Position Kinematics of a Three-Limbed Mixed Mechanism

1994 ◽  
Vol 116 (3) ◽  
pp. 924-929 ◽  
Author(s):  
M. Husain ◽  
K. J. Waldron
Keyword(s):  
Rational Design ◽  
Industrial Robots ◽  
Parallel Structure ◽  
General Mechanism ◽  
Static Characteristics ◽  
Serial Chain ◽  
Hybrid Mechanism ◽  
Parallel Structures ◽  
Industrial Use ◽  
Mixed Mechanism

Although robotics has traditionally focused on the serial chain structures typical of industrial robots, fully parallel structures such as the Stewart Platform have also found considerable industrial use. Actively coordinated mechanisms which have combinations of serial and parallel characteristics have been practically employed, and can be expected to become more important in the future. There has been very little study of the kinematic and static characteristics of these mechanisms which have combinations of the characteristics of fully serial and fully parallel structures. This work addresses the direct and inverse position kinematics of such a hybrid mechanism with combination of serial and parallel structure which has multiple, actively controlled actuators. While not the most general possible configuration, this particular case does include many important features of the general mechanism, and the solution obtained gives useful insight for developing a general theory of forward and inverse kinematics which will be equally applicable to serial, parallel and combination structures. Such a theory is necessary for rational design of hardware and software for such systems.

Position Kinematics of a Mixed Mechanism

1992 ◽  
Author(s):  
Muqtada Husain ◽  
Kenneth J. Waldron
Keyword(s):  
Rational Design ◽  
Industrial Robots ◽  
Parallel Structure ◽  
General Mechanism ◽  
Static Characteristics ◽  
Serial Chain ◽  
Hybrid Mechanism ◽  
Parallel Structures ◽  
Industrial Use ◽  
Mixed Mechanism

Abstract Although robotics has traditionally focused on the serial chain structures typical of industrial robots, fully parallel structures such as the Stewart Platform have also found considerable industrial use. Actively coordinated mechanisms which have combinations of serial and parallel characteristics have been practically employed, and can be expected to become more important in the future. There has been very little study of the kinematic and static characteristics of these mechanisms which have combinations of the characteristics of fully serial and fully parallel structures. This work addresses the direct and inverse position kinematics of such a hybrid mechanism with combination of serial and parallel structure which has multiple, actively controlled actuators. While not the most general possible configuration, this particular case does include many important features of the general mechanism, and the solution obtained gives useful insight for developing a general theory of forward and inverse kinematics which will be equally applicable to serial, parallel and combination structures. Such a theory is necessary for rational design of hardware and software for such systems.

scholarly journals THE DIFFICULTIES FACED BY THE STUDENTS IN ANSWERING THE WRITTEN EXPRESSION SECTION OF THE TOEFL TEST

2018 ◽  
Vol 3 (2) ◽  
Author(s):  
Mainar Fitri
Keyword(s):  
Quantitative Research ◽  
Written Expression ◽  
Parallel Structure ◽  
Study Program ◽  
Verb Agreement ◽  
The Third ◽  
Parallel Structures ◽  
Passive Verbs ◽  
Passing Grade

TOEFL test is one of the requirements for the students of English Study Program FKIP UNRI to finish their study at S1 Degree.  Based on the researcher’s observation, most of the students did not pass the TOEFL Test.  The students followed the test for several times till they reached the passing grade. It seemed that the students got difficulties in answering the TOEFL Test. So, in this research the researcher focused on analyzing the students’ difficulties in answering the Written Expression section of the TOEFL test.  The aims of this research were to identify the categories of items in the Written Expression section of the TOEFL test which were difficult for the third-year students of English Study Program FKIP-UNRI . and to identify which categories of items that were easy for the students. This research was a quantitative research. The researcher analyzed the categories of items tested in TOEFL test, especially in the Written Expression section. There were 12 categories of items tested in the Written Expression section of the TOEFL test based on Longman Preparation Course for the TOEFL Test by Deborah Phillips (2000: 144-221). The categories consisted of subject-verb agreement, parallel structure, comparative and superlative, the use of the verbs, the forms of the verbs, passive verbs, nouns, pronouns, adjectives and adverbs, articles, prepositions and usages   The result of the research showed that there were 10 categories of items that were difficult for the students. The categories were parallel structures, comparatives and superlatives, the use of the verbs, passive verbs, nouns, pronouns, adjectives and adverbs, articles, prepositions and usages.  While the categories of items which were considered easy for the students were subject-verb agreement and the forms of the verbs. So, in general, the students got difficulties in answering the Written Expression section of the TOEFL test.

