| 1. |
- Blomdell, Anders, et al.
(author)
-
Flexible application development and high-performance motion control based on external sensing and reconfiguration of ABB industrial robot controllers
- 2010
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In: ; , s. 62-66
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Conference paper (peer-reviewed)abstract
- New robot applications increasingly require external sensing to accomplish robustness and performance despite the variations and uncertainties that come with the increasing demands on flexibility for manufacturing of customized products. The demands on productivity then require high performance, which for well known feedback-control reasons means short response times from external process event to reaction on the robot motor control. The need for high- performance sensor interfaces connected to the motion control without excessive buffering and computations has therefore gained increasing attention over the last decade. Apart from high sampling frequencies and short latencies, there are also engineering aspects to consider. Control engineering tools should be possible to utilize, additional computing power is better connected via real-time Ethernet connections, and all interfaces should check compatibility without sacrificing performance. Furthermore, all that should preferably coexist with the original system, superimposing the effects on external sensing while still maintaining safety and consistency of data. The reason is that the original control software is model based and built on millions of lines of C-code, and tested beyond the possibilities of a research lab. Such a system has been accomplished for control and application development using ABB robots. A short description of the system is given, and its use for application/control development is exemplified. User specific feedback control can be done easily with short sampling periods and less than 1ms of latency from sensing to motor reaction.
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| 2. |
- Cescon, Marzia, et al.
(author)
-
Subspace-based Identification of Compliance Dynamics of Parallel Kinematic Manipulator
- 2009
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In: IEEE/ASME International Conference On Advanced Intelligent Mechatronics, 2009. ; 1-3, s. 1028-1033
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Conference paper (peer-reviewed)abstract
- A high-bandwith robot-workpiece interaction requires a stiff robot without resonances in the frequency range of operation. In this article, the compliance dynamics of the Gantry-Tau parallel kinematic robot were identified using subspace-based identification and physical modeling. Measurements were performed both with a camera vision system developed and with a laser tracker. Although promising simulation results for another Gantry-Tau prototype exist, both vision and laser tracker experiments identified multiple resonances around 14 Hz, which can reduce force control performance.
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| 3. |
- Crothers, Phil, et al.
(author)
-
Characterization of the Tau parallel kinematic machine for aerospace application
- 2009
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In: SAE 2009 AeroTech Congress & Exhibition Technical Papers.
-
Conference paper (peer-reviewed)abstract
- A consortium of interested parties has conducted an experimental characterization of two Tau parallel kinematic machines which were built as a part of the EU-funded project, SMErobot1. Characteristics such as machine stiffness, work envelope, repeatability and accuracy were considered. This paper will present a brief history of the Tau parallel machine, the results of this testing and some comment on prospective application to the aerospace industry.
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| 4. |
- Dressler, Isolde, et al.
(author)
-
A Kinematic Error Model for a Parallel Gantry-Tau Manipulator
- 2010
-
In: ; , s. 3709-3714
-
Conference paper (peer-reviewed)abstract
- Parallel robots are generally said to be more accurate but to have a smaller workspace compared to serial robots. With the Gantry-Tau robot, a parallel robot with a large, reconfigurable workspace was presented. This article tries to identify the maximum achievable end-effector positioning accuracy of the Gantry-Tau robot. To this end, a couple of new kinematic error models are presented and evaluated. The sources of the remaining positioning errors (0.09 mm) are discussed.
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| 5. |
- Dressler, Isolde, et al.
(author)
-
Automatic Kinematic Calibration of a Modular Gantry-Tau Parallel Robot from a Kinematics Point of View
- 2008
-
In: 2008 IEEE International Conference on Robotics and Automation, vols 1-9. - 2152-4092 .- 1050-4729. - 9781424416462 ; , s. 1282-1287
-
Conference paper (peer-reviewed)abstract
- A method for computer assisted kinematic calibration of a modular Gantry-Tau parallel robot is presented and tested in an experiment. A computer tool developed executes the first step of a kinematic calibration, the choice of appropriate measurement points, using a priori knowledge about kinematic parameters, e.g. obtained with a measuring tape. This step is performed by intersecting the robot's kinematic workspace and the area surveyable by the measurement device and overlaying it with a grid of a desired number of measurement points. A simulation determines automatically whether the choice leads to an accurate calibration and outputs a trajectory readable by a robot controller. In a calibration experiment it is shown that the method gives results with an accuracy comparable to that of manual calibration. The method allows non-experts to execute kinematic calibration of modular robots after reconfiguration thus making possible the use of modular robots in small size enterprises where such robots can answer the need for flexibility required with regularly changing tasks.
