High-precision motion platforms, such as industrial wire bonders used in semiconductor packaging, face demanding speed and accuracy requirements that challenge the inherent performance limits of Linear Time-Invariant (LTI) control, such as Bode's gain-phase relationship and the waterbed effect. Reset control strategies, particularly the Constant in Gain Lead in Phase (CGLP) architecture, offer a compelling solution by providing broadband phase lead without the gain penalty associated with linear lead filters. However, the inherent nonlinearity of reset elements introduces higher-order harmonics into the control loop. In precision motion control, these harmonics can shift reset timing, induce additional zero-crossings per excitation period, and invalidate the fundamental modeling assumptions of closed-loop sinusoidal-input describing function (HOSIDF) analysis.

To overcome these nonlinear limitations and prevent unreliable reset behavior, this thesis utilizes a shaping filter framework to strategically control the frequency-domain distribution of higher-order harmonics. By suppressing low-frequency harmonic distortion while preserving necessary phase lead around the crossover frequency, the proposed shaping filter formulation keeps zero-crossing proximity metrics within reliable bounds, thereby validating the underlying analytical HOSIDF modeling assumptions. Furthermore, this study investigates and validates the fundamental trade-offs between steady-state tracking precision and transient settling performance in shaped reset systems.

Building upon these theoretical insights, a systematic design guideline is established to synthesize reset controllers with shaping filters tailored to spectral error distributions across distinct motion phases. Following these proposed guidelines, a constraint-compliant reset controller featuring a sixth-order shaping filter was synthesized and evaluated on an industrial wire bonder motion stage. The experimental results demonstrate that the designed controller eliminates low-frequency disturbance energy without compromising closed-loop robustness margins, achieving an average improvement of 10.1% in stationary RMS tracking error and 7.2% in settling time across the complete set of operational references when compared to the state-of-the-art unshaped reset baseline. These findings confirm that performance-oriented nonlinearity distribution successfully reconciles transient speed with high steady-state positioning accuracy in industrial motion systems. ... Read more

This thesis investigates the industrial implementation of narrow-band multi-mode Active Vibration Control (AVC) for vibration attenuation of a state-of-the-art semiconductor wafer gripper. The wafer gripper is a wishbone like ceramic end-effector of the In-Vacuum Robot (IVR),  which is used in the wafer handler systems of lithography machines.
The structural dynamics, operational disturbances, and dominant noise sources are identified, providing the models required for loop shaping and Dynamic Error Budgeting (DEB). A DEB based simulation is constructed to predict the response at the gripper tips and identify the individual disturbance and noise contributions when active vibration control is introduced. The system requires multi-mode attenuation of the dominant vibrations while preserving the low-frequency dynamics. To meet these requirements, a narrow-band band-pass filter (NBPF) is adopted and compared with conventional Positive Position Feedback (PPF). An optimization based on DEB with loop shaping constraints is proposed and both optimized controllers predict a clear reduction in vibrations at the wafer gripper tip, while NBPF introduces less low frequency spillover than PPF. The results demonstrate the feasibility of narrow-band multi-mode active vibration control of a wafer gripper in an industrial environment and highlight the potential of combining DEB and loop shaping for active vibration control in industrial precision mechatronic systems. ... Read more

This thesis investigates a novel long-stroke linear actuator concept aimed at combining high force generation, low heat dissipation, and extended travel range for precision motion applications. As modern high-tech systems increasingly demand higher accuracy, throughput, and thermal stability, there is a growing need for alternative actuation principles that overcome the limitations of conventional technologies.

The research focuses on the development of a new magnetic actuator architecture that enables motion generation through controlled variation of magnetic interactions rather than conventional electromagnetic force generation. Multiple actuator concepts were analysed using analytical models and finite element simulations, after which the most promising design was optimized and experimentally validated.

