Robot arm with adaptive three-dimensional boundary in free-drive
AssigneeUniversal Robots A/S
InventorJacob Gregers Hansen
Life of this patent
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Abstract
The invention relates to a robot controller controlling a robot arm, the robot controller is configured to maintain the robot arm in a static posture when only gravity is acting on the robot arm and allow change in posture of the robot arm 5 when an external force different from gravity is applied to the robot arm. The free-drive mode of operation is activatable by a user establishing a free-drive activation signal to the robot controller, which in free-drive mode of operation is configured within at a free-drive safety period to allow a part of said robot arm to be moved within a virtual three-dimensional geometric shape 10 surrounding the part of the robot arm.
Claims20
A robot controller for controlling a robotic arm, the robot controller for switching the robotic arm from a first mode of operation to a free-drive mode of operation in response to a free-drive mode signal, where, in the free-drive mode of operation, the robot controller is configured to perform operations comprising:
- keeping the robotic arm in a posture that is static when only gravity acts on the robotic arm;
- allowing a change in the posture of the robotic arm when an external force different from gravity is applied to the robotic arm;
- monitoring a value of at least one parameter based on a signal of at least one sensor associated with a joint of the robotic arm;
- comparing the value of the at least one parameter to at least one threshold value;
- keeping the robotic arm in the free-drive mode of operation when the value of the at least one parameter does not exceed the at least one threshold value during a free-drive safety period;
- wherein the at least one threshold value is based on a virtual three-dimensional geometric shape surrounding a part of the robotic arm;
- wherein the free-drive safety period comprises a time period within which at least part of the robotic arm is allowed to move within the virtual three-dimensional geometric shape without creating a hazard;
- and
- redefining the virtual three-dimensional geometric shape following expiration of the free-drive safety period and when the value of the at least one parameter has not exceeded the virtual three-dimensional geometric shape during the free-drive safety period.
A method of operating a robotic arm in a free-drive mode of operation, where the robotic arm has been switched into the free-drive mode of operation by a robot controller in response to receiving a free-drive mode signal set by a user, where the free-drive mode of operation comprises:
- keeping the robotic arm in a posture that is static when only gravity acts on the robotic arm;
- changing the posture of the robotic arm when an external force different from gravity is applied to the robotic arm;
- monitoring a value of at least one parameter associated with a sensor of a joint on the robotic arm;
- comparing the value of the at least one parameter to at least one threshold value, where the at least one threshold value is based on a virtual three-dimensional geometric shape surrounding a part of the robotic arm;
- keeping the robotic arm in the free-drive mode of operation when the value of the at least one parameter does not exceed the virtual three-dimensional geometric shape within at a free-drive safety period, where the free-drive safety period comprises a time period within which at least part of the robotic arm is allowed to move within the virtual three-dimensional geometric shape without creating a hazard;
- and
- redefining the virtual three-dimensional geometric shape following expiration of the free-drive safety period and when the value of the at least one parameter has not exceeded the virtual three-dimensional geometric shape during the free-drive safety period.
A system comprising a robotic arm, the system comprising:
- a base;
- a tool flange;
- joints connecting the base and the tool flange, each of the joints comprising:
- an output flange rotatable in relation to a body of a joint;
- a motor configured to rotate the output flange;
- and
- at least one sensor for providing a sensor signal indicative of at least one of an angular position of the output flange, an angular position of a shaft of the motor, or a current of the motor;
- and
- at least one robot controller configured to control one or more of the joints by controlling motor torque of one or more motors based on one or more sensor signals, the at least one robot controller being configured to perform operations comprising:
- monitoring a value of at least one parameter that is based on the sensor signal of the at least one sensor for the one or more of the joints;
- comparing the value of the at least one parameter to at least one threshold value;
- keeping the robotic arm in a free-drive mode of operation when the value of the at least one parameter does not exceed the at least one threshold value during a free-drive safety period;
- wherein the at least one threshold value is based on a virtual three-dimensional geometric shape surrounding a part of the robotic arm;
- redefining the virtual three-dimensional geometric shape following expiration of the free-drive safety period and when the value of the at least one parameter has not exceeded the virtual three-dimensional geometric shape during the free-drive safety period;
- wherein the free-drive safety period comprises a time period within which at least part of the robotic arm is allowed to move within the virtual three-dimensional geometric shape without creating a hazard;
- and
- wherein in the free-drive mode of operation, a posture of the robotic arm is changeable through application of force to the robotic arm and where, in the absence of the force, the at least one robot controller is configured to maintain a posture of the robotic arm.
Dependencies are inferred from the claim text.