Multioperator Teleoperation of Multirobot Systems with Time Delay: Part II—Testbed Description

2002 ◽  
Vol 11 (3) ◽  
pp. 292-303 ◽  
Author(s):  
Nak Young Chong ◽  
Tetsuo Kotoku ◽  
Kohtaro Ohba ◽  
Hisayuki Sasaki ◽  
Kiyoshi Komoriya ◽  
...  
Keyword(s):  
Time Delay ◽  
A Priori ◽  
Coordinated Control ◽  
Multirobot Systems ◽  
Relay Station ◽  
Common Environment ◽  
Master Data ◽  
Master Station ◽  
Control Technologies ◽  
Operator Site

The Mechanical Engineering Laboratory (MEL) 1 has been developing coordinated control technologies for multi-telerobot cooperation in a common environment remotely controlled from multiple operators physically distant from each other. Previously, we learned about how the transmission delay over the network deteriorates the performance of telerobots through simulations. To overcome the operator's delayed visual perception arising from network throughput limitations, we have suggested several coordinated control aids at the local operator site. The testbed facilitates experiments with physical robots for validation beyond simulation. This paper mainly discusses the details of the testbed and investigates the use of an online predictive simulator to assist the operator in coping with time delay over the network. Practically, a common data relay station is suggested to reduce the travel distance of the master data over the network and enable multirobot predictive simulation at one's master station. Operators control their master to get their telerobot to cooperate with the counterpart telerobot using the predictive simulator as well as video image feedback. Specifically, exploiting the audio-visual resources of the simulator, operators can detect a priori the possibility of collision and coordinate conflicting motions between telerobots. We have demonstrated an object rearrangement task by two telerobots and two operators via an ethernet LAN that is subject to simulated delays and evaluated the validity of the online predictive simulator in Multioperator-Multirobot (MOMR) tele-cooperation. 1 On April 1, 2001, MEL merged into the National Institute of Advanced Industrial Science and Technology (AIST).

Multioperator Teleoperation of Multirobot Systems with Time Delay: Part I—Aids for Collision-Free Control

2002 ◽  
Vol 11 (3) ◽  
pp. 277-291 ◽  
Author(s):  
Nak Young Chong ◽  
Shun'ichi Kawabata ◽  
Kohtaro Ohba ◽  
Tetsuo Kotoku ◽  
Kiyoshi Komoriya ◽  
...  
Keyword(s):  
Time Delay ◽  
Coordinated Control ◽  
Difficult Problem ◽  
Multirobot Systems ◽  
Test Bed ◽  
Control Schemes ◽  
Plant Maintenance ◽  
Single Operator ◽  
Teleoperation Systems ◽  
Delayed Visual Feedback

In this paper, various coordinated control schemes are explored in Multioperatormultirobot (MOMR) teleoperation through a communication network with time delay. Over the past decades, problems and several notable results have been reported mainly in the Single-Operator–Single-Robot (SOSR) teleoperation system. Recently, the need for cooperation has rapidly emerged in many possible applications such as plant maintenance, construction, and surgery, because multirobot cooperation would have a significant advantage over a single robot in such cases. Thus, there is a growing interest in the control of multirobot systems in remote teleoperation, too. However, the time delay over the network would pose a more difficult problem to MOMR teleoperation systems and seriously affect their performance. In this work, our recent efforts devoted to the coordinated control of the MOMR teleoperation is described. First, we build a virtual experimental test bed to investigate the cooperation between two telerobots in remote environments. Then, different coordinated control aids are proposed to cope with collisions arising from delayed visual feedback from the remote location. To verify the validity of the proposed schemes, we perform extensive simulations of various planar rearrangement tasks employing local and remote graphics simulators over an ethernet LAN subject to a simulated communication delay.

scholarly journals A Priori “Imprinting” of General Relativity Itself on Some Tests of It?

2010 ◽  
Vol 2010 ◽  
pp. 1-5
Author(s):  
Lorenzo Iorio
Keyword(s):  
General Relativity ◽  
Gravitational Field ◽  
Time Delay ◽  
Solar System ◽  
Gravitational Constant ◽  
A Priori ◽  
Astronomical Unit ◽  
Space Curvature ◽  
Order Of Magnitude ◽  
Delay Tests

We investigate the effect of possible a priori “imprinting” effects of general relativity itself on satellite/spacecraft-based tests of it. We deal with some performed or proposed time-delay ranging experiments in the sun's gravitational field. It turns out that the “imprint” of general relativity on the Astronomical Unit and the solar gravitational constant , not solved for in the so far performed spacecraft-based time-delay tests, induces an a priori bias of the order of in typical solar system ranging experiments aimed to measure the space curvature PPN parameter . It is too small by one order of magnitude to be of concern for the performed Cassini experiment, but it would affect future planned or proposed tests aiming to reach a accuracy in determining .

