Attitude Representation Research Articles

Defensive representations of an uncomfortable history: The case of Hungary and the Holocaust

The current research examines how representations of a traumatic history influence contemporary intergroup attitudes. Specifically, we examine antisemitism in Hungary as a case example of how the need to defend the group's moral image motivates the assumption of a defensive representation of history − a modification of the group's narrative with regards to its culpability in past atrocities committed against another group. Two studies examined the link between defensive representations of the Holocaust, nationalism, and antisemitism. In the first, correlational study (N=348), we found that Hungarian nationalism and antisemitism were associated, and that this association was significantly mediated by defensive representations of the Holocaust – high nationalism was associated with higher endorsement of defensive representations which in turn were associated with more antisemitism. Low nationalism was associated with greater acknowledgement of in-group responsibility for historical crimes which was associated with less antisemitism. These findings were corroborated in an experimental study (N=165) which indicated that priming defensive representations of the Holocaust increased antisemitism, even when controlling for nationalism. Study 2 further showed, in a 2-step mediation model, that defensive representation primes increased secondary antisemitism, conspiratorial antisemitism, and negative attitudes towards Israel. We discuss the implications of defensive representations of history on contemporary intergroup relations.

Self-Tuning Geometric Control for a Quadrotor UAV Based on Lyapunov Stability Analysis

A Lyapunov-based self gain tuning geometric nonlinear controller for a quadrotor UAV has been developed on SE(3) in this paper. By designing an adaptive law with Lyapunov stability analysis for the controller gains, the proposed control system can asymptotically follow an attitude and position command while tuning the PID gains online, and it is extended to guarantee boundedness of tracking errors in the presence of unstructured disturbances. This introduce an unprecedented algorithm to autonomously tune the controller gains without need of extra effort or introducing boundary conditions. Proposed controller considers all the coupling effects between rotational and translational dynamics, and it is developed in a coordinate-free fashion to avoid complexities and ambiguities associated with other attitude representations such as Euler angles or quaternions. The desirable features of the proposed controller are illustrated by numerical simulations and juxtaposed with a well-known offline gain tuning method. The proposed algorithm is ultimately validated with an experimental example.

Finite-time output feedback attitude control for rigid spacecraft under control input saturation

In this paper, the problem of finite-time output feedback attitude control for rigid spacecraft subject to control input saturation is investigated. For the attitude stabilization, we propose a nonlinear finite-time observer using quaternion-based attitude representation. The estimated attitude of the observer always satisfies the unit norm constraint. The finite-time stability of the observer can be guaranteed by using homogeneous and Lyapunov methods. Furthermore, the effect of the external disturbance on the performance of the finite-time observer is analyzed. With the finite-time observer, we design an attitude stabilizing control law to guarantee that the attitude state of the spacecraft converges to the equilibrium point in finite time. We also discuss the finite-time attitude tracking control for spacecraft and propose a control scheme without requiring angular velocity measurements to guarantee that the desired attitude can be tracked in finite time. The main novelty of the control algorithms derived here lies in the fact that finite-time stability can be achieved even in the absence of angular velocity measurements as well as in the presence of constraints on control input magnitude. Numerical examples are presented to demonstrate the efficiency of the proposed control algorithms.

Robust adaptive relative motion control for spacecraft proximity operations

This paper studies the controller design for a spacecraft approaching a tumbling space target in the presence of model uncertainties and dynamic couplings between relative rotation and relative translation. An alternative relative attitude function is selected to measure the magnitude of the relative attitude motion carefully, and robust adaptive controllers are designed for relative attitude and relative position to guarantee a desirable stabilization performance uniformly for the relative motion. The strict Lyapunov analysis is presented to prove the uniformly ultimately boundedness of relative motion errors. The relative attitude controller is directly developed on the special orthogonal group SO(3) to avoid complexities and ambiguities associated with coordinate-dependent attitude representations. Performance of the controlled overall system is demonstrated via a representative numerical example.

