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Liquid crystalline polymers are attractive materials for untethered miniature soft robots. When they contain azo dyes, they acquire light-responsive actuation properties. However, the manipulation of such photoresponsive polymers at the micrometer scale remains largely unexplored. Here, uni- and bidirectional rotation and speed control of polymerized azo-containing chiral liquid crystalline photonic microparticles powered by light is reported. The rotation of these polymer particles is first studied in an optical trap experimentally and theoretically. The micro-sized polymer particles respond to the handedness of a circularly polarized trapping laser due to their chirality and exhibit uni- and bidirectional rotation depending on their alignment within the optical tweezers. The attained optical torque causes the particles to spin with a rotation rate of several hertz. The angular speed can be controlled by small structural changes, induced by ultraviolet (UV) light absorption. After switching off the UV illumination, the particle recovers its rotation speed. The results provide evidence of uni- and bidirectional motion and speed control in light-responsive polymer particles and offer a new way to devise light-controlled rotary microengines at the micrometer scale.

Submillimeter-scale electrically driven micromotors have the potential to revolutionize micro-robotic systems, but difficulties in their fabrication processes and unknown physical phenomena prevent their development. In this paper, we propose a submillimeter-scale rotary piezoelectric ultrasonic motor with the smallest stator (0.41 mm × 0.41 mm × 0.25 mm) reported to date. The micromachining technologies enable the creation of tiny components. A micromanipulator that can control a small amount of adhesive of sub-milligram order engenders success in manufacture of the stator. Several experiments clarify the submillimeter-scale physical behaviors, such as the admittance and the quality factor. With appropriate piezoelectric materials, submillimeter-scale ultrasonic motors are built and characterized using a rotor with 0.15 mm diameter. The motor with typical hard PZTs demonstrated maximum torque of 5.4 nNm and a maximum angular velocity of 714 rad/s at an applied voltage with amplitude of 44.8 Vp-p. Furthermore, another motor with single-crystal PMN-PT piezoelectric elements presented the possibility of low-voltage actuation. These submillimeter-scale ultrasonic motors were compared with existing comparable-size micromotors.

Conventional bending sensors mainly utilize electrical, chemical, or optical signals to control the bending action of the soft pneumatic bending actuator. Recently, image processing techniques have emerged as an alternative for detecting such bending movements. However, their fabrication process and measurement methodology still remain intricate. In this article, a novel vision-based bending sensor for the pneumatic network (PneuNet) actuator based on ArUco marker detection is proposed. The fabrication of the proposed sensor is simplified through the use of 3-D-printed or outsourced parts, making the proposed sensor’s design and fabrication much easier. The PneuNet is connected to a rotating disk featuring an ArUco marker via an inextensible Kevlar cable. Thus, the bending of the PneuNet is converted to the one degree of freedom (DoF) rotation of the ArUco marker, which can then be monitored by the camera module. Experiments show that a linear correlation between the bending and ArUco marker angles is characterized despite the hysteresis of the PneuNet, proving the proposed sensor’s usability. Moreover, control of multiple actuators is feasible as long as the markers are within the field of view (FOV) of the camera module. Finally, based on the mechanical detection method of the sensor, tracking of the PneuNet’s tip displacement upon the exertion of external force is also showcased to utilize the proposed sensor’s versatility further.

Liquid crystalline polymers are attractive materials for untethered miniature soft robots. When they contain azo dyes, they acquire light-responsive actuation properties. However, the manipulation of such photoresponsive polymers at the micrometer scale remains largely unexplored. Here, uni- and bidirectional rotation and speed control of polymerized azo-containing chiral liquid crystalline photonic microparticles powered by light is reported. The rotation of these polymer particles is first studied in an optical trap experimentally and theoretically. The micro-sized polymer particles respond to the handedness of a circularly polarized trapping laser due to their chirality and exhibit uni- and bidirectional rotation depending on their alignment within the optical tweezers. The attained optical torque causes the particles to spin with a rotation rate of several hertz. The angular speed can be controlled by small structural changes, induced by ultraviolet (UV) light absorption. After switching off the UV illumination, the particle recovers its rotation speed. The results provide evidence of uni- and bidirectional motion and speed control in light-responsive polymer particles and offer a new way to devise light-controlled rotary microengines at the micrometer scale. © 2023 Wiley-VCH GmbH.

[Resumen] Los actuadores blandos, es decir, los fabricados con materiales altamente deformables, tienen un gran potencial en aplicaciones biomédicas, debido principalmente a su bajo coste y peso, reducido tiempo de respuesta, facilidad de fabricación, alto grado de maniobrabilidad que ofrecen y seguridad en términos de biocompatibilidad. El objetivo de este proyecto es desarrollar un catéter robótico a pequeña escala con una punta dirigible para realizar cirugías cardiacas. Como primer paso para validar el concepto, este trabajo se centra en el diseño de un actuador hidráulico blando para controlar la dirección de la punta del catéter. Las simulaciones por elementos finitos permiten predecir con precisión el complejo comportamiento de los materiales hiperelásticos, lo que facilita el diseño y la optimización del uso de materiales. En este trabajo se emplean simulaciones en COMSOL Multiphysics para, por un lado, conocer cómo evoluciona el actuador bajo las deformaciones tridimensionales y, por otro, optimizar la geometría del actuador en términos de desplazamiento de la punta para una presión determinada. Asimismo, se describe el método de fabricación de los primeros prototipos., [Abstract] Soft actuators, i.e., those made of highly deformable materials, have great potential in biomedical applications, mainly due to their low cost and weight, reduced response time, ease of fabrication, high degree of maneuverability and safety in terms of biocompatibility. The objective of this project is to develop a small-scale robotic catheter with a steerable tip to perform cardiac surgery. As a first step to validate the concept, this work focuses on the design of a soft hydraulic actuator to control the direction of the catheter tip. Finite element simulations allow accurate prediction of the complex behavior of hyperelastic materials, which facilitates design and optimization of material usage. In this work, simulations in COMSOL Multiphysics are used to understand how the actuator evolves under three-dimensional deformations and to optimize the actuator geometry in terms of tip displacement for a given pressure. The manufacturing method of the first prototypes is also described.

