New nonlinear control algorithms for multiple robot arms

Multiple coordinated robot arms are modeled by considering the arms as closed kinematic chains and as a force-constrained mechanical system working on the same object simultaneously. In both formulations, a novel dynamic control method is discussed. It is based on feedback linearization and simultaneous output decoupling technique. By applying a nonlinear feedback and a nonlinear coordinate transformation, the complicated model of the multiple robot arms in either formulation is converted into a linear and output decoupled system. The linear system control theory and optimal control theory are used to design robust controllers in the task space. The first formulation has the advantage of automatically handling the coordination and load distribution among the robot arms. In the second formulation, it was found that by choosing a general output equation it became possible simultaneously to superimpose the position and velocity error feedback with the force-torque error feedback in the task space     

Protein crystal growth aboard the U.S. space shuttle flights STS-31 and STS-32.

The first microgravity protein crystal growth experiments were performed on Spacelab I by Littke and John. These experiments indicated that the space grown crystals, which were obtained using a liquid-liquid diffusion system, were larger than crystals obtained by the same experimental system on earth. Subsequent experiments were performed by other investigators on a series of space shuttle missions from 1985 through 1990. The results from two of these shuttle flights (STS-26 and STS-29) have been described previously. The results from these missions indicated that the microgravity grown crystals for a number of different proteins were larger, displayed more uniform morphologies, and yielded diffraction data to significantly higher resolutions than the best crystals of these proteins grown on earth. This paper presents the results obtained from shuttle flight STS-32 (flown in January, 1990) and preliminary results from the most recent shuttle flight, STS-31 (flown in April, 1990).     

防空导弹武器系统与反辐射导弹的对抗研究

首先概述了防空导弹武器系统,介绍了其主要技战术性能及关键技术的现状和发展趋势。接着概述了反辐射导弹,介绍反辐射导弹的主要特性及其关键技术和发展趋势。最后探讨了防空导弹武器系统与反辐射导弹的对抗措施。     

Feasibility of developing an ionospheric E-region electron density storm model using TIMED/SABER measurements

We present a new technique for improving ionospheric models of nighttime E-region electron densities under geomagnetic storm conditions using TIMED/SABER measurements of broadband 4.3 μm limb radiance. The response of E-region electron densities to geomagnetic activity is characterized by SABER-derived NO⁺(v) 4.3 μm Volume Emission Rates (VER). A storm-time E-region electron density correction factor is defined as the ratio of storm-enhanced NO⁺(v) VER to a quiet-time climatological average NO⁺(v) VER, which will be fit to a geomagnetic activity index in a future work. The purpose of this paper is to demonstrate the feasibility of our technique in two ways. One, we compare storm-to-quiet ratios of SABER-derived NO⁺(v) VER with storm-to-quiet ratios of electron densities measured by Incoherent Scatter Radar. Two, we demonstrate that NO⁺(v) VER can be parameterized by widely available geomagnetic activity indices. The storm-time correction derived from NO⁺(v) VER is applicable at high-latitudes.     

The Balloon Array for RBSP Relativistic Electron Losses (BARREL)

BARREL is a multiple-balloon investigation designed to study electron losses from Earth’s Radiation Belts. Selected as a NASA Living with a Star Mission of Opportunity, BARREL augments the Radiation Belt Storm Probes mission by providing measurements of relativistic electron precipitation with a pair of Antarctic balloon campaigns that will be conducted during the Austral summers (January-February) of 2013 and 2014. During each campaign, a total of 20 small (～20 kg) stratospheric balloons will be successively launched to maintain an array of ～5 payloads spread across ～6 hours of magnetic local time in the region that magnetically maps to the radiation belts. Each balloon carries an X-ray spectrometer to measure the bremsstrahlung X-rays produced by precipitating relativistic electrons as they collide with neutrals in the atmosphere, and a DC magnetometer to measure ULF-timescale variations of the magnetic field. BARREL will provide the first balloon measurements of relativistic electron precipitation while comprehensive in situ measurements of both plasma waves and energetic particles are available, and will characterize the spatial scale of precipitation at relativistic energies. All data and analysis software will be made freely available to the scientific community.     

Comparative ISS accelerometric analyses

Two accelerometric records coming from the SAMSes es08 sensor in the Columbus module, the so-called Runs 14 and 33 in terms of the IVIDIL experiment, has been studied here using standard digital signal analysis techniques. The principal difference between both records is the vibrational state of the IVIDIL experiment, that is to say, during Run 14 the shaking motor of the experiment is active while that in Run 33 this motor is stopped. Identical procedures have been applied to a third record coming from the SAMSII 121f03 sensor located in the Destiny module during an IVIDIL quiescent period. All records have been downloaded from the corresponding public binary accelerometric files from the NASA Principal Investigator Microgravity Services, PIMS website and, in order to be properly compared, have the same number of data. Results detect clear differences in the accelerometric behavior, with or without shaking, despite the care of the designers to ensure the achievement of the ISS μg-vibrational requirements all along the experiments.     

Introduction to global short message communication service of BeiDou-3 navigation satellite system

Short Message Communication (SMC) is a featured service of BeiDou Navigation Satellite System (BDS). After its successful deployment in 2003, Regional Short Message Communication (RSMC) service has been continuously serving China and its neighboring countries and regions, especially in life safety scenarios. In this paper, the architecture of the Global Short Message Communication (GSMC) system is proposed based on the medium earth orbit (MEO) constellation and the crosslinks of the global BeiDou navigation system (BDS-3). Three subtypes of GSMC service, i.e. positioning report, emergency search and rescue (SAR) and regular SMC are designed in accordance with the technical characteristic of integration of navigation and communication in BDS-3, which supports future wide applications of GSMC. The performance of the designed GSMC system is analyzed by numerical calculations. As BDS-3 was officially announced completion on July 31, 2020, GSMC has been providing initial service. First test results of the in orbit GSMC payloads are also presented in the paper to verify the designed capabilities. Preliminary results also show that the requirements of Global Maritime Distress and Safety System (GMDSS) can also be fulfilled.     

HORACE: A compact cold atom clock for Galileo

HORACE (HOrloge à Refroidissement d’Atomes en Cellule = clock based on atoms cooled from vapour cell) is a compact cold caesium atom clock developed in SYRTE at Paris Observatory. This clock can operate both on ground and in microgravity environment. Design of HORACE is based on isotropic light cooling, allowing performing the whole clock sequence (cooling, atomic preparation, Ramsey interrogation and detection) at the same place. Compared to more conventional cold atom clocks such as atomic fountains, the use of isotropic light cooling simplifies both the optical part of the setup and the detection sequence, and leads to a drastic size reduction of the physics package. Very good short-term performances have been demonstrated at SYRTE since relative frequency instability of 2.2 × 10⁻¹³ τ^−1/2 has been obtained. Optimization of the long term stability is still under progress and current results show relative frequency instability around 3 × 10⁻¹⁵ in 10⁴ s of integration. With these performances, HORACE appears as a good candidate both for Galileo’s ground segment clock and for onboard Galileo clock.     

Passive sonar fusion for submarine C2 systems

The most important sensors for gathering target information onboard a submarine are passive sonars. Problems concerning fusion of these passive sonars are discussed. Three typical passive sonars-passive noise sonar, passive ranging sonar and acoustic pulse surveillance sonar-constitute a passive sonar system for data fusion. This paper is concerned mainly with problems of significance in system development, such as tactical application background, special fusion techniques and own-ship maneuver considerations