US 12,440,933 B2
Screw tightening system, controller, and non-transitory storage medium
Shu Biwaki, Kyoto (JP); Zhiqiang Liu, Kyoto (JP); Masahiro Murai, Kyoto (JP); and Yuki Tsuchihashi, Kyoto (JP)
Assigned to OMRON CORPORATION, Kyoto (JP)
Filed by OMRON Corporation, Kyoto (JP)
Filed on Feb. 2, 2023, as Appl. No. 18/163,395.
Claims priority of application No. 2022-029619 (JP), filed on Feb. 28, 2022.
Prior Publication US 2023/0271282 A1, Aug. 31, 2023
Int. Cl. B23P 19/06 (2006.01)
CPC B23P 19/066 (2013.01) 11 Claims
OG exemplary drawing
 
1. A screw tightening system comprising:
an actuator including a driver bit configured to rotationally drive a screw, a motor coupled with the driver bit, a driver configured to drive the motor, and a load sensor configured to detect an axial load on the driver bit; and
a controller configured to control the actuator,
wherein:
the driver is configured to calculate a torque value of a torque generated in the motor,
the controller includes:
an acquirer configured to acquire torque values of the torque from the driver,
a calculator configured to calculate a standard deviation of the torque values acquired in a temporary tightening period from when the screw engages with a screw hole until when the screw is seated in the screw hole, and
a determiner configured to determine that there is an abnormality when a ratio of the standard deviation to a reference standard deviation exceeds a first threshold value, and
the determiner is configured to determine that there is an abnormality when the ratio does not exceed the first threshold value and the axial load detected by the load sensor exceeds a second threshold value.