Fixes to place

src/ControlSystems.jl

@@ -32,7 +32,6 @@ export  LTISystem,
         ctrb,
         obsv,
         place,
-        luenberger,
         # Model Simplification
         reduce_sys,
         sminreal,
@@ -173,6 +172,8 @@ include("plotting.jl")
 @deprecate den denvec
 @deprecate norminf hinfnorm
 @deprecate diagonalize(s::AbstractStateSpace, digits) diagonalize(s::AbstractStateSpace)
+@deprecate luenberger(sys, p) place(sys, p, :o)
+@deprecate luenberger(A, C, p) place(A, C, p, :o)
 # There are some deprecations in pid_control.jl for laglink/leadlink/leadlinkat
 
 function covar(D::Union{AbstractMatrix,UniformScaling}, R)

src/synthesis.jl

@@ -119,45 +119,52 @@ Calculate the optimal Kalman gain for discrete time systems
 dkalman(A, C, R1,R2) = Matrix(dlqr(A',C',R1,R2)')
 
 """
-    place(A, B, p)
-    place(sys::StateSpace, p)
+    place(A, B, p, opt=:c)
+    place(sys::StateSpace, p, opt=:c)
 
-Calculate gain matrix `K` such that
-the poles of `(A-BK)` in are in `p`.
+Calculate the gain matrix `K` such that `A - BK` has eigenvalues `p`.
+
+    place(A, C, p, opt=:o)
+    place(sys::StateSpace, p, opt=:o)
+
+Calculate the observer gain matrix `L` such that `A - LC` has eigenvalues `p`.
 
 Uses Ackermann's formula.
-For observer pole placement, see `luenberger`.
+Currently handles only SISO systems.
 """
-function place(A, B, p)
+function place(A, B, p, opt=:c)
     n = length(p)
-    n != size(A,1) && error("Must define as many poles as states")
-    n != size(B,1) && error("A and B must have same number of rows")
-    if size(B,2) == 1
-        acker(A,B,p)
+    n != size(A,1) && error("Must specify as many poles as states")
+    if opt == :c
+        n != size(B,1) && error("A and B must have same number of rows")
+        if size(B,2) == 1
+            acker(A, B, p)
+        else
+            error("place only implemented for SISO systems")
+        end
+    elseif opt == :o
+        C = B # B is really the "C matrix"
+        n != size(C,2) && error("A and C must have same number of rows")
+        if size(C,1) == 1
+            acker(A', C', p)'
+        else
+            error("place only implemented for SISO systems")
+        end
     else
-        error("place only implemented for SISO systems")
+        error("fourth argument must be :c or :o")
     end
 end
-
-function place(sys::StateSpace, p)
-    return place(sys.A, sys.B, p)
+function place(sys::StateSpace, p, opt=:c)
+    if opt == :c
+        return place(sys.A, sys.B, p, opt)
+    elseif opt == :o
+        return place(sys.A, sys.C, p, opt)
+    else
+        error("third argument must be :c or :o")
+    end
 end
 
-"""
-    luenberger(A, C, p)
-    luenberger(sys::StateSpace, p)
 
-Calculate gain matrix `L` such that the poles of `(A - LC)` are in `p`.
-Uses sytem's dual form (Controllability-Observability duality) applied to Ackermann's formula.
-That is, `(A - BK)` is indentic to `(A' - C'L') == (A - LC)`.
-"""
-function luenberger(A, C, p)
-    place(A', C', p)'
-end
-
-function luenberger(sys::StateSpace, p)
-    return luenberger(sys.A, sys.C, p)
-end
 
 #Implements Ackermann's formula for placing poles of (A-BK) in p
 function acker(A,B,P)

test/test_synthesis.jl

@@ -57,6 +57,38 @@ z5,p5,k5 = zpkdata(ffb5)
 end
 
 
+
+@testset "place" begin
+    sys = ss(-4, 2, 3, 0)
+    A, B, C, _ = ssdata(sys)
+
+    @test place(A, B, [-10]) == [3][:,:]
+    @test place(A, B, [-10], :c) == [3][:,:]
+    @test place(A, C, [-10], :o) == [2][:,:]
+
+    A = [0 1; 0 0]
+    B = [0; 1]
+    C = [1 0]
+    sys = ss(A, B, C, 0)
+
+    @test place(A, B, [-1.0, -1]) ≈ [1 2]
+    @test place(sys, [-1.0, -1]) ≈ [1 2]
+    @test place(A, B, [-1.0, -1], :c) ≈ [1 2]
+    @test place(sys, [-1.0, -1], :c) ≈ [1 2]
+    @test place(A, C, [-2.0, -2], :o) ≈ [4; 4]
+    @test place(sys, [-2.0, -2], :o) ≈ [4; 4]
+
+    @test place(A, B, [-2 + im, -2 - im]) ≈ [5 4]
+    @test place(A, C, [-4 + 2im, -4 - 2im], :o) ≈ [8; 20]
+
+    A = ones(3,3) - diagm([3, 4, 5])
+    B = [1; 0; 2]
+    C = [1 1 0]
+    @test place(A, B, [-2 + 2im, -2 - 2im, -4]) ≈ [-2.6 5.2 0.8]
+    @test place(A, C, [-2 + 3im, -2 - 3im, -4], :o) ≈ [11; -12; 1]
+end
+
+
 @testset "acker" begin
 Random.seed!(0)
 A = randn(3,3)