The convergence of nano-, bio-, and information technologies is based on the understanding of complex hierarchical structures and systems, as well as on the material unity at the nanoscale and on technology integration from that scale. A growing interest in these technologies is a result of their potential to provide solutions to numerous societal challenges, such as advanced healthcare, environmental remediation, sustainable development, and adoption of cyber-physical systems based on the Internet of Things and the Internet of Systems. Taking into account that hybrid nanomaterials possess extraordinary physical and chemical properties derived from their size in the nanoscale, the aim of this work is to present the connection between processing parameters and multifunctional properties of nano scale hybrid materials, focusing on the study of ceramic-polymer structures before they can be nano-engineered into functional devices. The unique functionality of these nanostructures has enabled their applications in numerous devices such as: micro and nano-electro-mechanical systems (MEMS/NEMS), sensors, microactuators, surface acoustic wave devices, polymer electrolyte membrane fuel cells, switches, thermistors, resonators and filters, electrooptic devices, etc. In this study special attention has been paid to their applications in the fields of electronics, biotechnology, environmental protection and remediation.

Safety is crucial for quadrotor flight, especially when the system suffers one rotor loss and disturbance. To enable quadrotors to survive in these worst cases, this paper proposes a Simultaneous Planning And Execution (SPAE) system strategy. First, the Euler angles under different equilibrium states are solved to ensure the feasibility of the control input when the quadrotors encounters rotor loss and disturbance. Based on the admissible Euler angle solutions, an emergency control strategy is proposed to realize desired angles by recalculating the desired trajectory and the disturbance observer. Meanwhile, this control strategy sacrifices the yaw angle control to handle further underactuation of the system caused by complete rotor failure. In addition to rotor losses, unsafe flight caused by actuator saturation is considered in the SPAE strategy where the planning and execution are simultaneous. As a decision maker, the planning considers the current disturbances and constraints of actuators, then generates a feasible trajectory for controller execution. As an executor of the decision, the controller feedback estimated disturbance information to the trajectory planning, which can help trajectory planning make admissible decisions consistent with the current situation. As a result, the actuator saturation caused by the underestimation of disturbance can be avoided under a feasible regenerated trajectory. Extensive simulations and experiments prove the validity of the proposed SPAE strategy. IEEE

The very recent concept of metaverse highlights the importance of virtual reality (VR) and augmented reality (AR), which associates with a wide variety of applications in entertainment, medical treatment, and human-machine interfaces. The current VR/AR technologies mainly rely on visual interaction, while immersive experience in VR and AR highly demands sensational feedback, such as haptic and temperature with noticeable quality in wearable or even skin-integrated formarts. In this article, we report a wearable and flexible haptic interface based on electromagnetic vibrotactile actuators with high wearability and stability. By adopting double layers of copper (Cu) coils at the top and bottom of the magnetic disc, an enhanced electromagnetic field can be generated. Additionally, the intensity of the haptic feedback can be modulated according to sensed pressure in the virtual world by adjusting the value of power input and frequency. The actuator exhibits high stability and tolerance upon environmental, cyclic, and impact resistance tests. Finally, the actuators are developed into the soft VR interfaces for mounting on forearms, fingers, and hands to verify their superiority over conventional haptic actuators in the aspects of performance and applications. © 2014 IEEE.

This work focuses on how to implement modern online-reactive control strategies developed for robots with backdrivable actuators on robots with conventional high gear ratio, position controlled motors. The vast majority of robots today have motors like this. Robots with torque-controlled proprioceptive actuators which are backdrivable and have high torque density are currently being developed. However, there are still many situations in which robots with more traditional position-controlled, high gear-ratio actuators are more appropriate. For example, since actuator weight scales exponentially with size while torque scales linearly, it is still cost-prohibitive to use torque control for robots that are large and or very tall. In addition, backdrivable actuators typically require low latency communication to function and consume much more current than high gear ratio actuators because they are dampening motion during operation. Both restrictions can make these motors prohibitively difficult to use and expensive to obtain. For these reasons, research on robots with non-backdrivable actuators is still valuable. Many of the basic assumptions made for control systems are violated when using these actuators; with the intent to develop robots capable of dynamic, robust locomotion, we will attempt to categorize these obstacles, record the attempts to overcome them, explain why or why not the interventions were successful and finally, recommend paths of inquiry for future work. Contributions from this thesis project include creation of a bipedal robotic platform for locomotion experiments, multiple gait generators for bipedal robots with non-backdrivable actuators which were tested on physical hardware, investigation of methods to compensate for non-backdrivability during locomotion and several principles for designing control systems for dynamic, stable locomotion. Supplemental media included: - dcm-disturbance-rejection-sim.mp4 - dcm-omnidirectional-walking-sim.mp4 - model

The objective of this bachelors thesis is to conduct a comprehensive analysis of the communication subsystems in the UHF, S, and X bands of the 3Cat-8 mission. This mission aims to develop a satellite under the CubeSat standard that allows the study of different physical phenomena, such as the effects of auroral emissions on wave propagation through the ionosphere. Furthermore, this project also includes the design of an S-band patch antenna, both to understand the design of a space application antenna and to implement it on the same satellite and compare it with other commercial options. In addition, the polar orbit described by the satellite results in limited opportunities for data downlink, making it necessary to design and dimension magnetic actuators to enable the satellite to point towards the ground station. This document addresses the study, design, and manufacturing of these elements in order to enable the satellite to aim its antennas at the ground station. Overall, this work represents a significant contribution to the 3Cat-8 mission. Throughout this project, various activities encompassing the fields of aerospace engineering and telecommunications have been carried out.

Direct ink writing (DIW) is a promising additive manufacturing (AM) technique in the field of microsystems technology due to the potential for high detail resolution and the wide choice of materials suitable for the technique. In this study, inks of polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) as well as composite inks with reduced graphene oxide (PVDF-TrFE-rGO) were developed and adapted for continuous flow DIW. The composite PVDF-TrFE-rGO inks achieved percolation after 1.5 wt% and electrical conductivity of 2.8 S/cm at the highest loading investigate in this study (7 wt%). The inks were successfully printed with minimum nozzle diameter of 40 & mu;m on different substrates including glass, metal and a nitrile elastomer. It was also demonstrated that the inks can be used to create a fully 3D-printed piezoelectric device with the predicted response, i.e. the fabrication technique did not deteriorate the functionality of the device. The conductive composite ink was successfully utilized as an effective electrode in the device. It was therefore demonstrated that by combining materials, such as the composite PVDF-TrFE-rGO ink and the co-polymer PVDF-TrFE with additive manufacturing techniques, the fabrication of low-cost, versatile devices can be achieved.

