The Multiple Use Plug Hybrid for Nanosats (MUPHyN) prototype thruster incorporates solutions to several major challenges that have traditionally limited the deployment of chemical propulsion systems on small spacecraft. The MUPHyN thruster offers several features that are uniquely suited for small satellite applications. These features include 1) a non-explosive ignition system, 2) non-mechanical thrust vectoring using secondary fluid injection on an aerospike nozzle cooled with the oxidizer flow, 3) a non-toxic, chemically-stable combination of liquid and inert solid propellants, 4) a compact form factor enabled by the direct digital manufacture of the inert solid fuel grain. Hybrid rocket motors provide significant safety and reliability advantages over both solid composite and liquid propulsion systems; however, hybrid motors have found only limited use on operational vehicles due to 1) difficulty in modeling the fuel flow rate 2) poor volumetric efficiency and/or form factor 3) significantly lower fuel flow rates than solid rocket motors 4) difficulty in obtaining high combustion efficiencies. The features of the MUPHyN thruster are designed to offset and/or overcome these shortcomings. The MUPHyN motor design represents a convergence of technologies, including hybrid rocket regression rate modeling, aerospike secondary injection thrust vectoring, multiphase injector modeling, non-pyrotechnic ignition, and nitrous oxide regenerative cooling that address the traditional challenges that limit the use of hybrid rocket motors and aerospike nozzles. This synthesis of technologies is unique to the MUPHyN thruster design and no comparable work has been published in the open literature.

This dissertation focuses on the constrained control of multi-body systems which are actuated by vectorized thrusters. A general control framework is proposed to stabilize the task configuration while ensuring constraints satisfaction at all times. For this purpose, the equations of motion of the system are derived using the Euler-Lagrange method. It is seen that under some reasonable conditions, the system dynamics are decoupled. This property is exploited in a cascade control scheme to stabilize the points of equilibrium of the system. The control scheme is composed of an inner loop, tasked to control the attitude of the vectorized thrusters, and an outer loop which is tasked to stabilize the task configuration of the system to a desired configuration. To prove stability, input-to-state stability and small gain arguments are used. All stability properties are derived in the absence of constraints, and are shown to be local. The main result of this analysis is that the proposed control scheme can be directly applied under the assumption that a suitable mapping between the generalized force and the real inputs of the system is designed. This thesis proposes to enforce constraints by augmenting the control scheme with two types of Reference Governor units: the Scalar Reference Governor, and the Explicit Reference Governor. This dissertation presents two case studies which inspired the main generalization of this thesis: (i) the control of an unmanned aerial and ground vehicle manipulating an object, and (ii) the control of a tethered quadrotor. Two further case studies are discussed afterwards to show that the generalized control framework can be directly applied when a suitable mapping is designed. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

A parametric study on Secondary Injection Thrust Vector Control (SITVC) has been accomplished numerically with the help of a commercial Computational Fluid Dynamics (CFD) code called FLUENT&reg / . This study consists of two parts / the first part includes the simulation of three dimensional flowfield inside a test case nozzle for the selection of parameters associated with both computational grid and the CFD solver such as mesh size, turbulence model accompanied with two different wall treatment approaches, and solver type. This part revealed that simulation of internal flowfield by a segregated solver with Realizable k-&amp / #949 / (Rke) turbulence model accompanied by enhanced wall treatment approach is accurate enough to resolve this kind of complex three dimensional fluid flow problems. In the second part a typical rocket nozzle with conical diverging section is picked for the parametric study on injection mass flow rate, injection location and injection angle. A test matrix is constructed / several numerical simulations are run to yield the assessment of performance of SITVC system. The results stated that for a nozzle with a small divergence angle, downstream injections with distances of 2.5-3.5 throat diameters from the nozzle throat lead to higher efficiencies over a certain range of total pressure ratios, i.e., mass flow rate ratios, upstream injections should be aligned more to the nozzle axis, i.e., higher injection angles, to prevent reflection of shock waves from the opposite wall and thus low efficiencies. Injection locations that are too much downstream may result reversed flows on nozzle exit.

Hall-effect thrusters (HETs) are among the most commonly used propulsion systems for attitude and orbit control of satellites. As an arrangement in a cluster or individually, equipped with a mechanical suspension, thrust in all three spatial directions can be generated, but requires additional mechanisms and components. Therefore, the Technische Universität Dresden (TU Dresden) is currently working on a concept for developing a Hall-effect thruster with integrated thrust vector control, which would allow steering in all three spatial directions with just a single thruster. This new concept is intended to work solely by influencing the ion beam and should not have any additional mechanical components. The HET will come with a segmented anode to set different electrical potentials at the anode and cause an inhomogeneous distribution of the electric field within the discharge channel, which results in an inhomogeneous force vector distribution at the exit plane. It is assumed that this will generate turning moments around the center of gravity. Deliberately causing those turning moments can therefore be used for steering with just one thruster. This work presents the concept of the propulsion system, gives an outlook on the advantages of its technology and shows capabilities for space applications.

