System and method for controlling a drilling machine

Abstract

A system and method for drilling a borehole using a drilling rig having a rotary drill bit includes monitoring one or more drilling parameters; determining whether the one or more monitored drilling parameters are within predetermined specifications for one or more of the monitored drill parameters; and, executing an exception control procedure for control of a drilling parameter. The exception control procedure receives an input sensor value associated with a drilling parameter and applies feedback control to establish a scaled error value that is used to compute a setting value for the drilling parameter. The drilling parameters controlled may include the rotation speed of the drill bit, the feed rate of the drill bit, the weight-on-bit, or rotation torque during retraction of the drill bit. A computer-readable database of specifications of drill bits may be provided as a part of the system.

I claim: 
     
         1 . A method for drilling a borehole using a drilling rig having at least one rotary drill bit, the drill bit having a feed force, and a computer-readable database of specifications of drill bits, the method comprising:
 executing a procedure to regulate the feed force on the drill bit, the procedure comprising:
 executing a feed-force limiting-line procedure; where the feed-force limiting-line procedure receives a first input sensor value representing a currently-measured feed rate, and predetermined parameters representing respectively, a reduction in feed force to be applied per increase in measured feed rate, and, a limiting value of feed force at zero feed rate;
 the feed-force limiting-line procedure calculating a first feed-force target value; and, 
 
 executing a control procedure to command adjustment of feed force on the drill bit; so that a third input sensor value representing measured feed force on the drill bit matches the first feed-force target value. 
   
     
     
         2 . The method of  claim 1 , further comprising:
 executing an exception control procedure; the exception control procedure receiving a second input sensor value representing currently-measured torque applied to the drill bit;
 the exception control procedure outputting a alternative second feed-force target value, and further outputting a signal when the alternative second feed-force target value is to be used; 
   selecting either the first feed-force target value or the alternative second feed-force target value depending on the signal output from the exception control procedure; and,   executing a control procedure to command adjustment of feed force on the drill bit; so that a third input sensor value representing measured feed force matches the selected feed-force target value.   
     
     
         3 . The method of  claim 1  where the control procedure to command adjustment of feed force comprises a PIV procedure. 
     
     
         4 . The method of  claim 1  where the control procedure to command adjustment of feed force comprises a PID procedure. 
     
     
         5 . The method of  claim 1 , where the calculation of the first feed-force target value comprises:
 obtaining the predetermined parameters for reduction in feed force to be applied per increase in measured feed rate, and for the limiting value of feed force at zero feed rate;   calculating the first feed-force target value by multiplying the feed force to be applied per increase in measured feed rate by the first input sensor value representing a currently-measured feed rate, and adding the limiting value of feed force at zero feed rate.   
     
     
         6 . The method of  claim 2 , where the limiting value of feed force at zero feed rate is reduced according to an operator-selected aggressiveness setting. 
     
     
         7 . The method of  claim 2 , where the limiting value of feed force at zero feed rate is reduced when a collaring drilling mode is selected.