# A Modified Preassigned Finite-Time Control Scheme for Spacecraft Large-Angle Attitude Maneuvering and Tracking

## TL;DR

This paper introduces a new control scheme for spacecraft to perform large-angle maneuvers while respecting physical and operational constraints.

## Contribution

The novel contribution is a modified preassigned finite-time control scheme that adapts to angular velocity and torque constraints.

## Key findings

- A sliding-mode-like vector ensures angular velocity constraints are satisfied.
- The proposed controller stabilizes the system and compensates for actuator saturation.
- Simulation results confirm the controller's effectiveness in practical scenarios.

## Abstract

This paper addresses the problem of large-angle attitude maneuvering and tracking control for rigid spacecraft, considering angular velocity and torque constraints, actuator faults, and external disturbances. First, a sliding-mode-like vector is constructed to guarantee the satisfaction of the angular velocity constraints. A modified preassigned finite-time function, which can adaptively adjust the boundaries, is then proposed to constrain the sliding-mode-like vector. The controller is designed to stabilize the closed-loop system using a barrier Lyapunov function. Additionally, actuator saturation is compensated adaptively, and the system’s lumped disturbance is estimated using a fixed-time disturbance observer. Finally, the practically preassigned finite-time stability of the closed-loop system is demonstrated. In practical applications, the proposed controller can guarantee transient and steady-state performance, prevent excessive angular velocity, and ensure compliance with the physical limitations of the actuators. Simulation results are provided to demonstrate the effectiveness of the proposed controller.