The J. Fodor's language of thought hypothesis and epistemic logic

The study is to show the similarities between J. Fodor's Language of Thought hypothesis and epistemic modal logic. According to the J. Fodor's hypothesis there is the language of thought (also called Mentalese) that is the meta-language in which mental representations of attitudes of organism to propositions expressed in object-language (for example: knowledge, belief, hope, desire, statement) are formulated. These attitudes are called attitudes. In the hypothesis propositional attitudes are thoughts and relations between organism and proposition. Propositional attitudes are of interest for epistemic modal logics. In epistemic logics propositional attitudes are relations considered as modalities, i.e. propositions with modal operators. On certain conditions J. Fodor's Language of Thought hypothesis may be considered as a sort of epistemic modal logic, only it would require certain updating as a formal logical system. The similarities between J. Fodor's Language of Thought and epistemic modal logics give two opportunities. First opportunity is to make special version of epistemic modal logic as an instrument of research for cognitive psychology based on J. Fodor's Language of Thought hypothesis. Second opportunity is to accept the idea of J. Fodor's Language of Thought as an innate language and to attain comprehension that epistemic modal logics are not especially constructed formal languages (formal systems) but innate cognitive programs. It might enable to extrapolate the idea of innate languages onto all formal languages including logical languages and to attempt verifying that idea experimentally within cognitive sciences.

Strapdown Inertial Navigation Algorithms Based on Lie Group

This paper presents a framework for a strapdown Inertial Navigation System (INS) algorithm design by using Lie group and Lie algebra. The general way to solve Lie group differential equations is introduced. Investigations reveal that this general Lie group method provides a simpler unified way to solve differential equations involving direction cosine matrix, quaternion and dual quaternion, which are widely used in INS algorithm design. Furthermore, we also present a new INS algorithm based on the Special Euclidean group se(3) under the guidelines of Lie group method. Analyses show that se(3) algorithm has the same accuracy as a dual quaternion algorithm, this is also justified by numerical simulations. Though the se(3) algorithm has no improvements in accuracy, the general Lie group method used in the design process shows its brevity and uniformity.

Possible Biases of Researchers' Attitudes Toward Video Games: Publication Trends Analysis of the Medical Literature (1980-2013).

BackgroundThe study of video games is expanding, and so is the debate regarding their possible positive and deleterious effects. As controversies continue, several researchers have expressed their concerns about substantial biases existing in the field, which might lead to the creation of a skewed picture, both in the professional and in the lay literature. However, no study has tried to examine this issue quantitatively.ObjectiveThe objective of our study was to examine possible systematic biases in the literature, by analyzing the publication trends of the medical and life sciences literature regarding video games.MethodsWe performed a complete and systematic PubMed search up to December 31, 2013. We assessed all 1927 articles deemed relevant for their attitude toward video games according to the focus, hypothesis, and authors’ interpretation of the study results, using a 3-category outcome (positive, negative, and neutral). We assessed the prevalence of different attitudes for possible association with year of publication, location of researchers, academic discipline, methodological research, and centrality of the publishing journals.ResultsThe attitude toward video games presented in publications varied by year of publication, location, academic discipline, and methodological research applied (P<.001 for all). Moreover, representation of different attitudes differed according to centrality of the journals, as measured by their impact factor (P<.001).ConclusionsThe results suggest that context, whether scientific or social, is related to researchers’ attitudes toward video games. Readers, both lay and professional, should weigh these contextual variables when interpreting studies’ results, in light of the possible bias they carry. The results also support a need for a more balanced, open-minded approach toward video games, as it is likely that this complex phenomenon carries novel opportunities as well as new hazards.

