Errata
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This page contains information about errata for Feedback Systems. The errata listed here include known and corrected errors since the first printing of the book; clicking on the link will take you to a page with additional details. Typos and other relatively minor corrections are listed here but do not have separate pages with additional details (they also do not appear on individual chapter pages).
Conventions:
 Each line of text and each line of a displayed equation are counted as a line. Negative line numbers mean number of lines from the bottom of the page. First line on page = 1, last line on page = 1.
 Entries in boldface indicate errors which might change significantly the interpretation of the text.
 The version refers to the release number in which the error was found. Errors are corrected in all subsequent releases of the text.
 The status of the errata uses the following terms:
 Submitted  erratum has been submitted, but not yet processed
 Open  erratum has been received, but not yet corrected
 Pending  erratum has been corrected, but fix is not yet posted
 Closed  erratum has been corrected and revision is posted
 Rejected  erratum was rejected (see page for information on why)
Second Edition
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Preprint
First Edition
Third printing
Page  Line  Erratum  Version 

10  1  In the "Instrumentation" subsection, "axon of the giant squid" should be "giant axon of the squid"  2.10c 
37  4  In Example 2.1, the state space equations for the balance system are missing a divisor of J_t in one of the terms  2.10c 
38  20, 21  In equation (2.12), should be x[0] (twice)  2.10e 
40  2  In Figure 2.7, the coefficients are for an update period of one day  2.10c 
42  2  In Figure 2.9, "solid" and "dashed" should be swapped  2.10e 
43  12  In displayed equation for , leading minus sign is missing from rightmost expression  2.10d 
47  6  In Example 2.5, expression for the step response is missing some factors  2.10d 
49  19  In the normalized state space model for the springmass system, the derivative should be with respect to  2.11b 
49  10  In Example 2.7, reference to the previous example should be Example 2.1, not Section 2.1  2.11b 
49  8 to 4  In Example 2.7, q should be replaced by p (three places) and theta (one place)  2.10d 
61  4  In Exercise 2.3, disrete should be discrete  2.10e 
62  10  In Exercise 2.4, a = 0.25 should be a = 0.75  2.10e 
84  11  In the online version of the text, there is a formatting error in equation (3.23)  2.10c 
86  1  In equation (3.26), q_0 is not defined  2.10c 
100  6  In Example 4.4, second simplifying assumption should be l/J_t = 1 (remove extra factor of m)  2.10d 
105  3  On right hand side of displayed equation, x should be x_j  2.10c 
107  7  At the end of Example 4.6, the roots should have negative real part instead of being positive  2.10d 
110  5  Near end of Example 4.11, denominator of f'(z_2e) term should be squared  2.10d 
113  14  In Example 4.10, \dot V = 0 should be treated as negative semidefinite, not positive  2.10d 
116  3,6  In Example 4.11, Lyapunov equation entries for f'_1 and f'_2 are switched (solution is correct)  2.10d 
121  10  In Example 4.13, inequality should be for x_1 instead of x_2  2.10c 
127  4  In Exercise 4.2, the q_in term should be positive  2.10d 
128  6  In Exercise 4.12, some additional assumptions are required for oscillation  2.10e 
132  1  Add a comma after "For other systems" for clarity  2.10c 
135  10  In displayed equation above equation (5.5), there is an extraneous infinity symbol after the summation  2.10f 
138  14  In Example 5.3, dot missing from q in middle term of displayed equation for dynamics with damping  2.10d 
138  11  In Example 5.3, omega_d should have terms in the square root reversed  2.11b 
140  0  In Figure 5.3, state labels are incorrect  2.10e 
140  7  In displayed equation after equation (5.11), exponential is missing parenthesis; should be  2.10d 
141  4, 8  In Example 5.4, there is a sign error in one of the terms  2.10c 
145  89  At end of Example 5.5, eigenvalue approximations are incorrect  2.10d 
145  89  At end of Example 5.5, real part of eigenvalues has incorrect sign  2.10e 
147  1015  Impulse response does not include the direct term in the proper manner  2.11b 
148  2  In the caption for Figure 5.7, "drive" should be "driven"  2.10c 
157  7  In equation (5.26), the u(k) term in the integral should be u(tau)  2.10c 
