Discrete Laguerre MPC-based Visual Servoing for 5-DOF Manipulators with Visual Feedback Loss Compensation: Design and Experimental Demonstration

Magnetic micro-robots are small robots under 1mm in size, made of magnetic materials, with relatively simple structures and functionalities. Such micro-robots can be actuated and controlled remotely by externally applied magnetic fields, and hence have the potential to access small and enclosed spaces. Most of the existing magnetic micro-robots can operate in wet environments. When the robots are actuated by the applied magnetic field to move inside a viscous liquid, they invoke flow motions around them inside the liquid. The induced flows are relatively local as the velocity of these flows decays rapidly with the distance from a moving robot, and the flow patterns are highly correlated with the motions of the micro-robots which are controllable by the applied magnetic field. Therefore, it is possible to generate local flow patterns that cannot be easily done using other microfluidic techniques. In this work we propose to use rotational motion of the magnetic micro-robots for local manipulation of flows. We employ electromagnetic techniques to successfully deliver actuation and motion control onto the micro-robots. Rotational magnetic field is applied to induce rotational motion of micro-robots both when they stay near a surface and are suspended in the liquid. Rotational flows are locally generated in the vicinity of micro-robots inside the viscous liquid. Implementation of three major applications using the flows generated by the rotating micro-robots are demonstrated in this work: 1) Two-dimensional (2D) non-contact manipulation of micro-objects. 2) Three-dimensional (3D) propulsion for the micro-robot to swim in a liquid. 3) Size-based sorting of micro-particles in microfluidic channels under continuous flow. The first two applications occur in otherwise quiescent liquid, while the third requires the presence of non-zero background flow. For the first application, we propose two methods to achieve precise positioning of the microrobots on a surface: 1) Using visual-feedback-control to adjust the rotation for one single microrobot. Micro-robot can be precisely positioned at any location on a surface using this method. 2) Using a specially prepared surface with magnetic micro-docks embedded in it, which act as local magnetic traps for multiple micro-robots to hold their positions and operate in parallel. Physical models are established for both the micro-robot and the micro-objects present in the induced rotational flow. The rotational flows induced by rotating micro-robots are studied with numerical simulations. Experimental demonstrations are first given at sub-millimeter scale to verify the proposed method. Micro-manipulation of polymer beads is performed with both positioncontrol methods. Automated micro-manipulation is also achieved using visual-feedback. Micromanipulation at micron-scale is then performed to demonstrate the scalability and versatility of the proposed method. Non-contact manipulation is achieved for various micro-objects, including biological samples, using a single spherical micro-robot. Inspired by flagellated microorganisms in nature, we explore the hydrodynamics of an elastic rod-like structure - the artificial flagellum, and verify by both simulation and experiments that rotation and deformation of such structure can result in a propulsive force on a micro-robot it is attached to. Optimization of flagellum geometry is achieved for a single flagellum. A swimming micro-robot design with multiple flexible flagella is proposed and fabricated via an inexpensive micro-fabrication process involving photolithography, micro-molding and manual assembly. Experiments are perform to characterize the propulsive force generation and the resulting swimming performance of the fabricated micro-robots. It is demonstrated that the swimming speed can be improved by increasing the number of attached flagella. For the size-based sorting application, we integrate the micro-robots into microfluidic channels by using the substrate embedded with magnetic micro-docks, which are capable of holding the robots under continuous flow inside the channels while the robots spin. Numerical analysis is carried out of the flows inside the microfluidic channel in the presence of rotating micro-robots, and a physical model is established and discussed for size-based lateral migration of spherical micro-objects inside the induced rotational flows. Experimental demonstrations are performed for using the induced rotational flows to divert the trajectories of micro-particles based on their sizes under continuous flow. In addition, we propose the method of using the two photon polymerization (TPP) technique to fabricate magnetic micro-robots with complex shapes. The method could also achieve fabrication of arrays of micro-robots for more sophisticated applications. However, experimental results prove that the TPP is insufficient to achieve magnetic micro-robots that meet our needs for size-based sorting application due to physical limitations of the materials. Despite that, it is potentially powerful and suitable for fabrication of micro-robots with complex structures at small scales.

IDF21-0237 The Impact of the Current Accessibility of Insulin Pumps on the Lives of the Visually Impaired in Canada

A reduction of more than 20 dB of the intensity noise at the antiphase relaxation oscillation frequency is experimentally demonstrated in a two-polarization dual-frequency solid-state laser without any optical or electronic feedback loop. Such behavior is inherently obtained by aligning the two orthogonally polarized oscillating modes with the crystallographic axes of a (100)-cut neodymium-doped yttrium aluminum garnet active medium. The antiphase noise level is shown to increase as soon as one departs from this peculiar configuration, evidencing the predominant role of the nonlinear coupling constant. This experimental demonstration opens new perspectives on the design and realization of extremely low-noise dual-frequency solid-state lasers.

