Integrated design of a 4-DOF high-speed pick-and-place parallel robot

This paper draws on robotic mechanisms theory and elastic dynamics to propose a new methodology for the integrated design of a 4-DOF SCARA pick-and-place parallel robot. The design process, which is readily applied to other designs, is implemented by four interactive steps: (1) conceptual design and mechanical realization of the light-weight yet rigid articulated travelling plate; (2) dimensional synthesis by minimizing the maximum driving toque of a single actuated joint; (3) structural parameter design for achieving good elastic dynamic behaviours; and (4) motor sizing necessary to generate the specified cycle time. Based upon the proposed process a virtual prototype is designed for achieving a cycle time for up to 150 picks/min

Kinetostatic design of an innovative Schoenflies-motion generator

International audienceIn this paper, a novel parallel robot is introduced. The robot, a Schoenflies-Motion Generator (SMG), is capable of a special class of motions, namely, those produced with serial robots termed SCARA, an acronym for Selective-Compliance Assembly Robot Arm. These motions involve three independent translations and one rotation about an axis of fixed direction. Such motions are known to form a subgroup of the displacement group of rigid-body motions, termed the Schoenflies subgroup. The SMG is composed of two identical four-degree-of-freedom serial chains in a parallel array, sharing one common base and one common moving platform. The proximal module of each chain is active and has two controlled axes, the motors being installed on the fixed base. The links can thus be made light, thereby allowing for higher operational speeds. The distal module, in turn, is passive and follows the motions of its active counterpart, the whole mechanism giving, as a result, a four-degree-of-freedom motion to its end-platform

An approach for smooth trajectory planning of high-speed pick-and-place parallel robots using quintic B-splines

This paper presents a new, highly effective approach for optimal smooth trajectory planning of high-speed pick-and-place parallel robots. The pick-and-place path is decomposed into two orthogonal coordinate axes in the Cartesian space and quintic B-spline curves are used to generate the motion profile along each axis for achieving C4-continuity. By using symmetrical properties of the geometric path defined, the proposed motion profile becomes essentially dominated by two key factors, representing the ratios of the time intervals for the end-effector to move from the initial point to the adjacent virtual and/or the via-points on the path. These two factors can then be determined by maximizing a weighted sum of two normalized single-objective functions and expressed by curve fitting as functions of the width/height ratio of the pick-and-place path, so allowing them to be stored in a look-up table to enable real-time implementation. Experimental results on a 4-DOF SCARA type parallel robot show that the residual vibration of the end-effector can be substantially reduced thanks to the very continuous and smooth joint torques obtained

Event-based Vision: A Survey

Event cameras are bio-inspired sensors that differ from conventional frame cameras: Instead of capturing images at a fixed rate, they asynchronously measure per-pixel brightness changes, and output a stream of events that encode the time, location and sign of the brightness changes. Event cameras offer attractive properties compared to traditional cameras: high temporal resolution (in the order of microseconds), very high dynamic range (140 dB vs. 60 dB), low power consumption, and high pixel bandwidth (on the order of kHz) resulting in reduced motion blur. Hence, event cameras have a large potential for robotics and computer vision in challenging scenarios for traditional cameras, such as low-latency, high speed, and high dynamic range. However, novel methods are required to process the unconventional output of these sensors in order to unlock their potential. This paper provides a comprehensive overview of the emerging field of event-based vision, with a focus on the applications and the algorithms developed to unlock the outstanding properties of event cameras. We present event cameras from their working principle, the actual sensors that are available and the tasks that they have been used for, from low-level vision (feature detection and tracking, optic flow, etc.) to high-level vision (reconstruction, segmentation, recognition). We also discuss the techniques developed to process events, including learning-based techniques, as well as specialized processors for these novel sensors, such as spiking neural networks. Additionally, we highlight the challenges that remain to be tackled and the opportunities that lie ahead in the search for a more efficient, bio-inspired way for machines to perceive and interact with the world

Implementation of Adaptive Neural Networks Controller for NXT SCARA Robot System

Several neural network controllers for robotic manipulators have been developed during the last decades due to their capability to learn the dynamic properties and the improvements in the global stability of the system. In this paper, an adaptive neural controller has been designed with self learning to resolve the problems caused by using a classical controller. A comparison between the improved unsupervised adaptive neural network controller and the P controller for the NXT SCARA robot system is done, and the result shows the improvement of the self learning controller to track the determined trajectory of robotic automated controllers with uncertainties. Implementation and practical results were designed to guarantee online real-time

