Method for positioning a tool of a multi-joint robot
First Claim
1. A method for positioning a tool of a multi-joint robot having a plurality of rotatable joints (Gi-1, Gi, Gi+1 ) defining robot joint axes, with one of the joints being connected to the tool and the location and the orientation of the tool being represented in a reference coordinate system and the respective position of the tool relative to the reference coordinate system and the angular positions of the robot joint axes being linked by a coordinate-transformation equation system having parameters which are determined by the desired distances and desired directions of the robot joints representing the ideal kinematic of the robot, comprising the following steps:
- (a) determining a preliminary desired angular position (θ
i-1, θ
i, θ
i+1) for each of the joints, respectively, for a desired position in space (x) of the tool based upon reference distances (ai-1, ai, ai+1 di-1, di, di+1) and directions of the joint axes required to position the tool in the desired position;
(b) determining the positioning error (Δ
x) of the tool due to the difference between the reference distance (ai-1, ai, ai+1, di-1, di, di+1) and the desired directions and the actual spacings and actual direction of the joints (Gi-1, Gi, Gi+1);
(c) transforming the determined positioning error (Δ
x) into corresponding angular correction values (Δ
θ
) for the preliminary desired angular positions (θ
i-1,θ
i, θ
i+1) of the joints (Gi-1, Gi, Gi+1) by means of the inverse Jacobi matrix (Fθ
(θ
v,Fref)-1) of the ideal kinematic of the robot of the coordinate-transformation equation system;
(d) calculating the error-corrected angular position (θ
f) for each of the joints (Gi-1, Gi, G+1) by addition of the angular correction values (Δ
θ
) determined in step c) to the preliminary desired angular positions (θ
i-1,θ
i, θ
i+1) determined in step a); and
(e) moving the tool to the desired position by rotating the joints in accordance with the error-corrected angular position (θ
f) calculated in step (d).
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Abstract
A method for positioning a tool of a multi-joint robot is disclosed in which an incorrect positioning of the tool resulting from nonideal geometrical relationships is compensated by the following steps: determining a preliminary desired angular position for each of the joints for a desired position in space of the tool based upon the reference distances and joint axis directions required to position the tool in the desired position; determining the positioning error of the tool due to the differences between the reference distances and the desired directions and the actual spacings and actual directions of the joints; transforming the determined positioning error into corresponding angular correction values for the preliminary desired angular positions of the joints by means of an inverse Jacobi matrix coordinate-transformation equation system; calculating the error-corrected angular position for each of the joints by addition of the angular correction values to the preliminary desired angular positions; and moving the tool to the desired position by rotating the joints in accordance with the error-corrected angular position calculated.
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Citations
1 Claim
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1. A method for positioning a tool of a multi-joint robot having a plurality of rotatable joints (Gi-1, Gi, Gi+1 ) defining robot joint axes, with one of the joints being connected to the tool and the location and the orientation of the tool being represented in a reference coordinate system and the respective position of the tool relative to the reference coordinate system and the angular positions of the robot joint axes being linked by a coordinate-transformation equation system having parameters which are determined by the desired distances and desired directions of the robot joints representing the ideal kinematic of the robot, comprising the following steps:
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(a) determining a preliminary desired angular position (θ
i-1, θ
i, θ
i+1) for each of the joints, respectively, for a desired position in space (x) of the tool based upon reference distances (ai-1, ai, ai+1 di-1, di, di+1) and directions of the joint axes required to position the tool in the desired position;(b) determining the positioning error (Δ
x) of the tool due to the difference between the reference distance (ai-1, ai, ai+1, di-1, di, di+1) and the desired directions and the actual spacings and actual direction of the joints (Gi-1, Gi, Gi+1);(c) transforming the determined positioning error (Δ
x) into corresponding angular correction values (Δ
θ
) for the preliminary desired angular positions (θ
i-1,θ
i, θ
i+1) of the joints (Gi-1, Gi, Gi+1) by means of the inverse Jacobi matrix (Fθ
(θ
v,Fref)-1) of the ideal kinematic of the robot of the coordinate-transformation equation system;(d) calculating the error-corrected angular position (θ
f) for each of the joints (Gi-1, Gi, G+1) by addition of the angular correction values (Δ
θ
) determined in step c) to the preliminary desired angular positions (θ
i-1,θ
i, θ
i+1) determined in step a); and(e) moving the tool to the desired position by rotating the joints in accordance with the error-corrected angular position (θ
f) calculated in step (d).
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Specification
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- Resources
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Current AssigneeSiemens AG
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Original AssigneeSiemens AG
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InventorsStelzer, Joerg
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Primary Examiner(s)Ruggiero, Joseph
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Application NumberUS07/184,371Time in Patent Office635 DaysField of Search364/513, 364/167.01, 364/474.28, 364/474.35, 364/474.36, 318/568, 318/568.11, 318/568.15, 318/568.19, 318/568.22, 901/2, 901/15US Class Current700/262CPC Class CodesG05B 19/414 Structure of the control sy...
