US Patent No. 9,193,074

MULTI-JOINT ROBOT HAVING GAS SPRING, AND METHOD FOR ESTIMATING INNER PRESSURE OF THE GAS SPRING


Patent No. 9,193,074
Issue Date November 24, 2015
Title Multi-joint Robot Having Gas Spring, And Method For Estimating Inner Pressure Of The Gas Spring
Inventorship Yu Hayashi, Yamanashi (JP)
Assignee Fanuc Corporation, Yamanashi (JP)

Claim of US Patent No. 9,193,074

1. A multi-joint robot comprising:
a robot mechanical unit having at least one arm;
a gas spring arranged on the arm; and
a controller which controls the robot mechanical unit,
wherein the gas spring comprises a cylinder, compressible inert gas enclosed within the cylinder and a piston rod configured
to slide in the cylinder, the gas spring being configured as a gas balancer for reducing a load of a servomotor which drives
the arm, and

wherein the controller has a function to obtain a reference current value of a servomotor for driving the arm at a reference
point in time when the servomotor is energized and controlled; obtain an object current value of the servomotor at a point
in time, which is different from the reference point in time, when the servomotor is energized and controlled under the same
operating condition as the reference point in time; calculate a difference between the reference current value and the object
current value; and calculate an amount of decrease in inner pressure of the compressible inert gas of the gas spring, based
on the difference.