|
| 1 | +"""H2 design using h2syn. |
| 2 | +
|
| 3 | +Demonstrate H2 desing for a SISO plant using h2syn. Based on [1], Ex. 7. |
| 4 | +
|
| 5 | +[1] Scherer, Gahinet, & Chilali, "Multiobjective Output-Feedback Control via |
| 6 | +LMI Optimization", IEEE Trans. Automatic Control, Vol. 42, No. 7, July 1997. |
| 7 | +
|
| 8 | +[2] Zhou & Doyle, "Essentials of Robust Control", Prentice Hall, |
| 9 | +Upper Saddle River, NJ, 1998. |
| 10 | +""" |
| 11 | +# %% |
| 12 | +# Packages |
| 13 | +importnumpyasnp |
| 14 | +importcontrol |
| 15 | + |
| 16 | +# %% |
| 17 | +# State-space system. |
| 18 | + |
| 19 | +# Process model. |
| 20 | +A=np.array([[0,10,2], |
| 21 | + [-1,1,0], |
| 22 | + [0,2,-5]]) |
| 23 | +B1=np.array([[1], |
| 24 | + [0], |
| 25 | + [1]]) |
| 26 | +B2=np.array([[0], |
| 27 | + [1], |
| 28 | + [0]]) |
| 29 | + |
| 30 | +# Plant output. |
| 31 | +C2=np.array([[0,1,0]]) |
| 32 | +D21=np.array([[2]]) |
| 33 | +D22=np.array([[0]]) |
| 34 | + |
| 35 | +# H2 performance. |
| 36 | +C1=np.array([[0,1,0], |
| 37 | + [0,0,1], |
| 38 | + [0,0,0]]) |
| 39 | +D11=np.array([[0], |
| 40 | + [0], |
| 41 | + [0]]) |
| 42 | +D12=np.array([[0], |
| 43 | + [0], |
| 44 | + [1]]) |
| 45 | + |
| 46 | +# Dimensions. |
| 47 | +n_u,n_y=1,1 |
| 48 | + |
| 49 | +# %% |
| 50 | +# H2 design using h2syn. |
| 51 | + |
| 52 | +# Create augmented plant. |
| 53 | +Baug=np.block([B1,B2]) |
| 54 | +Caug=np.block([[C1], [C2]]) |
| 55 | +Daug=np.block([[D11,D12], [D21,D22]]) |
| 56 | +Paug=control.ss(A,Baug,Caug,Daug) |
| 57 | + |
| 58 | +# Input to h2syn is Paug, number of inputs to controller, |
| 59 | +# and number of outputs from the controller. |
| 60 | +K=control.h2syn(Paug,n_y,n_u) |
| 61 | + |
| 62 | +# Extarct controller ss realization. |
| 63 | +A_K,B_K,C_K,D_K=K.A,K.B,K.C,K.D |
| 64 | + |
| 65 | +# %% |
| 66 | +# Compute closed-loop H2 norm. |
| 67 | + |
| 68 | +# Compute closed-loop system, Tzw(s). See Eq. 4 in [1]. |
| 69 | +Azw=np.block([[A+B2 @D_K @C2,B2 @C_K], |
| 70 | + [B_K @C2,A_K]]) |
| 71 | +Bzw=np.block([[B1+B2 @D_K @D21], |
| 72 | + [B_K @D21]]) |
| 73 | +Czw=np.block([C1+D12 @D_K @C2,D12 @C_K]) |
| 74 | +Dzw=D11+D12 @D_K @D21 |
| 75 | +Tzw=control.ss(Azw,Bzw,Czw,Dzw) |
| 76 | + |
| 77 | +# Compute closed-loop H2 norm via Lyapunov equation. |
| 78 | +# See [2], Lemma 4.4, pg 53. |
| 79 | +Qzw=control.lyap(Azw.T,Czw.T @Czw) |
| 80 | +nu=np.sqrt(np.trace(Bzw.T @Qzw @Bzw)) |
| 81 | +print(f'The closed-loop H_2 norm of Tzw(s) is{nu}.') |
| 82 | +# Value is 7.748350599360575, the same as reported in [1]. |
| 83 | + |
| 84 | +# %% |