| 1. |
- Enqvist, Martin, 1976-, et al.
(author)
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The CDIO Initiative from an Automatic Control Project Course Perspective
- 2005
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In: Proceedings of the 16th IFAC World Congress. - 9783902661753 ; , s. 2283-2283
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Conference paper (peer-reviewed)abstract
- The CDIO (Conceive Design Implement Operate) Initiative is explained, and some of the results at the Applied Physics and Electrical Engineering program at Linköping University, Sweden, are presented. A project course in Automatic Control is used as an example. The projects within the course are carried out using the LIPS (Linköping interactive project steering) model. An example of a project, the golf playing industrial robot, and the results from this project are also covered.
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| 2. |
- Gunnar, Johan, et al.
(author)
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Nonlinear Grey-box Identification of Linear Actuators Containing Hysteresis
- 2006
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In: Proceedings of the 2006 IEEE International Conference on Robotics and Automation. - Linköping : Linköping University Electronic Press. - 0780395050 ; , s. 1818-1823
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Conference paper (peer-reviewed)abstract
- A new identification procedure for a linear actuator used in parallel kinematic manipulators has been developed. The actuator dynamics contain both hysteresis and backlash resulting in a highly nonlinear system. The results in this paper show that not only can a nonlinear model of the system be successfully identified from measurement data, but the model is also compact enough to be an ideal candidate for inclusion in a high-performance robot control system.
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| 3. |
- Wernholt, Erik, 1975-, et al.
(author)
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Detection and Estimation of Nonlinear Distortions in Industrial Robots
- 2006
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In: Proceedings of the 23rd IEEE Instumentation and Measurement Technology Conference. - Linköping : Linköping University Electronic Press. - 0780393600 - 0780393597 ; , s. 1913-1918
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Conference paper (peer-reviewed)abstract
- System identification in robotics often involves the estimation of linear models characterizing the behavior in certain operating points. In this paper, a method for the detection and estimation of nonlinear distortions in an estimated frequency response function (FRF) has successfully been applied to experimental data from an industrial robot. The results show that nonlinear distortions areindeed present and cause larger variability in the FRF than the measurement noise contributions.
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| 4. |
- Wernholt, Erik, 1975-
(author)
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Multivariable Frequency-Domain Identification of Industrial Robots
- 2007
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Doctoral thesis (other academic/artistic)abstract
- Industrirobotar är idag en väsentlig del i tillverkningsindustrin där de bland annat används för att minska kostnader, öka produktivitet och kvalitet och ersätta människor i farliga eller slitsamma uppgifter. Höga krav på noggrannhet och snabbhet hos robotens rörelser innebär också höga krav på de matematiska modeller som ligger till grund för robotens styrsystem. Modellerna används där för att beskriva det komplicerade sambandet mellan robotarmens rörelser och de motorer som orsakar rörelsen. Tillförlitliga modeller är också nödvändiga för exempelvis mekanisk design, simulering av prestanda, diagnos och övervakning.En trend idag är att bygga lättviktsrobotar, vilket innebär att robotens vikt minskas men att den fortfarande kan hantera en lika tung last. Orsaken till detta är främst att minska kostnaden, men också säkerhetsaspekter spelar in. En lättare robotarm ger dock en vekare struktur där elastiska effekter inte längre kan försummas i modellen om man kräver hög prestanda. De elastiska effekterna beskrivs i den matematiska modellen med hjälp av fjädrar och dämpare.Denna avhandling handlar om hur dessa matematiska modeller kan tas fram genom systemidentifiering, vilket är ett viktigt verktyg där mätningar från robotens rörelser används för att bestämma okända parametrar i modellen. Det som mäts är position och moment hos robotens alla motorer. Identifiering av industrirobotar är ett utmanande problem bland annat eftersom robotens beteende varierar beroende på armens position. Den metod som föreslås i avhandlingen innebär att man först identifierar lokala modeller i ett antal positioner. Var och en av dessa beskriver robotens beteende kring en viss arbetspunkt. Sedan anpassas parametrarna i en global modell, som är giltig för alla positioner, så att den så väl som möjligt beskriver det lokala beteendet i de olika positionerna.I avhandlingen analyseras olika metoder för att ta fram lokala modeller. För att få bra resultat krävs att experimenten är omsorgsfullt utformade. För att minska osäkerheten i den globala modellens identifierade parametrar ingår också valet av optimala positioner för experimenten. Olika metoder för att identifiera parametrarna jämförs i avhandlingen och experimentella resultat visar användbarheten av den föreslagna metoden. Den identifierade robotmodellen ger en bra global beskrivning av robotens beteende.Resultatet av forskningen har även gjorts tillgängligt i ett datorverktyg för att noggrant kunna ta fram lokala modeller och identifiera parametrar i dynamiska robotmodeller.
