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A parallel robot is a closed-loop mechanism in which the mobile platform is connected to the base by at least two serial kinematic
chains (legs). Applications of this type of robots can be found in the motion platform for the pilot training simulators and the positioning device for high precision surgical tools because of the high force loading and very fine motion characteristics of the closed-loop mechanism. Recently, researchers are trying to utilized these advantages  to develop parallel-type robot based multi-axis machining tools and  precision assembly tools. However, the complicate structure of the mechanism not only limits the motion of the platform but also creates complex kinematic singularity in the workspace of the mobile platform, and therefore, makes the design, trajectory planning and application development of the parallel robot difficult and tedious. To overcome this drawback, here we introduce modular design concept in the development of parallel robots. A modular parallel robot system will consist of a set of independently designed modules, such as actuators, passive joints, rigid links (connectors), mobile platforms, and end-effectors, that can be rapidly assembled into a complete robot with various configurations (degree of freedom and geometry), possessing different kinematic and dynamic characteristics. In the past, modularity concept has been introduced in the design of serial-type industrial robots for flexibility, ease of maintenance, and rapid deployment. From our experience, a modularly design reconfigurable parallel robot not only possesses the above advantages but can truly shorten its development cycle, i.e., the time from design, construction, to deployment. Because modularity design reduces the complexity of the overall design problem to a manageable level.

To develop a modular parallel robot system, we propose to employ the following two types of modules to simplify the design effort: standard actuator, passive-joint, or end-effector modules with fixed dimensions , and rigid linking and connecting modules including the mobile platforms whose dimensions can be custom-designed and fabricated easily.  Through the use of different types of standard active or passive joint modules, the topological design becomes simply the configuration enumeration type of procedures. Whereas the custom-fabricated linking modules become the main target for the dimensional design. In this manner, the two major design stages can be clearly outlined, specific design tools can be developed for different design stages, and the overall design process can be streamlined. Most importantly, one can adopt the try-and-error types of development operations as certain modules can be rapidly fabricated. This is definitely impossible for a conventional parallel robot.

Current Research Projects

A. Kinematic design of parallel robots 
Forward Singularities of 3-legged RRRS and RPRS parallel manipulators

Workspace visualization

Cross sections of Workspace (3-legged RRRS parallel manipulator)

B. Micro-positioning parallel mechanisms for photonic and biomedical applications
  • Investigator: Mr. Huy Hoang Pham

C. Novel joint-coupling mechanisms for singularity management in parallel manipulators

  • Investigator: Ms. Theingi

D. Selectively actuated parallel mechanisms

  • Investigator: Mr. Yan Jin

E. Cable-Driven mechanisms

  • Investigator: Mr. Pham Cong Bang and Mr. Mustafa Shabbir Kurbanhusen

F. LEGO models for parallel mechanisms

Parallel Robot Fleet

Planar  RRRS RPRS (1) RPRS (2)
End-mill machine (1) End-mill machine (2) Hybrid (1) Hybrid (2)

Parallel Robot Simulation Software - SEMORS-PKM
SEMORS-PKM (Simulation for MOdular Reconfigurable Robotic Systems - Parallel Kinematic Machine extension)
  • Kinematic simulation software for modular parallel robots based on Product-Of-Exponential formulation
  • Windows 98/ME/NT4.0/2000 platform
  • Screen shots of SEMORS-PKM

Singularity analysis and visualization Teaching pendant (Cart. space) Teaching pendant (joint space)


Nanyang Technological University - Carnegie Mellon University (NTU-CMU) Joint Symposium on Advances in Robotics
[Orchard Hotel, Singapore 24 August 2001]

Reconfigurable Parallel-Kinematics Machines - Prof. I-Ming Chen [Powerpoint presentation, pdf, 3.6MB]

Copyright © 2004  Modular robotic & Robot locomotion Group, School of MPE, NTU