Controllable Degrees Of Freedom Research Articles

Adapt or Perish? Exploring the Effectiveness of Adaptive DoF Control Interaction Methods for Assistive Robot Arms

Robot arms are one of many assistive technologies used by people with motor impairments. Assistive robot arms can allow people to perform activities of daily living (ADL) involving grasping and manipulating objects in their environment without the assistance of caregivers. Suitable input devices (e.g., joysticks) mostly have two Degrees of Freedom (DoF), while most assistive robot arms have six or more. This results in time-consuming and cognitively demanding mode switches to change the mapping of DoFs to control the robot. One option to decrease the difficulty of controlling a high-DoF assistive robot arm using a low-DoF input device is to assign different combinations of movement-DoFs to the device’s input DoFs depending on the current situation (adaptive control). To explore this method of control, we designed two adaptive control methods for a realistic virtual 3D environment. We evaluated our methods against a commonly used non-adaptive control method that requires the user to switch controls manually. This was conducted in a simulated remote study that used Virtual Reality and involved 39 non-disabled participants. Our results show that the number of mode switches necessary to complete a simple pick-and-place task decreases significantly when using an adaptive control type. In contrast, the task completion time and workload stay the same. A thematic analysis of qualitative feedback of our participants suggests that a longer period of training could further improve the performance of adaptive control methods.

Automation of control degrees of freedom in Aspen Hysys

Analysis of control degrees of freedom (CDOF) is a main step in control structure design. The CDOF in a process flow diagram (PFD) is the maximum number of manipulated material or energy streams. In this study, a CDOF analyzer is developed within Aspen Hysys simulation software by writing the scripts for enumeration of structural PFD parts i.e. boundary streams, recycle/bypass loops, circuits, holdup vessels and the engaged fluid phases in holdup vessels. The scripts are written in WinWrap Basic v10, the embedded language in Aspen Hysys. The function for identification of recycle/bypass loops is adopted from an algorithm for enumeration of chordless cycles in graph theory. Finally, the generality, reliability and ease of application of the developed analyzer are examined for analysis of several PFDs including simple units as well as the large-scale plants.

Artificial micro- and nano-structure enhanced long and very long-wavelength infrared detectors

The infrared detectors own the ability to convert information carried by photons radiated by objects into electrical signals, which broadens the horizons of human beings observing the natural environment and human activities. At present, long and very long-wavelength infrared detections have many applications in atmospheric monitoring, biological spectroscopy, night vision, etc. As the demand for high-performance infrared detectors grows rapidly, it is difficult for traditional infrared detectors to arrive at performance indicators such as high response rate, high response speed, and multi-dimensional detection. The artificial structure designed based on micro- and nano-optics can be coupled with infrared photons efficiently, and control the degrees of freedom of infrared light fields such as amplitude, polarization, phase, and wavelength comprehensively. The systems integrated by infrared detectors and artificial micro- and nano-photonic structures provide additional controllable degrees of freedom for infrared detectors. And they are expected to achieve high quantum efficiency and other merits such as high response rate, excellent polarization, and wavelength selectivity. In this review paper, the research progress of the application of artificial micro- and nano-structure in the long and very long-wavelength infrared bands is presented; the advantages, disadvantages, and the application status of different mechanisms are described in detail, which include surface plasmon polaritons, localized surface plasmon, resonant cavity structure, photon-trapping structure, metalens, spoof surface plasmon, gap plasmon, and phonon polariton. In addition, the development prospect and direction of artificial micro- and nano-structure in long-wave and very long-wave infrared devices are further pointed out.

Can Deep Synthesis of EMG Overcome the Geometric Growth of Training Data Required to Recognize Multiarticulate Motions?

