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EnglishIn robotics actuators and manipulators are usually described by highly nonlinear models. Also for a manipulator dynamics with respect to a given equilibrium pOint, the linearized model must be considered along with some nonlinearity in order to get a significative global model. By assuming that a static nonlinear element is in series with a dynamic element we have a Hammerstein (Wiener) model if the nonlinearity precedes (follows) the linear dynamic part. In this paper a nonlinear auto-tuning by relay-feedback is used for the determination of both the linear part and the static nonlinearity of the model. In the conventional auto-tune test developed by Astrom-Hagglund a relay is placed in the loop and from the resulting limit cycle the critical gain and the critical frequency are measured. The non linear auto-tune method makes use of many relay-feedback tests with different relay amplitudes and different known dynamic elements inserted in the loop. By a suitable modification of the relay characteristics it is possible to compute points of the nonlinear characteristic. The effectiveness of this technique is demonstrated on a simulated example: the stiffness control of a simple robotic manipulator.
| Titolo: | Nonlinearity measurements via auto-tune test in robotics |
| Autori interni: | |
| Anno del prodotto: | 1995 |
| Abstract: | In robotics actuators and manipulators are usually described by highly nonlinear models. Also for a manipulator dynamics with respect to a given equilibrium pOint, the linearized model must be considered along with some nonlinearity in order to get a significative global model. By assuming that a static nonlinear element is in series with a dynamic element we have a Hammerstein (Wiener) model if the nonlinearity precedes (follows) the linear dynamic part. In this paper a nonlinear auto-tuning by relay-feedback is used for the determination of both the linear part and the static nonlinearity of the model. In the conventional auto-tune test developed by Astrom-Hagglund a relay is placed in the loop and from the resulting limit cycle the critical gain and the critical frequency are measured. The non linear auto-tune method makes use of many relay-feedback tests with different relay amplitudes and different known dynamic elements inserted in the loop. By a suitable modification of the relay characteristics it is possible to compute points of the nonlinear characteristic. The effectiveness of this technique is demonstrated on a simulated example: the stiffness control of a simple robotic manipulator. |
| Handle: | http://hdl.handle.net/11568/21759 |
| Appare nelle tipologie: | 4.1 Contributo in Atti di convegno |
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