Miche: Modular Self-Disassembly
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Self-Assembly by Disassembly
The Miche system is a collection of robots that, starting from an amorphous arrangement, can be assembled into arbitrary shapes and then commanded to self-disassemble in an organized manner. Much like a sculptor would remove the extra stone from a block of marble to reveal a statue, the Miche system, (short for Michelangelo), eliminates unnecessary modules to form a goal structure. Shape formation with Miche modules proceeds as follows. First, an initial amorphous shape is assembled by hand. The modules in this initial structure use local communication to establish their location within a system of coordinates. After the initial configuration has been assembled, the user provides a goal shape for the system. Using local communication, the group cooperates to distribute this information so that all modules know whether to remain as a part of the system or to extricate themselves. Finally, the unnecessary modules disconnect from the system and drop off to create the desired shape.
Creating robotic systems and smart objects by self-disassembly has one main advantage over existing approaches by self-assembly. Self-disassembling systems entail a simple actuation mechanism to disconnect which is generally easier, faster, and more robustly achievable than actively seeking and making connections. In our system, external forces must be employed to remove unwanted material from the system. Often, these forces can be found in the surrounding environment. For our experiments, we used gravity to pull unnecessary modules away from the final structure.
Modular robots that can self-disassemble provide a simple and robust approach toward the goal of smart structures, digital clay, and programmable matter. A collection of millions of modules, if each were small enough, could form a completely malleable building material that could solidify and then disassemble on command. Most types of objects and shapes could be created this way. The applications of self-disassembling systems include all the applications of self-assembling systems. The added flexibility of removing specific components from the assembly ensures that our approach is especially well suited to tasks requiring temporary supporting structures. For example, self-disassembling material could be applied as an active scaffolding to help heal severely broken bones that would otherwise require the use of permanent steel plates or pins. In addition to disassembling as the bone regrows, the scaffolding could provide valuable medical status information to doctors. In such a scenario, the bloodstream could carry away extra modules.
Each Miche module contains the resources necessary for autonomous operation: processing capabilities, actuation mechanisms, communication interfaces, and power supplies. The modules are built from six distinct printed circuit boards that interlock to form a rigid structure. When completely assembled, each cubic module is 1.8 inches on a side and weighs 4.5 oz. All electronic components are surface mounted on the top side of the boards so that when assembled into cubes, all components reside on the inside.
Individual modules bind to each other using switchable permanent magnet assemblies produced by Magswitch Technology, Inc. Three of the faces of each cubic module contain Magswitches. The other three cube faces of each cube are covered by steel plates. When multiple cubes are assembled into a structure, the Magswitches always attach to the steel plates of a neighboring cube, not one of the other cube's Magswitches. As a result, the modules can only attract one another. They do not repel but, instead, depend upon gravity or user intervention to clear unused modules from any final structure.
The Magswitch assemblies control a magnetic field by changing the relative orientation of two permanent disc magnets. The advantage of using Magswitches is that power is only consumed while changing their states. Once a Magswitch is on or off, it remains in that state indefinitely. This is invaluable for the battery life of the modules. A miniature pager-sized motor with an integrated planetary gear box drives each Magswitch. An analog Hall Effect sensor is used to detect the state of each Magswitch. The Hall Effect sensor is placed such that its axis of sensitivity is aligned with the magnetic field produced by the Magswitch. As the Magswitch rotates, the Hall Effect sensor produces a voltage that approximates a sine wave.
|self-assembly of a dog by disassembly|
|self-assembly humanoid by disassembly|
Kyle Gilpin, Keith Kotay, Daniela Rus, and Iuliu Vasilescu. Miche: Modular Shape Formation by Self-Disassembly. The International Journal of Robotics Research 2008 27: 345-372.
Kyle Gilpin, Keith Kotay, and Daniela Rus. Miche: Modular Shape Formation by Self-Dissasembly. IEEE International Conference on Robotics and Automation 10-14 April 2007 pp.2241--2247