Control system for longwall shearer

Claim 1

A control system for a longwall coal shearer assembly, said shear assembly comprising a track positionable in a tunnel along a seam of coal having a generally sine wave contour and a shearing machine adapted to move along said track, said shearing machine including a body having a longitudinal reference, a shearing drum, and an arm pivotally supported at one end on an end region of said body, with an opposite end of said arm extending beyond said body, a driven shearing drum rotably attached to said opposite end of said arm, and means responsive to control signals for rotating said arm whereby said drum is varied in elevation, said system comprising: first inclination means supported by said body for providing first electrical signals representative of the inclination of said longitudinal reference of said shearer with respect to a horizontal line perpendicular to gravity; second inclination means for providing second electrical signals representative of the inclination of said arm with respect to said longitudinal reference; sensing means responsive to the movement of said body along said track for providing third electrical signals representative of the movement of said shearer along said track; first computational means responsive to first and third signals for providing, as fourth signals, signals representative of changes of said first signals in relation to changes of said third signals; second computational means responsive to the sum of a first constant times said first signals and a second constant times said fourth signals for providing fifth signals representative of the difference in the elevation of said shearing drum from a sine wave elevational contour formed by said track and when maintained at a fixed elevation as said shearer traverses said track; and control means responsive to said fifth signals and said second signals for providing said control signals to said means for rotating said arm and controlling the elevation of said drum.