Browse Topic: Attitude control
The presence of a slung-load during the flight of a quadrotor generates swing effects that can greatly influence the dynamics of the quadrotor. These effects have the potential to threaten the stability of the system’s attitude. This study presents a disturbance compensation strategy that is designed based on the utilization of an adaptive harmonic extended state observer (AHESO) in order to solve this problem and achieve precise attitude control. To derive the aforementioned algorithm, a comprehensive mathematical model for the quadrotor-slung-load system is built. The periodic features of disturbance are derived by considering the movement of the slung-load. Subsequently, by taking the periodic features of the disturbances into account, the AHESO for accurate disturbance estimation is designed. In this observer, an online frequency estimator for the harmonic disturbances is introduced. Lyapunov theory is introduced to examine the stability of the AHESO. In addition, backstepping
This document provides recommended practices regarding how System Theoretic Process Analysis (STPA) may be applied to safety-critical systems in any industry
In the field of space technology, Centre Suisse d’Electronique et de Microtechnique (CSEM) has been a partner of the European Space Agency (ESA) for many years. One focus of their joint research is eliminating vibration emissions originating from components aboard satellites. In addition to limiting the precision of attitude control for satellites, these micro-vibrations lead to higher energy consumption and (in the case of imaging missions) cause deterioration of image quality
These recommendations cover the mechanical and electrical installation and installation test procedures for automatic pilots of the type normally used in transport type aircraft. The material in this ARP does not supercede any airworthiness requirement in the Civil Air Regulations
When firing artillery, there is typically a maximum angle that the platform cannot exceed relative to the Earth plane. This is due to the large recoil forces involved and the risk of destabilizing the platform the weapon is mounted to. Mobile systems are particularly sensitive to this as the attitude of the platform relative to Earth is constantly changing. A simple solution is to add pitch and roll sensors directly to the platform. However, many mobile systems already have an assortment of sensors that can be used to calculate the platform attitude
NASA’s Small Spacecraft Technology Program is on the countdown clock to advance communications and proximity maneuvering capabilities for CubeSats with the Integrated Solar Array and Reflectarray Antenna (ISARA) mission
In designing of the Attitude Control System (ACS) is important take into account the influence of the structure’s flexibility, since they can interact with the satellite rigid motion, mainly, during translational and/or rotational maneuver, damaging the ACS pointing accuracy. In the linearization and reduction of the rigid-flexible satellite mathematic model, usually one loses some important information associated with the satellite true dynamical behavior. One way to recovery this information is include to the ACS design parametric and not parametric uncertainties of the system. The H infinity control method is able to take into account the parametric uncertainty in the control law design, so the controller becomes more robust. This paper presents the design of a robust controller using the H infinity control technique to control the attitude of a rigid-flexible satellite. The satellite model is represented by a flexible beam connected to a central rigid hub considering a set of
Typical spacecraft thruster configurations are often unable to provide full six-degree-of-freedom control and may have unwanted interaction between their attitude control and trajectory control functions, have undesirably high instantaneous electrical power demands, and use more thrusters than desirable. These last two potential problems gain increased significance if a spacecraft is required to have especially small size and mass, and have very low cost
Preliminary data was recently provided for a reaction sphere prototype on NASA’s zero-gravity parabolic flight vehicle. Gyroscope telemetry indicates that reaction spheres were successfully commanded at 10- to 20-ms pulses during a handful of parabolas in each flight. This is the first publicly disclosed validation of a freely rotating reaction sphere in a standalone compact package. At dimensions of
This study is made on a simplified pitch model of an armored fighting vehicle. Jerks and angular acceleration inside the vehicle compartment Affects accurate firing attack and reduced fatigue to the occupants in Vehicle. The Stability Augmentation Technique can enhance the stability and ride comfort of the vehicle platform from road and firing disturbance. The force requirement for stabilizing the platform is calculated from the displacement of vehicle body in terms of pitch angle and Heave displacement with respect to the equilibrium position, the equivalent force at suspension mounting points required to stabilize the platform is calculated using a force transformation technique. The required force is given by an active Damper for stabilization, within the limit of damper capacity. From simulation conducted and comparison with passive suspension it is perceived that the Stability of vehicle platform is increased together with a reduced VDV (Vibration Dose Value) and rms acceleration
Various gas systems are classified in a broad sense, component operation is described in moderate detail, pertinent design parameters are discussed, and possible modes for system operation are listed
A paper describes a process for imposing safety constraints on a spacecraft trajectory design. The conventional process has the ACS (Attitude Control System) team define geometric constraints, then the NAV (Navigation) team produces a compliant thrust direction profile for the spacecraft to execute. With time-varying thrust profiles, merely specifying geometric constraints is not sufficient. Because low thrust implies low agility under thrust vector control (TVC), even slowly developing spacecraft dynamics can be significant and geometric constraints can have dynamic implications. The thrust profile design process was modified to incorporate a new tool, known as qSTAT, which analyzes candidate thrust profiles for compliance with geometric and dynamic constraints by simulating an appropriately reduced set of spacecraft dynamics. qSTAT gives the navigation team a simplified attitude control simulation tool that can quickly be used to analyze multiple candidate thrust profile designs. The
