Ján Vachálek

Collision-free manipulation of a robotic arm using the MS Windows Kinect 3D optical system

This article presents the collision-free manipulation of a robotic arm mounted to a mobile robotic unit, using the MS Windows Kinect 3D optical camera system. The 3D optical system is used to recognize objects, aiding the collision-free manipulation of the said objects with the arm of a mobile robotic system (MRS). The placement of the optical system directly on the robotic arm is essential to ensure the autonomy of the overall system. The MRS is able to recognize pre-defined objects in three dimensional space and approach and manipulate these automatically using its robotic arm. The aim of this article is to present the algorithms used in the mobile robot to guarantee the collision-free manipulation of the MRS with objects. The novelty of our approach lies in the a priori collision avoidance strategy, instead of solving collision states as they occur. In addition to this, the article presents the localization of objects in space. For this, randomly placed balls are localized by the MRS, estimating their real coordinates. Instead of using the standard RGB colorspace, we propose to utilize the HSV colorspace to assess object coordinates, since it provides more consistent results in case the ambient lightning intensity varies.

The digital twin of an industrial production line within the industry 4.0 concept

This article presents the digital twin concept, which is an augmented manufacturing project created in close collaboration by SOVA Digital and the Institute of Automation, Measurement and Applied Informatics (ÚAMAI), of the Faculty of Mechanical Engineering, Slovak University of Technology in Bratislava with the support of SIEMENS. The project is a technological concept focusing on the continuous optimization of production processes, proactive maintenance, and continuous processing of process data. This project is the basis for further work to promote the concept of Industry 4.0. for the needs of the industry subjects within Slovakia. Its basic goal is to support the existing production structures within the automotive industry and the most efficient use of resources by augmented production and planning strategies, such as the digital twin presented here.

From stochasticism to determinism in evaluation of human postural responses

The Center of Pressure (COP) signal is a kind of human postural response and it is an established indicator of human ability to maintain balanced posture. Its form of the statokinesigram has complicated profile, which suggests stochastic or chaotic nature of COP movement. Here is presented developed statokinesigram trajectory (DST) as a basis of method for human postural response analysis. Since DST does not show signs of stochastic behavior it is suitable for modeling with help of linear system theory. In this study, volunteers postural responses were affected by bilateral vibration stimuli of Achilles tendons. This vibration stimulus causes nonlinear response in anterior-posterior direction. DST allows to analyze this phenomenon through mathematical model in form of a transfer function. Its estimated parameters are useful in evaluation of human posture control.

Automatic machining system for the refurbishment of degraded welds in piping systems

Degradation of dissimilar metal welds in the piping systems of power plants is recognized as a significant ageing factor. Hence, close scientific attention is paid to various degradation mechanisms concerned with dissimilar metal welds, as well as to welding metallurgy. However, the process of dissimilar metal weld refurbishment consisting of the weld groove machining and subsequent repair welding is based on obsolete methods. Particularly, the machining stage has to rely on conventional portable machining or, more often, on manual grinding. Neither of these methods is adequate, especially when it comes to the special environment of the nuclear power plants. In this article, a novel design of an automatic orbital milling system intended for machining degraded welds in piping systems is presented. The system incorporates an orbital milling head designed to enable machining within the limited space, combined with a microcontroller-based control system providing full control over the geometry of the weld groove. Thus, the degraded dissimilar metal weld is removed, and simultaneously, the weld groove of desired geometry is prepared rapidly and flexibly, without the need for customized profile cutters, being the main contribution of the proposed design. The system prototype was verified by implementation in the Bohunice V2 nuclear power plant.

On-line identification using hybrid method of regularized exponential forgetting

The paper compares the ability of forgetting methods to track time varying parameters using various method of regularized exponential forgetting (REF). Three forgetting methods are analyzed in this paper: regularized exponential forgetting, second is regularized exponential forgetting with alternative covariance matrix (REFACM) and third is the novel hybrid regularized exponential forgetting method with a choice to disable or enable alternative covariance matrix (HREFACM). The comparison is performed in the terms of the quality of the observed output parameters. The observed parameters for all benchmarks are the integral sum of the Euclidean norm of the deviation of the parameter estimates from their true values (IS) and a selected band prediction error count (PE). As a supplementary information the eigenvalues of the covariance matrix are observed. All algorithms are validated by simulations in the Matlab Simulink software environment.