158  13, 22  In Example 5.11, the parameter should be  2.11b 
158  8  After equation (5.31), rolling friction term disappears if v = 0  2.10c 
158  7  After equation (5.31), the equilibrium velocity should be m/s  2.11b 
158  5  After equation (5.31), the parameter listed in the text should be  2.11b 
161  3  In Example 5.12, expression nonequilibrium condition has wrong symbols  2.10d 
162  7  In equation (5.37), the parameter should be  2.11b 
163  10  In equation (5.39), Coriolis term should be + C(q, \dot q)  2.10d 
165  4  In Exercise 5.8d, the left hand side of the first equation should be x(k+1)  2.10c 
178  12  In Example 6.4, the initial control signal is u(0) = k_r r = \omega_c^2 r  2.11b 
179  12  In equation (6.17), elements of the output matrix should be in the opposite order  2.10d 
179  8  In displayed equation after equation (6.17), a_l should be a_1  2.10d 
182  1620, 25  In Example 6.5, reference variable should be L_d instead of r  2.10d 
182  3  In Example 6.5, definitions of z1 and z2 are switched  2.11a 
182  17  In second line of displayed equation, missing minus sign in front of the gain matrix  2.10d 
182  21  In the last paragraph of Example 6.5, r_h should be u  2.10d 
183  4  In the caption for Figure 6.7, L_e=20 should be L_e=30  2.10d 
183  7  In equation (6.22), should be  2.11b 
184  17  For underdamped second order system, eigenvalues are listed incorrectly  2.10d 
185  3  The formula given for the rise time of a second order system in Table 6.1 is only approximate  2.11a 
186  5  Before Example 6.6, "is Qvalue" should be "its Qvalue"  2.10d 
186  3  In Example 6.6, the output equation has 'x' for the state instead of 'c'  2.10c 
188  2  In Example 6.7, the A matrix has an error in the (3,4) entry  2.11b 
189  5  In Example 6.7, the open loop eigenvalues are incorrect  2.11b 
189  15  In Example 6.7, the imaginary part of the first pair of eigenvalues is missing factor of i  2.10d 
191  5  In Example 6.8, the state space dynamics have errors in the trigonometric terms  2.10c 
192  414  In Example 6.8, the state error should be \xi and the input should be F  2.10d 
192  15  Diagonal entries for Q_v should be rho  2.10c 
196  19, 23  In Example 6.10, the system input for the linearized model should be w instead of u  2.11a 
196  1  In Example 6.10, the reference gain should be k_r = a_1/b  2.11b 
204  6  In Example 7.1, the output equation has 'x' for the state instead of 'c'  2.10c 
206  2  In expression for W_0, (3, 1) entry should be (remove factor of in second term)  2.10c 
207  13  "going zero" → "going to zero"  2.10d 
213  8  Estimator dynamics in Theorem 7.3 are missing B k_r r term  2.10c 
217  6, 5  In Example 7.5, descriptions for (disturbance) and are switched  2.10c 
219  5  Change gain matrix to for consistency  2.10d 
220  17  In expression for B(t), missing parenthesis at end of subscripted expression  2.11a 
220  12  Above displayed equation for the gain scheduled control law, should be replaced by  2.10d 
221  15  In Example 7.5, "where were" → "which were"  2.10d 
224  4  Output in Kalman decomposition for Example 7.7 is missing state error term  2.10c 
225  4  "phenomena knows" → "phenomena known"  2.10c 
229  10  Henrik Bode should be Hendrik Bode  2.11a 
233  8  In equation (8.6), matrix inverse is computed incorrectly  2.10d 
235  14  In displayed equation above equation (8.9), exponential term on right hand side should be (no minus sign)  2.10d 
236  9  In Example 8.2, resister should be resistor  2.11b 
238  9  In equation (8.15), second order partial derivative is written incorrectly  2.10c 
238  1  In Example 8.4, boundary condition and coefficients for psi(x) are incorrect  2.10c 
241  12  Before Example 8.5, "related" → "relate"  2.10d 
242  7  In Example 8.5, leading term in denominator for H_\theta F should be cubic in s  2.10d 
247  2  In Example 8.6, numerator gain term for G_ur should be k_r instead of k_1  2.10d 
247  11  Last equation in Example 8.6 has sign error in the second term  2.10c 
247  11  Last equation in Example 8.6 has errors in numerator expressions  2.10d 
249  6  In Example 8.7, remove from numerator of expression for  2.10d 
256  10,9  In Example 8.9, u should be v in the first displayed equation and the following line  2.11a 
262  2  In Exercise 8.2, text should read "transfer function from to " (instead of )  2.10d 
263  13  In Exercise 8.5, k in the denominator of G(s) should be (k+1)  2.10c 
264  9  In Exercise 8.6, second term in expression for b_n should be  2.10d 
