TriM: An ultra-accurate high-speed six degree-of-freedom manipulator using planar stepper motors

P. Krishnamurthy, F. Khorrami

Research output: Contribution to journalArticlepeer-review


In this paper, we propose a novel six degree-of-freedom positioning system. This mechanism is a tripod structure with inextensible limbs actuated at the base by two-dimensional linear stepper motors (other types of actuators may also be utilized). This manipulator has a closed-chain kinematic structure. Both the direct and the inverse kinematics of the manipulator are presented in detail. While the inverse kinematics are obtained in closed form, the direct kinematics can not be solved in closed form and an algorithm is provided for numerically computing the direct kinematic solution. A detailed dynamic model of the positioning system is also provided. The dynamics of the actuators (Sawyer motors) are also included in the dynamic modeling. The design of the tripod manipulator (TriM) included a kinematic optimization of the system parameters to maximize the manipulator workspace. The proposed manipulator achieves large range of motion in all the 6 degrees of freedom. Furthermore, high resolution and high speed motion may be achieved in all axes due to the actuators used and the direct-drive nature of the manipulator.

Original languageEnglish (US)
Pages (from-to)137-157
Number of pages21
JournalJournal of Intelligent and Robotic Systems: Theory and Applications
Issue number2
StatePublished - Feb 2008


  • Closed-chain manipulator
  • Dynamics
  • Kinematics
  • Workspace optimization

ASJC Scopus subject areas

  • Software
  • Control and Systems Engineering
  • Mechanical Engineering
  • Industrial and Manufacturing Engineering
  • Artificial Intelligence
  • Electrical and Electronic Engineering


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