Author: Steven Floyd, Eric Diller, Chytra Pawashe and Metin Sitti
Source: The International Journal of Robotics Research 2011 30: 1553.
This paper proposed a methodology to make several micro-robots respond differently to the same driven magnetic field.
To achieve the uniqueness of each robot, the following designs were employed: (1) geometrically similar Mag-uBots with different values of magnetization; (2) geometrically dissimilar Mag-uBots with similar magnetization; and (3) geometrically dissimilar Mag-uBots with dissimilar magnetization. The magnitude and frequency of the imposed driving magnetic fields are used as selection methods among the Mag-uBots.
It is found that while fully decoupled control is not possible with this method, parallel actuation of sub-groups of Mag-uBots is possible and controllable.
The methods proposed in this paper doesn’t require for a specialized substrate.
2. Tools & System
The robots in this work are actuated by 6 independent electromagnetic coils.
3.1 Magnetic Torque
The magnetic forces are assumed to be negligible in the analyses.
3.2 Gravitational Rest Torque
To achieve stick-slip motion, the magnetic torque must overcome the gravitational rest torque to lift the Mag-uBots onto an edge.
3.3 Other Forces & Torques
Surface adhesion, electrostatic attraction and viscous damping.
3.4 Natural Frequency
4. Selection Methods
By choosing appropriate values for magnitude, direction, and frequency of the magnetic field, all, none, or some of the Mag-uBots in the workspace can be selected and translated.
4.1 Selection via Internal Magnetization
4.2 Selection via Shape Demagnetization Factor
4.3 Selection via Rotational Inertia
5 Results & Discussion
5.1, 5.2 & 5.3 are same titles with 4.1 – 4.3.
While independent control of an arbitrary individual was not possible, by establishing the appropriate rules and algorithms, an arbitrary final configuration of Mag-uBots was achieved from an arbitrary initial configuration.
3 methods for the control of heterogeneous groups of magnetic micro-robots were demonstrated.
Q: In section 5.2, the Fig. 12 shows that the R4 has the largest moving area while R6 has the narrowest. But from the analysis and following figures, I think R4 actually has the narrowest moving area and R6 has the largest (R5 has the medium area).