Attitude Control

Small Satellites are establishing themselves as important tools for exploring our solar system. Developments in micro-electronics have enabled small and low-cost deep space probes to complement conventional space platforms in long-duration deep space missions. The paper presents a baseline design of an attitude control system for a spacecraft performing a Near Earth Object (NEO) fly-by mission. Following the autonomous escape and cruise phases, the NEO encounter phase is the most critical mission phase with the attitude control performed by a cluster of small Control Moment Gyros (CMG’s). The satellite needs to be rotated relatively fast to keep the NEO within its field of view for the imaging of the NEO. Simulations demonstrate the practicality and versatility on the use of CMGs for low-cost NEO deep space missions.

A new spacecraft attitude estimation approach based on the Unscented Filter is derived. For nonlinear systems the Unscented Filter uses a carefully selected set of sample points to more accurately map the probability distribution than the linearization of the standard Extended Kalman Filter, leading to faster convergence from inaccurate initial conditions in attitude estimation problems. The filter formulation is based on standard attitude-vector measurements using a gyro-based model for attitude propagation. The global attitude parameterization is given by a quaternion, while a generalized three-dimensional attitude representation is used to define the local attitude error. A multiplicative quaternion-error approach is derived from the local attitude error, which guarantees that quaternion normalization is maintained in the filter. Simulation results indicate that the Unscented Filter is more robust than the Extended Kalman Filter under realistic initial attitude-error conditions. ...

Since its launch into low-Earth orbit in June 1999, the mission of the Far Ultraviolet Spectroscopic Explorer (FUSE) has been to obtain high resolution far ultraviolet (905-1187 Å) spectra of a wide variety of astronomical sources. In late 2001, two of FUSE's four reaction wheels failed, compromising the ability to control spacecraft pointing. The FUSE Project adapted by developing a

Combining sliding mode control method with radial basis function
neural network (RBFNN), this paper proposes a robust adaptive
control scheme based on backstepping design for re-entry attitude
tracking control of near space hypersonic vehicle (NSHV) in the
presence of parameter variations and external disturbances. In the
attitude angle loop, a robust adaptive virtual control law is
designed by using the adaptive method to estimate the unknown
upper bound of the compound uncertainties. In the angular velocity
loop, an adaptive sliding mode control law is designed to suppress
the effect of parameter variations and external disturbances. The
main benefit of the sliding mode control is robustness to
parameter variations and external disturbances. To further improve
the control performance, RBFNNs are introduced to approximate the
compound uncertainties in the attitude angle loop and angular
velocity loop, respectively. Based on Lyapunov stability theory,
the tracking errors are shown to be asymptotically stable.
Simulation results show that the proposed control system attains a
satisfied control performance and is robust against parameter
variations and external disturbances.

Citation: Jingmei Zhang, Changyin Sun, Ruimin Zhang, Chengshan
Qian. Adaptive sliding mode control for re-entry attitude of near
space hypersonic vehicle based on backstepping design. IEEE/CAA
Journal of Automatica Sinica, 2015, 2(1): 94-101

The paper deals with the issue of developing an attitude control system for a remotely operated vehicle (ROV) for large inclination angles (pitch, roll). The construction of the orientation control system is considered based on the traditional approach using Euler angles (yaw, pitch and roll). A transfer matrix general form of the ROV attitude control system was obtained. It was shown that with the increase of inclination angles the transfer matrix of the system becomes multivariable. Algorithms of disturbances compensation and a methodology for parameters selection for decomposition algorithm were proposed. The obtained results were verified during the in situ tests of the ROV “Iznos”, developed in Bauman Moscow State Technical University (BMSTU). The proposed decomposition algorithms allow to expand the ranges of working angles and to improve the quality of the control system performance without significant re-engineering of its structure.

This paper analyses the possibility of exploiting a small spacecrafts constellation around Mars to ensure a complete and continuous coverage of the planet, for the purpose of supporting future human and robotic operations and taking advantage of optical transmission techniques. The study foresees such a communications mission to be implemented at least after 2020 and a high data-rate requirement is imposed for the return of huge scientific data from massive robotic exploration or to allow video transmissions from a possible human outpost.In addition, the set-up of a communication constellation around Mars would give the opportunity of exploiting this multi-platform infrastructure to perform network science, that would largely increase our knowledge of the planet.The paper covers all technical aspects of a feasibility study performed for the primary communications mission. Results are presented for the system trade-offs, including communication architecture, constellation configuration and transfer strategy, and the mission analysis optimization, performed through the application of a multi-objective genetic algorithm to two models of increasing difficulty for the low-thrust trajectory definition.The resulting communication architecture is quite complex and includes six 530 kg spacecrafts on two different orbital planes, plus one redundant unit per plane, that ensure complete coverage of the planet’s surface; communications between the satellites and Earth are achieved through optical links, that allow lower mass and power consumption with respect to traditional radio-frequency technology, while inter-satellite links and spacecrafts-to-Mars connections are ensured by radio transmissions. The resulting data-rates for Earth–Mars uplink and downlink, satellite-to-satellite and satellite-to-surface are respectively 13.7 Mbps, 10.2 Mbps, 4.8 Mbps and 4.3 Mbps, in worst-case.Two electric propulsion modules are foreseen, to be placed on a C3∼0 escape orbit with two Zenith Sea Launch rockets in March 2021 and carrying four satellites each. After the entrance in Mars sphere of influence, the single spacecrafts separate and spiral-down with Hall effect thrusters until they reach the final operational orbits in April 2025, at 17,030 km of altitude and 37 deg of inclination. The preliminary design includes 105 kg and 577 W of mass and power margin for each satellite, that can be allocated for scientific payloads.The main challenges of the proposed design are represented by the optical technology development and the connected strict pointing constraints satisfaction, as well as by the Martian constellation operations management.This mission study has therefore shown the possibility of deploying an effective communication infrastructure in Mars orbit employing a small amount of the resources needed for the human exploration programme, additionally providing the chance of performing important scientific research either from orbit or with a network of small rovers carried on-board and deployed on the surface.

Abstmct: This study presents a method to control the attitude of spacecraft using only magnetorquers without the gravity gradient boom. The main challenge is that the control torque can only be generated perpendicular to the geomagnetic field. If the dynamic model is expressed in the ...

A novel robust fault tolerant controller is developed for the problem of attitude control of a quadrotor aircraft in the presence of actuator faults and wind gusts in this paper. Firstly, a dynamical system of the quadrotor taking into account aerodynamical effects induced by lateral wind and actuator faults is considered using the Newton-Euler approach. Then, based on active disturbance rejection control (ADRC), the fault tolerant controller is proposed to recover faulty system and reject perturbations. The developed controller takes wind gusts, actuator faults and measurement noises as total perturbations which are estimated by improved extended state observer (ESO) and compensated by nonlinear feedback control law. So, the developed robust fault tolerant controller can successfully accomplish the tracking of the desired output values. Finally, some simulation studies are given to illustrate the effectiveness of fault recovery of the proposed scheme and also its ability to attenuate external disturbances that are introduced from environmental causes such as wind gusts and measurement noises.

The design and experimental control of an unmanned Tilt-Rotor aerial vehicle operating in Bi-Rotor mode is presented in this article. Tilt-Rotor UAVs exhibit important flight characteristics due to their ability to fly both like a rotorcraft (in Bi-Rotor Mode) and like a fixed-wing aerial system. The ability of having a dual flight envelope makes ideal for complex missions where both the speed and flight endurance of a fixed-wing design and the hovering, aggressive maneuvering and vertical take-off/landing capabilities of a helicopter ...