TRANSITION FROM MEASUREMENTS TO 3D AND 1D COMBUSTION SIMULATIONS FOR A DI DIESEL ENGINE

Zgorevanje v dizelskih motorjih je mogoče simulirati s pomočjo programske opreme, ki je danes na trgu že zelo razširjena. Vedno bo ostajalo število neraziskanih področij, ki se odkrivajo ob vpeljavi teh simulacijskih orodij. V tej nalogi sem na podlagi meritev in 3D, Fire simulacij sestavil 1D, Boost simulacijski model DI-dizelskega motorja z MCC-modelom zgorevanja, ki sem ga nato nastavil/umeril in rezultate primerjal z meritvami. Ujemanje je pokazalo, da je izbrana metoda dobra in da so simulacijski prijemi sposobni napovedovati trende obnašanja motorjev pri različnih obratovalnih pogojih. V prihodnosti je mogoče naredi še veliko, da se 1D- in 3D-simulacije zgorevanja dodatno zbližajo.Combustion in diesel engines can be simulated with the assistance of modern software that is wide spread on the market nowadays. There will always be a wide uncertain field which can be uncovered with implementation of these tools. In the presented diploma work I have constructed a 1D Boost model of a DI diesel engine with usage and calibration of MCC combustion model, based on measurement results and an available 3D Fire model. Analysis of the results showed that calibration method was successful and simulation tools are capable to predict engine behavior at different operating points. In the future, additional work can bring 1D and 3D combustion simulations even closer together

INFLUENCE OF STATIC, KINEMATIC AND DYNAMIC FACTORS ON THE ACCURACY OF ROBOTIC MACHINING

Doktorska disertacija se ukvarja z razvojem metodologije za določanje natančnosti obdelave z uporabo robota. Zaradi prilagodljivosti so industrijski roboti lahko alternativa namenskim strojem, posebej kadar gre za velike obdelovance ali obdelavo netipičnih ali mehkejših materialov. Težava je, da proizvajalci za industrijske robote natančnost robota po celotnem delovnem prostoru podajajo preveč ohlapno. V doktorski disertaciji smo predstavili pristop, ki omogoča določitev statičnih, kinematičnih in dinamičnih lastnosti robota z uporabo analitičnih, numeričnih in eksperimentalnih metod. Analitične metode smo uporabili za določitev gibljivosti in vztrajnosti robota, numerične metode za določitev strukturne togosti in eksperimentalne metode za določitev dušenja in prisotnosti resonančnega stanja sistema ter za kalibracijo numeričnega modela za določitev strukturne togosti robota. S polinomsko regresijo smo vzpostavili nadomestne modele, ki posamezno lastnost povežejo s pozo robota. Poze robota za izdelavo reprezentativnih izdelkov smo poiskali s pomočjo statističnih in nedeterminističnih metod. Izbrali smo Taguchi zasnovo eksperimenta, ki pri obvladljivem obsegu meritev najbolje zadosti pogoju pravokotnosti in omogoča, da se posamezna lastnost robota izrazi neodvisno od drugih. Meje eksperimenta smo določili z večkriterijskim dvojnim genetskim algoritmom z uteženimi ciljnimi kriteriji. Eksperimente rezkanja z robotom smo izvedli v prilagojeni celici. Na podlagi CMM-meritev kakovostnih kriterijev izdelkov smo določili vpliv gibljivosti, strukturne togosti, dušenja, vztrajnosti in prisotnosti resonančnega stanja na natančnost obdelave z robotom. Za kakovostne kriterije smo uporabili ploskost izdelane površine, najmanjši, srednji in največji premer izdelane luknje na treh nivojih ter krožnost, valjnost in ravnost srednjice luknje. Ugotovili smo, da je znotraj eksperimentalno opisanega področja natančnost obdelave z robotom odvisna od vseh obravnavanih dejavnikov.The doctoral dissertation deals with the development of a methodology for determining the accuracy of robotic machining. Due to their adaptability, industrial robots can be an alternative to specialized machines, especially when dealing with large workpieces or machining atypical or softer materials. The problem is that for industrial robots, manufacturers give robot accuracy throughout the workspace very loose. In the doctoral dissertation, we proposed an approach that allows the static, kinematic and dynamic properties of a robot to be determined by the use of analytical, numerical and experimental methods. Analytical methods were used to determine the manipulability and inertia of the robot, numerical methods were used to determine the structural stiffness, while experimental methods were used to determine damping and presence of the resonant state and to perform calibration of the numerical model for structural stiffness of the robot. With polynomial regression, we have established surrogate models that associate an individual property with the robot posture. Using statistical and non-deterministic methods, we searched for the relevant poses of the robot to machine a set of representative products. We chose the Taguchi experimental design, which in a manageable range of measurements best suits the orthogonality condition and allows an individual property of the robot to be expressed independently of the others. A multi-criteria dual genetic algorithm with weighted target criteria was used to determine the limits of the experiment. Robotic machining experiments were performed in a custom cell. Based on CMM measurements of product quality criteria, we determined the influence of manipulability, structural stiffness, damping, inertia, and the presence of a resonant state on the accuracy of robotic machining. For the quality criteria, we used sixteen different geometrical and dimensional part properties. We found that within the experimentally described region, the robotic machining accuracy depends on all the considered factors

