Motor driver and servo drive system

1 . A motor driver configured to supply electrical power to a motor on a basis of a control command sent periodically at a rate according to a network communication period of the communication network and sent from a higher-level controller connected to the motor driver via the communication network, the motor driver comprising:

a network frame receiver configured to receive the control command via the communication network at the periodical rate;

a user program processor configured to perform program processing of a user program created by a user;

a servo controller configured to output a servo control command, the servo control command being based on the control command; and

a drive controller configured to supply electrical power to the motor, the electrical power being based on the servo control command, wherein

when the user program processor performs the program processing:

the user program processor is configured to start the user program according to each of activation signals generated at respective receptions of the control command to cause the user program to perform the program processing on the control command to convert the control command into a command corresponding to the user program, in synchronization with the network communication period of the control command when the network frame receiver receives the control command; and

the servo controller is configured to output the servo control command, the servo control command being based on the control command resulting from the program processing.

2 . The motor driver according to claim 1 , wherein

the control command includes a sequential position command, a sequential speed command, or a sequential torque command, directed to the motor.

3 . The motor driver according to claim 1 , wherein

when the program processing started on a basis of one of the activation signals has not been completed within a predetermined time, the user program processor determines that an unusual condition has occurred, and aborts the program processing associated with the one of the activation signals.

4 . The motor driver according to claim 1 , wherein

when the program processing started on a basis of a second activation signal of the activation signals has not been completed at a time when the user program processor receives a first activation signal of the activation signals, the user program processor determines that an unusual condition has occurred, and aborts performing the program processing started on a basis of the first activation signal, the second activation signal being an activation signal immediately previous to the first activation signal.

5 . The motor driver according to claim 1 , wherein

the network frame receiver is configured to receive the control command in every network communication period.

6 . The motor driver according to claim 1 , wherein

the user program processor is configured to perform the user program with a period the same as the network communication period.

7 . The motor driver according to claim 1 , wherein

the user program processor is configured to perform the user program with a period that is a constant-value times the network communication period.

8 . The motor driver according to claim 1 , wherein

the user program processor is further configured to determine whether the user program has completed processing at a time synchronized with the network communication period.

9 . The motor driver according to claim 1 , wherein

the user program is executed during the network communication period.

10 . A servo drive system comprising:

the motor driver according to claim 1 ; and

the higher-level controller.

11 . A servo drive system comprising:

the motor driver according to claim 2 ; and

the higher-level controller.

12 . A servo drive system comprising:

the motor driver according to claim 4 ; and

the higher-level controller.

13 . A servo drive system comprising:

the motor driver according to claim 3 ; and

the higher-level controller.