scholarly journals Performance-Based Design of the CRS-RRC Schoenflies-Motion Generator

Robotics ◽  
2018 ◽  
Vol 7 (3) ◽  
pp. 55
Author(s):  
Raffaele Di Gregorio ◽  
Mattia Cattai ◽  
Henrique Simas
Keyword(s):  
Degrees Of Freedom ◽  
Rotation Axis ◽  
Dimensional Space ◽  
Design Procedure ◽  
Optimization Procedure ◽  
Conveyor Belt ◽  
Pick And Place ◽  
Displacement Group ◽  
4 Degrees Of Freedom ◽  
Motion Generator

Rigid-body displacements obtained by combining spatial translations and rotations around axes whose direction is fixed in the space are named Shoenflies’ motions. They constitute a 4-dimensional (4-D) subgroup, named Shoenflies’ subgroup, of the 6-D displacement group. Since the set of rotation-axis’ directions is a bi-dimensional space, the set of Shoenflies’ subgroups is a bi-dimensional space, too. Many industrial manipulations (e.g., pick-and-place on a conveyor belt) require displacements that belong to only one Schoenflies’ subgroup and can be accomplished by particular 4-degrees-of-freedom (4-DOF) manipulators (Shoenflies-motion generators (SMGs)). The first author has recently proposed a novel parallel SMG of type CRS-RRC. Such SMG features a single-loop architecture with actuators on the base and a simple decoupled kinematics. Here, firstly, an organic review of the previous results on this SMG is presented; then, its design is addressed by considering its kinetostatic performances. The adopted design procedure optimizes two objective functions, one (global conditioning index (GCI)) that measures the global performance and the other (CImin) that evaluates the worst local performance in the useful workspace. The results of this optimization procedure are the geometric parameters’ values that make the studied SMG have performances comparable with those of commercial SMGs. In addition, a realistic 3D model that solves all the manufacturing doubts with simple and cheap solutions is presented.

Position analysis, singularity loci and workspace of a novel 2PRPU Schoenflies-motion generator

Robotica ◽  
2018 ◽  
Vol 37 (1) ◽  
pp. 141-160 ◽  
Author(s):  
Henrique Simas ◽  
Raffaele Di Gregorio
Keyword(s):  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
End Effector ◽  
Single Loop ◽  
Position Analysis ◽  
Serial Robots ◽  
Pick And Place ◽  
Displacement Group ◽  
Motion Generator

SUMMARYPick-and-place applications need to perform rigid body displacements that combine translations along three independent directions and rotations around one fixed direction (Schoenflies motions). Such displacements constitute a four-dimensional (4-D) subgroup (Schoenflies subgroup) of the 6-D displacement group. The four-degrees of freedom (dof) manipulators whose end effector performs only Schoenflies motions are named Schoenflies-motion generators (SMGs). The most known SMGs are the serial robots named SCARA. In the literature, parallel manipulators (PMs) have also been proposed as SMGs. Here, a novel single-loop SMG of type 2PRPU is studied. Its position analysis, singularity loci and workspace are addressed to provide simple analytic and geometric tools that are useful for the design. The proposed single-loop SMG is not overconstrained, its actuators are on or near the base and its end effector can perform a complete rotation. These features solve the main drawbacks that parallel SMG architectures have in general and make the proposed SMG a valid design alternative.

Kinematics of a Particular 3T1R Parallel Manipulator of Type 2PRPU

2017 ◽  
Author(s):  
Henrique Simas ◽  
Raffaele Di Gregorio
Keyword(s):  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
Industrial Applications ◽  
End Effector ◽  
Serial Robots ◽  
Fixed Direction ◽  
Pick And Place ◽  
Displacement Group ◽  
4 Degrees Of Freedom

Schoenflies-motion generators (SMGs) are 4-degrees-of-freedom (dof) manipulators whose end effector can perform translations along three independent directions, and rotations around one fixed direction (Schoenflies motions). Such motions constitute the 4-dimensional (4-D) Schoenflies subgroup of the 6-D displacement group. The most known SMGs are the serial robots named SCARA. Pick-and-place tasks are typical industrial applications that SMGs can accomplish. In the literature, 3T1R parallel manipulators (PMs) have been also proposed as SMGs. Here, a somehow novel 3T1R PM is presented and studied. Its finite and instantaneous kinematics are analyzed in depth, and analytic and geometric tools that are useful for its design are presented. The proposed SMG has a single-loop not-overconstrained architecture with actuators on or near the base and can make the end effector perform a complete rotation.