Direct ink writing (DIW) is a promising additive manufacturing (AM) technique in the field of microsystems technology due to the potential for high detail resolution and the wide choice of materials suitable for the technique. In this study, inks of polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) as well as composite inks with reduced graphene oxide (PVDF-TrFE-rGO) were developed and adapted for continuous flow DIW. The composite PVDF-TrFE-rGO inks achieved percolation after 1.5 wt% and electrical conductivity of 2.8 S/cm at the highest loading investigate in this study (7 wt%). The inks were successfully printed with minimum nozzle diameter of 40 & mu;m on different substrates including glass, metal and a nitrile elastomer. It was also demonstrated that the inks can be used to create a fully 3D-printed piezoelectric device with the predicted response, i.e. the fabrication technique did not deteriorate the functionality of the device. The conductive composite ink was successfully utilized as an effective electrode in the device. It was therefore demonstrated that by combining materials, such as the composite PVDF-TrFE-rGO ink and the co-polymer PVDF-TrFE with additive manufacturing techniques, the fabrication of low-cost, versatile devices can be achieved.

Direct ink writing (DIW) is a promising additive manufacturing (AM) technique in the field of microsystems technology due to the potential for high detail resolution and the wide choice of materials suitable for the technique. In this study, inks of polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) as well as composite inks with reduced graphene oxide (PVDF-TrFE-rGO) were developed and adapted for continuous flow DIW. The composite PVDF-TrFE-rGO inks achieved percolation after 1.5 wt% and electrical conductivity of 2.8 S/cm at the highest loading investigate in this study (7 wt%). The inks were successfully printed with minimum nozzle diameter of 40 & mu;m on different substrates including glass, metal and a nitrile elastomer. It was also demonstrated that the inks can be used to create a fully 3D-printed piezoelectric device with the predicted response, i.e. the fabrication technique did not deteriorate the functionality of the device. The conductive composite ink was successfully utilized as an effective electrode in the device. It was therefore demonstrated that by combining materials, such as the composite PVDF-TrFE-rGO ink and the co-polymer PVDF-TrFE with additive manufacturing techniques, the fabrication of low-cost, versatile devices can be achieved.

Direct ink writing (DIW) is a promising additive manufacturing (AM) technique in the field of microsystems technology due to the potential for high detail resolution and the wide choice of materials suitable for the technique. In this study, inks of polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) as well as composite inks with reduced graphene oxide (PVDF-TrFE-rGO) were developed and adapted for continuous flow DIW. The composite PVDF-TrFE-rGO inks achieved percolation after 1.5 wt% and electrical conductivity of 2.8 S/cm at the highest loading investigate in this study (7 wt%). The inks were successfully printed with minimum nozzle diameter of 40 & mu;m on different substrates including glass, metal and a nitrile elastomer. It was also demonstrated that the inks can be used to create a fully 3D-printed piezoelectric device with the predicted response, i.e. the fabrication technique did not deteriorate the functionality of the device. The conductive composite ink was successfully utilized as an effective electrode in the device. It was therefore demonstrated that by combining materials, such as the composite PVDF-TrFE-rGO ink and the co-polymer PVDF-TrFE with additive manufacturing techniques, the fabrication of low-cost, versatile devices can be achieved.

Direct ink writing (DIW) is a promising additive manufacturing (AM) technique in the field of microsystems technology due to the potential for high detail resolution and the wide choice of materials suitable for the technique. In this study, inks of polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) as well as composite inks with reduced graphene oxide (PVDF-TrFE-rGO) were developed and adapted for continuous flow DIW. The composite PVDF-TrFE-rGO inks achieved percolation after 1.5 wt% and electrical conductivity of 2.8 S/cm at the highest loading investigate in this study (7 wt%). The inks were successfully printed with minimum nozzle diameter of 40 & mu;m on different substrates including glass, metal and a nitrile elastomer. It was also demonstrated that the inks can be used to create a fully 3D-printed piezoelectric device with the predicted response, i.e. the fabrication technique did not deteriorate the functionality of the device. The conductive composite ink was successfully utilized as an effective electrode in the device. It was therefore demonstrated that by combining materials, such as the composite PVDF-TrFE-rGO ink and the co-polymer PVDF-TrFE with additive manufacturing techniques, the fabrication of low-cost, versatile devices can be achieved.

Nickel-titanium (NiTi) shape memory alloy (SMA) films are already implemented into microelectromechanical system (MEMS) devices such as sensors, actuators, and implantable medical devices. In this thesis, I used DC magnetron sputter deposition to study the influence of film composition, microstructure, and annealing conditions on the stability of the phase transformation for the NiTi-based SMA thin films TiNiCu, TiNiCuCo, and TiNiHf. SMAs are a type of smart material that can undergo stress or temperature-induced solid-to-solid phase transformation between two different crystalline phases. In NiTi-based SMAs, the two phases are known as martensite with a monoclinic crystalline structure and austenite with a cubic crystal structure. The temperature-induced phase transformations can be used to switch between the martensite and austenite phases, and thus switch between two sets of material properties in the SMA. For example, in NiTi-based SMAs the Young’s modulus, electrical resistivity, and coefficient of thermal expansion of the austenite phase are typically 2X larger than that of the martensite phase. The transformation temperatures, recovery strains, enthalpy of transformation, and fatigue properties of NiTi SMAs can be tuned by alloying NiTi with other elements like copper (Cu), cobalt (Co), and hafnium (Hf). For example, certain compositions of sputtered TiNiCu and TiNiCuCo are known to be ultra-low fatigue SMAs, able to reversibly undergo the phase transformation for 10+ million cycles without degradation in the mechanical or thermal properties. The primary focus of this thesis was the integration of these sputtered NiTi-based SMA thin-films into the following four novel MEMS devices: 1) TiNiCu for magneoelectric sensors, 2) TiNiHf for bistable actuators, 3) TiNiCuCo for stretchable electronics and 4) thin-film SMA stretchable auxetic structures for wearable and implantable medical devices. The shape memory effect was observed in TiNiCu and TiNiHf films when the

Age of Information (AoI) and delay are crucial performance metrics for Industrial Internet of Things (IIoT) applications not only to perform seamless actuation and control actions but also to enable self-organized and re-configurable manufacturing systems. A challenging task in heterogeneous IIoT networks is to minimize the AoI while maintaining a predefined delay constraint. In this work, we consider a Device-to-Device (D2D)-based heterogeneous IIoT network that supports two types of traffic flows, namely AoI-sensitive flow and delay-sensitive flow. First, we introduce a distributed backlog-aware random access protocol that allows the AoI-sensitive nodes to opportunistically access the channel based on the queue occupancy of the delay-sensitive node. Then, we develop an analytical framework to evaluate the average delay and the average AoI, and formulate an optimization problem to minimize the AoI under a given delay constraint. Finally, we provide numerical results to demonstrate the impact of different network parameters on the performance in terms of the average delay and the average AoI. We also give numerical solutions of the optimal parameters that minimize the AoI subject to a defined delay constraint., Forskningsprofilen NIIT

