scholarly journals Sprawl Angle in Simplified Models of Vertical Climbing: Implications for Robots and Roaches

2011 ◽  
Vol 8 (3-4) ◽  
pp. 441-452 ◽  
Author(s):  
Goran A. Lynch ◽  
Lawrence Rome ◽  
Daniel E. Koditschek
Keyword(s):  
Open Loop ◽  
Physical Models ◽  
Stride Frequency ◽  
Mass Center ◽  
Electromechanical Actuators ◽  
Lateral Forces ◽  
Potential Benefits ◽  
The Stability ◽  
New Hypothesis ◽  
Operating Regimes

Empirical data taken from fast climbing sprawled posture animals reveals the presence of strong lateral forces with significant pendulous swaying of the mass center trajectory in a manner captured by a recently proposed dynamical template [1, 2]. In this simulation study we explore the potential benefits of pendulous dynamical climbing in animals and in robots by examining the stability and power advantages of variously more and less sprawled limb morphologies when driven by conventional motors in contrast with animal-like muscles. For open loop models of gait generation inspired by the neural-deprived regimes of high stride-frequency animal climbing, our results corroborate earlier hypotheses that sprawled posture may be required for stability. For quadratic-in-velocity power output actuation models typical of commercially available electromechanical actuators, our results suggest the new hypothesis that sprawled posture may confer significant energetic advantage. In notable contrast, muscle-powered climbers do not experience an energetic benefit from sprawled posture due to their sufficiently distinct actuator characteristics and operating regimes. These results suggest that the potentially significant benefits of sprawled posture climbing may be distinctly different depending upon the details of the climbers sensorimotor endowment. They offer a cautionary instance against mere copying of biology by engineers or rote study of physical models by biologists through this reminder of how even simple questions addressed by simple models can yield nuanced answers that only begin to hint at the complexity of biological designs and behaviors.

scholarly journals Data-Driven Stability Assessment of Multilayer Long Short-Term Memory Networks

2021 ◽  
Vol 11 (4) ◽  
pp. 1829
Author(s):  
Davide Grande ◽  
Catherine A. Harris ◽  
Giles Thomas ◽  
Enrico Anderlini
Keyword(s):  
Neural Network ◽  
Network Architecture ◽  
Short Term Memory ◽  
Moving Average ◽  
Machine Learning Algorithms ◽  
Physical Models ◽  
Data Driven ◽  
The Stability ◽  
And Control ◽  
Nonlinear Autoregressive

Recurrent Neural Networks (RNNs) are increasingly being used for model identification, forecasting and control. When identifying physical models with unknown mathematical knowledge of the system, Nonlinear AutoRegressive models with eXogenous inputs (NARX) or Nonlinear AutoRegressive Moving-Average models with eXogenous inputs (NARMAX) methods are typically used. In the context of data-driven control, machine learning algorithms are proven to have comparable performances to advanced control techniques, but lack the properties of the traditional stability theory. This paper illustrates a method to prove a posteriori the stability of a generic neural network, showing its application to the state-of-the-art RNN architecture. The presented method relies on identifying the poles associated with the network designed starting from the input/output data. Providing a framework to guarantee the stability of any neural network architecture combined with the generalisability properties and applicability to different fields can significantly broaden their use in dynamic systems modelling and control.

Attention Theory and Training Research

1987 ◽  
Vol 31 (6) ◽  
pp. 648-651 ◽  
Author(s):  
James G. Connelly ◽  
Christopher D. Wickens ◽  
Gavan Lintern ◽  
Kelly Harwood
Keyword(s):  
Mental Workload ◽  
Open Loop ◽  
Flight Simulation ◽  
Complex Task ◽  
Time Sharing ◽  
Attention Theory ◽  
Stimulus Response ◽  
Training Research ◽  
Complex Training ◽  
The Stability

This study used elements of attention theory as a methodological basis to decompose a complex training task in order to improve training efficiency. The complex task was a microcomputer flight simulation where subjects were required to control the stability of their own helicopter while acquiring and engaging enemy helicopters in a threat environment. Subjects were divided into whole-task, part-task, and part/open loop adaptive task groups in a transfer of training paradigm. The effect of reducing mental workload at the early stages of learning was examined with respect to the degree that subordinate elements of the complex task could be automated through practice of consistent, learnable stimulus-response relationships. Results revealed trends suggesting the benefit of isolating consistently mapped sub-tasks for part-task training and the presence of a time-sharing skill over and above the skill required for the separate subtasks.