A symmetric parallel Schönflies-motion manipulator for pick-and-place operations

Robotica ◽  
2011 ◽  
Vol 29 (6) ◽  
pp. 853-862 ◽  
Author(s):  
O. Altuzarra ◽  
B. Şandru ◽  
Ch. Pinto ◽  
V. Petuya
Keyword(s):  
Group Theory ◽  
Kinematic Analysis ◽  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Mechanical Device ◽  
End Effector ◽  
Pick And Place ◽  
Schönflies Motion ◽  
Motion Generator ◽  
Two Alternatives

SUMMARYThis paper presents a new symmetric parallel Schönflies-motion generator. The design is an evolution of a previous robot with linear inputs. The complete kinematic analysis of the 4-degree-of-freedom (dof) parallel manipulator is presented. The degrees of freedom are obtained from the Group Theory, the direct and inverse position problems are solved obtaining the manipulator's workspace, and the Jacobian analysis is presented. Then the isotropic configurations of the manipulator are discussed and the local dexterity map within the workspace is produced. Finally, two alternatives of a rotational mechanical device, which will increase the angular end-effector range, are proposed.

scholarly journals THE DESIGN OF AN INNOVATIVE LARGE SCALE SCHÖNFLIES-MOTION GENERATOR

2011 ◽  
Author(s):  
Alexei Morozov ◽  
Jorge Angeles
Keyword(s):  
Degrees Of Freedom ◽  
Large Scale ◽  
Design Procedure ◽  
Design Specifications ◽  
Single Structure ◽  
Fixed Orientation ◽  
Schönflies Motion ◽  
Main Components ◽  
Motion Generator ◽  
Selection Of

The design of a novel Schönflies-Motion Generator (SMG) is the focus of the paper. Schönflies motions are characterized by four degrees of freedom three independent translations and one rotation about one axis of fixed orientation. The two driving modules of the manipulator are based on differential transmissions. Then, the design philosophy and the layout of the SMG are discussed, along with the design procedure. This procedure includes: (i) part-modelling and visualization, with animation of the device; (ii) evaluation of the main parameters and the characteristics of the different structural realizations, as well as the selection of one single structure meeting best the design specifications; (iii) the design of the main components for the selected variant of the structure; and (iv) the production of detailed manufacturing drawings. Further results of structural and modal analyses of the SMG are considered, while the link geometry is defined based on the design specifications.

On the Design of a 4 Degrees-of-freedom Pick and Place Cable Suspended Parallel Manipulator

2017 ◽  
Vol 6 (4) ◽  
pp. 286
Author(s):  
F. J. Castillo-Garcia ◽  
P. Rea ◽  
A. Gonzalez-Rodriguez ◽  
E. Ottaviano
Keyword(s):  
Control Strategy ◽  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Parallel Robot ◽  
Medium Size ◽  
Pd Controller ◽  
Positioning Accuracy ◽  
Pick And Place ◽  
And Control ◽  
4 Degrees Of Freedom

This paper proposes the design and control strategy for a four degrees-of-freedom spatial cable-suspended parallel robot for pick and place operations. Pick and place is a repetitive task requiring payload changes for the movement to pick-up the object, and the movement to the nal pose to release the manipulated object. In this paper, a new robust control strategy has been proposed, together with proper trajectories for the required operation. The control strategy consists on the system decoupling and linearization by means of a feedforward term and a cascade PD controller. The main advantage of the proposed solution is that its design can be scalable in size spanning from centimeters to meters with a relatively good positioning accuracy. Finally, simulations are reported to show the overall performances of the proposed con guration for pick and place operations with a medium size manipulator.

The motion of a lunar orbiter

1966 ◽  
Vol 25 ◽  
pp. 373
Author(s):  
Y. Kozai
Keyword(s):  
Degrees Of Freedom ◽  
Dimensional Space ◽  
Artificial Satellite ◽  
Equations Of Motion ◽  
Triaxial Ellipsoid ◽  
The Moon ◽  
Secular Motion ◽  
The Earth ◽  
Close Satellite ◽  
The Mean

The motion of an artificial satellite around the Moon is much more complicated than that around the Earth, since the shape of the Moon is a triaxial ellipsoid and the effect of the Earth on the motion is very important even for a very close satellite.The differential equations of motion of the satellite are written in canonical form of three degrees of freedom with time depending Hamiltonian. By eliminating short-periodic terms depending on the mean longitude of the satellite and by assuming that the Earth is moving on the lunar equator, however, the equations are reduced to those of two degrees of freedom with an energy integral.Since the mean motion of the Earth around the Moon is more rapid than the secular motion of the argument of pericentre of the satellite by a factor of one order, the terms depending on the longitude of the Earth can be eliminated, and the degree of freedom is reduced to one.Then the motion can be discussed by drawing equi-energy curves in two-dimensional space. According to these figures satellites with high inclination have large possibilities of falling down to the lunar surface even if the initial eccentricities are very small.The principal properties of the motion are not changed even if plausible values ofJ3andJ4of the Moon are included.This paper has been published in Publ. astr. Soc.Japan15, 301, 1963.

