In order to meet industry demands for improved productivity and part quality, machine tools must be equipped with faster and more accurate feed drives. Over the past two decades, research has focused on the development of new control strategies and smooth trajectory generation techniques. These developments, along with advances in actuator and sensor technology, have greatly improved the accuracy of motion delivery in high speed machine tools. However, further advancement is limited by the vibration of the machine’s structure. The purpose of the research in this thesis is to develop new control techniques that use active vibration damping to achieve bandwidths near the structural frequencies of machine tools, in order to provide better dynamic positioning of the tool and workpiece. Two machine tool drives have been considered in this study. The first is a precision ball screw drive, for which a pole-placement technique is developed to achieve active vibration damping, as well as high bandwidth disturbance rejection and positioning. The pole-placement approach is simple and effective, with an intuitive physical interpretation, which makes the tuning process straightforward in comparison to existing controllers which actively compensate for structural vibrations. The tracking performance of the drive is improved through feedforward control using inverted plant dynamics and a novel trajectory pre-filter. The pre-filter is designed to remove tracking error artifacts correlated to the velocity, acceleration, jerk and snap (4th derivative) of the commanded trajectory. By applying the least-squares method to the results of a single tracking experiment, the pre-filter can be tuned quickly and reliably. The proposed controller has been compared to a controller used commonly in industry (P-PI position-velocity cascade control), and has achieved a 40-55 percent reduction in peak errors during tracking and machining tests. The controller design, stability analysis, and experimental results are discussed. The second drive considered is a linear motor driven X-Y stage arranged as a T-type gantry and worktable. The worktable motion is controlled independently of the gantry using a loop shaping filter. The gantry is actuated by dual direct drive linear motors and is strongly coupled to the worktable position, which determines its inertial characteristics. A 94 Hz yaw mode is handled in the gantry control law using sensor and actuator averaging, and active vibration damping. The stability and robustness of the design are considered using multivariable frequency domain techniques. For the worktable motion along the gantry, a bandwidth of 130 Hz is achieved. The gantry crossover frequency is 52 Hz, which is 3 times higher than the bandwidth that can be achieved using independent PID controllers (16 Hz). The performance of the proposed control scheme has been verified in step disturbance (i.e., rope snap) tests, as well as tracking and contouring experiments.

In order to meet industry demands for improved productivity and part quality, machine tools must be equipped with faster and more accurate feed drives. Over the past two decades, research has focused on the development of new control strategies and smooth trajectory generation techniques. These developments, along with advances in actuator and sensor technology, have greatly improved the accuracy of motion delivery in high speed machine tools. However, further advancement is limited by the vibration of the machine’s structure. The purpose of the research in this thesis is to develop new control techniques that use active vibration damping to achieve bandwidths near the structural frequencies of machine tools, in order to provide better dynamic positioning of the tool and workpiece. Two machine tool drives have been considered in this study. The first is a precision ball screw drive, for which a pole-placement technique is developed to achieve active vibration damping, as well as high bandwidth disturbance rejection and positioning. The pole-placement approach is simple and effective, with an intuitive physical interpretation, which makes the tuning process straightforward in comparison to existing controllers which actively compensate for structural vibrations. The tracking performance of the drive is improved through feedforward control using inverted plant dynamics and a novel trajectory pre-filter. The pre-filter is designed to remove tracking error artifacts correlated to the velocity, acceleration, jerk and snap (4th derivative) of the commanded trajectory. By applying the least-squares method to the results of a single tracking experiment, the pre-filter can be tuned quickly and reliably. The proposed controller has been compared to a controller used commonly in industry (P-PI position-velocity cascade control), and has achieved a 40-55 percent reduction in peak errors during tracking and machining tests. The controller design, stability analysis, and experimental results are discussed. The second drive considered is a linear motor driven X-Y stage arranged as a T-type gantry and worktable. The worktable motion is controlled independently of the gantry using a loop shaping filter. The gantry is actuated by dual direct drive linear motors and is strongly coupled to the worktable position, which determines its inertial characteristics. A 94 Hz yaw mode is handled in the gantry control law using sensor and actuator averaging, and active vibration damping. The stability and robustness of the design are considered using multivariable frequency domain techniques. For the worktable motion along the gantry, a bandwidth of 130 Hz is achieved. The gantry crossover frequency is 52 Hz, which is 3 times higher than the bandwidth that can be achieved using independent PID controllers (16 Hz). The performance of the proposed control scheme has been verified in step disturbance (i.e., rope snap) tests, as well as tracking and contouring experiments.

