Synchronous control unit for synchronizing two shafts with each other

A synchronous control unit, comprising:

• a first motor and a first amplifier for driving the first motor;
• a second motor and a second amplifier for driving the second motor;
• a NC unit connected to the first and the second amplifier;
• a first communication path connecting the first amplifier to the NC unit;
• a second communication path connecting the second amplifier to the NC unit;
• a third communication path connecting the first amplifier to the second amplifier;
• a movement command making section arranged in the NC unit, making a movement command of at least one of the first and the second motor;
• a first communication monitoring section for monitoring communication in the first communication path;
• a second communication monitoring section for monitoring communication in the second communication path;
• a deceleration command making section included in the first amplifier, making a deceleration command of the first motor;
• and
• a switching section for switching the system from a first synchronous system to a second synchronous system in the case where the first communication monitoring section detects communication trouble in the first communication path or in the case where the second communication monitoring section detects communication trouble in the second communication path, wherein
• in the first synchronous system, movement commands of the first and the second motor, which are synchronized with each other, made by the movement command making section are respectively supplied to the first and the second amplifier through the first and the second communication path,
• in the second synchronous system, the first motor is decelerated by a deceleration command made by the deceleration command making section and the second motor is decelerated synchronously with the first motor by a movement command made according to a position feedback value controlled by the first motor supplied to the second amplifier through the third communication path.