Effector Location Research Articles

Toward Programming a Collaborative Robot by Interacting with Its Digital Twin in a Mixed Reality Environment

In an industrial production context, when a robotic arm is assigned a new task, it must be re-programmed by specialized personnel with the necessary skills and knowledge. In addition, the robot remains offline while being re-programmed, negatively affecting productivity. Mixed reality opens up the opportunity for a production worker with no programming skills to teach a robot by interacting with the hologram of its digital twin, thus not interfering with the physical robot during re-programming. We describe the design and implementation of a mixed-reality interface to instruct trajectories for a robot end-effector by moving the hologram of its digital twin by hand. The interface supports the integrality of this interaction so that the user can configure the end effector location and orientation simultaneously. We also report a user study (n = 14) to characterize this interface in terms of usability, user experience, and estimated temporal efficiency that it can provide when programming robot trajectories.

Malleable Robots: Reconfigurable Robotic Arms With Continuum Links of Variable Stiffness

Through the implementation of reconfigurability to achieve flexibility and adaptation to tasks by morphology changes rather than by increasing the number of joints, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">malleable robots</i> present advantages over traditional serial robot arms in regards to reduced weight, size, and cost. While limited in degrees of freedom (DOF), malleable robots still provide versatility across operations typically served by systems using higher DOF than required by the tasks. In this article, we present the creation of a 2-DOF malleable robot, detailing the design of joints and malleable link, along with its modeling through forward and inverse kinematics, and a reconfiguration methodology that informs morphology changes based on end effector location—determining how the user should reshape the robot to enable a task previously unattainable. The recalibration and motion planning for making robot motion possible after reconfiguration are also discussed, and thorough experiments with the prototype to evaluate accuracy and reliability of the system are presented. Results validate the approach and pave the way for further research in the area.

A MINI-REVIEW OF KINETIC STUDY ON SHOULDER JOINT USING KUKA LIGHTWEIGHT ROBOT

A Traditional physiotherapy sessions are long and demanding, requiring a lot of effort and time from both the physiotherapist and the patient. The KUKA LWR's high work capacity and consistent precision of end- effector location and movement were utilized to solve these issues. The KUKA LWR is a seven-degrees-of- freedom robotic manipulator designed for applications in which the robot must be near the human operator. During shoulder flexion exercises, which are commonly employed in traditional physiotherapy sessions, the robotic system pretends to analyze upper-limb behaviour, specifically the shoulder complex.

Анализ сингулярных конфигураций мобильного манипулятора KUKA youBot

The article considers the KUKA youBot mobile manipulator with open software, which is intended for research and education purposes. Singular configurations of this apparatus have not been described in the literature as yet. The KUKA youBot system is a controlled platform, on which a five-axis manipulator with a grip is mounted. The platform can be moved in the horizontal plane by means of four mecanum wheels. The robot position in the absolute space is determined by eight generalized coordinates. As is known, the KUKA youBot inverse kinematics problem allows its exact analytical solution to be obtained. A rectangular Jacobi matrix for mapping the space of the robot generalized coordinates into the space of its end effector location parameters is constructed. The obtained Jacobi matrix is transformed to an equivalent echelon form by means of elementary operations. An analysis of the echelon matrix entries carried out using analytical tools has shown that, whatever the locations of the KUKA youBot system’s platform and the system arm first, fourth and fifth links, there is a singular configuration in which the robot's arm second and third links are stretched along the vertical line. In this case, the Jacobi matrix rank becomes equal to five (less than its full rank equal to six). When being in the above-mentioned singular configuration, the KUKA youBot system end effector cannot perform some of the movements the pattern of which is described in the presented paper.

Human Machine Interface Design for a 3 DoF Robot Manipulator

This paper represents a Human Machine Interface (HMI) design to control a 3 DoF robot manipulator. This manipulator has two parallelograms to make the moving platform always parallel to the ground. We used inverse kinematic analysis of the robot manipulator to control the end point location. Inverse kinematic results are verified using design parameters and end effector location. According to our algorithm, user defines the end point location from HMI, and then program solves inverse kinematics of the robot manipulator. The angles are sent to Arduino microcontroller to set the position of the servo motors. Using this HMI, the user picks and places the object in real time. The user can also give command to draw linear, circular and rectangular paths on the HMI.