Singularity-free backstepping controller for model helicopters

This paper develops a backstepping controller for model helicopters to achieve trajectory tracking without singularity, which occurs in the attitude representation when the roll or pitch reaches ±π2. Based on a simplified model with unmodeled dynamics, backstepping technique is introduced to exploit the controller and hyperbolic tangent functions are utilized to compensate the unmodeled dynamics. Firstly, a position loop controller is designed for the position tracking, where an auxiliary dynamic system with suitable parameters is introduced to warrant the singularity-free requirement for the extracted command attitude. Then, a novel attitude loop controller is proposed to obviate singularity. It is demonstrated that, based on the established criteria for selecting controller parameters and desired trajectories, the proposed controller realizes the singularity-free trajectory tracking of the model helicopter. Simulations confirm the theoretical results.

Determinig of an object orientation in 3D space using direction cosine matrix and non-stationary Kalman filter

Abstract This paper describes a method which determines the parameters of an object orientation in 3D space. The rotation angles calculation bases on the signals fusion obtained from the inertial measurement unit (IMU). The IMU measuring system provides information from a linear acceleration sensors (accelerometers), the Earth’s magnetic field sensors (magnetometers) and the angular velocity sensors (gyroscopes). Information about the object orientation is presented in the form of direction cosine matrix whose elements are observed in the state vector of the non-stationary Kalman filter. The vector components allow to determine the rotation angles (roll, pitch and yaw) associated with the object. The resulting waveforms, for different rotation angles, have no negative attributes associated with the construction and operation of the IMU measuring system. The described solution enables simple, fast and effective implementation of the proposed method in the IMU measuring systems.

Rita Felski. The Limits of Critique. Chicago: University of Chicago Press, 2015. 232 pp.

Previous articleNext article No AccessThe CI ReviewRita Felski. The Limits of Critique. Chicago: University of Chicago Press, 2015. 232 pp.Davide PanagiaDavide Panagia Search for more articles by this author PDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Critical Inquiry Volume 42, Number 4Summer 2016 Article DOIhttps://doi.org/10.1086/686957 Views: 827Total views on this site © 2016 by The University of Chicago. All rights reserved.PDF download Crossref reports no articles citing this article.

Smooth finite-time fault-tolerant attitude tracking control for rigid spacecraft

This paper investigates the problem of attitude tracking control for a rigid spacecraft subject to parametric uncertainties, external disturbances, actuator faults and actuator saturation constraints. By combining the finite-time passivity technique into adaptive sliding mode control approach, a novel smooth fault-tolerant control algorithm with finite time convergence is proposed. Then, the finite-time convergence of the relative attitude errors will be achieved by implementing the proposed smooth fault-tolerant controller, even under actuator faults and magnitude constraints. In particular, a solution to the unwinding phenomenon, arising from the usage of the redundant four-parameter attitude representation, is explored in the sense of finite-time passivity. Besides detailed controller design procedures and rigorous theoretical proofs of all related closed-loop finite-time stability, numerical simulation results are exhibited to demonstrate the effectiveness and superior control performance of the proposed control scheme.

Inertial measurement unit based indoor localization for construction applications

Abstract Localization and tracking of resources on construction jobsites are an emerging area where the location of materials, labor, and equipment is used to estimate productivity, measure project's progress and/or enhance jobsite safety. GPS has been widely used for outdoor tracking of construction operations. However, GPS is not suitable for indoor applications due to the lack of signal coverage; particularly inside tunnels or buildings. Several indoor localization research studies had been attempted, however such developments rely heavily on extensive external communication network infrastructures. These developments also are susceptible to electromagnetic interference in noisy construction jobsites. This paper presents indoor localization system using a microcontroller equipped with an inertial measurement unit (IMU). The IMU contains a cluster of sensors: accelerometer, gyroscope and magnetometer. The microcontroller uses a direct cosine matrix algorithm to fuse sensors data and calculate non-gravitational acceleration using nine-degrees-of-freedom motion equations. Current position is calculated based on measured acceleration and heading, while accounting for growing error in speed estimation utilizing jerk integration algorithm. Experimental results are presented to illustrate the relative effectiveness of the developed system, which is able to operate independently of any external aids and visibility conditions.

