Fix for PID component to accept symbolic parameters

src/Blocks/Blocks.jl

@@ -26,7 +26,7 @@ export Limiter, DeadZone, SlewRateLimiter
 include("nonlinear.jl")
 
 export Integrator, Derivative, FirstOrder, SecondOrder, StateSpace
-export PI, LimPI, PID, LimPID
+export PI, LimPI, PID, PD, LimPID
 include("continuous.jl")
 
 export AnalysisPoint, get_sensitivity, get_comp_sensitivity,

src/Blocks/continuous.jl

@@ -214,15 +214,15 @@
 end
 
 """
-    PID(;name, k=1, Ti=false, Td=false, Nd=10, int__x=0, der__x=0)
+    PID(with_I = true, with_D = true; name, k=1, Ti=0.1, Td=0.1, Nd=10, int__x=0, der__x=0)
 
 Text-book version of a PID-controller without actuator saturation and anti-windup measure.
 
 # Parameters:
 
   - `k`: Gain
-  - `Ti`: [s] Integrator time constant (Ti>0 required). If set to false, no integral action is used.
-  - `Td`: [s] Derivative time constant (Td>0 required). If set to false, no derivative action is used.
+  - `Ti`: [s] Integrator time constant (Ti>0 required). If `with_I` set to false, no integral action is used.
+  - `Td`: [s] Derivative time constant (Td>0 required). If `with_D` set to false, no derivative action is used.
   - `Nd`: [s] Time constant for the derivative approximation (Nd>0 required; Nd=0 is ideal derivative).
   - `int__x`: Initial value for the integrator.
   - `der__x`: Initial value for the derivative state.
@@ -234,29 +234,42 @@
 
 See also [`LimPID`](@ref)
 """
-@component function PID(; name, k = 1, Ti = false, Td = false, Nd = 10, int__x = 0,
+@component function PID(with_I = true, with_D = true; name, k = 1, Ti = 0.1, Td = 0.1,
+    Nd = 10, int__x = 0,
     der__x = 0)
-    with_I = !isequal(Ti, false)
-    with_D = !isequal(Td, false)
+    pars = @parameters begin
+        k = k
+        Ti = Ti
+        Td = Td
+        Nd = Nd
+        int__x = int__x
+        der__x = der__x
+    end
+
     @named err_input = RealInput() # control error
     @named ctr_output = RealOutput() # control signal
-    !isequal(Ti, false) &&
-        (Ti ≥ 0 || throw(ArgumentError("Ti out of bounds, got $(Ti) but expected Ti ≥ 0")))
-    !isequal(Td, false) &&
-        (Td ≥ 0 || throw(ArgumentError("Td out of bounds, got $(Td) but expected Td ≥ 0")))
-    Nd > 0 || throw(ArgumentError("Nd out of bounds, got $(Nd) but expected Nd > 0"))
 
-    @named gainPID = Gain(k)
+    with_I &&
+        (@symcheck Ti ≥ 0 ||
+                   throw(ArgumentError("Ti out of bounds, got $(Ti) but expected Ti ≥ 0")))
+    with_D &&
+        (@symcheck Td ≥ 0 ||
+                   throw(ArgumentError("Td out of bounds, got $(Td) but expected Td ≥ 0")))
+
+    @symcheck Nd > 0 ||
+              throw(ArgumentError("Nd out of bounds, got $(Nd) but expected Nd ≥ 0"))
+
+    @named gainPID = Gain(; k)
     @named addPID = Add3()
     if with_I
-        @named int = Integrator(k = 1 / Ti, x = int__x)
+        @named int = Integrator(; k = 1 / Ti, x = int__x)
     else
-        @named Izero = Constant(k = 0)
+        @named Izero = Constant(; k = 0)
     end
     if with_D
-        @named der = Derivative(k = Td, T = 1 / Nd, x = der__x)
+        @named der = Derivative(; k = Td, T = 1 / Nd, x = der__x)
     else
-        @named Dzero = Constant(k = 0)
+        @named Dzero = Constant(; k = 0)
     end
     sys = [err_input, ctr_output, gainPID, addPID]
     if with_I
@@ -286,7 +299,14 @@
     else
         push!(eqs, connect(Dzero.output, addPID.input3))
     end
-    ODESystem(eqs, t, [], []; name = name, systems = sys)
+    ODESystem(eqs, t, [], pars; name = name, systems = sys)
+end
+
+with_I(type::Union{AbstractString, Symbol}) = contains(lowercase(string(type)), "i")
+with_D(type::Union{AbstractString, Symbol}) = contains(lowercase(string(type)), "d")
+
+function PID(type::Union{AbstractString, Symbol}; kwargs...)
+    PID(with_I(type), with_D(type); kwargs...)
 end
 
 """

test/Blocks/continuous.jl

@@ -1,3 +1,4 @@
+using Test
 using ModelingToolkit, ModelingToolkitStandardLibrary, OrdinaryDiffEq
 using ModelingToolkitStandardLibrary.Blocks
 using OrdinaryDiffEq: ReturnCode.Success
@@ -12,9 +13,13 @@ an integrator with a constant input is often used together with the system under
 =#
 
 @testset "Constant" begin
-    @named c = Constant(; k = 1)
-    @named int = Integrator(x = 1)
-    @named iosys = ODESystem(connect(c.output, int.input), t, systems = [int, c])
+    pars = @parameters begin
+        k = 1
+        x = 1
+    end
+    @named c = Constant(; k)
+    @named int = Integrator(; x)
+    @named iosys = ODESystem(connect(c.output, int.input), t, [], pars; systems = [int, c])
     sys = structural_simplify(iosys)
     prob = ODEProblem(sys, Pair[], (0.0, 1.0))
     sol = solve(prob, Rodas4())
@@ -167,9 +172,11 @@ end
 end
 
