Methods, systems, and techniques for controlling the rate of penetration of a drill bit use drilling parameter measurements read from drilling parameter sensors to evaluate control loops, with the output of one of the control loops at any given time being used by an automatic driller to control the rate of penetration. For each of the drilling parameters, the automatic driller reads a drilling parameter measurement, determines an error measurement that represents a difference between a drilling parameter setpoint and the drilling parameter measurement, and from the error measurement determines an output signal proportional to the rate of penetration of the drill bit. The output signal of one of the control loops is subsequently selected and used to control the rate of penetration.