Passive Stability and Active Control in a Rhythmic Task

2007 ◽  
Vol 98 (5) ◽  
pp. 2633-2646 ◽  
Author(s):  
Kunlin Wei ◽  
Tjeerd M. H. Dijkstra ◽  
Dagmar Sternad
Keyword(s):  
Steady State ◽  
Active Control ◽  
Human Performance ◽  
Passive Control ◽  
Basin Of Attraction ◽  
Relaxation Times ◽  
Passive Dynamics ◽  
Passive Stability ◽  
Set Up ◽  
Boundary Of Stability

Rhythmically bouncing a ball with a racket is a task that affords passively stable solutions as demonstrated by stability analyses of a mathematical model of the task. Passive stability implies that no active control is needed as errors die out without requiring corrective actions. Empirical results from human performance demonstrated that actors indeed exploit this passive dynamics in steady-state performance, thereby reducing computational demands of the task. The present study investigated the response to perturbations of different magnitudes designed on the basis of the model's basin of attraction. Humans performed the task in a virtual reality set-up with a haptic interface. Relaxation times of the performance errors showed significantly faster returns than predicted from the purely passive model, indicative of active error corrections. Systematic adaptations in the racket trajectories were a monotonic function of the perturbation magnitudes, indicating that active control was applied in proportion to the perturbation. These results did not indicate any sensitivity to the boundary of stability. Yet the influence of passive dynamics was also seen: the pattern of relaxation times in the major performance variable ball height was consistent with qualitative predictions derived from the basin of attraction and racket accelerations at contact were generally negative signaling use of passive stability. These findings suggest that the fast return back to steady state was assisted by passive properties of the task. It was concluded that actors used a blend of active and passive control for all sizes of perturbations.

On the magnetic resonance of an alined spin-assembly

1972 ◽  
Vol 330 (1581) ◽  
pp. 265-270 ◽  
Keyword(s):  
Steady State ◽  
Magnetic Resonance ◽  
Equations Of Motion ◽  
Double Resonance ◽  
Relaxation Times ◽  
Spin Orientation ◽  
Optical Double Resonance ◽  
Set Up ◽  
Slow Passage ◽  
Steady State Solutions

The state of a spin-assembly of arbitrary J , undergoing magnetic resonance, is characterized by the multipole components p q k of the instantaneous spin-polarization which describe spin-orientation ( k = 1), spin-alinement ( k = 2), etc. Equations of motion analogous to Bloch’s equations ( k = 1) are set up for the multipole components of different k , introducing terms which describe phenomenologically ( a ) the pumping of the longitudinal multipole components ( q = 0), and ( b ) the independent but anisotropic relaxation of multipole components of different k . Steady-state solutions are obtained. In particular, the slow-passage magnetic resonance functions for the alinement components, which involve three relaxation times, are calculated explicitly. For the particular case of isotropic relaxation, these resonance functions reduce to the form originally derived for optical double resonance for a J = 1 assembly. It is emphasized that the damping constant which is involved is that for alinement.

scholarly journals A Critical Review of Supersonic Flow Control for High-Speed Applications

2021 ◽  
Vol 11 (15) ◽  
pp. 6899
Author(s):  
Abdul Aabid ◽  
Sher Afghan Khan ◽  
Muneer Baig
Keyword(s):  
Supersonic Flow ◽  
Flow Control ◽  
Active Control ◽  
Critical Review ◽  
High Speed ◽  
Passive Control ◽  
Control Method ◽  
Sudden Expansion ◽  
Control Approach ◽  
Cost Efficient

In high-speed fluid dynamics, base pressure controls find many engineering applications, such as in the automobile and defense industries. Several studies have been reported on flow control with sudden expansion duct. Passive control was found to be more beneficial in the last four decades and is used in devices such as cavities, ribs, aerospikes, etc., but these need additional control mechanics and objects to control the flow. Therefore, in the last two decades, the active control method has been used via a microjet controller at the base region of the suddenly expanded duct of the convergent–divergent (CD) nozzle to control the flow, which was found to be a cost-efficient and energy-saving method. Hence, in this paper, a systemic literature review is conducted to investigate the research gap by reviewing the exhaustive work on the active control of high-speed aerodynamic flows from the nozzle as the major focus. Additionally, a basic idea about the nozzle and its configuration is discussed, and the passive control method for the control of flow, jet and noise are represented in order to investigate the existing contributions in supersonic speed applications. A critical review of the last two decades considering the challenges and limitations in this field is expressed. As a contribution, some major and minor gaps are introduced, and we plot the research trends in this field. As a result, this review can serve as guidance and an opportunity for scholars who want to use an active control approach via microjets for supersonic flow problems.

scholarly journals Evaluation of malignant effusions using MR-based T1 mapping

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
D. Kuetting ◽  
J. Luetkens ◽  
A. Faron ◽  
A. Isaak ◽  
U. Attenberger ◽  
...  
Keyword(s):  
T1 Mapping ◽  
Ex Vivo ◽  
Diagnostic Yield ◽  
Spin Echo ◽  
Relaxation Times ◽  
Inversion Recovery ◽  
Malignant Effusions ◽  
Mapping Techniques ◽  
Set Up ◽  
Post Hoc

