A review on optimization of composite structures Part I: Laminated composites

The rapid developments of artificial intelligence in the last decade are influencing aerospace engineering to a great extent and research in this context is proliferating. We share our observations on the recent developments in the area of spacecraft guidance dynamics and control, giving selected examples on success stories that have been motivated by mission designs. Our focus is on evolutionary optimisation, tree searches and machine learning, including deep learning and reinforcement learning as the key technologies and drivers for current and future research in the field. From a high-level perspective, we survey various scenarios for which these approaches have been successfully applied or are under strong scientific investigation. Whenever possible, we highlight the relations and synergies that can be obtained by combining different techniques and projects towards future domains for which newly emerging artificial intelligence techniques are expected to become game changers.

A Survey on Artificial Intelligence Trends in Spacecraft Guidance Dynamics and Control

The rapid developments of Artificial Intelligence in the last decade are influencing Aerospace Engineering to a great extent and research in this context is proliferating. We share our observations on the recent developments in the area of Spacecraft Guidance Dynamics and Control, giving selected examples on success stories that have been motivated by mission designs. Our focus is on evolutionary optimisation, tree searches and machine learning, including deep learning and reinforcement learning as the key technologies and drivers for current and future research in the field. From a high-level perspective, we survey various scenarios for which these approaches have been successfully applied or are under strong scientific investigation. Whenever possible, we highlight the relations and synergies that can be obtained by combining different techniques and projects towards future domains for which newly emerging artificial intelligence techniques are expected to become game changers.

Simulation of the dynamics of an electrodynamic tether on a circular inclined orbit shows a very complex motion driven by the electrodynamic forces acting on the conductive tether. These forces depend on the current flowing in the wire, the Earth magnetic field, the orbital velocity and the tether position. In this paper we use a simple model to describe the dynamic effects of these forces. The tether is modeled as a rigid rod with point masses at the ends. We also adopt a non-tilted dipole model for the Earth magnetic field, and we assume that the tether current is constant. When the current is null, the system has a stable equilibrium position with the tether aligned along the local vertical. When the current is different from zero, a periodic motion appears. A nonlinear analysis of the motion shows that the periodic solutions are always unstable (within the limitation of the model considered in the paper). The physical reason for the instability is that the electrodynamic forces pump energy continually into the system. The net energy increase per orbit for the periodic solution (or state space trajectory) is zero. However, any nonperiodic trajectory in its neighborhood has a positive net energy flux per orbit so that after several orbits the in-plane libration becomes a rotation. The mechanism responsible for this instability depends on the orbital inclination. Unlike other destabilizing mechanisms found in electrodynamic tethers, this one is present in any kind of tether system with either a flexible or a rigid tether, operating in the generator or thruster mode and utilizing a bare tether or a large spherical termination to collect the ionospheric electrons. The instability described in this paper is independent of the presence of resonant force components that may be generated by the magnetic and plasma fields.

A new kind of dynamic instability in electrodynamic tethers

Considering the number of applications, and the quantity of research conducted over the past few decades, it wouldn't be an overstatement to label the piezoelectric materials as the cream of the crop of the smart materials. Among the various smart materials, the piezoelectric materials have emerged as the most researched material for practical applications. They owe it to a few key factors like low cost, large frequency bandwidth of operation, availability in many forms, and the simplicity offered in handling and implementation. For piezoelectric materials, from an application standpoint, the area of active control of vibration, noise, and flow, stands, alongside energy harvesting, as the most researched field. Over the past three decades, several authors have used piezoelectric materials as sensors and actuators, to (i) actively control structural vibrations, noise and aeroelastic flutter, (ii) actively reduce buffeting, and (iii) regulate the separation of flows. These studies are spread over several engineering disciplines-starting from large space structures, to civil structures, to helicopters and airplanes, to computer hard disk drives. This review is an attempt to concise the progress made in all these fields by exclusively highlighting the application of the piezoelectric material. The research carried out in the past five years, in the areas of modeling, and optimal positioning of piezoelectric actuators/sensors, for active vibration control, are covered. Along with this, investigations into different control algorithms, for the piezoelectric based active vibration control, are also reviewed. Studies reporting the use of piezoelectric modal filtering and self sensing actuators, for active vibration control, are also surveyed. Additionally, research on semi-active vibration control techniques like the synchronized switched damping (on elements like resistor, inductor, voltage source, negative capacitor) has also been covered

https://iopscience.iop.org/article/10.1088/1361-665X/ab7541/pdf

Review on the use of piezoelectric materials for active vibration, noise, and flow control

