequency of stick-slip oscillations at the drive system based on the torque values using the control system. The method also includes determining an estimated instantaneous rotational speed of the drive system with the control system based on at least the frequency of stick-slip oscillations and a characteristic impedance of the drill string. The method also includes adjusting the estimated instantaneous rotational speed based on changes in the torque values to define an adjusted estimated instantaneous rotation speed with the control system. The method also includes providing an output signal representing the adjusted estimated instantaneous rotational speed to the drive system. The method also includes controlling rotation of a quill of the drive system based on the output signal.

The present disclosure is directed to systems and methods for rotating a drill string to mitigate stick-slip oscillations. An embodiment includes a method of rotating a drill string driven by a drive system using a control system. The method includes measuring torque values of the drive system with a torque sensor. The method also includes determining a frequency of stick-slip oscillations at the drive system based on the torque values using the control system. The method also includes determining an estimated instantaneous rotational speed of the drive system with the control system based on at least the frequency of stick-slip oscillations and a characteristic impedance of the drill string. The method also includes adjusting the estimated instantaneous rotational speed based on changes in the torque values to define an adjusted estimated instantaneous rotation speed with the control system. The method also includes providing an output signal representing the adjusted estimated instantaneous rotational speed to the drive system. The method also includes controlling rotation of a quill of the drive system based on the output signal.

Disclosed is a torque limiter having driver mandrel and driven axially aligned mandrels, a piston movable into and out of an engaged position wherein the driver and driven mandrels are coupled together to transmit torque there between. Hydraulically locking the movable piston in an engaged position. Disengaging the hydraulic lock when during rotation when a specified torque magnitude is exceeded to allow relative rotation between the mandrels. Resetting the torque limiter by hydraulically locking the piston in the engaging position when relative rotation ceases or is reduced.

An apparatus for drilling a hole in a golf green. The apparatus includes a support frame, a moveable cutter head, a handle, a base, a tread plate, an ejection mechanism, a drive motor configured to power the operation of the apparatus and control device. A drive shaft connects the drive motor with the cutter head via a threaded coupling. The cutter head is advanced relative to the tread plate when the drive shaft is rotated in one rotational direction and is retracted relative to the tread plate when the drive shaft is rotated in the opposite rotational direction. The drive shaft is provided with a central threaded portion and a non-threaded end portion at each end of the thread. The non-threaded end portions act as slip couplings configured to allow a rotation of the drive shaft without axial movement of the threaded coupling to stop the cutter head.