| 摘要 |
A down-hole drilling assembly ( 12,16 ) and control system ( 120 ) therefor, for directional drilling including a bent housing of a bottom hole assembly ( 18 ), utilising a gearbox ( 102 ) to derive a higher speed (about 600 r.p.m.) rotational drive ( 104 ) from the drill string ( 10 ) to drive a drilling bit ( 20 ) via an electromagnetic clutch ( 110, 112 ) controlled by the control system ( 120 ) such that the clutch balances reaction torque when the orientation angle of the bent housing is correct.
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