Abstract: Torsional oscillation of a shaft in a swing drive system of an excavator is minimized by monitoring torsional strain of the shaft. An electric motor provides torque to the shaft in response to a drive signal provided by a converter. A compensation circuit produces a compensation signal as a function of torsional strain of the shaft. A field excitation circuit or regulator powers a converter as a function of the compensation signal such that a counter torque is provided to the shaft and torsional oscillation of the shaft is reduced.

Abstract: Torsional oscillation of a shaft in a swing drive system of an excavator is minimized by monitoring torsional strain of the shaft. An electric motor provides torque to the shaft in response to a drive signal provided by a converter. A compensation circuit produces a compensation signal as a function of torsional strain of the shaft. A field excitation circuit or regulator powers a converter as a function of the compensation signal such that a counter torque is provided to the shaft and torsional oscillation of the shaft is reduced.

Abstract: Torsional oscillation of a shaft in a swing drive system of an excavator is minimized by monitoring torsional strain of the shaft. An electric motor provides torque to the shaft in response to a drive signal provided by a converter. A compensation circuit produces a compensation signal as a function of torsional strain of the shaft. A field excitation circuit or regulator powers a converter as a function of the compensation signal such that a counter torque is provided to the shaft and torsional oscillation of the shaft is reduced.

Abstract: A method of underground mining includes mining material using a continuous miner to form at least one set of entries comprising a plurality of entries. A plurality of crosscuts extend between and connect the entries. A plurality of pillars are defined by the entries and crosscuts. The entries and crosscuts define a passage having a roof, a floor, and sidewalls. The pillars at least in part are adapted to prevent the roof of the passage from collapsing. Roof bolts are installed in the roof of the passage. Material is mined from the sidewalls of the passage with the continuous miner to form perimeter cuts extending outwardly from the passage. The perimeter cuts are free of roof bolts. At least approximately 30 percent of the material mined from within the set of entries is derived from the unbolted perimeter cuts.