US 12,257,722 B2
Method for detecting and evaluating a friction status at a joint, robotic arm and computer program product
Karsten Monreal, Stadtbergen (DE)
Assigned to KUKA Deutschland GmbH, (DE)
Appl. No. 17/922,028
Filed by KUKA Deutschland GmbH, Augsburg (DE)
PCT Filed Apr. 23, 2021, PCT No. PCT/EP2021/060667
§ 371(c)(1), (2) Date Oct. 28, 2022,
PCT Pub. No. WO2021/219506, PCT Pub. Date Nov. 4, 2021.
Claims priority of application No. 10 2020 205 379.0 (DE), filed on Apr. 28, 2020.
Prior Publication US 2023/0173678 A1, Jun. 8, 2023
Int. Cl. B25J 9/00 (2006.01); B25J 9/16 (2006.01); B25J 13/08 (2006.01); B25J 17/00 (2006.01); B25J 19/00 (2006.01); G01L 5/28 (2006.01)
CPC B25J 9/1674 (2013.01) [B25J 13/085 (2013.01); B25J 17/00 (2013.01); B25J 19/0004 (2013.01); B25J 19/0095 (2013.01); G01L 5/28 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A method for detecting and evaluating a friction status in at least one joint of a robotic arm that includes a plurality of joints and a plurality of links connecting the joints to each other, wherein the robotic arm is connected to a robot controller that is designed and configured to control a plurality of electric motors and brakes of the robotic arm which are associated with the respective joints in order to move the robotic arm, the method comprising:
(a) automatically executing a brake test procedure associated with the robotic arm to control the electric motors and brakes via the robot controller, in order to automatically move the links of the robotic arm in accordance with a brake test program specified by the brake test procedure, and to automatically control the brakes;
(b) in accordance with the brake test program, automatically driving at least one motor of the plurality of electric motors in a first rotational direction and detecting a first motor torque in the at least one motor during rotation in the first rotational direction, and subsequently automatically driving the at least one motor in a second rotational direction, opposed to the first rotational direction, and detecting a second motor torque in the at least one motor during rotation in the second rotational direction;
automatically evaluating the first motor torque and the second motor torque in order to obtain a first moment of friction of the respective joint associated with the at least one driven motor;
repeating method steps (a) and (b) at a later point in time;
automatically evaluating the first motor torque and the second motor torque obtained at the later point in time in order to obtain a second moment of friction of the respective joint associated with the at least one driven motor;
comparing the second moment of friction to the first moment of friction; and
assessing the friction status of the joint associated with the at least one driven motor as defective in response to a deviation of the second moment of friction from the first moment of friction exceeding a prespecified threshold value.