scholarly journals Examining modifications of execution strategies during a continuous task

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Erez James Cohen ◽  
Kunlin Wei ◽  
Diego Minciacchi
Keyword(s):  
Motor Control ◽  
Initial State ◽  
Short Timescale ◽  
Initial Location ◽  
Control Knowledge ◽  
Solution Manifold ◽  
A Performance

AbstractHow strategies are formulated during a performance is an important aspect of motor control. Knowledge of the strategy employed in a task may help subjects achieve better performances, as it would help to evidence other possible strategies that could be used as well as help perfect a certain strategy. We sought to investigate how much of a performance is conditioned by the initial state and whether behavior throughout the performance is modified within a short timescale. In other words, we focus on the process of execution and not on the outcome. To this scope we used a repeated continuous circle tracing task. Performances were decomposed into different components (i.e., execution variables) whose combination is able to numerically determine movement outcome. By identifying execution variables of speed and duration, we created an execution space and a solution manifold (i.e., combinations of execution variables yielding zero discrepancy from the desired outcome) and divided the subjects according to their initial performance in that space into speed preference, duration preference, and no-preference groups. We demonstrated that specific strategies may be identified in a continuous task, and strategies remain relatively stable throughout the performance. Moreover, as performances remained stable, the initial location in the execution space can be used to determine the subject’s strategy. Finally, contrary to other studies, we demonstrated that, in a continuous task, performances were associated with reduced exploration of the execution space.

scholarly journals Parametric optimization of a neutral system with two delays and PD-controller

2013 ◽  
Vol 23 (2) ◽  
pp. 131-143 ◽  
Author(s):  
Józef Duda
Keyword(s):  
Performance Index ◽  
Lyapunov Functional ◽  
Parametric Optimization ◽  
Neutral Type ◽  
Neutral System ◽  
Pd Controller ◽  
Initial State ◽  
Two Delays ◽  
Index Value ◽  
A Performance

In this paper a parametric optimization problem for a linear neutral system with two delays with an integral quadratic performance index is formulated and solved. The method of computing of a performance index value bases on determining of a Lyapunov functional defined on a state space such that its value for an initial state is equal to a performance index value. In the paper a form of a Lyapunov functional is assumed and a method of computing its coefficients is given. An example illustrating the application of discussed theory is presented. It concerns the system with a PD-controller designed to control a plant with two delays both retarded and neutral type. For such system a value of considered performance index is determined.

scholarly journals A Cyclogenesis Evolving into Two Distinct Scenarios and Its Implications for Short-Term Ensemble Forecasting

2005 ◽  
Vol 133 (7) ◽  
pp. 2016-2029 ◽  
Author(s):  
Matthieu Plu ◽  
Philippe Arbogast
Keyword(s):  
Monte Carlo ◽  
Error Bounds ◽  
Coherent Structures ◽  
Singular Vector ◽  
Initial Conditions ◽  
Low Cost ◽  
Bimodal Distribution ◽  
Initial State ◽  
Position Errors ◽  
Initial Location

Abstract In a nonlinear quasigeostrophic model with uniform potential vorticity, an idealized initial state sharing some features with atmospheric low-predictability situations is built. Inspired by previous work on idealized cyclogenesis, two different cyclogenesis scenarios are obtained as a result of a small change of the initial location of one structure. This behavior is interpreted by analyzing the baroclinic interaction between upper- and lower-level anomalies. The error growth mechanism is nonlinear; it does not depend on the linear stability properties of the jet, which are the same in both evolutions. The ability of ensemble forecasts to capture these two possible evolutions is then assessed given some realistic error bounds in the knowledge of the initial conditions. First, a reference statistical distribution of each of the evolutions is obtained by means of a large Monte Carlo ensemble. Smaller ensembles with size representative of what is available in current operational implementations are then built and compared to the Monte Carlo reference: several singular-vector-based ensembles, a small Monte Carlo ensemble, and a “coherent structure”-based ensemble. This new technique relies on a sampling of the errors on the precursors of the cyclogenesis: amplitude and position errors. In this context, the precursors are handled as coherent structures that may be amplified or moved within realistic error bounds. It is shown that the singular vector ensemble fails to reproduce the bimodal distribution of the variability if the ensemble is not initially constrained, whereas it is accessible at a relatively low cost to the new coherent structures initialization.

scholarly journals Purely Declarative Action Descriptions are Overrated: Classical Planning with Simulators

