Merge pull request #71 from JuliaControl/resdist

add method for resonant augmentation that takes input matrix

src/model_augmentation.jl

@@ -99,6 +99,20 @@ function add_resonant_disturbance(sys::AbstractStateSpace{Continuous}, ω, ζ, A
  measurement ? add_measurement_disturbance(sys, Ad, Cd) : add_disturbance(sys, Ad, Cd)
 end
 
+"""
+ add_resonant_disturbance(sys::AbstractStateSpace, ω, ζ, Bd::AbstractArray)
+
+- `Bd`: The disturbance input matrix.
+"""
+function add_resonant_disturbance(sys::AbstractStateSpace, ω, ζ, Bd::AbstractArray)
+ Ad = [-ζ -float(ω); ω -ζ]
+ if isdiscrete(sys)
+ Ad .*= sys.Ts
+ Ad = exp(Ad)
+ end
+ add_disturbance(sys, Ad, [Bd zeros(sys.nx)])
+end
+
 """
  add_differentiator(sys::StateSpace{<:Discrete})
 

test/test_augmentation.jl

@@ -28,6 +28,13 @@ Gd = add_resonant_disturbance(G, 1, 0, 1, measurement=true)
 @test rank(ctrb(Gd)) == 3
 @test any(isapprox(1, atol=eps()), imag.(poles(Gd)))
 
+# Discrete time and input matrix
+G = c2d(ss(tf(1.0, [1, 1])), 0.1)
+Gd = add_resonant_disturbance(G, 1, 0, [1.0])
+@test sminreal(Gd) == G
+@test Gd.nx == 3
+allapproxin(a, b) = all(any(a .≈ b', dims=2))
+@test allapproxin(poles(Gd), [eigvals(exp([0 -1; 1 0]*0.1)); exp(-1*0.1)])
 
 
 ##