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Sasa Zelenika

University of Rijeka, Faculty of Engineering & Centre for Micro- and Nanosciences and Technologies, Faculty Member

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Full Prof. in Mechanical Engineering with expertise in precision engineering (especially compliant mechanisms, ultra-high precision positioning, structural analysis, integration into mechatronics devices, measurement techniques, equipment for synchrotron radiation) and microsystems technologies (MEMS, handling, assembly and packaging, scaling effects, micro-fabrication, energy harvesting, tribology).

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University of Rijeka

Università degli Studi di Udine / University of Udine

University of Dhaka, Bangladesh

University of Rijeka

Milan Růžička

Vitalii Yanovych

University Politehnica of Bucharest

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Papers by Sasa Zelenika

Miniaturized wearable broadband energy harvesters

Nonlinear numerical modelling and experimental validation of multilayer piezoelectric vibration energy scavengers

Proceedings of SPIE, May 21, 2015

Parasitic Motion of Cross-Spring Pivots: Theoretical Analysis and Experimental Assessment

Methodological correlation of finite element models to nanoindentation measurements on Si (100)

Issues in the mechatronics design of a full arm rehabilitation device

Traditional therapy for the recovery of patients with arm impairments involves physical therapist... more Traditional therapy for the recovery of patients with arm impairments involves physical therapists that control the (mainly repetitive) rehabilitative movements of the patients and help them recover the (hopefully full) motion ability of the arm. The limited number of physiotherapists, as well as their limited time availability to be spent with each patient, constitute in this frame an increasing problem. The goal of this study is to ideate, develop and design a full arm rehabilitation mechatronics device that will enable a fast and reliable recovery of patients’ motion ability. Moreover, the device should provide the patients with the possibility to use it rather autonomously so that each physiotherapist could ideally be concurrently in charge of at least three patients. In this frame, preliminary results of the critical evaluation of the solutions available on the market are presented in this work. Especially relevant is here the consideration of the needed number and arrangement (distribution) of the degrees of freedom (DOFs) and their benefit-to-price ratio. A crucial part of this evaluation is the study of the kinematics of the movement of the whole arm in the natural (unconstrained) state. Considerations about the usable actuators and sensors complement the performed evaluation. In fact, the actuators should provide the needed help to the patients while performing the motions otherwise not achievable by their own, while the sensors should hence provide the needed feedback to the used control system so as the optimize the level of help when the degree of autonomy that the patients can accomplish by themselves is reached. The computing part controlling the performances of the device, complemented ideally with a virtual reality (VR) users’ interface, follows thus patients’ improvements and stimulates them to make full use of their efforts while assuring the safe usage of the whole device.

Characterization of cross-spring pivots for micropositioning applications

Proceedings of SPIE, May 21, 2015

Compliant mechanisms gain at least part of their mobility from the deflection of flexible member.... more Compliant mechanisms gain at least part of their mobility from the deflection of flexible member. They are characterised by high precision, as well as no backlash and wear. Several analytical and numerical methods are used in this work to characterise the behaviour of compliant rotational mechanisms, known as cross-spring pivots, aimed at micropositioning applications. When ultra-high precision is required, the limits of applicability of approximated calculation algorithms have to be determined. The results obtained by employing these methods are thus compared with results obtained by using nonlinear finite element calculations tuned with experimental data reported in literature. The finite element model allows also considering the influence of lateral loads and of non-symmetrical pivot configurations where the angle or point of intersection of the leaf springs, or even the initial curvature of the springs, can be varied. The aim of this part of the work is to determine the influence of the cited design parameters on the minimisation of the parasitic shifts of the geometric centre of the pivot as well as on the minimisation of the variability of the rotational stiffness of the pivot so as to ensure its stability. The obtained results allow therefore determining design solutions applicable in ultra-high precision micropositioning applications, e.g. in the field of production or of handling and assembly of MEMS.

