Search

This paper investigates a tracking control issue for a class of drag-free spacecraft with state constraints caused by the optical assembly. Firstly, a nonlinear kinematics and dynamics relative equation of coupling system of position and attitude is devised by a 6-degree of freedom (DOF) model of rigid body. Secondly, an optimal control method with a terminal functional is designed to meet state constraints. To solve the Hamilton-Jacobi-Bellman (HJB) equation generated by the optimal control of the nonlinear model, a policy iteration ideal is presented and the final numerical solution of the iteration is obtained by a critic neural network (NN). Thirdly, to enhance the robustness of the closed-loop system, an optimal sliding mode control is proposed, which can ensure the optimal and robustness performance simultaneously. At last, the simulation results demonstrate the performance of the proposed methods and the contrast of precision and robustness of two methods are showcased. [ABSTRACT FROM AUTHOR]

• Space debris detection; • Payload camera breadboard for space surveillance; • Star tracking and space debris detection algorithms; • Hybrid time-index image algorithm. Space debris threatens space activities, demanding continuous observation and tracking by the Space Surveillance Network (SSN) to secure the Earth's orbits. However, SST efforts are limited by the size and brightness of the debris, detecting only a small amount of the total. Seeking to overcome such limitations, this study proposes an alternative payload camera capable of extracting the attitude of a satellite in orbit and detecting under-catalogued debris. This work is a sequential study of previous research, where the camera breadboard was designed and implemented. The contribution of this paper is the evaluation of star tracking and space debris algorithms to be implemented in the payload camera, the development and implementation of a new hybrid algorithm and the elaboration of performance metrics for comparison between the algorithms. The observation data of the previous research was used as input for the algorithms' tests. For star identification and, consequently, attitude extraction, the chosen algorithm was Tetra. The results were compared to the standard star identification software, Astrometry.net , to assess the attitude accuracy. For debris detection, ASTRiDE and the Hybrid time-index image algorithms were used. A comparison of the results was made to establish a performance evaluation metric in terms of detectability, time, and computational cost. [ABSTRACT FROM AUTHOR]

This paper addresses the multi-objective integrated attitude control problem of a large solar power satellite (SPS) in the presence of time-varying parameters, disturbances, and actuator saturation. The attitude coupling dynamic model, which could accurately describe the rotational motion of different SPS components, is firstly obtained. The gravity gradient, solar radiation pressure, microwave radiation reflection, and friction torques are investigated to evaluate their influence on attitude control accuracy. The coupling dynamic model is linearized and discretized, which provides a subsystem model for distributed controller design. A distributed incremental predictive controller is designed for each rotation channel to form a distributed system. The augmented system state is defined to solve the complex constraint problem, and the predicted value with feedback correction is introduced to deal with the disturbances. Besides, the stability of the system is analyzed by considering external disturbances and actuator failure. Comparative analysis with centralized methods under the same prediction horizon is provided, and the results demonstrate a tenfold solution performance enhancement while maintaining accuracy. Furthermore, the controller is integrated with feedback correction, which could improve control accuracy by at least one order of magnitude. The proposed controller reduces the adjusting time for attitude stabilization by 56.8 % in the presence of actuator failure. The simulation results demonstrate that the proposed controller has good robustness and fault tolerance, which provides a feasible solution for SPS multiple attitude control missions. [ABSTRACT FROM AUTHOR]

A modified unscented Kalman filter is presented to estimate the quaternion parameters as well as the angular velocities of a rigid gyro-less satellite under faulty sensor conditions. The task is carried out using the Sun sensor and magnetometers as attitude sensors with bounded noise and unknown fault(s). Following the presentation of the satellite attitude dynamics and filtering formulations, a new fault detection and isolation algorithm is proposed. The latter is based on a modified unscented Kalman filter structure for improved fault detection, sensor isolation, and attitude control (AC). A Backtracking Search Algorithm (BSA) is also used to design and optimize the PID controller gains, as well as to optimize sensor installation orientation for residual signal decoupling. In this regard, the paper presents and proves a theory that describes how the proposed optimization process for sensor installation can analytically decouple the faulty orientation signal from the healthy ones. A comparison of attitude and angular velocity estimation approaches using the standard Kalman, extended Kalman, and a proposed modified unscented Kalman filter is also provided. The results show that the proposed filter performs significantly better in closed-loop AC systems and copes adequately with sensor faults. • Gyro-less satellite attitude estimation and control with faulty sensors is studied. • A modified unscented Kalman filter is proposed and compared with KF and EKF. • A novel fault detection and isolation (FDI) algorithm is developed. • FDI is optimized with respect to sensor installation (SI) for improved accuracy. • A theorem is proven that demonstrates the decupling of the residual signals. [ABSTRACT FROM AUTHOR]

