Experimental verification of fractional order controller´s robustness using torsion test bench

Fractional order control (FOC) is still an unfamiliar concept. But it is actually a natural generalization of classical integer order control (IOC) theory, in which the orders of controlled systems and/or controllers can be any real numbers including the conventional integer numbers. This generalization provides insight and more flexibility for robust control design. This paper reviews the applications of various FOC approaches including fractional order filter and disturbance observer into the gear backlash vibration control of a torsion test bench, in which a trade-off exists between stability and the strength of vibration suppression. The theoretical analysis and implementation results show FOC´s superior robustness against gear backlash nonlinearity and more importantly its possibility of enabling a clear-cut robust control design.