A stacking sequence optimization method, which is conducted on the basis of a ground laminate and utilizes a two-level approximation as well as a genetic algorithm (GA), was developed before by the authors. Compared with general GAs, this method shows lower computational costs while reaching a high level of practical feasibility. However, the published work did not involve problems constrained with a strength requirement, which is essential for laminate structures subject to multiple loading conditions. Thus, in the present study, this approach is extended to implement strength constraints for laminate stacking sequence optimizations. First, to avoid the selection of some control parameters in the GA as well as to improve its performance, the standard genetic algorithm is modified with adaptive schemes in the fitness function and GA operators. Furthermore, by adopting the first-ply failure criterion and considering the stresses/strains for each layer in the ground laminate, the concept of temporal deletion techniques is proposed to extend this approach for handling optimization problems with strength constraints. Moreover, by combining the optimizer with the general finite element software MSC. Patran/Nastran, an optimization framework is established to conduct the optimization easily. Numerical examples are performed in repeated runs to illustrate the performance of the modified approaches in the GA as well as the feasibility and efficiency of this optimization system.

Laminate stacking sequence optimization with strength constraints using two-level approximations and adaptive genetic algorithm

Vibration isolation and dual-stage actuation pointing system for space precision payloads

Multi-objective optimal design of hybrid composite laminates for minimum cost and maximum fundamental frequency and frequency gaps

The tethered satellite with chemical propulsion has broad application prospects in the disposal of abandoned satellites, the orbital rescue of spacecrafts, and the transportation of space supplies, which is completely different from the traditional applications of tethered satellites. Therefore, new research on its dynamics, stability, and control becomes useful and interesting. In this article, based on a dumbbell model of tethered satellite, the dynamics equations of tethered system in orbital maneuvering are established. Furthermore, according to the definitions of transversal and radial propulsive coefficients, analytical solutions of the equilibrium position for librational angle are derived during maneuvering in orbital plane; meanwhile, the effects of propulsive coefficients on librational stability are analyzed, which provides a basis for a selection of expected attitude trajectory. Then, a method of hierarchical sliding-mode tension control is presented to track the expected in-plane angle. This method can address the underactuated problem of tethered systems without either complex coordinate transformation for the system state model or constraint equation restrictions. During orbital flight, in-plane and out-of-plane angles are decoupled, so the tether tension control cannot be conducted to inhibit the out-of-plane angle. To solve this problem, the binormal component of thrust acceleration normal to the orbital plane is adopted as a control variable, and a feedback linearization-based thrust controller is designed to damp out the out-of-plane angle. Afterwards, orbital transfer cases between two circular orbits are studied to demonstrate the effectiveness of the tethered satellite with chemical propulsion. Numerical simulation results indicate that the stability of librational angles has a close relation to propulsive coefficients, and distributions of stable centers and unstable saddle points are totally different on both sides of bifurcation point. In addition, tracking control requirements for tethered satellite are guaranteed by designed controllers, which ensure flight safety in orbital maneuvering.

Stability and control of tethered satellite with chemical propulsion in orbital plane

Tether drag deorbit technology with chemical propulsion is an effective method of active removal of space debris, which is completely different from the traditional applications of tethered satellites. During flight in a non-Keplerian orbit, the tethered satellite is impacted by a compelling active thrust and presents complicated librational characteristics. In this article, based on a dumbbell model of tethered satellite, analytical first-order solutions of the librational angles of a tethered satellite are derived under a small, continuous, constant thrust in the transversal, tangential, radial and binormal directions. The librational characteristics of a tethered satellite are revealed for two conditions: (1) in-plane orbit transfer of an abandoned satellite and (2) adjustment of the orbital inclination of a satellite. Furthermore, the ranges of designed system parameters, such as initial geocentric distance, mass of the system, mass ratio between base satellite and objective satellite, tether length, ...

Hai Huang

Papers

Laminate stacking sequence optimization with strength constraints using two-level approximations and adaptive genetic algorithm

Vibration isolation and dual-stage actuation pointing system for space precision payloads

Multi-objective optimal design of hybrid composite laminates for minimum cost and maximum fundamental frequency and frequency gaps

Stability and control of tethered satellite with chemical propulsion in orbital plane

Librational characteristics of a dumbbell modeled tethered satellite under small, continuous, constant thrust