Method and System to Provide Improved Accuracies in Multi-Jointed Robots Through Kinematic Robot Model Parameters Determination
First Claim
1. A method providing improved pose accuracies in a multi-jointed robot, said method comprising:
- providing a pair of reference objects each of a known geometry and each defining a unique constraint point of unknown pose, distance between constraint points from said reference objects forming a known constraint distance;
providing an effector object on the robot, said effector object is movable by the robot in at least two axes and is configured to indicate an encounter with at least one of said reference objects;
providing a plurality of encounters of said effector object with said reference objects;
determining joint values of the robot for each of said encounters;
calculating a first pose of a first reference point from said joint values determined from at least four of said encounters with a first one of said reference objects, said first pose corresponding to a first calculated pose of said constraint point of said first reference object;
calculating a second pose of a second reference point from said joint values determined from at least four of said encounters with a second one of said reference objects, said second pose corresponding to a second calculated pose of said constraint point of said second reference object;
calculating a first difference between said first or second pose and a trial pose of said constraint point for said first or second reference object, respectively;
calculating a second difference between a calculated constraint distance and said known constraint distance, said calculated constraint distance is the distance between said trial poses of said constraint points of said pair of reference objects;
identifying kinematic model parameters of said robot model and trial poses of said constraint points of said pair of reference objects which minimize said first and second differences; and
,using said identified kinematic model parameters for improved pose accuracies in the multi-jointed robot.
1 Assignment
0 Petitions
Accused Products
Abstract
A method and system to provide improved accuracies in multi jointed robots through kinematic robot model parameters determination are disclosed. The present invention calibrates multi-jointed robots by using the chain rule for differentiation in the Jacobian derivation for variations in calculated poses of reference points of a reference object as a function of variations in robot model parameters. The present invention also uses two such reference objects and the known distance therebetween to establish a length scale, thus avoiding the need to know one link length of the robot. In addition, the present invention makes use of iterative methods to find the optimum solution for improved accuracy of the resultant model parameters. Furthermore, the present invention provides for determination of the end joint parameters of the robot, including parameters defining the tool attachment mechanism frame, which allows for interchange of tools without subsequent calibration.
145 Citations
24 Claims
-
1. A method providing improved pose accuracies in a multi-jointed robot, said method comprising:
-
providing a pair of reference objects each of a known geometry and each defining a unique constraint point of unknown pose, distance between constraint points from said reference objects forming a known constraint distance; providing an effector object on the robot, said effector object is movable by the robot in at least two axes and is configured to indicate an encounter with at least one of said reference objects; providing a plurality of encounters of said effector object with said reference objects; determining joint values of the robot for each of said encounters; calculating a first pose of a first reference point from said joint values determined from at least four of said encounters with a first one of said reference objects, said first pose corresponding to a first calculated pose of said constraint point of said first reference object; calculating a second pose of a second reference point from said joint values determined from at least four of said encounters with a second one of said reference objects, said second pose corresponding to a second calculated pose of said constraint point of said second reference object; calculating a first difference between said first or second pose and a trial pose of said constraint point for said first or second reference object, respectively; calculating a second difference between a calculated constraint distance and said known constraint distance, said calculated constraint distance is the distance between said trial poses of said constraint points of said pair of reference objects; identifying kinematic model parameters of said robot model and trial poses of said constraint points of said pair of reference objects which minimize said first and second differences; and
,using said identified kinematic model parameters for improved pose accuracies in the multi-jointed robot. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
-
-
13. A system providing improved pose accuracies in a robot having a multi-jointed arm, said system comprising:
-
a controller configured to interpret coordinates within a three dimensional space, move the multi-jointed ann to a location within the three dimensional space that corresponds to the coordinates, and determine joint values of each joint in the multi-jointed arm; a pair of reference objects each of a known geometry situated within the three dimensional space, each said reference objects defining a unique constraint point of unknown pose and the distance between constraint points from said reference objects forming a known constraint distance therebetween; an effector object provided on the multi-jointed arm, said effector object is configured to indicate an encounter with at least one of said reference objects; and a processor configured to perform parameter identification, wherein said controller is configured to; provide a plurality of encounters of said effector object with said reference objects, and, wherein said controller is comprised of said processor, which processor is configured to; determine joint values of the multi-jointed arm for each of said encounters, calculate a first pose of a first reference point from said joint values determined from at least four of said encounters with a first one of said reference objects, said first pose corresponding to a calculated pose of the constraint point of said first reference object, calculate a second pose of a second reference point from said joint values determined from at least four of said encounters with a second one of said reference objects, said second pose corresponding to a calculated pose of the constraint point of said second reference object, calculate a first difference between said first or second pose and a trial pose of said constraint point for said first or second reference object, respectively, calculate a second difference between a calculated constraint distance and said known constraint distance, said calculated constraint distance is the distance between said trial poses of said constraint points of said pair of reference objects, identify kinematic model parameters of said robot model and said trial poses of the constraint points of said pair of reference objects, which minimize said first and second differences, and wherein said controller is further configured to use said identified kinematic model parameters for improved pose accuracies in the multi-jointed robot. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
-
Specification