Numerical controller and servomotor control system

A servomotor control system for controlling servomotors through servo amplifiers respectively connected thereto by a numerical controller, said system comprising:

• a plurality of serial buses to perform communications between the numerical controller and the servo amplifiers in daisy-chain;
• detecting means for detecting a communication failure in any of said plurality of serial buses and issuing an alarm indicating the communication failure;
• and
• selecting means for selecting stopping or continuing of the communications by each of the plurality of serial buses according to a parameter preset in the numerical controller when an alarm of the communication failure or a system failure of the numerical controller is inputted, so that the servo amplifiers connected to the plurality of serial buses are selectively operable.

A method of controlling servomotors through servo amplifiers respectively connected thereto by a numerical controller, comprising:

• detecting a communication failure in any of a plurality of serial buses;
• and
• selecting either notification or non-notification of the communication failure to communication control circuits, wherein
• communication control circuits communicating with servo amplifiers required to continue controlling the servomotors are not notified, and
• communication control circuits communicating with servo amplifiers not required to continue controlling the servomotors are notified.