Simulated Motion Control of a School of Microrobots with Random Walks

The dynamics of individual elements in a swarm moving in biological fluids is an important aspect to ascertain the effectiveness of cumulative motion control. The hydrodynamic interaction between the swarm and surrounding walls as well as between the micro-swimmers, i.e., magnetotactic bacteria, within the swarm are affected by Brownian motion. A small group of magnetically-controlled bacteria swimming in a biological fluid could be simulated in a simplified fashion to design and test controllers for addressable motion with random walks. Furthermore, the disruptive effect of the random walks might prove detrimental to the control performance. This paper showcases a simulation study of adaptive motion control for a trio of magnetotactic bacteria swimming as a group in human synovial fluid. The bacterial group is confined by the joint geometry and maneuvered by the external magnetic field of a permanent magnet positioned by an open kinematic chain. Results show that it is possible to control the yaw angle of the bacterial group while swimming under the influence of repulsive force and the Brownian noise although each swimmer follows a different path. It is further observed that, when bacteria came in contact with solid surfaces, the control algorithm could be prone to misinterpreted sensory data.