One-degree Of Freedom Research Articles

Application of Smoothed Particle Hydrodynamics Method for the Analysis of the Flow Past Vertical Vortex Turbine of a Micro Hydropower

The Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) has been applied to simulate the flow through a Gravitational Vertical Turbine (GVT) configuration and the motion of the turbine of a small hydropower system. The turbine blades are assumed to be rigid bodies moving with one-degree of freedom, which is the rotation about its shaft due the hydrodynamic forces of the flow. The intake flow is an open channel flow which falls into a cylindrical basin which houses the turbine and impinges on the turbine blades. The method of simulation is the Weakly Compressible Smoothed Hydrodynamics (WCSPH) with the turbulence models in the equations of motion and the boundary conditions. The results are compared with a laboratory experiments conducted for the same dimension and the configuration. The flow features agree well and the motion of the turbine with a representative mass and a load agrees reasonably with the laboratory experiments

Prescribed Performance Control for the Upper-Limb Exoskeleton System in Passive Rehabilitation Training Tasks

In this study, a model-free adaptive sliding mode control method was developed in combination with the prescribed performance method. On this basis, this study attempted to fulfill the joint position tracking trajectory task for the one-degree of freedom (DOF) upper-limb exoskeleton in passive robot-assisted rehabilitation. The proposed method is capable of addressing the defect of the initial error in the controller design and the application by adopting a tuning function, as compared with other prescribed performance methods. Moreover, the method developed here was not determined by the dynamic model parameters, which merely exploit the input and output data. Theoretically, the stability exhibited by the proposed controller and the tracking performance can be demonstrated. From the experimental results, the root mean square of the tracking error is equal to 1.06 degrees, and the steady-state tracking error converges to 1.91 degrees. These results can verify the expected performance of the developed control method.

AN INTELLIGENT WEARABLE ROBOTIC DEVICE FOR KNEE REHABILITATION

Around the globe, the population suffered with stroke and spinal cord injury are rapidly increasing who are in need of an effective and efficient solution for their day to day life management. Paraplegia is a form of paralysis in which function is substantially impeded from the waist down or lower extremities but not the arms and it is sometimes called as partial paralysis. More than 73% people with paraplegia have perfectly healthy legs. The main aim of this proposed study is to develop an efficient rehabilitation system to treat paralysis patients of paraplegia. In this proposed research work, an assistive knee exoskeleton is designed and developed as a wearable robot with One Degree of Freedom (ODF) movement. This system is attached with the disabled limb with the aim of delivering appropriate motion and pragmatic functionality to the affected knee for suitable rehabilitation. This exoskeleton knee is controlled by the instrumented cane as a wearable sensory system to establish the coordinated movement through patient’s motion task estimation in order to control the trajectory of ODF exoskeleton robot. The computational intelligent control systems provides assisted rehabilitation motion in coherence with the motion of other unassisted upper limbs through the wearable sensors and switches in the instrumented cane. The instrumented cane is a helpful assistive device for rehabilitation in terms of balance and movement for those who suffering neurological disorders, in particular stroke and spinal cord injury. The pilot study on a subject using the proposed system describes utilization of instrumented cane as a feasible interface between the patient and exoskeleton to improve in terms of motion in their day-to-day activities. Also, the system is designed with inertial measurement module integrated with wireless communication device in order to assist real-time control of exoskeleton. The outcomes of the proposed research work validated and appreciated by the expert physicians and therapists. This study strives the purpose of an instrumented cane that able to contribute to the cognitively assisted locomotion technology as well as improves the mobility of physically challenged people.

Open Access Dataset, Toolbox and Benchmark Processing Results of High-Density Surface Electromyogram Recordings.

We provide an open access dataset of High densitY Surface Electromyogram (HD-sEMG) Recordings (named "Hyser"), a toolbox for neural interface research, and benchmark results for pattern recognition and EMG-force applications. Data from 20 subjects were acquired twice per subject on different days following the same experimental paradigm. We acquired 256-channel HD-sEMG from forearm muscles during dexterous finger manipulations. This Hyser dataset contains five sub-datasets as: (1) pattern recognition (PR) dataset acquired during 34 commonly used hand gestures, (2) maximal voluntary muscle contraction (MVC) dataset while subjects contracted each individual finger, (3) one-degree of freedom (DoF) dataset acquired during force-varying contraction of each individual finger, (4) N-DoF dataset acquired during prescribed contractions of combinations of multiple fingers, and (5) random task dataset acquired during random contraction of combinations of fingers without any prescribed force trajectory. Dataset 1 can be used for gesture recognition studies. Datasets 2-5 also recorded individual finger forces, thus can be used for studies on proportional control of neuroprostheses. Our toolbox can be used to: (1) analyze each of the five datasets using standard benchmark methods and (2) decompose HD-sEMG signals into motor unit action potentials via independent component analysis. We expect our dataset, toolbox and benchmark analyses can provide a unique platform to promote a wide range of neural interface research and collaboration among neural rehabilitation engineers.