The aim of the thesis is to propose active damping as a potential control strategy for chatter instability in machine tools. The regenerative process theory explains chatter as a closed loop interaction between the structural dynamics and the cutting process. This is considered to be the most dominant reason behind machine tool chatter although other instability causing mechanisms exist. The stability lobe diagram provides a quantitative idea of the limits of stable machining in terms of two physical parameters: the width of contact between tool and the workpiece, called the width of cut and the speed of rotation of the spindle. It is found that the minimum value of the stability limit is proportional to the structural damping ratio for turning operations. This important finding provides the motivation of influencing the structural dynamics by active damping to enhance stability limits of a machining operation. A direct implementation of active damping in an industrial environment may be difficult. So an intermediate step of testing the strategy in a laboratory setup, without conducting real cutting is proposed. Two mechatronic "Hardware in the Loop" simulators for chatter in turning and milling are presented, which simulate regenerative chatter experimentally without conducting real cutting tests. A simple cantilever beam, representing the MDOF dynamics of the machine tool structure constitutes the basic hardware part and the cutting process is simulated in real time on a DSP board. The values of the cutting parameters such as spindle speed and the axial width of cut can be changed on the DSP board and the closed loop interaction between the structure and the cutting process can be led to instability. The demonstrators are then used as test beds to investigate the efficiency of active damping, as a potential chatter stabilization strategy. Active damping is easy to implement, robust and does not require a very detailed model of the structure for proper functioning, provided a collocated sensor and actuator configuration is followed. The idea of active damping is currently being implemented in the industry in various metal cutting machines as part of the European Union funded SMARTOOL project (www.smartool.org), intended to propose smart chatter control technologies in machining operations.

In this work, we investigate the active vibration isolation and damping of sensitive equipment. Several single-axis isolation techniques are analyzed and tested. A comparison between the sky-hook damper, integral force feedback, inertial velocity feedback and LagLead control techniques is conducted using several practical examples. The study of single-axis systems has been developed and used to build a six-axis isolator. A six degrees of freedom active isolator based on Stewart platform has been designed manufactured and tested for the purpose of active vibration isolation of sensitive payloads in space applications. This six-axis hexapod is designed according to the cubic configuration; it consists of two triangular parallel plates connected to each other by six active legs orthogonal to each other; each leg consists of a voice coil actuator, a force sensor and two flexible joints. Two different control techniques have been tested to control this isolator : integral force feedback and Lag-Lead compensator, the two techniques are based on force feedback and are applied in a decentralized manner. A micro-gravity parabolic flight test has been clone to test the isolator in micro-gravity environment. ln the context of this research, another hexapod has been produced ; a generic active damping and precision painting interface based on Stewart platform. This hexapod consists of two parallel plates connected to each other by six active legs configured according to the cubic architecture. Each leg consists of an amplified piezoelectric actuator, a force sensor and two flexible joints. This Stewart platform is addressed to space applications where it aims at controlling the vibrations of space structures while connecting them rigidly. The control technique used here is the decentralized integral force feedback.

Phase Locked Loops(PLLs) are an integral part of almost every electronic system. Systems involving low frequency clocks often require PLLs with low bandwidth. The area occupied by the large loop filter capacitor and resistor in a low bandwidth PLL design makes the realization of traditional charge-pump PLL architecture impractical on a single die, mandating external components on the board. In order to maintain low loop bandwidth the designer is often forced to choose very low values of charge pump current which can lead to reliability issues. In this work, a semi-digital architecture for very low bandwidth monolithic PLLs is proposed. This architecture eliminates large components in traditional charge-pump PLL, thus allowing the realization of on-chip low bandwidth PLLs. A 2x2mm PLL is realized in 180nm CMOS with 75mHz bandwidth consuming 400μW power from 1.8V supply. The prototype PLL locks to an input clock of 1Hz and generates 20kHz output clock with a measured peak-to-peak jitter of 100ns. / Graduation date: 2013