Mechanical aspects of the design of third-generation synchrotron-light sources

In storage rings of third-generation synchrotron radiation facilities, the positioning tolerances... more In storage rings of third-generation synchrotron radiation facilities, the positioning tolerances of the elements of the machine are constantly reduced to achieve lower emittance and increased lifetime. This implies increasing positioning and alignment precision that must be preserved over long timespans. The mechanical engineering approach to meet these requirements is described. The design of the Swiss Light Source storage ring support, positioning and position monitoring systems, the tests done on the respective prototypes, the quality assurance and installation procedures, and the operational experience with these systems are discussed in depth. The applicability of the developed arrangement to beam-based alignment is also illustrated.

Design of Compliant Micromechanisms

A broad overview of the topics related to the mechanical design of compliant micromechanisms is p... more A broad overview of the topics related to the mechanical design of compliant micromechanisms is presented. Design methodologies to be used in the design of devices based on leaf springs, flexural notches and continuum structures with distributed compliance are given, and a critical presentation of the peculiarities of these solutions is provided. The extensive bibliographical list is given as means to extend further the study to details of each of the treated topics.

Characterisation of the dynamical behaviour of a power transformer’s tank

Forearm and Wrist Active Rehabilitation Device

The In-Vacuum Flexural Hinge Based Dynamic Mirror Bender for the Protein Crystallography Beamline

One of the key features of the SLS Protein Crystallography Beamline will be the dynamic focusing ... more One of the key features of the SLS Protein Crystallography Beamline will be the dynamic focusing adaptability of the photon beam to the various experimental set-ups. In this work are described the modifications done to an already existing mirror bender mechanism in order to make it suited to meet these requirements. The numerical evaluation of the resulting mechanical arrangement shows its full applicability in the desired working range.

Ultra-High Precision Gimbal-Mount for Optical Elements

This work presents an innovative design of a high precision rotational device in a gimbal-mount c... more This work presents an innovative design of a high precision rotational device in a gimbal-mount configuration. The device is characterised by manufacturing simplicity as well as with compatibility with severe environmental conditions. It is moreover based on compliant elements, thus allowing the mechanical non-linearities present in the current off-the-shelf solutions to be avoided. The experimental validation of its performances has allowed establishing that accuracies in the sub micro-radian range can be achieved.

Acceptance Tests of the Mirror Bender for the Protein Crystallography Beamline

Sažetak: Results of the mechanical and metrological acceptance tests of the mirror bender for the... more

Strategija Tehničkog Fakulteta Sveučilišta U Rijeci Za Razdoblje Od 2007. – 2013. Godine

Performance evaluation of the energy harvester

Klasifikacija znanosti u fokusu metodologije i tehnologije znanstvenoga istraživanja

Pomorski zbornik, May 11, 2006

This scientific paper has proven the following basic scientific hypothesis: scientific findings r... more This scientific paper has proven the following basic scientific hypothesis: scientific findings regarding science classification, methodology and technology of scientific research represent conditio sine qua non while creating, designing and conducting the scientific research process, formulating research results and writing scientific and scientific-specialized and professional papers. Following the presentation of most important characteristics regarding science, classification of science, methodology and technology of scientific research is being elaborated, the paper further explores, scientifically analyzes and evaluates newest Croatian scientific classifications (2005.). Special attention has been paid to interaction of scientific classification, methodology and technology of scientific research, disciplinary and multidisciplinary scientific research. Specially indicative results are being observed in area of revolving the scientific classification, methodology and technology of scientific research in 21 st century as well as results regarding fifth technological revolution that will take place in next century.