The World Health Organization declared Alzheimer's disease and its care a global public health priority in 2021 due to its complexity and development, which affects the patient and their caregiver. Alzheimer's symptoms worsen daily, so the patient must have 24/7 care; between responsibilities, the caregiver must deal with arduous tasks, from bathing the patient to managing the behavioral symptoms. By carrying out a systematic mapping, it was possible to identify that, despite the profuse information about Alzheimer's and its care, there is no concise source of information that allows the development of integrated systems that support the care of patients with Alzheimer's. This paper is presented OntoCaimer, which is an ontology that synthesizes the recommendations and preventive actions for most of the symptoms of the different stages of Alzheimer's. OntoCaimer integrates concepts related to sensors, actuators, and measurement, making it possible to use it as a basis for the development of systems that support patient care digitally through alerts or with the use of actuators to support patient care. OntoCaimer allows automating a group of variables associated with recommendations or preventive actions such as weight, environment, and feeding schedules, among others, which would support patient care, reduce caregiver tasks, and serve as a knowledge base for the scientific community and the development of systems that implement electronic systems or simulations before their implementation., La Organización Mundial de la Salud declaró en el 2021 al Alzheimer y su cuidado como prioridad de salud pública a nivel mundial debido a su complejidad y desarrollo, que afecta al paciente y su cuidador. Los síntomas del Alzheimer empeoran día a día, por lo que el paciente debe tener un cuidado 24/7; entre las responsabilidades, el cuidador debe lidiar con arduas tareas, desde bañar al paciente hasta manejar sus síntomas comportamentales. A pesar de la profusa información acerca del Alzheimer y su cuidado, no se cuenta con una fuente concisa de información que permita desarrollar sistemas integrados que soporten el cuidado de pacientes con Alzheimer. En este artículo se presenta OntoCaimer, una ontología que sintetiza las recomendaciones y acciones preventivas para la gran mayoría de los síntomas de las diferentes etapas del Alzheimer, asimismo, OntoCaimer integra conceptos relacionados con sensores, actuadores y medición, haciendo posible su uso como base para el desarrollo de sistemas que apoyen el cuidado de los pacientes, de manera digital –a través de alertas–, o con el uso de actuadores, todo con el fin de dar soporte al cuidado de los pacientes. OntoCaimer permite automatizar un grupo de variables asociadas a las recomendaciones o acciones preventivas como el: peso, ambiente, horarios de alimentación, entre otros, lo que permitiría apoyar el cuidado del paciente, disminuir las tareas del cuidador y servir como base de conocimiento para la comunidad científica y el desarrollo de sistemas que implementen sistemas electrónicos o simulaciones antes de su implementación.

This paper proposes a method to precisely estimate the load force of magnetic lead screw (MLS)-based series elastic actuators (SEAs) in real time. The elastic transmissions of MLS-based SEAs generally comprise permanent magnets (PMs). Owing to the magnetic pole distortion and the characteristic nonlinear force of PMs, conventional force estimation methods are less accurate for MLS-based actuators than for SEAs with mechanical springs. In the proposed method, to precisely estimate force of MLSs, the nonlinear force characteristic of an MLS is modeled with a sinusoidal force model, and the magnetic force hysteresis phenomenon is predicted based on Bouc–Wen-type hysteresis equations. Moreover, a method called the relative displacement normalization method is proposed to detect the magnetic pole distortion and to compensate for the related force estimation error. In addition, the proposed method is applied to a rotary-linear (RotLin) actuator, which is a novel MLS-based linear SEA. The force estimation accuracy is experimentally evaluated by comparison with existing methods. The results demonstrate that the root-mean-square error of the proposed method is less than that of the existing polynomial model by up to 81.2%. Finally, a force controller and a static force control system is designed with the proposed model to prove its feasibility.

Soft robotic manipulators are on the verge to their first real applications. In most cases they are actuated by fluidic pressure or tendons and molded of highly elastic material, which performs large deformation if put under stress. Performing tasks e.g. in inspection of narrow machines or endoscopy requires the actuator to be tactile and controllable. Due to their highly nonlinear behavior, model-based approaches are investigated to combine and utilize sensor information to estimate the system states of the manipulator. In this paper, equations of motion (EoM) for the well-known piecewise constant curvature (PCC) approach are extended by a floating base as it is often used in kinematic chains for legged robots and their contact with the ground. Base reaction forces and moments, which are easily measurable quantities, become visible in the EoM, if the six spatial degrees of freedom at the base of the manipulator are considered. Thereby, additional information on the system's states is obtained and used in the proposed identification scheme. Essentially, the floating base, a center-of-gravity approach and a state-of-the-art parametrization of the PCC kinematics are combined to derive and validate a Lagrangian dynamics model. On a best-case set of validation step responses, the identified inverse dynamics model performs with an accuracy of 5% to 7.6% of max. actuation torque.© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

In this paper, we present a methodology for actuator and sensor fault estimation in nonlinear systems. The method consists of augmenting the system dynamics with an approximated ultra-local model (a finite chain of integrators) for the fault vector and constructing a Nonlinear Unknown Input Observer (NUIO) for the augmented dynamics. Then, fault reconstruction is reformulated as a robust state estimation problem in the augmented state (true state plus fault-related state). We provide sufficient conditions that guarantee the existence of the observer and stability of the estimation error dynamics (asymptotic stability of the origin in the absence of faults and ISS guarantees in the faulty case). Then, we cast the synthesis of observer gains as a semidefinite program where we minimize the ℒ 2 -gain from the model mismatch induced by the approximated fault model to the fault estimation error. Finally, simulations are given to illustrate the performance of the proposed methodology., Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Team Peyman Mohajerin Esfahani

