<p>Flextronics Design i Linköping, som ingår i den stora amerikanskägda Flextronics- koncernen, är en industrialiseringsenhet på mobiltelefonsidan. Det innebär att verksamheten kretsar kring att ta fram test- och monteringsprocesser, samt tillhörande utrustning, som sedan implementeras hos högvolymsfabrikerna belägna i olika låg-kostnads-länder.</p><p>På mobiltelefonerna finns, beroende på modell, ett antal detaljer som pressas fast, antingen för hand, med en manuell press, eller med hjälp av en pneumatisk press. Den sistnämnda pressmetoden används när det rör sig om lite längre presstider på detaljen, från ett par sekunder och uppåt. Idag finns det två modeller som drivs med tryckluft och som pressar med olika kraftintervall beroende på vilket lufttryck som tillförs till systemet. Det har visat sig att det finns ett behov hos företaget att ta fram en ny konstruktion som pressar med ett lägre kraftintervall än de befintliga modellerna kan erbjuda. Det är önskvärt att reducera tillverkningskostnaden jämfört med tidigare modeller. Framförallt är en ny lösning på xy-bordet önskvärd då den står för en stor del av den totala kostnaden. För att tryckbilden, och därmed resultatet, ska bli så bra som möjligt är det också viktigt att konstruktionen går att kalibrera i x- och y-led, samt att även felaktigheter i planheten går att justera.</p><p>Under konstruktionsarbetet har olika tekniska lösningar och koncept tagits fram som utvärderats. Den slutliga konstruktionen består av en tryckluftscylinder som är dimensionerad för att trycka med de krafter som är specificerade. Den rörliga delen av cylindern förs ner och pressar samman detaljen och telefonen som är placerade i en fixtur. Den är i sin tur fixerad i ett justerbart xy-bord som består av två aluminiumplattor med urfrästa spår. Inställningen av tryckbilden i x- och y-led sker med hjälp av styrpinnar. Eventuella skillnader i planheten verifieras redan vid monteringen av pressen, och justeras genom skimsning.</p><p>Tillverkningskostnaden för den nya modellen har reducerats med 30 % jämfört med de tidigare pressarna. Konceptlösningen på det nya xy-bordet innebär en kostnadsminskning med 50 % mot det befintliga bordet.</p>

<p>In this master thesis a robot arm belonging to an automatic milking machine from DeLaval is investigated. The robot arm is controlled by a pneumatic cylinder and a valve. The goal of the master thesis is to investigate instability problems and to find out if it is possible to solve them by using gain scheduling. Gain scheduling is a type of controller where the parameters of the controller are changed during operation, for example depending on the working point. First a nonlinear mathematical model of the system was made. Then a test rig was built with a robot arm and sensors, identical to the ones mounted on the real machine from DeLaval. The different parameters of the nonlinear model were then tuned and validated against data from the test rig to make sure that the model is correct. After that the nonlinear model was linearized for a closer analysis of the parameters that seemed to have an apparent effect on the system behaviour. The result of the analysis showed that the probable cause of instability is a decrease of the viscous friction, which gives worse damping characteristics. It was more suitable to base the controller parameters on the valve opening instead of the working point for the robot arm, since the gain in the valve increases with increasing valve opening. To avoid deterioration in phase margin because of the increased gain, the controller is adjusted so that the total gain is the same regardless of valve opening. The result is a system with larger bandwidth, less sensitive to changes in the viscous friction.</p>

The present work investigates, numerically, the process of melting and solidification in hollow vertical cylinders, filled with air and phase change material (PCM). The PCM used is sodium nitrate, which expands upon melting. Therefore, a void must be present within the cylinder, which is filled with air. The influence of cylinder shape on melting time is determined. The numerical model takes both conductive and convective heat transfer into account during the melting process. The Volume-of-Fluid (VOF) model is used to track the interface between the PCM and air as the PCM melts. Three dimensionless numbers represent the characteristics of the problem, which are the Grashof, Stefan, and Prandtl numbers. The Stefan and Prandtl numbers are held constant, while the Grashof number varies. Inner Aspect Ratio (AR) is used to characterize the shape of the cylinder, which is defined as the ratio of the height to the diameter of the vertical cylinder. In this study, a range of AR values from 0.23 to 10 is investigated. Cylinders with small AR, corresponding to high Grashof numbers, lead to lower melting times compared with cylinders with high AR. The molten PCM velocity was also influenced greatly by this difference between solid PCM shape between high and low AR cases. Cylinders with small AR, corresponding to high Grashof numbers, lead to higher solidification times compared with cylinders with high AR. It was found that the velocity decreased during the solidification process, but the shape of the cylinder had an effect on the decrease. Natural convection velocity was found to decrease during the solidification process and, therefore, its effects diminish as solidification proceeds.

