Method and device for the improvement of the pose accuracy of effectors on mechanisms and for the measurement of objects in a workspace
First Claim
1. A method for improving the pose accuracy of a mechanism in a workspace, wherein the mechanism is movable in at least one axis with tolerances and includes an effector, at least one effector object is mounted via a rigid connection to the effector eccentric to the at least one axis of the mechanism in an estimated pose with a tolerance in position and orientation, at least one reference object is arranged in the workspace with a tolerance in position and orientation, and a computer system is connected to the mechanism having a measurement control program, a parameter identification program, and a mechanism control program, the at least one effector object and the at least one reference object forming at least one trigger/detector pair comprising a signal trigger device and a signal detector for triggering and detecting a binary signal, wherein a totality of signal poses of the signal detector relative to the trigger device in which a signal is triggered on the signal detector is described by at least one non-trivial characteristic equation, said method comprising the following steps:
- (a) selecting a proximity sequence N of a finite number of proximity poses for the at least one trigger-detector pair, each of the proximity poses being located in the vicinity of a respective one of signal poses, wherein the proximity sequence N is selected such that the following criteria are fulfilled;
DG(N)≧
DG(AI)/15whereby the distance on an arbitrary straight line G between two neighbouring points of the projection of the proximity sequence N onto G is at the most DG(N)/4, wherein DGis a function which maps each subset of the set A1 to the distance between those two points of the projection of this subset on G which are at maximum distance from each other on G;
AI is the space of all those reachable effector poses of the given mechanism which result from elementary kinematic calculations on the basis of the known mechanism model which in turn is afflicted with tolerances;
G is an arbitrary straight line which contains at least two points of SI; and
SI is a subset of AI which is denotes the space of proximity poses and is defined by the totality of all those effector object poses where a signal would be expected according to a mathematical calculation based on the parameter values of the known tolerance-afflicted mechanism model, the estimated pose of the reference objects in space, and the estimated pose of the effector object on the mechanism;
(b) searching for a nearby signal pose for each of the proximity poses consecutively through movement of one of the at least one effector object and the mechanism using a simple search algorithm until a signal pose is detected;
(c) passing a momentary joint configuration of the mechanism onto the computer system after the detection thereof in said step (b) and storing the momentary joint configuration in the computer system as a data record;
(d) using a parameter identification program to identify the true values of one of the parameters influencing the pose accuracy of the mechanism and user-specific subsets of this parameter set, whereby a scaling factor is used for the identification of all length-parameters.
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Abstract
A device and a method for measuring the pose of mechanisms includes at least one effector object fixedly joined to a mechanism (e.g., industrial robot, hexapod) in which the at least one effector object moves along one of several axes. The ideal, effective shape of the at least one effector object is a point, a straight line, a plane, an ellipsoid, a cylinder, a hyperboloid or a combination thereof. The movable effector objects interact with reference objects which are arranged in defined positions relative to the mechanism. The interactions are detected by a suitable sensor. Once said interactions are detected, only the pertaining joint configuration of the mechanism is transmitted to the information processing unit and evaluated and no further continuous values of measuring parameters are required for the evaluation.
