An electric gripper system includes a motor driving a gripper mechanism, a sensor, and a controller. The sensor is assembled onto the motor for generating a current position of the gripper mechanism. The controller has a control segment, a transceiver segment, an accessible segment, and a driving segment. The control segment generates a target position according to a relative-position command value of the transceiver segment and an absolute cumulative position of the accessible segment. The control segment generates a driving datum based on a difference between the current position and the target position, and on a rotation rate of the motor. The driving segment uses the driving datum to drive the motor to move the gripper mechanism. With calculation among the relative-position command value, the absolute cumulative position, and the current position, the motor is prevented from accumulating positional deviation.

A machine controller for controlling a machine detects an absolute position of a detection target using a detector outputting rotation number data corresponding to a position of the detection target, and controls the machine based on the detected absolute position of the detection target. The machine controller includes: a storage unit which stores rotation number data, of the detector, that corresponds to a zero point position of the absolute position, as zero point position data, and which stores rotation number data exceeding a rotation number data length that the detector can output, as extended rotation number data; and a calculation unit which calculates the absolute position in accordance with Formula (1) below that is based on the rotation number data output from the detector, the zero point position data, and the extended rotation number data:
Absolute position=(Rotation number data from the detector+Extended rotation number data)−Zero point position data   (1).

A position detection device according to the present disclosure includes: a detector which outputs a count value corresponding to a position of a detection target, and repeating values from zero until an upper limit value; an extended data storage unit which stores extended data corresponding to an integrated value of change amount in the count value by the rollover; a position calculation unit which calculates an absolute position of the detection target by adding the count value outputted by the detector and the integrated value indicated by the extended data; a section storage unit which, among count sections defined by dividing the range of the count value into at least three, stores the count section in which the count value received from the detector is included; and a confirmation processing unit which confirmation appropriateness of the extended data, based on an isolation number between the count section stored by the section storage unit during position detection processing start, and the count section in which the count value is included after position detection processing start.

A position detection device according to the present disclosure includes: a detector which outputs a count value corresponding to a position of a detection target, and repeating values from zero until an upper limit value; an extended data storage unit which stores extended data corresponding to an integrated value of change amount in the count value by the rollover; a position calculation unit which calculates an absolute position of the detection target by adding the count value outputted by the detector and the integrated value indicated by the extended data; a section storage unit which, among count sections defined by dividing the range of the count value into at least three, stores the count section in which the count value received from the detector is included; and a confirmation processing unit which confirmation appropriateness of the extended data, based on an isolation number between the count section stored by the section storage unit during position detection processing start, and the count section in which the count value is included after position detection processing start.

A machine controller for controlling a machine detects an absolute position of a detection target using a detector outputting rotation number data corresponding to a position of the detection target, and controls the machine based on the detected absolute position of the detection target. The machine controller includes: a storage unit which stores rotation number data, of the detector, that corresponds to a zero point position of the absolute position, as zero point position data, and which stores rotation number data exceeding a rotation number data length that the detector can output, as extended rotation number data; and a calculation. unit which calculates the absolute position in accordance with Formula (1) below that is based on the rotation number data output from the detector, the zero point position. data, and the extended rotation number data:

Absolute position=(Rotation number data from the detector+Extended rotation number data)Zero point position data (1).

A numerical controller for controlling a machine receives an instruction to reestablish a machine coordinate value of a movable part of the machine and stops a servo motor driving the movable part. When the servo motor is stopped, the numerical controller acquires position information of a position detector provided to the servo motor. Then, the numerical controller updates the machine coordinate value of the movable part based on the position information, and further updates the absolute coordinate value of the movable part based on the updated machine coordinate value.