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| 6. |
- Dressler, Isolde, et al.
(author)
-
Closed-form calibration of the Gantry-Tau parallel robot
- 2008
-
In: [Host publication title missing].
-
Conference paper (peer-reviewed)abstract
- This paper addresses the kinematic calibration of the Gantry-Tau parallel kinematic manipulator. It offers two closed-form solutions to this problem, which do not need any initial guess, contrarily to most calibration methods that are based on non-linear least square minimization. This makes the proposed methods applicable by non expert users in a context of mechanical modularity of the robot. Experimental results validate the approach.
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| 7. |
- Dressler, Isolde, et al.
(author)
-
Configuration Support and Kinematics for a Reconfigurable Gantry-Tau Manipulator
- 2007
-
In: 2007 IEEE International Conference on Robotics and Automation (IEEE Cat No. 07CH37836D). ; , s. 2957-2962
-
Conference paper (peer-reviewed)abstract
- Affordable and competitive industrial automation is of key importance for small and medium enterprises, in Europe and elsewhere. A key factor is the introduction of new robot automation concepts that ease fast deployment and extend available task repertoire. The Gantry-Tau manipulator is a new robot concept. In contrast to other parallel kinematic manipulators (PKMs), it has a large working range. The high stiffness makes it ideal for a wide range of tasks such as grinding, deburring, and cutting. An additional aspect of such a PKM is the modularity, which in this work has been studied in terms of possibilities for assembly and mechanical reconfiguration at the end-user site, integration of such a kinematically different robot with a standard industrial controller, and new needs for methods/tools to support simple (re)configuration. What is needed for fully utilizing the modularity of the concept in typical SME manufacturing scenarios? A range of software tools and methods were found to be useful and necessary for efficient engineering and integration. For experimental evaluation, a full-scale prototype robot was designed and built, the kinematic software was developed and integrated into the ABB kinematics software, robot CAD software was adapted to the configuration needs, and both simulations and physical experiments were carried out. Our findings make us believe that enhanced software tools should be integrated on a higher symbolic (or meta-) level to better support transformation of data and code generation, but also that the Gantry-Tau type of robot (with adequate software support) will bring a new dimension of flexibility into SME manufacturing.
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| 8. |
- Dressler, Isolde
(author)
-
Modeling and Control of Stiff Robots for Flexible Manufacturing
- 2012
-
Doctoral thesis (other academic/artistic)abstract
- To survive on a global market, small and medium size enterprises (SMEs) require affordable and competitive industrial automation for high quality flexible manufacturing. This thesis contributes to the development of robot concepts that fit the needs of SMEs. A major part of the thesis deals with the modeling of the three degree-of-freedom (DOF) Gantry-Tau parallel kinematic robot, which has the potential to fulfill the requirements on accuracy, mechanical stiffness and conceptual flexibility of a robot for SMEs. Additionally, concepts that aid the SMEs to achieve the required accuracy and a more intuitive robot operation were developed and evaluated. The modeling of the Gantry-Tau robot includes both kinematic and dynamic modeling. Based on the nominal kinematic model, kinematic error models were developed, as well as kinematics for the F1-type Gantry-Tau, a Gantry-Tau architecture extended to 6~DOF. The modeling was evaluated in kinematic calibration experiments. A rigid body model was derived and identified, including friction in the actuators. As noticeable flexible behaviour was observed, the compliance dynamics were identified by black box modeling. Kinematic calibration was not only considered for evaluation of the kinematic models developed, but it was also studied how to automize the kinematic calibration procedure, so that it can be executed by non-expert SME staff after a possible geometric reconfiguration of the robot. In the search of affordable, accurate and reusable measurement devices for kinematic calibration in SMEs, the usage of camera vision for kinematic calibration was evaluated. To make the programming of a robot trajectory fast and intuitive, lead-through programming was recently introduced. A new concept for lead-through programming in contact situations is proposed in this thesis, where two force sensors are used. While the first sensor is used for guiding the robot, the second force sensor measures the tool force, which can prevent damage of the tool or workpiece and can help to keep a steady contact between tool and surface. The concept was demonstrated in two example applications. A possibility to improve the performance for a repeatedly executed motion is iterative learning control (ILC). An ILC algorithm is evaluated on the Gantry-Tau robot, which uses an estimate of the tool motion, based on measurements from an accelerometer mounted at the end-effector plate and in addition to measurements on the motor side. The performance of the tool motion was shown to be considerably improved compared to the case when only motor side measurements are used.