scholarly journals Design and Analysis of a Flexible, Elastic, and Rope-Driven Parallel Mechanism for Wrist Rehabilitation

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Zaixiang Pang ◽  
Tongyu Wang ◽  
Junzhi Yu ◽  
Shuai Liu ◽  
Xiyu Zhang ◽  
...  
Keyword(s):  
Inverse Kinematics ◽  
Parallel Mechanism ◽  
Inverse Kinematic ◽  
Parallel Structure ◽  
Flexible Joints ◽  
Rehabilitation Robots ◽  
Hybrid Mechanism ◽  
Compression Spring ◽  
Moving Platform

This paper proposes a bionic flexible wrist parallel mechanism to simulate human wrist joints, which is characterized by a rope-driven, compression spring-supported hybrid mechanism. Specifically, to realize the movement of the wrist mechanism, a parallel structure is adopted to support the mobile platform and is controlled by a cable, which plays the role of wrist muscles. Because the compression spring is elastic, it is difficult to directly solve inverse kinematics. To address this problem, the external force acting on the moving platform is firstly equivalent to the vector force and torque at the center of the moving platform. Then, based on inverse kinematic and static analyses, the inverse motion of the robot model can be solved according to the force and torque balance conditions and the lateral spring bending equation of the compression spring. In order to verify the proposed method, kinematics, statics, and parallel mechanism workspace are further analyzed by the software MATLAB. The obtained results demonstrate the effectiveness and feasibility of the designed parallel mechanism. This work offers new insights into the parallel mechanism with flexible joints in replicating the movements of the human wrist, thus promoting the development of rehabilitation robots and rope-driven technology to some extent.

A Class of Parallel Manipulators Based on Kinematically Simple Branches

1994 ◽  
Vol 116 (3) ◽  
pp. 908-914 ◽  
Author(s):  
R. P. Podhorodeski ◽  
K. H. Pittens
Keyword(s):  
Parallel Manipulators ◽  
Parallel Structure ◽  
End Effector ◽  
Forward Displacement ◽  
Parallel Class ◽  
Serial Chain ◽  
Order Polynomial ◽  
Six Dof ◽  
Actuated Joints ◽  
Chain Branch

Parallel manipulators consisting of serial branches acting in parallel on a common end effector are examined. All nonredundant, six DOF manipulators corresponding to this in-parallel class of structures are enumerated. A specific in-parallel structure, three branches with two actuated joints per branch (3–2,2,2), is chosen as most promising based upon performance considerations. A class of kimematically simple (KS) serial-chain branch joint layouts suitable for the chosen in-parallel structure is defined. Arguments based upon kinematic equivalency of the branches and mobility of the assembled in-parallel manipulator chain are used to show that there exist only five unique branch joint-layouts belonging to the KS class. It is demonstrated that the solution to the inverse displacement problem for in-parallel manipulators based on the KS branches can be expressed in a closed form. Furthermore, the 3–2,2,2 in-parallel manipulators are shown to belong to a family of manipulators whose forward displacement solutions can be resolved through roots of a 16th order polynomial.

Helical Kirigami-Enabled Centimeter-Scale Worm Robot With Shape-Memory-Alloy Linear Actuators

2015 ◽  
Vol 7 (2) ◽  
Author(s):  
Ketao Zhang ◽  
Chen Qiu ◽  
Jian S. Dai
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Degrees Of Freedom ◽  
Screw Theory ◽  
Kinematic Model ◽  
Parallel Structure ◽  
Geometrical Parameters ◽  
Parallel Structures ◽  
Complete Procedure ◽  
Motion Characteristics

The wormlike robots are capable of imitating amazing locomotion of slim creatures. This paper presents a novel centimeter-scale worm robot inspired by a kirigami parallel structure with helical motion. The motion characteristics of the kirigami structure are unravelled by analyzing the equivalent kinematic model in terms of screw theory. This reveals that the kirigami parallel structure with three degrees-of-freedom (DOF) motion is capable of implementing both peristalsis and inchworm-type motion. In light of the revealed motion characteristics, a segmented worm robot which is able to imitate contracting motion, bending motion of omega shape and twisting motion in nature is proposed by integrating kirigami parallel structures successively. Following the kinematic and static characteristics of the kirigami structure, actuation models are explored by employing the linear shape-memory-alloy (SMA) coil springs and the complete procedure for determining the geometrical parameters of the SMA coil springs. Actuation phases for the actuation model with two SMA springs are enumerated and with four SMA springs are calculated based on the Burnside's lemma. In this paper, a prototype of the worm robot with three segments is presented together with a paper-made body structure and integrated SMA coil springs. This centimeter-scale prototype of the worm robot is lightweight and can be used in confined environments for detection and inspection. The study presents an interesting approach of integrating SMA actuators in kirigami-enabled parallel structures for the development of compliant and miniaturized robots.