Flextronics Design i Linköping, som ingår i den stora amerikanskägda Flextronics- koncernen, är en industrialiseringsenhet på mobiltelefonsidan. Det innebär att verksamheten kretsar kring att ta fram test- och monteringsprocesser, samt tillhörande utrustning, som sedan implementeras hos högvolymsfabrikerna belägna i olika låg-kostnads-länder. På mobiltelefonerna finns, beroende på modell, ett antal detaljer som pressas fast, antingen för hand, med en manuell press, eller med hjälp av en pneumatisk press. Den sistnämnda pressmetoden används när det rör sig om lite längre presstider på detaljen, från ett par sekunder och uppåt. Idag finns det två modeller som drivs med tryckluft och som pressar med olika kraftintervall beroende på vilket lufttryck som tillförs till systemet. Det har visat sig att det finns ett behov hos företaget att ta fram en ny konstruktion som pressar med ett lägre kraftintervall än de befintliga modellerna kan erbjuda. Det är önskvärt att reducera tillverkningskostnaden jämfört med tidigare modeller. Framförallt är en ny lösning på xy-bordet önskvärd då den står för en stor del av den totala kostnaden. För att tryckbilden, och därmed resultatet, ska bli så bra som möjligt är det också viktigt att konstruktionen går att kalibrera i x- och y-led, samt att även felaktigheter i planheten går att justera. Under konstruktionsarbetet har olika tekniska lösningar och koncept tagits fram som utvärderats. Den slutliga konstruktionen består av en tryckluftscylinder som är dimensionerad för att trycka med de krafter som är specificerade. Den rörliga delen av cylindern förs ner och pressar samman detaljen och telefonen som är placerade i en fixtur. Den är i sin tur fixerad i ett justerbart xy-bord som består av två aluminiumplattor med urfrästa spår. Inställningen av tryckbilden i x- och y-led sker med hjälp av styrpinnar. Eventuella skillnader i planheten verifieras redan vid monteringen av pressen, och justeras genom skimsning. Tillverkningskostnaden för den nya modellen har reducerats med 30 % jämfört med de tidigare pressarna. Konceptlösningen på det nya xy-bordet innebär en kostnadsminskning med 50 % mot det befintliga bordet.

This thesis reports on measurements of drag on an unbounded cylinder in a viscoelastic Stokes flow, and compares these values with a Newtonian equivalent. Cylinders of diameter 0.5 to 3.34 mm were submerged 10 to 36 mm into slowly rotating annular tanks with channel widths between 133 to 152 mm. Theoretical formulas and computer simulations were used to correct for the effects of ends and walls, yielding estimates of the unbounded drag. The methodology was verified by testing Newtonian fluids and comparing the results to Kaplun’s (1957) prediction for unbounded drag. The test fluids used were a silicone oil, a polybutene, and two Boger fluids. By comparing the Boger fluid results to equally viscous Newtonian results, the contributions of elasticity to the drag were determined. The Deborah number (De) was used to represent the magnitude of flow elasticity, and an onset of elastic effects was measured between 0.5 and 0.7.

This thesis reports on measurements of drag on an unbounded cylinder in a viscoelastic Stokes flow, and compares these values with a Newtonian equivalent. Cylinders of diameter 0.5 to 3.34 mm were submerged 10 to 36 mm into slowly rotating annular tanks with channel widths between 133 to 152 mm. Theoretical formulas and computer simulations were used to correct for the effects of ends and walls, yielding estimates of the unbounded drag. The methodology was verified by testing Newtonian fluids and comparing the results to Kaplun’s (1957) prediction for unbounded drag. The test fluids used were a silicone oil, a polybutene, and two Boger fluids. By comparing the Boger fluid results to equally viscous Newtonian results, the contributions of elasticity to the drag were determined. The Deborah number (De) was used to represent the magnitude of flow elasticity, and an onset of elastic effects was measured between 0.5 and 0.7.