Mid-infrared precision spectroscopy has important applications in the fields of trace gas detection and the determination of fundamental physical constants. However, due to the limited commercialization of related technologies, there is a lack of narrow linewidth laser sources or linewidth narrowing approaches in the mid-infrared region, as well as stable mid-infrared frequency standards. The most commercialized and widely used mid-infrared laser source is the quantum cascade laser (QCL). But its free-running linewidth is more than MHz scale due to the influence of laser drive current noise and temperature fluctuation. This impedes the development of precision spectroscopy in this region. In this work, we introduce a technique for generating a narrow linewidth, stable mid-infrared laser by using optical feedback frequency locking, with a high-finesse mid-infrared ultrastable Fabry-Pérot cavity as the frequency reference. The optical cavity consists of two high reflectivity mirrors separated by ultra-low expansion (ULE) material with a low temperature expansion coefficient, and its temperature is precisely controlled. And the cavity is also surrounded in a vaccum cavity made of stainless steel. All these measures ensure the cavity length and its longitudinal mode stability. By using optical feecback, a QCL is locked to the cavity, which stabilizes the laser frequency and narrows the laser linewidth. In order to improve the long-term stability of the optical feedback, an active servo is leveraged to control the feedback phase. The error signal for the servo is obtained by using the method similar to the Pound-Derver-Hall locking. In this work, we first theoretically analyze the feasibility of laser to F-P cavity frequency locking by optical feedback. We propose the laser frequency response model with a linear F-P cavity under optical feedback, and analyze the influence of the direct cavity reflection on the laser frequency. Then the experimental demonstration is conducted. Firstly, we measure the reflectivity of the cavity mirror by using cavity ring-down spectroscopy, resulting in a cavity finesse of 30200 and a cavity mode linewidth of 49.7 kHz. After that, we successfully achieve optical feedback frequency locking, and consecutive cavity transmission is observed. The error signal for the control of the optical feedback phase is used to evaluate the locking performance by converting it into the laser frequency noise. By analyzing the noise spectral density, the QCL linewidth is narrowed to 0.3 Hz on a short timescale (< 10 ms). And the long-term stability is suspected to be dedicated by the temperature variation of the optical cavity, resulting in a laser frequency drift 20 kHz/12 h. The narrow linewidth stabilized mid-infrared laser source obtained with this technique is expected to serve as an effective frequency reference source for mid-infrared precision spectroscopic measurements.

The project presented in this thesis centers around the development of TREYESCAN: Traffic Eye Scanning and Compensation Analyzer. A test designed to quantitatively assess compensatory viewing abilities on a wide screen in individuals with visual field loss, which allows for unrestricted head and eye movements. Establishing vision standards for determining fitness to drive is challenging, considering the negative consequences of driving cessation on mobility, independence, and quality of life. The impact of peripheral visual field loss on driving performance is established, but the precise level of loss incompatible with safe driving remains uncertain, as compensation abilities vary widely between individuals and increased scanning is reported to aid adaptation. Given the relatively weak evidence supporting current vision standards, there is a need to explore whether compensatory eye movements enable individuals with varying levels of visual field loss to effectively perceive their surroundings while driving. The aim is to distinguish between effective and ineffective compensatory scanning in individuals with visual field loss, focusing solely on this skill without measuring additional abilities associated with driving. Therefore, TREYESCAN can offer advantages over static visual field testing, since eye and head movements are permitted for compensation of visual field loss. Chapter 1 provides a general introduction on glaucoma, the primary cause of visual field loss in the elderly population and the leading cause of irreversible blindness worldwide. Primary open-angle glaucoma (POAG) represents a significant public health concern with a global prevalence of 2.4% in the population over 40 years old, impacting 68.56 million individuals in 2021. The chapter discusses the impact on the optic nerve and the visual field, and the importance of timely detection and intervention. The phenomenon of unawareness of visual field loss in glaucoma patients, compensatory eye movements, and the challenges of driving with visual field defects are also explored. Presently, the Esterman visual field test, a suprathreshold binocular test, serves as the standard for assessing the visual field in glaucoma patients undergoing driving evaluations in the Netherlands. In Chapter 2, an analysis of data from the CBR (Dutch driving test organization) is conducted to determine the predictive value of the Esterman visual field test on the outcome of on-road driving tests. Subsequently, the TREYESCAN was developed, with detailed accounts of the developmental stages presented in Chapters 3 and 4. Chapter 3 covers the validation and development of the setup and open-source software of the TREYESCAN. Chapter 4 outlines procedures involved in traffic scene recording, as well as pilot measurements in normally-sighted individuals for the selection of suitable scenes and Areas of Interest (AOIs). Chapter 5 presents the TREYESCAN case-control study results, involving glaucoma patients at various stages of disease progression and control participants. The relationship between visual field loss and compensatory eye movements is explored. Chapter 6 includes a summary of this thesis’ main findings, leading to a subsequent general discussion and conclusion.

