Abstract
Chaos in hard spring phi(6)-Van der Pol Oscillator, and its modelling and control with fractional-Order Calculus (FOC) is studied in this research. An adaptive PID controller with fractional order adaptation mechanism is proposed to synchronize fractional-order chaotic system. PID coefficients are updated using the gradient method when a proper sliding surface is chosen. Fractional-order phi(6)-Van der Pol Oscillator is used as case study to verify the proposed method.