Single-axis Attitude Control Research Articles

Single-axis attitude control for slew maneuvers with the keep-out zones

The problem of large angle slew maneuvers under the attitude restrictions is considered. The modification of the single axis Lyapunov feedback attitude control is proposed. It “locally” changes the standard attitude controller to accommodate the attitude restrictions avoidance. The problem of the unwanted equilibria appearance is thoroughly investigated. Different keep-out zones intersection cases are considered.

On robust LPV-based observation of fuel slosh dynamics for attitude control design

Most attitude control scenarios are highly affected by fuel slosh dynamics that must be carefully taken into account to preserve pointing accuracy. Since such dynamics are not easily predictable, standard strategies consist of bounding the performances of the control system to avoid interactions between the rigid dynamics of the spacecraft and the oscillating liquid motion inside the fuel tank. Thanks to a recently developed control-oriented CFD-based fuel slosh model, an alternative approach is evaluated in this paper. It is based on a reformulation of the slosh effects in the Linear-Parameter-Varying (LPV) framework from which a robust LPV observer is easily derived. The latter is then classically used in a disturbance compensation scheme. The proposed strategy is illustrated on a simple but realistic single axis attitude control scenario for a small satellite using reaction wheels.

Integrated power and single axis attitude control system with two flywheels

The existing research of the integrated power and attitude control system (IPACS) in satellites mainly focuses on the IPACS concept, which aims at solving the coupled problem between the attitude control and power tracking. In the IPACS, the configuration design of IPACS is usually not considered, and the coupled problem between two flywheels during the attitude control and energy storage has not been resolved. In this paper, an integrated power and single axis attitude control system using two counter rotating magnetically suspended flywheels mounted to an air table is designed. The control method of power and attitude control using flywheel is investigated and the coupling problem between energy storage and attitude control is resolved. A computer simulation of an integrated power and single axis attitude control system with two flywheels is performed, which consists of two counter rotating magnetically suspended flywheels mounted to an air rotary table. Both DC bus and a single axis attitude are the regulation goals. An attitude & DC bus coordinator is put forward to separate DC bus regulation and attitude control problems. The simulation results of DC bus regulation and attitude control are presented respectively with a DC bus regulator and a simple PD attitude controller. The simulation results demonstrate that it is possible to integrate power and attitude control simultaneously for satellite using flywheels. The proposed research provides theory basis for design of the IPACS.

모터와 프로펠러로 구성된 시소형 1축 자세 제어 실험에 관한 연구

본 연구에서는 쿼드로터형 비행체 개발을 위한 선행연구로서 1축 자세 제어장비를 개발하고, 시뮬레이션과 실험을 수행하였다. 두 개의 모터와 프로펠러로 구성된 시소형 1축 자세 제어장비가 제작되었고, 추력 시험을 통해 공력 파라메터를 도출하였다. Matlab/Simulink를 이용하여 시스템의 응답을 추정하였고, 자세 센서와 자세 제어 컴퓨터를 탑재하여 실험을 수행하였다. 시뮬레이션과 실험 데이터를 비교하여 실험 시 발생하는 정상상태 오차에 대한 원인을 파악하고, 사용된 자세알고리즘과 자세 제어 컴퓨터에 대한 성능 검증하였다. 본 과정을 통해, 쿼드로터형 무인항공기 자세 제어를 위한 선행 필수 기초자료를 획득하였다. In this research, a single-axis attitude control test bed is developed, and simulation and tests experiments are performed, as a preliminary research of a quad-rotor aerial vehicle development. A single-axis test bed with seesaw configuration is manufactured using two motors and propellers, and the aerodynamic parameters are derived by thrust tests. The response of the system is estimated with Matlab/Simulink, and experiments are performed with attitude control computer and an attitude sensor onboard the test bed. Comparing the results of simulated and tested data, factors of steady-state errors during experiments are found, and performances of used attitude control algorithm and the control computer were verified. In these process, essential preliminary data for attitude control of a quad-rotor unmanned aerial vehicle were acquired.

Integrated power and attitude control with two flywheels

Energy storage and attitude control are two distinct subsystems of the typical satellite. Energy storage is provided using batteries and active attitude control is accomplished with control moment gyroscopes or reaction wheels. A system mass savings can be achieved if these two subsystems are combined using multiple flywheels for simultaneous kinetic energy storage and momentum transfer. This paper develops, simulates, and experimentally demonstrates the control algorithms to accomplish integrated power and single-axis attitude control using two flywheels.

A gyro drift and dynamics state estimator for satellite attitude control systems utilizing a star mappert†

A recursive estimator is presented which, when given attitude measurements from a star mapper and rate integrating gyro, together with control signals, provides filtered estimates of gyro drift, disturbing angular acceleration, body angular velocity and attitude. Attention is restricted at present to satellites with substantially rigid body dynamics and negligible inter-axis coupling. A single axis attitude control system is considered, this being sufficient for demonstration of the principles. The estimator is based on the Kalman filter with the following developments ; (a) A low level fictitious covariance matrix element is introduced to facilitate estimation of the disturbing angular acceleration, and (b) the gain matrix is modified to enable the real-time model iterations and gyro sampling to be carried out at a much higher rate than the star mapper sampling. Furthermore, the part of the gain matrix relevant to the star mapper output is adapted to enable the correction to the model to be applied continuously, thereby avoiding stepping of the state estimate following new star mapper measurements. A form of the estimator is presented in which it is unnecessary to know the time to the next star mapper reading. Digital simulation results are given for a complete control system in which two control loops are completed by state-variable feedback, comprising a linear gyro-drift control law and a non-linear gas jet control law.

Stability of Ultimate Motion in an Attitude Control System with Unbalanced Thrusters

Theme A SINGLE axis attitude control system, employing -/man integral pulse frequency modulator and thrusters having unsymmetrical force characteristics, is analyzed for the stability of its ultimate motion around a small equilibrium region, and for convergence of the system trajectory from large initial states to this region. A type of motion, which for practical purposes is equivalent to a two-pulse limit cycle, is defined and referred to here as Relationships among the several system parameters are established and these ensure the existence of favorable motion. To establish the convergence from large initial states, a function similar to a Lyapunov function, but involving the concept of the minimum distance between a point and a set, is used as an analytical tool. The analytical results are displayed conveniently on a single graph and are verified by experiments on a computer simulation.

A note on problems with periodic target sets

For certain types of optimization problems, the target set may consist of an infinite number of points uniformly spaced along one or more of the state variable axes. This is true, for example, in the case of time optimal single-axis attitude control. Since the target set is noncompact, the maximum principle cannot be applied directly. However, a new set of state variables can be defined ahich eliminates this problem. The single-axis attitude control problem will be solved to demonstrate the method.

The Optimal Control of Some Attitude Control Systems for Different Performance Criteria

Optimal control functions in the sense of minimum settling time and minimum fuel or energy consumption are derived for several different single-axis attitude control systems. The systems treated differ only in the mechanism used to produce control torque. The torque producing elements considered include, (i) reaction gas jets, with either one or two discrete levels of thrust, (ii) an armature controlled d-c motor, (iii) a two-phase a-c motor. Optimal switching curves for these systems are illustrated in the phase plane, and the optimal choice of system parameter values is discussed.