1,721,262 research outputs found
ARCADE small-scaledockingmechanismformicro-satellites
No full textThe development of on-orbit autonomous rendezvous and docking (ARD) capabilities represents a key point for a number of appealing mission scenarios that include activities
of on-orbit servicing, automated assembly of modular structures and active debris
removal. As of today, especially in the field of micro-satellites ARD, many fundamental technologies are still missing or require further developments and micro-gravity testing.
In this framework, the University of Padova, Centre of Studies and Activities for Space (CISAS), developed the Autonomous Rendezvous Control and Docking Experiment (ARCADE), a technology demonstrator intended to fly aboard a BEXUS stratospheric balloon. The goal was to design, build and test, in critical environment conditions, a proximity relative navigation
system, a custom-made reaction wheel and a small-size docking mechanism. The ARCADE docking mechanism was designed against a comprehensive set of requirements and it can be classified as small-scale, central, gender mating and unpressurized. The large use of commercial components makes it low-cost and simple to be manufactured. Last, it features a good tolerance to off-nominal docking conditions and a by-design soft docking capability.
The final design was extensively verified to be compliant with its requirements by means of numerical simulations and physical testing. In detail, the dynamic behaviour of the mechanism in both nominal and off-nominal conditions was assessed with the multibody dynamics analysis software MD ADAMS2010 and functional tests were carried out within the fully integrated ARCADE experiment to ensure the docking system efficacy and to highlight possible issues. The most relevant results of the study will be presented and discussed in conclusion to this pape
Modelling and control of double-cone dielectric elastomer actuator
No full textAmong various dielectric elastomer devices, cone actuators are of large interest for their multidegree-
of-freedom design. These objects combine the common advantages of dielectric
elastomers (i.e. solid-state actuation, self-sensing capability, high conversion efficiency, light
weight and low cost) with the possibility to actuate more than one degree of freedom in a single
device. The potential applications of this feature in robotics are huge, making cone actuators very
attractive. This work focuses on rotational degrees of freedom to complete existing literature and
improve the understanding of such aspect. Simple tools are presented for the performance
prediction of the device: finite element method simulations and interpolating relations have been
used to assess the actuator steady-state behaviour in terms of torque and rotation as a function of
geometric parameters. Results are interpolated by fit relations accounting for all the relevant
parameters. The obtained data are validated through comparison with experimental results:
steady-state torque and rotation are determined at a given high voltage actuation. In addition, the
transient response to step input has been measured and, as a result, the voltage-to-torque and the
voltage-to-rotation transfer functions are obtained. Experimental data are collected and used to validate the prediction capability of the transfer function in terms of time response to step input and frequency response. The developed static and dynamic models have been employed to implement a feedback compensator that controls the device motion; the simulated behaviour is compared to experimental data, resulting in a maximum prediction error of 7.5%
Development of a zero-dimensional numerical model for optimization and diagnostic of gas systems
No full textInternal Publication, University of Padova, .Reg. Tribunale P
DESIGN OF DOCKING MECHANISM FOR SMALL SPACECRAFT
No full textDocking mechanisms have been employed in space missions for more than 50 years. In fact, since the Apollo program, docking ports became unavoidable subsystems to connect different spacecraft together. With the start of the Space Stations era, the new concept of standardization was born and the contribution of different participants from various countries led to the definition of common design requirements. However, this standardization progress involved only large space structures and manned missions: in the field of small commercial and scientific automatic spacecraft there is still a lack on research and development of docking technologies. At the same time, the design and exploitation of small satellites can open new ways to carry out space activities. Large structures such as segmented mirrors telescopes or solar arrays can be realized through the mechanical connection of many small satellites. Deep-space multi-probe automatic exploration programs could also take benefit from the employment of docking systems to extend and reconfigure their mission profiles.
In this framework this paper presents a new concept of docking system for small satellites. The proposed solution has axis-symmetric interfaces with a “probe and drogue" logic; to perform docking and undocking maneuvers it respectively demands for a well defined chaser approach velocity to activate the passive latches and propulsion abilities to perform separation. In this way the implementation of active locking mechanisms is avoided.
The mechanism design and preliminary validation through numerical simulations is presented: 3-D modeling, kinematic and dynamic analysis guided the development of the interfaces geometry
Improvement of the CISAS high-shot-frequency light-gas gun
Full text linkAbstract
A preliminary version of Two Stage Light Gas Gun for impact testing directly derived from fusion
pellet injectors was built in the CISAS laboratories few years ago. The main purpose of that system
was to have a starting point to develop a new unit expressly dedicated to hypervelocity impacts.
The system has started its development phase in the late '97 and it was fully operative in the late
'99. In that configuration, it was able to accelerate 200 mg at 3.5 km/s and 100 mg at 4 km/s with a
shot frequency between 20-30 shot per day. The system at that point was reliable but the
performances were not good enough for impact testing. A great computation and experimental
work started at that point to improve the gun performances. The main subsystems of the gun have
been completely revised. Extensive numerical simulations have been used to optimise the first
stage, the head and the damping system. Leaving almost unaltered the main geometric
parameters of the original gun, an almost new unit has been developed, building a new fist stage
valve, a new damping system, and a new gun head. The new system has been tested end
experimentally characterised and optimised. In its new configuration, the gun is able to accelerate
100 mg at 5.5 km/s with a shot frequency of (at least) 10 shots per day; some tests show also that
a speed up to 6 km/s with the same shot frequency is reachable. In this paper, the basic gun
configuration and the improvement of each part are discussed
New Optical Communication Capabilities Using Nanosatellites
No full textIn this paper, the benefits derived from the exploitation of nanosatellites for complex telecommunication missions are presented, along with their limitations, and laser technology is identified as a viable solution to dramatically increase the downlink and crosslink capabilities of such miniature platforms. Then, the critical technological issues concerning the integration of an optical telecom terminal on a nanosatellite platform are discussed, considering the perspective advancements in areas such as power generation, propulsion and attitude control. The incompatibility of laser terminals pointing requirements with the current and perspective nanosatellite attitude stability has been identified as the most critical issue to be addressed in order to implement optical links on nanosatellites. A possible solution is presented at the end of the discussion
Filterkit: an industrial development project for SMEs of the Veneto Region
No full textThis paper presents an example of an innovation network which provides the necessary resources to change the business model of a group of local traditional SMEs to improve global competitiveness. The network generates smaller clusters aiming at developing new knowledge which is then shared within the all network. Several clusters exist the same time, in this way each single company is exposed to a rich flow of technological information and opportunities to generate new business activity
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