Patent ID: 7460471

Claim:
A method of maintaining operation in the event of a fault of a system for motion control with a plurality of slaves in a ring network controlled by a central controller, comprising: transmitting first messages addressed to plural respective slaves in a first direction along said ring network; monitoring first reply messages transmitted by said plural slaves in a second direction along said ring network in response to the transmitted first messages; identifying, when first reply messages are not received from each slave to which a first message was transmitted, a first subset of slaves from which said first reply messages are received, and based thereon, determining a second subset of slaves exclusive of said first subset of slaves, from which respective first reply messages were not received; transmitting in said second direction, when first reply messages are not received from each slave to which a first message was transmitted, second messages addressed to respective slaves in said second subset of slaves; receiving second reply messages transmitted by respective of said slaves of said second subset of slaves in response to said second messages, said second reply messages traveling in said first direction along said ring network; transmitting in said first direction third messages addressed to said first subset of slaves; and transmitting in said second direction fourth messages addressed to said second subset of slaves.