By being predicated on supervised machine learning, pattern recognition approaches to myoelectric prosthesis control require electromyography (EMG) training data collected concurrently with every detectable motion. Within this framework, calibration protocols for simultaneous control of multifunctional prosthetic hands rapidly become prohibitively long-the number of unique motions grows geometrically with the number of controllable degrees of freedom (DoFs). This paper proposes a technique intended to circumvent this combinatorial explosion. Using EMG windows from 1-DoF motions as input and EMG windows from 2-DoF motions as targets, we train generative deep learning models to synthesize EMG windows appertaining to multi-DoF motions. Once trained, such models can be used to complete datasets consisting of only 1-DoF motions, enabling simple calibration protocols with durations that scale linearly with the number of DoFs. We evaluated synthetic EMG produced in this way via a classification task using a database of forearm surface EMG collected during 1-DoF and 2-DoF motions. Multi-output classifiers were trained on either (I) real data from 1-DoF and 2-DoF motions, (II) real data from only 1-DoF motions, or (III) real data from 1-DoF motions appended with synthetic EMG from 2-DoF motions. When tested on data containing all possible motions, classifiers trained on synthetic-appended data (III) significantly outperformed classifiers trained on 1-DoF real data (II), although significantly underperformed classifiers trained on both 1- and 2-DoF real data (I) (I < 0.05). These findings suggest that it is feasible to model EMG concurrent with multiarticulate motions as nonlinear combinations of EMG from constituent 1-DoF motions, and that such modelling can be harnessed to synthesize realistic training data.

In-place rotation of particles and time-average vibrational vortex on a Chladni plate

It is traditionally believed that particles will settle at the nodes or antinodes of a vibrating plate, forming stable standard or inverse Chladni patterns. The Chladni effect has been utilized to manipulate or pattern objects such as solid particles and even biological cells. The motion of particles near the nodal point is usually considered stochastic, and the stable and orderly movement of particles is impossible. Here, we experimentally show that the aggregation of particles can keep in-place rotating with different chirality at the nodal point of a vibrating plate, by utilizing specific dual-frequency oscillating signals to a single vibrator. To understand the motion of particles, irregular whirlpool force fields are calculated by considering the function of time dependent terms of the vibration response. Our findings reveal the time averaged vibrational vortex which can trap and rotate objects or particle clusters. It offers a new controllable degree of freedom for the movement of objects on a Chladni plate.

Machine learning based accurate recognition of fractional optical vortex modes in atmospheric environment

Optical vortex beam with fractional orbital angular momentum (OAM) has great potential to increase the capacity of optical communication and information processing in classical and quantum regimes. However, atmospheric turbulence (AT) in free space distorts the helical phase-front of vortex beams and causes the mode diffusion, seriously hindering the practical application. Herein, using a convolutional neural network approach with an improved residual neural network architecture, we overcome the hurdle to give the accurate recognition of the fractional OAM in the AT. As demonstrated on the petal interference patterns, a type of hybrid beams carrying double OAM modes is utilized to provide two controllable degrees of freedom for greater recognition of more subtle OAM modes, e.g., the fractional topological charge number l and the angular ratio n. Our studies show that with various l and n, the recognition accuracy of OAM over 20 000 images is as high as 85.30% even under the strong AT parameter (Cn2 = 5 × 10−14 m−2/3) and the long propagation distance (z = 1500 m). Our findings represent a remarkable achievement toward highly accurate recognition of fractional OAM with broad bandwidth in the atmospheric environment, expanding the applications for the general interest of machine learning based OAM optical communication.

Dense false target jamming suppression for airborne superimposed stepped frequency radar

Traditional space-time adaptive processing (STAP) suffers from severe performance degradation in dense false target jamming scenarios, especially mainlobe deceptive jamming. To solve this problem, the superimposed stepped frequency (SSF) radar is explored and its ability in suppressing the mainlobe deceptive jamming is studied in this work. SSF radar can provide a controllable degree of freedom in range domain besides the traditional freedom in angle and Doppler domains, which can be used to distinguish true and false targets. Thus, the range cascaded STAP approach is proposed to suppress the deceptive jamming and the clutter. First, the true target and clutter are blocked in carrier frequency domain. Then, the jamming is attenuated by the adaptive filter in carrier frequency domain with the jamming covariance matrix being constructed by the blocked data. At last, the clutter can be suppressed by the cascaded STAP in the space-time domain. Simulation results demonstrate the effectiveness of the proposed radar framework and the processing approach in suppressing the clutter and jamming.

