US 10,449,676 B2 · Multi-jointed robot deviation under load determination

Abstract

Determining deviation of a multi jointed robot under load using a tribological contact between an end of the robot and any available hard constraint near the robot, involves pressing the end against the constraint, and then soliciting a movement of the end relative to the constraint in a tribologically resisted direction to apply a force that does not overbear the resistance. By measuring the force and a position encoded by the robot, a deviation of the robot under the corresponding load is determined. Correction terms may be required for deformation of the tribological surface and/or constraint. The constraint may be tooling or parts subjected to an intended process. The deviation at many measurement poses of the robot, each in multiple resisted directions, within the ordinary operating space of the robot, was used to derive compliances of the robot, and a kinetostatic model.

Claims22

Dependent claims

A method for determining a deviation of a multi-jointed robot subjected to a load, the method comprising:

moving an end of the robot to a measurement pose adjacent a constraint;
applying a first force to press the robot end into tribological contact with the constraint;
soliciting the robot to move the end in one direction that is resisted by the tribological contact while the tribological contact is maintained, where the solicitation exerts a second force that is insufficient to overbear the tribological contact's resistance;
and
quantifying the second force in the resisted direction, and a variation in position of the robot from the robot's encoders resulting from the solicitation.

2 more elements

An apparatus for measuring deviation of a multi-jointed robot under load, the apparatus comprising:

a robot with an end flange;
a friction bearing element (FBE) mounted to the end flange directly, or via an end effector or end tooling;
a force sensor within the robot, or mounted to the end flange directly, or via an end effector, end tooling, or the FBE;
and
a computer processor with a memory, in communication with the force sensor and the robot,
wherein the computer processor has program instructions for:
directing the robot to move the FBE into a measurement pose adjacent to a constraint located within an envelope of the robot;
applying a first force to press the FBE into tribological contact with the constraint;
soliciting the robot to move in one direction that is resisted by the tribological contact while the tribological contact is maintained, where the solicitation exerts a second force that is insufficient to overbear the tribological contact's resistance;
and
quantifying the second force and a change in position of the robot from the robot's encoders due to the resistance to the solicitation, and using same to determine a deviation of the robot.

8 more elements

A kit for use in determining deviation of a multi-jointed robot under load, the kit comprising a friction bearing element (FBE) for mounting to an end of the robot and one or more of:

b) non-transitory computer readable program instructions for:
determining a variation in position of the robot by from a difference between encoder positions at first and second stable positions, wherein at least the second stable position is a result of a force exerted in a tribologically resisted direction after the robot is pressed against a constraint to form a tribological contact;
receiving from a force sensor mounted directly or indirectly to the robot, at least select force feedback for computing at least a difference between forces applied at the first and second stable positions;
and
calculating a deviation of the robot under a load as the variation in position associated with difference between the forces;
and
c) non-transitory computer readable program instructions for obtaining a specification of the constraint, and a location of the FBE mounted directly or indirectly to the robot, and commanding the robot to perform the following steps:
directing the robot to move the FBE into a measurement pose adjacent to a constraint located within an envelope of the robot;
apply a first force to press the FBE into tribological contact with the constraint;
solicit the robot to move in one direction that is resisted by the tribological contact while the tribological contact is maintained, where the solicitation exerts a second force that is insufficient to overbear the tribological contact's resistance;
and
record a position of the robot as determined from its encoders, when the second force is solicited.

9 more elements

Dependencies are inferred from the claim text.

Multi-jointed robot deviation under load determination

Life of this patent

Multi-jointed robot deviation under load determination

Life of this patent

Abstract

Claims22