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| 9. |
- Haage, Mathias, et al.
(author)
-
Reconfigurable Parallel Kinematic Manipulator for Flexible Manufacturing
- 2009
-
In: 13th IFAC Symposium on Information Control Problems in Manufacturing. - 9783902661432 ; 42:4, s. 145-150
-
Conference paper (peer-reviewed)abstract
- Flexible manufacturing puts high demands on industrial automation in terms of affordable and competitive solutions and is of key importance for short-lot production typically found in small and medium sized enterprises, situations where today manual labour is extensively used despite environmental issues and harsh working conditions. Key factors in the successful introduction of new robot automation concepts are that they provide both the desired performance and quality (technical capability), but also that they enable fast deployment and extend available task repertoire. The Gantry-Tau manipulator is a new robot concept which in contrast to other high-performance parallel kinematic manipulators (PKM), has a large, open working range. Its high stiffness makes it ideal for a wide range of tasks such as grinding, deburring, and cutting. An additional aspect of such a PKM is the modularity, which in this work has been studied in terms of possibilities for assembly and mechanical reconfiguration at the end-user site, integration of such a kinematically different robot with a standard industrial controller, and new needs for methods/tools to support simple (re)configuration. A range of software tools and methods were found to be useful and necessary for efficient engineering and integration of the concept in typical SME manufacturing scenarios. For experimental evaluation, two full-scale prototype robots were designed and built, the kinematic software was developed and integrated into a couple of different robot control systems, robot CAD software was adapted to the configuration needs, and both simulations and physical experiments were carried out. Our findings make us believe that enhanced software tools should be integrated on a higher symbolic (or meta-) level to better support transformation of data and code generation, but also that the Gantry-Tau type of robot (with adequate software support) will bring a new dimension of flexibility into SME manufacturing.
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| 10. |
- Otter, Martin, et al.
(author)
-
StateGraph-A Modelica Library for Hierarchical State Machines
- 2005
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In: Modelica 2005 Proceedings. ; , s. 569-578
-
Conference paper (other academic/artistic)abstract
- The new library Modelica.StateGraph is a freeModelica package providing components to modeldiscrete event and reactive systems in a convenientway. It has a similar modeling power as Statecharts,but avoids some deficiencies of Statecharts by usingelements of JGrafchart and by using Modelica as an“action” language. An overview of the StateGraphlibrary is given, the available components and anapplication example. The implementation of thelibrary in Modelica is sketched, especially theneeded extension to Modelica that will be availablein release 2.2 of the Modelica language.
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| 11. |
- Robertsson, Anders, et al.
(author)
-
Modeling and Control of a Parallel Robot Using Modelica
- 2009
-
Conference paper (peer-reviewed)abstract
- A new type of high-performance robots has been developed by ABB Robotics, the Robotics Lab at Lund University and Güdel AG, Switzerland. In all parts of the project, ranging from the simulation of the kinematic configuration and reachable workspace, and kinematic and dynamic calibration/grey-box identification, and to code generation of controllers and optimal switching strategies for hybrid control, Modelica and Opti- mica provide very valuable functionality. We will make a short overview of the different aspects used during the development.
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| 12. |
- Robertsson, Anders, et al.
