scholarly journals Design and Optimal Control of a Multistable, Cooperative Microactuator

Actuators ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 183
Author(s):  
Michael Olbrich ◽  
Arwed Schütz ◽  
Tamara Bechtold ◽  
Christoph Ament
Keyword(s):  
Deflection Angle ◽  
Initial State ◽  
New Concepts ◽  
Vertical Displacements ◽  
State Uncertainty ◽  
Stable Equilibria ◽  
Freely Moving ◽  
Time And Energy ◽  
Multiple Stable Equilibria ◽  
Optimal Trajectory Planning

In order to satisfy the demand for the high functionality of future microdevices, research on new concepts for multistable microactuators with enlarged working ranges becomes increasingly important. A challenge for the design of such actuators lies in overcoming the mechanical connections of the moved object, which limit its deflection angle or traveling distance. Although numerous approaches have already been proposed to solve this issue, only a few have considered multiple asymptotically stable resting positions. In order to fill this gap, we present a microactuator that allows large vertical displacements of a freely moving permanent magnet on a millimeter-scale. Multiple stable equilibria are generated at predefined positions by superimposing permanent magnetic fields, thus removing the need for constant energy input. In order to achieve fast object movements with low solenoid currents, we apply a combination of piezoelectric and electromagnetic actuation, which work as cooperative manipulators. Optimal trajectory planning and flatness-based control ensure time- and energy-efficient motion while being able to compensate for disturbances. We demonstrate the advantage of the proposed actuator in terms of its expandability and show the effectiveness of the controller with regard to the initial state uncertainty.

Dynamic Response of Dielectric Elastomers

2004 ◽  
Author(s):  
Eric M. Mockensturm ◽  
Nakhiah Goulbourne
Keyword(s):  
Large Deformations ◽  
Electrical Energy ◽  
Material Behavior ◽  
Dielectric Elastomers ◽  
Large Strains ◽  
Inertial Effects ◽  
Stable Equilibria ◽  
Electrostatic Pressure ◽  
Linear Material ◽  
Multiple Stable Equilibria

Dielectric elastomers have received a great deal of attention recently for effectively transforming electrical energy to mechanical work. Their large strains and conformability make them enticing materials for many new types of actuators. Unfortunately, their non-linear material behavior and large deformations make actual devices difficult to model. However, the reason for this difficulty can also be used to design actuators that utilize these material and geometric non-linearities to obtain multiple stable equilibria. In this work, we investigate one of the simplest possible configurations, a spherical membrane, using a model that incorporates both mechanical and electrostatic pressure as well as inertial effects that become important when transitioning from one equilibrium to another.

Chaebol and Catastrophe: A New View of the Korean Business Groups and Their Role in the Financial Crisis

2002 ◽  
Vol 1 (2) ◽  
pp. 1-45 ◽  
Author(s):  
Robert C. Feenstra ◽  
Gary G. Hamilton ◽  
Eun Mie Lim
Keyword(s):  
Industrial Organization ◽  
Business Groups ◽  
High Concentration ◽  
Low Concentration ◽  
Korean Economy ◽  
Vertical Linkages ◽  
Stable Equilibria ◽  
Second Tier ◽  
The Government ◽  
Multiple Stable Equilibria

We present a model of industrial organization that has multiple stable equilibria and argue that the high-concentration equilibrium describes Korea's economy and the low-concentration equilibrium describes Taiwan's economy. Past industrial policy of the state may have put Korea's economy in the high-concentration equilibrium, but discontinuation of the policy did not cause the industrial organization to change because this is an economically viable equilibrium. The high-concentration equilibrium produces a narrower range of final goods than the low-concentration equilibrium, which explains why the 1996 collapse in semiconductor prices caused the less diversified Korean economy to contract more than the more diversified Taiwanese economy. More importantly, this collapse in demand caused Korea's economy to move to a new equilibrium that has a smaller number of business groups, as evidenced by the collapse of the second-tier chaebol and their absorption into the first-tier chaebol. This wave of bankruptcies, combined with the financially precarious state of the merchant banks, created an investor panic that precipitated the crisis, which began with the 17 November 1997 devaluation of the won. This is why economic fundamentals could explain the chaebol bankruptcies before that date and not those after that date. The logic of our model suggests that public policy should focus on reducing the vertical linkages within business groups and not on reducing their horizontal linkages as the current “Big Deal” program of the government is doing.

scholarly journals Implicit Coordination Using FOND Planning

2020 ◽  
Vol 34 (05) ◽  
pp. 7151-7159
Author(s):  
Thorsten Engesser ◽  
Tim Miller
Keyword(s):  
Computational Complexity ◽  
The Other ◽  
Path Finding ◽  
Initial State ◽  
Arbitrary Initial State ◽  
State Uncertainty ◽  
Multi Agent ◽  
Decidable Fragment ◽  
Implicit Coordination

Epistemic planning can be used to achieve implicit coordination in cooperative multi-agent settings where knowledge and capabilities are distributed between the agents. In these scenarios, agents plan and act on their own without having to agree on a common plan or protocol beforehand. However, epistemic planning is undecidable in general. In this paper, we show how implicit coordination can be achieved in a simpler, propositional setting by using nondeterminism as a means to allow the agents to take the other agents' perspectives. We identify a decidable fragment of epistemic planning that allows for arbitrary initial state uncertainty and non-determinism, but where actions can never increase the uncertainty of the agents. We show that in this fragment, planning for implicit coordination can be reduced to a version of fully observable nondeterministic (FOND) planning and that it thus has the same computational complexity as FOND planning. We provide a small case study, modeling the problem of multi-agent path finding with destination uncertainty in FOND, to show that our approach can be successfully applied in practice.

scholarly journals Pleiotropy as a factor maintaining genetic variation in quantitative characters under stabilizing selection

1996 ◽  
Vol 68 (1) ◽  
pp. 65-73 ◽  
Author(s):  
A. Gimelfarb
Keyword(s):  
Allelic Frequency ◽  
Direct Selection ◽  
Stabilizing Selection ◽  
Major Locus ◽  
Relative Contribution ◽  
Linkage Disequilibria ◽  
Wide Range ◽  
Stable Equilibria ◽  
A Minor ◽  
Multiple Stable Equilibria

SummaryA model of pleiotropy with N diallelic loci contributing additively to N quantitative traits and stabilizing selection acting on each of the traits is considered. Every locus has a major contribution to one trait and a minor contribution to the rest of them, while every trait is controlled by one major locus and N−1 minor loci. It is demonstrated that a stable equilibrium with the allelic frequency equal to 0·5 in all N loci can be maintained in such a model for a wide range of parameters. Such a ‘totally polymorphic’ equilibrium is maintained for practically any strength of selection and any recombination, if the relative contribution by a minor locus to a trait is less than 20 % of the contribution by a major locus. The dynamic behaviour of the model is shown to be quite complex with a possibility under sufficiently strong selection of multiple stable equilibria and positive linkage disequilibria between loci. It is also suggested that pleiotropy among loci controlling traits experiencing direct selection can be responsible for apparent selection on neutral traits also controlled by these loci.

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