The commented paper discusses the attitude dynamics representation using quaternions. The main idea of the paper is to eliminate angular velocity from the dynamics equations. The obtained equations are interesting. However, all applications presented in the discussed paper have plain errors in the equations derivations. This affects the main results and conclusions of the paper, which require significant corrections. • Errors in commented paper are outlined. • Quaternion dynamics equations application for the attitude control is discussed. • Control singularity is shown. [ABSTRACT FROM AUTHOR]
This paper addresses the attitude reorientation problem under the pointing-constraint zone, angular velocity limits, and actuator constraints. The ERG-based control scheme is designed such that the attitude is stabilized, while the state and control constraints stay in the allowable regions defined by the Lyapunov invariant subset. The disturbance observer-based control law is developed in the inner loop of ERG that enables attitude stabilization in the presence of external disturbance. The navigation layer is utilized to manipulate the reference state to enforcing constraints satisfaction. The effectiveness of the proposed constrained attitude control algorithm is then verified through numerical simulations. • Address the constrained attitude control problem via explicit reference governor. • Design a disturbance observer-based inner loop controller. • Design the Lyapunov thresholds of state and actuator constraints. [ABSTRACT FROM AUTHOR]
Spacecraft attitude control solutions typically are torque-level algorithms that simultaneously control both the attitude and angular velocity tracking errors. In contrast, robotic control solutions are kinematic steering commands where rates are treated as the control variable, and a servo-tracking control subsystem is present to achieve the desired control rates. In this paper kinematic attitude steering controls are developed where an outer control loop establishes a desired angular response history to a tracking error, and an inner control loop tracks the commanded body angular rates. The overall stability relies on the separation principle of the inner and outer control loops which must have sufficiently different response time scales. The benefit is that the outer steering law response can be readily shaped to a desired behavior, such as limiting the approach angular velocity when a large tracking error is corrected. A Modified Rodrigues Parameters implementation is presented that smoothly saturates the speed response. A robust nonlinear body rate servo loop is developed which includes integral feedback. This approach provides a convenient modular framework that makes it simple to interchange outer and inner control loops to readily setup new control implementations. Numerical simulations illustrate the expected performance for an aggressive reorientation maneuver subject to an unknown external torque. [ABSTRACT FROM AUTHOR]