scholarly journals The influence of sensory delay on the yaw dynamics of a flapping insect

2011 ◽  
Vol 9 (72) ◽  
pp. 1685-1696 ◽  
Author(s):  
Michael J. Elzinga ◽  
William B. Dickson ◽  
Michael H. Dickinson
Keyword(s):  
Feedback System ◽  
System Response ◽  
Feedback Gain ◽  
Free Flight ◽  
Closed Loop Systems ◽  
Tethered Flight ◽  
Body Dynamics ◽  
And Performance ◽  
Proportional Controller ◽  
Flight Measurements

In closed-loop systems, sensor feedback delays may have disastrous implications for performance and stability. Flies have evolved multiple specializations to reduce this latency, but the fastest feedback during flight involves a delay that is still significant on the timescale of body dynamics. We explored the effect of sensor delay on flight stability and performance for yaw turns using a dynamically scaled robotic model of the fruitfly, Drosophila . The robot was equipped with a real-time feedback system that performed active turns in response to measured torque about the functional yaw axis. We performed system response experiments for a proportional controller in yaw velocity for a range of feedback delays, similar in dimensionless timescale to those experienced by a fly. The results show a fundamental trade-off between sensor delay and permissible feedback gain, and suggest that fast mechanosensory feedback in flies, and most probably in other insects, provide a source of active damping which compliments that contributed by passive effects. Presented in the context of these findings, a control architecture whereby a haltere-mediated inner-loop proportional controller provides damping for slower visually mediated feedback is consistent with tethered-flight measurements, free-flight observations and engineering design principles.

Time-Accurate Simulation of Longitudinal Flight Mechanics with Control by CFD/RBD Coupling

2012 ◽  
Vol 226-228 ◽  
pp. 788-792 ◽  
Author(s):  
Dong Guo ◽  
Min Xu ◽  
Shi Lu Chen
Keyword(s):  
Computational Study ◽  
Rigid Motion ◽  
Rigid Body Dynamics ◽  
Flight Mechanics ◽  
Control Surface ◽  
Free Flight ◽  
Body Dynamics ◽  
Computational Fluid Dynamics Cfd ◽  
Coupled Solution ◽  
Surface Deflections

This paper describes a multidisciplinary computational study undertaken to compute the flight trajectories and simultaneously predict the unsteady free flight aerodynamics of aircraft in time domain using an advanced coupled computational fluid dynamics (CFD)/rigid body dynamics (RBD) technique. This incorporation of the flight mechanics equations and controller into the CFD solver loop and the treatment of the mesh, which must move with both the control surface deflections and the rigid motion of the aircraft, are illustrated. This work is a contribution to a wider effort towards the simulation of aeroelastic and flight stability in regions where nonlinear aerodynamics, and hence potentially CFD, can play a key role. Results demonstrating the coupled solution are presented.

STABILIZATION OF CHAOTIC SYSTEMS USING LINEAR SAMPLED-DATA CONTROLLER

2007 ◽  
Vol 17 (06) ◽  
pp. 2021-2031 ◽  
Author(s):  
H. K. LAM ◽  
F. H. F. LEUNG
Keyword(s):  
Chaotic System ◽  
Chaotic Systems ◽  
Lorenz System ◽  
Design Procedure ◽  
Sampling Period ◽  
Feedback Gain ◽  
Sampled Data ◽  
Lyapunov Approach ◽  
And Performance ◽  
Data Controller

This paper proposes a linear sampled-data controller for the stabilization of chaotic system. The system stabilization and performance issues will be investigated. Stability conditions will be derived based on the Lyapunov approach. The findings of the maximum sampling period and the feedback gain of controller, and the optimization of system performance will be formulated as a generalized eigenvalue minimization problem. Based on the analysis result, a stable linear sampled-data controller can be realized systematically to stabilize a chaotic system. An example of stabilizing a Lorenz system will be given to illustrate the design procedure and effectiveness of the proposed approach.

scholarly journals The Dynamic Response of Tuned Impact Absorbers for Rotating Flexible Structures

2005 ◽  
Vol 1 (1) ◽  
pp. 13-24 ◽  
Author(s):  
Steven W. Shaw ◽  
Christophe Pierre
Keyword(s):  
Dynamic Response ◽  
Flexible Structures ◽  
Experimental Studies ◽  
Analytical Investigation ◽  
Design Parameters ◽  
System Response ◽  
Rotor Speed ◽  
Flexible System ◽  
Restoring Forces ◽  
And Performance