Конкуренция режимов колебаний плохо обтекаемого тела в воздушном потоке

Based on well-known mathematical models describing vibrations in the gas flow of a bluff body with one degree of freedom, a model of vibrations of a body with two degrees of freedom is proposed. The equations of transverse translational vibrations and rotational vibrations of an elastically fixed body around an axis perpendicular to the velocity vector of the incoming flow are obtained. Using the Krylov-Bogolyubov method in the first approximation, the equations are reduced to equations for slowly varying amplitudes and frequencies of vibrations. It turned out that the differential equations written for the squares of dimensionless amplitudes of translational and rotational vibrations coincide with the well-known Lotka-Volterra equations describing competition between two species of animals that eat the same food. The coefficients of the equations depend on the velocity of the incoming flow. The model is verified in the experiments in the wind tunnel.

Low-gain feedback controller for a real soft actuated knee rehabilitation device using a state observer

Rehabilitation devices using soft actuation have been designed recently due to their characteristics in the human-robot interaction. Though, the analysis and control of these kinds of systems are challenging. We have designed a five-link knee rehabilitation device actuated in two of the five joints. This system can be reconfigured to attend a wide range of patients according to their height. We use elastic actuation to help the motion at the knee joint. In this work, we simplify the rehabilitation device modelling into a one-degree of freedom (DoF) soft actuated system. We present the design and implementation of a dynamic feedback controller to track a desired reference. For the proposed controller, we require an estimation of the system stiffness and some of the states, so we propose a state observer as part of the design. As a result, we present the design and implementation of the controller with a state observer that follows a desired angular joint trajectory with the desired stiffness. We demonstrate in simulation, by performing different tests oriented to carry out rehabilitation routines, the effectiveness, and stability of the controlled system which responds effectively to disturbances.

Low-gain feedback controller for a real soft actuated knee rehabilitation device using a state observer

Rehabilitation devices using soft actuation have been designed recently due to their characteristics in the human-robot interaction. Though, the analysis and control of these kinds of systems are challenging. We have designed a five-link knee rehabilitation device actuated in two of the five joints. This system can be reconfigured to attend a wide range of patients according to their height. We use elastic actuation to help the motion at the knee joint. In this work, we simplify the rehabilitation device modelling into a one-degree of freedom (DoF) soft actuated system. We present the design and implementation of a dynamic feedback controller to track a desired reference. For the proposed controller, we require an estimation of the system stiffness and some of the states, so we propose a state observer as part of the design. As a result, we present the design and implementation of the controller with a state observer that follows a desired angular joint trajectory with the desired stiffness. We demonstrate in simulation, by performing different tests oriented to carry out rehabilitation routines, the effectiveness, and stability of the controlled system which responds effectively to disturbances.

Multi-ethnic analysis shows genetic risk and environmental predictors interact to influence 25(OH)D concentration and optimal vitamin D intake.

25-Hydroxyvitamin D (25(OH)D) concentration is a complex trait with genetic and environmental predictors that may determine how much vitamin D exposure is required to reach optimal concentration. Interactions between continuous measures of a polygenic score (PGS) and vitamin D intake (PGS*intake) or available ultraviolet (UV) radiation (PGS*UV) were evaluated in individuals of African (n = 1,099) or European (n = 8,569) ancestries. Interaction terms and joint effects (main and interaction terms) were tested using one-degree of freedom (1-DF) and 2-DF models, respectively. Models controlled for age, sex, body mass index, cohort, and dietary intake/available UV. In addition, in participants achieving Institute of Medicine (IOM) vitamin D intake recommendations, 25(OH)D was evaluated by level PGS. The 2-DF PGS*intake, 1-DF PGS*UV, and 2-DF PGS*UV results were statistically significant in participants of European ancestry (p = 3.3 × 10-18 , p = 2.1 × 10-2 , and p = 2.4 × 10-19 , respectively), but not in those of African ancestry. In European-ancestry participants reaching IOM vitamin D intake guidelines, the percent of participants achieving adequate 25(OH)D ( >20 ng/ml) increased as genetic risk decreased (72% vs. 89% in highest vs. lowest risk; p = .018). Available UV radiation and vitamin D intake interact with genetics to influence 25(OH)D. Individuals with higher genetic risk may require more vitamin D exposure to maintain optimal 25(OH)D concentrations.