A report describes a model that estimates the orientation of the backup reaction wheel using the reaction wheel spin rates telemetry from a spacecraft. Attitude control via the reaction wheel assembly (RWA) onboard a spacecraft uses three reaction wheels (one wheel per axis) and a backup to accommodate any wheel degradation throughout the course of the mission. The spacecraft dynamics prediction depends upon the correct knowledge of the reaction wheel orientations. Thus, it is vital to determine the actual orientation of the reaction wheels such that the correct spacecraft dynamics can be predicted
A landing gear system comprises the most compelling assembly of engineering skills. Its importance to the successful design of an aircraft can be favorably compared with that of the aircraft's wings and engines. A landing gear system consists of several different engineering disciplines, and is continually in the public eye especially with regard to safety. The primary objective of AIR4846 is to present a record of a variety of interesting gears, gear/aircraft systems and patents, and to discuss wherever possible the lessons learned, and the reasons for the design. Thus, the document is not only a historical account, but a means of recording technical knowledge for the practical benefit of future landing gear designers. Commendable efforts have been made over the years by several individuals to make such recordings, and AIR4846 will make continual reference to them. This applies to all books, papers, or specifications that have the approval of the SAE A-5 Committee. AIR4846 also
Hybrid systems are characterized by a composition of discrete and continuous dynamics. In particular, the system has a continuous evolution and occasional jumps. The jumps are caused either by controllable, uncontrollable external events or by its continuous evolution. Inevitably, this type of system is present in mobility devices such as cars, ships, and aircrafts. Efforts to develop this type of system have increasingly suffered from cost and schedule overruns. In fact, the verification of such systems has become a key activity in the development life cycle. Historically, such activity demands experts and high efforts, and uses ad-hoc methods. Therefore, the aim of this work is to apply finite state-machine verification to hybrid systems. To do that, a small part of the vast theory of automatic test suite generation for this type of discrete behavior and system is applied in a model-based testing approach, showing an effective and reproducible alternative for automatic test suite
This document sets forth design and operational recommendations concerning the human factors issues and criteria for airborne terrain separation assurance systems. The visual and aural characteristics are covered for both the alerting components and terrain depiction/situation components. The display system may contain any one or a combination of these components. Although the system functionality assumed for this document exemplifies commercial aircraft implementation, the recommendations do not exclude other fixed wing aircraft types. Because of their unique operations with respect to terrain, rotorcraft will be addressed in a separate document. The assumptions about the system that guided and bounded the recommendations included: the system will have a human centered design based on the "lessons learned" from past systems; the system is not intended to replace the Ground Proximity Warning System (GPWS) function; the system is an on-board system that is not dependent on ground
A paper describes attitude-control algorithms using the combination of magnetic actuators with reaction wheel assemblies (RWAs) or other types of actuators such as thrusters. The combination of magnetic actuators with one or two RWAs aligned with different body axis expands the two-dimensional control torque to three-dimensional. The algorithms can guarantee the spacecraft attitude and rates to track the commanded attitude precisely
This paper presents and investigates different passive methods for reducing the notorious instability of discoid aerial vehicles. Presented methods are completely passive and involve elementary causes such as aerodynamic forces and gravitational effects. Four different system attitude control methods are presenting for different shapes and constructive solutions
A patent disclosure document discusses a photonic method for connecting a spacecraft with a launch vehicle upper-stage telemetry system as a means for monitoring a spacecraft’s health and status during and right after separation and deployment. This method also provides an efficient opto-coupled capability for prelaunch built-in-test (BIT) on the ground to enable more efficient and timely integration, preflight checkout, and a means to obviate any local EMI (electromagnetic interference) during integration and test. Additional utility can be envisioned for BIT on other platforms, such as the International Space Station (ISS
This study proposes a novel semi-active hydro-pneumatic suspension design and investigates its performance potentials. The proposed new semi-active suspension design involves pneumatic interconnection between the front and rear suspension struts of the vehicle. The analytical formulations of suspension forces due to two suspension configurations, a passive unconnected and the proposed semi-active interconnected, are derived to analyze suspension properties. Based on a validated pitch-plane vehicle braking model, vehicle dynamic responses are conducted under a range of measured road roughness excitations and driving speeds, as well as braking inputs. The results of fundamental suspension properties and vehicle responses demonstrate the considerably potentials of the proposed novel semi-active suspension in improving vehicle pitch ride, pitch attitude control, and road-friendliness under random road excitations, without influencing vehicle vertical ride, and pitch attitude control when
Software has been designed to schedule remote sensing with the Earth Observing One spacecraft. The software attempts to satisfy as many observation requests as possible considering each against spacecraft operation constraints such as data volume, thermal, pointing maneuvers, and others. More complex constraints such as temperature are approximated to enable efficient reasoning while keeping the spacecraft within safe limits. Other constraints are checked using an external software library. For example, an attitude control library is used to determine the feasibility of maneuvering between pairs of observations. This innovation can deal with a wide range of spacecraft constraints and solve large scale scheduling problems like hundreds of observations and thousands of combinations of observation sequences
Items per page:
50
1 – 50 of 163