Application of redundant robots to constrained-motion tasks

Robotica ◽  
1992 ◽  
Vol 10 (5) ◽  
pp. 397-407 ◽  
Author(s):  
Veljko Potkonjak
Keyword(s):  
Free Motion ◽  
Constrained Motion ◽  
End Effector ◽  
Redundant Robot ◽  
Redundant Robots ◽  
Passive Compliance ◽  
Two Phases ◽  
The Impact

SUMMARYThe problem of the constrained motion of robot end-effector is discussed. The redundant robot is considered, redundancy being added in order to improve robot working characteristics. In the phase of free motion towards the constraint the errors of basic non-redundant configuration are corrected by means of redundancy. During the constrained motion redundancy plays the role either of active or passive compliance. Between these two phases, the collision with the constraint occurs, and the impact can be absorbed by using redundancy.

Adaptive Motion and Force Control of Robots Performing a Complete Task

1999 ◽  
Author(s):  
Prabhakar R. Pagilla ◽  
Biao Yu
Keyword(s):  
Force Control ◽  
Position Control ◽  
Active Phase ◽  
Free Motion ◽  
Constrained Motion ◽  
Control Laws ◽  
Adaptive Motion ◽  
Inactive Phase ◽  
The Impact ◽  
Three Phases

Abstract In this work, we consider adaptive motion and force control of a robot performing a complete task. By a complete task we mean that the robot desired task contains both free motion and constrained motion. Further, we also consider transition from free motion to constrained motion. We divide the motion of the robot into three phases: (i) inactive phase, where the robot is in free motion, (ii) transition phase, where the transition from free motion to constrained motion takes place, and (iii) active phase, where the robot is in constrained motion with simultaneous force and position control. Uncertainty of the constraint results in the impact of robot with the constraint surface when transition from free motion to constrained motion. We design stable control laws for the three phases that results in an efficient algorithm for robots performing a complete task. Extensive experiments are conducted to show the validity of the proposed control designs.

Awareness-Raising in the TEFL Phonology Classroom

2004 ◽  
Vol 145-146 ◽  
pp. 219-268 ◽  
Author(s):  
Lawrence Zhang
Keyword(s):  
Native Speaker ◽  
Psychological Needs ◽  
British English ◽  
Linguistic Imperialism ◽  
Teacher Student ◽  
Suprasegmental Features ◽  
Discourse Intonation ◽  
Awareness Raising ◽  
Two Phases ◽  
The Impact

This paper reports on two phases of a study of a group of advanced TEFL (teachers-of-English-as-a-foreign-language) students. To raise their awareness of the importance of discourse intonation while they were receiving teacher training, this study focuses on examining their sociocultural and psychological inclinations in the choice of phonological models. The first phase is an exploration of their attitudes toward, a native-speaker variety (British English) and a nonnative (Chinese EFL-speaker) variety of English pronunciation and intonation. The second reports on a didactic intervention study of the impact of activities that engaged the students in the awareness-raising of the importance of suprasegmental features, especially discourse intonation, on self-perceptions of their efficacy and confidence in communication. The results showed a systematic pattern of participant endorsement for a native-speaker model and a clear improvement in theIr perceptions of the importance of suprasegmental features of standard English because of teacher-student co-construction of meaning through interactive awareness-raising activities. The findings are discussed with reference to the students' sociocultural and psychological needs in TEFL training, particularly with reference to recent academic discourse on the issue of “linguistic imperialism” (Canagarajah, 1999; Phillipson, 1992, 1996) and ElL in pedagogy (Jenkins, 1998, 2002) and their wider implications in typical EFL contexts.

scholarly journals Phase transitions from the fifth dimension

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Kaustubh Agashe ◽  
Peizhi Du ◽  
Majid Ekhterachian ◽  
Soubhik Kumar ◽  
Raman Sundrum
Keyword(s):  
Bubble Dynamics ◽  
Effective Field ◽  
Bubble Nucleation ◽  
Thin Wall ◽  
Black Brane ◽  
Composite Higgs ◽  
Fifth Dimension ◽  
Two Phases ◽  
Holographic Description ◽  
The Impact

