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- Khan, Suleman, et al.
(författare)
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A design Methodology for haptic devices
- 2011
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Ingår i: Proceedings of the 18th International Conference on Engineering Design (ICED11), Vol. 4. - 9781904670247 ; , s. 288-298
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Konferensbidrag (refereegranskat)abstract
- This paper presents a design methodology for optimal design of haptic devices, considering aspects form all involved engineering domains. The design methodology is based on parametric modeling, iterative and integrated design approach that leads to easier design space exploration for global optimal design and initial verification in the conceptual design phase. For global optimization, performance indices such as; workspace volume, isotropy, stiffness, inertia and control of the device were from all involved engineering domains were considered. To handle this complex and non-linear optimization problem, a multi-objective algorithm together with a new developed optimization function was used, to obtain a global optimum solution. A case study, where the methodology has been applied to develop a parallel haptic device is presented in detail in this paper. The results obtain from the test case model show significant improvements in the performances of the device.
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| 2. |
- Khan, Suleman, et al.
(författare)
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Dynamic based control strategy for haptic devices
- 2011
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Ingår i: World Haptics Conference (WHC), 2011 IEEE Issue Date: 21-24 June 2011. - 9781457702990 ; , s. 131-136
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Konferensbidrag (refereegranskat)abstract
- Transparency is a key performance measure for haptic devices. In this paper, we investigate a control strategy to increase the transparency of a haptic device. This control strategy is based on careful analysis of the dynamics of the haptic device, computed torque feed forward control and current feedback based force control. The inverse dynamic equation of motion for the device is derived using Lagrangian formalism and the dominating terms are identified for some representative motion trajectories. The user contact dynamic model is identified using experiments on the device with different users. A PI controller using motor current measurements is used to follow the reference force from the virtual environment. Experimental results illustrate the effectiveness of the control strategy.
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| 3. |
- Granmo, Tobias, 1972, et al.
(författare)
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Aha-Festival 2021 "The suspension of disbelief" Part 2
- 2021
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Ingår i: Chalmers Tekniska Högskola 25 of November 2021.
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- Of course I know, but still..Imagine sitting in the audience of a theater play when on stage two people are waving a blue plastic sheet between them. A third person comes walking across the stage with a cardboard structure around their waist and two wooden sticks in their hands. It is obvious that what you see is picturing someone in a boat, on the ocean. If you doubt that and say “I see that it is not the ocean it is plastic!” you will break the necessary agreement in an aesthetic experience. “The suspension of disbelief” seems to be a condition for experiencing different cultural phenomena. Is this also relevant in science and other areas of knowledge production? Duo Granmo/Berg theme: Man- Machine a workshop with musical Artefacts
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| 9. |
- Sattari, Amir, 1980-
(författare)
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Investigations of Flow Patterns in Ventilated Rooms Using Particle Image Velocimetry : Applications in a Scaled Room with Rapidly Varying Inflow and over a Wall-Mounted Radiator
- 2015
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- This thesis introduces and describes a new experimental setup for examining the effects of pulsating inflow to a ventilated enclosure. The study aimed to test the hypothesis that a pulsating inflow has potential to improve ventilation quality by reducing the stagnation zones through enhanced mixing. The experimental setup, which was a small-scale, two-dimensional (2D), water-filled room model, was successfully designed and manufactured to be able to capture two-dimensional velocity vectors of the entire field using Particle Image Velocimetry (PIV). Using in-house software, it was possible to conclude that for an increase in pulsation frequency or alternatively in the flow rate, the stagnation zones were reduced in size, the distribution of vortices became more homogeneous over the considered domain, and the number of vortices in all scales had increased. Considering the occupied region, the stagnation zones were moved away in a favorable direction from a mixing point of view. In addition, statistical analysis unveiled that in the far-field occupied region of the room model, stronger eddies were developed that we could expect to give rise to improved mixing. As a fundamental experimental study performed in a 2D, small-scale room model with water as operating fluid, we can logically conclude that the positive effect of enhanced mixing through increasing the flow rate could equally be accomplished through applying a pulsating inflow.In addition, this thesis introduces and describes an experimental setup for study of air flow over a wall-mounted radiator in a mockup of a real room, which has been successfully designed and manufactured. In this experimental study, the airflow over an electric radiator without forced convection, a common room-heating technique, was measured and visualized using the 2D PIV technique. Surface blackening due to particle deposition calls for monitoring in detail the local climate over a heating radiator. One mechanism causing particle deposition is turbophoresis, which occurs when the flow is turbulent. Because turbulence plays a role in particle deposition, it is important to identify where the laminar flow over radiator becomes turbulent. The results from several visualization techniques and PIV measurements indicated that for a room with typical radiator heating, the flow over the radiator became agitated after a dimensionless length, 5.0–6.25, based on the radiator thickness.Surface properties are among the influencing factors in particle deposition; therefore, the geometrical properties of different finishing techniques were investigated experimentally using a structured light 3D scanner that revealed differences in roughness among different surface finishing techniques. To investigate the resistance to airflow along the surface and the turbulence generated by the surfaces, we recorded the boundary layer flow over the surfaces in a special flow rig, which revealed that the types of surface finishing methods differed very little in their resistance and therefore their influence on the deposition velocity is probably small.
