The Effect of Large-Scale Structures on the Stability of Coal-Face Steering

Simplified models of piecewise rigid support structures for power-loaders operating on longwall coal-faces are shown to be amendable to analysis by z-transform methods. Such analysis predicts that increasing the length of the structures subsections sufficiently (compared to the inherent delay within the machine's vertical steering system) should stabilise the vertical steering of the entire coal face. Increasing the width of of the structure to embrace more than two consecutive cut floors is shown analytically to eliminate the need for electronic tilt-feedback in control systems. In general terms, these analytical predictions are shown to hold good in detailed simulations of the system that eliminate the simplifications demanded by the analytical method. The general conclusion of the work is therefore, that an increase in the size of support-structure segments can potentially reduce the complexity of steering control systems. The size-increase must be substantial, e.g. to 4 to 5 times the size of conventional structures.