Open Loop Stability on Hybrid Synchronous Motor

2010 ◽  
Vol 121-122 ◽  
pp. 860-865
Author(s):  
Xue Zhen Chen
Keyword(s):  
Permanent Magnet ◽  
Harmonic Distortion ◽  
Synchronous Motor ◽  
Open Loop ◽  
Mathematics Model ◽  
Distortion Factor ◽  
Part D ◽  
Fraction Length ◽  
The Stability ◽  
Loop Stability

This paper searched open loop stability on hybrid synchronous motor which is made of a permanent magnet part and a reluctance part, there is important influence for the ratio k, the fraction length of the permanent magnet part, and the displaced angle α, the between the two part d-axis, the small-signal mathematics model was derived based on d-q reference frame, and optimized the appropriate k and α value considering the stability and the harmonic distortion factor (THD), The simulation results show that the model is correct.

scholarly journals Road train motion stability in BRT system

2019 ◽  
Vol 254 ◽  
pp. 03007 ◽  
Author(s):  
Vladimir Sakhno ◽  
Juraj Gerlici ◽  
Viktor Poliakov ◽  
Alexandr Kravchenko ◽  
Oleg Omelnitcky ◽  
...  
Keyword(s):  
Critical Speed ◽  
Motor Vehicles ◽  
Mass Center ◽  
Passenger Transportation ◽  
Wheel Drive ◽  
Main Index ◽  
Rapid Transport ◽  
The Stability ◽  
The City ◽  
Potential Stability

The peculiarities of organization and perspectives of mass passenger transportation in the city and beyond are considered with the use of "Bus Rapid Transport" (BRT) or Metrobus. Different aspects of study of motor vehicles (MV) controllability and stability are analyzed. It is substantiated that it is sufficient to consider the potential stability of the MV itself, in order to guarantee the stability of the "driver MV" system with a large reserve. A mathematical model of a three-axle bus train consisting of a bus and two trains (metrobus) is developed and the factors influencing the critical speed as the main index of the stability of its movement are determined. It is established that the increase of the critical speed of the metrobus can be achieved by increasing the base of the bus, the first and the second trailer, as well as the mass of the bus and the coefficients of resistance of the drive wheels of the bus driving axle and the trailers axles. At the same time, increasing the distance from the mass center to the bus rear axle, increasing the distance from the mass center to the point of the coupling of the bus with the first trailer, increasing the mass of trailers and the resistance of the resistance of the wheel drive of the bus axis lead to a decrease in the critical speed of the metrobus. This must be taken into account both when designing metrobuses, and when operating them.

An insect-scale robot reveals the effects of different body dynamics regimes during open-loop running in feature-laden terrain

2021 ◽  
Author(s):  
Perrin Elizabeth Schiebel ◽  
Jennifer Shum ◽  
Henry Cerbone ◽  
Robert J Wood
Keyword(s):  
Input Power ◽  
Open Loop ◽  
Stride Frequency ◽  
Robot Dynamics ◽  
Natural Environments ◽  
Heterogeneous Environments ◽  
Cost Of Transport ◽  
Transmission Resonance ◽  
Loop Control ◽  
Terrain Features

