Engineering evaluations and studies. Volume 3: Exhibit C

High rate multiplexes asymmetry and jitter, data-dependent amplitude variations, and transition density are discussed

Minimisation of the wire position uncertainties of the new CERN vacuum wire scanner

The particle production of an accelerator is characterised by the accelerated species of particles, by their number and energy. The particle rate is determined by the production cross section, a natural constant and the accelerator dependent parameter luminosity. The luminosity is proportional to the number of particles in each beam and inversely proportional to the particle beam transverse dimensions. The luminosity increases with the particle beam density and therefore the probability of interactions too. To optimize the transverse beam sizes, profile monitors are used to measure parameter depending changes. Different monitors can provide beam transversal profile measurements (Wire Scanners, Synchrotron Light Monitors, Rest Gas Profile Monitors), however the wire scanner monitor is considered to be the most accurate of all monitors. Wire scanner instruments measure the transverse beam density profile in a particle accelerator by means of moving a thin wire in an intermittent manner. In the next years the luminosity of the Large Hadron Collider (LHC) will be significantly increased and more accurate beam profile measurement will necessary. The new performance demands a wire travelling speed up to 20 m.s-1 and a position measurement accuracy of the order of few micros. The existing wire scanners does not reach the new requirements as their accuracy achieved is limited by the motorization, the angular position measurement system located outside of the vacuum vessels and the vibration of the thin carbon wire which has been identified as one of the major error sources reducing the knowledge of the wire position. Therefore the development of a new device whose accuracy meets the new requirements was mandatory. This thesis work aims to provide suitable inputs for the design and operation of this new fast wire scanner in order to minimize the uncertainties in the wire position. To accomplish the aims the understanding of the wire vibrations in such a system is one of the main goals of this work. More specifically, the development of a suitable vibration measurement system and the construction of dynamic models of the system are the two goals aimed. For the new scanner design this work intend to propose, the conceptual design, the optimization of the most critical parts and the operation procedure that will allow the new device to reach the required performances imposed by the forthcoming LHC conditions.La producción de partículas de un acelerador se caracteriza por las especies de partículas aceleradas, por su número y energía. La tasa de partículas se determina a partir de la sección transversal de producción, una constante natural, y de un parámetro que depende del acelerador, la luminosidad. La luminosidad es proporcional al número de partículas por haz e inversamente proporcional a la dimensión transversal de los haces. La luminosidad aumenta con la densidad de partículas y por lo tanto también aumenta la probabilidad de interacciones entre los haces. Para optimizar la sección trasversal del haz, se utilizan monitores de perfil de haz. Diversos tipos de monitores pueden proporcionar mediciones del perfil transversal del haz (Escáneres de hilo, Monitores de luz de sincrotrón, Monitores de análisis de gas residual), sin embargo el escáner de hilo está considerado como el más preciso de todos ellos. Los escáneres de hilo miden el perfil del haz atravesándolo con un hilo muy delgado de manera intermitente. En los próximos años la luminosidad del Gran Colisionador de Hadrones (LHC) se incrementará de manera significativa, por lo que serán necesarios sistemas de medida de perfil de haz más precisos que lo actuales. Las nuevas características, requerirán velocidad de desplazamiento del hilo de hasta 20 ms-1 y una precisión en la medida de posición del hilo de tan solo unas micras. Los escáneres actuales no pueden alcanzar estos requerimientos ya que su precisión está limitada por el sistema de motorización, por el medidor angular de posición que está situado fuera del tanque de vacío y por las vibraciones del hilo, la cuales han sido identificadas como una de las mayores fuentes de error a la hora de conocer la posición real del hilo. Por todo esto, el desarrollo de un nuevo dispositivo cuyas características cumplan los nuevos requerimientos era necesario. Este trabajo de tesis tiene como objetivo proporcionar criterios adecuados para el diseño y operación de un nuevo escáner, con el fin de minimizar las incertidumbres en la posición del hilo. Para lograr estos objetivos, el entender las vibraciones del hilo en un sistema de este tipo es un objetivo primordial. De manera más específica el desarrollo de sistemas de medida de vibración adecuados y la construcción de modelos dinámicos del sistema son los dos objetivos concretos perseguidos por este trabajo. De cara al nuevo diseño, este trabajo pretende proponer un diseño conceptual así como definir los criterios para la optimización de las partes más críticas y establecer un procedimiento de operación que permita al nuevo dispositivo alcanzar los requerimientos impuestos por las futuras condiciones del LHC.Postprint (published version

