Workspace optimization for a planar cable-suspended direct-driven robot

The present work is inspired by an industrial task, i.e. spray painting a large area by means of a robotic system consisting in a Cable-Driven Parallel Robot (CDPR). In many cases, the area of the robot workspace is smaller than the area to be painted. For this reason, the base of the robot has to be shifted several times during the painting process. These robots are referred to as Repetitive Workspace Robots (RWR). In other words, in order to accomplish the whole task, they need to be moved after they have completed a sub-task locally. A cable suspended CDPR is an ideal candidate for such tasks; it can be thin, light, flexible and cost-efficient. The question is: which is the best shape of the local workspace in these conditions? In fact, not always a larger area of the local workspace guarantees an efficient painting process. This is because the efficiency relies mainly on the shape rather than on the local workspace area itself. In this work we employ an index [Seriani S, Gallina P, Gasparetto A, 2014] to evaluate the efficiency of the workspace of a 2-link CDPR. Finally, we show how the index value changes in relation to some geometrical parameters of the robot, thus laying the foundations for a general design methodology

A new mechanism for soft landing in robotic space exploration

Landing safely is the key to successful exploration of the solar system; the mitigation of the connected effects of collision in mechanical systems relies on the conversion of kinetic energy into heat or potential energy. An effective landing-system design should minimize the acceleration acting on the payload. In this paper, we focus on the application of a special class of nonlinear preloaded mechanisms, which take advantage of a variable radius drum (VRD) to produce a constant reactive force during deceleration. Static and dynamic models of the mechanism are presented. Numerical results show that the system allows for very efficient kinetic energy accumulation during impact, approaching the theoretical limit

Incommensurate, helical spin ground states on the Hollandite lattice

We present a model of classical Heisenberg spins on a Hollandite lattice, which has been developed to describe the magnetic properties of $\alpha$-MnO$_2$ and similar compounds. The model has nearest neighbor interacting spins, however the strength and the sign of spin-spin interactions is anisotropic and depends on the nature of the bonds. Our analysis shows that the Hollandite lattice supports four different incommensurate and helical magnetic ground states depending on the relative strengths and signs of spin-spin interactions. We show that the incommensurate helical ground states appear due to the geometrical frustration present in the model. We demonstrate that each of the four helical incommensurate magnetic phases are continuously connected to four different collinear antiferromagnetic ground states as the strength of spin-spin interaction along some bonds is increased. The present results give support to the presence of helical states that have been previously suggested experimentally for Hollandite compounds. We provide an in-depth analysis of the magnetic form factors for each helical phase and describe how it could be used to identify each of these phases in neutron diffraction experiments.Comment: 11 pages, 8 figure

Meningkatkan Hasil Belajar IPA Melalui Media Gambar Pada Siswa Kelas Iia Sdn 78 Pekanbaru

Natural Sciences (IPA) is one of the important lesson in learning. Even for the upper secondary level or high school level, this subject to one program penjurusan which will determine the students majoring in College. In addition, this science subjects also joined the national final examination (UAN) who became the main requirements for students graduating. The research design used in this research is the class action research (PKT). The aspect that is observed on each cycle and is the result of the learning and teaching process subjects source of energy and its benefits using media pictures. The subject of the learning improvement activities are the students of class 2 SDN 78 Pekanbaru with the number of students 39 people with the details of 20 students of male and female students 19 people. The results of research on the pre cycle, the value of the results of the learning science students, the average 43,08 and there are no students who achieve KKM. Then on the cycle I the results of learning science students an average of 1.807 and students who achieve KKM 9 students (23%). At cycle II, the value of the average student learning results reach 82,56 and students who achieve KKM 39 students (100%). The implementation of the media image can improve the results of learning science students on the subjects of energy sources and benefits. The learning process explains the source of energy and its benefits the sequence on each cycle apply media image and be led by the researchers and observers

A new family of magnetic adhesion based wall-climbing robots

This paper is devoted to climbing robots that adhere to the wall through permanent magnetic elements. If the surface on which they adhere is not ferromagnetic, it is necessary for the system to be composed of two subsystems (master and follower carts), arranged in a sandwich configuration, with the surface to climb interposed between the two. However, this configuration does not allow the robot to descend from the wall where it is climbing and to move freely on the floor (because of the presence of the follower). This paper shows how to remove this limitation. In fact, the system is able to automatically detach the follower when the robot has to move on the floor and recover it when it has to climb

Pedestrian level of interaction on platform conflict areas by real-scale laboratory experiments