A prototype actuator was designed, manufactured, and tested through a series of experiments ranging from single-module validation to a complete long-stroke demonstrator. The results demonstrate the feasibility of the proposed concept and show that long-stroke motion can be achieved while maintaining very low steady-state power dissipation. Although further improvements are possible in areas such as force density and motion smoothness, the work successfully establishes a proof of principle and provides a foundation for future development of efficient precision motion systems.
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High-precision motion systems are often limited by lightly damped flexible modes. These modes can increase tracking error, residual vibrations, and settling time, especially when higher motion speed and bandwidth are required.
This thesis examines if the vibrations of a flexure-based motion stage may be enhanced through the use of over-actuation and over-sensing. In essence, additional channels of actuation and sensing will allow flexible modes to be selectively observed and damped.
First, the mechanism is designed and optimized with the later vibration-control problem in mind. After this, actuator and sensor placement are investigated. Since single-point sensing and actuation are not sufficient for all modes, modal filtering is used to combine multiple sensor signals into mode-dominant virtual outputs. These virtual channels are then controlled using Positive Position Feedback and band-pass PPF controllers.
The proposed approach is then evaluated in the frequency domain and in the time domain. The results show how much vibration reduction can be obtained, while also showing the practical limitations caused by mode isolation quality and sensor noise.

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A tunable magnet reluctance actuator is an actuator that combines a hybrid reluctance actuator with a tunable permanent magnet as an alternative source of flux. Semi-static forces can be actuated by changing the magnetization of the magnet, after which a constant force can be generated without dissipating energy. In high-tech applications, this reduces heat dissipation, thereby reducing thermal expansion and increasing precision.

Tuning a magnet requires energy upfront, after which the power output of the combined reluctance actuator may be decreased. Next to semi-static situations where a constant force output is demanded, this may also be beneficial in dynamic applications.

This paper investigates optimal control of such an actuator, identifying the limits where a reduction in heat dissipation is possible. The main focus of this paper is on energy efficiency and dynamic effects while tuning the magnet.
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This paper presents an estimator synthesis methodology that uses an optimization approach to construct estimators which minimize the vertical acceleration response of a hydrofoil craft in ocean waves. The optimal estimator structure is identified, and a fundamental tradeoff between reducing wave-following motion and the required strut height is discovered and characterized. The developed methodology is validated through its application to a scale-model hydrofoil ship, resulting in a reduction of up to 70% in vertical acceleration magnitude compared to the ship's original estimator. ... Read more

Measurements and production at ever decreasing length scales give rise to increasing demands on active vibration isolation. Where conventional passive vibration isolation can typically isolate frequencies above 100 Hz sufficiently, high-end applications like gravitational-wave detection or semiconductor manufacturing require active vibration mitigation schemes. This drives the development of inertial sensors with good low-frequency (< 100 Hz) sensitivity. In these sensors, conventional passive readout is replaced by an active (force-feedback) topology, with interferometric readout. Although it is generally well established that an active readout topology is capable of achieving lower self-noise levels, no literature was found on a quantified sensitivity comparison of active and passive readout. Moreover, no literature was found quantifying the influence of control performance on the inertial sensor output signal robustness. This thesis aims to clarify what the influence of control performance is on the sensitivity and readout robustness of an active topology interferometrically read out inertial sensor. A comparison is made between active and passive readout, as well as multiple control stiffness levels in active readout. To do so, an experimental setup is designed and constructed. It is capable of digitally switching between passive and active readout, without the need for hardware changes. The digital implementation of the controller allows to measure the sensitivity for different control bandwidth in active readout. An incremental reduction in 1/f sloped readout noise spectrum is observed for incrementally increased control bandwidth. Compared to the highest noise spectrum associated with passive readout, a 100 fold noise reduction is measured for the 60 - 1000 Hz frequency band by applying the maximum performance controller in active readout. At 150 Hz this is a 1000 fold reduction in noise. Further improvements of the 1/f sloped readout noise are not measurable, as the spectrum is dominated by physical disturbances, ground motion and flat spectrum readout noise. In passive readout, the inertial sensor output signal relies on accurate estimation of the stiffness, damping and mass parameter of the mechanical design. Active readout is not dependent on the stiffness and damping parameter, but within the control bandwidth does require characterization of higher order parasitic modes of the mechanism. These modes are susceptible to frequency drift and can cause a change in the readout magnitude. Above the control bandwidth the dependency is reduced, similar to passive readout. The conflicting requirement on the desired control bandwidth, for maximum sensitivity and readout robustness, requires a trade-off to be made in controller design. The incremental reduction of the readout noise spectrum provides a quantitative relation between control performance and readout noise. It confirms a position and velocity dependent magnitude and demonstrates that benefits of reduced readout noise in the active topology already exist for the lowest control performance. These results strengthen our understanding of readout noise and output signal robustness in active topology interferometrically read out inertial sensors. ... Read more

