Control System for Mining Machine

Abstract

A mining machine such as a mining shovel includes a digging assembly having an upward extending boom and a dipper assembly with a dipper that is generally horizontally supported by the boom. A hoist system including hoist ropes attached to the dipper may be used to vertically pivot the dipper assembly with respect to the boom. To determine if the hoist ropes are properly supporting the weight of the dipper assembly, an electronic controller can calculate a calculated hoist force based on a hoist speed associated with the hoist ropes and a hoist motor torque from a hoist motor. If the calculated hoist force indicates that slack exists in the hoist ropes, the electronic controller can execute a slack reduction function to increase tension in the hoist ropes attached to the dipper.

We claim: 
     
         1 . A mining machine comprising:
 an undercarriage;   an upper structure supported on the undercarriage;
 a digging assembly disposed on the upper structure, the digging assembly including: 
 a boom connected to the upper structure at a lower end and extending upwardly to an upper end; 
 a dipper assembly including a dipper arm and a dipper disposed at a first end of the dipper arm, the dipper assembly pivotally supported by the boom; 
 a hoist system for pivoting the dipper assembly with respect to the boom in a generally vertical direction, the hoist system including:
 a hoist motor disposed on the upper structure; 
 a hoist rope operatively associated with the hoist motor and running from a hoist winch upwards about the upper end of the boom and downwards to attach to the dipper; 
 
   an electronic controller operatively associated with the hoist system and in electronic communication with hoist motor, the electronic controller configured to receive a hoist speed and an hoist motor torque and to determine a calculated hoist rope force indicative of tension in the hoist rope based in part on the hoist speed and the hoist motor torque.   
     
     
         2 . The mining machine of  claim 1 , wherein the electronic controller receives an inertia parameter associated with the dipper assembly and calculates the calculated hoist rope force based in part on the inertia parameter. 
     
     
         3 . The mining machine of  claim 2 , wherein the electronic controller converts the hoist speed to a hoist acceleration. 
     
     
         4 . The mining machine of  claim 3 , wherein the electronic controller calculates an inertial hoist force based on the inertia parameter and the hoist acceleration. 
     
     
         5 . The mining machine of  claim 4 , wherein the electronic controller calculates the calculated hoist rope force by subtracting the inertial hoist force from the hoist motor torque. 
     
     
         6 . The mining machine of  claim 5 , wherein the electronic controller compares the calculated hoist rope force to a hoist force threshold to assess a rope slack condition. 
     
     
         7 . The mining machine of  claim 6 , wherein the electronic controller reduces the hoist speed if the rope slack condition is assessed. 
     
     
         8 . The mining machine of  claim 7 , further comprising a crowd system for slidably moving the dipper assembly with respect to the boom, the crowd system including a crowd motor disposed in the upper structure and a crowd actuator operatively associated with the crowd motor and arranged to slide the dipper arm with respect to the boom. 
     
     
         9 . The mining machine of  claim 8 , wherein the electronic controller reduces a crowd speed of the crowd actuator if electronic controller assesses the rope slack condition. 
     
     
         10 . The mining machine of  claim 1 , wherein the upper structure is rotatably mounted to the undercarriage; and the electronic controller monitors a swing command directing the upper structure to rotatably swing with respect to the undercarriage. 
     
     
         11 . The mining machine of  claim 10 , wherein the electronic controller compares the swing command to a swing threshold and only assesses a rope slack condition if the swing command is below the swing threshold. 
     
     
         12 . The mining machine of  claim 1 , further comprising an operator input device for interfacing with an operator. 
     
     
         13 . The mining machine of  claim 12 , wherein the electronic controller receives a hoist speed command from the operator input device and limits the hoist speed command with a hoist speed limit to reduce the hoist speed. 
     
     
         14 . A method of operating a mining machine comprising:
 operating a hoist motor to pay out or wind in a hoist rope;   pivoting a dipper assembly pivotally supported on a boom arranged in an upward orientation on the mining machine with the hoist rope by operation of the hoist motor;   receiving a hoist motor torque and a hoist speed;   calculating a calculated hoist rope force based in part on the hoist motor torque and the hoist speed, the calculated hoist rope force representative of tension in the hoist rope; comparing the calculated hoist rope force to a hoist force threshold; and   reducing the hoist speed if the calculated hoist rope force is below the hoist force threshold.   
     
     
         15 . The method of  claim 14 , wherein the step of calculating the calculated hoist rope force comprises:
 converting the hoist speed to a hoist acceleration;   multiplying the hoist acceleration with an inertia parameter associated with the dipper assembly to determine a inertial hoist force; and   subtracting the inertial hoist force from the hoist motor torque to determine the calculated hoist rope force.   
     
     
         16 . The method of  claim 14 , further comprising reducing a crowd speed operatively associated with a crowd actuator arranged to slidably crowd and retract the dipper assembly supported on the boom. 
     
     
         17 . The method of  claim 14 , further comprising:
 monitoring a swing command directing rotation of an upper structure with respect to an undercarriage; and   comparing the swing command to a swing threshold as a prerequisite to reducing the hoist speed.   
     
     
         18 . The method of  claim 14 , wherein the step of reducing the hoist speed further comprises receiving a hoist speed command from an operator input device and limiting the hoist speed command with a hoist speed limit. 
     
     
         19 . An electronic controller for a mining machine having a dipper assembly pivotally supported on a boom extending upwardly with respect to the mining machine, the electronic controller comprising:
 a hoist force function configured to determine a calculated hoist rope force based in part on a hoist motor torque generated by a hoist motor operatively arranged to pay out and wind a hoist rope attached to the dipper assembly to pivot the dipper assembly with respect to the boom, a hoist speed associated with the hoist rope, and an inertia parameter associated with the dipper assembly;   the hoist force function further configured to determine a rope slack condition indicative of slack in the hoist rope by comparing the calculated hoist rope force with a hoist force threshold; and   a slack reduction function configured to reduce the hoist speed during the rope slack condition.   
     
     
         20 . The electronic controller of  claim 19 , wherein the hoist force function is further configured to convert the hoist speed to a hoist acceleration, multiply the hoist acceleration with an inertia parameter associated with the dipper assembly to produce a hoist inertia force, and to subtract the hoist inertia force from the hoist motor torque to determine the calculated hoist rope force.