Abstract We study the cosmological transition of 5D warped compactifications, from the high-temperature black-brane phase to the low-temperature Randall-Sundrum I phase. The transition proceeds via percolation of bubbles of IR-brane nucleating from the black-brane horizon. The violent bubble dynamics can be a powerful source of observable stochastic gravitational waves. While bubble nucleation is non-perturbative in 5D gravity, it is amenable to semiclassical treatment in terms of a “bounce” configuration interpolating between the two phases. We demonstrate how such a bounce configuration can be smooth enough to maintain 5D effective field theory control, and how a simple ansatz for it places a rigorous lower-bound on the transition rate in the thin-wall regime, and gives plausible estimates more generally. When applied to the Hierarchy Problem, the minimal Goldberger-Wise stabilization of the warped throat leads to a slow transition with significant supercooling. We demonstrate that a simple generalization of the Goldberger-Wise potential modifies the IR-brane dynamics so that the transition completes more promptly. Supercooling determines the dilution of any (dark) matter abundances generated before the transition, potentially at odds with data, while the prompter transition resolves such tensions. We discuss the impact of the different possibilities on the strength of the gravitational wave signals. Via AdS/CFT duality the warped transition gives a theoretically tractable holographic description of the 4D Composite Higgs (de)confinement transition. Our generalization of the Goldberger-Wise mechanism is dual to, and concretely models, our earlier proposal in which the composite dynamics is governed by separate UV and IR RG fixed points. The smooth 5D bounce configuration we introduce complements the 4D dilaton/radion dominance derivation presented in our earlier work.

Development of an End-Effector for Mitigation of Collisions

2021 ◽  
Author(s):  
Domenico Tommasino ◽  
Matteo Bottin ◽  
Giulio Cipriani ◽  
Alberto Doria ◽  
Giulio Rosati
Keyword(s):  
Numerical Simulations ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Contact Forces ◽  
Design Parameters ◽  
End Effector ◽  
Linear Behavior ◽  
Stable Mechanism ◽  
Robot Tasks ◽  
The Impact

Abstract In robotics the risk of collisions is present both in industrial applications and in remote handling. If a collision occurs, the impact may damage both the robot and external equipment, which may result in successive imprecise robot tasks or line stops, reducing robot efficiency. As a result, appropriate collision avoidance algorithms should be used or, if it is not possible, the robot must be able to react to impacts reducing the contact forces. For this purpose, this paper focuses on the development of a special end-effector that can withstand impacts and is able to protect the robot from impulsive forces. The novel end-effector is based on a bi-stable mechanism that decouples the dynamics of the end-effector from the dynamics of the robot. The intrinsically non-linear behavior of the end-effector is investigated with the aid of numerical simulations. The effect of design parameters and the operating conditions are analyzed and the interaction between the functioning of the bi-stable mechanism and the control system is studied. In particular, the effect of the mechanism in different scenarios characterized by different robot velocities is shown. Results of numerical simulations assess the validity of the proposed end-effector, which can lead to large reductions in impact forces.

scholarly journals Comparative study on the redundancy of mobile single- and dual-arm robots

2016 ◽  
Vol 13 (6) ◽  
pp. 172988141666678
Author(s):  
Hongxing Wang ◽  
Ruifeng Li ◽  
Yunfeng Gao ◽  
Chuqing Cao ◽  
Lianzheng Ge
Keyword(s):  
Rate Control ◽  
Control Algorithm ◽  
Redundant Robot ◽  
Motion Models ◽  
Redundant Robots ◽  
Operational Space ◽  
Rate Control Algorithm ◽  
Simulation Results ◽  
Dual Arm Robot ◽  
Dual Arm

A whole resolved motion rate control algorithm designed for mobile dual-arm redundant robots is presented in this article. Based on this algorithm, the end-effector movements of the dual arms of the mobile dual-arm redundant robot can be decomposed into the movements of the two driving wheels of the differential driving platform and the movements of the dual-arm each joint of this robot harmoniously. The influence of the redundancies of the single- and dual-arm robots on the operation based on the fixed- and differential-driving platforms, which are then based on the whole resolved motion rate control algorithm, is studied after building their motion models. Some comparisons are made to show the advantages of this algorithm on the entire modeling of the complicated robotic system and the influences of the redundancy. First, the comparison of the simulation results between the fixed single-arm robot and the mobile single-arm robot is presented. Second, a comparison of the simulation results between the mobile single-arm robot and the mobile dual-arm robots is shown. Compared with the mobile single-arm robot and the fixed dual-arm robot based on this algorithm, the mobile dual-arm robot has more redundancy and can simultaneously track and operate different objects. Moreover, the mobile dual-arm redundant robot has better smoothness, more flexibility, larger operational space, and more harmonious cooperation between the two arms and the differential driving platform during the entire mobile operational process.