Ongoing technological advancements demand the need for increasingly fast and precise motion systems, in which piezoelectric nanopositioners play a key role. However, due to their inherent dynamics, achieving open loop bandwidths close to the first resonance has proven to be challenging. An additional limitation arises from linear control, which is constrained by the Bode's phase-gain relationship and the waterbed effect. These limitations make achieving good tracking and disturbance rejection performance while maintaining stability and robustness at high bandwidth challenging.
Given the difficulty of achieving bandwidths close to the first resonance, this thesis investigates the even more challenging problem of extending the open loop bandwidth beyond the first resonance.
To address the challenge, a linear controller with barely positive stability margins is designed to achieve a bandwidth beyond the first resonance. A reset controller is then added on top of the linear controller to achieve stability and robustness without affecting the gain behavior. Unlike previous applications, here the nonlinearity introduced by the reset controller is extremely high, making the handling of higher-order harmonics particularly challenging. To address this, a novel shaping filter is introduced in order to reduce the magnitude of higher-order harmonics, along with pre- and post-filters which smooth the control action signal and keep it within the input saturation constraints.
The controller is fine tuned and validated in simulation using both frequency and time domain tools, and later implemented in an experimental test setup. Simulations show that achieving stable and robust post-resonance control is feasible, however mismatches between simulations and experiments appear during experiments. It is found that these are caused by an excessive amount of nonlinearities in the reset controller, making DF and HOSIDF tools from simulations unreliable. Nonetheless, experiments demonstrate that post-resonance control is feasible, and achievable only with reset control, outperforming the linear controllers currently used in industry. ... Read more

The relentless advancement of semiconductor and photovoltaic technologies has been driven by the demand for smaller, lighter, and more efficient electronic devices. A key trend accompanying this evolution is the reduction in substrate thickness, which lowers material costs and improves performance, alongside the increase in wafer diameter to enhance throughput. As a result, modern manufacturing increasingly relies on silicon wafers that are both thin and large in area. This combination fundamentally alters the mechanical behavior of wafers, resulting in them being highly compliant, fragile, and sensitive to external disturbances. Currently, conventional wafer handling systems rely on mechanical contact through robotic grippers and end-effectors, which have long been acceptable for mechanically robust substrates. However, for ultra-thin wafers, even minimal contact forces can induce warpage, micro-cracks, or fracture. Moreover, repeated dry contact unavoidably generates nanoparticles through friction and micro-wear, contributing to contamination that degrades yield and device reliability. In the literature, although contactless wafer handling approaches have been proposed to eliminate mechanical contact, they fail to achieve contactless positioning and transportation functionalities while remaining manufacturable and scalable to large working areas.

Therefore, this thesis addresses this gap by developing a scalable contactless wafer transportation system based on active air-bearing principles, with a strong emphasis on manufacturability and practical upscaling. As a first step, a novel contactless force actuator is introduced, featuring a continuous deformable air-bearing surface composed of compliant-mechanism-based unit cells. This design enables effective generation of viscous traction forces while significantly simplifying mechanical construction for easier fabrication and component integration, compared to prior discrete-cell architectures. Experimental validation demonstrates stable levitation, a fly height of 42.5 µm, and high traction force up to 90 mN, confirming the feasibility of the proposed approach.

To enable automated and efficient actuation of the compliant air-bearing system, a tunable hybrid reluctance actuator is developed. By exploiting adjustable magnetic reluctance, the actuator achieves passive and tunable stiffness reduction with high force efficiency and low disturbance transmissibility. Experimental results demonstrate substantial stiffness reduction up to 88.5%, while also revealing the necessity of closed-loop control to mitigate dynamic instabilities at high reduction levels.
Building on these components, a modular contactless wafer transportation system is realized through redesigned airflow pathways and integrated vacuum resistances, ensuring stable levitation even when the wafer partially uncovers the bearing surface. Closed-loop experiments confirm reliable contactless transportation and ±2.5 µm positioning accuracy. Finally, the modular concept is extended to a large-scale system by integrating multiple modules into a unified flat surface. Experimental results validate the scalability of the design, improved manufacturability, and highlight surface quality as a critical factor governing fly height, vacuum consumption, and traction force.