Abstract The construction industry is a large contributor to global emissions, though it is becoming more aligned with sustainability practices. Historically, the industry has focused on cost, production and time, but now adds emissions to this list. Industry attitudes to emissions have been the subject of a number of surveys, but these necessarily only give qualitative information. This paper takes a quite different tack and establishes, for the first time, quantitative measures of industry attitude. Both the qualitative and quantitative approaches have a perception basis. The paper's approach is through the medium of utility and utility functions. The paper takes a number of industry scenarios and establishes the attitude of industry personnel to lower-emissions production. Generally, it is found that construction personnel are risk aversive to emissions, but to differing degrees. Here, risk is used in the sense of the magnitude and likelihood of an outcome involving emissions. The implications of this are demonstrated through an earthmoving operation, where the emissions-production results for differing degrees of risk aversion are highlighted. The paper is original in terms of offering a different view of emissions, and unique in its approach. By analysing the utility functions obtained, industry's attitude toward carbon emissions can be better understood. And flowing from this, more effective and efficient methods for reducing carbon emissions can be created. Graphical abstract Image 1 Highlights • Utility is advanced as a measure of attitudes to cleaner production. • Construction personnel are found to be risk averse to emissions. • The paper gives an original and unique view of attitudes to cleaner production. • A utility measure provides understanding of industry emissions attitudes. • Effective and efficient methods for reducing emissions can follow. [ABSTRACT FROM AUTHOR]

The attitude information of geostationary satellites is difficult to be obtained since they are presented in non-resolved images on the ground observation equipment in space object surveillance. In this paper, an attitude inversion method for geostationary satellite based on Unscented Particle Filter (UPF) and ground photometric data is presented. The inversion algorithm based on UPF is proposed aiming at the strong non-linear feature in the photometric data inversion for satellite attitude, which combines the advantage of Unscented Kalman Filter (UKF) and Particle Filter (PF). This update method improves the particle selection based on the idea of UKF to redesign the importance density function. Moreover, it uses the RMS-UKF to partially correct the prediction covariance matrix, which improves the applicability of the attitude inversion method in view of UKF and the particle degradation and dilution of the attitude inversion method based on PF. This paper describes the main principles and steps of algorithm in detail, correctness, accuracy, stability and applicability of the method are verified by simulation experiment and scaling experiment in the end. The results show that the proposed method can effectively solve the problem of particle degradation and depletion in the attitude inversion method on account of PF, and the problem that UKF is not suitable for the strong non-linear attitude inversion. However, the inversion accuracy is obviously superior to UKF and PF, in addition, in the case of the inversion with large attitude error that can inverse the attitude with small particles and high precision. [ABSTRACT FROM AUTHOR]

Abstract This study presents an original approach to the design of a complete digital attitude control unit for a UAV quadrotor. The approach is developed within the framework of Active Disturbance Rejection Control (ADRC) and Embedded Model Control (EMC), two well-established control design methodologies, both based on the estimation of the disturbances/uncertainties affecting the plant to control, and on their online cancellation. The attitude control design carried out in this paper demonstrates the possibility of adopting a simple input–output model to control the UAV attitude, while relying on the disturbance rejector to bridge the gap between model and plant reality. The designed attitude control unit encompasses an attitude state predictor, a control law, and a model-based reference generator. A multi-step test strategy is proposed to assess the performance of this disturbance-rejection-based attitude controller. Consequently, the presented experimental results are obtained both using a high-fidelity numerical simulator and in several experimental tests, carried out either on a laboratory single-axial test-bench or in-flight. Finally, the control unit performance is benchmarked, in simulation, against a state-of-the-art high-performance UAV attitude controller. [ABSTRACT FROM AUTHOR]