Results of the attitude reconstruction for the UniSat-6 microsatellite using in-orbit data

UniSat-6 is a civilian microsatellite that was launched in orbit on the 19th of June, 2014. Its main mission consisted in the in-orbit release of a number of on-board carried Cubesats and in the transmission to the UniSat-6 ground station of telemetry data and images from an on-board mounted camera. The spacecraft is equipped with a passive magnetic attitude control system. Gyros and magnetometers provide the information about the attitude of the spacecraft.The importance of reconstructing the attitude motion of UniSat-6 lies in the dual possibility, for future missions, of:•controlling the direction of ejection of the on-board carried satellites•having an accurate pointing for remote sensing operation.The reconstruction of the attitude motion of UniSat-6 is based on the data of the on-board Commercial Off The Shelf (COTS) gyros and magnetometers, downloaded at the passages over the ground station in Roma, Italy. At ground, these data have been processed with the UnScented QUaternion Estimator (USQUE) algorithm. This estimator is an adaptation of the Unscented Filter to the problem of spacecraft attitude estimation. The USQUE is based on a dual attitude representation, which involves both quaternions and Generalized Rodrigues Parameters. In this work, the propagation phase of the algorithm contains only a kinematic model of the motion of the spacecraft.This paper presents the results of the reconstruction of the UniSat-6 attitude using on-board measurements. The results show that the spacecraft effectively stabilized its attitude motion thanks to the on-board magnetic devices.

Particle Filter with Novel Nonlinear Error Model for Miniature Gyroscope-Based Measurement While Drilling Navigation.

The derivation of a conventional error model for the miniature gyroscope-based measurement while drilling (MGWD) system is based on the assumption that the errors of attitude are small enough so that the direction cosine matrix (DCM) can be approximated or simplified by the errors of small-angle attitude. However, the simplification of the DCM would introduce errors to the navigation solutions of the MGWD system if the initial alignment cannot provide precise attitude, especially for the low-cost microelectromechanical system (MEMS) sensors operated in harsh multilateral horizontal downhole drilling environments. This paper proposes a novel nonlinear error model (NNEM) by the introduction of the error of DCM, and the NNEM can reduce the propagated errors under large-angle attitude error conditions. The zero velocity and zero position are the reference points and the innovations in the states estimation of particle filter (PF) and Kalman filter (KF). The experimental results illustrate that the performance of PF is better than KF and the PF with NNEM can effectively restrain the errors of system states, especially for the azimuth, velocity, and height in the quasi-stationary condition.

Unscented Kalman Filter for Determination of Spacecraft Attitude Using Different Attitude Parameterizations and Real Data

The non-linear estimators are certainly the most important algorithms applied to real problems, especially those involving the attitude estimation of spacecraft. The purpose of this paper was to use real data of sensors to analyze the behavior of Unscented Kalman Filter (UKF) in attitude estimation problems when it is represented in different ways and compare it with the standard estimator for non-linear estimation problems. The robustness of the estimation was performed when this was subjected to imprecise initial conditions. The attitude parametrization was described in Euler angles, quaternion and quaternion incremental. The satellite China-Brazil Earth Resources Satellite and measurements provided by the Satellite Control Center of the Instituto Nacional de Pesquisas Espaciais were considered in the study. The results indicate that the behaviors for both estimators were equivalent for such parameterizations under the same conditions. However, comparing the Unscented Kalman Filter with the standard filter for non-linear systems, Extended Kalman Filter (EKF), it was observed that, in the presence of inaccurate initial conditions, the Unscented Kalman Filter presented a fast convergence whereas Extended Kalman Filter had problems and only converged later on.