Stiffness effects on laminar separation flutter

This work explores self-sustained pitching oscillations of a NACA0012 airfoil operating at low-to-moderate Reynolds numbers in which the aerodynamic flow is in a transitional regime. One-degree of freedom (1-DOF) pitching oscillations are explored for chord-based Reynolds numbers of Rec=77,000 and 110,000, which fall on the lower end of the flutter regime, over a large range of torsional spring constants. Laminar separation flutter (LSF) is shown to persist over several orders of magnitude of structural rigidity. At the Reynolds numbers tested, the effect of changing structural rigidity at a fixed Reynolds number exhibits remarkable similarity to the effect of varying Reynolds number at a fixed stiffness. Although the two effects are not perfectly analogous, both parameters influence the timing of transition events relative to the limit-cycle. Raising stiffness values at either Reynolds number causes the structural response to outpace boundary layer transition which in turn yields an increasingly nonlinear aeroelastic response. Oscillations are no longer sustained when the structural frequency merges with the frequency of the aeroelastic response. At this point, the slow relaxation time of boundary layer transition fails to keep pace with the structural frequency and the processes that sustain LSF are inhibited. Oscillations terminate at a lower stiffness in the lower Reynolds number case—an apparent effect of slower boundary layer transition. Interestingly, hysteresis patterns and flow topologies coalesce into nearly identical topologies for both Reynolds numbers when stiffness is very low.

Likelihood Ratio Tests for a Large Directed Acyclic Graph

Inference of directional pairwise relations between interacting units in a directed acyclic graph (DAG), such as a regulatory gene network, is common in practice, imposing challenges because of lack of inferential tools. For example, inferring a specific gene pathway of a regulatory gene network is biologically important. Yet, frequentist inference of directionality of connections remains largely unexplored for regulatory models. In this article, we propose constrained likelihood ratio tests for inference of the connectivity as well as directionality subject to nonconvex acyclicity constraints in a Gaussian directed graphical model. Particularly, we derive the asymptotic distributions of the constrained likelihood ratios in a high-dimensional situation. For testing of connectivity, the asymptotic distribution is either chi-squared or normal depending on if the number of testable links in a DAG model is small. For testing of directionality, the asymptotic distribution is the minimum of d independent chi-squared variables with one-degree of freedom or a generalized Gamma distribution depending on if d is small, where d is number of breakpoints in a hypothesized pathway. Moreover, we develop a computational method to perform the proposed tests, which integrates an alternating direction method of multipliers and difference convex programming. Finally, the power analysis and simulations suggest that the tests achieve the desired objectives of inference. An analysis of an Alzheimer’s disease gene expression dataset illustrates the utility of the proposed method to infer a directed pathway in a gene network.

Experimental investigation of vortex- and wake-induced vibrations of tandem cylinders

ABSTRACTThis paper presents the experimental investigation of the wake-induced vibration (WIV) and vortex-induced vibration (VIV) acting on two circular cylinders. In particular, a riser installed in an offshore field may experience flow interferences between adjacent risers. Accordingly, the scaled models are arranged in a tandem configuration to observe the flow interference between the cylinders. The upstream cylinder is either fixed or allowed to have one-degree of freedom (1-DOF) motion, whereas the downstream cylinder is allowed to have two degrees of freedom (2-DOF) motion. The experimental test is conducted in a circulating water channel with cylinders that are connected by linear springs in two horizontal directions. A three-dimensional displacement metre and load cell are employed to measure the motion and hydrodynamic force of the cylinder, respectively. From the experiment, we identify that there are relative effects between the VIV and WIV with respect to selected parameters.

