A pre-process simulation may calculate operating conditions of a machine tool by simulating a NC program and calculate predicted values indicative of the operating conditions. A real time monitoring system may compare actual values from the actual operation of a machine tool actually executing the NC program to the predicted values and determine whether to initiate a response. The operating conditions may be machine tool operating conditions. The comparison of actual values to predicted values may be based on a dynamic limit within which the predicted values fall which may vary based on the tool position, and the dynamic limit may include upper and lower limit boundaries.

An abnormality detection method for detecting an abnormality of an encoder provided for a robot includes: obtaining corrected position information according to commanded position information output from a controller that designates the rotational position of a motor and an output signal output from the encoder; and, determining, after comparing the corrected position information with the detected position information according to the output signal output from the encoder, the abnormality of the encoder, if there is a difference greater than or equal to a predetermined value between the corrected position information and the detected position information. The controller removes a vibration component of the robot corresponding to the weight of an attachment load from the commanded position information and compensates for a time delay to obtain the corrected position information.

A robot including a motor is used to machine a workpiece. The robot further includes the following components: a controller configured to output a speed command and commanded-position information; an encoder; a position sensor configured to output, as a differential signal, the amount of displacement of the position of the workpiece W from a predetermined position; a servo driver configured to control the motor upon receiving the speed command, the output signal of the encoder, and the differential signal; and a safety unit configured to detect a fault in the encoder. When controlling the motor based on the speed command, the output signal, and the differential signal, the servo driver sends the differential signal to the controller. The controller sends the safety unit new commanded-position information, which is generated by adding a correction value based on the differential signal to the commanded-position information.

A method for operating a multiple axis machine includes controlling drives of the machine with a machine control system and monitoring the machine with a fail-safe control system having first and second redundant channels. Each of the first and second channels receives first input target values and first input actual values from the machine control system, and compares first reference target values (based on the first input target values) with first reference actual values (based on the first input actual values). A fault reaction is triggered if there is a deviation between the compared values that exceeds a specified tolerance. The first input values comprise reference position values of a machine-fixed reference or time derivatives thereof, and the machine control system determines target and/or actual reference position values based on a transformation between reference position values of the machine-fixed reference and axial position values of the machine.

An abnormality detection method for detecting an abnormality of an encoder provided for a robot includes: obtaining corrected position information according to commanded position information output from a controller that designates the rotational position of a motor and an output signal output from the encoder; and, determining, after comparing the corrected position information with the detected position information according to the output signal output from the encoder, the abnormality of the encoder, if there is a difference greater than or equal to a predetermined value between the corrected position information and the detected position information. The controller removes a vibration component of the robot corresponding to the weight of an attachment load from the commanded position information and compensates for a time delay to obtain the corrected position information.

A robot including a motor is used to machine a workpiece. The robot further includes the following components: a controller configured to output a speed command and commanded-position information; an encoder; a position sensor configured to output, as a differential signal, the amount of displacement of the position of the workpiece W from a predetermined position; a servo driver configured to control the motor upon receiving the speed command, the output signal of the encoder, and the differential signal; and a safety unit configured to detect a fault in the encoder. When controlling the motor based on the speed command, the output signal, and the differential signal, the servo driver sends the differential signal to the controller. The controller sends the safety unit new commanded-position information, which is generated by adding a correction value based on the differential signal to the commanded-position information.

A pre-process simulation may calculate operating conditions of a machine tool by simulating a NC program and calculate predicted values indicative of the operating conditions. A real time monitoring system may compare actual values from the actual operation of a machine tool actually executing the NC program to the predicted values and determine whether to initiate a response. The operating conditions may be machine tool operating conditions. The comparison of actual values to predicted values may be based on a dynamic limit within which the predicted values fall which may vary based on the tool position, and the dynamic limit may include upper and lower limit boundaries.

An average value of differences between command current values acquired at a plurality of timings when the motor is controlled at a rotation speed within a preset fixed range in a preset period and an average value of the command current values in the period is acquired, and the average value of the differences is accumulated in an order of the acquisition. When a difference between an accumulated value of the average values of the differences up to an N1th time and an accumulated value of the average values of the differences up to an Nth time becomes greater than or equal to a preset value, and then become less than the preset value, and then again becomes greater than or equal to the preset value, a notification of an abnormality sign in the robot arm is transmitted.

A pre-process simulation may calculate operating conditions of a machine tool by simulating a NC program and calculate predicted values indicative of the operating conditions. A real time monitoring system may compare actual values from the actual operation of a machine tool actually executing the NC program to the predicted values and determine whether to initiate a response. The operating conditions may be machine tool operating conditions. The comparison of actual values to predicted values may be based on a dynamic limit within which the predicted values fall which may vary based on the tool position, and the dynamic limit may include upper and lower limit boundaries.

An average value of differences between command current values acquired at a plurality of timings when the motor is controlled at a rotation speed within a preset fixed range in a preset period and an average value of the command current values in the period is acquired, and the average value of the differences is accumulated in an order of the acquisition. When a difference between an accumulated value of the average values of the differences up to an N1th time and an accumulated value of the average values of the differences up to an Nth time becomes greater than or equal to a preset value, and then become less than the preset value, and then again becomes greater than or equal to the preset value, a notification of an abnormality sign in the robot arm is transmitted.