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Fractional order Coulomb friction compensation and experimental validation on a fractional horsepower dynamometer. Sara Dadras 1,2 Hadi Malek 2 YangQuan Chen 2 1 Tarbiat Modares University, Tehran, Iran
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Fractional order Coulomb friction compensation and experimental validation on a fractional horsepower dynamometer Sara Dadras 1,2 Hadi Malek 2 YangQuan Chen 2 1 Tarbiat Modares University, Tehran, Iran 2 Center of Self-Organizing and Intelligent Systems (CSOIS), ECE Department, Utah State University, Logan, UT, USA March 5, 2012
Outline • Fiction model • IO Adaptive friction compensation (IO-AFC) • FO Adaptive friction compensation (FO-AFC) • Method I • Method II • Simulation results • Experimental results • Conclusion
Friction model • The friction is a nonlinear phrnomrnon that exist in many real world applications. Fot the servo control system, it is dependent on the state of the motor and its environment. The friction model considered here is based on the Friedland, et al paper [1]
Friction model • So, the dynamic equation of the motor, i.e. the velocity dynamics, can be written as follows where w is the force due to all sources other than friction. It is assumed that this component w of the total force and the velocity v are measurable quantities.
IO-AFC • An Integer order estimator for undermined parameter a in the friction model can be presented as follows
FO-AFC (Method I) • A fractional order estimator for undermined parameter a in the friction model can be presented as follows
FO-AFC • To study the performance of the observer, consider the error between the actual parameter a and its estimate • Using fractional differentiator, we have
Conclusion • A fractional order adaptive scheme is proposed for the Coulomb friction compensation in a servo control system. • The design procedure of the proposed control scheme is very simple and its application is easy. The comparison shows that the fractional order compensator has less tracking error. • A fractional horsepower dynamometer was developed as a general purpose hardware-in-the-loop real-time simulation platform to emulate Coulomb friction as a mechanical nonlinearity. The simulation and experimental results demonstrate that the proposed controller has a good performance and diminishes friction characteristics.
Reference [1] B. Friedland, Y.J. Park, “On adaptive friction compensation,” IEEE Transactions on Automatic Control, Vol. 37, Issue 10, pp. 1609-1612, 1992.