Kinematics Analysis of a Novel 5-DOF Parallel Manipulator with Two Planar Limbs
Abstract
It is significant to develop a limited-DOF parallel manipulator (PM) with high rigidity. However, the existing limited-DOF PMs include so many spherical joint which has less capability of pulling force bearing, less rotation range and lower precision under alternately heavy loads. A novel 5-DOF PM with two planar limbs is proposed and its kinematics is analyzed systematically. A 3-dimension simulation mechanism of the proposed manipulator is constructed and its structure characteristics are analyzed. The kinematics formulae for solving the displacement, velocity, acceleration of the platform, the active legs are established. An analytic example is given for solving the kinematics of the proposed manipulator and the analytic solved results are verified by the simulation mechanism. It provides the theoretical and technical foundations for its manufacturing, control and application.
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Introduction
Currently, various limited-DOF PMs are attracting much attention due to their fewer active legs, large workspace, simpler structure, easy control and simple kinematic solutions [1-2].Various limited-DOF parallel manipulators (PMs) have been applied in fields of rescue missions, industry pipe inspection, manufacturing and fixture of parallel machine tool, CT-guided surgery, health recover and training of human neck or waist and micro–Nano operation of bio-medicine [3–4]. In the aspects, Xie et al. [3] synthesized a class of limited-DOF PMs with several spherical joints(S). He and Gao [4] synthesized a class of 4-DOF PMs with 4 limbs, several S. S has the following disadvantages due to its structure: (1) the drag load capability is lower; (2) the rotation range is limited; (3) precision is lowed under alternately heavy loads. For this reason, The PMs with planar limbs have attracted many attentions because the planar limb only include revolute joints R and prismatic joint P. Wu and Gosselin [5] designed a PM with 3 planar limbs which are formed by a four-bar linkage. Lu et al. [6] proposed a novel 6- DOF PM with three planar limbs
In the aspects of kinematics of PMs, Huang et al. [1] proposed the influence coefficient matrices. By screw theory, GallardoAlvarado [2] analyzed the kinematics of a hybrid PM. Kim and Merlet [7] studied the Jacobian matrix of various PMs by different approaches. Canfield et al. [8] analyzed the velocity of PMs by truss transformations. Zhou et al. [9] studied the kinematics of some limited-DOF PMs. Lu and Hu [10] derived unified and simple velocity and acceleration of some limitedDOF PMs with linear active legs.
Up to now, no effort towards the kinematics analysis of the limited-DOF PMs with planar limbs is found. For this reason, the paper focuses on the kinematics analysis of a novel 5-DOF PM with 2 planar limbs. Its structure characteristics, kinematics and singularity are studied systematically.
Conclusion
1. A novel 5-DOF parallel manipulator (PM) with 2 planar limbs is proposed and its structure characteristics and merits are analyzed. The formulae for solving its kinetostatics are derived.
2. When given the input displacement, velocity, acceleration of the proposed PM, its output displacement, velocity, acceleration can be solved by using derived formulae. The analytic solutions of coordinated kinematics for the proposed parallel manipulator are verified by its simulation solutions.
3. The proposed PM has higher rigidity, and more room for arranging multi-finger mechanisms without interference among active legs. Each of active legs is only the subjected to a linear force along active leg, the active leg and has a large capability of load bearing.
4. The proposed PM has potential applications for of forging operator, manufacturing and fixture of parallel machine tool, assembly cells, CT-guided surgery, health recover and training of human neck or waist, and micro–Nano operation of bio-medicine, and rescue missions, industry pipe inspection. Theoretical formulae and results provide foundation for its structure optimization, control, manufacturing and applications.