Attitude Kinematic Equations Research Articles

Approaching and pointing tracking control for tumbling target under motion constraints

On-orbit servicing for the failed spacecraft involves two necessary stages: on-orbit observing and approaching. For these two stages, a novel approaching and pointing tracking control scheme under motion constraints and input saturation is proposed in this paper. For the security of approaching, a relative position guidance law for specific surface hovering is proposed. Then, a model predictive controller based on quadratic programming algorithm is designed. For the continuous observation task, the optimal maneuver angular velocity under the motion constraint is planned through model predictive control. In order to reduce the dimensionality of the optimization problem to reduce the computational effort, only the attitude kinematics equation is used as the process model. Thereafter, the adaptive anti-saturation attitude controller is designed to track the optimal maneuver angular velocity. The anti-saturation auxiliary system and the adaptive update law are used to cope with the control torque saturation and the integrated uncertainties, respectively. Finally, the stability of the closed-loop system is demonstrated by Lyapunov method. Simulation results demonstrate that the proposed control scheme accomplishes the approaching and pointing tracking task, and finally service spacecraft maintains hovering above the tumbling target and observing its specific surface.

Adaptive fault-tolerant attitude control for a CMG-based underwater vehicle

This paper proposes a fault-tolerant control strategy for the attitude control problem of a CMG-based underwater vehicle based on the adaptive sliding mode control method and Lyapunov stability theory. First, a fault-tolerant control model is presented for the quaternion-based attitude kinematic equations combined with a pyramid control moment gyroscope (CMG) system. Second, considering the momentum singularity and input saturation constraint problem, adaptive control method is inspired to estimate the model uncertainties and actuator failures under some basic assumptions. Subsequently, the proposed controller is derived from backstepping-based design techniques and its feasibility is complemented by the remarks. Finally, its efficiency and robustness are illustrated in simulation results to against the uncertainties and disturbances.

Rotations, Transformations, Left Quaternions, Right Quaternions?

This paper surveys the two fundamental possible choices in representing the attitude of an aerospace vehicle: active and passive rotations. The consequences of the choice between the two are detailed for the two most common attitude parameterizations, a three-by-three orthogonal matrix and the quaternion. Successive rotations are also reviewed in this context as well as the attitude kinematic equations.

HIGH-PRECISION ATTITUDE ESTIMATION METHOD OF STAR SENSORS AND GYRO BASED ON COMPLEMENTARY FILTER AND UNSCENTED KALMAN FILTER

Abstract. Determining the attitude of satellite at the time of imaging then establishing the mathematical relationship between image points and ground points is essential in high-resolution remote sensing image mapping. Star tracker is insensitive to the high frequency attitude variation due to the measure noise and satellite jitter, but the low frequency attitude motion can be determined with high accuracy. Gyro, as a short-term reference to the satellite’s attitude, is sensitive to high frequency attitude change, but due to the existence of gyro drift and integral error, the attitude determination error increases with time. Based on the opposite noise frequency characteristics of two kinds of attitude sensors, this paper proposes an on-orbit attitude estimation method of star sensors and gyro based on Complementary Filter (CF) and Unscented Kalman Filter (UKF). In this study, the principle and implementation of the proposed method are described. First, gyro attitude quaternions are acquired based on the attitude kinematics equation. An attitude information fusion method is then introduced, which applies high-pass filtering and low-pass filtering to the gyro and star tracker, respectively. Second, the attitude fusion data based on CF are introduced as the observed values of UKF system in the process of measurement updating. The accuracy and effectiveness of the method are validated based on the simulated sensors attitude data. The obtained results indicate that the proposed method can suppress the gyro drift and measure noise of attitude sensors, improving the accuracy of the attitude determination significantly, comparing with the simulated on-orbit attitude and the attitude estimation results of the UKF defined by the same simulation parameters.

Initial Attitude Determination of Aerial Platform Based on MIMU

Aiming at the problem of initial attitude determination of aerial platform, a low computational attitude fusion algorithm is proposed based on MIMU. Attitude kinematic equations described by quaternions are developed and the filter structure used in this paper is designed. Real fly test results show that: at different initial deviation, the alignment precision of roll and pitch angles are within 1 °, attitude errors converge to 5 °or less within 12s, which meets the requirements of the aerial platform attitude fast self-determination. The filter algorithm has a small amount of calculation and is easy to be realized.

Direct Lyapunov-based control law design for spacecraft attitude maneuvers

Abstract A direct Lyapunov–based control law is presented to perform on–orbit stability for spacecraft attitude maneuvers. Spacecraft attitude kinematic equations are coupled, nonlinear, multi–input multi–output (MIMO), which baffles controller design. Orbit angular rates are taken into account in kinematic equations and influence of gravity gradient moments and disturbance moments on the spacecraft attitude in dynamic equations is considered to approach the practical environment, which enhance the problem complexity to some extent. Based on attitude tracking errors and angular rates' a Lyapunov function is constructed' through which the stabilizing feedback control law is deduced via Lie derivation of the Lyapunov function. The proposed method can deal with the case that the spacecraft is subjected to mass property variations or centroidal inertia matrix variations due to fuel assumption or flexibility, and disturbance moments, which shows the proposed controller is robust for spacecraft attitude maneuve...

Predictive Centroiding for Star Trackers with the Effect of Image Smear

Star centroiding, locating the star center in a star image frame, is a fundamental process for any star tracker. In this paper, the approximate locations of the stars in successive image frames are predicted using the angular velocity as provided by a rate gyro, then the centroid is updated based upon local image processing. When the rate gyro data are not available, then the angular velocity is estimated using the attitude kinematics equation and successive attitude estimates from the Lost-In-Space Algorithm. Also considered are the special features of noncircular star image shapes associated with optical tagging of starlight and/or image smear. Finally, an approach is presented to implement these ideas with the recently introduced Active Pixel Sensors, allowing dynamic pixel access and selected subarray analog-to-digital conversion of the pixel information is feasible, with logic dictated by most recent image and the instantaneous angular velocity estimate. This novel process that predicts the star image starlight locations is termed predictive centroiding. The problem of the image smear is also treated, in which the relatively high angular velocity of the spacecraft will affect the shape of the star images. These approaches, coupled with active pixel sensors, should enable near-optimal image processing and high frame rates. The paper includes analytical, computational, and night sky experimental results.

Precision Spacecraft Attitude Estimators Using an Optical Payload Pointing System

The advancement of satellite program technology mandates that issues affecting future spacecraft system development cost be resolved, while continuing to meet smaller size, lower power, and more stringent mission requirements. In the specie c area of the spacecraft attitude determination system, an optical payload pointing system can servea dual purpose: to support the payload mission and to providepreciseattitude information for the spacecraft functions. As a result, star trackers orotherprecisereferencesystems can beeliminated to reduce the development cost. Additional benee ts include performance robustness to spacecraft motion or disturbance and potential cost saving due to weight reduction, e.g., launch cost. Attitude estimators using an optical payload pointing system and strap-down gyros are derived in detail for two distinct formulations: spacecraft body and inertial formulations. Alternative Kalman e lter equation derivations are shown using the skew symmetric matrix properties of the attitude kinematics equation. It is also shown that both formulations produce identical solutions. However, the body formulation is conceptually easier to understand, and the inertial formulation requires less processing time. To show thespacecraft attitudeestimatorperformanceusing an optical payload pointing system, an exampleisshown for an agile low-Earth-orbit satellite.