Abstract Consumers regularly waste products with unused utility (e.g., edible food, functioning appliances), but also have an aversion to such wastefulness. The present paper demonstrates that this wasting conflict has relevant managerial implications. Drawing upon cognitive dissonance theory, the authors predict and reveal in three experiments that brand attitudes for everyday mundane products can suffer when the unused utility of such products is wasted. Two scenario studies show that wasting a product with unused utility leads to feelings of discomfort (Experiment 1), and to lower product attitudes (Experiment 2). A final study (Experiment 3) replicates the effect on brand attitudes in an actual consumption situation. Moreover, it shows that brand visibility is a moderator in this process: wasting tends to lead to lower brand attitudes when the brand is visible at the moment of wasting, but not when the brand is not visible. Collectively, these experiments provide novel insights into how and when the generation of waste can have detrimental effects on brand attitudes, demonstrating the importance of consumer waste acts for industry. Highlights • Consumers experience a paradox between wasting products and aversion to waste. • Cognitive dissonance theory explains why wasting products lowers brand attitudes. • Wasting leads to more feelings of discomfort compared to other ways of disposal. • Wasting lowers brand attitudes when the brand is visible at the waste occasion. [ABSTRACT FROM AUTHOR]

There is a growing concern about the pollution of agricultural systems caused by plastic residue and debris. This pollution poses a threat to the quality of food products. To gain a deeper understanding of how to maintain cleaner farmlands and reduce plastic residue and debris pollution, this cross-sectional study investigated the intention and behavior of plastic residue management (BPRM) in farmlands. Using random sampling method, the study surveyed 338 farmers in northwestern Iran. The resulting evidence found that 37.6% of farmers perform the BPRM with a mean score above average. The path analysis cleared that among the conceptualized ecological, economic, and social connotations, only the ecological attitude had a significant and positive impact on the BPRM (β E c o A t t i → B H V = 0.28, p < 0.001). It was found that both fact feedback (β F F B s → Int = 0.76, p < 0.001) and causal feedback (β C F B s → Int = 0.22, p < 0.001) contribute to reducing plastic residue pollution and forecasting the intention to perform the BPRM. The intention, in turn, directly predicts BPRM (β Int → B H V = 0.30, p < 0.001). Using a 2 × 2 cross-tabulation of causal feedback and the scenario of landfilling, derived from perceived action-based life cycle analysis of plastic wastes, the association between the two variables was found to be statistically significant (x 2 (df) = 3.24(1), p < 0.05). The resulting evidence would provide essential information for farm management strategists and governmental authorities to reduce plastic residue pollution in farmlands. This can be achieved by implementing policy initiatives that aim to change farmers' intentions and behaviors. • Paper indicates how to keep farmlands cleaner from plastic residue pollution. • Factual feedback forecasts intention to perform plastic residue management behavior. • Cause feedback predicts intention to perform plastic residue management behavior. • Cause feedback links with scenario of landfilling from action-based life cycle. • Factual and causal feedback should be given to farmers. [ABSTRACT FROM AUTHOR]