Analisa Peralihan Tanggapan Tegangan Sistem Automatic Voltage Regulator (AVR) Tipe Arus Searah Dengan Pengendali 2 Derjat Kebebasan

This journal discusses the design and analysis of the transfer response of the direct cuurent type of Automatic Voltage Regulator (AVR) system with 2 degrees of freedom controller. Direct current type of the AVR system is represented in the form of transfer function. For 2 degrees of freedom controllers are designed using a parallel architecture with the help of Matlab software using predefined design criteria. The types of controllers used consist of Proportional Differential (PD), Proportional Integral (PI), Proportional Integral Differential (PID), Proportional Differential with First Order Filters in the Differential Section (PDF) and Proportional Intregral Differential with First Order Filters in the Differential Section (PIDF). For the transition analysis, the observed parameters consist of rise time, peak time, steady state time, maximum pass value and peak value. The results of the analysis show that the controller that meets the design criteria is a Proportional Differential (PD) controller with an uptime parameter value of 0.2808 seconds, a peak time of 1.3354 seconds, a steady state time of 0.7017 seconds, a maximum pass of 0% and a peak value of 0.9512. For the Proportional Differential controller with First Order Filter in the Differential Section (PDF) with an increase time parameter value of 0.4177 seconds, a peak time of 1.4684 seconds, a steady state time of 0.8453 seconds, a maximum pass of 0% and a peak value of 0.9502.

Tailoring a sub-diffraction optical focus via a straightforward interferometric approach

An approach for yielding light focuses below Abbe’s diffraction limit in Gaussian beams is presented. The method uses only standard passive optical elements as lenses, filters and mirrors and consists of a Michelson interferometric setup, where one of the light branches is modified in amplitude and/or phase. The focus narrowing process is carried out at the focal plane of a spherical lens by the interference of altered and unaltered light branches. The main focus features, namely, the focus intensity and size as well as the sidelobe intensity, are adjusted by varying two external parameters in a controllable manner under the conditions of pure destructive interference. Narrowing of the diffraction limit close to 40% with reduced intensity sidelobes (10%) is achieved. Due to the use of only lenses and mirrors, the approach does work with laser beams within a broad optical bandwidth ranging from infrared to ultraviolet in continuum regime as well as in ultra-short pulse regime. The method can also be implemented for high-power lasers and temporal domains. The focus-narrowing process emerges as a natural mechanism to the light interference, bringing a fresh perspective to applications from a few controllable degrees of freedom. The good performance of the sub-diffraction optical focus and the simplicity of the experimental setup promote new opportunities in fields ranging from optical manipulation of particles at sub-wavelength scale to optical writing and super-resolution microscopy.

Super-Twisting Sliding Mode Control Law Design for Attitude Tracking Task of a Spacecraft via Reaction Wheels

The attitude control has been recognized as one of the most important research topics for spacecraft. If the desired attitude trajectory cannot be tracked precisely, it may cause mission failures. In the real space mission environment, the unknown external perturbations, for example, atmospheric drag and solar radiation, should be taken into consideration. Such external perturbations could deviate the precision of the spacecraft orientation and thereby lead to a mission failure. Therefore, in this paper, a quaternion-based super-twisting sliding mode robust control law for the spacecraft attitude tracking is developed. The finite time stability based on the formulation of the linear matrix inequality (LMI) is also provided. To avoid losing the control degree of freedom due to the certain actuator fault, a redundant reaction wheels configuration is adopted. The actuators distribution associated force distribution matrix (FDM) is analyzed in detail. Finally, the reference tangent-normal-binormal (TNB) command generation strategy is implemented for simulating the scenario of the space mission. Finally, the simulation results reveal that the spacecraft can achieve the desired attitude trajectory tracking demands in the presence of the time-varying external disturbances.

Hybridized Defects in Solid-State Materials as Artificial Molecules.