Delay Identification in Thermoacoustics

2021 ◽  
Author(s):  
F. Gant ◽  
G. Ghirardo ◽  
A. Cuquel ◽  
M. R. Bothien
Keyword(s):  
Time Series ◽  
Time Delay ◽  
Additive White Gaussian Noise ◽  
A Priori ◽  
Accurate Estimate ◽  
Combustion Noise ◽  
Unknown Parameters ◽  
Acoustic Damping ◽  
The Stability ◽  
Low Order

Abstract The stability of thermoacoustic systems is often regulated by the time delay between acoustic perturbations and corresponding heat release fluctuations. An accurate estimate of this value is of great importance in applications, since even small modifications can introduce significant changes in the system behavior Different studies show that the nonlinear delayed dynamics typical of these systems can be well captured with low-order models. In the present work, a method is introduced to estimate the most likely value of the time delay of a single thermoacoustic mode from a measured acoustic pressure signal. The mode of interest is modeled by an oscillator equation, with a nonlinear delayed forcing term modeling the deterministic flame contribution and an additive white Gaussian noise to embed the stochastic combustion noise. Additionally, other thermoacoustic relevant parameters are estimated. The model accounts for a flame gain, for a flame saturation coefficient, for a linear acoustic damping and for the background combustion noise intensity. The pressure data time series is statistically analyzed and the set of unknown parameters is identified. Validation is performed with respect to synthetically generated time series and low order model simulations, for which the underlying delay is known a priori. A discussion follows about the accuracy of the method, in particular a comparison with existing methods is drawn.

scholarly journals Observer-Based Coordinated Control for Blended Braking System with Actuator Delay

Actuators ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 193
Author(s):  
Wenfei Li ◽  
Huiyun Li ◽  
Chao Huang ◽  
Kun Xu ◽  
Tianfu Sun ◽  
...  
Keyword(s):  
Time Delay ◽  
Sliding Mode ◽  
Coordinated Control ◽  
Time Delay Estimation ◽  
Smith Predictor ◽  
Braking System ◽  
Single Output ◽  
Braking Torque ◽  
Input Time ◽  
Friction Braking System

The coordinated control of a blended braking system is always a difficult task. In particular, blended braking control becomes more challenging when the braking actuator has an input time-delay and some states of the braking system cannot be measured. In order to improve the tracking performance, a coordinated control system was designed based on the input time-delay and state observation for a blended braking system comprising a motor braking system and friction braking system. The coordinated control consists of three parts: Sliding mode control, a multi-input single-output observer, and time-delay estimation-based Smith Predictor control. The sliding mode control is used to calculate the total command braking torque according to the desired braking performance and vehicle states. The multi-input single-output observer is used to simultaneously estimate the input time-delay and output braking torque of the friction braking system. With time-delay estimation-based Smith Predictor control, the friction braking system is able to effectively track the command braking torque of the friction braking system. The tracking of command braking torque is realized through the coordinated control of the motor braking system and friction braking system. In order to validate the effectiveness of the proposed approach, numerical simulations on a quarter-vehicle braking model were performed.

scholarly journals Cluster survey of the mid-altitude cusp – Part 2: Large-scale morphology

2009 ◽  
Vol 27 (5) ◽  
pp. 1875-1886 ◽  
Author(s):  
F. Pitout ◽  
C. P. Escoubet ◽  
B. Klecker ◽  
I. Dandouras
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Time Delay ◽  
Large Scale ◽  
Statistical Study ◽  
Proper Time ◽  
A Priori ◽  
Scale Morphology ◽  
External Conditions ◽  
Cluster Ion

Abstract. In this second part of our statistical study of the mid-altitude cusp, we compare the cusp morphology, as seen in the Cluster ion spectrometer (CIS), to the interplanetary magnetic field (IMF) orientation. We first recall the method we have used a) to define the cusp properties, b) to sort IMF conditions or behaviour in classes, c) to determine the proper time delay between the solar wind monitors and Cluster. Then, we define a few morphological features of the cusp and we relate these to the prevailing IMF. Our results reveal, among other things, that the occurrence of clearly dispersed ion structures in the cusp is 48%. From these dispersions, we infer the distance to reconnection site, which we relate to external conditions. In all other cases, the cusp exhibits a more disturbed behaviour in terms of ion structures and fall in our "discontinuous" or "irregular" categories. Among these, a few interesting cases of discontinuous cusps occurring under stable IMF conditions have been identified. They all occur when the IMF is dominated by its Y-component, which plays in principle in favour of anti-parallel reconnection but their wide MLT and latitudinal distributions is a priori incompatible with the anti-parallel reconnection hypothesis solely.

scholarly journals Joint Estimation of Doppler Stretch and Time Delay of Wideband Echoes for LFM Pulse Radar Based on Sigmoid-FRFT Transform under the Impulsive Noise Environment

