Active hip orthosis for assisting the training of the gait in Hemiplegics

The gait restoration is a significant component of the rehabilitation of patients with hemiplegia after central nervous system lesion. The typical symptom of the disability is the lack of hip extension during the stance phase and hip flexion during the swing phase of the affected leg; therefore, asymmetry and perturbed balance while walking. We developed a new modular orthosis for assisting hip flexion and extension during the therapeutic sessions of the gait in hemiplegic individuals based on thorough analysis of the gait characteristics of normal gait. The system is designed to fit into the powered postural controller Walkaround®. The system is developed based on the estimation of torque and power requirement for the gait at speeds up to 1.1 m/s. The model used for the simulation is a known double pendulum in the sagittal plane. The kinematics and dynamics used as the input for the simulation have been recorded in the gait laboratory with eight cameras and force platforms. The system needs to be clinically evaluated before it possibly can be turned into innovation. © 2018, University of Kragujevac, Faculty of Science

Experimental and numerical cross-correlated modal analysis of the floor structure dynamics in a thermal power plant

This article presents search methodology after the cause of excessive floor vibrations in a thermal power plant control room. The floor structure is a composition of a steel grillage and concrete slabs at 12 m level above soil. It was detected that floor vibration severity exceeds the threshold of the permitted rate. After full scale measurements are conducted on site, the results are arranged versus time and frequency domain. In parallel to site measurements a 3D modal analysis is performed in ANSYS. The outcome is a set of modal frequencies and modal shapes. Cross-correlated analytical and experimental analysis formed a true picture of the excitation, response and their mutual interaction. The obtained results and appropriate conclusions had profiled a remedy strategy to mitigate the severity of the floor vibration

Experimental and numerical cross-correlated modal analysis of the floor structure dynamics in a thermal power plant

This article presents search methodology after the cause of excessive floor vibrations in a thermal power plant control room. The floor structure is a composition of a steel grillage and concrete slabs at 12 m level above soil. It was detected that floor vibration severity exceeds the threshold of the permitted rate. After full scale measurements are conducted on site, the results are arranged versus time and frequency domain. In parallel to site measurements a 3D modal analysis is performed in ANSYS. The outcome is a set of modal frequencies and modal shapes. Cross-correlated analytical and experimental analysis formed a true picture of the excitation, response and their mutual interaction. The obtained results and appropriate conclusions had profiled a remedy strategy to mitigate the severity of the floor vibration

Casting process optimization by the regression analysis applied on the wear resistant parts molding

Provodeći sveobuhvatno istraživanje procesa lijevanja dijelova otpornih na habanje (lijevanje bijelog željeza), uspostavljena je značajna korelacija između tehnoloških parametara (temperatura, vrijeme starenja u kalupu i protok rashladnog sredstva) i tvrdoće finalnog proizvoda. Osnovna teorija Box-Wilsonove metode gradijenta činila je osnovu za predviđena istraživanja. Ta metoda definira koherentnost parametara procesa budući da je njihova disperzija u ispitivanom procesu relativno mala. Glavni je cilj eksperimenta bila definicija optimalnih uvjeta lijevanja. Stoga su identificirane različite tehnološke rute i modifikacije u procesu lijevanja dok se nije postigao najbolji rezultat. Ciljna je funkcija u početku imala oblik hipoteze, ali je kasnije dobila konzistentan oblik primjenom statističkih podataka dobivenih eksperimentom, optimizacijom procesa i upravljanjem procesom na bazi empirijske povratne veze.Conducting a comprehensive research of the casting process of wear resistant parts (white hard casting), a significant correlation is established between the technological parameters (temperature, aging time in the mold and coolant flow) and the final product hardness. The fundamental theory of Box-Wilson\u27s gradient method marked the baseline for the foreseen researches. The method defines the coherence of the process parameters, since their dispersion in the examined process is relatively small. Main target of the experiment was a definition of the optimal casting conditions. Therefore the different technological routes are identified and the casting process is modified until the best outcome is achieved. Target function was initially in a hypothesized form, while later on evolved into a consistent form due to the application of experiment-statistics, process optimization and process management based on empirical feedback

Structural Integrity Assessment by Using Cross-Correlated Modal Identification

Early researches on steel structures integrity were mainly oriented on calculations and conventional experiments. Robust numerical methods of a high accuracy are usually less reliable in estimation of dynamic properties and a true condition of a steel structure. On the other hand, experiments on real structures, being in regular operation, could be very demanding to conduct. Therefore, the implementation and justification of novel methodology in structural integrity analysis is presented here. The main idea is to correlate experimental results with those obtained applying ANSYS software package. Throughout a results cross-correlation and model adjustment the new presentation of the structure is created, involving natural frequency, modal mass, stiffness and damping. By a proper definition of those parameters, and a 3D model of the structure, a preliminary map of measuring points and measuring configuration are set in order to enable structural integrity assessment. Example of application of this procedure is given