This paper describes an analytical investigation of the dynamic response and performance of impact vibration absorbers fitted to flexible structures that are attached to a rotating hub. This work was motivated by experimental studies at NASA, which demonstrated the effectiveness of these types of absorbers for reducing resonant transverse vibrations in periodically excited rotating plates. Here we show how an idealized model can be used to describe the essential dynamics of these systems, and used to predict absorber performance. The absorbers use centrifugally induced restoring forces so that their nonimpacting dynamics are tuned to a given order of rotation, whereas their large amplitude dynamics involve impacts with the primary flexible system. The linearized, nonimpacting dynamics are first explored in detail, and it is shown that the response of the system has some rather unique features as the hub rotor speed is varied. A class of symmetric impacting motions is also analyzed and used to predict the effectiveness of the absorber when operating in its impacting mode. It is observed that two different types of grazing bifurcations take place as the rotor speed is varied through resonance, and their influence on absorber performance is described. The analytical results for the symmetric impacting motions are also used to generate curves that show how important absorber design parameters—including mass, coefficient of restitution, and tuning—affect the system response. These results provide a method for quickly evaluating and comparing proposed absorber designs.

Rheology of Adhesion

1972 ◽  
Vol 45 (6) ◽  
pp. 1604-1622 ◽  
Author(s):  
D. H. Kaelble
Keyword(s):  
Polymer Composites ◽  
Three Dimensional ◽  
Polymeric Materials ◽  
Intermolecular Forces ◽  
Adhesive Joints ◽  
Polymer Chains ◽  
System Response ◽  
Ample Evidence ◽  
Volume State ◽  
And Performance

Abstract This discussion has outlined a series of considerations which begin with engineering definitions of system response of adhesive joints and end with propositions involving molecular interactions at interfaces. Connecting these extreme aspects of the argument is the central subject of the micromechanics of bonding and fracture. Cavitation theory, as simply described by Equations (6a) and (7), illustrates the scale of microresponse in which both the thermodynamic and rheological aspects of adhesion phenomena achieve a parity when applied to cavities of radius r=0.1 to 10 μ. The discussion of the micromechanics of polymer fracture provides ample evidence that pure materials, polymer composites, and adhesive joints, need to be described in terms of their microdefects. The several mathematical models for crack propagation which are imposed upon fracture mechanics data tend to oversimplify the visualization of the true micromechanisms of fracture. The fuller development of micromechanics theory and experimental analysis promises to be an important area of current developments in the better understanding of macroscopic response of filled systems, fiber reinforced composites, and adhesively bonded structures. Recent developments in the several theories of intermolecular forces and the physical chemistry of bonding provide new impetus to the chemist to design optimized polymeric materials with finely adjusted balances of surface and bulk properties. The fuller visualization of adsorption-interdiffusion bonding as a process involving both the two-dimensional interface and the three-dimensional interphase defines bonding as both a thermodynamical and a rheological process. The microstages of bond formation are somewhat the reverse of the stages of microfracture listed earlier. The microdefects that commonly exist in polymeric materials and polymer composites tend to indicate that the viscoelastic constraints typical of polymer chains and networks play an important role in preventing equilibrium bonding in the simple thermodynamic sense as expressed by idealized liquid—liquid or liquid—solid interactions. The current development and application of a refined thermodynamical and rheological argument to both bonding and fracture processes stands as a central issue in directly correlating the molecular criteria of adhesion and performance of bonded systems. Any of the simple mathematical relations introduced in this discussion may be expressed with greater detail and precision by incorporating detailed statements concerning chemical composition, macromolecular structure, and free volume state of the polymeric adhesive.

scholarly journals Rapid visuomotor feedback gains are tuned to the task dynamics

2017 ◽  
Vol 118 (5) ◽  
pp. 2711-2726 ◽  
Author(s):  
Sae Franklin ◽  
Daniel M. Wolpert ◽  
David W. Franklin
Keyword(s):  
Control System ◽  
Force Field ◽  
Feedback System ◽  
Sensorimotor Control ◽  
Motor Memory ◽  
Feedback Gain ◽  
Adaptation Process ◽  
Fourfold Increase ◽  
Lateral Resistance ◽  
Left And Right

