Abstract
A novel mobile serial–parallel mechanism with legs for in-pipe use is proposed. The mobile robotic mechanism is composed of two identical three-universal joint–prismatic joint–universal joint parallel mechanisms connected in series and two gripping modules. The proposed parallel mechanism has two rotational freedoms and one translational freedom. In addition, the parallel mechanism can achieve continuous and equivalent rotation. The singularities of the parallel mechanism are analyzed. The overall serial–parallel mechanism has six degrees of freedom, and each gripping module has four degrees of freedom. Each parallel mechanism in the waist module is driven by three servo-electric cylinders and each leg mechanism in the gripping modules is controlled by a linear actuator. The robotic mechanism can perform peristaltic movement and turning in space. The robotic mechanism possesses a simple structure and high flexibility, along with the merits of serial–parallel mechanism. In this article, analytic models for the kinematics and dynamics of the robotic mechanism are derived. Additionally, numerical examples are given, and their solutions are validated based on results obtained by SimMechanics and Adams.
Highlights
A peristaltic robot is a bioinspired robotic mechanism that mimics the locomotion of an inchworm
According to the analysis presented in the third section, the limbs in the ith parallel mechanism (PM) generate three constraint forces and it has been proved that Rij[1] and Rij[4] intersect at point O2ij and that the constraint force, FCij, of the jth limb passing through origin O2ij is parallel to Rij[2] or Rij[3]
The architectural design of the mechanism imitates the structure of a natural inchworm and comprises a waist module and two gripping modules
Summary
A peristaltic robot is a bioinspired robotic mechanism that mimics the locomotion of an inchworm. Tian et al.[13] designed a quadruped robot with S–PM legs, and Zheng et al.[14] presented an S–PM based on two types of PMs. PMs with three active limbs are limited DOF PMs and exhibit a simple structure, easy control, and low costs. This article presents a novel 3UPU PM with 2R1T DOFs for construction of the robotic mechanism This PM exhibits better motion properties than the PM designed in the study by Chen et al.[16,17] it can realize continuous motion and equivalent rotation. The waist module comprises front and rear PMs connected in series and has six DOFs. The front PM, which consists of two platforms and three identical limbs, has identical structure to the rear PM. Each of the gripping modules creates friction when in contact with the inner wall of a pipe, which enables the robot to hold its position inside pipes with different cross sections
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