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| 5. |
- Wernholt, Erik, 1975-, et al.
(author)
-
Nonlinear Grey-Box Identification of Industrial Robots Containing Flexibilities
- 2005
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In: Proceedings of the 16th IFAC World Congress. - 9783902661753 ; , s. 59-59
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Conference paper (peer-reviewed)abstract
- Nonlinear grey-box identification of industrial robots is considered. A three-step identification procedure is proposed in which parameters for rigid body dynamics, friction and flexibilites can be identified only using measurements on the motor. In the first two steps, good initial parameter estimates are derived which are used in the last step, where the parameters of a nonlinear physically parameterized model are identified directly in the time domain. The procedure is examplifed using real data from an experimental industrial robot.
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| 6. |
- Wernholt, Erik, 1975-, et al.
(author)
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Nonlinear Identification of a Physically Parameterized Robot Model
- 2006
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In: Proceedings of the 14th IFAC Symposium on System Identification. - Linköping : Linköping University Electronic Press. - 9783902661029 ; , s. 143-148
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Conference paper (peer-reviewed)abstract
- In the work presented here, a three-step identification procedure for rigid body dynamics, friction, and flexibilities, introduced in (Wernholt and Gunnarsson, 2005), will be utilized and extended. Using the procedure, the parameters can be identified only using motor measurements. In the first step, rigid body dynamics and friction will be identified using a separable least squares method, where a friction model describing the Striebeck effect is used. In the second step, initial values for flexibilities are obtained using inverse eigenvalue theory. Finally, in the last step, the remaining parameters of a nonlinear physically parameterized model are identified directly in the time domain. The procedure is exemplified using real data from an experimental industrial robot.
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| 7. |
- Wernholt, Erik, 1975-
(author)
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On Multivariable and Nonlinear Identification of Industrial Robots
- 2004
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Licentiate thesis (other academic/artistic)abstract
- The main objective of the thesis is the identification of flexibilities and nonlinearities in mathematical models of industrial robots. In particular, a nonparametric frequency-domain estimation method for the multivariable frequency response function (MFRF) has been evaluated and analyzed for the robot application. Nonlinear gray-box identification has also been treated. Since identification in robotics is a much studied problem, one important part of the thesis also is to give an overview of earlier results.For the MFRF estimation method, an approximate expression tor the estimation error has been derived which describes how the estimate is affected by disturbances, the choice of excitation signal, the feedback and the properties of the system itself. The MFRF estimation method has been evaluated using both simulation data and experimental data from an ABB IRB 6600 robot. A number of different aspects regarding excitation signals and averaging techniques have been studied. It is shown, for instance, that the repetitive nature of the disturbances further limits the choice of excitation signals. Averaging the estimates over several periods of data or using experiments with identical excitation does not give any significant reduction due to the repetitive disturbances.A three-step identification procedure is also proposed for the combined identification of rigid body dynamics, friction, and flexibilities. The procedure includes continuous-time nonlinear gray-box identification and is exemplified using experimental data.
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| 8. |
- Wernholt, Erik, 1975-, et al.
(author)
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On the Use of a Multivariable Frequency Response Function Estimation Method for Closed Loop Identification
- 2004
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In: Proceedings of the 43rd IEEE Conference on Decision and Control. - Linköping : Linköping University Electronic Press. - 0780386825 ; , s. 827-832
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Conference paper (peer-reviewed)abstract
- A method for estimating the Multivariable Frequency Response Function using closed loop data is studied. An approximate expression for the estimation error is derived, and using this expression some properties of the estimation error can be explained. Of particular interest is how the model quality is affected by the properties of the disturbances, the choice of excitation signal in the different input channels, the feedback and the properties of the system itself. The expression is illustrated by simulation data from an industrial robot.
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| 9. |
- Öhr, Jonas, et al.
(author)
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Identification of Flexibility Parameters of 6-axis Industrial Manipulator Models
- 2006
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In: Proceedings of the 2006 International Conference on Noise and Vibration Engineering. - Linköping : Linköping University Electronic Press. ; , s. 3305-
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Conference paper (peer-reviewed)abstract
- A method for identification of flexibility parameters of a 18 DOF (degrees offreedom) robot prototype model is proposed. Experiments show the strengthof the method and the results indicates that flexibilities in the bearings and thearms, taken together, are of the same order as the flexibilities in the gears.
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