Inter-robot transfer of training data is a little explored topic in learning- and vision-based robot control. Here we propose a transfer method from a robot with a lower Degree-of-Freedom (DoF) to one with a higher DoF utilizing the omnidirectional camera image. The virtual rotation of the robot camera enables data augmentation in this transfer learning process. As an experimental demonstration, a vision-based control policy for a 6- DoF robot is trained using a dataset collected by a wheeled ground robot with only three DoFs. Towards the application of robotic manipulations, we also demonstrate a control system of a 6- DoF arm robot using multiple policies with different fields of view to enable object reaching tasks.

We demonstrate numerically and experimentally that low- frequency fluctuations (LFF) in a laser diode subject to delayed optical feedback can be suppressed or stabilized by a second optical feedback with a short delay. The second feedback suppresses LFF by shifting antimodes far away from the external cavity modes in phase space, or by making them disappear, with the consequence that the crises that induce the power dropouts are no longer possible. Moreover, as the second feedback strength increases, the laser undergoes a bifurcation cascade with successive regions where it exhibits chaos or LFF and regions where it locks to a newly-born stable maximum gain mode. This all-optical stabilization technique is easier to implement from an experimental point of view than many existing methods since it does not require modification of any laser parameters or of the first optical feedback.

Composed of multi-section precurved tubes, continuous concentric-tube robot(CTR) has the potential of reaching surgical target during minimally invasive surgeries. Since concentric tubes are made of super-elastic nickel-titanium alloy, they can present different shapes when they extend and rotate with respect to each other. Compared to traditional surgical robots, CTR is superior in small size and flexible bending so that it can work in tiny space and adapt well to non-structural environment with multiple obstacles. In this paper, we proposed a CTR with 38cm in length and 1.85kg in weight which is assembled on a two-freedom platform to enable surgeons to perform various surgeries. Structure design of CTR and an image-guided algorithm are described in detail. For the propose of controlling robot to reach the target more precisely, a single camera is mounted at the tip of concentric tubes which can estimate the mapping between image plane and robotic joint space. This paper presents a model-less method based on Kalman filter to online estimate image Jacobian matrix, therefore robot is capable of capturing the target accurately accompanied by position changes on image plane. Experimental demonstration is also presented in this paper to verify the proposed method.

Purpose:To review the evidence on the impact of visual field loss on skills required for driving.Methods:A literature search was undertaken using a systematic approach. Papers within scope were identified by two independent reviewers, and papers were grouped into similar themes for discussion.Key findings:Evidence suggests that both binocular and monocular visual field defects have a negative impact on driving skills. Both central and peripheral cause difficulties, but the degree of impact is dependent on the defect severity and compensation ability. Many factors that affect compensation to visual field loss and the effects of visual field loss on driving skills are discussed, including cognitive status, age and duration of visual field loss. In summary, in central visual field loss compensation, strategies include reduction of overall driving speed; whereas, in peripheral field loss, increased scanning is reported to aid adaptation.Conclusions:For driving, there is evidence that complete and/or binocular visual field loss poses more of a difficulty than partial and/or monocular loss, and central defects cause more problems than peripheral defects. A lack of evidence exists concerning the impact of superior versus inferior defects. The level of peripheral vision loss that is incompatible with safe driving remains unknown, as compensation abilities vary widely between individuals. This review highlights a lack of evidence in relation to the impact of visual field loss on driving skills. Further research is required to strengthen the evidence to allow clinicians to better support people with visual field loss with driving advice.

In this paper, we experimentally demonstrate message transmission over a commercial optical fiber link modulated by an ultra-wideband (UWB) carrier generated by a chaotic laser diode subject to optical feedback. The laser diode subject to the optical loop feedback is adopted to generate the chaotic UWB carrier. The message, which is generated by a pulse pattern generator, is modulated by the optical intensity modulator. After being transmitted over a 2 km standard single-mode fiber (SSMF), the waveform is recorded by a real-time oscilloscope, in front of which is a photodetector. A message with a bit rate of 2 Gb/s is successfully transmitted over the 2 km SSMF using the chaotic UWB-over-fiber system. In addition, the influences of the amplitude, the bit rate of the message, and the optical power in the SSMF on the transmission quality are separately analyzed in detail. The results presented in this paper are of great importance for UWB communications.

