This angular transmission error identifying system identifies an angular transmission error of a speed reducer (13) of a robot arm (4) including a joint (7) which is driven in rotation by a motor (11) via the speed reducer (13). The angular transmission error identifying system is provided with an identifying unit (46) which calculates an amplitude parameter and a phase parameter of an angular transmission error identifying function, which is a periodic function modeling the angular transmission error of the speed reducer (13), and which includes the amplitude parameter and the phase parameter, and uses the angular transmission error identifying function to identify the angular transmission error. The identifying unit (46) calculates the amplitude parameter corresponding to a gravitational torque current value, which is a gravitational torque value acting on the joint at the time the angular transmission error is being identified, using an amplitude first function or an amplitude second function in accordance with the value of the gravitational torque current value, and calculates the phase parameter corresponding to the gravitational torque current value using a phase first function or a phase second function in accordance with the gravitational torque current value.
ANGULAR TRANSMISSION ERROR IDENTIFYING SYSTEM, ANGULAR TRANSMISSION ERROR IDENTIFYING METHOD, AND ROBOT SYSTEM