Adaptation to novel dynamics requires learning a motor memory, or a new pattern of predictive feedforward motor commands. Recently, we demonstrated the upregulation of rapid visuomotor feedback gains early in curl force field learning, which decrease once a predictive motor memory is learned. However, even after learning is complete, these feedback gains are higher than those observed in the null field trials. Interestingly, these upregulated feedback gains in the curl field were not observed in a constant force field. Therefore, we suggest that adaptation also involves selectively tuning the feedback sensitivity of the sensorimotor control system to the environment. Here, we test this hypothesis by measuring the rapid visuomotor feedback gains after subjects adapt to a variety of novel dynamics generated by a robotic manipulandum in three experiments. To probe the feedback gains, we measured the magnitude of the motor response to rapid shifts in the visual location of the hand during reaching. While the feedback gain magnitude remained similar over a larger than a fourfold increase in constant background load, the feedback gains scaled with increasing lateral resistance and increasing instability. The third experiment demonstrated that the feedback gains could also be independently tuned to perturbations to the left and right, depending on the lateral resistance, demonstrating the fractionation of feedback gains to environmental dynamics. Our results show that the sensorimotor control system regulates the gain of the feedback system as part of the adaptation process to novel dynamics, appropriately tuning them to the environment. NEW & NOTEWORTHY Here, we test whether rapid visuomotor feedback responses are selectively tuned to the task dynamics. The responses do not exhibit gain scaling, but they do vary with the level and stability of task dynamics. Moreover, these feedback gains are independently tuned to perturbations to the left and right, depending on these dynamics. Our results demonstrate that the sensorimotor control system regulates the feedback gain as part of the adaptation process, tuning them appropriately to the environment.

An Insect Tether System Using Magnetic Levitation: Development, Analysis and Feedback Control

2016 ◽  
Author(s):  
Shih-Jung Hsu ◽  
Yagız Efe Bayiz ◽  
Pan Liu ◽  
Bo Cheng
Keyword(s):  
System Identification ◽  
Feedback Control ◽  
Flight Control ◽  
Insect Flight ◽  
Magnetic Levitation ◽  
Body Movement ◽  
Whole Body ◽  
Free Flight ◽  
Tethered Flight ◽  
Development Analysis

Insect flight has gained wide interests in both biology and engineering communities in the past decades regarding its aerodynamics, sensing and flight control. However, studying insect flight experimentally remains a challenge in both free-flight and tethered-flight settings. In free flight experiments, due to highly unpredictable and fast flight behavior of flying insects, it is difficult to apply controlled sensory inputs to their flight system for system identification and modeling analyses. In tethered flight experiments, constrained whole body movement results in silenced proprioceptive feedback therefore breaks the flight control loop and does not reveal any flight dynamics. Therefore, this work aims to develop a novel insect tether system using magnetic levitation. Such a system magnetically fixes an insect in space but allows it to rotate freely about yaw axis with minimal interference from mechanical constraints. This paper presents the development, analysis and feedback control of this system and finally test its performance using a hawkmoth (Manduca Sexta). In addition, a system identification of the magnetic levitation system and detailed analysis in closed-loop stability and performance are provided. In the future, the insect tether system will be applied to study the insect flight aerodynamics, sensing and control.

Modeling and Simulation of Stochastic Lorenz Systems by Polynomial Chaos Approach

2007 ◽  
Author(s):  
Lin Li ◽  
Corina Sandu
Keyword(s):  
Polynomial Chaos ◽  
Initial Conditions ◽  
Nonlinear Problems ◽  
System Response ◽  
Structural Vibrations ◽  
System Parameters ◽  
Highly Nonlinear ◽  
Body Dynamics ◽  
The Lorenz System ◽  
Multi Body

The Lorenz problem is one of the paradigms of the chaotic systems, which are sensitive to initial conditions and for which the performance is hard to predict. However, in many cases and dynamic systems, the initial conditions of a dynamic system and the system parameters can’t be measured accurately, and the response of the system must indeed be explored in advance. In this study, the polynomial chaos approach is used to handle uncertain initial conditions and system parameters of the Lorenz system. The method has been successfully applied by the authors and co-workers in multi-body dynamics and terrain profile and soil modeling. Other published studies illustrate the benefits of using the polynomial chaos, especially for problems involving large uncertainties and highly nonlinear problems in fluid mechanics, structural vibrations, and air quality studies. This study is an attempt to use the polynomial chaos approach to treat the Lorenz problem, and the results are compared with a classical Monte Carlo approach. Error bars are used to illustrate the standard deviation of the system response. Different meshing schemes are simulated, and the convergence of the method is analyzed.

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