The objective of this work was to develop a new method to measure the interaction of passengers boarding and alighting at metro stations. This method included the Level of Interaction (LOI) as more precise indicator compared to the Level of Service (LOS). The method consisted of building a mock-up of a metro car and a series of simulation experiments in University College London’s Pedestrian Accessibility Movement Environmental Laboratory (PAMELA) based on observation at two London Underground station. This mock-up included Platform Edge Doors (PEDs) and a new space defined as Platform Conflict Area in front of the train doors in which the density of passengers was high. Results of the laboratory experiments were expressed according to the types of queues, formation of lanes, density by layer, and distance between passengers, in which the interaction followed a Logarithmic Distribution and no statistical differences were found with PEDs. These results are helpful for traffic engineers and policy makers to measure the interaction and use the LOI as a new indicator for the design of spaces in metro systems

Exploring the Effect of Crowd Management Measures on Passengers’ Behaviour at Metro Stations

To reduce problems of interaction at the platform train interface (PTI) platform edge doors (PEDs) and markings on the platform are used as door positions indicators. The common methods to study the effect of these measures are based on average values of density using Fruin’s Level of Service (LOS), however identification cannot be made of which part of the PTI is more congested. To solve this problem, a new method is proposed. The method included a conceptual model in which the PTI was discretised into 40 cm square cells to identify which part of the platform is more congested. Passengers’ behaviour was recorded considering two situations before the train arrives: i) passengers waiting in front of the doors; ii) passengers waiting beside the doors. Observation was done at existing stations at Metro de Santiago and London Underground. Results show that PEDs changed the behaviour of passengers as they were located beside the doors rather than in front of them. In addition, when markings were used on the platform, then this behaviour was reinforced. Therefore, it is recommended to use this method to better design the PTI rather than the LOS which is used to design the whole platform. Further research is needed to study the effect of PEDs on passengers with reduced mobility

Estimation of the passenger space in the boarding and alighting at metro stations

Platform edge doors (PEDs) have been used in various metro stations to improve safety and ventilation conditions, however limited research has been done to estimate the passenger space (PS) in the boarding and alighting process when PEDs are installed. The aim of this study was to estimate the space needed for boarding and alighting at metro stations. The method was based on a mock-up carriage and the relevant portion of the platform at University College London´s Pedestrian Accessibility Movement Environmental Laboratory (PAMELA), in which different load scenarios of boarding and alighting were conducted. The scenarios were based in a preliminary analysis observed at Westminster Station, in which PEDs are installed. To obtain the position of each passenger on the platform a tracking tool was used. The hypothesis of this research was that PS for alighting passengers can be represented as an asymmetrical ellipse, in which the longitudinal and lateral radii changed according to the negotiation with other passengers alighting or waiting on the platform to board the train. Therefore, there is a relationship between PS and the level of interaction, which suggests that passengers adjust their PS to avoid collision. This research can be used by traffic engineers to estimate PS of passengers boarding and alighting when PEDs are used. This in turn can help in designing the platform train interface (PTI) and platforms at transport infrastructures

Development of n-DoF Preloaded structures for impact mitigation in cobots

A core issue in collaborative robotics is that of impact mitigation, especially when collisions happen with operators. Passively compliant structures can be used as the frame of the cobot, although, usually, they are implemented by means of a single-degree-offreedom (DoF). However, n-DoF preloaded structures offer a number of advantages in terms of flexibility in designing their behavior. In this work, we propose a comprehensive framework for classifying n-DoF preloaded structures, including one-, two-, and threedimensional arrays. Furthermore, we investigate the implications of the peculiar behavior of these structures-which present sharp stiff-to-compliant transitions at designdetermined load thresholds-on impact mitigation. To this regard, an analytical n-DoF dynamic model was developed and numerically implemented. A prototype of a 10DoF structure was tested under static and impact loads, showing a very good agreement with the model. Future developments will see the application of n-DoF preloaded structures to impact-mitigation on cobots and in the field of mobile robots, as well as to the field of novel architected materials

A New Framework to Evaluate Passenger Interactions at Platform Train Interfaces

Platform train interfaces (PTIs) are spaces with high interactions between passengers boarding and alighting. A simple framework is proposed to help designers and planners to identify and benchmark the degree of interaction when crowd management measures are used such as platform edge doors (PEDs). Firstly, a conceptual model is created to represent the interaction problems, followed by the definition of variables. Then, the degree of interaction is defined based on the density and perception of risk. Finally, the results are presented in a matrix that groups the variables according to the area where the interaction happens, and to the type of users that are affected. As a case study, the framework is applied in this paper to two existing stations (with and without PEDs). The results show that the new framework is able to describe well the phenomena of high interactions and can be used to evaluate suitable crowd management measures in railway infrastructure and to communicate interaction problems in a simple and effective way