Optimization of vibration response for energy harvesters is critical for maximizing power generation efficiency.  In this research project, a theoretical model of a piecewise-linear (PWL) nonlinear vibration harvester is proposed and numerically investigated. This new technique enables automatic frequency tunability in the energy harvester
by controlling the gap size in the PWL oscillator so that it is able to adapt to changes in excitations. To optimize the performance of the proposed system, a control method combining the response prediction, signal measurement and gap adjustment mechanism is proposed.