La commande des actionneurs électropneumatiques a été un sujet largement traité au cours des dernières décennies. Le caractère fortement non-linéaire de son comportement en a fait un cas d'étude particulièrement pertinent dans le cadre d'une démarche d'application de la théorie de la commande des systèmes non-linéaires. L'utilisation de ces techniques a été comparée aux approches linéaires traditionnelles et généralement jugée largement supérieure notamment en termes de précision ou de temps de réponse. Dans ce manuscrit nous abordons très spécifiquement l'aspect multivariable du système et introduisons la transformée A-T, similaire à la transformée de Park appliquée classiquement aux systèmes électriques, afin de donner une forme strict feedback à son modèle d'état, de clarifier les phénomènes physiques mis en jeu lors de sa commande et de distinguer les deux degrés de liberté du système. Cette transformée permet en outre une comparaison directe avec les moteurs électriques décrits dans le repère de Park. Ce parallèle rend notamment possible la solution du problème délicat de l'observation de la position à vitesse nulle en transférant des méthodologies déjà validées sur des systèmes électriques. L'exploitation des deux degrés de liberté est illustrée par la synthèse de lois de commande combinant le suivi d'une trajectoire de position du piston au respect d'un second critère variable (réglage de la pressurisation moyenne, optimisation de la consommation instantanée). L'utilisation d'un actionneur électropneumatique asservi comme actionneur à compliance variable est étudiée. Une loi de commande basée sur la transformée A-T est proposée pour contrôler simultanément la position et la raideur pneumatique de l'actionneur. Une méthodologie de réglage des gains de commande est proposée pour définir l'impédance en boucle fermée du système. L'influence de la raideur pneumatique sur la raideur en boucle fermée est étudiée. L'utilisation d'une source d'énergie alternative (de l'hélium sous pression) est également pour la première fois mise en œuvre. L'influence du changement de gaz sur le dimensionnement de l'actionneur électropneumatique est étudiée et une méthodologie permettant d'utiliser les lois de commande prévues pour de l'air est proposée. L'ensemble des propositions faites dans ce manuscrit est testée et validée sur un banc d'essais à la structure inédite. Ce dernier allie deux actionneurs, l'un électropneumatique (l'actionneur étudié) et l'autre, un moteur plat électrique (l'actionneur de charge). L'utilisation de celui-ci permet la génération d'efforts perturbateurs dans une large bande passante ainsi que la modification en temps réel des paramètres mécaniques dynamiques de la charge. / Control of electropneumatic actuator is a subject which has been thoroughly dealt with in the past decades. The strongly non-linear behavior of those systems made them a particularly relevant case study for applications of the non linear control theory. The use of those techniques has been compared to the traditional linear approaches and is generally considered as more efficient in terms of precision and response time. In this work, we specifically deal with the multivariable character of this actuator and we introduce the A-T transformation, similar to the Park Transformation used for electrical systems study, in order to give a strict feedback form to its state model, clarify the physical phenomena occurring during its control and distinguish the system's two degrees of freedom. This transformation allows a comparison with electrical motors described in the Park's frame. This parallel allows to solution the complex problem of zero speed observation of the piston's position by transferring the methodologies which have been previously used on electrical systems. The utilization of the two degrees of freedom is illustrated by the synthesis of control law which combines the piston position trajectory tracking with the respect of a given criterion (which can be the pressurization level or the instantaneous gas consummation optimization). The use of an electropneumatic actuator as a variable stiffness actuator (VSA) is studied. A control law base on the A-T transform is proposed in order to simultaneously control the position and the pneumatic stiffness of the actuator. A control gains tuning strategy is proposed to allow the system closed loop impedance tuning. The influence of the pneumatic stiffness over the closed loop stiffness is studied. An alternative energy source (pressurized helium) is also used for the first time. The influence of the change of gas over the actuator sizing is studied and a methodology allowing using control laws designed for air applications is proposed. Every proposition are tested and validated using an innovative test bench with a unique structure. The latter combines two actuators. One is an electropneumatic actuator (the one studied) and the other one is a linear motor (used as the load actuator). The use of the latter allows disturbance generation in a wide bandwidth and the real-time tuning of the load dynamic characteristics. Finally, the tools developed in this PHD are used in order to validate the implementation of an electropneumatic solution to the thrust vector control problem of a nano scale space launcher. Data provided by the CNES (the French National Space Agency) are used to de ne specific requirements and the flight conditions are reproduced on the test bench to assess the solution quality.

The recent interests in the necessity of high maneuverability and vertical launching triggered namely the unconventional control design techniques that are effective at high angle of attack flight regimes. For most of missile configurations, this interest required thrust vector control together with conventional aerodynamic control. In this study, nonlinear modeling and dynamical analysis of a surface to air missile with both aerodynamic and thrust vector control is investigated. Aerodynamic force and moment modeling of the presented missile includes the challenging high angle of attack aerodynamics behavior and the so called hybrid control, which utilizes both tail fins and jet vanes as control surfaces. Thrust vector and aerodynamic control effectiveness is examined during flight envelope. Different autopilot designs are accomplished with hybrid control. Midcourse and terminal guidance algorithms are implemented and performed on target sets including maneuverable targets. A different initial turnover strategy is suggested and compared with standard skid-to-turn maneuver. Comparisons of initial roll with aerodynamic and thrust vector control are examined. Afterwards, some critical maneuvers and hybrid control ratio is studied with a real coded genetic algorithm. Rapid turnover for low altitude targets, intercept maneuver analysis with hybrid control ratio and lastly, engagement initiation maneuver optimization is fulfilled.