AbstractOur aim was to investigate the diagnostic yield of rapid T1-mapping for the differentiation of malignant and non-malignant effusions in an ex-vivo set up. T1-mapping was performed with a fast modified Look-Locker inversion-recovery (MOLLI) acquisition and a combined turbo spin-echo and inversion-recovery sequence (TMIX) as reference. A total of 13 titrated albumin-solutions as well as 48 samples (29 ascites/pleural effusions from patients with malignancy; 19 from patients without malignancy) were examined. Samples were classified as malignant-positive histology, malignant-negative histology and non-malignant negative histology. In phantom analysis both mapping techniques correlated with albumin-content (MOLLI: r = − 0.97, TMIX: r = − 0.98). MOLLI T1 relaxation times were shorter in malignancy-positive histology fluids (2237 ± 137 ms) than in malignancy-negative histology fluids (2423 ± 357 ms) as well as than in non-malignant-negative histology fluids (2651 ± 139 ms); post hoc test for all intergroup comparisons: < 0.05. ROC analysis for differentiation between malignant and non-malignant effusions (malignant positive histology vs. all other) showed an (AUC) of 0.89 (95% CI 0.77–0.96). T1 mapping allows for non-invasive differentiation of malignant and non-malignant effusions in an ex-vivo set up.

Seismic Control Effect for Nonlinear Benchmark Building Using Passive or Semi-Active Damper

2002 ◽  
Author(s):  
Akira Fukukita ◽  
Tomoo Saito ◽  
Keiji Shiba
Keyword(s):  
Active Control ◽  
Passive Control ◽  
Feedforward Control ◽  
Electrical Power ◽  
Control Device ◽  
Control Effect ◽  
Damping Force ◽  
Active Device ◽  
Seismic Control ◽  
Control Forces

We study the control effect for a 20-story benchmark building and apply passive or semi-active control devices to the building. First, the viscous damping wall is selected as a passive control device which consists of two outer plates and one inner plate, facing each other with a small gap filled with viscous fluid. The damping force depends on the interstory velocity, temperature and the shearing area. Next, the variable oil damper is selected as a semi-active control device which can produce the control forces by little electrical power. We propose a damper model in which the damping coefficient changes according to both the response of the damper and control forces based on an LQG feedback and feedforward control theory. It is demonstrated from the results of a series of simulations that the both passive device and semi-active device can effectively reduce the response of the structure in various earthquake motions.

Control of Vibration Using Compliant Actuators

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Sannia Mareta ◽  
Dunant Halim ◽  
Atanas A. Popov
Keyword(s):  
Vibration Control ◽  
Active Control ◽  
Passive Control ◽  
Performance Comparison ◽  
Control Performance ◽  
Frequency Bandwidth ◽  
Series Configuration ◽  
Compliant Actuators ◽  
Stiffness And Damping ◽  
Compliant Actuator

This work proposes a method for controlling vibration using compliant-based actuators. The compliant actuator combines a conventional actuator with elastic elements in a series configuration. The benefits of compliant actuators for vibration control applications, demonstrated in this work, are twofold: (i) vibration reduction over a wide frequency bandwidth by passive control means and (ii) improvement of vibration control performance when active control is applied using the compliant actuator. The vibration control performance is compared with the control performance achieved using the well-known vibration absorber and conventional rigid actuator systems. The performance comparison showed that the compliant actuator provided a better flexibility in achieving vibration control over a certain frequency bandwidth. The passive and active control characteristics of the compliant actuator are investigated, which shows that the control performance is highly dependent on the compliant stiffness parameter. The active control characteristics are analyzed by using the proportional-derivative (PD) control strategy which demonstrated the capability of effectively changing the respective effective stiffness and damping of the system. These attractive dual passive–active control characteristics are therefore advantageous for achieving an effective vibration control system, particularly for controlling the vibration over a specific wide frequency bandwidth.

Active control of divertor heat and particle fluxes in EAST towards advanced steady state operations

2015 ◽  
Vol 463 ◽  
pp. 99-103 ◽  
Author(s):  
L. Wang ◽  
H.Y. Guo ◽  
J. Li ◽  
B.N. Wan ◽  
X.Z. Gong ◽  
...  
Keyword(s):  
Steady State ◽  
Active Control ◽  
Particle Fluxes

A shuffled frog-leaping algorithm based mixed-sensitivity H∞ control of a seismically excited structural building using MR dampers

2017 ◽  
Vol 24 (13) ◽  
pp. 2832-2852 ◽  
Author(s):  
Xiufang Lin ◽  
Shumei Chen ◽  
Guorong Huang
Keyword(s):  
Active Control ◽  
Passive Control ◽  
Structural Parameters ◽  
Mr Damper ◽  
Inverse Model ◽  
Shuffled Frog Leaping Algorithm ◽  
Weighting Functions ◽  
Inference System ◽  
Mr Dampers ◽  
Shuffled Frog Leaping

