Robot manipulators (in short manipulators) are popular tools in a large range of industrial fields including manufacturing, assembly and quality control. The primary incentive for manipulators is to be reprogrammable for a variety of tasks. Therefore, they are more versatile than their fixed-automation counterparts in that they are able to switch from one task to another with minimal adjustments. However, conventional manipulators are limited by their mechanical structure to a set range of tasks. The number of the joints, along with their layout would be determined in their design and fabrication based on the range of tasks the manipulator would likely encounter. The number of degrees of freedom (DOF's) for industrial manipulators typically varies from 4-7. Ideally, a manipulator would be chosen to have the number and configuration of joints best suited for their expected range of tasks. However, this is often not the case, as manipulators with custom-configuration are expensive and time-consuming to specify. It is usually the case that the best manipulator configuration from a range of available industrial manipulators is chosen and implemented for a range of tasks. However, even in the ideal case of custom implementation, the manipulator is not optimized for each individual task, but rather for a collection of different tasks. For each individual task, it could have too many or too few joints, and likely have the joints in less-than-optimal configurations. A reconfigurable manipulator can provide a range of configurations, by including or removing joints and changing their relative positioning, which enables the robot to optimally perform a much larger variety of tasks, thus expanding the versatility of the robot manipulator.
In addition to industrial and service applications, a reconfigurable platform for robot manipulators can be greatly helpful for the purpose of design and development as well as research and education. Such a platform can be utilized as a rapid-prototyping means for investigating various configurations for new manipulators and/or control modules. As well, such a platform can be a cost-effective solution for the students and researchers to physically model various robot manipulators and study their performance, as it is often far too expensive to gain access to more than one manipulator for a thorough study or learning experience.
FIG. 1 shows the Reconfigurable Module Manipulator System (RMMS) from “A Rapidly Deployable Manipulator System” (C. Paredis, H. Brown, P. Khosla, “A Rapidly Deployable Manipulator System,” Robotics and Automation, IEEE International Conference on, April 1996, pp 1434-1439), which is a manually-reconfigurable serial manipulator with a discrete reconfiguration scheme. By rearranging the modules, the kinematic and dynamic properties of the manipulator can be changed. The RMMS is pneumatically actuated, and is capable of only revolute motion. The modules that make up the manipulator are non-homogenous in size and layout. The configuration shown in FIG. 1 is made up of 6 modules, totalling 4 DOF's.
A second reconfigurable serial manipulator system, shown in FIG. 2, from “Interactive-Motion Control of Modular Reconfigurable Manipulators” (W. Chen, G. Lang, E. Ho, I. Chen, “Interactive-Motion Control of Modular Reconfigurable Manipulators,” Robotics and Automation, IEEE International Conference on, October 2003, pp. 1620-1625), is capable of both serial and branched (two or more end-effectors) configurations. This manipulator is also discreetly reconfigurable, via a set of 1-2-DOF non-homogeneous modules. The modules are capable of either revolute or prismatic motion, allowing the system to assume configuration with prismatic joints. The manipulator is manually reconfigured by a human operator.
Another type of modular reconfigurable serial manipulator, from “Modular, Expandable And Reconfigurable Robot” (A. Goldenberg, N. Kircanski, P. Kuzan, J. Wiercienski, R. Hui, C. Zhou, “Modular, Expandable And Reconfigurable Robot”, USPTO #5523662, Jun. 4, 1996) is a collection of 1-DOF modules of revolute actuation that can be assembled into various configurations. This manipulator uses brushless DC motors through harmonic drive gearing, and is manually reconfigurable. Reconfiguration requires complete or near complete disassembly of the manipulator.
Another type of robot relevant to this patent is the self-reconfigurable robot. These robots are often modular assemblies that are able to reconfigure their kinematics either manually or autonomously.
In “Telecubes: Mechanical Design of a Module for Self-Reconfigurable Robotics” (J. Suh, S. Homans, M. Yim, “Telecubes: Mechanical Design of a Module for Self-Reconfigurable Robotics,” Robotics & Automation, IEEE, Vol 4, May 2002, pp. 4095-4101.), a robot call Telecubes is presented, shown in FIG. 3. The Telecubes robot is a collection of 3-DOF modules that have orthogonal prismatic motion. Modules are able to autonomously link and un-link from each other to create new configurations.
Similar to the Telecube robot is the robot presented in “Self Reconfigurable Cellular Robotic System” K. Tanie, H. Maekawa, “Self Reconfigurable Cellular Robotic System”, USPTO #5361186, Nov. 1, 1994. It is also constructed from 3-DOF modules of orthogonal prismatic motion, shown in FIG. 4. Unlike the Telecube, the cellular robot retracts one side while it extends on the other side. The Telecube retracts and extends both sides at the same time. The Cellular robot is also able to autonomously change its configuration.
The Crystalline Robot, shown in FIG. 5, and described in “Crystalline Robots: Self-Reconfiguration with Compressible Unit Modules” (D. Rus, M. Vona, “Crystalline Robots: Self-Reconfiguration with Compressible Unit Modules,” Autonomous Robots, Vol 10, Number 1, January 2001, pp. 107-124) is a 1-DOF representation of a prismatic self-reconfigurable robot. This robot is also capable of autonomous reconfiguration of its modules, through automatic linking and un-linking of modules.
The M-TRAN Robot, shown in FIG. 6 and described in “Modular Self-Reconfigurable Robot Systems” (M. Yim, W. Shen, B. Salemi, D. Rus, M. Moll, H. Lipson, E. Klavins, G. Chirikjian, “Modular Self-Reconfigurable Robot Systems,” Robotics & Automation, IEEE, Vol 14, Issue 1, March 2007, pp. 43-52) is a self-reconfigurable robot that is capable of revolute motion instead of prismatic. Each robotic module has 2-DOF, and is capable of autonomous reconfiguration. It should be noted that “Modular Self-reconfigurable Robot Systems” also describes several other self-reconfigurable robots similar to the ones previously mentioned. One common shortcoming in all of them is the inability to lift more than a few modules in weight. A list of similar robots is present in FIG. 7.