Overall, this work establishes a viable foundation for scalable, manufacturable contactless wafer transportation. While further improvements in surface finishing, vacuum management, actuator capability, and control strategies are required, the presented concepts represent a significant step toward practical, high-performance contactless handling solutions for next-generation semiconductor manufacturing. ... Read more

Piezoelectric nanopositioning systems are indispensable in high-precision applications such as Atomic Force Microscopy (AFM), wafer metrology, and medical applications. Enhancing their throughput while maintaining precision presents significant challenges due to lightly damped resonant modes and substantial dynamic variations associated with payload changes. Contemporary approaches, involve the tuning of motion controllers in a dual-closed-loop architecture that incorporates active damping to achieve higher bandwidths. Although these methods function adequately for nominal systems, they fail to meet performance requirements under system variations in resonance modes caused by payload changes and often overlook higher-order dynamics and delays. This research introduces a robust control framework that synthesises H-infinity and Mu synthesis-based controllers by shaping sensitivities within a dual-closed-loop, considering payload variations and prominent higher-order system dynamics. Systematic design guidelines for weighting functions are established to synthesise robust controllers that meet specified performance criteria. The proposed framework is experimentally validated on an industrial nanopositioning system, demonstrating robust performance despite dynamic variations induced by varying payloads. ... Read more

With the increasing demand for precision and accuracy in the high-tech industry, limiting thermal dissipation has become a critical challenge. In high-precision positioning systems, heat dissipation causes thermal expansion of components, which degrades positioning accuracy and ultimately compromises overall performance. These shortcomings led to the development of a Tunable Magnet Actuator(TMA). TMA can sustain the required force without a continuous current supply by utilizing the tunable magnets, which can be magnetized along different states. To minimize thermal dissipation, accurate control of the magnet’s magnetization state is essential. Existing magnetization state tuning methods, however, are subpar, falling short in efficiency, accuracy, or both simultaneously. Moreover, many of the existing state-of-the-art control algorithms utilize the look-up table, resulting in a feedforward control. To generate these look-up tables, a comprehensive data collection is required, as well as the calibration of the obtained results, which is undesirable. To mitigate this, a feedback control strategy similar to the traditional Pulse Width Modulation algorithm has been developed. While accurate, the PWM control remains highly inefficient. The aforementioned necessitates the development of a new feedback control algorithm that would be as accurate but more efficient. The neural networks used for the prediction of the hysteresis loops have been largely explored in the past years. However, the implementation of the neural network in tandem with a real-time control remains novel. This thesis proposes a new neural network-based PWM control algorithm to address the challenges in accurately controlling the remanent state of the tunable magnet. Initially, a system characterization is done to train the neural network model. Afterwards, a new control algorithm that utilizes the developed neural network models is created and implemented. ... Read more

Precision engineering applications, such as atomic force microscopes and semiconductor motion stages, demand high accuracy in tracking and disturbance rejection, often limited by the waterbed effect and gain-phase constraints in linear control systems. This thesis introduces nonlinear control designs leveraging Fractional-order Hybrid-Integrator-Gain Systems (FO-HIGS) to overcome these limitations, providing tunable phase lead with reduced higher-order harmonics compared to traditional integer-order HIGS.

Two novel FO-HIGS-based controllers are proposed: (1) An enhanced CgLp filter integrated with PID control to improve low-frequency tracking by compensating phase lag through parameter tuning (e.g., fractional order α and corner frequency), minimizing parasitic nonlinear effects via simulation-based higher-order sinusoidal-input describing function (HOSIDF) analysis and pseudo-sensitivity evaluation. (2) A FO-HIGS-based LPF for superior high-frequency noise attenuation, achieving lower cumulative power spectral density than linear counterparts.

