Dateline: 04/04/00
Recent article on androids described how a robot with the same locomotive structure as a human ensures that it can certainly operate in any environment a human can operate in. Research teams around the world are making great efforts to develop robots that can successfully cope with environments that could not be fully anticipated nor programmed into the robot in advance. You can imagine how difficult that task can be, especially if different mechanical robot has to be designed for each experiment. But what if you could just build many copies of one simple robotic module that can be interconnected in many different ways? One module can't do much by itself, but when you connect many of them together you could get a system that can do very complicated things.
A modular robot can even reconfigure itself and change its shape by moving its modules around. This type of robots can offer advantages over traditional locomotion systems in rough environments and on unstructured terrain. Highly articulated robot systems, like snake robots, have more degrees of articulation over the traditional mobile robots, and can be used for difficult tasks like bridge inspection, space structure inspection, painting, search and rescue, security and many more. Reconfigurable modular robot can be best understood as of a collection of standard and cheap components, such as links, actuators, end-effectors, positioning stages, and sensors. These components can be rapidly reconfigured and assembled to form a workcell dedicated to a task at hand. The maintenance and upgrade of such system becomes very easy, plug-and-play type of job. Mini-workshops and desktop manufacturing become the reality, allowing users to to keep up with the rapid changing marketplace by quickly converting manufacturing lines from one product to the other. I admit it sounds more like Science Fiction (every modern child knows about Transformers and similar stuff), so here are a few real-world examples...
Modular Robots at Xerox PARC
Researchers at the Xerox Palo Alto Research Center carry out a wide variety of modular robot projects under the MEMS/Smart Matter Research. MEMS (Micro-Electro-Mechanical-Systems) is a set of technologies that make it possible to mass produce large numbers of integrated sensors, actuators, computers, and communication systems that can be embedded within products or spread throughout the environment. Although today's structure and product designers have many materials with varied properties to choose from, once a particular material is selected and cut to size, its properties remain fixed. Making the dynamic behavior of matter programmable - creating "smart matter" - has the potential to enable an entirely new generation of mechanisms and products. A key aspect of PARC's research strategy is to move MEMS beyond its micro-scale origins, to create a new field that called Systemic MEMS, which includes uEMS (micro-scale), mEMS (meso-scale), and MEMS (Macro-scale).
As for the specific projects, Polypod is a bi-unit modular robot, built by Mark Yim. This means that the robot is built up of exactly two types of module prototypes that are repeated many times (until now there are 11 types of actual modules and up to 180 simulated modules). This repetition makes manufacturing easier and cheaper. Dynamic reconfigurability allows the robot to be highly versatile, reconfiguring itself to whatever shape best suits the current task. To study this versatility, locomotion was chosen as the class of tasks for examination. PolyBot is the next generation of Polypod whose work started in August 1998. The primary functional difference between PolyBot and the previous versions is the implementation of automatic reconfiguration. The target module size has been reduced to 5 centimeters per side, with the connecting plates allowing easier reconfiguration. This includes larger chamfers to help passively guide mating parts together as well as guiding beacons and sensor system to actively aid in mating. The DOF (Degrees Of Freedom) of the modules has been reduced to one DOF per module to ease the size constraint. The first generation of PolyBot uses simple hobby servo's typically found on RC toys, without onboard computation or sensors. Up to 32 modules were incorporated into one connected component, screwed together. Automatic connecting of modules was not implemented. Next generation of PolyBot included onboard computing (Power PC 555) as well as the ability to reconfigure automatically via shape memory alloy actuated latches. Generation three is currently under development - target date for prototype is end of 2000.
Another advanced project, Proteo, explores the issues in scaling up the number of distributed robotics to hundreds, thousands, maybe millions or more. Imagine a pile of little robot modules, sitting on your desk, that could form arbitrary shapes on your command. Applications of this technology would include 3D visualization in prototyping, self moving/adapting furniture, portable ladders, building materials, arbitrary shaped tools, etc. Digital Clay project is a subset of the modular robotics project, without active coupling and actuation for producing module to module motions. Changes to an assembly of modules is made by a user. It embodies one very important aspect that the modules have some capacity to sense or know their own orientation in space with respect to other modules. As such it may be a useful hardware system for testing software, communications and power distribution for physically modular systems. It can be also used as a 3D human-computer interface, where user can actually experience real 3D objects, and yet has a direct representation in a CAD program.
Modular Reconfigurable Robot and Manufacturing Systems at Caltech
The objective of this research is to design, simulate, and construct a reconfigurable workcell based on component technology. Such a system will possess benefit from robot manipulators and CNC machine tools, such as high precision, large working envelope, moderate loading, high throughput and open control architecture. Research efforts are primarly focused on the development of RISC (Reduced Intricacy in Sensors and Control) algorithms and hardware to reduced the complexity and degrees of freedom in the modular robot. Direct industrial applications will be autonomous deburring and grinding of workpieces, while other potential applications will be in microelectronics and consumer electronics assembly, biomedical laboratory automation, and service industries.
