Robot control system, lower-level control apparatus, and control method for robot

1. A robot control system comprising:

a robot having a servo control unit;

a lower-level control apparatus transmitting a control command to the servo control unit and receiving robot status information representing a status of the robot from the servo control unit with respect to a preset control period; and

an upper-level control apparatus transmitting command information for creation of the control command to the lower-level control apparatus, wherein

the lower-level control apparatus transmits the robot status information to the upper-level control apparatus in synchronization with the control period, and

the upper-level control apparatus transmits the command information to the lower-level control apparatus within a predetermined transmission time shorter than the control period from a time when receiving the robot status information from the lower-level control apparatus.

2. The robot control system according to claim 1 , wherein

the upper-level control apparatus selects and executes, according to description in a robot control program, as processing of creating the command information, one of

(i) first processing of creating the command information according to the robot control program created in advance without using the robot status information received from the lower-level control apparatus, and

(ii) second processing of creating the command information using the robot status information according to the robot control program.

3. The robot control system according to claim 1 , wherein

when failed to receive the command information from the upper-level control apparatus until a time-out time before a time to transmit the next control command to the servo control unit, the lower-level control apparatus creates the next control command using a previous control command without using the command information and transmits the command to the servo control unit.

4. The robot control system according to claim 3 , wherein

when failed to receive the command information from the upper-level control apparatus until the time-out time, the lower-level control apparatus creates the next control command by extrapolation of a plurality of control commands in the past.

5. A lower-level control apparatus forming a robot control system with a robot and an upper-level control apparatus, the lower-level control apparatus configured to execute:

(a) processing of transmitting a control command to a servo control unit of the robot and receiving robot status information representing a status of the robot from the servo control unit with respect to a preset control period;

(b) processing of transmitting the robot status information to the upper-level control apparatus in synchronization with the control period; and

(c) processing of receiving command information from the upper-level control apparatus and creating a next control command from the command information, wherein

in the processing (c),

when failed to receive the command information from the upper-level control apparatus until a time-out time before a time to transmit the next control command to the servo control unit, creating the next control command using a previous control command without using the command information and transmitting the command to the servo control unit.

6. A control method for a robot in a robot control system including the robot having a servo control unit, a lower-level control apparatus, and an upper-level control apparatus, comprising:

(a) transmitting a control command to the servo control unit and receiving robot status information representing a status of the robot from the servo control unit with respect to a preset control period by the lower-level control apparatus; and

(b) transmitting command information for creation of the control command to the lower-level control apparatus by the upper-level control apparatus, wherein

at (a), the lower-level control apparatus transmits the robot status information to the upper-level control apparatus in synchronization with the control period, and

at (b), the upper-level control apparatus transmits the command information to the lower-level control apparatus within a predetermined transmission time shorter than the control period from a time when receiving the robot status information from the lower-level control apparatus.