Sensor integration for robotic laser welding processes

The use of robotic laser welding is increasing among industrial applications, because of its ability to weld objects in three dimensions. Robotic laser welding involves three sub-processes: seam detection and tracking, welding process control, and weld seam inspection. Usually, for each sub-process, a separate sensory system is required. The use of separate sensory systems leads to heavy and bulky tools, in contrast to compact and light sensory systems that are needed to reach sufficient accuracy and accessibility. In the solution presented in this paper all three subprocesses are integrated in one compact multipurpose welding head. This multi-purpose tool is under development and consists of a laser welding head, with integrated sensors for seam detection and inspection, while also carrying interfaces for process control. It can provide the relative position of the tool and the work piece in three-dimensional space. Additionally, it can cope with the occurrence of sharp corners along a three-dimensional weld path, which are difficult to detect and weld with conventional equipment due to measurement errors and robot dynamics. In this paper the process of seam detection will be mainly elaborated

Integrated sensors for robotic laser welding

A welding head is under development with integrated sensory systems for robotic laser welding applications. Robotic laser welding requires sensory systems that are capable to accurately guide the welding head over a seam in three-dimensional space and provide information about the welding process as well as the quality of the welding result. In this paper the focus is on seam tracking. It is difficult to measure three-dimensional parameters of a ream during a robotic laser welding task, especially when sharp corners are present. The proposed sensory system is capable to provide the three dimensional parameters of a seam in one measurement and guide robots over sharp corners

A Model of Operant Conditioning for Adaptive Obstacle Avoidance

We have recently introduced a self-organizing adaptive neural controller that learns to control movements of a wheeled mobile robot toward stationary or moving targets, even when the robot's kinematics arc unknown, or when they change unexpectedly during operation. The model has been shown to outperform other traditional controllers, especially in noisy environments. This article describes a neural network module for obstacle avoidance that complements our previous work. The obstacle avoidance module is based on a model of classical and operant conditioning first proposed by Grossberg ( 1971). This module learns the patterns of ultrasonic sensor activation that predict collisions as the robot navigates in an unknown cluttered environment. Along with our original low-level controller, this work illustrates the potential of applying biologically inspired neural networks to the areas of adaptive robotics and control.Office of Naval Research (N00014-95-1-0409, Young Investigator Award

Reuleaux: Robot Base Placement by Reachability Analysis

Before beginning any robot task, users must position the robot's base, a task that now depends entirely on user intuition. While slight perturbation is tolerable for robots with moveable bases, correcting the problem is imperative for fixed-base robots if some essential task sections are out of reach. For mobile manipulation robots, it is necessary to decide on a specific base position before beginning manipulation tasks. This paper presents Reuleaux, an open source library for robot reachability analyses and base placement. It reduces the amount of extra repositioning and removes the manual work of identifying potential base locations. Based on the reachability map, base placement locations of a whole robot or only the arm can be efficiently determined. This can be applied to both statically mounted robots, where position of the robot and work piece ensure the maximum amount of work performed, and to mobile robots, where the maximum amount of workable area can be reached. Solutions are not limited only to vertically constrained placement, since complicated robotics tasks require the base to be placed at unique poses based on task demand. All Reuleaux library methods were tested on different robots of different specifications and evaluated for tasks in simulation and real world environment. Evaluation results indicate that Reuleaux had significantly improved performance than prior existing methods in terms of time-efficiency and range of applicability.Comment: Submitted to International Conference of Robotic Computing 201

Multiple configuration shell-core structured robotic manipulator with interchangeable mechatronic joints : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Engineering in Mechatronics at Massey University, Turitea Campus, Palmerston North, New Zealand

With the increase of robotic technology utilised throughout industry, the need for skilled labour in this area has increased also. As a result, education dealing with robotics has grown at both the high-school and tertiary educational level. Despite the range of pedagogical robots currently on the market, there seems to be a low variety of these systems specifically related to the types of robotic manipulator arms popular for industrial applications. Furthermore, a fixed-arm system is limited to only serve as an educational supplement for that specific configuration and therefore cannot demonstrate more than one of the numerous industrial-type robotic arms. The Shell-Core structured robotic manipulator concept has been proposed to improve the quality and variety of available pedagogical robotic arm systems on the market. This is achieved by the reconfigurable nature of the concept, which incorporates shell and core structural units to make the construction of at least 5 mainstream industrial arms possible. The platform will be suitable, but not limited to use within the educational robotics industry at high-school and higher educational levels and may appeal to hobbyists. Later dubbed SMILE (Smart Manipulator with Interchangeable Links and Effectors), the system utilises core units to provide either rotational or linear actuation in a single plane. A variety of shell units are then implemented as the body of the robotic arm, serving as appropriate offsets to achieve the required configuration. A prototype consisting of a limited number of ‘building blocks’ was developed for proof-of-concept, found capable of achieving several of the proposed configurations. The outcome of this research is encouraging, with a Massey patent search confirming the unique features of the proposed concept. The prototype system is an economic, easy to implement, plug and play, and multiple-configuration robotic manipulator, suitable for various applications

Characterization of robotics parallel algorithms and mapping onto a reconfigurable SIMD machine