2017 ◽  
Author(s):  
Guillem Francès ◽  
Miquel Ramírez ◽  
Nir Lipovetzky ◽  
Hector Geffner
Keyword(s):  
State Of The Art ◽  
Black Box ◽  
Initial State ◽  
Planning Algorithms ◽  
Control Knowledge ◽  
Domain Independent ◽  
Action Structure

Classical planning is concerned with problems where a goal needs to be reached from a known initial state by doing actions with deterministic, known effects. Classical planners, however, deal only with classical problems that can be expressed in declarative planning languages such as STRIPS or PDDL. This prevents their use on problems that are not easy to model declaratively or whose dynamics are given via simulations. Simulators do not provide a declarative representation of actions, but simply return successor states. The question we address in this paper is: can a planner that has access to the structure of states and goals only, approach the performance of planners that also have access to the structure of actions expressed in PDDL? To answer this, we develop domain-independent, black box planning algorithms that completely ignore action structure, and show that they match the performance of state-of-the-art classical planners on the standard planning benchmarks. Effective black box algorithms open up new possibilities for modeling and for expressing control knowledge, which we also illustrate.

scholarly journals Dynamical Motor Control Learned with Deep Deterministic Policy Gradient

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Haibo Shi ◽  
Yaoru Sun ◽  
Jie Li
Keyword(s):  
Dynamical System ◽  
Motor Control ◽  
Neural Coding ◽  
Control Policy ◽  
Neural Mechanism ◽  
Spatial Filter ◽  
Initial State ◽  
Motor Network ◽  
Control Command ◽  
Policy Gradient

Conventional models of motor control exploit the spatial representation of the controlled system to generate control commands. Typically, the control command is gained with the feedback state of a specific instant in time, which behaves like an optimal regulator or spatial filter to the feedback state. Yet, recent neuroscience studies found that the motor network may constitute an autonomous dynamical system and the temporal patterns of the control command can be contained in the dynamics of the motor network, that is, the dynamical system hypothesis (DSH). Inspired by these findings, here we propose a computational model that incorporates this neural mechanism, in which the control command could be unfolded from a dynamical controller whose initial state is specified with the task parameters. The model is trained in a trial-and-error manner in the framework of deep deterministic policy gradient (DDPG). The experimental results show that the dynamical controller successfully learns the control policy for arm reaching movements, while the analysis of the internal activities of the dynamical controller provides the computational evidence to the DSH of the neural coding in motor cortices.

Tensile Failure of 55-Nitinol Wire

1975 ◽  
Vol 33 ◽  
pp. 46-47
Author(s):  
F. I. Grace
Keyword(s):  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Stoichiometric Composition ◽  
Tensile Failure ◽  
Initial State ◽  
Initial Shape ◽  
Nitinol Wire ◽  
Cscl Type ◽  
Shear Transformation

An interest in NiTi alloys with near stoichiometric composition (55 NiTi) has intensified since they were found to exhibit a unique mechanical shape memory effect at the Naval Ordnance Laboratory some twelve years ago (thus refered to as NITINOL alloys). Since then, the microstructural mechanisms associated with the shape memory effect have been investigated and several interesting engineering applications have appeared.The shape memory effect implies that the alloy deformed from an initial shape will spontaneously return to that initial state upon heating. This behavior is reported to be related to a diffusionless shear transformation which takes place between similar but slightly different CsCl type structures.

Physiologic Studies Provide New Perspectives on Early Speech Development

2010 ◽  
Vol 20 (2) ◽  
pp. 29-36
Author(s):  
Erin M. Wilson ◽  
Ignatius S. B. Nip
Keyword(s):  
Motor Control ◽  
Motor Development ◽  
Motion Tracking ◽  
Speech Development ◽  
Speech Motor Control ◽  
Therapeutic Approaches ◽  
Facial Motion ◽  
Disordered Speech ◽  
Speech Motor ◽  
Physiologic Data

Abstract Although certain speech development milestones are readily observable, the developmental course of speech motor control is largely unknown. However, recent advances in facial motion tracking systems have been used to investigate articulator movements in children and the findings from these studies are being used to further our understanding of the physiologic basis of typical and disordered speech development. Physiologic work has revealed that the emergence of speech is highly dependent on the lack of flexibility in the early oromotor system. It also has been determined that the progression of speech motor development is non-linear, a finding that has motivated researchers to investigate how variables such as oromotor control, cognition, and linguistic factors affect speech development in the form of catalysts and constraints. Physiologic data are also being used to determine if non-speech oromotor behaviors play a role in the development of speech. This improved understanding of the physiology underlying speech, as well as the factors influencing its progression, helps inform our understanding of speech motor control in children with disordered speech and provide a framework for theory-driven therapeutic approaches to treatment.

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