This Master of Applied Science thesis presents an inverter control system design and implementation with active damping of LCL filter resonance for a single phase grid-connected Distributed Power Generation (DPGS). The focus of the thesis is to actively damp the LCL filter resonance while keeping inverter control variables well regulated. The mathematical model of the LCL filter is analyzed and the filter is designed. Then, a PLL, and a PI compensator in the synchronous reference frame, and a PR compensator in stationary reference frame along a notch filter in cascade are designed and implemented. System level simulation and implementation are conducted. The idea of systematic applying the low loss power conversion topology, effective grid condition detection, grid synchronization, and advanced signal processing theory provides some advantages for single phase grid-connected inverter control design to meet the standard specifications of the interaction between the DPGS and utility grid. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2014-06-26 17:06:03.693

Wheel loaders are under the influence of low frequency vibrations that may be harmful for the health of the operator, and for the productivity of the machine. The strong vibrations can significantly impact the operation of the machine since they are not equipped with wheel suspension systems and due to their work environment in rough terrains with uneven surfaces. The risk of spilling or dropping the load is also increased and they can introduce higher mechanical stress that can wear out parts faster. The focus of this thesis work is to develop an approach for damping these vibrations dynamically by improving the functionality of the electrohydraulic system in Volvo's prototype wheel loader LX1. The dynamic damping system controls the cylinder of the lift framework to make it behave as a damper. The system utilizes the lift cylinder pressure and piston position as feedback to adjust the oil flow in the cylinder using the proposed control system. Results indicate that the proposed technique is capable of attenuation that is comparable with the existing boom suspension system based on accumulators through simulations and experimental tests.

Aircraft and satellite structures are exposed to a wide range of temperatures during normal operation cycles. These fluctuations in temperature may result in significant changes of the structural dynamics. Aircraft, automotive, and satellite structures are also subject to various vibration sources. Passive and active vibration suppression techniques have been developed to minimize acoustic noise and fatigue stress damage. Featuring low weight solutions and high performance, active control techniques are becoming increasingly common. Structures with varying dynamics require more sophisticated active control techniques, such as adaptive control. This research uses a special vibration test rig for evaluating the performance of different vibration suppression systems on a representative aircraft panel. The test panel is clamped rigidly in a frame and can be excited in various frequencies with an electromagnetic shaker. To simulate temperature fluctuations the temperature on the panel can be increased up to 65°C (150°F). Smart material based sensors and actuators are used to interface the mechanical system with the electronic controller. The active controller utilizes three positive position feedback (PPF) filters implemented through a digital signal processor board. This research develops two different adaptation methods to perform vibration suppression in the presence of thermally induced frequency changes of the representative panel. To adjust the PPF filter parameters an open-loop adaptation method and an auto-tuning method are investigated. The open-loop adaptation method uses a measurement of the plate temperature and a look-up table with pre-determined parameters to update the filters accordingly. The auto-tuning methods identifies the frequencies of the poles and zeros in the structure's collocated transfer function. From the knowledge of the pole and zero locations the optimal PPF parameters are calculated online. The results show that both adaptation methods are capable of reducing the vibration levels of the test specimen over the temperature range of interest. Three PPF filters with parameter adaptation through temperature measurement achieve magnitude reductions of the resonance peaks as high as 13.6 decibel. Using the auto-tuning method resonance peak reductions up to 17.4 decibel are possible. The pole/zero identification routine proves to detect the frequencies correctly. The average identification error remained at around one percent even in the presence of external disturbances. / Master of Science