Nonlinear Attitude Control of Spacecraft with a Large Captured Object

This paper presents an attitude control strategy and a new nonlinear tracking controller for a spacecraft carrying a large object, such as an asteroid or a boulder. If the captured object is larger or comparable in size to the spacecraft and has significant modeling uncertainties, conventional nonlinear control laws that use exact feedforward cancellation are not suitable because they exhibit a large resultant disturbance torque. The proposed nonlinear tracking control law guarantees global exponential convergence of tracking errors with finite-gain stability in the presence of modeling uncertainties and disturbances, and it reduces the resultant disturbance torque. Furthermore, this control law permits the use of any attitude representation, and its integral control formulation eliminates any constant disturbance. Under small uncertainties, the best strategy for stabilizing the combined system is to track a fuel-optimal reference trajectory using this nonlinear control law because it consumes the least amount of fuel. In the presence of large uncertainties, the most effective strategy is to track the derivative plus proportional–derivative-based reference trajectory because it reduces the resultant disturbance torque. The effectiveness of the proposed attitude control methods is demonstrated by using results of numerical simulation based on an Asteroid Redirect Mission concept.

Nonlinear Dynamic Inversion of a Flexible Aircraft

This paper investigates the use of dynamic inversion for the attitude control of a flexible aircraft. Input-output feedback linearization-based dynamic inversion is used to linearize the angular velocity and forward translational velocity equations of motion. A proportional-integral-derivative (PID) controller based on the direction cosine matrix (DCM) that describes the attitude of the aircraft is used, in addition to a proportional-integral (PI) controller to maintain a desired airspeed. Numerical simulations are performed using the proposed dynamic inversion controller, as well as more practical implementations of the controller that include saturated control inputs and no knowledge of the aircraft’s flexible states. In simulation, the practical controllers successfully stabilize a flexible aircraft with reasonable control surface deflections.

Micro-Satellite Attitude Determination with Only a Single Horizon Sensor

Through using measurement from only a single horizon sensor, this paper presented a quaternion-based 3-axis attitude determination method, which can be implemented on board micro-satellites and applied over a whole orbital period. Firstly, a description of attitude representation on the quaternion is given. Secondly, a detailed modeling formulation with nadir vector and measurement equations on attitude estimation system is demonstrated. Afterwards, a correction is made to eliminate the estimation error resulted from Earth’s oblateness, and able to further improve the accuracy of the attitude determination algorithm. Finally, a six degree-of-freedom closed-loop simulation is used to validate the accuracy of the attitude determination method given in this paper.

Motion trajectory of human arms based on the dual quaternion with motion tracker

In this paper, we present an algorithm for human motion capture of the real-time motion trajectory of human arms based on wireless inertial 3D motion trackers. It aims to improve the accuracy of inertial motion captures and quickly reconstruct some human movements. To evaluate the performance of the proposed dual quaternion algorithm, we present the prototype design. The wireless inertial measurement system and Kinect device are introduced simultaneously in capturing human motion. The dual quaternion algorithm incorporates features of the quaternion rotation and translation. So the singular points of Euler angles can be avoided. Dual quaternion algorithm and DCM(direction cosine matrix) are used to reconstruct human arm movements respectively. Compared with the computing speed in Matlab, the speed of the dual quaternion is faster than it of DCM. To the end, we propose a 3D ADAMS human robotic model for simulating the motion trajectory using dual quaternion algorithm. The results show that the dual quaternion can achieve capabilities of a positive DCM solving, which completed between body segments rotating and translating the coordinate system transformation. Also it can effectively drive in real-time a human model to animate movement, and provide a good algorithm.

A minimal logic for interactive epistemology

We propose a minimal logic for interactive epistemology based on a qualitative representation of epistemic individual and group attitudes including knowledge, belief, strong belief, common knowledge and common belief. We show that our logic is sufficiently expressive to provide an epistemic foundation for various game-theoretic solution concepts including “1-round of deletion of weakly dominated strategies, followed by iterated deletion of strongly dominated strategies” ( $$\hbox {DWDS}^1\hbox {-IDSDS}$$ ) and “2-rounds of deletion of weakly dominated strategies, followed by iterated deletion of strongly dominated strategies” ( $$\hbox {DWDS}^2\hbox {-IDSDS}$$ ). Axiomatization and complexity results for the logic are given in the paper.