Abstract: The sign algorithm of the harmonic balance approximate solutions and homotopy continuation method are introduced to get the analytic limit cycle and steady state response of the forced Van der Pol oscillator. In order to enhance precision,a correction algorithm is proposed. The approximate solution presented here is compared with numerical simulation. It is shown that the algorithm is very accurate, reliable and also an effective way of analyzing strong nonlinear systems.

Key words: harmonic balance, homotopy continuation method, correction algorithm, limit cycle