272  10, 11  In the paragraph above Example 9.3, G(*) should be L(*)  2.11a 
272  1  In Example 9.3, intersection of negative real axis should be at 0.5.  2.10d 
273  5  In Example 9.4, "that that" → "that"  2.10d 
274  2  In right hand expression of last displayed equation of Example 9.4, in the denominator should be  2.10d 
275  1  In the caption for Figure 9.7, the transfer function should match equation (9.4)  2.11a 
275  3  In caption for Figure 9.7, "intersections" → "intersects"  2.10d 
275  5  In Example 9.5, "it is seems" → "it seems  2.10d 
282  11, 9  In Example 9.9, 'gain margin' g_m should be 'stability margin' s_m  2.10d 
282  7  In Example 9.9, the gain margin for Figure 9.12 should be  2.10d 
283  12  In equation (9.8), the right hand side should be evaluated at omega0  2.11a 
283  6  Missing parenthesis in  2.10d 
284  13  In Example 9.10, transfer function zero is at  2.10d 
289  7  In equation (9.14), should be  2.10d 
292*  10  In Exercise 9.7, should be  2.11a 
296  1  Caption for Figure 10.3b should be "Derivative action"  2.10c 
297  11  After equation (10.5), low frequency limit bound be 1/T_d instead of T_d  2.10c 
299  10  Closed loop time constant after equation (10.6) has an extra factor of 2  2.11a 
300  4  The b k_i term in the characteristic polynomial has an extra factor of s  2.10c 
300  7  In displayed equation above equation (10.7), the final term should be (not squared)  2.10d 
302  0  In Figure 10.7b, should be  2.10c 
304  8  In Example 10.4, z should be zeta  2.11a 
304  1  In Example 10.4, proportional gain should be  2.10d 
305  1  In equation (10.12), should be  2.11a 
306  1  Right after equation (10.12), should be  2.11a 
308  9  In Section 10.5, PID derivative filter should have time constant  2.10d 
309  9  In equation (10.4), upper limit of the integral should be t, not infinity  2.11a 
310  4  The expressions for the PID parameters for the op amp implementation are incorrect  2.10d 
318  4 to 1  Reference input not included in Figure 11.2 and dimensions of blocks are listed incorrectly  2.10c 
319  0  In Figure 11.3, the label 'y' at the input to P_2 should be removed  2.10c 
326  1  In equation (11.11), delete extraneous "[rad]"  2.10d 
328  11  In Example 11.5, "" should be ""  2.10c 
328  6  In Example 11.5, "dotted" line is actually "dashdotted" line  2.11a 
329  3,5  In the Figure 11.10 caption and Example 11.5 text, "dotted" line is actually "dashdotted" line  2.11a 
330  2  In the caption for Figure 11.11, Fz should be F1  2.10c 
334  0  In Figure 11.13a, curves should be labeled with z instead of b  2.10d 
338  6  At end of Example 11.11, "the can be achieved" should be "that can be achieved"  2.10d 
339  9  In expression for I_1, limits have an extra factor of i  2.10c 
340  39  Contour integral in derivation of Bode's integral formula is analyzed incorrectly  2.10c 
341  8  In Example 11.12, value for mg should be 39.2  2.11a 
341  5  In Example 11.12, transfer functions for inner loop and outer loop dynamics are incorrect  2.11b 
342  5  In Example 11.12, error should be in , not  2.11a 
342  13  In Example 11.12, after displayed equation for C_o(s), frequency where phase lead flattens out should be b_o/10  2.10d 
342  16  In Example 11.12, transfer functions for inner loop and outer loop dynamics are incorrect  2.11b 
342  10  In Example 11.12, gain term in should be 2 instead of 0.8  2.11a 
344  4  In Exercise 11.5, final expression for should be  2.11a 
345  10  In Exercise 11.10, controller gain at frequency should be  2.10d 
357  6, 8  For Youla parameterization, P = b(s)/a(s) = B(s)/A(s) and C0 = G0(s)/F0(s)  2.10c 
359  6, 4  In equation (12.13) and the displayed equation above it, T should be T  2.10d 
361  13  Missing end parenthesis at end of sentence  2.10c 
363  17  In Example 12.8, repeated in denominator of transfer function for should be  2.10d 
365  13  The reference to the maximum complementary sensitivity should be to equation (12.7)  2.10c 
366  16  In equation (12.16), a is not defined and a factor of a is missing in numerator the last term  2.10c 
367  8  In equation (12.18), a factor of is missing from the numerator  2.10c 
368  7  In equation (12.21), final term in expression for should be  2.10d 
369  12  Replace "dashed" with "shaded" in the description of Figure 12.16a  2.10c 
371  4  Reference to Figure 12.17b should be to Figure 12.17 (right)  2.10c 
376  2  In Exercise 12.11, first term in numerator for should be  2.10d 