Hand model with dependency constrained joints for applications in rehabilitation robotics

Medicina Fluminensis, Dec 1, 2022

Aim: This work presents a method for developing a simplified but efficient model of the complex h... more Aim: This work presents a method for developing a simplified but efficient model of the complex human hand kinematics with the aim of its implementation in rehabilitation robotics. Material and methods: The approach incorporates modularity by simplifying the available model comprising 24 degrees of freedom (DOFs) to 9 DOFs, with the introduction of additional joint coupling parameters specific to different grasp types. The effect of dependent joints to the ranges-of-motion (ROMs) of the model is investigated and compared to the anatomical one. The index, middle, ring and little finger solutions to forward and inverse kinematics problems are then acquired. The implementation of the model, based on the median male bones dimensions, is made available in the open-source Robot Operating System (ROS) framework. Results: By including additional four inclination angles per finger, the devised kinematic hand model encompasses also finger curvatures, resulting in significant positioning accuracy improvements compared to the conventional model. The used 3D spatial position improvement metrics are the mean absolute (MAE) and mean relative errors (MRE). The dependent joint position MAEs range from 0.22 to 0.34 cm, while MREs range from 2.8 and 3.5 %, whereas the highest absolute and relative errors during fingertip positioning can reach 0.5 cm and 10.5 %, respectively. Conclusion: The performed investigation allowed establishing that by modelling finger curvature and assuring the adaptability of the model to a variety of human hands and rehabilitation modalities through joint dependency, represents the best approach towards a relatively simple and applicable rehabilitation model with functional human-like hand movements.

Optimized cross-spring pivot configurations with minimized parasitic shifts and stiffness variations investigated via nonlinear FEA

Mechanics Based Design of Structures and Machines, Sep 3, 2016

Compliant mechanisms are nowadays a well-established means of achieving ultra-high precision, alb... more Compliant mechanisms are nowadays a well-established means of achieving ultra-high precision, albeit at the expense of complex kinematics with the presence of parasitic motions. Diverse design configurations of compliant rotational joints called cross-spring pivots are hence studied in this work by applying various analytical and numerical approaches. Depending on the required precision and loading conditions, the limits of applicability of the available analysis tools, validated with nonlinear finite element calculations tuned with experimental data reported in literature, are established. The variation of design parameters allows, in turn, establishing design configurations of the studied mechanism that allow attaining minimised parasitic shifts and slight variations of its rotational stiffness, even when a broad range of rotations and varying transversal loads are considered, creating thus the preconditions for their application in high-precision micropositioning applications.

Structured open-source procedure for the design and validation of an arm rehabilitation device

Investigation of friction force trends at the nanoscale using computation approach

Miniaturized wearable broadband energy harvesters

Nonlinear numerical modelling and experimental validation of multilayer piezoelectric vibration energy scavengers

Proceedings of SPIE, May 21, 2015

Parasitic Motion of Cross-Spring Pivots: Theoretical Analysis and Experimental Assessment

Methodological correlation of finite element models to nanoindentation measurements on Si (100)

Issues in the mechatronics design of a full arm rehabilitation device

Traditional therapy for the recovery of patients with arm impairments involves physical therapist... more Traditional therapy for the recovery of patients with arm impairments involves physical therapists that control the (mainly repetitive) rehabilitative movements of the patients and help them recover the (hopefully full) motion ability of the arm. The limited number of physiotherapists, as well as their limited time availability to be spent with each patient, constitute in this frame an increasing problem. The goal of this study is to ideate, develop and design a full arm rehabilitation mechatronics device that will enable a fast and reliable recovery of patients’ motion ability. Moreover, the device should provide the patients with the possibility to use it rather autonomously so that each physiotherapist could ideally be concurrently in charge of at least three patients. In this frame, preliminary results of the critical evaluation of the solutions available on the market are presented in this work. Especially relevant is here the consideration of the needed number and arrangement (distribution) of the degrees of freedom (DOFs) and their benefit-to-price ratio. A crucial part of this evaluation is the study of the kinematics of the movement of the whole arm in the natural (unconstrained) state. Considerations about the usable actuators and sensors complement the performed evaluation. In fact, the actuators should provide the needed help to the patients while performing the motions otherwise not achievable by their own, while the sensors should hence provide the needed feedback to the used control system so as the optimize the level of help when the degree of autonomy that the patients can accomplish by themselves is reached. The computing part controlling the performances of the device, complemented ideally with a virtual reality (VR) users’ interface, follows thus patients’ improvements and stimulates them to make full use of their efforts while assuring the safe usage of the whole device.

