Abstract
Industrial robots are getting widely applied due to their low use-cost and high flexibility. However, the low absolute positioning accuracy limits their expansion in the area of high-precision manufacturing. Aiming to improve the positioning accuracy, a compensation method for the positioning error is put forward in terms of the optimization of the experimental measurement space and accurate modelling of the positioning error. Firstly, the influence of robot kinematic performance on the measurement accuracy is analysed, and a quantitative index describing the performance is adopted. On this basis and combined with the joints motion characteristics, the optimized measurement space in joint space as well as Cartesian space is obtained respectively, which can provide accurate measurement data to the error model. Then the overall model of the positioning error is constructed based on modified Denavit–Hartenberg method, in which the geometric errors and compliance errors are considered comprehensively, and an error decoupling method between them is carried out based on the error-feature analyses. Experiments on the KUKA KR210 robot are carried out finally. The mean absolute positioning accuracy of the robot increases from 1.179 mm to 0.093 mm, which verifies the effectiveness of the compensation methodology in this article.
Highlights
Industrial robots are getting widely used in more and more industrial applications gradually because of their prominent advantages such as the low use-cost and high flexibility
The absolute positioning accuracy of robots is generally larger than 0.3 mm, which can hardly satisfy the requirement of high-precision machining and greatly limits their application scope.[2]
Replace 20 groups of measured positions in the optimized measurement space by those in the unoptimized space and identify the parameter errors based on the new data
Summary
Industrial robots are getting widely used in more and more industrial applications gradually because of their prominent advantages such as the low use-cost and high flexibility. Not limited to the simple jobs such as pick-and-place, they find their niche in manufacturing operations such as deburring and drilling, which require special attention to the manufacturing accuracy.[1]. The trend is that modern industrial robots will someday replace the less flexible and costlier computer numerical control (CNCs) in many areas. There are some obstacles such as the low absolute positioning accuracy. The absolute positioning accuracy of robots is generally larger than 0.3 mm, which can hardly satisfy the requirement of high-precision machining and greatly limits their application scope.[2] Up to the present time, the applications of the robots in high-precision machining are relatively few.
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