Simulations and experiments on a linear-motor-actuated motion stage validate the designs, demonstrating improved performance in reference tracking and disturbance rejection while maintaining stability. ... Read more

Piezoelectric nanopositioning systems are widely used in applications demanding high-speed and high-precision motion. Their closed-loop performance is often constrained by lightly damped modes and strong inherent nonlinearity which limit achievable bandwidth and tracking accuracy. Conventional approaches such as notch filters can mitigate resonances but struggle to provide robust damping without sacrificing bandwidth.

This thesis investigates the combination of active damping control and nonlinear reset control to overcome the limitations of linear time-invariant (LTI) feedback methods. A dual-loop control architecture is proposed, employing an active damping controller to suppress dominant modes and enable higher bandwidths, together with a nonlinear CgLp reset controller to recover the phase lag introduced by the damping control. Unlike typical applications, the high nonlinearity of piezoelectric systems makes introducing additional nonlinearity from reset control challenging, particularly when aiming for large phase lead. To address this, a dedicated shaping filter is designed to limit higher-order harmonics and prevent multiple resets, enabling effective phase compensation of up to 20°.

The control architecture is optimized in the frequency domain and validated through simulation and experiments on a piezoelectric nanopositioning platform. Results demonstrate significant improvements in both open- and closed-loop bandwidth and tracking performance compared to conventional LTI controllers, while maintaining stability and robustness. The shaping filter effectively reduces harmonic distortion, ensuring the practical viability of combining reset control with active damping in highly nonlinear, lightly damped systems.

This work shows that the integration of reset control with shaping filter, within a dual-loop active damping framework, can push the performance of nanopositioning systems beyond the traditional LTI control limits. ... Read more

Automated driving systems are expected to be revolutionary technologies that will reconstruct mobility by improving safety and efficiency. Among the components of automated driving systems, motion planning plays a critical role as it determines how the vehicle reaches its target location from a given origin. The current challenges of motion planning lie in real-time performance and passenger comfort, which is also the main objective of motion planning algorithms. These challenges often occur simultaneously but are treated separately. Neither of these challenges could be solved at a global level of motion planning, which is mainly concerned with route selection and travel time minimization, and could be computed in advance. Consequently, this thesis primarily focuses on local motion planning related to the maneuvering of a vehicle, ensuring real-time performance and passenger comfort.
To address these two challenges, an extended tentacle-based motion planning algorithm is developed. This is an interpolation curve-based algorithm that could work in real-time because there are no optimizers or learning processes that cost a lot of computational resources in the algorithm. The most important factor that affects passenger comfort in a ride is jerk, which is also known as the time derivative of acceleration. The proposed algorithm manages to control the jerk in both lateral and longitudinal directions, thus ensuring ride comfort. Begin with the current state of the vehicle, including velocity, attitude, and steering angle, a series of geometry curves called tentacles is generated and evaluated. The maximum lateral jerk is limited during tentacle generation to avoid excessive impact on passengers during maneuvering.To address these two challenges, an extended tentacle-based motion planning algorithm is developed. This is an interpolation curve-based algorithm that could work in real-time because there are no optimizers or learning processes that cost a lot of computational resources in the algorithm. The most important factor that affects passenger comfort in a ride is jerk, which is also known as the time derivative of acceleration. The proposed algorithm manages to control the jerk in both lateral and longitudinal directions, thus ensuring ride comfort. Begin with the current state of the vehicle, including velocity, attitude, and steering angle, a series of geometry curves called tentacles is generated and evaluated. The maximum lateral jerk is limited during tentacle generation to avoid excessive impact on passengers during maneuvering.
In most motion planning algorithms, geometry path planning and speed planning are treated separately. However, in the proposed planning algorithm, the speed profile is generated based on the selected best tentacle, thus making the speed profile more rational and adaptable to current maneuvers. In addition, the target speed of the speed profile is decided based on road curvature and traffic conditions, ensuring safety and avoiding wasting time on some low-speed traffic participants. More importantly, the speed profile limits the maximum longitudinal jerk, thus making jerk limited in all directions and ensuring passenger comfort.
To evaluate the performance of the proposed motion planning algorithm, simulations using a high-fidelity vehicle model through IPG CarMaker and MATLAB/Simulink are implemented under various conditions. Because this report does not focus on the design of the path-following controller, the vehicle directly uses the output of the planner as control input during simulations. Even so, the algorithm still manages to complete static and dynamic obstacle avoidance as well as adaptive following and overtaking maneuvers at various speed ranges and road conditions. A virtual map of part of the campus of TU Delft is also constructed using Carmaker and used for validation of the proposed algorithm under urban traffic conditions. The proposed algorithm works effectively in complex environments and can operate in real time at a frequency of $20$ $Hz$ while constraining the total jerk.
This research illustrated the capability of the developed tentacle-based motion planning algorithm to ensure passenger comfort and safety under various traffic conditions. Although primarily serving as a concept emphasizing feasibility through simulations rather than immediate on-road verification, the proposed algorithm establishes a foundation for future real-vehicle implementation, thus contributing towards resolving normal driving conditions essential for achieving fully automated driving. ... Read more

