Cargo capture and transport by colloidal swarms

Controlling active colloidal particle swarms could enable useful microscopic functions in emerging applications at the interface of nanotechnology and robotics. Here, we present a computational study of controlling self-propelled colloidal particle propulsion speeds to cooperatively capture and transport cargo particles, which otherwise produce random dispersions. By sensing swarm and cargo coordinates, each particle’s speed is actuated according to a control policy based on multiagent assignment and path planning strategies that navigate stochastic particle trajectories to targets around cargo. Colloidal swarms are shown to dynamically cage cargo at their center via inward radial forces while simultaneously translating via directional forces. Speed, power, and efficiency of swarm tasks display emergent coupled dependences on swarm size and pair interactions and approach asymptotic limits indicating near-optimal performance. This scheme exploits unique interactions and stochastic dynamics in colloidal swarms to capture and transport microscopic cargo in a robust, stable, error-tolerant, and dynamic manner.

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Principal eigenvalue characterization connected with stochastic particle motion in a finite interval

Journal of Applied Mathematics and Stochastic Analysis ◽

10.1155/s104895330200028x ◽

2002 ◽

Vol 15 (4) ◽

pp. 349-356

Author(s):

Fethi Bin Muhammad Belgacem ◽

Ahmed Abdullatif Karaballi

Keyword(s):

Maximum Principle ◽

Stochastic Dynamics ◽

Finite Interval ◽

Principal Eigenvalue ◽

Planck Equation ◽

The Maximum Principle ◽

Constant Diffusion ◽

Indefinite Potential ◽

Finite Domains ◽

Stochastic Particle

In this paper, we show that despite their distinction, both the Statonovich and Îto s calculi lead to the same reactive Fokker-Planck equation: ∂p∂t−∂∂x[D∂p∂x−bp]=λmp, (1) describing stochastic dynamics of a particle moving under the influence of an indefinite potential m(x,t), a drift b(x,t), and a constant diffusion D. We treat the periodic-parabolic eigenvalue problem (1) for finite domains having absorbing barriers. We show that under conditions required by the maximum principle, the positive principal eigenvalue λ* (and the negative principal λ* eigenvalue) is connected to the probability eigendensity function p(x,t) by a Raleigh-Ritz like formulation. In the process, we establish the manner of effect of the drift and any inducing potential on the size of the principal eigenvalue. We show that the degree of convexity of the potential plays a major role in this regard.

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Reward-dependent selection of feedback gains impacts rapid motor decisions

10.1101/2021.07.25.453678 ◽

2021 ◽

Author(s):

Antoine De Comite ◽

Frederic Crevecoeur ◽

Philippe Lefevre

Keyword(s):

Muscle Activity ◽

Control Strategies ◽

Control Policy ◽

Movement Planning ◽

Baseline Activity ◽

Planning Strategies ◽

External Loads ◽

Direction Opposite ◽

Selection Of ◽

Background Load

Expected reward is known to affect planning strategies through modulation of movement vigor. Strikingly, although current theories suggest that movement planning consists in selecting a goal-directed control policy, the influence of reward on feedback control strategies remains unknown. Here we investigated this question in three human reaching experiments. First, we varied the explicit reward associated with the goal target and found an overall increase in movement vigor for higher reward targets, highlighted by larger velocities, feedback responses to external loads, and background muscle activity. Then, assuming that larger feedback gains were used to reject perturbations, we sought to investigate whether this effect hindered online decisions to switch to a new target in the presence of multiple successful goals. We indeed observed idiosyncratic switching strategies dependent on both target rewards and movement vigor, such that the more vigorous movements were less likely to switch to a new goal following perturbations. To gain further insight into a causal influence of movement vigor on rapid motor decisions, we demonstrated that biasing the baseline activity and reflex gains by means of a background load evoked a larger proportion of target switches in the direction opposite to the background load associated with lower muscle activity. Our results highlight the competition between movement vigor and flexibility to switch target during movement.

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