Free singularity path planning of hybrid parallel robot

This paper presents a singularity-free path planning approach for a hybrid parallel robot. The hybrid robot is composed of two well-known parallel robots, a hexapod and a tripod, that are serially connected. In this paper a methodology is developed to avoid singularity configurations of the hybrid parallel robot. Nominal polynomial paths are used for motion of end effector, and the strokes of each actuator is calculated by using the developed inverse kinematic. A MATLAB program has been developed to generate the designed paths, and several poses have been tested in a CAD model of the hybrid parallel robot to validate the feasibility of the path planning approach

Design and motion control of a 6-UPS fully parallel robot for long bone fracture reduction : a thesis presented in partial fulfillment of the requirements for the degree of Master of Engineering in Mechatronics at Massey University

The incidences of long bone fractures in New Zealand are approximately 1 in 10,000. Long bones such as tibia and femur have complicated anatomic structures, making the realignment of these long bone fractures reliant on the skill of the surgeon. The drawbacks of current practice result in long time exposure to radiation, slow recovery and possible morbidity. A semi-automated long bone fracture reduction system based on a 6-DOF parallel robot platform has been in development since 2004. The developed 6-DOF parallel robot platform comprises of six linear actuators with rotary incremental encoders. To implement a realignment of long bone fractures, a framework for the 6-DOF platform robot has been developed. The inverse kinematics and singularity of the 6-DOF parallel robot has been studied to obtain the actions and Jacobin matrices. In motion control a multiple axis motion controller and amplifiers were used for 6-DOF parallel robot. PID tuning algorithms were developed based on the combination of the general tuning result and the contour control principle. The PID parameters have been validated by a number of experiments. The practical realignment of bone fractures requires a "Pull-Rotate-Push" action implemented by the 6-DOF parallel robot. After calibration, the reduction trajectories were generated accurately. The actual trials on the artificial fractures have shown that the robot developed is capable of performing the required reduction motion

Dynamics of the Orthoglide parallel robot

Recursive matrix relations for kinematics and dynamics of the Orthoglide parallel robot having three concurrent prismatic actuators are established in this paper. These are arranged according to the Cartesian coordinate system with fixed orientation, which means that the actuating directions are normal to each other. Three identical legs connecting to the moving platform are located on three planes being perpendicular to each other too. Knowing the position and the translation motion of the platform, we develop the inverse kinematics problem and determine the position, velocity and acceleration of each element of the robot. Further, the principle of virtual work is used in the inverse dynamic problem. Some matrix equations offer iterative expressions and graphs for the input forces and the powers of the three actuators

How to Expand the Workspace of Parallel Robots

In this chapter, methods for expanding the workspace of parallel robots are introduced. Firstly, methods for expanding the translational workspace of the parallel robot are discussed. The parallel robot has multiple solutions of the inverse and forward displacement analysis. By changing its configurations from one solution to another, the parallel robot can expand its translational workspace. However, conventional nonredundant parallel robot encounters singularity during the mode change. Singularity-free mode changes of the parallel robot by redundant actuation are introduced. Next, methods for expanding the rotational workspace of the parallel robot are shown. In order to achieve the large rotation, some mechanical gimmicks by gears, pulleys, and helical joints have been embedded in the moving part. A novel differential screw-nut mechanism for expanding the rotational workspace of the parallel robot is introduced

Kinematic Analysis of a Continuum Parallel Robot

Conference Paper presented at EUCOMES 2016 held in Nantes, France, from 20 to 23 September 2016Continuum Parallel Robots are mechanical devices with closed loops where kinematic pairs have been eliminated and motion is obtained by large deformations of certain elements. Most compliant mechanisms use notches in thick elements to produce the effect of kinematic pairs. A few are designed so that slender elements can deform and produce the desired motion. Some microelectromechanical systems have used this principle to create bistable planar mechanisms. The purpose of this work is to extend such principle in the field of macro mechanisms for manipulation. The aim is to design the counterparts to some classical parallel manipulators solving the corresponding kinematic problems. In doing this, the authors will have to work out the most efficient way to solve a position problem where geometry and forces are involved. Such compliant mechanisms could be combined in the future with tensegrity systems to enhance the available workspace. In this first report, we will focus on the simplest planar parallel mechanism of two degrees of freedomThe authorswish to acknowledge the financial support received fromthe Spanish Government through theMinisterio de Economía y Competitividad (Project DPI2015-64450-R) and the Regional Government of the Basque Country through the Departamento de Educación, Universidades e Investigación (Project IT445-10) and UPV/EHU under program UFI 11/29. Also, the support of ERASMUS program is gratefully acknowledged by the fourth autho

Kinematics and workspace analysis of a 3ppps parallel robot with u-shaped base

This paper presents the kinematic analysis of the 3-PPPS parallel robot with an equilateral mobile platform and a U-shape base. The proposed design and appropriate selection of parameters allow to formulate simpler direct and inverse kinematics for the manipulator under study. The parallel singularities associated with the manipulator depend only on the orientation of the end-effector, and thus depend only on the orientation of the end effector. The quaternion parameters are used to represent the aspects, i.e. the singularity free regions of the workspace. A cylindrical algebraic decomposition is used to characterize the workspace and joint space with a low number of cells. The dis-criminant variety is obtained to describe the boundaries of each cell. With these simplifications, the 3-PPPS parallel robot with proposed design can be claimed as the simplest 6 DOF robot, which further makes it useful for the industrial applications

Motion planning of a climbing parallel robot

This paper proposes a novel application of the Stewart–Gough parallel platform as a climbing robot and its kinematics control to climb through long structures describing unknown spatial trajectories, such as palm trunks, tubes, etc. First, the description and design of the climbing parallel robot is presented. Second, the inverse and forward kinematics analysis of a mobile six-degrees-of-freedom parallel robot is described, based on spatial constraint formulation. Finally, the gait pattern and the climbing strategy of the parallel robot is described. The information from this research is being used in an actual climbing parallel robot design at Miguel Hernández University of Elche (Alicante), Spain.This paper was recommended for publication by Associate Editor M. Shoham and Editor I. Walker upon evaluation of the reviewers’ comments. This work was supported by the Spanish Ministry of Education and Culture under Project 1FD1997-1338

Rotation symmetry axes and the quality index in a 3D octahedral parallel robot manipulator system

The geometry of a 3D octahedral parallel robot manipulator system is specified in terms of two rigid octahedral structures (the fixed and moving platforms) and six actuation legs. The symmetry of the system is exploited to determine the behaviour of (a new version of) the quality index for various motions. The main results are presented graphically

An Active helideck testbed for floating structures based on a Stewart-Gough platform

A parallel robot testbed based on Stewart-Gough platform called Active-helideck is designed, developed and tested as a helicopter floating helideck. The objective of this testbed is to show the advantages of helicopters that use an active helideck upon landing on and taking off from ships or from offshore structures. Active-helideck compensates simulated movements of a ship at sea. The main goal of this study is to maintain the robot’s end effector (helideck) in a quasi-static position in accordance to an absolute inertial frame. Compensation is carried out through the coordinate action of its six prismatic actuators in function of an inertial measurement unit. Moreover, the simulation of the sea movement is done by a parallel robot called ship platform with three degrees of freedom. The ship platform is built with a vertical oscillation along the z axis, i.e. heave, and rotates on remaining axes, i.e. roll and pitch. Active helideck is able to compensate simulated movements by considering the ship as an inertial frame as observed in the experiment