 @testset "PID" begin
+    @parameters Ti=0.5 Td=1 / 100
+    @named pid_controller = PID(; k = 3, Ti, Td)
+
     re_val = 2
     @named ref = Constant(; k = re_val)
-    @named pid_controller = PID(k = 3, Ti = 0.5, Td = 1 / 100)
     @named plant = Plant()
     @named fb = Feedback()
     @named model = ODESystem([
@@ -178,8 +185,7 @@ end
             connect(fb.output, pid_controller.err_input),
             connect(pid_controller.ctr_output, plant.input),
         ],
-        t,
-        systems = [pid_controller, plant, ref, fb])
+        t, [], [Ti, Td]; systems = [pid_controller, plant, ref, fb])
     sys = structural_simplify(model)
     prob = ODEProblem(sys, Pair[], (0.0, 100.0))
     sol = solve(prob, Rodas4())
@@ -188,15 +194,14 @@ end
     @test sol[plant.output.u][end]≈re_val atol=1e-3 # zero control error after 100s
 
     @testset "PI" begin
-        @named pid_controller = PID(k = 3, Ti = 0.5, Td = false)
+        @named pid_controller = PID("PI"; k = 3, Ti)
         @named model = ODESystem([
                 connect(ref.output, fb.input1),
                 connect(plant.output, fb.input2),
                 connect(fb.output, pid_controller.err_input),
                 connect(pid_controller.ctr_output, plant.input),
             ],
-            t,
-            systems = [pid_controller, plant, ref, fb])
+            t, [], [Ti]; systems = [pid_controller, plant, ref, fb])
         sys = structural_simplify(model)
         prob = ODEProblem(sys, Pair[], (0.0, 100.0))
         sol = solve(prob, Rodas4())
@@ -206,7 +211,7 @@ end
     end
 
     @testset "PD" begin
-        @named pid_controller = PID(k = 10, Ti = false, Td = 1)
+        @named pid_controller = PID("PD"; k = 10, Td = 1)
         @named model = ODESystem([
                 connect(ref.output, fb.input1),
                 connect(plant.output, fb.input2),
@@ -284,7 +289,8 @@ end
 @testset "LimPID" begin
     re_val = 1
     @named ref = Constant(; k = re_val)
-    @named pid_controller = LimPID(k = 3, Ti = 0.5, Td = 1 / 100, u_max = 1.5, u_min = -1.5,
+    @named pid_controller = LimPID(; k = 3, Ti = 0.5, Td = 1 / 100, u_max = 1.5,
+        u_min = -1.5,
         Ni = 0.1 / 0.5)
     @named plant = Plant()
     @named model = ODESystem([
@@ -305,7 +311,7 @@ end
     @test all(-1.5 .<= sol[pid_controller.ctr_output.u] .<= 1.5) # test limit
 
     @testset "PI" begin
-        @named pid_controller = LimPID(k = 3, Ti = 0.5, Td = false, u_max = 1.5,
+        @named pid_controller = LimPID(; k = 3, Ti = 0.5, Td = false, u_max = 1.5,
             u_min = -1.5, Ni = 0.1 / 0.5)
         @named model = ODESystem([
                 connect(ref.output, pid_controller.reference),
@@ -325,7 +331,7 @@ end
         @test all(-1.5 .<= sol[pid_controller.ctr_output.u] .<= 1.5) # test limit
     end
     @testset "PD" begin
-        @named pid_controller = LimPID(k = 10, Ti = false, Td = 1, u_max = 1.5,
+        @named pid_controller = LimPID(; k = 10, Ti = false, Td = 1, u_max = 1.5,
             u_min = -1.5)
         @named model = ODESystem([
                 connect(ref.output, pid_controller.reference),
@@ -346,7 +352,7 @@ end
     end
     @testset "set-point weights" begin
         @testset "wp" begin
-            @named pid_controller = LimPID(k = 3, Ti = 0.5, Td = 1 / 100, u_max = 1.5,
+            @named pid_controller = LimPID(; k = 3, Ti = 0.5, Td = 1 / 100, u_max = 1.5,
                 u_min = -1.5, Ni = 0.1 / 0.5, wp = 0, wd = 1)
             @named model = ODESystem([
                     connect(ref.output, pid_controller.reference),
@@ -367,7 +373,7 @@ end
             @test all(-1.5 .<= sol[pid_controller.ctr_output.u] .<= 1.5) # test limit
         end
         @testset "wd" begin
-            @named pid_controller = LimPID(k = 3, Ti = 0.5, Td = 1 / 100, u_max = 1.5,
+            @named pid_controller = LimPID(; k = 3, Ti = 0.5, Td = 1 / 100, u_max = 1.5,
                 u_min = -1.5, Ni = 0.1 / 0.5, wp = 1, wd = 0)
             @named model = ODESystem([
                     connect(ref.output, pid_controller.reference),
@@ -389,7 +395,7 @@ end
         end
     end
     @testset "PI without AWM" begin
-        @named pid_controller = LimPID(k = 3, Ti = 0.5, Td = false, u_max = 1.5,
+        @named pid_controller = LimPID(; k = 3, Ti = 0.5, Td = false, u_max = 1.5,
             u_min = -1.5, Ni = Inf)
         @named model = ODESystem([
                 connect(ref.output, pid_controller.reference),