Inclusion of Bidirectional Angular Positioning Deviations in the Kinematic Model of a Six-DOF Articulated Robot for Static Volumetric Error Compensation
Md Moktadir Alam, Soichi Ibaraki, Koki Fukuda, Sho Morita, Hiroshi Usuki, Naohiro Otsuki, Hirotaka Yoshioka
Abstract
To improve a robot’s absolute positioning accuracy,
researchers have extensively studied the robot kinematic model
containing position and orientation errors of rotary axes average
lines, widely known as Denavit–Hartenberg (D-H) parameters. To
further improve the absolute positioning accuracy of industrial
robots, this paper proposes a novel kinematic model and its
identification s cheme. T he p roposed k inematic m odel f or a
serial-linked industrial robot contains the bidirectional angular
positioning deviations of each rotary axis, represented in a lookup
table, in addition to its D-H parameters. The angular positioning
deviations of the rotary axes are modeled as a function of
angular command positions, along with the direction of rotation
to model the influence of backlash. This paper also proposes
a novel approach to identify the proposed kinematic model
with the bidirectional angular positioning deviations using a
laser tracker with indexing each rotary axis at specified angular
positions (“circle point method”). Moreover, the model-based
compensation technique is being experimentally investigated to
validate the prediction accuracy of the proposed model. The
findings o f t he e xperiment s howed t hat t he p roposed model
enhances the robot’s absolute positioning accuracy significantly
over the entire workspace.
Keywords: Industrial Robot, Kinematic Model, Angular Positioning Deviation, Laser Tracker, Lookup table.
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