Structural integrity assessment of welded bucket-wheel boom

Research is conducted on the causes of damage and the structural integrity assessment of the bucket-wheel boom welded lattice structures, before and after the repair of vital structures. Additionally, the paper describes the investigation conducted based on the results of non-destructive tests (visual-, magnetic particle-, dye penetrant-, and ultrasonic tests), results of tensometric measurements that refer to the stress-strain state, and results based on numerical calculation of stresses by finite element method, performed through the use of a 3D model in the software Radimpex Tower 6.0 (R). The results of tests and research performed after the repair of damaged structural welded sections show that the operational procedures are being obeyed

Structural integrity assessment of welded bucket-wheel boom

Research is conducted on the causes of damage and the structural integrity assessment of the bucket-wheel boom welded lattice structures, before and after the repair of vital structures. Additionally, the paper describes the investigation conducted based on the results of non-destructive tests (visual-, magnetic particle-, dye penetrant-, and ultrasonic tests), results of tensometric measurements that refer to the stress-strain state, and results based on numerical calculation of stresses by finite element method, performed through the use of a 3D model in the software Radimpex Tower 6.0 (R). The results of tests and research performed after the repair of damaged structural welded sections show that the operational procedures are being obeyed

Structural integrity assessment of welded bucket-wheel boom

Research is conducted on the causes of damage and the structural integrity assessment of the bucket-wheel boom welded lattice structures, before and after the repair of vital structures. Additionally, the paper describes the investigation conducted based on the results of non-destructive tests (visual-, magnetic particle-, dye penetrant-, and ultrasonic tests), results of tensometric measurements that refer to the stress-strain state, and results based on numerical calculation of stresses by finite element method, performed through the use of a 3D model in the software Radimpex Tower 6.0 (R). The results of tests and research performed after the repair of damaged structural welded sections show that the operational procedures are being obeyed

Mechatronic approach to inventing a novel kind of deformeter

Mjerenje napona i deformacija na različitim konstrukcijama povezano je s primjenom mjernih traka. Mjerni lanac koji se koristi za ovu vrstu mjerenja obično sadrži: mjerne trake, pojačivače i akvizicijsko-memorijske module. Primjenjivost ovakve instrumentacije prvenstveno zavisi od njezine osjetljivosti, mjerne ponovljivosti, točnosti i niske razine šuma. Ključni detalj ovog rada je harmonizacija mjerne karakteristike novorazvijenog deformetra s mjernim svojstvima elektroničke opreme. Vrlo slično klasičnoj metodi modeliranja mehatroničkih jedinica, novopostavljeno rješenje deformetra u obliku zatvorene petlje (CLD) optimizirano je kroz spregnuto modeliranje. Na ovaj način povezano je virtualno ispitivanje 3D modela s ispitivanjem realnog modela u laboratorijskim uvjetima. Program virtualnog eksperimenta razvijen je prema aktivnostima realnog ispitivanja na probnom stolu. Ideja o primjeni rektifikacijskog faktora za preračun naprezanja izmjerenih deformetrom uvedena je i u 3D modeliranje CLD-a. Primarni cilj ovog istraživanja bio je kreiranje novog rješenja deformetra s linearnom mjernom karakteristikom, potrebnim mjernim opsegom i dovoljnom rezolucijom mjerenja.Stress and strain measurements on frames and structures are mainly conducted by the use of strain gauges. A measuring chain applied in such measurements usually consists of strain gauges, amplifiers and data acquisition and logging device. The applicability of such instrumentation mainly depends on its sensitivity measuring repeatability, accuracy and noiseless operation. The key point of this paper is harmonization of measuring properties for the newly invented deformeter with the measuring electronics. Much alike a standard modeling of Mechatronic items, a very specific CLD (Close Loop Deformeter) is optimized throughout coupled modeling, bridging analysis of 3D virtual model and real design of laboratory prototype. Virtual experiment was developed to correspond with actual measurements on the test rig. The idea of rectification factor is introduced into concept of 3D modelling with an innovative CLD research. The focus of the research was kept on the output linearity, measuring range and resolution of the invented deformeter

Rigid body dynamics in optimization of the machine tool vibroisolation

Modern design of the machine tool treats the suspending parts as a crucial element of the effective vibration isolation. Therefore the suspending items are specifically developed and subjected to extensive tests before being applied on real objects. These elements ensure accurate levelling and appropriate vibration damping. Usually selection of inadequate support element causes intensive disturbing effects in machining. The paper presents dynamics analysis of the machine tool suspended on flexible mountings. The overall analysis is conceived on a rigid body dynamics. This method enables selection of an optimal supporting configuration. Further on such an effective suspension design prevents a need for expensive monitoring of the dynamic characteristics of the mechanical system, i.e. machine tool and supports. The paper explores dynamics of a real, flexibly supported machine tool. Results are obtained with the assistance of the "SUPPORT" software. Finally the theoretical and computational statements are approved throughout extensive site measurements on the machine tool body with appropriate instrumentation