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2D microgravity test-bed for the validation of space robot control algorithms

Oleś J., Kindracki J., Rybus T., Mężyk Ł., Paszkiewicz P., Moczydłowski R., Barciński T., Seweryn K., Wolański P.

Journal of Automation Mobile Robotics and Intelligent Systems

2017

Vol. 11, No. 2

95--104

The utilization of satellites equipped with robotic arms is one of the existing strategies for Active Debris Removal (ADR). Considering that the time intended for on-orbit capturing manoeuvres is strictly limited, any given space robot should possess a certain level of autonomy. This paper is about the control of on-orbit space robots and the testing of such objects in laboratory conditions. The Space Research Centre of the Polish Academy of Sciences (CBK PAN) possesses a planar air bearing microgravity simulator used for the testing of advanced control algorithms of space robots supported on air bearings. This paper presents recent upgrades to the testing facility. Firstly, the base of the space robot is now equipped with manoeuvre thrusters using compressed nitrogen and therefore allowing for position control of the entire system. Secondly, a signal from an external vision system, referencing the position and orientation of the robot’s parts is used by the control system for the closed loop control.

Temperature effect on explosion parameters of hydrogen-air deflagrations in presence of water vapor

Grabarczyk M., Żbikowski M., Mężyk Ł., Teodorczyk A.

Challenges of Modern Technology

2016

Vol. 7, no. 3

39-44

Results of investigation of hydrogen-air deflagrations phenomenon in closed vessel in various initial temperatures and volume fraction of water vapor are presented in following paper. Tests were performed in apparatus which construction complies with EN 15967 recommendations—20-litre sphere. Studied parameters were explosion pressure (Pex) and maximum explosion pressure (Pmax). Defining the influence of the initial conditions (temperature and amount of water vapor) on the maximum pressure of the hydrogen-air deflagration in a constant volume was the main aim. Initial temperatures were equal to 373K, 398K and 413K. Initial pressure was ambient (0.1 MPa). Hydrogen volume fraction differed from 15% to 80%, while humidity volume fraction from 0% to 20%. Ignition source was placed in geometrical center of testing chamber and provided energy between 10-20J from burnout of fuse wire with accordance to abovementioned standard. Common features of all experimentally obtained results were discussed. Maximum explosion pressure (Pmax) decreases with increasing the initial temperature. Furthermore, addition of the water vapor for constant initial temperature decreases value of Pmax and shifts the maximum peak to the direction of lean mixtures. Data provided in paper can be useful in assessment of explosion risk of industry installations working with hydrogen-air atmospheres with high water vapor addition.

Experimental research on influence of geometrical configuration on high pressure hydrogen outflow ignition process

Oleszczak P., Mężyk Ł., Wolański P.

Journal of KONES

2009

Vol. 16, No. 4

357-366

Hydrogen is regarded as a potential future fuel for various kinds of vehicles: fuel cell cars, trucks, buses etc. Storing and transportation issues are the crucial safety problems concerned with utilization ofhydrogen. Because of its very łów density hydrogen needs to be stored under very high pressure, in range of 35 division sign 70 MPa, and this create hazard of sudden discharge of hydrogen leading to ignition and severe accident. The aim of the presented research is an experimental investigation of hydrogen ignition as a result of a compression and heating of air by shock wave generated by the discharge of the hydrogen. Mixing of the air heated up by the shock wave and expanding hydrogen can produce combustible mixture of sufficiently high temperature and can lead to ignition. The critical conditions for ignition depend mainly on hydrogen discharge pressure, geometrical configuration, parameters of the ambient air, obstacles, etc. Experimental research -was conducted on a facility specially constructed in Combustion Laboratory, the Institute of Heat Engineering, Warsaw University of Technology. The facility consists from the pressure tank and high pressure hydrogen installation. To allow visualization the observation section is equipped with high quality optical windows. Schlieren visualization system and high speed digital camera was used to register high pressure hydrogen outflow and potential ignition. The high speed digital camera was used to take Schlieren or direct pictures of the process. Additionally, the experiment is registered with use of conventional digital camera. Experiments were conducted for different discharge pressure of hydrogen and outflow to "open space " as well to specially prepared obstacles. Critical condition for which ignition occurs were evaluated for both cases. The high speed Schlieren and direct pictures taken during the experiments are presented in the paper. The influence of presence of obstacles on the feasibility of hydrogen ignition during outflow from high pressure installation is discussed and analyzed.