Abstract: Dynamic stability of parametrically excited flexible cam-follower system of SDOF is investigated by using the combination of both the method of multiple scales and the technique of Fourier series expansion. The equations of approximate transition curves in the plane of the dimensionless frequency and excitation (amplitude) parameter that separate stable from unstable solution are derived. It is found that there are many unstable regions around ω0/ωn＝2/k（k＝1，2，…, whereω0 andωn re exciting frequency and natural frequency respectively. The example results show that the types of follower motion events dominate the stability diagram and the existence of damping reduces the instability regimes effectively. The validity of the stability diagram is verified by direct numerical integration of the equation in question.

Key words: Cam mechanism, Method of multiple scales, Parametric excitation, Stability