Adaptive Feedforward Control For High Precision Force Control Of Electromechanical Fatigue Testing Machine

An adaptive feedforward scheme is proposed to enlarge the frequency range where precise biased sinusoidal force can be generated by an electromechanical fatigue testing machine (FTM). The major concern is to guarantee a tight precision with respect to a desired output peak, as well as its peak-to-peak amplitude. A simple efficient method to continuously estimate a sinusoidal signal amplitude is instrumental. To this end, a simple second order resonant filter is proposed. A Hammerstein dynamic model is analytically established relating a critical feedforward parameter with the estimated amplitude. Then, an adaptive control law is proposed and theoretically justified. The resulting controller was successfully tested by simulation as well as experimentally.