Two-dimensional materials can be crafted with structural precision approaching the atomic scale, enabling quantum defects-by-design. These defects are frequently described as "artificial atoms" and are emerging optically addressable spin qubits. However, interactions and coupling of such artificial atoms with each other, in the presence of the lattice, warrants further investigation. Here we present the formation of "artificial molecules" in solids, introducing a chemical degree of freedom in control of quantum optoelectronic materials. Specifically, in monolayer hexagonal boron nitride as our model system, we observe configuration- and distance-dependent dissociation curves and hybridization of defect orbitals within the bandgap into bonding and antibonding orbitals, with splitting energies ranging from ∼10 meV to nearly 1 eV. We calculate the energetics of cis and trans out-of-plane defect pairs CHB-CHB against an in-plane defect pair CB-CB and find that in-plane defect pair interacts more strongly than out-of-plane pairs. We demonstrate an application of this chemical degree of freedom by varying the distance between CB and VN of CBVN and observe changes in the predicted peak absorption wavelength from the visible to the near-infrared spectral band. We envision leveraging this chemical degree of freedom of defect complexes to precisely control and tune defect properties toward engineering robust quantum memories and quantum emitters for quantum information science.

Optimal, blind-search modal wavefront correction in atmospheric turbulence. Part I: simulations

Modal control is an established tool in adaptive optics. It allows not only for the reduction in the controllable degrees of freedom, but also for filtering out unseen modes and optimizing gain on a mode-by-mode basis. When Zernike polynomials are employed as the modal basis for correcting atmospheric turbulence, their cross-correlations translate to correction errors. We propose optimal modal decomposition for gradient-descent-based wavefront sensorless adaptive optics, which is free of this problem. We adopt statistically independent Karhunen-Loève functions for iterative blind correction and analyze performance of the algorithm in static as well as in dynamic simulated turbulence conditions.

Finite Control Set Model Predictive Direct Power Control of Single-Phase Three-Level PWM Rectifier Based on Satisfactory Optimization

In this paper, a finite control set model predictive direct power control (FCS-MPDPC) method based on satisfactory optimization, for single-phase three-level PWM rectifier, is proposed to achieve global optimization that takes into account all its objectives and constraints. Satisfaction optimization aims to obtain the satisfactory solution after coordination of multiple goals, instead of the optimal solution of a single goal. By replacing “optimal” with “satisfaction”, more control degrees of freedom are acquired, so that low-priority auxiliary control objectives can participate in the optimization process. Meanwhile, in order to enhance the description accuracy of FCS-MPDPC method for the future trend of PWM rectifier, the prediction time domain is extended from the traditional single-step to multi-step, and the average switching frequency model is established to realize the low switching frequency control. The satisfactory optimized FCS-MPDPC method proposed in this paper is compared, through simulation and experimental results, with the standard FCS-MPDPC method, which verifies the effectiveness and superiority of the proposed algorithm.

Optimization of LLC Resonant Converter With Two Degrees of Freedom Based on Operation Stage Trajectory Analysis

LLC resonant DC-DC converter has been widely used in high power density and high efficiency applications. Pulse frequency modulation (PFM) is commonly applied due to its wide soft-switching range. In some special cases, phase shift modulation (PSM) is applied to widen voltage regulation range, improve light-load efficiency, or implement a soft start-up process. Because LLC is with 2 control degrees of freedom (2DOFs), switching frequency and duty ratio, a unified analysis and optimization for LLC with 2DOFs is desired. This paper makes an effort to present a unified time domain operation stage trajectories (OSTs) analysis of LLC. On this basis, a unified numerical optimization method is proposed with arbitrarily designed optimization objectives. With the proposed optimization method, the optimized LLC with 2DOFs is with better performance compared to conventional PFM and PSM, which is verified by the experimental results.

Improved Indirect Iterative Learning MIT Control Method for Ultrasonic Motor

MIT control strategy is a kind of model reference adaptive control method with the simplest structure. The reason why the structure is simple is that only the gain of the controlled object is adaptively adjusted. Because only the gain is adjusted, the ability of MIT control strategy to change the characteristics of the controlled object is limited. This also limits its application. In this paper, the simple idea of iterative learning control is introduced into MIT controller to increase the controller's ability to adjust the characteristics of the controlled object, and make it suitable for complex control objects. In the proposed control method, the output of the iterative learning controller is used to adjust the adaptive law of the MIT controller. The proposed control method is applied to the speed control system of ultrasonic motor. Experiments show that although only the gain of MIT controller can be adjusted, the learning process based on memory increases the degree of control freedom. Therefore, the dynamic characteristics of the system can be greatly changed, and the control performance can be significantly improved. Moreover, the proposed method only needs to add a simple P-type iterative learning controller to the MIT controller, and the increase of online calculation amount is small.