56 Citations
31 Claims
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1. A method for improving the pose accuracy of a mechanism in a workspace, wherein the mechanism is movable in at least one axis with tolerances and includes an effector, at least one effector object is mounted via a rigid connection to the effector eccentric to the at least one axis of the mechanism in an estimated pose with a tolerance in position and orientation, at least one reference object is arranged in the workspace with a tolerance in position and orientation, and a computer system is connected to the mechanism having a measurement control program, a parameter identification program, and a mechanism control program, the at least one effector object and the at least one reference object forming at least one trigger/detector pair comprising a signal trigger device and a signal detector for triggering and detecting a binary signal, wherein a totality of signal poses of the signal detector relative to the trigger device in which a signal is triggered on the signal detector is described by at least one non-trivial characteristic equation, said method comprising the following steps:
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(a) selecting a proximity sequence N of a finite number of proximity poses for the at least one trigger-detector pair, each of the proximity poses being located in the vicinity of a respective one of signal poses, wherein the proximity sequence N is selected such that the following criteria are fulfilled;
DG(N)≧
DG(AI)/15whereby the distance on an arbitrary straight line G between two neighbouring points of the projection of the proximity sequence N onto G is at the most DG(N)/4, wherein DGis a function which maps each subset of the set A1 to the distance between those two points of the projection of this subset on G which are at maximum distance from each other on G;
AI is the space of all those reachable effector poses of the given mechanism which result from elementary kinematic calculations on the basis of the known mechanism model which in turn is afflicted with tolerances;
G is an arbitrary straight line which contains at least two points of SI; and
SI is a subset of AI which is denotes the space of proximity poses and is defined by the totality of all those effector object poses where a signal would be expected according to a mathematical calculation based on the parameter values of the known tolerance-afflicted mechanism model, the estimated pose of the reference objects in space, and the estimated pose of the effector object on the mechanism;
(b) searching for a nearby signal pose for each of the proximity poses consecutively through movement of one of the at least one effector object and the mechanism using a simple search algorithm until a signal pose is detected;
(c) passing a momentary joint configuration of the mechanism onto the computer system after the detection thereof in said step (b) and storing the momentary joint configuration in the computer system as a data record;
(d) using a parameter identification program to identify the true values of one of the parameters influencing the pose accuracy of the mechanism and user-specific subsets of this parameter set, whereby a scaling factor is used for the identification of all length-parameters. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 24)
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23. A method for improving the pose accuracy of a mechanism in a workspace, wherein the mechanism is movable in at least one axis with tolerances and includes an effector, at least one effector object is mounted via a rigid connection to the effector eccentric to the at least one axis of the mechanism in an estimated pose with a tolerance in position and orientation, at least one immaterial reference object is arranged in the workspace with an exact known pose, and a computer system is connected to the mechanism having a measurement control program, a parameter identification program, and a mechanism control program, the at least one effector object and the at least one immaterial reference object forming a trigger/detector pair comprising a signal trigger device and a signal detector for triggering and detecting a binary signal, wherein a totality of signal poses of the signal detector relative to the trigger device in which a signal is triggered on the signal detector is described by at least one non-trivial characteristic equation, said method comprising the following steps:
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(a) selecting a proximity sequence N such that it contains at least one proximity pose arranged at a reference object neighbouring a target pose;
(b) successively searching for detection of a signal pose nearby to the at least one proximity pose through the motion of one of the effector object and mechanism via a simple search algorithm;
(c) passing the momentary joint configuration of the mechanism onto the computer system and storing the momentary joint configuration as a data record upon detection of the signal in said step (b);
(d) using the computer system to calculate, for each data record, the incorrect pose in the workspace resulting mathematically on the basis of the mechanism parameters currently known to the controller; and
(e) calculating a correction movement from the difference between the signal poses and the associated incorrect poses, through elementary interpolation procedures and elementary error compensation algorithms, the correction movement compensating the deviation of the pose actually steered for by the mechanism control from the desired pose, whereby the scalar factor, which was determined from the exactly known pose of the reference object, is used for the calculation of the correction movement from incorrect poses and signal poses.
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25. A device for improving the pose accuracy of a mechanism and for pose measurement of objects in the work space, comprising:
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a computer system comprising measurement control program, a parameter identification program, and a mechanism control program;
a mechanism moveable in at least one axis which has an effector, said mechanism connected to said computer system;
at least one pair of calibration objects, each pair of said at least one pair comprises an effector object rigidly connected with said effector and mounted eccentrically to the at least one axis of said mechanism and a reference object fixedly arranged relative to said mechanism in said workspace, each pair comprising a signal trigger device and a signal detector for binary signals; and
an installation for determining a scaling factor. - View Dependent Claims (26, 27, 28, 29, 30)
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31. The device for improving the pose accuracy of a mechanism and for pose measurement of objects in a work space, comprising:
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a computer system comprising measurement control program, a parameter identification program, and a mechanism control program;
a mechanism having tolerances and moveable in at least one axis with an effector;
at least one effector object in estimated pose with tolerance in position and orientation is rigidly connected with said effector and mounted eccentrically to said at least one axis of said mechanism;
at least one immaterial reference object arranged fixedly in the workspace and the pose of which is known exactly, wherein each one of said at least one effector object forms a trigger/detector pair with each one of said at least one reference object, said trigger/detector pair comprising a signal trigger device and a signal detector such that each pair is suitable for effecting a triggering and detection of at least binary signals, wherein a totality of signal poses of said signal detector relative to said signal trigger device in which a signal is triggered on the detector are described by at least one non-trivial characteristic equation.
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Specification