Design and implementation of robot skill programming and control

Abstract. Skill-based approach has been represented as a solution to the raising complicity of robot programming and control. The skills rely heavily on the use of sensors integrating sensor perceptions and robot actions, which enable the robot to adapt to changes and uncertainties in the real world and operate autonomously. The aim of this thesis was to design and implement a programming concept for skill-based control of industrial robots. At the theoretical part of this thesis, the industrial robot system is introduced as well as some basic concepts of robotics. This is followed by the introduction of different robot programming and 3D machine vision methods. At the last section of the theoretical part, the structure of skill-based programs is presented. In the experimental part, structure of the skills required for the “grinding with localization” -task are presented. The task includes skills such as global localization with 3D-depth sensor, scanning the object with 2D-profile scanner, precise localization of the object as well as two grinding skills: level surface grinding and straight seam grinding. Skills are programmed with an off-line programming tool and implemented in a robot cell, composed of a standard industrial robot with grinding tools, 3D-depth sensors and 2D-profile scanners. The results show that global localization can be carried out with consumer class 3D-depth sensors and more accurate local localization with an industrial high-accuracy 2D-profile scanner attached to the robot’s flange. The grinding experiments and tests were focused on finding suitable structures of the skill programs as well as to understand how the different parameters influence on the quality of the grinding.Robotin taitopohjaisten ohjelmien ohjelmointi ja testaus. Tiivistelmä. Robotin taitopohjaisia ohjelmia on esitetty ratkaisuksi robottien jatkuvasti monimutkaistuvaan ohjelmointiin. Taidot pohjautuvat erilaisten antureiden ja robotin toimintojen integroimiseen, joiden avulla robotti pystyy havainnoimaan muutokset reaalimaailmassa ja toimimaan autonomisesti. Tämän työn tavoitteena oli suunnitella ja toteuttaa taitopohjaisia ohjelmia teollisuusrobotille. Aluksi työn teoriaosuudessa esitellään teollisuusrobottijärjestelmään kuuluvia osia ja muutamia robotiikan olennaisimpia käsitteitä. Sen jälkeen käydään läpi eri robotin ohjelmointitapoja ja eri 3D-konenäön toimintaperiaatteita. Teoriaosuuden lopussa esitellään taitopohjaisten ohjelmien rakennetta. Käytännön osuudessa esitellään ”hionta paikoituksella” -tehtävän suoritukseen tarvittavien taitojen rakenne. Tehtävän vaatimia taitoja ovat muun muassa kappaleen globaalipaikoitus 3D-syvyyskameralla, kappaleen skannaus 2D-profiiliskannerilla, kappaleen tarkkapaikoitus ja kaksi eri hiontataitoa: tasomaisen pinnan ja suoran sauman hionta. Taidot ohjelmoidaan off-line ohjelmointityökalulla ja implementoidaan robottisoluun, joka muodostuu hiontatyökaluilla varustetusta teollisuusrobotista, 3D-kameroista ja 2D-profiiliskannereista. Työn tuloksista selviää, että kappaleen globaalipaikoitus voidaan suorittaa kuluttajille suunnatuilla 3D-syvyyskameroilla ja kappaleen tarkempi lokaalipaikoitus robotin ranteeseen kiinnitetyllä teollisuuden käyttämillä 2D-profiiliskannereilla. Hiontojen kokeellisessa osuudessa etsitään ohjelmien oikeanlaista rakennetta sekä muodostetaan käsitys eri parametrien vaikutuksesta hionnan laatuun

Dynamic Balancing of the SCARA robot

International audienceThis paper deals with the complete shaking force and shaking moment balancing of the four degrees of freedom SCARA robot. Dynamic reaction forces on the frame of the manipulator are eliminated by traditional approach making the total mass center of the moving links stationary. Reaction moments on the frame of the manipulator are eliminated by optimal control of the end-effector, which rotates with prescribed acceleration. A numerical simulation carried out on the software ADAMS illustrates that such a balanced SCARA robot transmits no inertia loads to surrounding, i.e. the sum of all ground bearing forces and their moments are eliminated

Natural Motion for Energy Saving in Robotic and Mechatronic Systems

Energy saving in robotic and mechatronic systems is becoming an evermore important topic in both industry and academia. One strategy to reduce the energy consumption, especially for cyclic tasks, is exploiting natural motion. We define natural motion as the system response caused by the conversion of potential elastic energy into kinetic energy. This motion can be both a forced response assisted by a motor or a free response. The application of the natural motion concepts allows for energy saving in tasks characterized by repetitive or cyclic motion. This review paper proposes a classification of several approaches to natural motion, starting from the compliant elements and the actuators needed for its implementation. Then several approaches to natural motion are discussed based on the trajectory followed by the system, providing useful information to the researchers dealing with natural motion

Application of Elliptic Jerk Motion Profile to Cartesian Space Position Control of a Serial Robot

The paper discusses the application of a motion profile with an elliptic jerk to Cartesian space position control of serial robots. This motion profile is obtained by means of a kinematic approach, starting from the jerk profile and then calculating acceleration, velocity and position by successive integrations. Until now, this profile has been compared to other motion laws (trapezoidal velocity, trapezoidal acceleration, cycloidal, sinusoidal jerk, modified sinusoidal jerk) considering single-input single-output systems. In this work, the comparison is extended to nonlinear multi-input multi-output systems, investigating the application to Cartesian space position control of serial robots. As case study, a 4-DOF SCARA-like architecture with elastic balancing is considered; both an integer-order and a fractional-order controller are applied. Multibody simulation results show that, independently of the controller, the behavior of the robot using the elliptic jerk profile is similar to the case of adopting the sinusoidal jerk and modified sinusoidal jerk laws, but with a slight reduction in the position error (−3.8% with respect to the sinusoidal jerk law and −0.8% with respect to the modified sinusoidal jerk law in terms of Integral Square Error) and of the control effort (−8.2% with respect to the sinusoidal jerk law and −1.3% with respect to the modified sinusoidal jerk law in terms of Integral Control Effort)