Performance-driven control of nano-motion systems

The performance of high-precision mechatronic systems is subject to ever increasing demands regarding speed and accuracy. To meet these demands, new actuator drivers, sensor signal processing and control algorithms have to be derived. The state-of-the-art scientific developments in these research directions can significantly improve the performance of high-precision systems. However, translation of the scientific developments to usable technology is often non-trivial. To improve the performance of high-precision systems and to bridge the gap between science and technology, a performance-driven control approach has been developed. First, the main performance limiting factor (PLF) is identified. Then, a model-based compensation method is developed for the identified PLF. Experimental validation shows the performance improvement and reveals the next PLF to which the same procedure is applied. The compensation method can relate to the actuator driver, the sensor system or the control algorithm. In this thesis, the focus is on nano-motion systems that are driven by piezo actuators and/or use encoder sensors. Nano-motion systems are defined as the class of systems that require velocities ranging from nanometers per second to millimeters per second with a (sub)nanometer resolution. The main PLFs of such systems are the actuator driver, hysteresis, stick-slip effects, repetitive disturbances, coupling between degrees-of-freedom (DOFs), geometric nonlinearities and quantization errors. The developed approach is applied to three illustrative experimental cases that exhibit the above mentioned PLFs. The cases include a nano-motion stage driven by a walking piezo actuator, a metrological AFM and an encoder system. The contributions of this thesis relate to modeling, actuation driver development, control synthesis and encoder sensor signal processing. In particular, dynamic models are derived of the bimorph piezo legs of the walking piezo actuator and of the nano-motion stage with the walking piezo actuator containing the switching actuation principle, stick-slip effects and contact dynamics. Subsequently, a model-based optimization is performed to obtain optimal drive waveforms for a constant stage velocity. Both the walking piezo actuator and the AFM case exhibit repetitive disturbances with a non-constant period-time, for which dedicated repetitive control methods are developed. Furthermore, control algorithms have been developed to cope with the present coupling between and hysteresis in the different axes of the AFM. Finally, sensor signal processing algorithms have been developed to cope with the quantization effects and encoder imperfections in optical incremental encoders. The application of the performance-driven control approach to the different cases shows that the different identified PLFs can be successfully modeled and compensated for. The experiments show that the performance-driven control approach can largely improve the performance of nano-motion systems with piezo actuators and/or encoder sensors

Micro/Nano Manufacturing

Micro manufacturing involves dealing with the fabrication of structures in the size range of 0.1 to 1000 µm. The scope of nano manufacturing extends the size range of manufactured features to even smaller length scales—below 100 nm. A strict borderline between micro and nano manufacturing can hardly be drawn, such that both domains are treated as complementary and mutually beneficial within a closely interconnected scientific community. Both micro and nano manufacturing can be considered as important enablers for high-end products. This Special Issue of Applied Sciences is dedicated to recent advances in research and development within the field of micro and nano manufacturing. The included papers report recent findings and advances in manufacturing technologies for producing products with micro and nano scale features and structures as well as applications underpinned by the advances in these technologies

Robust fault tolerant control of induction motor system

Research into fault tolerant control (FTC, a set of techniques that are developed to increase plant availability and reduce the risk of safety hazards) for induction motors is motivated by practical concerns including the need for enhanced reliability, improved maintenance operations and reduced cost. Its aim is to prevent that simple faults develop into serious failure. Although, the subject of induction motor control is well known, the main topics in the literature are concerned with scalar and vector control and structural stability. However, induction machines experience various fault scenarios and to meet the above requirements FTC strategies based on existing or more advanced control methods become desirable. Some earlier studies on FTC have addressed particular problems of 3-phase sensor current/voltage FTC, torque FTC, etc. However, the development of these methods lacks a more general understanding of the overall problem of FTC for an induction motor based on a true fault classification of possible fault types.In order to develop a more general approach to FTC for induction motors, i.e. not just designing specific control approaches for individual induction motor fault scenarios, this thesis has carried out a systematic research on induction motor systems considering the various faults that can typically be present, having either “additive” fault or “multiplicative” effects on the system dynamics, according to whether the faults are sensor or actuator (additive fault) types or component or motor faults (multiplicative fault) types.To achieve the required objectives, an active approach to FTC is used, making use of fault estimation (FE, an approach that determine the magnitude of a fault signal online) and fault compensation. This approach of FTC/FE considers an integration of the electrical and mechanical dynamics, initially using adaptive and/or sliding mode observers, Linear Parameter Varying (LPV, in which nonlinear systems are locally decomposed into several linear systems scheduled by varying parameters) and then using back-stepping control combined with observer/estimation methods for handling certain forms of nonlinearity.In conclusion, the thesis proposed an integrated research of induction motor FTC/FE with the consideration of different types of faults and different types of uncertainties, and validated the approaches through simulations and experiments

The 31st Aerospace Mechanisms Symposium

The proceedings of the 31st Aerospace Mechanisms Symposium are reported. Topics covered include: robotics, deployment mechanisms, bearings, actuators, scanners, boom and antenna release, and test equipment. A major focus is the reporting of problems and solutions associated with the development and flight certification of new mechanisms