scholarly journals Design, Fabrication, and Testing of a Novel 3D 3-Fingered Electrothermal Microgripper with Multiple Degrees of Freedom

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 444
Author(s):  
Guoning Si ◽  
Liangying Sun ◽  
Zhuo Zhang ◽  
Xuping Zhang
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Polyimide Film ◽  
Zebrafish Embryos ◽  
Multiple Degrees Of Freedom ◽  
Electrothermal Actuator ◽  
3D Space ◽  
Pick And Place

This paper presents the design, fabrication, and testing of a novel three-dimensional (3D) three-fingered electrothermal microgripper with multiple degrees of freedom (multi DOFs). Each finger of the microgripper is composed of a V-shaped electrothermal actuator providing one DOF, and a 3D U-shaped electrothermal actuator offering two DOFs in the plane perpendicular to the movement of the V-shaped actuator. As a result, each finger possesses 3D mobilities with three DOFs. Each beam of the actuators is heated externally with the polyimide film. The durability of the polyimide film is tested under different voltages. The static and dynamic properties of the finger are also tested. Experiments show that not only can the microgripper pick and place microobjects, such as micro balls and even highly deformable zebrafish embryos, but can also rotate them in 3D space.

scholarly journals Development and assessment of a telesonography system for musculoskeletal imaging

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Mohammed Obaid ◽  
Qianwei Zhang ◽  
Scott J. Adams ◽  
Reza Fotouhi ◽  
Haron Obaid
Keyword(s):  
Degrees Of Freedom ◽  
Ultrasound Images ◽  
Ultrasound Probe ◽  
Rural And Remote ◽  
Significant Delay ◽  
Remote Communities ◽  
Internet Connection ◽  
Good For ◽  
4 Degrees Of Freedom

Abstract Background Telesonography systems have been developed to overcome barriers to accessing diagnostic ultrasound for patients in rural and remote communities. However, most previous telesonography systems have been designed for performing only abdominal and obstetrical exams. In this paper, we describe the development and assessment of a musculoskeletal (MSK) telesonography system. Methods We developed a 4-degrees-of-freedom (DOF) robot to manipulate an ultrasound probe. The robot was remotely controlled by a radiologist operating a joystick at the master site. The telesonography system was used to scan participants’ forearms, and all participants were conventionally scanned for comparison. Participants and radiologists were surveyed regarding their experience. Images from both scanning methods were independently assessed by an MSK radiologist. Results All ten ultrasound exams were successfully performed using our developed MSK telesonography system, with no significant delay in movement. The duration (mean ± standard deviation) of telerobotic and conventional exams was 4.6 ± 0.9 and 1.4 ± 0.5 min, respectively (p = 0.039). An MSK radiologist rated quality of real-time ultrasound images transmitted over an internet connection as “very good” for all telesonography exams, and participants rated communication with the radiologist as “very good” or “good” for all exams. Visualisation of anatomic structures was similar between telerobotic and conventional methods, with no statistically significant differences. Conclusions The MSK telesonography system developed in this study is feasible for performing soft tissue ultrasound exams. The advancement of this system may allow MSK ultrasound exams to be performed over long distances, increasing access to ultrasound for patients in rural and remote communities.

scholarly journals Optimizing the structure and movement of a robotic bat with biological kinematic synergies

2018 ◽  
Vol 37 (10) ◽  
pp. 1233-1252 ◽  
Author(s):  
Jonathan Hoff ◽  
Alireza Ramezani ◽  
Soon-Jo Chung ◽  
Seth Hutchinson
Keyword(s):  
Principal Component Analysis ◽  
Topological Structure ◽  
Degrees Of Freedom ◽  
Dimensional Space ◽  
Principal Component ◽  
Biologically Inspired ◽  
Wing Kinematics ◽  
Wing Motion ◽  
Kinematic Synergies ◽  
Low Dimensional

In this article, we present methods to optimize the design and flight characteristics of a biologically inspired bat-like robot. In previous, work we have designed the topological structure for the wing kinematics of this robot; here we present methods to optimize the geometry of this structure, and to compute actuator trajectories such that its wingbeat pattern closely matches biological counterparts. Our approach is motivated by recent studies on biological bat flight that have shown that the salient aspects of wing motion can be accurately represented in a low-dimensional space. Although bats have over 40 degrees of freedom (DoFs), our robot possesses several biologically meaningful morphing specializations. We use principal component analysis (PCA) to characterize the two most dominant modes of biological bat flight kinematics, and we optimize our robot’s parametric kinematics to mimic these. The method yields a robot that is reduced from five degrees of actuation (DoAs) to just three, and that actively folds its wings within a wingbeat period. As a result of mimicking synergies, the robot produces an average net lift improvesment of 89% over the same robot when its wings cannot fold.

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