Abstract The transition from the lab to natural environments is an archetypal challenge in robotics. While larger robots can manage complex limb-ground interactions using sensing and control, such strategies are difficult to implement on small platforms where space and power are limited. The Harvard Ambulatory Microrobot (HAMR) is an insect-scale quadruped capable of effective open-loop running on featureless, hard substrates. Inspired by the predominantly feedforward strategy of rapidly-running cockroaches on uneven terrain [Sponberg, 2007], we used HAMR to explore open-loop running on two 3D printed heterogeneous terrains generated using fractional Brownian motion. The ``pocked'' terrain had foot-scale features throughout while the ``jagged'' terrain features increased in height in the direction of travel. We measured the performance of trot and pronk gaits while varying limb amplitude and stride frequency. The frequencies tested encompassed different dynamics regimes: body resonance (10-25~Hz) and kinematic running (30-40~Hz), with dynamics typical of biological running and walking, respectively, and limb-transmission resonance (45-60~Hz). On the featureless and pocked terrains, low mechanical cost-of-transport (mCoT) kinematic running combinations performed best without systematic differences between trot and pronk; indicating that if terrain features are not too tall, a robot can transition from homo- to heterogeneous environments in open-loop. Pronk bypassed taller features than trot on the jagged terrain, and higher mCoT, lower frequency running was more often effective. While increasing input power to the robot improved performance in general, lower frequency pronking on jagged terrain allowed the robot to bypass taller features compared with the same input power at higher frequencies. This was correlated with the increased variation in center-of-mass orientation occurring at frequencies near body resonance. This study established that appropriate choice of robot dynamics, as mediated by gait, frequency, and limb amplitude, can expand the terrains accessible to microrobots without the addition of sensing or closed-loop control.

scholarly journals Modeling and Stability Analysis of Parallel Inverters in Island Microgrid

Electronics ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 463 ◽  
Author(s):  
Xiaohuan Wang ◽  
Hongyang Qing ◽  
Peng Huang ◽  
Chunjiang Zhang
Keyword(s):  
Parallel System ◽  
Open Loop ◽  
Power Equipment ◽  
Control Methods ◽  
Impedance Model ◽  
Loop Transfer Function ◽  
Impedance Modeling ◽  
The Difference ◽  
Output Characteristics ◽  
The Stability

The island microgrid is composed of a large number of inverters and various types of power equipment, and the interaction between inverters with different control methods may cause system instability, which will cause the power equipment to malfunction. Therefore, effective methods for analyzing the stability of the microgrid system have become particularly important. Generally, impedance modeling methods are used to analyze the stability of power electronic converter systems. In this paper, the impedance models of a PQ-controlled inverter and droop-controlled inverter are established in d-q frame. In view of the difference of output characteristics between the two control methods, the island microgrid is equivalent to a double closed-loop system. The impedance model of the parallel system is derived and the open loop transfer function of the system is extracted. Based on the generalized Nyquist criterion (GNC), the stability of parallel system working in island microgrid mode is analyzed using this proposed impedance model. The simulation and experiment results are presented to verify the analysis.

Friction-Induced Dynamics of Axially-Moving Media in Contact With an Actively-Positioned Surface

2008 ◽  
Author(s):  
V. Kartik ◽  
Evangelos Eleftheriou
Keyword(s):  
Data Storage ◽  
Surface Friction ◽  
Design Parameters ◽  
Moving Medium ◽  
Critical Design ◽  
Flexible Material ◽  
Potential Benefits ◽  
Axially Moving ◽  
The Stability ◽  
Moving Media

The dynamics of an axially-moving flexible medium are examined in the context of an application where the medium is partially supported by a frictional surface, that actively-orients itself relative to the direction of transport. The stability and motion of the medium are of interest in a magnetic tape data storage application where the orientation of a sensing surface is continuously altered in order to ‘follow’ the medium’s motion. Moving media that are in contact with such guiding surfaces experience friction excitations induced by the relative motion in addition to what is observed with a stationary guiding surface. Friction-induced bending moments, as well as tension fluctuation beyond the permissible limits for the flexible material can erode the potential benefits of such active positioning. This paper describes some of these dynamic phenomena using the simplified example of a planar guiding surface whose orientation is dynamically altered relative to the moving medium. A physical model for the friction-induced excitation of the moving medium is developed, and the dynamics are analyzed for their effect on critical design parameters such as the achievable bandwidth of the active control algorithm, as well as with respect to constraints on the geometry and positioning of the guiding surface.