Hydrofoil vessels show unstable behaviour when operating in foilborne condition. Therefore, an active control system (ACS) is used. Designing an ACS requires an accurate dynamic model. While many theoretical frameworks have been proposed, experimentally validated models for hydrofoil vessels remain limited. This study aims to identify the pitch and height dynamics of the Flying Fish 1 hydrofoil demonstrator. For this, the closed loop system identification (CLSI) method in combination with a multisine excitation signal is used. The identified dynamics will be compared to a parametric dynamical model derived from literature. And, using the resulting frequency domain data, an attempt is made to improve the control performance of the pitch and height control loops.

The CLSI method, in combination with the multisine disturbance signal proved to be an effective method. Accurate frequency domain results were obtained within the frequency range of 1 to 10 Hz. Within this range, the parametric dynamic model aligned well with experimental data. The experiment was repeated three times at 4.0, 4.5 and 5.0 m/s and resulted in similar responses, aside from a negative trend in magnitude at increasing velocities. The use of frequency domain tuning led to an increase in phase margin for the pitch controller and a bandwidth increase of 667\% for the height controller. The results show that CLSI is a powerful tool in estimating the dynamics of a hydrofoil vessel, laying the foundation for advanced control strategies and improved system performance. ... Read more

Linear controllers are widely preferred in the industry for controlling motion platforms used in semiconductor and electronics manufacturing machines. However, as production demands for semiconductor devices increase, the performance of linear controllers reaches a plateau due to their intrinsic limitations, making further improvements increasingly difficult. Thus, the reset control has been explored as a potential solution as it can overcome the limitations and it consists of the frequency domain analysis tools.

Past research has shown that the CgLp (Constant in gain, Lead in phase) is the most advanced reset based filter and has shown performance improvements for an industrial machine. The non-linearity of these filters, which gives an advantage over linear filters, also makes their placement within a control loop highly critical. While the inherent non-linearity of these filters provides certain advantages, it can also be detrimental to system performance.

This thesis aims at developing architectures based on sequencing strategies to improve the performance of reset based filters by optimally utilizing the non-linearity. Also, the disadvantages of existing frequency domain analysis methods have been identified. Finally, the method of filtered architecture which can shape the non-linearity of reset based filters have been explored.
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In industrial settings that necessitate high precision and speed, particularly within the semiconductor manufacturing industry, linear control solutions are frequently employed due to their intuitive tuning methods, namely through frequency-domain analysis, and their compatibility with tuning based on experimental measurements of the systems, Frequency Response Function (FRF). Nonetheless, inherent limitations exist, such as Bode’s phase-gain relationship and the waterbed effect, which constrain their achievable performance. Consequently, non-linear control solutions must be considered. Reset control presents an interesting solution as it has been proven to outperform linear controllers and also allows for frequency-domain analysis based on FRFs. Nonetheless, this kind of analysis is subject to a set of assumptions. The most recent reset control element developed for broadband phase compensation, the Parallel Constant in Gain Lead in Phase ((P)CGLP), presents several benefits towards meeting the required assumptions. However, tuning a control architecture that includes this element can be a challenging and time-consuming task, as no tuning rules have currently been established. This research focuses on the development of an automatic tuning framework to tune not only control architectures that contain the (P)CGLP element but also any reset control structure. The tuning framework was validated in an industrial wire bonding machine against an optimized linear control solution developed by the manufacturer. An average improvement in settling time of 7.1% was achieved and an average improvement of 13.5% in the RMS value of the error signal across different operational scenarios. The proposed framework proved to be capable of tuning reset controllers that outperform equally optimized linear solutions while maintaining a similar tuning workflow and not requiring additional expertise. ... Read more