The kinematics, dynamics, Jacobian, and their corresponding inverse computations are six essential problems in the control of robot manipulators. Efficient parallel algorithms for these computations are discussed and analyzed. Their characteristics are identified and a scheme on the mapping of these algorithms to a reconfigurable parallel architecture is presented. Based on the characteristics including type of parallelism, degree of parallelism, uniformity of the operations, fundamental operations, data dependencies, and communication requirement, it is shown that most of the algorithms for robotic computations possess highly regular properties and some common structures, especially the linear recursive structure. Moreover, they are well-suited to be implemented on a single-instruction-stream multiple-data-stream (SIMD) computer with reconfigurable interconnection network. The model of a reconfigurable dual network SIMD machine with internal direct feedback is introduced. A systematic procedure internal direct feedback is introduced. A systematic procedure to map these computations to the proposed machine is presented. A new scheduling problem for SIMD machines is investigated and a heuristic algorithm, called neighborhood scheduling, that reorders the processing sequence of subtasks to reduce the communication time is described. Mapping results of a benchmark algorithm are illustrated and discussed

Kinematics of A 3-PRP planar parallel robot

Recursive modelling for the kinematics of a 3-PRP planar parallel robot is presented in this paper. Three planar chains connecting to the moving platform of the manipulator are located in a vertical plane. Knowing the motion of the platform, we develop the inverse kinematics and determine the positions, velocities and accelerations of the robot. Several matrix equations offer iterative expressions and graphs for the displacements, velocities and accelerations of three prismatic actuators

Delta robot motion control

Abstract. The aim of this thesis is to generate a functional motion control to a delta robot. The motion control is based on solving the inverse kinematics problem of the delta robot. This solution is then used to form the control logic of the robot. In addition, this thesis also introduces forward kinematics solution models and, the most common industrial robots and their features. Applications of industrial robots, as well as the industries that utilize them the most are also examined. This thesis introduces a self-made delta robot and its motion control design. The functionality of motion control is studied by measuring the positioning accuracy as well as the repeatability of the self-made delta robot in the xy-plane. Accuracy measurements are performed using a separate measuring device. A small-scale comparison between the positioning accuracy of a self-made and a commercial delta robot is implemented to find out how closely can the performance of a commercial delta robot be reproduced with a self-made delta robot. The results of this thesis indicate that the inverse kinematics model of the delta robot as well as the motion control actually work. The results demonstrate that the performance of the self-made delta robot is at a good level and that further development is worthwhile. There was not enough measurement data to perform a proper comparison between the self-made and the commercial delta robot. However, despite the narrow sampling, it is assumed that the positioning accuracy of the self-made delta robot is not yet at the same level as that of the commercial product. The accuracy of the self-made delta robot presented in this thesis can be improved by developing the feeding of the robot’s drive commands. The materials used in the construction of the robot as well as the quality of the joints also affect the accuracy. The inverse kinematics model of the delta robot presented in this thesis can be easily scaled to different sized delta robots depending on the application. Motion control can be utilized in the control of delta robots implemented with a similar mechanical structure.Delta-robotin liikkeenohjaus. Tiivistelmä. Tämän työn tarkoituksena on suunnitella delta-robotille toimiva liikkeenohjaus. Liikkeenohjauksen rakentaminen perustuu delta-robotin käänteiskinematiikan ratkaisemiseen. Käänteiskinematiikan ratkaisua hyödynnetään ohjauslogiikan toteutuksessa. Työssä tutustutaan myös suorankinematiikan ratkaisumalleihin, sekä esitellään yleisimpiä teollisuusrobotteja ja niiden ominaisuuksia. Työssä tarkastellaan myös teollisuusrobottien käyttökohteita, sekä niitä eniten hyödyntävät teollisuudenalat. Työssä tutustutaan omavalmisteiseen delta-robottiin ja sen liikkeenohjauksen suunnitteluun. Liikkeenohjauksen toimivuutta tutkitaan mittaamalla omavalmisteisen delta-robotin paikoitustarkkuus, sekä toistotarkkuus xy-tasossa. Tarkkuusmittaukset toteutetaan käyttämällä erillistä mittalaitetta. Työssä pyritään myös selvittämään kuinka lähelle kaupallisen delta-robotin suorituskykyä voidaan päästä omavalmisteisella delta-robotilla. Työssä toteutetaan pienimuotoinen vertailu omavalmisteisen ja kaupallisen delta-robotin paikoitustarkkuuden välillä. Työn tulokset osoittavat, että delta-robotin käänteiskinematiikan malli, sekä liikkeenohjaus toimivat. Tuloksista selviää, että omavalmisteisen delta-robotin suorituskyky on hyvällä tasolla ja sen kehittämistä kannattaa jatkaa. Omavalmisteisen ja kaupallisen delta-robotin kunnolliseen vertailuun ei saatu riittävästi dataa. Suppeasta otannasta huolimatta on kuitenkin oletettavaa, että omavalmisteisen delta-robotin paikoitustarkkuus ei vielä yllä samalle tasolle kaupallisen tuotteen kanssa. Työssä esitellyn omavalmisteisen delta-robotin tarkkuutta saadaan parannettua kehittämällä robotin ajokomentojen syöttämistä. Myös robotin rakenteessa käytetyt materiaalit, sekä nivelten laadukkuus vaikuttavat tarkkuuteen. Työssä esitetty delta-robotin käänteiskinematiikan malli on helposti skaalattavissa myös erikokoisiin delta-robotteihin käyttökohteesta riippuen. Liikkeenohjausta voidaan hyödyntää vastaavalla mekaanisella rakenteella toteutettujen delta-robottien ohjauksessa