Method for position-calibration of a digging assembly for electric mining shovels
The present invention relates generally to the field of positioning mechanical equipment, and particularly to the likes of mechanical excavation and electric mining shovels. In one embodiment, there is disclosed a system for calibrating the sensors that measure hoist and crowd motions for an electric mining shovel, enabling the position of a bucket to be known with greater accuracy than can be achieved using previously known approaches.
1. A method of calibrating a work implement location, the work implement being attached to a machine house, the method comprising the steps of
(a) defining a h-frame comprising a set of Cartesian coordinate axes fixed to the machine house with the (X, Z) plane being in the sagittal plane of the machine house and the Y-axis being orthogonal;
(b) utilising a range measurement sensor at a point p h =(x h ,z h ) in the h-frame to create a directed line of measurement in the (X h ,Z h )-plane of the h-frame originating at p h along which a range measurement is made, designated by angle θ h ;
(c) defining a d-frame comprising a set of Cartesian coordinate axes fixed to the work implement;
(d) providing a range measurement sensor target at a point p d =(x d ,z d ) in the d-frame on the work implement;
(e) measuring a Cartesian distance d between p h and p d ; and
(f) measuring corresponding positions of motors used to drive the work implement.
2. A method as claimed in claim 1 wherein said work implement comprises a shovel handle and dipper assembly.
3. A method as claimed in claim 2 wherein the digging assembly is attached to a hoist and crowd motor and said method further comprises correlating the distance d with the measured position of the hoist motor, d hm and the crowd motor d cm for different distances d.
4. A method as claimed in claim 1 comprising the step of:
(g) maneuvering the work implement so that the range measurement sensor target intersects the line of measurement,
wherein step (g) occurs prior to step (e).
5. A method as claimed in claim 3 wherein the digging assembly includes a crowd actuator and a hoist actuator which are driven by the crowd motor and the hoist motor respectively, thereby to drive the work implement.
6. A method as claimed in claim 5 comprising the step of:
(h) computing calibration offsets, o c and o h , for the crowd and hoist actuators.
7. A method as claimed in claim 6 , wherein step (h) comprises the steps of:
(i) computing the extension of the crowd actuator d c and the saddle angle θ x , which together define the position and orientation of the d-frame relative to the h-frame; and
(j) thereafter computing the extension of the hoist actuator d h .
8. A method as claimed in claim 7 , wherein step (h) comprises the further step of:
(k) utilising the computed actuator extensions d c and d h , and the measured motor positions d hm and d cm to calculate the calibration offsets o c and o h .
9. A method as claimed in claim 8 , comprising the step of utilising an independent range measurement sensor directed along a line to resolve the crowd and hoist offsets o c and o h .
10. A system for allowing the calibration of a work implement location, the work implement being attached to a machine house, the system comprising:
(a) a component for defining an h-frame comprising a set of Cartesian coordinate axes fixed to the machine house with the (X, Z) plane being in the sagittal plane of the machine house and the Y-axis being orthogonal;
(b) a component for utilising a range measurement sensor at a point p h =(x h ,z h ) in the h-frame to create a directed line of measurement in the (X h ,Z h )-plane of the h-frame originating at p h along which a range measurement is made, designated by angle θ h ;
a component for defining a d-frame comprising a set of Cartesian coordinate axes fixed to the work implement;
(d) a component for providing a range measurement sensor target at point p d =(x d ,z d ) in the d-frame on the work implement;
(e) a component for measuring a Cartesian distance between p h and p d ; and
(f) a component for measuring corresponding positions of motors used to drive the work implement.