Samir Bennani

Valentin Preda, Andrew Hyslop, Samir Bennani

This paper introduces an algorithm to perform optimal reorientation of a spacecraft during a high speed flyby mission that maximizes the time a certain target is kept within the field of view of scientific instruments. The method directly handles the nonlinear dynamics of the spacecraft, sun exclusion constraint, torque and momentum limits on the reaction wheels as well as potential faults in these actuators. A sequential convex programming approach was used to reformulate non-convex pointing objectives and other constraints in terms of a series of novel convex cardinality minimization problems. These subproblems were then efficiently solved even on limited hardware resources using convex programming solvers implementing second-order conic constraints. The proposed method was applied to a scenario that involved maximizing the science time for the upcoming Comet Interceptor flyby mission developed by the European Space Agency. Extensive simulation results demonstrate the capability of the approach to generate viable trajectories even in the presence of reaction wheel failures or prior dust particle impacts.

Hans Strauch, Klaus Luig, Samir Bennani

The cost associated with developing flight control forms a significant part of the overall development cost. The increased demand for greater functionality and for extending the domain of applicability of future launchers leads to higher complexity of the GNC algorithms. Furthermore, there is also a need for a responsive design methodology, which can quickly adapt to changes in the requirements during the development process. These demands are stretching the current,largely manual, development process, which is fragmented in the different disciplines and activities concerning modelling, algorithm design, software coding, implementation on the avionics platform and the associated testing at the different stages. The model-based-design (MBD) philosophy presents an attractive solution in addressing the multi-disciplinary nature of the flight algorithm design task. In terms of design process, this materializes in a tight coupling between the modelling, the design and the analysis activities.An integrated design framework for the GNC development for future launcher upper stages has been realized.

Christina Jetzschmann, Hans Strauch, Samir Bennani

This paper presents a model based experimental investigation to demonstrate the usefulness of an active damping strategy to manage fluid sloshing motion in spacecraft tanks. The active damping strategy is designed to reduce the degrading impact on maneuvering and pointing performance via a force feedback strategy. Many problems have been encountered until now, such as instability of the closed loop system, excessive consumption in the attitude propellant or problems for engine re-ignition in upper stages. Mostly, they have been addressed in a passive way via the design of baffles and membranes, which on their own have mass and constructive impacts. Active management of propellant motion in launchers and satellites has the potential to increase performance on various levels. This paper demonstrates active slosh management using force feedback for the compensation of the slosh resonances. Force sensors between tank and the carrying structure provide information of the fluid motion via the reaction force. The control system is designed to generate an appropriate acceleration profile that leads to desired attenuation profiles in amplitude, frequency and time. Two robust control design methods, one based on $μ$ design and the other on parametric structured design based on non-smooth optimization of the worst-case $H_{\infty}$ norm, are applied. The controller is first tested with a computational fluid dynamics simulation in the loop. Finally a water tank mounted on a Hexapod with up to $1100$ liter is used to evaluate the control performance. The paper illustrates that is possible to actively influence sloshing via closed loop.

Tarik Mountassir Bouchaib Nassereddine, Abdelkrim Haqiq, Samir Bennani

Wireless mesh networks have seen a real progress due of their implementation at a low cost. They present one of Next Generation Networks technologies and can serve as home, companies and universities networks. In this paper, we propose and discuss a new multi-objective model for nodes deployment optimization in Multi-Radio Multi-Channel Wireless Mesh Networks. We exploit the trade-off between network cost and the overall network performance. This optimization problem is solved simultaneously by using a meta-heuristic method that returns a non-dominated set of near optimal solutions. A comparative study was driven to evaluate the efficiency of the proposed model.