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Vibration analysis and modelling of light-weight robot arms

Leniowski Ryszard, Wroński Michał

Vibrations in Physical Systems

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2022

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Vol. 33, nr 2

art. no. 2022220

EN

Lightweight robots (LWR) are a new generation of devices intended to be used not only for industrial tasks but also to perform actions in the human environment. This work presents an analysis of selected basic problems related to the vibration properties of light-weight robot arms. The study of vibration is based on the analysis of the root locus on the plane of complex variables. It turns out that their distribution is non-stationary and depends on the parameters of the model (arm geometry, material parameters), but also depends on the type of realised motion, which is not so obvious. Depending on the manoeuvres conducted (acceleration / deceleration), the system may lose (or increase) its oscillating properties at higher frequencies, as well as introduce a structural (measurable) delay. Recognition of the discussed properties along with their modelling is an important element of the design process of the control system of modern, light-weight robots.

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Aktywne modyfikowanie elastyczności ramion lekkich robotów

Leniowski R.

Pomiary Automatyka Robotyka

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2010

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R. 14, nr 2

645-654

PL

Lekkie roboty (LWR) są nową generacją urządzeń przeznaczonych do zastosowań przemysłowych, które zaprojektowano tak mogły wykonywać czynności w otoczeniu człowieka. Z powodu zredukowanej masy ramion są podatne na deformacje oraz charakteryzują się złożonym modelem dynamiki, co w konsekwencji zmusza do stosowania złożonych układów sterowania. Praca prezentuje cząstkowe wyniki prowadzonych badań dotyczących sterowania LWR. Opisywane są trzy metody kontrolowania sztywności ramion traktowanych jako powłoki. Wyniki badań symulacyjne ramienia wykonującego trzy ruchy obrotowe są obiecujące w kontekście przyszłych zastosowań.

EN

Light-weight robots (LWR) are a new generation of industrial appliances that was designed to operate in an unknown environment with humans. Due to reduced mass such construction might to achieve a higher elasticity in the arms and a more complex dynamic behaviour, which requires advanced control techniques in order to obtain good performances and a high accuracy. This paper presents on-going research on active control of LWR arms elasticity. The three different approaches are described and tested for 3D single robot arm, which is interpreted as a cylindrical shell. Simulation results show that the proposed concepts are promising for future applications.

3

A methodology for the design of a models set of light-weight robots components

Leniowski R.

Archives of Control Sciences

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2007

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Vol. 17, no. 3

295-310

EN

The paper gives an overview of precise mathematical modeling of light-weight robots components. Derived set of components contains dynamic models obtained with finite element method using Legendre polynomials and models of actuators (PWM power amplifiers), transmitters (harmonic drive and tooth-belt gearboxes) and sensors (PVDF, vision sensor and rotary encoder). The proposed gearboxes models taking into account such phenomena as: hysteresis, friction as well as torsional and longitudinal flexibility. The hysteresis has been modeled as weighted combination of individual Preisach cells to form a global operator. Friction model includes a lubricated contact force assuming dynamic behavior developed by Bliman and Sorine. The harmonic drive model describes the flexspline flexibility, that produces substantial transmission torsion. The original proposition assumes that the flexspline can be modeled as cylindrical shell FEM model based on 16 directional mesh. All analytical operations of process design stage have been done using the Maple symbolic language. The paper describes also the developed software which has been prepared as the dynamic library (C++/Cg) and as the s-function forms (for Matlab/Simulink). Both, the result of the theoretical analysis and the written software are used in ongoing research to develop variant of MRAC-type controllers for vibration cancelation.