Article

# A HYBRID TECHNIQUE FOR FREQUENCY DOMAIN IDENTIFICATION OF SERVO SYSTEM WITH FRICTION FORCE

International Journal of Engineering Science and Technology 01/2011;

Source: DOAJ

- Citations (27)
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**ABSTRACT:**Mechanical devices usually come with undesirable nonlinearities, such as friction, backlashes, and saturations. Under the assumption of linear systems, the commonly seen identification schemes utilize sinusoidal excitation signals for parameter identification. However, the data needed for identification are unavoidably distorted by the aforementioned nonlinearities and the identification result may not be satisfactory. In the paper, binary test signals are used to perform identification, thus simplifying the behavior of friction. An identification method based on the difference of binary multifrequency excitation signals is proposed. The modified identification algorithm does not suffer from the problem of nonlinear distortions in the signal shape and is able to determine the nonlinear friction such that an accurate servo system model can be derived. A high-precision ball-screw table with asymmetric friction is identified as a test plant for this approach. The results prove that the method can be used very successfullyIEEE Transactions on Control Systems Technology 10/2002; · 2.52 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**In this paper, we introduce an adaptive algorithm for nonlinear system identification in the short-time Fourier transform (STFT) domain. The adaptive scheme consists of a parallel combination of a linear component, represented by crossband filters between subbands, and a quadratic component, which is modeled by multiplicative cross-terms. We adaptively update the model parameters using the least-mean-square (LMS) algorithm, and derive explicit expressions for the transient and steady-state mean-square error (MSE) in frequency bins for white Gaussian inputs. We show that estimation of the nonlinear component improves the MSE performance only when the power ratio of nonlinear to linear components is relatively high. Furthermore, as the number of crossband filters increases, a lower steady-state MSE may be obtained at the expense of slower convergence. Experimental results support the theoretical derivations.IEEE Transactions on Signal Processing 11/2009; · 2.81 Impact Factor -
##### Conference Paper: Analysis and model-based control of servomechanisms with friction

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**ABSTRACT:**Friction is responsible for several servomechanism problems, and their elimination is always a challenge for control engineers. In this paper, feedback model-based compensation of friction is used for servomechanism set point and tracking tasks. Basic friction models are tested and their influence on system response is examined using describing function analysis. Analytical predictions are compared to simulations and experimental results. Various control laws using friction compensation are compared experimentally. Results showed that for both types of tasks, the best response is obtained by a model-based control law with friction compensation using the general kinetic friction model.Intelligent Robots and Systems, 2002. IEEE/RSJ International Conference on; 02/2002

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