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A centenária indústria automotiva está passando por profundas transformações nos seus modelos de negócio, processos de desenvolvimento em produto e de produção. Inovações tais como veículos autônomos, transporte compartilhado, células de combustível, entre outras, apresentam-se aos estrategistas das montadoras como alternativas para gerar um diferencial competitivo e garantir a sobrevivência das empresas. Assim sendo, o entendimento dos mecanismos e fatores que influenciam na decisão de adoção de inovações em produto pelas montadoras é um tema relevante para a academia. Artigos sobre adoção de inovação em produto pelas organizações da indústria automotiva não são comuns na literatura, e quando realizados concentram-se no estudo de tecnologias de propulsão alternativa. Este estudo propõe, a partir de uma ampla revisão sistemática da literatura disponível sobre adoção de inovações pelas organizações, um modelo teórico contendo dimensões e fatores de influência na adoção de inovações em produto pelas montadoras de veículos, aplicando o modelo a um componente específico do automóvel, os chamados sistemas semiativos de amortecimento ou \'amortecedores inteligentes\'. Um diferencial do modelo conceitual desenvolvido foi a introdução da dimensão \'gestão da inovação\', analisando diversos fatores relacionados à estratégia tecnológica da montadora. A aplicação deste modelo foi realizada utilizando a metodologia de pesquisa qualitativa básica, por meio de entrevistas com funcionários de montadoras e fabricantes de sistemas de suspensão e amortecedores estabelecidos no mercado automotivo brasileiro. Uma pesquisa adicional foi realizada com o objetivo de identificar de que maneira a importância relativa entre os fatores que influem na adoção de inovações em produto pelas montadoras de veículos muda entre um país desenvolvido (EUA) e outro em desenvolvimento (Brasil). Dessa forma, o modelo conceitual desenvolvido foi aplicado por meio de entrevistas realizadas com funcionários de empresas do segmento automotivo estabelecidas no mercado dos EUA. As análises dos resultados permitiram identificar os fatores de maior influência na adoção da inovação em estudo pelas montadoras, bem como os fatores de menor influência. Análises comparativas foram realizadas entre estes fatores, para discutir as razões das semelhanças e diferenças entre eles. Esta tese produziu três artigos correlacionados entre si, o primeiro denominado Adoção de inovações em produto pelas organizações: Uma revisão sistemática de literatura. O segundo artigo foi intitulado como Adoção de inovações em produto na indústria automotiva: Modelo conceitual e aplicação para sistemas semiativos de amortecimento. O artigo Adoção de inovações em produto na indústria automotiva: Um estudo comparativo entre Brasil e EUA é o terceiro e último da tese. Estudos comparando a influência de fatores de adoção de inovação em produto pelas organizações foram realizados em outras áreas da tecnologia, porém artigos com comparações internacionais entre estes fatores não são comuns na literatura. Nenhum estudo sobre adoção de sistemas semiativos de amortecimento ou \'amortecedores inteligentes\' foi identificado na revisão de literatura realizada, o que evidencia o ineditismo deste trabalho de pesquisa. / The centenary automotive industry has gone through significant transformations in its business models, product development and production processes. Innovations like autonomous vehicles, transportation sharing, fuel cells, among others, show themselves as alternatives to create a competitive differential and assure companies survival. Therefore, the understanding of mechanisms and factors that influence automaker\'s decision to adopt product innovations is a relevant issue for the academy. Papers about product innovation adoption by organizations in the automotive industry are not common in the literature. When made, they focus mostly on the study of alternative propulsion technologies. This research proposes a theoretical model comprising dimensions and factors influencing product innovation adoption by automakers based on a broad literature systematic analysis about organizational innovation adoption. This model was applied to a specific automotive component, the so-called semi active damping systems or \"smart shock absorbers.\" The conceptual model presents the unpublished dimension \"innovation management\", which analyses several factors related to the automakers technological strategy. This research used basic qualitative analysis methodology and performed interviews with employees from automakers and suspension system manufacturers settled in the Brazilian automotive market. An extra research aimed to identify the way the relative importance between the factors that influence in the product innovation adoption by the automakers changes from a developed country (USA) and another country in development (Brazil). Interviews with employees from automotive companies settled in the USA market applied the conceptual model. The result of the analysis allowed the identification of the most influencing factors in the adoption of the product innovation by automakers, as well the less influencing factors. Comparative analyses between these factors were made in order to discuss the reasons of similarities and differences between them. This dissertation produced three correlated papers se, the first one is \"Product innovation adoption by organizations: A systematic literature review.\" The second one is \"Product innovation adoption in the automotive industry: Conceptual model and application for semi active damping systems.\" The third and last one of this dissertation is \"Product innovation adoption in the automotive industry: A comparative study between Brazil and USA.\" There are papers comparing the factors influencing product innovation adoption by organizations in other technology fields, but international comparisons between these factors are not common in literature. This research found no paper about semi active damping systems (\"smart shock absorbers\") in the literature review, which evidences the brand new characteristic of this dissertation.