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| 10. |
- Acuña, José, 1982-
(författare)
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Distributed thermal response tests : New insights on U-pipe and Coaxial heat exchangers in groundwater-filled boreholes
- 2013
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- U-pipe Borehole Heat Exchangers (BHE) are widely used today in ground source heating and cooling systems in spite of their less than optimal performance. This thesis provides a better understanding on the function of U-pipe BHEs and Investigates alternative methods to reduce the temperature difference between the circulating fluid and the borehole wall, including one thermosyphon and three different types of coaxial BHEs.Field tests are performed using distributed temperature measurements along U-pipe and coaxial heat exchangers installed in groundwater filled boreholes. The measurements are carried out during heat injection thermal response tests and during short heat extraction periods using heat pumps. Temperatures are measured inside the secondary fluid path, in the groundwater, and at the borehole wall. These type of temperature measurements were until now missing.A new method for testing borehole heat exchangers, Distributed Thermal Response Test (DTRT), has been proposed and demonstrated in U-pipe, pipe-in-pipe, and multi-pipe BHE designs. The method allows the quantification of the BHE performance at a local level.The operation of a U-pipe thermosyphon BHE consisting of an insulated down-comer and a larger riser pipe using CO2 as a secondary fluid has been demonstrated in a groundwater filled borehole, 70 m deep. It was found that the CO2 may be sub-cooled at the bottom and that it flows upwards through the riser in liquid state until about 30 m depth, where it starts to evaporate.Various power levels and different volumetric flow rates have been imposed to the tested BHEs and used to calculate local ground thermal conductivities and thermal resistances. The local ground thermal conductivities, preferably evaluated at thermal recovery conditions during DTRTs, were found to vary with depth. Local and effective borehole thermal resistances in most heat exchangers have been calculated, and their differences have been discussed in an effort to suggest better methods for interpretation of data from field tests.Large thermal shunt flow between down- and up-going flow channels was identified in all heat exchanger types, particularly at low volumetric flow rates, except in a multi-pipe BHE having an insulated central pipe where the thermal contact between down- and up-coming fluid was almost eliminated.At relatively high volumetric flow rates, U-pipe BHEs show a nearly even distribution of the heat transfer between the ground and the secondary fluid along the depth. The same applies to all coaxial BHEs as long as the flow travels downwards through the central pipe. In the opposite flow direction, an uneven power distribution was measured in multi-chamber and multi-pipe BHEs.Pipe-in-pipe and multi-pipe coaxial heat exchangers show significantly lower local borehole resistances than U-pipes, ranging in average between 0.015 and 0.040 Km/W. These heat exchangers can significantly decrease the temperature difference between the secondary fluid and the ground and may allow the use of plain water as secondary fluid, an alternative to typical antifreeze aqueous solutions. The latter was demonstrated in a pipe-in-pipe BHE having an effective resistance of about 0.030 Km/W.Forced convection in the groundwater achieved by injecting nitrogen bubbles was found to reduce the local thermal resistance in U-pipe BHEs by about 30% during heat injection conditions. The temperatures inside the groundwater are homogenized while injecting the N2, and no radial temperature gradients are then identified. The fluid to groundwater thermal resistance during forced convection was measured to be 0.036 Km/W. This resistance varied between this value and 0.072 Km/W during natural convection conditions in the groundwater, being highest during heat pump operation at temperatures close to the water density maximum.
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