2.2 The block diagram. Figure 2-3-1 shows the block diagram of a linear feedback control system The following terminology often used in control systems is defined with preference to the block diagram R(S),r(t=reference input C(s),c(t=output signal(controlled variable) B(s, b(t=feedback signal E(S),e(t=R(s-C(s=error signal G(s=C(s)/c(s=open-loop transfer function or forward-path transfer function MS=C(S/R(S=closed-loop transfer function H(S=feedback-path transfer function G(SH(S=loop transfer function G(s) S Fig2-2-12.2 The block diagram. Figure 2-3-1 shows the block diagram of a linear feedback control system. The following terminology often used in control systems is defined with preference to the block diagram. R(s), r (t)=reference input. C(s), c (t)=output signal (controlled variable). B(s), b (t)=feedback signal. E(s), e (t)=R(s)-C(s)=error signal. G(s)=C(s)/c(s)=open-loop transfer function or forward-path transfer function. M(s)=C(s)/R(s)=closed-loop transfer function H(s)=feedback-path transfer function. G(s)H(s)=loop transfer function. G(s) H(s) Fig2-2-1