Nonlinear attitude control of a spacecraft with distributed actuation of solar arrays

This paper presents a novel control architecture and algorithm for precision attitude control of a one-degree-of-freedom dynamic model of a spacecraft. To achieve a parametric model-based control design approach for this new spacecraft actuation and control architecture, the nonlinear dynamics of the open-loop plant are modeled as an ordinary differential equation (ODE)-partial differential equation (PDE) system. The ODE describes the spacecraft single-axis rigid-body rotation, and the PDE describes the spatially continuous flexible dynamics of the solar array including an allocation for a multi-input distributed piezoelectric actuation system bonded on the solar array. This distributed actuation system is called strain-actuated solar arrays. Based on this plant model, a nonlinear ODE-PDE feedback controller for attitude trajectory tracking and slewing is presented with detailed stability proofs. From an end-to-end point of view, the controller drives the distributed piezoelectric actuator patches with voltages that induce bending deflections in the solar arrays, causing controlled reaction torques on the bus to yield target-following motions and precision spacecraft attitude control. The proposed algorithm can be extended to any distributed actuation system with appropriate control input to actuator input mapping. The benefits and limitations of the proposed attitude control method using strain actuation are discussed later in terms of solar array inertia and structural rigidity. This paper also reports experimental results that demonstrate command-following rotations of a cylindrical bus via closed-loop control of its flexible appendages.