Characterization of cross-spring pivots for micropositioning applications

Proceedings of SPIE, May 21, 2015

Compliant mechanisms gain at least part of their mobility from the deflection of flexible member.... more Compliant mechanisms gain at least part of their mobility from the deflection of flexible member. They are characterised by high precision, as well as no backlash and wear. Several analytical and numerical methods are used in this work to characterise the behaviour of compliant rotational mechanisms, known as cross-spring pivots, aimed at micropositioning applications. When ultra-high precision is required, the limits of applicability of approximated calculation algorithms have to be determined. The results obtained by employing these methods are thus compared with results obtained by using nonlinear finite element calculations tuned with experimental data reported in literature. The finite element model allows also considering the influence of lateral loads and of non-symmetrical pivot configurations where the angle or point of intersection of the leaf springs, or even the initial curvature of the springs, can be varied. The aim of this part of the work is to determine the influence of the cited design parameters on the minimisation of the parasitic shifts of the geometric centre of the pivot as well as on the minimisation of the variability of the rotational stiffness of the pivot so as to ensure its stability. The obtained results allow therefore determining design solutions applicable in ultra-high precision micropositioning applications, e.g. in the field of production or of handling and assembly of MEMS.

Mechanical aspects of the design of third-generation synchrotron-light sources

In storage rings of third-generation synchrotron radiation facilities, the positioning tolerances... more In storage rings of third-generation synchrotron radiation facilities, the positioning tolerances of the elements of the machine are constantly reduced to achieve lower emittance and increased lifetime. This implies increasing positioning and alignment precision that must be preserved over long timespans. The mechanical engineering approach to meet these requirements is described. The design of the Swiss Light Source storage ring support, positioning and position monitoring systems, the tests done on the respective prototypes, the quality assurance and installation procedures, and the operational experience with these systems are discussed in depth. The applicability of the developed arrangement to beam-based alignment is also illustrated.

Design of Compliant Micromechanisms

A broad overview of the topics related to the mechanical design of compliant micromechanisms is p... more A broad overview of the topics related to the mechanical design of compliant micromechanisms is presented. Design methodologies to be used in the design of devices based on leaf springs, flexural notches and continuum structures with distributed compliance are given, and a critical presentation of the peculiarities of these solutions is provided. The extensive bibliographical list is given as means to extend further the study to details of each of the treated topics.

Characterisation of the dynamical behaviour of a power transformer’s tank

Forearm and Wrist Active Rehabilitation Device

The In-Vacuum Flexural Hinge Based Dynamic Mirror Bender for the Protein Crystallography Beamline

One of the key features of the SLS Protein Crystallography Beamline will be the dynamic focusing ... more One of the key features of the SLS Protein Crystallography Beamline will be the dynamic focusing adaptability of the photon beam to the various experimental set-ups. In this work are described the modifications done to an already existing mirror bender mechanism in order to make it suited to meet these requirements. The numerical evaluation of the resulting mechanical arrangement shows its full applicability in the desired working range.

Ultra-High Precision Gimbal-Mount for Optical Elements

This work presents an innovative design of a high precision rotational device in a gimbal-mount c... more This work presents an innovative design of a high precision rotational device in a gimbal-mount configuration. The device is characterised by manufacturing simplicity as well as with compatibility with severe environmental conditions. It is moreover based on compliant elements, thus allowing the mechanical non-linearities present in the current off-the-shelf solutions to be avoided. The experimental validation of its performances has allowed establishing that accuracies in the sub micro-radian range can be achieved.