A Next Generation Gravity Mission (NGGM) concept for measuring the Earth's variable gravity field has been recently proposed by ESA. The mission objective consists in measuring the temporal variations of the Earth gravity field over a long-time span, with very high spatial and temporal resolutions. This paper focuses on the guidance, navigation and control (GNC) design for the science phase of the NGGM mission. NGGM will consist of a two-satellite long-distance formation like GRACE, where each satellite will be controlled to be drag-free like GOCE. Satellite-to-satellite distance variations, encoding gravity anomalies, will be measured by laser interferometry. The formation satellites, distant up to 200 km, will fly in a quasi-polar orbit at an Earth altitude between 300 and 450 km. Orbit and formation control counteract bias and drift of the residual drag-free accelerations, in order to reach orbit/formation long-term stability. Drag-free control allows the formation to fly counteracting the atmospheric drag, ideally subject only to gravity. Orbit and formation control, designed through the innovative Integrated Formation Control (IFC), have been integrated into a unique control system, aiming at stabilizing the formation triangle consisting of satellites and Earth Center of Masses. In addition, both spacecraft must align their control axis to the satellite-to-satellite line (SSL) with micro-radian accuracy. This is made possible by specific optical sensors and the inter-satellite laser interferometer, capable of materializing the SSL. Such sensors allow each satellite to pursue an autonomous alignment after a suitable acquisition procedure. Pointing control is severely constrained by the angular drag-free control, which must ideally zero the angular acceleration vector, in the science frequency band. The control unit has been designed according to the Embedded Model Control methodology and is organized in a hierarchical way, where the drag-free control plays the role of a wide-band inner loop, and orbit/formation and attitude/pointing controls are the narrow band outer loops. The relevant state equations were converted to discrete time providing the embedded model, a fundamental part of the control unit. The state predictor, control law and reference generator were built on and interfaced to the embedded model. Simulated results, via a high-fidelity simulator, prove the concept validity and show that the control performances are in agreement with the defined mission requirements. Indeed, the presented control strategy is shown to be capable of keeping the attitude and formation variables stable within the required boundaries, all over the 10-year mission, through a low-thrust authority in the order of a few milli-Newton. [ABSTRACT FROM AUTHOR]

Abstract: A miniaturized attitude control system suitable for nanosatellites, developed using only commercial off-the-shelf components, is described in the paper. It is a complete and independent system to be used on board nanosatellites, allowing automated attitude control. To integrate this system into nanosatellites such as Cubesats its size has been reduced down to a cube of side about 5cm. The result is a low cost attitude control system built with terrestrial components, integrating three micro magnetotorquers, three micro reaction wheels, three magnetometers and redundant control electronics, capable of performing automatics operations on request from the ground. The system can operate as a real time maneuvering system, executing commands sent from the ground or as a standalone attitude control system receiving the solar array status from a hosting satellite and the satellite ephemeris transmitted from the ground station. The main characteristics of the developed system and test results are depicted in this paper. [Copyright &y& Elsevier]

Abstract: Based on the hypothesis of the interdependence of the different facets of man''s activity, this paper stresses the importance of sociocultural and sociohistorical elements in the interpretation of prosodic meaning and more particularly of intonational contour meaning. The first part of the paper provides a review of some main topics concerning the object of our study: prosodic stereotypes in cultural groups, the role of the larger context in speech analysis, and the relationship between intonational variations and group cultural norms. The second part of the paper focuses on the intonation of African-American Vernacular English. After an examination of the sparse research on the subject, an experiment reveals several intonational characteristics of the group which are reported to communicate sense of community, playfulness, and creativity. The importance of such behaviors in that speech community is supported by historical reports and recent observations. They are described as (1) originating from Africa and from the socio-economic changes the group has faced during its short history, and (2) serving to the expression of affirmation of black identity. This analysis confirms the need of a multifunctional approach in speech analysis which would include the larger context, particularly in prosody where these notions have rarely been considered. [Copyright &y& Elsevier]

Abstract: Context-aware computing is useful in providing individualized and automated services; so far it has focused on acquiring extra-personal and observable context such as location, weather and activity. By comparison, only very little research has been completed acquiring intra-personal and perceived context, despite its usefulness and diverse applications such as healthcare, marketing and smart homes. In particular, one of the most important psychological factors in personalized service selection and provision is individual attitude. Hence, the purpose of this paper is to propose a novel methodology of acquiring individual attitude context data for a more sophisticated context-aware service. We developed a model based approach to estimate the positive feedback of target services and products based on individual stimuli, which are regarded as external context. Models and corresponding modules are collected from research models on attitudes. To show the feasibility of the ideas proposed in this paper, we developed and examined a prototype system through laboratory experiments. [Copyright &y& Elsevier]

Abstract: In this paper, the control system of the first Algerian microsatellite in orbit Alsat-1 is presented. Alsat-1 is a 3-axis stabilised microsatellite, using a pitch momentum wheel and yaw reaction wheel, with dual redundant 3-axis magnetorquers. A gravity gradient boom is employed to provide a high degree of platform stability. Two vector magnetometers and four dual sun sensors are carried in order to determine the attitude. This paper examines the low Earth orbit (LEO) control system requirements and design in the context of a real system, the Surrey Satellite Technology Limited (SSTL) advanced microsatellite platform and puts forward designs for the control system to match the advanced capability of the enhanced microsatellite platform. Numerical results show the effectiveness of the implementation. Comparison with in orbit results is presented to evaluate the performance of the control system during accurate Nadir pointing control. [Copyright &y& Elsevier]