Vibrations deteriorate the performance of machines and instruments, especially when high precision and efficiency are required. Multiple approaches for vibration mitigation exist, mostly constituting separate bodies of research. This thesis establishes a connection between the active vibration control practice, advances in other control fields, and metamaterials research. To this end, three research gaps are addressed.

First, in Chapter 2, the design requirements of active vibration control are expressed in the frequency domain, using the loop-shaping approach commonly used in motion control. The use of the proposed approach is shown in the experimental evaluation of a vibration isolation system based on piezoelectric stack actuators.

Second, the loop-shaping approach is related to the design for bandgap in active metastructures. Chapter 3 adopts a modal analysis approach for finite metamaterial beams, relating the underlying control problem to the active damping of a single-degree-of-freedom system by assuming an infinite number of infinitesimally small transducer pairs distributed along a beam. This allows the application of design methods developed in the preceding chapter. The experiments demonstrate that controllers initially developed for damping resonance peaks can effectively induce bandgaps, even in structures featuring a small number of sparsely placed transducer pairs. Chapter 4 studies when the obtained models and approximations are accurate, highlighting the correlation between the minimal number of transducers required for model accuracy and the dominant vibration mode within the controller's targeted frequency range.

Third, the frequency-domain approach is applied for the design of fractional order and reset controllers for vibration mitigation to relax the limitations imposed using low-order linear controllers. In Chapter 5, a design for a fractional-order resonant element tailored for AVC, which preserves the characteristics of its integer-order counterpart but provides greater design freedom, is presented and evaluated in a simplified vibration isolation system. In Chapter 6, the same element is implemented within a unit cell of a granular metamaterial. For such a fractional-order metamaterial, both the dispersion characteristics of the infinite structure and the transmissibility of a finite chain are presented.

The use of nonlinear elements, like reset systems, poses additional challenges in vibration control. Since an exact frequency-domain representation of such elements does not exist, their behaviour is approximated using the describing functions. While this enables the loop-shaping design, the describing function approximation does not represent the system well in the presence of wide-band excitations and multiple resonance peaks in the plant. Chapter 7 explores how such conditions influence the reset elements and how to ensure that the use of reset is still beneficial. Additionally, assessing the stability of a reset system solely based on controller dynamics and experimentally measured plant frequency response is an open problem. To address this, the Negative Imaginary systems approach for stability analysis, originally developed for AVC of flexible systems with uncertain dynamics, is extended to reset systems in Chapter 8. ... Read more

This dissertation focuses on the frequency response analysis and design of Linear Time- Invariant systems (LTI) reset feedback control systems for precision motion applications. In the precision motion industry, there is a growing demand for control systems that deliver higher positioning resolution, faster response, and enhanced stability. However, inherent limitations in linear controllers, such as the “waterbed effect” and the Bode phase gain trade-off, limit their performance, posing challenges in meeting these evolving requirements.

Reset feedback control has emerged as an effective solution to address the limitations of linear control systems in precision motion applications. The practical implementation of control strategies relies on reliable analysis methods. Among these, frequency response analysis stands out as an effective and widely utilized method across industries. However, existing frequency response analysis methods for both open-loop and closed-loop reset control systems face challenges, including accuracy limitations and restrictions to specific control system structures. The first category of contributions in this dissertation addresses these challenges by introducing frequency response analysis methods for open-loop and closed-loop Single-Input and Single-Output (SISO) LTI reset control systems within a generalized control system structure. Moreover, to further realize the potential of reset control, the second category of contributions focuses on proposing novel reset control designs to enhance system performance. The content is organized into nine chapters…
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