Analysis of the Idling Start of the Moving Coil Linear Compressor

2008 ◽  
Author(s):  
Yingbai Xie ◽  
Xiuzhi Huang ◽  
Liyong Lun ◽  
Ganglei Sun
Keyword(s):  
Closed Loop ◽  
Transfer Functions ◽  
Load Condition ◽  
Open Loop ◽  
Reciprocating Compressor ◽  
Piston Motion ◽  
Linear Compressor ◽  
Simulation Results ◽  
The Stability ◽  
Stability Time

The linear compressor is driven by a linear motor. Because it has no crankcase, the piston motion and its control of the linear compressor are differing from that of the conventional reciprocating compressor. For a moving coil linear compressor, mechanical and electromagnetism system are modeled. The open loop and closed loop transfer functions of the system in no-load condition are obtained derived from these equations. The Matlab software is applied to analyze the stability, time domain and frequency domain of the system. Simulation results show that the linear compressor is stable, but the overshoot is relative high, which must be adjusted. This conclusion will be benefit for the design of the idling start of the moving coil linear compressor.

A Train Operations and Energy Simulator Model of the Steered Frame Truck

2009 ◽  
Author(s):  
John P. Wachsmuth ◽  
G. Walter Rosenberger ◽  
Robert W. Blank
Keyword(s):  
Fuel Consumption ◽  
Average Velocity ◽  
Rolling Resistance ◽  
Considerable Reduction ◽  
Lateral Forces ◽  
Train Operation ◽  
Potential Benefits ◽  
Air Brakes

A Train Operation and Energy Simulator (TOES™) model was created in order to investigate the potential benefits of replacing three-piece trucks with the “Steered Frame Truck” currently under development. Loaded coal trains were simulated with three-piece trucks and with Steered Frame Trucks. Both trains were modeled traveling on Norfolk Southern’s Pocahontas division from MP V435 to V399. The consist and direction of travel are based on actual trains in service. It was found that the model predicts several benefits for replacing three-piece trucks with Steered Frame Trucks. These resulted from the Steered Frame Truck having a greatly reduced rolling resistance while traveling around a curve. The benefits were found to include: a significant reduction in fuel consumption, a reduction in in-train forces, and a small increase in average velocity. One drawback was also predicted: that the reduced rolling resistance would necessitate the increased use of air brakes while traveling down-hill. Although Steered Frame Trucks should produce a considerable reduction in lateral forces, modeling such a reduction was beyond the scope of this work. Similarly, modeling other potential benefits not directly derived from the Steered Frame Truck’s reduced rolling resistance was not considered here.

Plasma spray process modelling using artificial neural networks: Application to Al2O3-TiO2 (13% by weight) ceramic coating structure

2004 ◽  
Vol 120 ◽  
pp. 363-370
Author(s):  
S. Guessasma ◽  
G. Montavon ◽  
C. Coddet
Keyword(s):  
Thermal Spraying ◽  
Processing Parameters ◽  
Ceramic Coatings ◽  
Physical Models ◽  
Spray Process ◽  
Artificial Neural ◽  
Artificial Neural Network Ann ◽  
The Stability ◽  
Experimental Values ◽  
Physical Phenomena

Thermal spraying is a versatile technique of coating manufacturing implementing large variety of materials and processes. The manufacture control is constrained by the understanding of the physical phenomena occurring during the spraying. It is however penalized by the large number of processing parameters (up to 50), their interdependencies, their correlations with the coating attributes and the stability of the process. Numerous statistical, heuristic or physical models intended to response to these constrains, very often partially because considering some aspects of the process. This work aims at considering a more global approach based on a powerful statistical methodology using artificial intelligence. Following this approach, the physical phenomena are encoded in a structure called Artificial Neural Network (ANN). An application of the ANN methodology is discussed in the case of the APS spray process. Some processing parameters categories are related to some coating properties for alumina-titania (13% by weight) ceramic coatings. ANN optimization is presented and discussed. Predicted results show globally a well agreement with the experimental values. Some conclusions point out the advantages of the ANN on the conventional methods, such as the design of experiments, used usually to recognize the controlling factors in a process.

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