Industrial Robot Programming

Učbenik zajema osnove programiranja, pravilne izbire industrijskih robotov, postavitve, zagon, prve nastavitve, nastavitve koordinatnega sistema orodja, obdelovancev, uporaba odločitvenih vej, ponovitvenih zank, prekinitvenih rutin, serijske komunikacije z uporabo PROFINET protokola ter podaja smernice za varno vračanje robota v izhodiščno točko. Prav tako podaja smernice za pripravo robota za operaterja.The textbook covers the basics of programming, correct selection of industrial robots, layout, start-up, initial settings, tool coordinate system settings, workpieces, use of decision branches, repeating loops, interrupt routines, serial communication using PROFINET protocol and provides guidelines for safe return of robot to starting point. It also provides guidelines for preparing a robot for the operator

Stiffness-Based Cell Setup Optimization for Robotic Deburring with a Rotary Table

Deburring is recognized as an ideal technology for robotic automation. However, since the low stiffness of the robot can affect the deburring quality and the performance of an industrial robot is generally inhomogeneous over its workspace, a cell setup must be found that allows the robot to track the toolpath with the desired performance. In this work, the problems of robotic deburring are addressed by integrating components commonly used in the machining industry. A rotary table is integrated with the robotic deburring cell to increase the effective reach of the robot and enable it to machine a large workpiece. A genetic algorithm (GA) is used to optimize the placement of the workpiece based on the stiffness of the robot, and a local minimizer is used to maximize the stiffness of the robot along the deburring toolpath. During cutting motions, small table rotations are allowed so that the robot maintains high stiffness, and during non-cutting motions, large table rotations are allowed to reposition the workpiece. The stiffness of the robot is modeled by an artificial neural network (ANN). The results confirm the need to optimize the cell setup, since many optimizers cannot track the toolpath, while for the successful optimizers, a performance imbalance occurs along the toolpath

Using a Fully Fractional Generalised Maxwell Model for Describing the Time Dependent Sinusoidal Creep of a Dielectric Elastomer Actuator

Actuators made of dielectric elastomers are used in soft robotics for a variety of applications. However, due to their mechanical properties, they exhibit viscoelastic behaviour, especially in the initial phase of their performance, which can be observed in the first cycles of dynamic excitation. A fully fractional generalised Maxwell model was derived and used for the first time to capture the viscoelastic effect of dielectric elastomer actuators. The Laplace transform was used to derive the fully fractional generalised Maxwell model. The Laplace transform has proven to be very useful and practical in deriving fractional viscoelastic constitutive models. Using the global optimisation procedure called Pattern Search, the optimal parameters, as well as the number of branches of the fully fractional generalised Maxwell model, were derived from the experimental results. For the fully fractional generalised Maxwell model, the optimal number of branches was determined considering the derivation order of each element of the branch. The derived model can readily be implemented in the simulation of a dielectric elastomer actuator control, and can also easily be used for different viscoelastic materials

Using a Fully Fractional Generalised Maxwell Model for Describing the Time Dependent Sinusoidal Creep of a Dielectric Elastomer Actuator

Actuators made of dielectric elastomers are used in soft robotics for a variety of applications. However, due to their mechanical properties, they exhibit viscoelastic behaviour, especially in the initial phase of their performance, which can be observed in the first cycles of dynamic excitation. A fully fractional generalised Maxwell model was derived and used for the first time to capture the viscoelastic effect of dielectric elastomer actuators. The Laplace transform was used to derive the fully fractional generalised Maxwell model. The Laplace transform has proven to be very useful and practical in deriving fractional viscoelastic constitutive models. Using the global optimisation procedure called Pattern Search, the optimal parameters, as well as the number of branches of the fully fractional generalised Maxwell model, were derived from the experimental results. For the fully fractional generalised Maxwell model, the optimal number of branches was determined considering the derivation order of each element of the branch. The derived model can readily be implemented in the simulation of a dielectric elastomer actuator control, and can also easily be used for different viscoelastic materials

A Holistic Approach to Cooling System Selection and Injection Molding Process Optimization Based on Non-Dominated Sorting

This study applied a holistic approach to the problem of controlling the temperature of critical areas of tools using conformal cooling. The entire injection molding process is evaluated at the tool design stage using four criteria, one from each stage of the process cycle, to produce a tool with effective cooling that enables short cycle times and ensures good product quality. Tool manufacturing time and cost, as well as tool life, are considered in the optimization by introducing a novel tool-efficiency index. The multi-objective optimization is based on numerical simulations. The simulation results show that conformal cooling effectively cools the critical area of the tool and provides the shortest cycle times and the lowest warpage, but this comes with a trade-off in the tool-efficiency index. By using the tool-efficiency index with non-dominated sorting, the number of relevant simulation cases could be reduced to six, which greatly simplifies the decision regarding the choice of cooling system and process parameters. Based on the study, a tool with conformal cooling channels was made, and a coolant inlet temperature of 20 °C and a flow rate of 5 L/min for conformal and 7.5–9.5 L/min for conventional cooling channels were selected for production. The simulation results were validated by experimental measurements