The block diagram of a nonlinear system is given in Figure 6. There is an ideal relay element and a linear transfer function. The Nyquist plots for the two elements are shown in Figure 7. Use the Describing Function method to analyse this system. Which one of the following is the describing function of an ideal relay element? N(A)=M4A,N(A)=A4M,N(A)=4AM,N(A)=4MA Does self-oscillation exist in this system? If yes, calculate the self-oscillation frequency and amplitude. Figure 6. Block diagram of a nonlinear system Figure 7. Nyquist plot for the nonlinear system of Figure 6