Numerical investigation of vortex-induced vibration of an elastically mounted circular cylinder with One-degree of freedom at high Reynolds number using different turbulent models

This study presents numerical investigation for flow around cylinder at Reynolds number = 104 using different turbulent models. Numerical simulations have been conducted for fixed cylinder case at Reynolds number = 104 and for cylinder free to oscillate in cross-flow direction, at Reynolds number O (104), mass–damping ratio = 0.011 and range of frequency ratio wt = 0.4–1.4 using two-dimensional Reynolds-averaged Navier–Stokes equations. In the literature, the study has been conducted using detached eddy simulation, large eddy simulation and direct numerical simulation which are comparatively expensive in terms of computational cost. This study utilizes the Reynolds-averaged Navier–Stokes shear stress transport k-ω and realizable k-ε models to investigate the flow around fixed cylinder and flow around cylinder constrained to oscillate in cross-flow direction only. Hydrodynamic coefficients, vortex mode shape and maximum amplitude ( Ay/ D) extracted from this study are compared with detached eddy simulation, large eddy simulation and direct numerical simulation results. Results obtained using two-dimensional Reynolds-averaged Navier–Stokes shear stress transport k-ω model are encouraging, while realizable k-ε model is unable to capture the entire response branches. In addition, broad range of “lock-in” region is observed due to delay in capturing the transition from upper to lower branch during two-dimensional realizable k-ε analyses.

On the role of flow transition in laminar separation flutter

This work explores self-sustained pitching oscillations of a NACA0012 airfoil operating at low-to-moderate Reynolds numbers in which the aerodynamic flow is in a transitional regime. One-degree of freedom (DOF) pitching oscillations were explored over a range of Reynolds numbers (7.7×104<Rec≤2.0×105) using high-order implicit large-eddy simulation coupled with structural dynamics. Limit-cycle oscillation is observed at all Reynolds numbers tested but requires a disturbance to initiate at the highest flow speeds identifying a bifurcation in possible solution states. In all cases, aerodynamic loading is dominated by primarily two features. Negative aerodynamic damping is largely provided by suction beneath a separation bubble located behind the elastic axis. This feature induces a moment that reinforces the pitch-rate at small angles of incidence and is directly influenced by flow transition at different Reynolds numbers. Open trailing edge separation on the opposite surface transitions and reattaches immediately preceding the largest angles of incidence. This process imparts a spike in the pitching moment that opposes the pitch-rate and briefly damps oscillations. Transition of the detached shear layer occurs at smaller angles of incidence as Reynolds number is increased, attenuating oscillation amplitude as Reynolds number is increased.

IMC based Fractional Order Controller Design for Specific Non-Minimum Phase Systems

Internal model control (IMC) structure is derived from classical control by introducing the model of plant in the control loop and thereby having significant advantages over classical control such as dual stability, perfect control and zero-steady state offset. The basic one degree of freedom (ODF) IMC provides good compromise between set-point tracking and disturbance rejection and works well for non-minimum phase (NMP) systems. In this work, an IMC based fractional order (FO) controller is designed for NMP system which satisfy desired phase margin (ϕm) at a desired gain-crossover frequency (ωg). The domain of desired ϕm and ωg is provided from which they can be selected. Simulation studies are done for (i) DC-DC boost converter which is a NMP system with one zero in right half of s-plane and (ii) first order plus time delay (FOPTD) system which is also a NMP system because of the delay. Significance of the proposed methodology is verified by comparing with other well-known techniques in IMC based on the performance measures, such as rise time (Tr), settling time (Ts) and overshoot (%Mp) and performance indices such as integral square error (ISE), integral absolute error (IAE) and integral of the time weighted absolute error (ITAE).

2C25 Application of sampled-data control by using vibration manipulation function to suppress residual vibration of travelling crane(The 12th International Conference on Motion and Vibration Control)

Vibration manipulation function is applied as a feedforward function to suppress residual vibration of a hoisting load in one-dimensional overhead travelling crane. The system is modeled as a pendulum of one-degree-of-freedom (ODF) with enforced acceleration of a trolley. In case of small initial swing angle of the wire of the crane, the residual vibration of the load can be vanished by this method in one natural period. Although, in case of large initial angle, certain amount of residual vibration remains, it can be eliminated by repeated enforce acceleration of trolley under vibration manipulation function with sampled-data control in every natural period. Some examples of numerical simulation are shown to use vibration manipulation function in crane operation. The residual vibration of the load can be suppressed in any time of crane work, as far as the trolley travels in constant speed including static position at the beginning of operation. This analytic feedforward function could be used for automatic carne machine or tutoring software for operator's training.

The preliminary results of a force feedback control for Sensorized Medical Robotics

A laparoscopic surgery system by using a robot holds many problems. Among these, its inability in delivering touching sensation to a surgeon is raised as the biggest problem. The current paper attempted to find a force feedback controlling method at the time of performing movement by using one-degree of freedom (DOF) arm of slave and master system that is used in the programming based system. The study was two methods experience force feedback control; In the first place used force sensors and otherwise, conducted for the force feedback control by using a force sensor and for the case when the sensor could not be used due to the spatial and systematic limitation. The realization of force feedback system was successful, and the experiment results of force feedback control and current based force feedback control mode based on the force sensors of one-DOF system indicates that it could be directly applied to the another multi-DOF surgical robot system that is currently under the development.