(author)
-
Positioning Accuracy of a Parallel Kinematic Gantry-Tau Robot
- 2010
-
Conference paper (peer-reviewed)abstract
- Parallel robots are generally said to be more accurate and have a smaller workspace compared to serial robots. With the Gantry-Tau robot, a parallel robot with relatively large workspace was presented. This article examines the end-effector positioning accuracy of the Gantry-Tau robot. End-effector positioning errors arising from joint positioning or modeling errors are studied. A geometric approach is used and with the aid of linearization, the influence of the robot's pose and kinematic parameters on accuracy is studied. Simulations and evalutation of measurement data support the geometric results. The joint and end-effector accuracy of two different Gantry-Tau prototypes were evaluated. The work underlines the need of a very good actuator modeling and control.
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| 13. |
- Wallén Axehill, Johanna, et al.
(author)
-
Estimation-based ILC applied to a parallel kinematic robot
- 2014
-
In: Control Engineering Practice. - : Elsevier BV. - 0967-0661 .- 1873-6939. ; 33, s. 1-9
-
Journal article (peer-reviewed)abstract
- Estimation-based iterative learning control (ILC) is applied to a parallel kinematic manipulator known as the Gantry-Tau parallel robot. The system represents a control problem where measurements of the controlled variables are not available. The main idea is to use estimates of the controlled variables in the ILC algorithm, and in the paper this approach is evaluated experimentally on the Gantry-Tau robot. The experimental results show that an ILC algorithm using estimates of the tool position gives a considerable improvement of the control performance. The tool position estimate is obtained by fusing measurements of the actuator angular positions with measurements of the tool path acceleration using a complementary filter. (C) 2014 Elsevier Ltd. All rights reserved.
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| 14. |
- Wallén, Johanna, et al.
(author)
-
Observer-based ILC Applied to the Gantry-Tau Parallel Kinematic Robot
- 2011
-
In: Proceedings of the 18th IFAC World Congress. - : IFAC. - 9783902661937 ; , s. 992-998
-
Conference paper (peer-reviewed)abstract
- Three approaches of iterative learning control (ILC) applied to a Gantry-Tau parallel kinematic robot are studied; ILC algorithms using 1) measured motor angles, 2) tool-position estimates, and for evaluation purposes, 3) measured tool position. The approaches are compared experimentally, with the tool performance evaluated using external sensors. It is concluded that the tool performance can be improved using tool-position estimates in the ILC algorithm, compared to when using motor-angle measurements. Applying ILC algorithms to a system following trajectories with so-called lead-in/lead-out is also considered in the paper.
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| 15. |
- Wallén, Johanna, et al.
(author)
-
Observer-Based ILC Applied to the Gantry-Tau Parallel Kinematic Robot : Modelling, Design and Experiments
- 2010
-
Reports (other academic/artistic)abstract
- Three different approaches of iterative learning control (ILC) applied to a parallel kinematic robot are studied. First, the ILC algorithm is based on measured motor angles only. Second, tool-position estimates are used in the ILC algorithm. For evaluation, the ILC algorithm finally is based on measured tool position. Model-based tuning of the ILC filters enables learning above the resonance frequencies of the system. The approaches are compared experimentally on a Gantry-Tau prototype, with the tool performance being evaluated by using external sensors. It is concluded that the tool performance can be improved by using tool-position estimates in the ILC algorithm, compared to when using motor-angle measurements. In the paper applying ILC algorithms to a system following trajectories with so-called lead-in/lead-out is also considered, as well as dynamic modelling of the Gantry-Tau prototype.
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| 16. |
- Wallén, Johanna, et al.
(author)
-
Observer-Based ILC Applied to the Gantry-Tau Parallel Kinematic Robot
- 2011
-
Conference paper (peer-reviewed)abstract
- Three approaches of iterative learning control (ILC) applied to a Gantry-Tau parallel kinematic robot aC algorithms using 1) measured motor angles, 2) tool-position estimates, and for evaluation purposes, 3l position. The approaches are compared experimentally, with the tool performance evaluated using extert is concluded that the tool performance can be improved using tool-position estimates in the ILC algor to when using motor-angle measurements. Applying ILC algorithms to a system following trajectories witad-in/lead-out is also considered in the paper.
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