Electronics ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 121 ◽  
Author(s):  
Li Li ◽  
Nicolas Younan ◽  
Xiaofei Shi
Keyword(s):  
Fourier Transform ◽  
Time Delay ◽  
Fractional Fourier Transform ◽  
Impulsive Noise ◽  
A Priori ◽  
Joint Estimation ◽  
Estimation Accuracy ◽  
A Priori Knowledge ◽  
Noise Interference ◽  
Priori Knowledge

To overcome the limitation of performance degradation of existing methods based on fractional Fourier transform in impulsive noise, and fractional lower-order statistics based method dependence on a priori knowledge of the noise, a novel Sigmoid fractional Fourier transform (Sigmoid-FRFT) is presented in this paper. This novel approach is then used to estimate the Doppler stretch and time delay. Furthermore, the properties of the Sigmoid transform, robustness and boundedness of the Sigmoid-FRFT to the S α S noise, and the computation complexity of the Sigmoid-FRFT method are presented to evaluate the performance of the proposed method. Simulation results and theoretical analysis are presented to demonstrate the applicability of the forgoing method. It is shown that the proposed method not only can effectively suppress impulsive noise interference but also does not need a priori knowledge of the noise, with higher estimation accuracy and lower computational complexity in impulsive noise environments.

scholarly journals A Novel Parameter Estimation Method Based on a Tuneable Sigmoid in Alpha-Stable Distribution Noise Environments

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 3012 ◽  
Author(s):  
Li Li ◽  
Nicolas Younan ◽  
Xiaofei Shi
Keyword(s):  
Parameter Estimation ◽  
Time Delay ◽  
Stable Distribution ◽  
Fractional Fourier Transform ◽  
Impulsive Noise ◽  
A Priori ◽  
Estimation Method ◽  
Fractional Power ◽  
Estimation Accuracy ◽  
Alpha Stable Distribution

In this paper, a novel method, that employs a fractional Fourier transform and a tuneable Sigmoid transform, is proposed, in order to estimate the Doppler stretch and time delay of wideband echoes for a linear frequency modulation (LFM) pulse radar in an alpha-stable distribution noise environment. Two novel functions, a tuneable Sigmoid fractional correlation function (TS-FC) and a tuneable Sigmoid fractional power spectrum density (TS-FPSD), are presented in this paper. The novel algorithm based on the TS-FPSD is then proposed to estimate the Doppler stretch and the time delay. Then, the derivation of unbiasedness and consistency is presented. Furthermore, the boundness of the TS-FPSD to the symmetric alpha stable ( S α S ) noise, the parameter selection of the TS-FPSD, and the feasibility analysis of the TS-FPSD, are presented to evaluate the performance of the proposed method. In addition, the Cramér–Rao bound for parameter estimation is derived and computed in closed form, which shows that better performance has been achieved. Simulation results and theoretical analysis are presented, to demonstrate the applicability of the forgoing method. It is shown that the proposed method can not only effectively suppress impulsive noise interference, but it also does not need a priori knowledge of the noise with higher estimation accuracy in alpha-stable distribution noise environments.

scholarly journals VIABLE NETWORK INTRUSION DETECTION ON WIRELESS ADHOC NETWORKS

2013 ◽  
Vol 5 (1) ◽  
pp. 29-34
Author(s):  
Nutakki Praveena ◽  
Dr. Ujwal A. Lanjewar ◽  
Chilakalapudi Meher Babu
Keyword(s):  
Resource Allocation ◽  
Control Strategies ◽  
A Priori ◽  
Satellite Networks ◽  
Available Bandwidth ◽  
Traffic Characteristics ◽  
Network Intrusion ◽  
Master Station ◽  
Wireless Adhoc Networks ◽  
Network Status

Control architecture for resource allocation in satellite networks is proposed, along with the specification of performance indexes and control strategies. The latter, besides being based on information on traffic statistics and network status, rely upon some knowledge of the fading conditions over the satellite network channels. The resource allocation problem consists of the assignment, by a master station, of a total available bandwidth among traffic earth stations in the presence of different traffic types. Traffic stations are assumed to measure continuously their signal fade level, but this information may either be used only locally or also communicated to the master station. According to the information made available on-line to the master station on the level of the fading attenuation of the traffic stations, the assignment can be made static, based on the a priori knowledge of long-term fading statistics, or dynamic, based on the updated measurements. In any case, the decisions can be adapted to slowly time-varying traffic characteristics. At each earth station, two basic traffic types are assumed to be present, namely guaranteed bandwidth, real-time, synchronous data (stream traffic), and best effort traffic (datagram traffic). Numerical results are provided for a specific architecture in the dynamic case, in a real environment, based on the Italian satellite national coverage payload characteristics.

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