Visual processing at goal and effector locations is dynamically enhanced during motor preparation

Previous theoretical and experimental works has shown that preparing to act causes enhanced perceptual processing at movement-relevant locations. Up until now, this has focused almost exclusively on the goal of an action, neglecting the role of the effector. We addressed this by measuring changes in visual processing across time during motor preparation at both goal and effector locations.We compared event related potentials (ERPs) elicited by task-irrelevant visual probe stimuli at both goal and effector locations during motor preparation. Participants were instructed to place their hands on two starting positions (effector locations) and an auditory tone instructed them to immediately move to one of two target buttons (goal locations). Probe stimuli were presented in the interval between the offset of the cue and the execution of the movement at either a goal or an effector location. Probes were presented randomly at either 100ms, 200ms or 300ms after the auditory cue.Analysis of the visual N1 ERP showed enhanced visual processing at moving vs. not-moving goal locations across all three SOAs. At effector locations, enhanced processing for the moving vs. not-moving effector was only observed during the middle (200ms) SOA.These results demonstrate, for the first time, simultaneous perceptual enhancement of goal and effector locations during motor preparation. We interpret these results as reflecting a temporally and spatially specific dynamic attentional map of the environment that adapts to maximise efficiency of movement by selectively weighting processing of multiple functional components of action in parallel.

Positional Error Estimation in Serial Link Manipulator Under Joint Clearances and Backlash

The serial link manipulators are most commonly used for industrial applications. The positional accuracy is an important specification for performance evaluation of a serial chain manipulator. The factors influencing the positional accuracy of serial link robotic manipulator includes joint clearances, and drive backlash. This paper presents method for evaluating the effect of joint error on positional accuracy of the robotic manipulator. Serial chain Two Revolute Joint (2R) planar manipulator is modeled to position the end effector in workspace. The inverse kinematic analysis under ideal joint provides the link properties for respective end effector location. Formulation for manipulator link properties under influence of the joint clearance is presented. Effect of drive backlash on positional accuracy of end effector is analyzed. Positional deviations at end effector positions over workspace are estimated. Maximum error under influence of backlash and clearances is estimated at all possible end effector positions.

Regulation of Leptin Receptor Expression in Human Polarized Caco-2/15 Cells

Leptin receptors (LEPR) are expressed in intestinal epithelial cells from the duodenum to the colon. Since their role is fundamental for the proper control of nutrient absorption, mucus secretion and mucosa renewal, the regulation of LEPR expression is for the first time investigated as a function of various potential effectors. Fully differentiated Caco-2/15 cells were incubated for 24 hours with nutrients [carbohydrates, fatty acids (FA), amino acids and sterols], hormones (leptin, insulin, hydrocortisone and epithelial growth factor), inflammatory agents (Interferon-γ, LPS, TNF-α), and PPAR agonists (rosiglitazone and WY14643). Levels of LEPR mRNA and protein expressions were measured by RT-PCR and Western blots, respectively. Long (219.1) and short (219.3) isoforms of the LEPR were detected in Caco-2/15 cells, while absence of the isoform 219.2 was noted. Their gene expression was modulated by carbohydrates, FA, PPAR agonists, biliary salts, insulin and leptin itself. On the other hand, LEPR protein expression was modulated by FA, cholesterol, biliary salts, PPAR agonists and insulin. Interestingly, the same effectors may have opposite effects on the short and the long LEPR isoforms, as well as on mRNA and protein levels. Finally, Caco-2/15 cells were found to be sensitive to the effector location, i.e. apical or basolateral compartment. Our results suggest that (i) the expression of LEPR in Caco-2/15 cell line is not constitutive; (ii) the agents present in the apical or basolateral medium have different effects on LEPR mRNA and/or protein levels; and (iii) short and long isoforms of LEPR follow different patterns of regulation.

