Code and algorithms for Steering Catalytic Janus Particles
Authors: Li Huang and Aaron T. Becker
Email: [email protected]
All rights reserved.
A catalytic Janus particle is a two-faced particle with one face that reacts with the surrounding medium to produce thrust. By using a permanent magnet core, the particle can be steered. Unlike many current microrobots that are steered and propelled by an external magnetic field, these particles have independent steering and propulsion mechanisms. Janus particles can be manufactured in large numbers. An offset angle between their thrust and magnetization vectors can provide kinematic heterogeneity in a uniform magnetic field, which is the key for controlling multiple microrobots. In the 2D case, only two degrees-of-freedom (DOF) are controllable. We review controllability results in 2D, and then show that interesting things happen in 3D. We provide control laws for steering up to nine DOF, which can be mapped in various ways, including to control the x; y; z position of three particles, make four particles meet, or reduce the spread of n particles. A hardware implementation is described.
Open-loop control Janus spheres using linear programmingClosed-loop control using random rotation matricesClosed-loop control using linear programmingClosed-loop control using greedy optimal controlControl four spheres to collideControl 9 spheres up to 9 DOFSteer 10 spheres closer to each other
Janus sphere simulations of open-loop control using linear programming. The goal locations are indicated by green orbits. In each figure, all spheres move the same total distance and reach the goal location at the same time. A colored line describes the trajectory of each Janus sphere. Black arrows indicate the magnetic moment orientation for the subsequent move.
Janus sphere simulations of (closed-loop) linear programming. The demo shows three spheres’ trajectories, and the corresponding sum of squared distance error.
Janus sphere simulations of (closed-loop) optimal greedy control. The demo shows three spheres’ trajectories, and the corresponding sum of squared distance error.
Trajectories of four spheres moving towards their mean position till they collide, and trajectories of three spheres chasing the fourth sphere till they collide. These two cases have the same initial conditions with different target position, but the four spheres collide at the same spot.
Closed-loop control simulation of nine Janus spheres with 3D view, xz plane view, and xy plane view. Three groups of spheres (red, blue, and green) are delivered to x = 0, z = 0, and y = 0 planes respectively
