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Prediction of position errors for an industrial robot, using a model of the robot with parameters acquired from the clamping procedure

Söder-Hoorn, Anders (2015)
Department of Automatic Control
Abstract
A robot should follow a given path as accurately as possible. There are however almost always deviations from the desired path, and when the deviations become too large it may be a problem. Some of the deviations stem from transmissions of the robot, and the deviations become more pronounced when there are process forces and gravitational forces present, that affect the transmissions. When position is measured and controlled on the motor side, characteristics of the transmission are not accounted for in the control of the robot, resulting in deviations from the desired path. There are also deviations from the desired path that stem from links of the robot, due to process forces and gravitational forces that affect the links.

To predict... (More)
A robot should follow a given path as accurately as possible. There are however almost always deviations from the desired path, and when the deviations become too large it may be a problem. Some of the deviations stem from transmissions of the robot, and the deviations become more pronounced when there are process forces and gravitational forces present, that affect the transmissions. When position is measured and controlled on the motor side, characteristics of the transmission are not accounted for in the control of the robot, resulting in deviations from the desired path. There are also deviations from the desired path that stem from links of the robot, due to process forces and gravitational forces that affect the links.

To predict the deviations that stem from the transmissions, models of the transmissions were developed and used. Models that should be able to predict the deviations that stem from the links were also developed. To acquire data about the characteristics of the transmissions of a robot, tailored experiments were performed. To acquire the data, the robot’s end-effector was locked to a stiff point in space, the robot’s motors were run, and the robot’s sensors were used to log the data. This procedure is known as a clamping procedure. The collected data were processed to derive parameters that were used in the models of the transmissions. The robot that was used was a KR 300 R2500 ULTRA, which is an industrial robot with six degrees of freedom.

Simulations with the models of the transmissions were able to recreate the data from the clamping procedure with great accuracy. This shows that the models of the transmissions, with the parameters derived from the clamping procedure, capture characteristics of the robot, that are not taken into account in the control of the robot, which leads to deviations from the desired path.

The next step, that is not a part of this thesis, is to use a model of the whole robot, that contains the models of the transmissions and the links, and to validate that the robot model can recreate the deviations from a given path that the robot takes. (Less)
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author
Söder-Hoorn, Anders
supervisor
organization
year
type
H3 - Professional qualifications (4 Years - )
subject
other publication id
ISRN LUTFD2/TFRT--5991--SE
language
English
id
8254043
date added to LUP
2015-12-04 09:10:38
date last changed
2015-12-04 09:10:38
@misc{8254043,
  abstract     = {A robot should follow a given path as accurately as possible. There are however almost always deviations from the desired path, and when the deviations become too large it may be a problem. Some of the deviations stem from transmissions of the robot, and the deviations become more pronounced when there are process forces and gravitational forces present, that affect the transmissions. When position is measured and controlled on the motor side, characteristics of the transmission are not accounted for in the control of the robot, resulting in deviations from the desired path. There are also deviations from the desired path that stem from links of the robot, due to process forces and gravitational forces that affect the links.

To predict the deviations that stem from the transmissions, models of the transmissions were developed and used. Models that should be able to predict the deviations that stem from the links were also developed. To acquire data about the characteristics of the transmissions of a robot, tailored experiments were performed. To acquire the data, the robot’s end-effector was locked to a stiff point in space, the robot’s motors were run, and the robot’s sensors were used to log the data. This procedure is known as a clamping procedure. The collected data were processed to derive parameters that were used in the models of the transmissions. The robot that was used was a KR 300 R2500 ULTRA, which is an industrial robot with six degrees of freedom.

 Simulations with the models of the transmissions were able to recreate the data from the clamping procedure with great accuracy. This shows that the models of the transmissions, with the parameters derived from the clamping procedure, capture characteristics of the robot, that are not taken into account in the control of the robot, which leads to deviations from the desired path. 

The next step, that is not a part of this thesis, is to use a model of the whole robot, that contains the models of the transmissions and the links, and to validate that the robot model can recreate the deviations from a given path that the robot takes.},
  author       = {Söder-Hoorn, Anders},
  language     = {eng},
  note         = {Student Paper},
  title        = {Prediction of position errors for an industrial robot, using a model of the robot with parameters acquired from the clamping procedure},
  year         = {2015},
}