The goal is not special: Electrophysiological evidence for the simultaneous selection of goal and effector location during motor preparation

The Premotor Theory of Attention (Rizzolatti et al., 1987, 1994) predicts that the intention to carry out an action will cause enhanced perceptual processing at the location of the action goal. This enhancement is often interpreted as a shift of spatial attention and is presumed to serve the purpose of selecting one goal amongst many distracters towards which to plan an action (selection-for-action, Allport, 1987 and Neumann, 1987). Early research on the premotor effect focused on the planning of saccades, whilst more recent work has extended the principle of enhanced processing at the goal to uni-manual movements such as reaching, pointing and grasping. Unlike saccades, however, successful planning of such uni-manual movements implies selection of an effector as well as a goal. We investigated this effect by recording participants’ EEG whilst cueing them to point to one of six targets arranged in an annular array. Visual processing was measured by reference to the size of the posterior N1 event related potential, elicited in response to task-irrelevant visual ‘probe’ stimuli presented at one of the six locations in the interval between the presentation of an auditory cue and the execution of the movement. Results showed enhanced perceptual processing simultaneously at the location of the effector and at the location of the action goal. We conclude that action planning leads to a pattern of facilitation and inhibition in perception, which achieves the selection of all action relevant locations, not just that of the goal.

Asymmetrical regulation of scavenger receptor class B type I by apical and basolateral stimuli using Caco‐2 cells

Cholesterol uptake and the mechanisms that regulate cholesterol translocation from the intestinal lumen into enterocytes remain for the most part unclear. Since scavenger receptor class B type I (SR-BI) has been suggested to play a role in cholesterol absorption, we investigated cellular SR-BI modulation by various potential effectors administered in both apical and basolateral sides of Caco-2 cells. With differentiation, Caco-2 cells increased SR-BI protein expression. Western blot analysis showed the ability of cholesterol and oxysterols in both cell compartments to reduce SR-BI protein expression. Among the n-3, n-6, and n-9 fatty acid families, only eicosapentaenoic acid was able to lower SR-BI protein expression on both sides, whereas apical alpha-linolenic acid decreased SR-BI abundance and basolateral arachidonic acid (AA) raised it. Epidermal growth factor and growth hormone, either in the apical or basolateral medium, diminished SR-BI cellular content, while insulin displayed the same effect only on the basolateral side. In the presence of proinflammatory agents (LPS, TNF-alpha, IFN-gamma), Caco-2 cells exhibited differential behavior. SR-BI was downregulated by lipopolysaccharide on both sides. Finally, WY-14643 fibrate diminished SR-BI protein expression when it was added to the apical medium. Biotinylation studies in response to selected stimuli revealed that regulatory modifications in SR-BI protein expression occurred for the most part at the apical cell surface irrespective of the effector location. Our data indicate that various effectors supplied to the apical and basolateral compartments may impact on SR-BI at the apical membrane, thus suggesting potential regulation of intestinal cholesterol absorption and distribution in various intracellular pools.

ERP effects of movement preparation on visual processing: attention shifts to the hand, not the goal

The premotor theory of attention claims that attentional shifts are triggered during response programming, regardless of which response modality is involved (Rizzolatti et al. 1994). In a series of earlier experiments we found ERP evidence for attention shifts during preparation for lifting either left or right index finger (Eimer et al. 2005; Eimer and van Velzen 2006). We also found evidence for enhanced tactile and visual, but not auditory processing at the response location during the preparation interval. In these experiments, effector location was also the response location. In the two experiments presented here we investigated whether lateralised ERP components during reaching movement preparation are triggered by effector selection or movement target selection. A second research question was whether preparation for a reaching movement induces spatially selective modulations of visual processing at the location of the effector and/or the goal location for the reaching movement.