Dynamic analysis and decentralised control system design for diphenyl carbonate reactive distillation process

ABSTRACT Reactive distillation (RD), a process intensified technique, involves integrating reaction and separation in a single unit. High non-linearities associated with the RD process constrict the control degrees of freedom and set the key challenge in designing a robust control system. In the present work, the design is optimised for reactive distillation–diphenyl carbonate and a decentralised feedback control configuration is applied to carry out the control studies. A comparative decentralised control performance is studied for different transfer function models obtained by using analytical and optimisation-based process identification techniques. The controller parameters obtained from the simple internal model control tuning relations are applied to (i) the linear transfer function model and (ii) non-linear plant model. Set-point tracking and load rejection studies are carried out to compare the performance of different models and investigate the non-linear model’s controller performance.

Diseño e implementación de un controlador de 6 grados de libertad, para el sistema GRACE.

En este artículo el lector podrá obtener información sobre el escáner 3D de la Universidadde Groningen. El proceso de diseño incluyendo el control para el sistema con 6 grados delibertad, así como la luz que es regulada para tener datos limpios utilizando un algoritmo y unafuente de corriente constante es mostrado en el documento. La implementación y resultadosson mostrados, así entonces el lector puede analizar los materiales y métodos para futurasaplicaciones

Realization of acoustic spin transport in metasurface waveguides

Spin angular momentum enables fundamental insights for topological matters, and practical implications for information devices. Exploiting the spin of carriers and waves is critical to achieving more controllable degrees of freedom and robust transport processes. Yet, due to the curl-free nature of longitudinal waves distinct from transverse electromagnetic waves, spin angular momenta of acoustic waves in solids and fluids have never been unveiled only until recently. Here, we demonstrate a metasurface waveguide for sound carrying non-zero acoustic spin with tight spin-momentum coupling, which can assist the suppression of backscattering when scatters fail to flip the acoustic spin. This is achieved by imposing a soft boundary of the π reflection phase, realized by comb-like metasurfaces. With the special-boundary-defined spin texture, the acoustic spin transports are experimentally manifested, such as the suppression of acoustic corner-scattering, the spin-selected acoustic router with spin-Hall-like effect, and the phase modulator with rotated acoustic spin.

Fail-Safe Flight of a Fully-Actuated Quadrotor in a Single Motor Failure

In this letter, we introduce a new quadrotor fail-safe flight solution that can perform the same four controllable degrees-of-freedom flight as a standard multirotor even when a single thruster fails. The new solution employs a novel multirotor platform known as the T 3 -Multirotor and utilizes a distinctive strategy of actively controlling the center of gravity position to restore the controllable degrees of freedom. A dedicated control structure is introduced, along with a detailed analysis of the dynamic characteristics of the platform that change during emergency flights. Experimental results are provided to validate the feasibility of the proposed solution.

Multiparameter Controllable Chiral Optical Patterns

We demonstrate a method to generate multiparameter controllable chiral optical patterns. In the method, we introduce a phase calculation method of the rotation matrix and the transformation matrix. The controllable characteristics of the chiral optical patterns, which are generated by an annular subzone vortex phase plate, are demonstrated. The direction and spatial distribution of the eccentricity of the generated optical patterns can be freely regulated. The restriction on the direction of a chiral optical pattern by the single phase gradient (\ifmmode\pm\else\textpm\fi{}\ensuremath{\Delta}l) of an annular subzone vortex is solved. A chiral optical pattern is modulated by using the light-field superposition and phase shift, which is experimentally achieved by a spatial light modulator. The numerical and experimental results indicate that the controllable degrees of freedom are as many as five, namely, shape, size, direction, eccentricity, and number of arrays. Furthermore, we analyze the spatial propagation of the controllable chiral optical patterns in turbulence. The generation of chiral optical patterns has great potential application in optical tweezers, optical micromechanics, chiral microstructure fabrication, rotating microscopic illumination, and so on.