Extending results from previous work by Bandikova et al. (2012) and Inacio et al. (2015), this paper analyzes Gravity Recovery and Climate Experiment (GRACE) star camera attitude measurement noise by processing inter-camera quaternions from 2003 to 2015. We describe a correction to star camera data, which will eliminate a several-arcsec twice-per-rev error with daily modulation, currently visible in the auto-covariance function of the inter-camera quaternion, from future GRACE Level-1B product releases. We also present evidence supporting the argument that thermal conditions/settings affect long-term inter-camera attitude biases by at least tens-of-arcsecs, and that several-to-tens-of-arcsecs per-rev star camera errors depend largely on field-of-view. [ABSTRACT FROM AUTHOR]

On the 12th of November 2014, The Rosetta Lander Philae became the first spacecraft to softly land on a comet nucleus. Due to the double failure of the cold gas hold-down thruster and the anchoring harpoons that should have fixed Philae to the surface, it spent approximately two hours bouncing over the comet surface to finally come at rest one km away from its target site. Nevertheless it was operated during the 57 h of its First Science Sequence. The FSS, performed with the two batteries, should have been followed by the Long Term Science Sequence but Philae was in a place not well illuminated and fell into hibernation. Yet, thanks to reducing distance to the Sun and to seasonal effect, it woke up at end of April and on 13th of June it contacted Rosetta again. To achieve this successful landing, an intense preparation work had been carried out mainly between August and November 2014 to select the targeted landing site and define the final landing trajectory. After the landing, the data collected during on-comet operations have been used to assess the final position and orientation of Philae, and to prepare the wake-up. This paper addresses the Flight Dynamics studies done in the scope of this landing preparation from Lander side, in close cooperation with the team at ESA, responsible for Rosetta, as well as for the reconstruction of the bouncing trajectory and orientation of the Lander after touchdown. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive attitude control algorithm is developed based on neural network for a satellite. The proposed attitude control is based on nonlinear modified Rodrigues parameters feedback control in the presence of unknown terms like external disturbances and actuator faults. In order to eliminate the effect of the uncertainties, a multilayer neural network with a new learning rule will be designed appropriately. In this method, asymptotic stability of the proposed algorithm has been proven in the presence of unknown terms based on Lyapunov stability theorem. Finally, the performance of the designed attitude controller is investigated by simulations. [ABSTRACT FROM AUTHOR]

Abstract: Consensus reaching processes are applied in group decision making problems to reach a mutual agreement among a group of decision makers before making a common decision. Different consensus models have been developed to facilitate consensus reaching processes. However, new trends bring diverse challenges in group decision making, such as the modelling of different types of information and of large groups of decision makers, together with their attitude to achieve agreements. These challenges require the capacity to deal with heterogenous frameworks, and the automation of consensus reaching processes by means of consensus support systems. In this paper, we propose a consensus model in which decision makers can express their opinions by using different types of information, capable of dealing with large groups of decision makers. The model incorporates the management of the group’s attitude towards consensus by means of an extension of OWA aggregation operators aimed to optimize the overall consensus process. Eventually, a novel Web-based consensus support system that automates the proposed consensus model is presented. [Copyright &y& Elsevier]

Abstract: An imperative factor in the identification of suitable wind-turbine locations and the subsequent development thereof is the general acceptance of the proposed wind turbines. In this perspective, the existing number of turbines is expected to be a driver of attitude. However, to date only a few studies have assessed the influence of the turbine density in the residential area has on attitude. The present paper sheds light on this issue and finds that attitude towards existing turbines is negatively related with the number of turbines encountered on a daily basis. If the respondents see more than five on-land turbines, they are less positive. However, conditional of seeing more than five turbines a day, opposition does not increase with increasing turbine encounters. These results suggest that the general long-run threshold for opposition towards wind turbines is five turbine encounters per day. [Copyright &y& Elsevier]

