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Calculation strength optimum of surgical robot effector for mechanical eigenproblems using FEM and genetic algorithm

Ilewicz Grzegorz

Vibrations in Physical Systems

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2023

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Vol. 34, nr 1

art. no. 2023106

EN

It is essential to check whether the surgical robot end effector is safe to use due to phenomena such as linear buckling and mechanical resonance. The aim of this research is to build an multi criteria optimization model based on such criteria as the first natural frequency, buckling factor and mass, with the assumption of the basic constraint in the form of a safety factor. The calculations are performed for a serial structure of surgical robot end effector with six degrees of freedom ended with a scalpel. The calculation model is obtained using the finite element method. The issue of multi-criteria optimization is solved based on the response surface method, Pareto fronts and the genetic algorithm. The results section illustrates deformations of a surgical robot end effector occurring during the resonance phenomenon and the buckling deformations for subsequent values of the buckling coefficients. The dependencies of the geometrical dimensions on the criteria are illustrated with the continuous functions of the response surface, i.e. metamodels. Pareto fronts are illustrated, based on which the genetic algorithm finds the optimal quantities of the vector function. The conducted analyzes provide a basis for selecting surgical robot end effector drive systems from the point of view of their generated inputs.

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Biomechanical criterion of dynamic stability based on ZMP formula and Flash-Hogan principle of minimum jerk

Ilewicz Grzegorz, Mrozowski Jerzy, Awrejcewicz Jan, Zagrodny Bartłomiej, Ludwicki Michał

Journal of Theoretical and Applied Mechanics

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2023

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Vol. 61 nr 1

3--9

EN

The main aim of the article is to define a criterion of dynamic stability based on the Flash- Hogan principle and the ZMP method. The gait researches were focused on analysis and observation of the human biomechanism with the optical system Optitrack. The smooth reference trajectory is defined forming a stability pattern. The optimal, due to the minimum jerk criterion, ZMP trajectory is illustrated in the results Section in order to demonstrate the dynamic stability pattern for the needs of rehabilitation in cases of neuromuscular damage or injuries affecting gait stability.

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Calculating extreme criteria of eigenvalue problems of a medical robot for soft tissue surgery using the multi-objective optimization

Ilewicz Grzegorz

Vibrations in Physical Systems

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2020

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Vol. 31, nr 3

art. no. 2020306

EN

Medical robots with an instant center of rotation mechanism in a trocar are used for operating a human body or servicing artificial organs. The result of the work is the development of a multi-criteria optimization model of a discussed medical robot, considering safety factor, first eigenfrequency and buckling coefficient as a criteria. The article also analyzes two issues of mechanics, the natural frequency and linear buckling. A discrete mesh model of a novel robot design with ten degrees of freedom and ended with a scalpel was developed based on finite element method. For the given loads and supports, a multi-criteria optimization model was evolved, which was solved by using the response surface method and the multi-objective genetic algorithm. The results section shows the Pareto fronts for the criteria and geometrical dimensions of the kinematic chain. The courses of resonant vibrations and buckling strains were also characterized. The solved optimization model gives correct values for the adopted criteria. The values of resonance were defined, which makes it possible to select mechatronic drive systems in terms of the input they generate. Variability of the resonant vibrations phenomena, as well as shapes and directions of buckling, provide information about the displacements taking place in the medical robot system.