Passive and active exoskeletons have been used over recent decades. However, regarding many physiological systems, we see that the majority explore both active and passive elements to minimize energy consumption while retaining proper motion control. In light of this, we propose a design that combines compliant mechanisms as passive support for gravity balancing of the hand's weight and soft actuators as active support for wrist flexion-extension. Our approach offers a safe, lightweight solution that intrinsically complements and supports the wrist's degrees of freedom. We hypothesize that the proposed soft wearable device is able to increase the range of motion and reduce muscle fatigue while being energy-conservative by balancing of the passive and active subsystems. In this work, we perform a design feasibility study for such soft wrist exoskeletons, particularly focused on wrist flexion-extension rehabilitation. Through optimization, geometries for the required functionality of the compliant beam and soft actuator are obtained, and their performance as separate subsystems is evaluated by simulations and experiments. Under the appropriate inputs, we show that the system can introduce a controllable bifurcation. Through experiments, we investigate such bi-stability and explore its usefulness for rehabilitative support of wrist flexion-extension. In short, the proposed wearable can offer a viable, energy-efficient alternative to traditional rehabilitation technologies., Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Mechatronic Systems Design

Biomimetic actuators are promising candidates for smart soft robotics. The applications of state-of-the-art actuators require the combination of programmable stimuli-responsiveness, excellent robustness, and efficient self-healing ability in a wide-range of working conditions. However, these properties may be mutually exclusive. Inspired by biological tissues, two kinds of polyelectrolytes including polyvinyl alcohol (PVA) and polystyrene sulfonate (PSS) are exploited as the fillers of cellulose nanofibrils (CNFs) for the fabrication of the CNF/PVA/PSS (CAS) film via the assembly of the physically-crosslinked network through multiple H-bonding and electrostatic interactions. Achieved by a casting-evaporation strategy, internal stress is stored within the polymer matrix and transforms into reversible anisotropic bending deformations in response to a humidity gradient. The speed, direction, and pitch of the bending can be programmed by tailoring the internal stresses and geometry of the samples. Moreover, the H-bonded network also contributes to the effective energy dissipation toward high toughness during tensile stretching, as well as self-healing ability during moisture saturation of the CAS films. This enables the fabrication of a humidity-sensitive flower-shaped actuator and self-healable packaging paper. This study presents a biomimetic strategy for the fabrication of multi-functional soft robotics, which holds great promise for applications in the fields of biosensors and smart packaging., QC 20230602

In this paper, we consider identification and control for potentially unstable linear systems with multi-agent controllers in the presence of wireless interference channels among the remote controllers and the actuators. We formulate the optimal control problem as a stochastic game and utilize the stochastic approximation technique to learn the optimal control solutions and the plant dynamics simultaneously in an online manner. Using Lyapunov drift analysis, we show that the identified plant dynamics and the learned control solutions via the proposed algorithm can converge to the true plant dynamics and optimal control solutions, respectively. Furthermore, we also rigorously show the convergence speed of the proposed learning algorithm in terms of the online learning step sizes in the proposed algorithm. The proposed scheme is also compared with various state-of-art baselines and we show that significant performance gains can be achieved. IEEE

This thesis provides an study of the flow around a McDonnell Douglas 30P30N with an Active Flow Control device, a synthetic jet, with different configurations. The flow is two dimensional, with a Reynolds number of 1.7·10⁶ , an Angle of Attack of 5.5⁰ and a Mach of 0.7. The purpose of this device is to reduce the drag and increases the lift by reducing the vortex shedding at the wake by retarding the boundary layer detachment. Several Reynold Averaged Navier-Stokes simulations have been performed to determine the configuration where the maximum aerodynamic efficiency is reach. It has been concluded that the actuation is highly dependant on the position of the actuator; placed after the suction region has been two time more efficient than placed on it. In addition to this, it has been observed that the efficiency increased with the momentum coefficient, the nondimensional frequency and the angle of the exhaust velocity. All of them have played a major role on the actuation.

To achieve high motion accuracy and repeatability for a variable reluctance tunable magnet actuator that uses linear controllers, this article proposes a novel actuator design that has a linearized force-flux relation. Prior designed variable reluctance tunable magnet actuators use a C-shaped actuator that has a quadratic relation between the force and the flux. By using lumped parameter models, an Hybrid Tunable Magnet Actuator design based on biased fluxes is developed. The linear behaviour of this design is proven by a finite element analysis. The force-flux relation is piecewise linear for different positions depending on the direction of the flux. Within a position range of ± 500 µm and a force range of ± 20 N, the error of a linear fit is in the order of 0.08 N. With an experimental setup the linear relation is also proven with an error of 0.03 N. Comparing the designed tunable magnet actuator with an hybrid reluctance actuator shows that the tunable magnet actuator is more efficient for quasi-static forces that are constant for time periods longer than 1.4 s., Mechanical Engineering | Mechatronic System Design (MSD)

This paper proposes a method to precisely estimate the load force of magnetic lead screw (MLS)-based series elastic actuators (SEAs) in real time. The elastic transmissions of MLS-based SEAs generally comprise permanent magnets (PMs). Owing to the magnetic pole distortion and the characteristic nonlinear force of PMs, conventional force estimation methods are less accurate for MLS-based actuators than for SEAs with mechanical springs. In the proposed method, to precisely estimate force of MLSs, the nonlinear force characteristic of an MLS is modeled with a sinusoidal force model, and the magnetic force hysteresis phenomenon is predicted based on Bouc–Wen-type hysteresis equations. Moreover, a method called the relative displacement normalization method is proposed to detect the magnetic pole distortion and to compensate for the related force estimation error. In addition, the proposed method is applied to a rotary-linear (RotLin) actuator, which is a novel MLS-based linear SEA. The force estimation accuracy is experimentally evaluated by comparison with existing methods. The results demonstrate that the root-mean-square error of the proposed method is less than that of the existing polynomial model by up to 81.2%. Finally, a force controller and a static force control system is designed with the proposed model to prove its feasibility.

The parallel connection of DC-DC converters requires the development of an appropriate control strategy that regulates load voltage and shares current amongst participating converters. This paper proposes a resilient and robust cooperative distributed control approach that simultaneously ensures voltage regulation and balanced current sharing in parallel DC-DC converters in the presence of false data injection attacks on control input channels. Based on analytical tools from network control and Lyapunov stability theory, concise stability certificates are derived. The proposed cooperative distributed control strategy guarantees resilience against unknown bounded attacks on the actuators of DC-DC converters and the robustness to uncertainties in load parameters and the physical parameters of converters. Furthermore, the control design for each converter does not require any knowledge about the number of participating converters. The detailed simulation and experimental results verify the satisfactory performance of the proposed method in voltage regulation and balanced current sharing in parallel converters, as well as resilience to bounded false data injection attacks.

