Electrohydraulic control system for a rockdrill assembly

Claim 1

In an electrohydraulic control system for a support arm assembly of a subterranean drilling machine for automatic drilling of a number of bores relatively shifted in a predetermined pattern forming a firing plan which comprises: a base support angularly displaceable about a substantially upright first axis; a first hydraulic operator connected to said base support for angularly displacing same about said first axis through an angle α1; an arm pivotally mounted on said base support and swingable thereon about a second axis substantially perpendicular to said first axis, said arm having a longitudinal third axis substantially perpendicular to said second axis; a second hydraulic operator connected to said arm for angularly displacing same about said second axis through an angle α2; a support member on said arm angularly displaceable about said third axis; a third hydraulic operator on said arm connected to said member for angularly displacing said member about said third axis through an angle α3; a tool-guiding rail pivotally mounted on said member for tilting movement about a fourth axis substantially perpendicular to said third axis; and a fourth hydraulic operator connected to said rail for tilting same about said fourth axis through an angle α4, the improvement wherein said system comprises in combination: first, second, third and fourth sensors responsive respective to angular displacements α1, α2, α3 and α4 for generating respective electrical signals representing these angular displacements; an electronic computer connected to each of said sensors individually for individually receiving said signals and processing same to provide: (a) third and fourth output signals from said computer determining said angular displacements α3 and α4 to be generated by said third and fourth operators to maintain said rail parallel to itself upon positioning of said rail at a number of different locations for tool operations in response to first and second output signals corresponding to said angular displacements α1 and α2, and (b) generating respective command signals Ve1, Ve2, Ve3 and Ve4 for each of said first, second, third and fourth operators upon said initiation of a programmed sequence of movements of said rail controlled by said computer for successive operations of a drilling tool on said rail in successive locations thereof; programming means for selecting from a number of such programmed sequences a predetermined sequence for applying a predetermined plan of locations for successive tool operations to said computer in accordance with said firing plan; respective electronic correction circuits between the respective outputs of said computer and each of said operators for controlling same by comparing signals representing said angular displacements α1, α2, α3 and α4 and thus said actual positions generated by said operators with command signals Ve1, Ve2, Ve3 and Ve4 from said computer, whereby each of said operators is controlled at least in part in consideration of forces on said assembly at each location, said third sensor producing electrical signals V3' and V3" which are respectively proportional to the sine and cosine of the angle of rotation α3 of said support member about about said third axis through a full 360°, said signals V3' and V3" being supplied to said electronic computer, said electronic computer being programmed to transform said signals V3' and V3" into a linear signal V3 as a function of the angle α3 over a full 360° excursion of said angle α3; and means for applying said signal V3 to the electronic correction circuit of said third operator as the angle representing the actual position α3 generated by said third operator.