Darbo apimtis yra 51 puslapių, jame yra 23 paveikslėliai. Literatūros aprašą sudaro 36 literatūros šaltiniai. Pagrindinis tiriamojo darbo tikslas – išanalizuoti hidraulinio cilindro stūmoklio greičio charakteristikų priklausomybę, keičiant hidraulinio cilindro apkrovą bei esant pastoviam siurblio slėgiui. Magistrantūros baigiamąjį darbą sudaro trys dalys: literatūros apžvalga, teoriniai tyrimai ir eksperimentiniai tyrimai. Literatūros apžvalgoje pateikiama droselinės hidraulinių sistemų reguliavimo sistemos, automatizuotos sistemos bei jų sandara. Teoriniuose tyrimuose yra išnagrinėtas droselinis valdymas ir reguliavimas, jo veikimo principai, naudingumo koeficientai bei galios balansas. Eksperimentiniuose tyrimuose yra išnagrinėta hidraulinio cilindro stūmoklio greičio charakteristikų priklausomybė nuo hidraulinio cilindro stūmoklio judėjimo greičio bei apkrovos. Sumontavus specialią hidraulinę sistemą atlikti hidraulinio cilindro stūmoklio greičio charakteristikų tyrimai. / Volume of work is 51 pages and contains 23 pictures. References inventory consists of 36 literary sources. The main aim of the investigation - to analyze the hydraulic cylinder shaft speed characteristics of dependency, changing the working pressure of hydraulic system and droseliavimo character. Master's thesis consists of three parts: an overview of sources of information, an overview of theoretical studies and experimental studies. Review of information sources describe butterfly hydraulic systems framework, addresses the butterfly speed control characteristics. The work purpose – to find out features of throttle adjustment of speed of movement the piston of hydraulic system of the big capacity. Experimental researches have been carried out with earlier described device. In the hydraulic cylinder design changes have been executed, the sizes and throttle place by means of theoretical throttle characteristic ADR = f(h) are changed. For reduction of turn time of a working platform it was necessary to increase pressure in hydraulic systems with 60 to 70 bar. Pressure increase has allowed piston to increase speed of movement. These changes have specified on a smooth stop of a working platform a problem. Time of turn of a working platform has decreased till 1,31 seconds. The piston pressure in the braking chamber is equal in last phase of work 48 bar, it tells about prevention of blow the piston about the hydraulic cylinder.

The non-linear model of pneumatic acting system, consisting of proportional directional control valve and symmetric rodless pneumatic cylinder is developed and investigated in this paper. This model enables to evaluate influence of essential nonlinearities concerned with working characteristics of airflow regulating valves and pneumatic cylinders on dynamics of the system. The modeling results of pneumatic acting system under several initial working conditions are presented and discussed in this article. The model reference based adaptive control method of force regulation in electro-pneumatic servo system is proposed and investigated in this paper to. This method allows eliminating of influence of nonlinearities of pneumatic cylinder and directional control valve on behavior of force regulation system. Therefore controllers of higher hierarchy level such as velocity and position controllers can be designed using conventional methods based on quantitative optimum. The modeling results of investigated system are presented in the paper.

The accuracy of existing methods for estimating the drag based on experimental flow field measurements were assessed for two-dimensional bodies. The effects of control volume boundary placement and inherent simplifying assumptions were also investigated. Wind tunnel experiments were performed on a circular cylinder operating at a Reynolds number of 8,000 and 20,000, and on a NACA 0018 airfoil operating at a chord Reynolds number of 100,000 for three angles of attack (α), specifically, 5◦, 10◦, and 15◦. The circular cylinder experiments fall within the the shear layer transition flow regime. Airfoil investigations span both types of flow development common to low Reynolds number airfoil operation. For α = 5◦ and 10◦, a separation bubble forms on the upper surface of the airfoil, while, for α = 15◦, the flow separates without reattaching, resulting in a stalled airfoil. Wake velocity and pressure measurements were performed at several downstream locations to investigate the impact of control volume boundary placement. Wake profiles were measured between 3 and 40 diameters downstream from the circular cylinder axis and between 1 and 4.5 chord lengths from the trailing edge of the airfoil. In addition to wake profiles, the outer flow velocity variation was quantified to investigate the appropriate location to measure freestream flow characteristics in a test section with streamwise-varying outer flow conditions. The results show that drag estimates are strongly dependent on the streamwise position of the measured wake profile for all methods investigated. Drag estimates improved, and streamwise variation decreased, with increasing streamwise position of the flow measurements. For the pressure based method examined, wake measurements should be taken at least 10 times the projected model height downstream of the model. In the case of the circular cylinder, this is equivalent to 10 diameters and, for the airfoil investigated, it is approximately 1 chord length from the trailing edge. For the methods relying on velocity measurements, acceptable estimates of drag were possible when based on measurements taken at least 30 projected heights downstream, i.e., 30 diameters for the circular cylinder and 3 chord lengths for the airfoil model investigated. The findings highlight the importance of providing a detailed description of the methodology and experimental implementation for drag estimates based on flow field measurements. Finally the study offers guidelines for implementing momentum integral based drag calculations in future investigations.

The majority of commercially available ultrasonic transducers used to excite and measure wave propagation in structures can be coupled only to a free surface. While convenient, this method is likely to excite multiple structural modes, making data interpretation difficult. Furthermore, the many modes excited make predicting the structure’s response a computationally intensive task. Here the dynamic radial displacement induced by a transient radial point load is calculated at more than 230,000 points on the outer surface of a virgin steel pipe to simulate a typical experiment. The radial component of the displacement field is calculated by convolving the Green’s functions of the pipe with the transient load. These functions are calculated on personal computers (in a distributed arrangement) by employing modal summation. The mode shapes are obtained from a Semi-Analytical Finite Element formulation used in conjunction with a separation of variables. The results are presented in a four dimensional animation, providing easier interpretations and insight into how to best select observation points for the detection of defects. The accuracy of the calculated displacements is verified experimentally. Agreement is good when magnitude and phase corrections are incorporated from the frequency response curves of the transducers used.