In this paper, we present dynamic systems over encrypted data that compute the next state and the output using homomorphic properties of the cryptosystem, which has equivalent performance to the linear dynamic controllers over real-valued signals. Assuming that the input as well as the output of the plant is encrypted and transmitted to the system, the state matrix of the system is designed to consist of integers. This allows the proposed dynamic system to operate for infinite time horizon, without decryption or reset of the state. For implementation in practice, the use of cryptosystems based on Learning With Errors problem is considered, which allows both multiplication and addition over encrypted data. The effect of injecting errors during encryption is in turn controlled under closed-loop stability., QC 20221005

Interactive applications with automated feedback will largely influence the design of future networked infrastructures. In such applications, status information about an environment of interest is captured and forwarded to a compute node, which analyzes the information and generates a feedback message. Timely processing and forwarding must ensure the feedback information to be still applicable; thus, the quality-of-service parameter for such applications is the end-to-end latency over the entire loop. By modelling the communication of a feedback loop as a two-hop network, we address the problem of allocating network resources in order to minimize the delay violation probability (DVP), i.e. the probability of the end-to-end latency exceeding a target value. We investigate the influence of the network queue states along the network path on the performance of semi-static and dynamic scheduling policies. The former determine the schedule prior to the transmission of the packet, while the latter benefit from feedback on the queue states as time evolves and reallocate time slots depending on the queue's evolution. The performance of the proposed policies is evaluated for variations in several system parameters and comparison baselines. Results show that the proposed semi-static policy achieves close-to-optimal DVP and the dynamic policy outperforms the state-of-the-art algorithms., QC 20220607

Assistive technology (AT) supports individuals who experience difficulties in carrying out daily life physical activities, for example, people with disabilities, the elderly, and people with chronic diseases, such as diabetes, bone and joint disorders, heart disease, or stroke. Thanks to assistive technologies, these patients can regain their independence by using permissive devices to carry out physical activities without human assistance, and in ways that mirror healthy individuals. Hence, ATs support the autonomy of people who have been physically limited or have cognitive dysfunction. AT is also known as access technology, including mechanical, optical, electronic, and computer solutions to benefit people with sensory or motor impairments, thus allowing them to perform routine tasks that were previously impossible to execute. This chapter presents a prosthesis that has been designed for people with locomotor disabilities and deficiencies. The device is low cost, has low energy consumption, and is easy to use by a person with a hand disability. The subsequent developing stage will consist of transitioning from a traditional prosthesis to a neuroprosthesis, by using sensor networks and controlling the device (bionic prosthesis) through smart sensors and actuators, with control systems having microcontroller unit (MCU), brain-computer interface, and NextMind interfaces.

Liquid Crystal Elastomers (LCEs) are an exciting category of material that has tremendous application potential across a variety of fields, owing to their unique properties that enable both sensing and actuation. To some, LCEs are simply another type of Shape Memory Polymer, while to others they are an interesting on-going scientific experiment. In this visionary article, we bring an interdisciplinary discussion around creative and impactful ways that LCEs can be applied in the Built Environment to support kinematic and kinetic buildings and situational awareness. We focus particularly on the autonomy made possible by using LCEs, potentially removing needs for motors, wiring and tubing, and even enabling fully independent operation in response to natural environment variations, requiring no power sources. To illustrate the potential, we propose a number of concrete application scenarios where LCEs could offer innovative solutions to problems of great societal importance, such as autonomous active ventilation, heliotropic solar panel systems which can also remove snow or sand autonomously, and invisible coatings with strain mapping functionality, alerting residents in case of dangerous (static or dynamic) loads on roofs or windows, as well as assisting building safety inspection teams after earthquakes.

Liquid Crystal Elastomers (LCEs) are an exciting category of material that has tremendous application potential across a variety of fields, owing to their unique properties that enable both sensing and actuation. To some, LCEs are simply another type of Shape Memory Polymer, while to others they are an interesting on-going scientific experiment. In this visionary article, we bring an interdisciplinary discussion around creative and impactful ways that LCEs can be applied in the Built Environment to support kinematic and kinetic buildings and situational awareness. We focus particularly on the autonomy made possible by using LCEs, potentially removing needs for motors, wiring and tubing, and even enabling fully independent operation in response to natural environment variations, requiring no power sources. To illustrate the potential, we propose a number of concrete application scenarios where LCEs could offer innovative solutions to problems of great societal importance, such as autonomous active ventilation, heliotropic solar panel systems which can also remove snow or sand autonomously, and invisible coatings with strain mapping functionality, alerting residents in case of dangerous (static or dynamic) loads on roofs or windows, as well as assisting building safety inspection teams after earthquakes.

Liquid Crystal Elastomers (LCEs) are an exciting category of material that has tremendous application potential across a variety of fields, owing to their unique properties that enable both sensing and actuation. To some, LCEs are simply another type of Shape Memory Polymer, while to others they are an interesting on-going scientific experiment. In this visionary article, we bring an interdisciplinary discussion around creative and impactful ways that LCEs can be applied in the Built Environment to support kinematic and kinetic buildings and situational awareness. We focus particularly on the autonomy made possible by using LCEs, potentially removing needs for motors, wiring and tubing, and even enabling fully independent operation in response to natural environment variations, requiring no power sources. To illustrate the potential, we propose a number of concrete application scenarios where LCEs could offer innovative solutions to problems of great societal importance, such as autonomous active ventilation, heliotropic solar panel systems which can also remove snow or sand autonomously, and invisible coatings with strain mapping functionality, alerting residents in case of dangerous (static or dynamic) loads on roofs or windows, as well as assisting building safety inspection teams after earthquakes.