Abstract: An attitude determination and control system (ADCS) is critical to satellite attitude maneuvers and to the coordinate transformation from the inertial frame to the spacecraft frame. This paper shows specific sensors in the ADCS of the satellite mission FORMOSAT-3/COSMIC (F3/C) and the impact of the ADCS quality on orbit accuracy. The selection of main POD antenna depends on the beta angles of the different F3/C satellites (for FM2 and FM4) during the inflight phase. In particular, under the eclipse, alternative attitude sensors are activated to replace the Sun sensors, and such a sensor change leads to anomalous GPS phase residuals and a degraded orbit accuracy. Since the nominal attitude serves as a reference for ADCS, the 3-dimensional attitude-induced errors in reduced dynamic orbits over selected days in 2010 show 9.35, 10.78, 4.97, 5.48, 7.18, and 6.89cm for FM1–FM6. Besides, the 3-dimensional velocity errors induced by the attitude effect are 0.10, 0.10, 0.07, 0.08, 0.09, and 0.10 for FM1–FM6. We analyze the quality of the observed attitude transformation matrix of F3/C and its impact on kinematic orbit determination. With 249days of GPS in 2008, the analysis leads to the following averaged 3-dimensional attitude-induced orbit errors: 2.72, 2.62, 2.37, 1.90, 1.70, and 1.99cm for satellites FM1–FM6. Critical suggestions of geodetic payloads for the follow-on mission of F3/C are presented based on the current result. [Copyright &y& Elsevier]

Abstract: The coming European astrometry mission Gaia will set new standards for the accuracy of position and velocity of up to a billion objects in the universe. This implies an extensive effort in the processing of the measurement data at the highest possible level of physical fidelity. Studies related to the precursor Hipparcos have shown that the fully-dynamical modelling of the spacecraft''s attitude leads to significant improvements in the understanding of the spacecraft''s real behaviour in space and eventually in the high quality of the scientific results. As a consequence, the principle goal for Gaia is to get a thorough knowledge of the characteristics of the dynamic behaviour of the spacecraft and related parameters. By establishing a software for attitude and disturbance torque modelling, this knowledge will incorporate in the modelling of the attitude—to be ready well in advance of the launch. The Gaia ‘Dynamical Attitude Model’ (DAM) focuses on the development of a simulation software environment based on physical principles and effects, complemented by information from onboard software and hardware components to control the spacecraft''s motion in space. DAM contains accurate models for all essential parts of a spacecraft simulator to gain sufficient knowledge of the Gaia attitude characteristics in order to aim for a level of knowledge that would ultimately lead to an improvement in the attitude modelling and thus in the science results. This paper presents the major parts of the DAM and shows the steps in the development of a high-precision tool for simulating Gaia''s attitude. [Copyright &y& Elsevier]

Abstract: Presently, large quantities of waste mobile phones are being generated in Nigeria with a significant proportion in storage. This paper investigated the behavior of consumers in Nigeria towards this waste stream and their willingness to participate in waste mobile phones recycling. This study also assessed the willingness of consumer''s to pay for a more ‘environment friendlier’ phone – the so-called ‘green phone’. We performed a principal component analysis with varimax rotation in order to condense some of our questions into a smaller set of factors. We developed a model to estimate and explain the willingness to pay (WTP) a premium for ‘green’ cell phones. The model showed that the significant predictors of willingness to pay extra for green electronics include awareness and concern about the deteriorating environment, age, and the general attitude towards the environment. About 65% of the respondents are either ‘willing’ or ‘very willing’ to drop-off no-longer-in-use electronics at a nearby recycling facility. Majority of the respondents are also very willing to pay a premium for a green phone. Considering the increasing waste generation by this sector, it has become expedient that a recycling program be introduced for these potentially harmful waste materials. [Copyright &y& Elsevier]