An Origami Parallel Structure Integrated Deployable Continuum Robot

2015 ◽  
Author(s):  
Ketao Zhang ◽  
Chen Qiu ◽  
Jian S. Dai
Keyword(s):  
Translational Motion ◽  
Kinematic Model ◽  
Parallel Structure ◽  
Continuum Robots ◽  
Helical Springs ◽  
Parallel Structures ◽  
Driven System ◽  
Continuum Robot ◽  
Motion Characteristics ◽  
Novel Design

This paper presents a novel design for continuum robots in light of origami inspired folding techniques. The work of the present paper starts from design of a crease pattern, which consists of two triangular bases and three waterbomb bases, and folding process for creating an origami parallel structure in 3D from the crease pattern in 2D. Mapping the origami parallel structure to an equivalent kinematic model, the motion characteristics of the origami structure are unraveled in terms of kinematic principles. The analysis reveals that mixed rotational and translational motion of the origami parallel structure enables both axial contraction and bending motion. A novel multi-section continuum robot with integrated origami parallel structures and bias elements is then proposed to imitate not only bending motion but also contraction of continuum apparatus in nature. According to kinematics of the proposed continuum robot and features of the embedded helical spring in each module, three actuation schemes and their enabled two typical working phases with a tendon driven system are presented. A prototype of the continuum robot with six modules connected in serial is produced and tested. The functionality of the proposed continuum robot by integrating the origami parallel structure as its skeleton and helical springs as the compliant backbone is validated by the preliminary experimental results.

PRINCIPLES OF BUILDING OF AUTOMATIC MEASURING VOLUME OF AGRICULTURAL PRODUCTS AND MATERIALS DEVICES

1970 ◽  
pp. 68-71
Author(s):  
A. M. Sedov
Keyword(s):  
Free Volume ◽  
Rational Design ◽  
Experimental Studies ◽  
Agricultural Products ◽  
Static Characteristics ◽  
Basic Principles ◽  
Tuning Parameters ◽  
Quantitative Properties ◽  
Automation Tools ◽  
Analytical Expressions

Many qualitative and quantitative properties of products, materials, and parameters of technological processes in agricultural production and other sectors of the economy are characterized by volume indicators. Based on analytical and experimental studies a unified system of automatic volumetric meters has been developed taking into account three basic principles: “discharge” of a gas-filled chamber to a measuring capacity; generation of a linearly increasing pneumatic signal in the free volume of the measuring capacitance; digital quantization of the free volume of the measuring capacitance. The system is unified by the elemental base, power levels and output signals and allows you to solve the main tasks of measuring, monitoring and signaling the volume of most agricultural products and materials; create fundamentally new automation tools from standardized units on the basis of the volumetric module by adding other modules (weighting, computing, differentiating, comparisons, etc.). Analytical expressions of the static characteristics of the developed volumes are obtained experimental studies have confirmed their reliability. The rational design and tuning parameters of the devices are determined taking into account the specifics of the physical properties of agricultural products and materials.

A new methodology for the determination of the workspace of six-DOF redundant parallel structures actuated by nine wires

Robotica ◽  
2006 ◽  
Vol 25 (1) ◽  
pp. 113-120 ◽  
Author(s):  
Carlo Ferraresi ◽  
Marco Paoloni ◽  
Francesco Pescarmona
Keyword(s):  
Degrees Of Freedom ◽  
New Method ◽  
Parallel Structure ◽  
Graphical Form ◽  
Six Degrees Of Freedom ◽  
Parallel Structures ◽  
Six Dof ◽  
Force Reflection ◽  
Master Device

The WiRo-6.3 is a six-degrees of freedom (six-DOF) robotic parallel structure actuated by nine wires, whose characteristics have been thoroughly analyzed in previous papers in reference. It is thought to be a master device for teleoperation; thus, it is moved by an operator through a handle and can convey a force reflection on the operator's hand. A completely new method for studying the workspace of this device, and of virtually any nine-wire parallel structure actuated by wire is presented and discussed, and its results are given in a graphical form.

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