A longstanding goal in engineering research has been to realize haptic displays for virtual reality that allow their users to touch and manipulate virtual objects which feel realistic. Despite decades of research, this goal remains far from being achieved. Motivated by the challenges involved, this PhD contributes new research findings on perceptual and physical mechanisms of human touch perception, and applies this knowledge for the engineering of efficient haptic technologies for virtual and augmented reality. The first part of the PhD is motivated by the active nature of haptic perception. During haptic exploration of objects, proprioceptive information about movements of the hands and fingers is integrated with tactile sensory information elicited via touch contact in order to facilitate perceptual judgements about object properties or events. Surprisingly little is known about human abilities to spatially localize the fingers via proprioception. The first part of the dissertation presents findings from perceptual investigations using a novel virtual reality paradigm. The results reveal that errors in spatial localization of the fingers are surprisingly large, averaging several centimeters per finger, but are strongly refined by even partial visual cues about the positions of adjacent fingers. The results also provide critical information that is needed in order to specify performance requirements for virtual reality technologies, including hand tracking systems.The next part of this PhD addresses another key aspect in engineering haptic interactions: that of furnishing touch sensations to the skin. A central challenge in haptic engineering is that the skin is an extended sensory medium with high spatial resolution. While many prior haptic devices have been designed to use numerous actuators, such devices are too bulky, costly, and complex for practical application. This PhD proposes a new design strategy that exploits the physics of waves in the skin. First, fi

Liquid Crystal Elastomers (LCEs) are an exciting category of material that has tremendous application potential across a variety of fields, owing to their unique properties that enable both sensing and actuation. To some, LCEs are simply another type of Shape Memory Polymer, while to others they are an interesting on-going scientific experiment. In this visionary article, we bring an interdisciplinary discussion around creative and impactful ways that LCEs can be applied in the Built Environment to support kinematic and kinetic buildings and situational awareness. We focus particularly on the autonomy made possible by using LCEs, potentially removing needs for motors, wiring and tubing, and even enabling fully independent operation in response to natural environment variations, requiring no power sources. To illustrate the potential, we propose a number of concrete application scenarios where LCEs could offer innovative solutions to problems of great societal importance, such as autonomous active ventilation, heliotropic solar panel systems which can also remove snow or sand autonomously, and invisible coatings with strain mapping functionality, alerting residents in case of dangerous (static or dynamic) loads on roofs or windows, as well as assisting building safety inspection teams after earthquakes.

This thesis presents the development a sliding mode controller and vehicle allocation to control a surface vessel platform within a high degree of accuracy. This is part of ongoing development on the WAMV platform at Florida Atlantic University to improve autonomy in marine systems. By developing models for the untested thrusters currently used, the efficacy of a Sliding Mode Controller is evaluated, and a new control allocation developed based on the gradient descent optimization method is developed to manage the thrusters’ constrained angles of thrust generation. The official simulation for the WAMV platform was then modified to include these aspects and the system was tested under wind conditions and was successful in achieving control to waypoints. The gradient descent optimization used for the control allocation did manage to increase the accuracy of both heading and position of the system at convergence. The sliding mode controller navigated to the desired waypoint however maintained oscillations of cross track that were less then 2m and heading error less 20 degrees., 2022, Includes bibliography., Degree granted: Thesis (MS)--Florida Atlantic University, 2022., Collection: FAU Electronic Theses and Dissertations Collection

With the rapid development of mobile computing, mission-critical internet-of-things (IoT) systems have become popular. Typical mission-critical IoT systems may contain complicated unknown and unstable elements and it is of particular importance to identify and stabilize them as unstable systems may experience catastrophic consequences. We consider the identification and optimal control for a mission-critical IoT system over multiple-input multiple-output (MIMO) fading channels. First, we focus on the optimal control of the mission-critical IoT system, assuming that the system dynamics are known, and propose a novel stochastic-approximation-based algorithm to learn the optimal control solution for the IoT controller in an online manner. Second, we extend the optimal control framework to deal with the unknown mission-critical IoT system and propose a novel normalized-stochastic-gradient-descent-based algorithm to simultaneously identify and control the system in an online manner. Using Lyapunov stability analysis, we theoretically show the asymptotic optimality of the proposed learning algorithms. Numerical results are analyzed for our proposed scheme and for several state-of-the-art learning schemes in terms of the computational complexity, the convergence and the stability performance. Specifically, the proposed scheme can be implemented more than 50% faster than the state-of-the-art learning schemes. Moreover, the system identification performance of the proposed scheme can achieve a normalized system identification mean square error (MSE) of around 0.01 in 100 iterations. This is a substantial improvement compared to the baseline algorithms, where the normalized system identification MSE diverges.

We consider the optimal control of linear systems over wireless multiple-input multiple-output (MIMO) fading channels, where the wireless MIMO fading and random access of the remote controller may cause intermittent controllability or uncontrollability of the closed-loop control system. We consider the finite time horizon optimal control first and then check the conditions for the existence and uniqueness of optimal control for the infinite time horizon case. Specifically, for the finite time horizon case, we show that the optimal control gain matrix can be computed offline based on the distribution of the wireless MIMO fading and random access of the controller. For the infinite time horizon case, we show that, when the closed-loop system is almost surely controllable, the optimal control solution always exists and is unique. In the case that MIMO fading channels and the random access of the remote controller destroy the closed-loop controllability, we propose a novel controllable and uncontrollable positive semidefinite (PSD) cone decomposition induced by the singular value decomposition (SVD) of the MIMO fading channel contaminated control input matrix. This enables a closed-form characterization of the sufficient condition for both the existence and the uniqueness of the optimal control solution. The closed-form sufficient condition reveals the fact that the optimal control action may still exist even if the closed-loop system suffers from intermittent controllability or almost sure uncontrollability. We further propose a novel stochastic approximation (SA)-based online learning algorithm that can learn the optimal control action on the fly based on the plant state observations. We finally extend the technical results to the case in which the channel state information (CSI) is unavailable at the controller. We show that the sufficient condition for the existence and uniqueness of the optimal control solution is more difficult to satisfy due to the penalty caused

We consider the problem of sensor and actuator (SaA) placement to minimize an infinite-horizon LQG cost for a discrete-time Gauss-Markov system. Due to financial, topology and bandwidth limitations, only a subset of SaAs can be selected for placement. Different from existing literature, which successively iterates partial selection to reach a suboptimal solution, this paper focuses on a joint placement and encounters fundamental difficulty in the sense that joint SaA placement introduces a term in the LQG cost that is difficult to be convexified. A branch-and-bound algorithm is introduced to search for solutions to an approximate problem obtained by relaxing the Boolean constraints. By deriving a compact search space where any optimal solution belongs to or resides, we derive lower and upper bounds to the optimal solution in each subregion of the search space, and subsequently refine the search space. A suboptimal solution to the original problem is obtained from integer rounding and the optimality gap is further analyzed. Numerical examples are provided to illustrate the effectiveness of the proposed algorithm. This algorithm has significant reduction of iteration numbers compared with the brute-force enumeration especially when the number of states is not large but the number of placement choices is large. In addition, an improvement of LQG cost is obtained compared with the successively iterating partial selection methods, a canonical algorithm for SaA placement in the literature. IEEE