In this contribution we experimentally demonstrate the change and improvement of dynamical properties of a passively mode-locked semiconductor laser subject to optical feedback from two external cavities by coupling the feedback pulses back into the gain segment. Hereby, we tune the full delay-phase of the pulse-to-pulse period of both external cavities separately and demonstrate the change of the repetition rate, timing jitter, multi-pulse formation and side-band suppression for the first time for such a dual feedback configuration. In addition, we thereby confirm modeling predictions by achieving both a good qualitative and quantitative agreement of experimental and simulated results. Our findings suggest a path towards the realization of side-band free all-optical photonic oscillators based on mode-locked lasers.

In this paper, the timing jitter induced by the fiber dispersion in photonic A/D converters using time-wavelength interweaved sampling clocks generated by optical time-division-multiplexing (OTDM) with fiber delay lines is analyzed and effective bit loss is calculated. A compensation method is proposed to decrease the dispersion-induced jitter. Simulations are performed and the results show the validity of the proposed compensation method. An experimental demonstration is carried out to verify the theoretical expression derived.

The purpose of this study was to assess the immediate effect of video feedback on the regulation and control of the standing back tuck somersault in the absence of vision. Two groups of male parkour athletes performed the standing back tuck somersault under both open and closed eyes conditions. The first group received video feedback, while the second group received verbal feedback. Concurrent analysis, including kinetic data from a force plate (Kistler Quattro-Jump) and kinematic data in two-dimensional by Kinovea freeware, was employed for motion and technical performance analysis. The results indicate that the loss of vision during the standing back tuck somersault affected only the take-off and ungrouping angle, as well as the vertical velocity and displacement. These effects were consistent regardless of the type of feedback provided (i.e.,video feedback or verbal feedback). Furthermore, a significant Vision × Feedback interaction was observed at the level of technical performance. This suggests that the use of video feedback enabled the parkour athletes to maintain a high level of technical performance both with and without vision (i.e.,13.56 vs. 13.00 points, respectively, p > .05 and d = 2.233). However, the verbal feedback group technical performance declined significantly under the no-vision condition compared with the vision condition (13.14 vs. 10.25 points, respectively, with and without vision, p < .001 and d = 2.382). We concluded that when the movement is proprioceptively controlled (i.e.,without vision), the video feedback enables the athletes to globally assess the technical deficiencies arising from the lack of vision and to correct them. These findings are discussed based on parkour athletes' ability to evaluate the kinematic parameters of the movement.

Image-based visual servoing guides a robotic system to its desired place through ongoing feedback from visual signals. However, interference such as object occlusion and camera drift may cause visual signal loss, ultimately leading to servo failure. This article proposes a novel continuous image-based visual servoing (CIBVS) approach to address the potential visual signal loss. A geometric relationship is established between the positions of natural features and servo features. In each iteration, natural features are coarsely matched between frames, and mismatched pairs are eliminated by the proposed refining score based on the geometric relationship. When visual signal loss occurs, CIBVS leverages the natural features and the geometric relationship to estimate the lost servo features through optimization, ensuring continuous and stable visual feedback generation. In simulation, CIBVS was evaluated across three scenarios and 750 test cases, achieving an enhanced success rate and estimation accuracy. In the real world, CIBVS was integrated into various robotic systems, including manipulators, drones, and ground vehicles, to achieve multiple tasks. Experimental results demonstrated that, in scenarios with visual signal loss, CIBVS achieved significant improvements over extended-Kalman-filter-based IBVS and visual-odometry-based IBVS in servoing success rate, estimation accuracy, and convergence speed.

We report the implementation and experimental feasibility demonstration of modular spatial cross-connects (SXCs) for spatial channel networks (SCNs) based on route-and-select architectures using packaged 19-core-fiber (19-CF)-based optical switches. The SXCs employ hermetically sealed core selective switches (CSSs), core selectors (CSs), and core port selectors (CPSs) integrated into a compact 1U rack-mount chassis with software-based polarity and core-arrangement management, enabling any-core-access, nondirectional, and contentionless spatial-channel (SCh) routing. We experimentally demonstrate hierarchical establishment, routing, and protection of SChs and wavelength channels; core-contention-free SCh establishment using CPS-based add/drop sections; and inter-domain SCh establishment and restoration in a heterogeneous 4-core-fiber (4-CF)/16-core-fiber (16-CF) SCN. The heterogeneous SCN is interconnected via a spatial gateway constructed using 19-CF CSSs and 4-C/19-C converters, with loss compensation provided by cladding-pumped 19-CF erbium-doped fiber amplifiers (EDFAs) and first-in-first-out-less core-pumped 4-CF EDFAs. Experimental results show low insertion loss, low inter-core crosstalk, a negligible optical-signal-to-noise-ratio penalty, and successful fault protection and restoration, demonstrating the practical feasibility and scalability of CSS-based modular SXCs for future large-scale SCNs.