A hybrid neural control scheme for visual-motor coordination

Visual-motor coordination, also referred to as hand-eye coordination, in the context of robotics is the process of using visual information to control a robot manipulator to reach a target point in its workspace. The task requires learning the mapping that exists between camera output and desired end effector location. Biological organisms have demonstrated their superior adaptive capabilities in motion control over present-day robotic systems. Inspired by this fact, various neural network models based on biological systems have been developed for robot control tasks. The drawback of many neural schemes to tackle visual-motor control problems is that of a long training period. We suggest an approach using Kohonen's self-organizing scheme to learn this hand-eye coordination problem in reduced time with high accuracy. Our approach has also been compared with a conventional calibration-based algorithm. These schemes have been implemented in real time on a CRS PLUS robot arm. Experimental results show that the proposed neural scheme is on an average 10 times faster in training compared to similar neural approaches existing in the literature. This speed is also comparable to the conventional algorithm and is more accurate.

Robot kinematics—II. Analytical solution of the inverse equations of closure

Part II of this paper shows that analytical solutions to the problem of inverse closure in a robot manipulator, may be derived directly from the graphical considerations of Part I. The work expands on the methods outlined by Hunt[1], and resolves ambiguities from [1] in determining the multiple robot configurations for a given end effector location. Solutions for the Cincinnati Milacron T 3566 and ASEA IRB2000 industrial robots are presented with a worked example for each.

Robot kinematics—I. Graphical solution of the inverse equations of closure

Solution of the inverse closure problem in robot kinematics has been unnecessarily complicated by those who have bypassed an appreciation of robot geometry in search for general methods of solution. This paper demonstrates that elementary graphical techniques can be applied to determine all of the possible robot configurations for a prescribed end effector location. In Part II, analytical solutions based on the geometric methods of Part I are presented. These solutions are derived using “straight down the line trigonometry” recommended by Hunt[1]. Ambiguities in identifying the multiple configurations, arising in [1], are resolved.

Complex Robotic Inverse Kinematic Solutions

A new method exploiting complex numbers in the inverse kinematic solution of serial robotic manipulators is presented. If a prescribed end effector location is outside of the manipulator workspace, complex joint values result. While they cannot be implemented physically, they may be mapped to real numbers. The result approximates the prescribed location. For many industrial manipulators, mapped solutions may be explained using spherical and planar dyads. An important criterion characterizes error minimization properties, and is illustrated for a 3R regional robot.

An Extended Workspace Mapping Algorithm and its Implementation in a Nuclear Tele-Robotic Control System

When a universal master control device is used for the operation of master-slave telerobots, the accessible workspaces of slave manipulators are reduced To complement such a problem, a new kinematic mapping strategy is introduced so that the slave manipulator's workspace is fully utilized By expressing the slave's joint angles in complex numbers, an extended workspace is defined. The slave end effector's location in the extended workspace is then mapped to a location within its reachable workspace. A few complex to real joint angle mapping schemes are suggested and implemented in a master-slave manipulator system consisting of a universal master control mechanism built and modified in the laboratory It is observed that the proposed mapping provides uninterrupted motion over the entire workspace of the slave manipulator.

Singular configurations and workspace of robots

The purpose of this paper is to explain the set-up of a general method for finding the singular configurations of a robot. Open en closed chain manipulators made out of links with single degree of freedom joints are considered. The manipulator singular configurations corresponding to inner and outer limits of workspace are found by the study of analytical relations between the end effector location and the joint coordinates using the Jacobian matrix.

Analytical Trajectory Optimization of Seven Degrees of Freedom Redundant Robots

The basic characteristic of kinematically redundant robots is that non-unique joint solutions may exist for a specified end effector location. Thus, trajectory planning for a kinematically redundant robot requires an optimization procedure to determine the joint displacements when solving the inverse kinematics relations. In this paper an analytical solution is developed for the trajectory optimization problem of redundant robots based on the classical Lagrange’s method. A detailed formulation is provided for seven degrees of freedom robots, which minimizes the Euclidean norm of joint dislacements for point-to-point motion trajectory planning.