• Entropy functions based on Perceived Uncertainty are introduced. • The extant entropy functions are special cases of the proposed functions. • Analysis of the special cases is performed. • Applicability in the real world decision-making is demonstrated. In this paper, new entropy functions are formulated based on an agent's perceived uncertainty that inevitably affects the agent's choice. The role of the decision-maker's (DM's) attitude is emphasized as one of the key determinants of such an entropy function. More specifically, new attitude-based variants of Shannon's, Pal & Pal, and Aggarwal's probabilistic entropies are introduced. The extant fuzzy entropies are also extended to consider the agent's specific attitude. The proposed entropy functions provide a wide range of entropy values with the conventional entropy functions as their special cases. The special cases of the proposed entropies are examined. The wide applicability of the proposed entropy functions in multi criteria decision making is highlighted. A case-study is included to showcase the usefulness of the proposed entropy functions in the real world. [ABSTRACT FROM AUTHOR]

Abstract: The paper analyses the dynamics of a spinning tethered formation where the tethered units are modelled as extended rigid bodies. The system, composed by two platforms linked by a flexible tether a few hundreds of meters long, constitutes the building block of more complex tethered architectures utilised in proposed space interferometry missions. The issue investigated herein is the transfer of a collimated beam from one platform to another in the presence of environmental perturbations and structural vibrations affecting the position and attitude of the two tethered units. We propose to damp residual oscillations and limit the effect of environmental torques with the aid of two passive dampers placed at the tether attachment point. When the damping system is properly tuned, this approach has the considerable advantage of rapidly bringing the system to a minimum energy configuration (zero residual vibrations) without any external control force. Numerical results show the effectiveness of the proposed control strategy and provide an important element towards the implementation of future space-based observatories and formation-flying demonstration mission based on tether-connected architectures. [Copyright &y& Elsevier]

Abstract: A rotation can be represented by a tensor which in turn can be parameterized by an angle of rotation and an axis of rotation. This paper presents the first systematic study of the class of rotation tensors which possess constant angular velocities. In addition to the expected rotations featuring constant axes of rotation and constant angular rates, the existence of two other types of rotation are shown. For these rotations, the time variation of the angle and axis of rotation are coupled by an integrable dynamical system. Although the temporal behavior of the axis and angle of rotation can be complex, it also demonstrated how the rotations can be considered as motions about the angular velocity vector. One of the methods used to show this result is based on an analogue to the geometry of a circular helix. The presence of the class of rotations in rigid body dynamics and twistless helical deformations of rods is also discussed. [Copyright &y& Elsevier]

The backbone of aiding inertial navigation systems by satellite navigation receivers is the data fusion of the subsystem outputs. Its conventional mechanization emerged from the classical, necessary aiding of inertial navigation systems and is based on linearized error models. Recent approaches therefore use directly the nonlinear kinematical equations of the rigid body motion. These methods lead to a simpler system structure as well as to smaller estimation error variances. To verify this statement, the paper presents a systematization of the different fusion schemes and a comparison between results of postprocessed flight test data. [Copyright &y& Elsevier]

As the impacts of climate change become increasingly visible across the globe, awareness of the need for cleaner energy and demand reduction is growing. Energy literacy offers a strong potential for explaining and predicting energy-related behaviours, yet research and policies focused on this topic remain limited. In this study, energy literacy was measured in a sample of 2806 university students in the United Kingdom and China, in addition to their wider environmental attitudes using the New Ecological Paradigm scale. Findings indicate that energy literacy was relatively high overall, but there were significant differences between the knowledge, attitudes and behavioural intentions of participants in the two countries. Whilst the UK respondents rated themselves significantly more highly on perceived knowledge of energy issues, Chinese respondents provided significantly more correct answers in a knowledge test. UK respondents demonstrated more positive attitudes towards energy conservation than those from China, and were more likely to report energy-saving behaviours. However, Chinese respondents exhibited higher levels of trust in government and businesses to take action on energy issues. This paper provides a novel insight into cultural differences which may be crucial to policy and practice, and evidences the potential benefits of utilising a combination of educational and structural change to support transition to a cleaner, low-energy society. Image 1 • Significant differences in energy literacy arose in 1806 students in UK and China. • Chinese respondents demonstrated more knowledge about energy than UK respondents. • UK respondents demonstrated more positive attitudes and energy saving behaviours. • Cultural context, including trust in government impacts on energy-saving behaviours. • Combining educational and structural change will aid transition to a cleaner world. [ABSTRACT FROM AUTHOR]