Suspended piezoelectric thin films are key elements enabling high-frequency filtering in telecommunication devices. To meet the requirements of next-generation electronics, it is essential to reduce device thickness for reaching higher resonance frequencies. Here, the high-quality mechanical and electrical properties of graphene electrodes are combined with the strong piezoelectric performance of the free-standing complex oxide, BaTiO3 (BTO), to create ultrathin piezoelectric resonators. It is demonstrated that the device can be brought into mechanical resonance by piezoelectric actuation. By sweeping the DC bias voltage on the top graphene electrode, the BTO membrane is switched between the two poled ferroelectric states. Remarkably, ferroelectric hysteresis is also observed in the resonance frequency, magnitude and Q-factor of the first membrane mode. In the bulk acoustic mode, the device vibrates at 233 GHz. This work demonstrates the potential of combining van der Waals materials with complex oxides for next-generation electronics, which not only opens up opportunities for increasing filter frequencies, but also enables reconfiguration by poling, via ferroelectric memory effect., QN/Steeneken Lab, ImPhys/Practicum support, QN/van der Zant Lab, QN/Steele Lab, QN/Groeblacher Lab, QN/Caviglia Lab, Dynamics of Micro and Nano Systems, QRD/Wimmer Group

After decades of research and development, haptic feedback is increasingly appearing in consumer products. While the prevalence of haptic feedback is increasing, the integration rarely offers increased fidelity to previous generations. We argue this is because of the tremendous complexity of successful haptic design engineering, but critically, also because of information saturation. With novel cutaneous feedback technologies and companies emerging almost daily, the multi-disciplinary nature of haptics and the marketing-driven terminology used to stand out in a crowded market makes it challenging to select and integrate actuators correctly. To manage this complexity and facilitate the interdisciplinary exchange of user requirements and material affordances, we introduce a novel classification criterion for haptic actuators focused on the bandwidth and fidelity of potential effects. We introduce vocabulary for describing the precise experience the actuators and corresponding systems should deliver. Lastly, we summarize currently commercially available cutaneous-based haptic technology. In the nearby future, the same criterion and language can also prove valuable for steering technology development of new and improved actuators and enabling novice and experienced practitioners to understand and integrate cutaneous feedback in their products., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Materials and Manufacturing

In contrast with most existing results concerning unmanned aerial vehicles (UAVs) wherein material points or only attitude/longitudinal dynamics are considered, this article proposes a distributed fixed-time fault-tolerant control methodology for networked fixed-wing UAVs whose dynamics are six-degree-of-freedom with twelf-state-variables subject to actuator faults and full-state constraints. More precisely, state transformations with the scaling function are devised to keep the involved velocity and attitude within their corresponding constraints. The fixed-time property is obtained in the sense of guaranteeing that the settling time is lower bounded by a positive constant, which is independent of initial states. The actuator faults as well as the network induced errors are handled via the bound estimation approach and well-defined smooth functions. By strict Lyapunov arguments, all closed-loop signals are proved to be semiglobally uniformly ultimately bounded, and the tracking errors of velocity and attitude converge to the residual sets around origin within a fixed time., Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Team Bart De Schutter

Knowledge on joint impedance during walking in various conditions is relevant for clinical decision-making and the development of robotic gait trainers, leg prostheses, leg orthotics and wearable exoskeletons. Whereas ankle impedance during walking has been experimentally assessed, knee and hip joint impedance during walking have not been identified yet. Here we developed and evaluated a lower limb perturbator to identify hip, knee and ankle joint impedance during treadmill walking. The lower limb perturbator (LOPER) consists of an actuator connected to the thigh via rods. The LOPER allows to apply force perturbations to a free-hanging leg, while standing on the contralateral leg, with a bandwidth of up to 39 Hz. While walking in minimal impedance mode, the interaction forces between LOPER and the thigh were low (<5N) and the effect on the walking pattern was smaller than the within-subject variability during normal walking. Using a non-linear multibody dynamical model of swing leg dynamics, the hip, knee and ankle joint impedance were estimated at three time points during the swing phase for nine subjects walking at a speed of 0.5 m/s. The identified model was well able to predict the experimental responses for the hip and knee, since the mean variance accounted (VAF) for was 99% and 96%, respectively. The ankle lacked a consistent response and the mean VAF of the model fit was only 77%, and therefore the estimated ankle impedance was not reliable. The averaged across-subjects stiffness varied between the three time points within 34-66 and 0-3.5 Nm/rad Nm/rad for the hip and knee joint respectively. The damping varied between 1.9-4.6 and 0.02-0.14 Nms/rad Nms/rad for hip and knee respectively. The developed LOPER has a negligible effect on the unperturbed walking pattern and allows to identify hip and knee impedance during the swing phase., Biomechatronics & Human-Machine Control

This article proposes a fuzzy adaptive design solving the finite-time constrained tracking for hypersonic flight vehicles (HFVs). Actuator dynamics and asymmetric time-varying constraints are considered when solving this problem. The main features of the proposed design lie in 1) introducing a novel piecewise but differentiable switching control law, with an appropriate design thought to avoid the singularity issues typical of finite-time control; 2) handling actuator magnitude, bandwidth, and rate constraints, thanks to the introduction of an auxiliary compensating system counteracting the adverse effects caused by actuator physical constraints, while guaranteeing the closed-loop stability; and 3) handling asymmetric time-varying state constraints, thanks to the introduction of tan-type barrier Lyapunov functions working for both constrained and unconstrained scenarios. Comparative simulation results illustrate the effectiveness of the proposed strategy over existing methods for HFVs in terms of convergence, smoothness, actuator performance, and constraints satisfaction., Team DeSchutter, Robot Dynamics

We proposed network-decentralized control strategies, in which each actuator can exclusively rely on local information, without knowing the network topology and the external input, ensuring that the flow asymptotically converges to the optimal one with respect to the p -norm. For 1 < p < ∞ , the flow converges to a unique constant optimal up∗. We show that the state converges to the optimal Lagrange multiplier of the optimization problem. Then, we consider networks where the flows are affected by unknown spontaneous dynamics and the buffers need to be driven exactly to a desired set-point. We propose a network-decentralized proportional-integral controller that achieves this goal along with asymptotic flow optimality; now it is the integral variable that converges to the optimal Lagrange multiplier. The extreme cases p=1 and p=∞ are of some interest since the former encourages sparsity of the solution while the latter promotes fairness. Unfortunately, for p=1 or p=∞ these strategies become discontinuous and lead to chattering of the flow, hence no optimality is achieved. We then show how to approximately achieve the goal as the limit for p 1 or p ∞., Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Team Tamas Keviczky