Automated calibration of an optomechanical derotator using 6-axes parallel kinematics and industrial image processing algorithms

Infrared Sensors, Devices, and Applications X

Reithmeier

2020

Self Cite

Due to their high availability and versatility, rolling bearings are a standard solution for mounting and support of rotating components. The service life of an entire rotating machine is often limited by the service life of rolling bearings. This can be shorter than expected if the rolling bearing is operated in harmful operating conditions, e.g. in the presence of slip. Slip means that there is a deviation between the theoretical angular velocity of the rolling element set and the actual angular velocity. In this context, slip is harmful if it leads to increased friction and thus heating of the bearing. The occurrence and properties of slip are not completely understood yet. Therefore, it is of interest to investigate a relationship between slip and heating of the rolling bearing in order to better understand damages of the rolling bearing. In this work, a method is presented in which, in addition to slip measurements with a high-speed camera, a thermal imaging camera is used to investigate the heating of the bearing during operation. Since the rotational movement and exposure time of the camera would cause motion blur, the thermal imaging camera is operated together with a derotator to optically eliminate the rotational movement. The investigations of the rolling bearing are carried out under different operating conditions (different loads and rotational speeds), which have an influence on the slip behavior of the bearing. Thus, the potential of this investigation method for deepening the understanding of heating and friction in rolling bearings is demonstrated.

Section: Functionality Of the Derotatormentioning

confidence: 99%

Investigation of harmful slip in a rolling bearing using a thermographic camera with a derotator

Infrared Sensors, Devices, and Applications X

Reithmeier

2020

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“…To achieve coaxial alignment, the mathematical model between the movement of the image and the misalignment of the two axes is established, in which the trajectory of a marker can be described with the limaçon of Pascal 7,8 . The parameters of the limaçon correlate with the magnitude of the misalignment.…”

Section: Introductionmentioning

confidence: 99%

“…The parameters can be minimized by adjusting the pose of the derotator to achieve the coaxial alignment. However, this model cannot distinguish the shift and the tilt between the two axes 7 , thus a procedure to make the two axes parallel is need. An alternative approach to achieve the coaxial alignment is adjusting the pose of the derotator directly based on the transformation matrix between the two axes.…”

Section: Introductionmentioning

confidence: 99%

Rotation axis estimation for the derotator calibration with machine vision measurement of the auxiliary laser

Yin

Optical Metrology and Inspection for Industrial Applications V

Pape

et al. 2018

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A key problem when using the derotator is to ensure the coaxial alignment between the optical axis of the derotator and the rotation axis of the measured object. Moreover, accurate measurement of the rotation axis is the prerequisite of achieving the coaxial alignment. In this paper, we propose a strategy for estimation of the rotation axis with the assistant of an auxiliary laser and a binocular stereo vision sensor. When a laser source is temporarily attached to the measured object or the rotor shaft, the rotation of the laser will generate a ruled surface. The binocular sensor can accurately measure the coordinates of laser dots in three-dimensional (3D) space. The pose vector of the laser in each certain rotation angle can be estimated with measured 3D coordinates of the laser dots. Finally, the rotation axis of the object can be estimated with multiple pose vectors considering the constraint of the fixed axis rotation. The validity and precision of this proposed strategy are demonstrated by means of experiments.

“…By using a derotator, vibration measurements using a LDV can be extended to the rotating object during operation, so that the object can be measured as if at rest. Other applications of the derotator and its concept are described detailed in [1] and [2]. However, the constraint between the derotator and the measurement object has to be fulfilled before measurements are made possible.…”

Section: Introductionmentioning

confidence: 99%

Identification and Tracking‐Control for an Optomechatronical Image Derotator Using Neural Networks

Proc Appl Math and Mech

Rohloff

Pape

et al. 2016

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In this paper an optomechatronical image derotator is used for vibration measurements on rotating objects. First of all, the concept of the derotator is explained and it is shown that the phase position and the rotational velocity of the derotator and the measurement object have to be aligned. Therefore, a highly dynamic tracking-control is needed. Considering the nonlinear friction of the synchronous motor, a model of the system which considers this non-linearity is evolved. This is accomplished by using neural networks for the approximation of the friction term. In this case General Regression Neural Networks (GRNN) are used for the learning algorithm. Moreover, the system's parameters, eg. the friction term and the inertia, are identified based on the nonlinear model. Then a feedback control is designed by using the controllable canonical form through feedback linearization. Finally, the results of vibration measurements on a rotating blisk using the nonlinear control concept for the derotator are shown.