Acceptance Tests of the Mirror Bender for the Protein Crystallography Beamline

Sažetak: Results of the mechanical and metrological acceptance tests of the mirror bender for the... more

Strategija Tehničkog Fakulteta Sveučilišta U Rijeci Za Razdoblje Od 2007. – 2013. Godine

Performance evaluation of the energy harvester

Klasifikacija znanosti u fokusu metodologije i tehnologije znanstvenoga istraživanja

Pomorski zbornik, May 11, 2006

This scientific paper has proven the following basic scientific hypothesis: scientific findings r... more This scientific paper has proven the following basic scientific hypothesis: scientific findings regarding science classification, methodology and technology of scientific research represent conditio sine qua non while creating, designing and conducting the scientific research process, formulating research results and writing scientific and scientific-specialized and professional papers. Following the presentation of most important characteristics regarding science, classification of science, methodology and technology of scientific research is being elaborated, the paper further explores, scientifically analyzes and evaluates newest Croatian scientific classifications (2005.). Special attention has been paid to interaction of scientific classification, methodology and technology of scientific research, disciplinary and multidisciplinary scientific research. Specially indicative results are being observed in area of revolving the scientific classification, methodology and technology of scientific research in 21 st century as well as results regarding fifth technological revolution that will take place in next century.

Hand model with dependency constrained joints for applications in rehabilitation robotics

Medicina Fluminensis, Dec 1, 2022

Aim: This work presents a method for developing a simplified but efficient model of the complex h... more Aim: This work presents a method for developing a simplified but efficient model of the complex human hand kinematics with the aim of its implementation in rehabilitation robotics. Material and methods: The approach incorporates modularity by simplifying the available model comprising 24 degrees of freedom (DOFs) to 9 DOFs, with the introduction of additional joint coupling parameters specific to different grasp types. The effect of dependent joints to the ranges-of-motion (ROMs) of the model is investigated and compared to the anatomical one. The index, middle, ring and little finger solutions to forward and inverse kinematics problems are then acquired. The implementation of the model, based on the median male bones dimensions, is made available in the open-source Robot Operating System (ROS) framework. Results: By including additional four inclination angles per finger, the devised kinematic hand model encompasses also finger curvatures, resulting in significant positioning accuracy improvements compared to the conventional model. The used 3D spatial position improvement metrics are the mean absolute (MAE) and mean relative errors (MRE). The dependent joint position MAEs range from 0.22 to 0.34 cm, while MREs range from 2.8 and 3.5 %, whereas the highest absolute and relative errors during fingertip positioning can reach 0.5 cm and 10.5 %, respectively. Conclusion: The performed investigation allowed establishing that by modelling finger curvature and assuring the adaptability of the model to a variety of human hands and rehabilitation modalities through joint dependency, represents the best approach towards a relatively simple and applicable rehabilitation model with functional human-like hand movements.

Optimized cross-spring pivot configurations with minimized parasitic shifts and stiffness variations investigated via nonlinear FEA

Mechanics Based Design of Structures and Machines, Sep 3, 2016

Compliant mechanisms are nowadays a well-established means of achieving ultra-high precision, alb... more Compliant mechanisms are nowadays a well-established means of achieving ultra-high precision, albeit at the expense of complex kinematics with the presence of parasitic motions. Diverse design configurations of compliant rotational joints called cross-spring pivots are hence studied in this work by applying various analytical and numerical approaches. Depending on the required precision and loading conditions, the limits of applicability of the available analysis tools, validated with nonlinear finite element calculations tuned with experimental data reported in literature, are established. The variation of design parameters allows, in turn, establishing design configurations of the studied mechanism that allow attaining minimised parasitic shifts and slight variations of its rotational stiffness, even when a broad range of rotations and varying transversal loads are considered, creating thus the preconditions for their application in high-precision micropositioning applications.

Structured open-source procedure for the design and validation of an arm rehabilitation device

Investigation of friction force trends at the nanoscale using computation approach