scholarly journals Surging virtual reference services: COVID-19 a game changer

2021 ◽  
Vol 82 (3) ◽  
pp. 106
Author(s):  
Marie L. Radford ◽  
Laura Costello ◽  
Kaitlin Montague
Keyword(s):  
Academic Library ◽  
The United States ◽  
User Interactions ◽  
Virtual Reference ◽  
Longitudinal Surveys ◽  
Reference Services ◽  
Key Points ◽  
Academic Librarian ◽  
Two Phases ◽  
The Impact

In March 2020, academic libraries across the United States closed and sent everyone home, some destined to not reopen for months. University offices closed. Classes were moved online. Suddenly, librarians and staff pivoted to working from home and to all remote services, without time for planning logistics or training. To study the impact of this extraordinary and sweeping transition on virtual reference services (VRS), we conducted a major study of academic library responses to the pandemic that focused on librarian perceptions of how services and relationships with users morphed during this COVID-19 year.Academic librarians rallied to our call, and we collected a total of 300 responses to two longitudinal surveys launched at key points during the pandemic. Data collection focused on two phases in 2020: 1) shutdown and immediate aftermath (mid-March to July), and 2) fall ramp up and into the semester (August to December). Via Zoom, we also interviewed 28 academic librarian leaders (e.g., heads of reference and/or VRS, associate directors for User Services) from September to November. Surveys and interviews centered on adaptations and innovations to reference services, especially VRS and perceptions of changes in user interactions.

Dynamics of redundant robots – inverse solutions

Robotica ◽  
1986 ◽  
Vol 4 (4) ◽  
pp. 263-267 ◽  
Author(s):  
Ronald L. Huston ◽  
Timothy P. King
Keyword(s):  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Solution Algorithm ◽  
Redundant Robot ◽  
Redundant Robots ◽  
Revolute Joints ◽  
Inverse Kinematics Problem ◽  
Inverse Solutions ◽  
Natural Dynamics ◽  
Least Energy

SUMMARYThe dynamics of “simple, redundant robots” are developed. A “redundant” robot is a robot whose degrees of freedom are greater than those needed to perform a given kinetmatic task. A “simple” robot is a robot with all joints being revolute joints with axes perpendicular or parallel to the arm segments. A general formulation, and a solution algorithm, for the “inverse kinematics problem” for such systems, is presented. The solution is obtained using orthogonal complement arrays which in turn are obtained from a “zero-eigenvalues” algorithm. The paper concludes with an assertion that this solution, called the “natural dynamics solution,” is optimal in that it requires the least energy to drive the robot.

scholarly journals Physics-Based Simulations of Flow and Fire Development Downstream of a Canopy

Atmosphere ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 683
Author(s):  
Gilbert Accary ◽  
Duncan Sutherland ◽  
Nicolas Frangieh ◽  
Khalid Moinuddin ◽  
Ibrahim Shamseddine ◽  
...  
Keyword(s):  
Turbulent Flow ◽  
Forest Canopy ◽  
Prescribed Burning ◽  
Second Phase ◽  
Flow Conditions ◽  
Developed Turbulence ◽  
Large Eddy ◽  
Long Time ◽  
Two Phases ◽  
The Impact

The behavior of a grassland fire propagating downstream of a forest canopy has been simulated numerically using the fully physics-based wildfire model FIRESTAR3D. This configuration reproduces quite accurately the situation encountered when a wildfire spreads from a forest to an open grassland, as can be the case in a fuel break or a clearing, or during a prescribed burning operation. One of the objectives of this study was to evaluate the impact of the presence of a canopy upstream of a grassfire, especially the modifications of the local wind conditions before and inside a clearing or a fuel break. The knowledge of this kind of information constitutes a major element in improving the safety conditions of forest managers and firefighters in charge of firefighting or prescribed burning operations in such configurations. Another objective was to study the behavior of the fire under realistic turbulent flow conditions, i.e., flow resulting from the interaction between an atmospheric boundary layer (ABL) with a surrounding canopy. Therefore, the study was divided into two phases. The first phase consisted of generating an ABL/canopy turbulent flow above a pine forest (10 m high, 200 m long) using periodic boundary conditions along the streamwise direction. Large Eddy Simulations (LES) were carried out for a sufficiently long time to achieve a quasi-fully developed turbulence. The second phase consisted of simulating the propagation of a surface fire through a grassland, bordered upstream by a forest section (having the same characteristics used for the first step), while imposing the turbulent flow obtained from the first step as a dynamic inlet condition to the domain. The simulations were carried out for a wind speed that ranged between 1 and 12 m/s; these values have allowed the simulations to cover the two regimes of propagation of surfaces fires, namely plume-dominated and wind-driven fires.

Sign in / Sign up

Export Citation Format

Share Document