An intelligent robust controller, which combines a shuffled frog-leaping algorithm (SFLA) and an H∞ control strategy, is designed for a semi-active control system with magnetorheological (MR) dampers to reduce seismic responses of structures. Generally, the performance of mixed-sensitivity H∞ (MSH) control highly depends on expert experience in selecting the parameters of the weighting functions. In this study, as a recently-developed heuristic approach, a multi-objective SFLA with constraints is adopted to search for the optimal weighting functions. In the proposed semi-active control, firstly, based on the Bouc–Wen model, the forward dynamic characteristics of the MR damper are investigated through a series of tensile and compression experiments. Secondly, the MR damper inverse model is developed with an adaptive-network-based fuzzy inference system (ANFIS) technique. Finally, the SFLA-optimized MSH control approach integrated with the ANFIS inverse model is used to suppress the structural vibration. The simulation results for a three-story building model equipped with an MR damper verify that the proposed semi-active control method outperforms fuzzy control and two passive control methods. Besides, with the proposed strategy, the changes in structural parameters and earthquake excitations can be satisfactorily dealt with.

Dynamic Absorption by Passive and Active Control1

2000 ◽  
Vol 122 (4) ◽  
pp. 429-433 ◽  
Author(s):  
Kumar Vikram Singh ◽  
Yitshak M. Ram
Keyword(s):  
Steady State ◽  
Active Control ◽  
Conservative System ◽  
Degree Of Freedom ◽  
Loss Of Stability ◽  
Steady State Motion ◽  
Damped System ◽  
Single Sensor ◽  
Dynamic Absorber

The motion of a particular degree-of-freedom in a harmonically excited conservative system can be vanished by attaching an appropriate dynamic absorber to it. It is shown here that under certain conditions, which are characterized in the paper, the steady state motion of a damped system may be completely absorbed, without loss of stability, by active control implementing a single sensor and an actuator. The results are established theoretically and they are demonstrated by means of analytical examples. [S0739-3717(00)02104-8]

Me and My VE, Part 5: Applications in Human Factors Research and Practice

2018 ◽  
Vol 62 (1) ◽  
pp. 2051-2055
Author(s):  
Randall Spain ◽  
Benjamin Goldberg ◽  
Jeffrey Hansberger ◽  
Tami Griffith ◽  
Jeremy Flynn ◽  
...  
Keyword(s):  
Virtual Reality ◽  
Human Factors ◽  
Virtual Environments ◽  
Virtual Environment ◽  
Human Performance ◽  
Mixed Reality ◽  
Research Training ◽  
Research And Practice ◽  
Set Up ◽  
Human Factors Research

Recent advances in technology have made virtual environments, virtual reality, augmented reality, and simulations more affordable and accessible to researchers, companies, and the general public, which has led to many novel use cases and applications. A key objective of human factors research and practice is determining how these technology-rich applications can be designed and applied to improve human performance across a variety of contexts. This session will demonstrate some of the distinct and diverse uses of virtual environments and mixed reality environments in an alternative format. The session will begin with each demonstrator providing a brief overview of their virtual environment (VE) and a description of how it has been used to address a particular problem or research need. Following the description portion of the session, each VE will be set-up at a demonstration station in the room, and session attendees will be encouraged to directly interact with the virtual environment and ask demonstrators questions about their research and inquire about the effectiveness of using VE for research, training, and evaluation purposes. The overall objective of this alternative session is to increase the awareness of how human factors professionals use VE technologies and increase the awareness of the capabilities and limitations of VE in supporting the work of HF professionals.

scholarly journals Active Control and Validation of the Electric Vehicle Powertrain System Using the Vehicle Cluster Environment

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3642 ◽  
Author(s):  
Ming Ye ◽  
Yitao Long ◽  
Yi Sui ◽  
Yonggang Liu ◽  
Qiao Li
Keyword(s):  
Active Control ◽  
Control Strategy ◽  
Passive Control ◽  
Prediction Algorithm ◽  
Control Effect ◽  
Demand Forecast ◽  
Powertrain System ◽  
Cluster Environment ◽  
Active Control Strategy ◽  
Vehicle Powertrain

With the development of intelligent vehicle technologies, vehicles can obtain more and more information from various sensors. Many researchers have focused on the vertical and horizontal relationships between vehicles in a vehicle cluster environment and control of the vehicle power system. When the vehicle is driving in the cluster environment, the powertrain system should quickly respond to the driver’s dynamic demand, so as to achieve the purpose of quickly passing through the cluster environment. The vehicle powertrain system should be regarded as a separate individual to research its active control strategy in a vehicle cluster environment to improve the control effect. In this study, the driving characteristics of vehicles in a cluster environment have been analyzed, and a vehicle power-demanded prediction algorithm based on a vehicle-following model has been proposed in a cluster environment. Based on the vehicle power demand forecast and driver operation, an active control strategy of the vehicle powertrain system has been designed considering the passive control strategy of the powertrain system. The results show that the vehicle powertrain system can ensure a sufficient backup power with the active control proposed in the paper, and the motor efficiency is improved by 0.61% compared with that of the passive control strategy. Moreover, the overall efficiency of the powertrain system is increased by 0.6% and the effectiveness of the active control is validated using the vehicle cluster environment.

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