Darpa Microrobot Project
The goal of this project is to design, build, and test a prototype of micro-robot that will exhibit multiple forms of locomotion.The suction cups located at the robot extremities provide the ability to climb walls and flip over obstacles. Highly sensitive diamond sensors will be incorporated into the robot structure for sensor-based learning. The robot will be able to actively determine and transition to the effective mode of location necessary for accomplishing a specific mission. It will be able to work individually or team up with other robots to perform a given mission.
The first prototype includes two suction cups and two legs, with one suction cup attached to each leg. Altogther, the robot has 4 joints controlled by 3 motors. It was demonstrated at the DARPA Distributed Robotics Program held on September 12-15, 1999 at the Quantico US Marine Base, showing its capability to walk on a real wall.
CMU I-Cubes
I-Cubes are a class of modular self-reconfigurable bipartite robotic system. This system is a collection of independently controlled mechatronic modules (links) and passive connection elements (cubes). A link has the ability to connect to and disconnect from the face of a cube. While attached to a cube on one end, links are also capable of moving themselves and another cube attached to the other end. As the links (and attached cubes) move, attach, and detach themselves to the cubes, the morphology of the system changes. All active and passive modules are capable of permitting power and information flow to their neighboring modules.
The USC/ISI CONRO project
The CONRO Project has a goal of providing the modern soldier with a miniature reconfigurable robot that can be tasked to perform reconnaissance, search and identification tasks in urban, seashore and other field environments. CONRO will be miniature, about 2.5cm long, and is to be made from identical modules that can be programmed to alter its topology in order to respond to environmental challenges. The base topology is simply connected, as in a snake, but the system can reconfigure itself in order to grow a set of legs or other specialized appendages. Each module will consist of a CPU, some memory, a battery, and a micro-motor plus a variety of other sensors and functionality, including vision and wireless connection and docking sensors.
Self-reconfiguring Robots at The Dartmouth Robotics Lab
The Molecule is a 4 degree-of-freedom, small-scale module capable of aggregating with other identical modules to form three-dimensional dynamic structures. The Molecule consists of two atoms connected by a right-angle rigid bond. Each atom has 5 inter-Molecule connectors and two degrees of freedom. One degree of freedom allows rotation about one connector. The second degree-of-freedom allows rotation of the atom about the bond.
Cubic shaped Crystal Module features connectors to other modules in the middle of each face. The module can be actuated to expand by a factor of two and to contract by a factor of two. This prototype can only move in the x and y directions but the design is easily extensible to allow for movement in the z direction as well.
Modular, Reconfigurable Robot at Rensselaer
The Center for Automation Technologies produces a modular system for the design, implementation, and control of a class of highly redundant and reconfigurable robotic mechanisms. The Tetrabot features a novel concentric multilink spherical (CMS) joint which facilitates the construction of a wide variety of variable geometry mechanisms using an integrated control and computational framework. Design software allows different configurations to be rapidly simulated, and generates outputs detailing the number and types of hardware components required. This system is currently being evaluated as a potential solution to flexible shoring requirements in construction and maintenance tasks encountered by electric and gas utilities.
Reconfigurable Modular Manipulator System at CMU
The RMMS utilizes a stock of interchangeable joint (actuator) and link modules of different size and performance specifications. The modularity in mechanical, electrical and electronic design allows the user to design the optimal manipulator for the task at hand. The RMMS extends the concept of modularity to also include the control algorithms and task planning software. With this combination of capabilities, the RMMS can be configured to meet the task requirements as they arise at the application site. First prototype includes four joints and links of varying sizes, controled by a Chimera real-time control system.
CMU Agile Assembly Architecture
The Architecture for Agile Assembly (AAA) aims to reduce the time to deploy a new assembly factory from months to weeks, with adjustment to product changes in less than an eight-hour shift. It will enhance product quality in several ways including reducing parts-workpiece alignment errors to micrometer levels, and substantially reduce the floor space required for product assembly. The architecture relies on a distributed community of capable agents. However, an agent is here much more than a mere computational process: it encompasses a mechanical device with integrated computational, communication, and algorithmic support for its operation. Each agent presents a standardized mechanical, communication, and algorithmic interface through which it can interact with both its peers and its environment. By standardizing these interfaces and producing devices that recognize their need to cooperate with their peers from the outset, AAA enables the rapid design, deployment, and reconfiguration of automated assembly systems.
Fractal Robots
Fractal robot is a new kind of robot made from motorized cubic bricks that move under computer control. These cubic motorized bricks can be programmed to move and shuffle themselves, changing shape to produce various objects a few seconds using their internal mechanisms. The size available in prototype form is 10 inches and 5 inches in size made of 1.5 mm thickness aluminium panels. The next generation of machines are expected to be 8" and 16" built from 1/8" thickness aluminium plates. The machines are under research and development right now and may become commercially available in mid 2000 (as this is only "non-academic" site in this review).