Dynamics of electrostatic microelectromechanical systems actuators

Electrostatic actuators are simple but important switching devices for microelectromechanical systems applications. Due to the difficulties associated with the electrostatic nonlinearity, precise mathematical description is often hard to obtain for the dynamics of these actuators. Here we present two sharp theorems concerning the dynamics of an undamped electrostatic actuator with one-degree of freedom, subject to linear and nonlinear elastic forces, respectively. We prove that both situations are characterized by the onset of one-stagnation-point periodic response below a well-defined pull-in voltage and a finite-time touch-down or collapse of the actuator above this pull-in voltage. In the linear-force situation, the stagnation level, pull-in voltage, and pull-in coordinate of the movable electrode may all be determined explicitly, following the recent work of Leus and Elata based on numerics. Furthermore, in the nonlinear-force situation, the stagnation level, pull-in voltage, and pull-in coordinate may be described completely in terms of the electrostatic and mechanical parameters of the model so that they approach those in the linear-force situation monotonically in the zero nonlinear-force limit.

Dynamics Analysis and Simulation of one-DOF Parallel Manipulator

One-degree of freedom (DOF) parallel manipulator of sorting robot is of vital importance for municipal solid waste (MSW) sorting. The motion velocity of the manipulator is very high. So the inertia forces seriously affect the motion characteristics of the manipulator. In order to solve this problem, this paper makes force analysis for the manipulator by using method of body-separation. In the process of the force analysis, the inertia forces are took into account. The dynamics equations of the manipulator are established based on D’Alember’s principle and dynamics sequence solution. The sequence to solve all the equations is listed. Dynamics simulation of one-DOF parallel manipulator is made to visualize the solved results of the equations by using software ADAMS.

The Parallel Control Structure for Transparent Online Tuning

Abstract In this paper, the Parallel Control Structure (PCS) as an alternative to the Conventional Control Structure (CCS) is proposed to perform Transparent Online Tuning – the ability to independently manipulate the three most important performance attributes of a control loop: Set-point Tracking Performance, Disturbance-Rejection Performance and Robustness. Firstly, the extent to which Transparent Online Tuning is possible in the PCS is described and it is shown through derivations that the PCS maintains its transparent tuning feature even under mismatch conditions, provided that the Robust Stability Condition is satisfied. Secondly, by utilizing its transparent tuning feature the PCS can have greater Robustness than a Conventional Control Structure (CCS) with no loss in tracking performance. In addition, a generalized design procedure is presented which will direct the user towards proper utilization of the PCS’ transparent tuning. Simulation and experimental results are used to demonstrate the proposed design procedure and the Transparent Online Tuning feature of the PCS. Arguments will be presented to highlight that the PCS’ features are not available in a general Two Degree of Freedom (TDF) and One Degree of Freedom (ODF) structures.

Detecting digital chameleons

Conversations are characterized by an interactional synchrony between verbal and nonverbal behaviors [Kendon, A. (1970). Movement coordination in social interaction: some examples described. Acta Psychologica, 32(2), 101-125]. A subset of these contingent conversational behaviors is direct mimicry. During face to face interaction, people who mimic the verbal [Giles, H., Coupland, J., & Coupland, N. (1991). Accommodation theory: Communication, context, and consequence. In Giles, H., Coupland, J., & Coupland, N. Contexts of accommodation. Developments in applied sociolinguistics. Cambridge: Cambridge University Press] and nonverbal behaviors [Chartrand, T. L., & Bargh, J. A. (1999). The chameleon effect: the perception-behavior link and social interaction. Journal of Personality and Social Psychology, 76, 893-910] gain social advantage. Most research examining mimicry behavior in interaction examines 'implicit mimicry' in which the mimicked individual is unaware of the behavior of the mimicker. In this paper, we examined how effective people were at explicitly detecting mimicking computer agents and the consequences of mimic detection in terms of social influence and interactional synchrony. In Experiment 1, participant pairs engaged in a ''one-degree of freedom'' Turing Test. When the computer agent mimicked them, users were significantly worse than chance at identifying the other human. In Experiment 2, participants were more likely to detect mimicry in an agent that mirror-mimicked their head movements (three degrees of freedom) than agents that either congruently mimicked their behaviors or mimicked those movements on another rotational axis. We discuss implications for theories of interactivity.