Merge pull request #307 from SciML/zero_defaults

Reduce the extra initial conditions on Translational components

src/Hydraulic/IsothermalCompressible/components.jl

@@ -30,7 +30,7 @@ end
 
     vars = @variables begin
         p(t) = p_int
-        dm(t) = 0
+        dm(t)
     end
 
     systems = @named begin
@@ -79,7 +79,7 @@ Variable length internal flow model of the fully developed incompressible flow f
 
     @variables begin
         x(t) = length_int
-        ddm(t) = 0
+        ddm(t)
     end
 
     vars = []
@@ -242,8 +242,8 @@ Reduces the flow from `port_a` to `port_b` by `n`.  Useful for modeling parallel
     end
 
     vars = @variables begin
-        dm_a(t) = 0
-        dm_b(t) = 0
+        dm_a(t)
+        dm_b(t)
     end
 
     systems = @named begin
@@ -373,9 +373,9 @@ end
 
     vars = @variables begin
         x(t) = x_int
-        dx(t) = 0
+        dx(t)
         rho(t) = liquid_density(port)
-        drho(t) = 0
+        drho(t)
         vol(t) = dead_volume + area * x_int
     end
 
@@ -416,7 +416,7 @@ Fixed fluid volume.
 
     vars = @variables begin
         rho(t) = liquid_density(port)
-        drho(t) = 0
+        drho(t)
     end
 
     # let
@@ -717,7 +717,7 @@ end
 
     vars = @variables begin
         x(t) = x_int
-        dx(t) = 0
+        dx(t)
     end
 
     eqs = [D(x) ~ dx
@@ -822,7 +822,7 @@ end
 
     vars = @variables begin
         x(t) = x_int
-        dx(t) = 0
+        dx(t)
     end
 
     total_length = length_a_int + length_b_int

src/Mechanical/MultiBody2D/components.jl

@@ -9,35 +9,35 @@
     end
 
     @variables begin
-        (A(t) = 0), [state_priority = 10]
-        (dA(t) = 0), [state_priority = 10]
-        (ddA(t) = 0), [state_priority = 10]
+        (A(t)), [state_priority = 10]
+        (dA(t)), [state_priority = 10]
+        (ddA(t)), [state_priority = 10]
 
-        fx1(t) = 0
-        fy1(t) = 0
+        fx1(t)
+        fy1(t)
 
-        fx2(t) = 0
-        fy2(t) = 0
+        fx2(t)
+        fy2(t)
 
         x1(t) = x1_0
-        dx1(t) = 0
+        dx1(t)
 
         y1(t) = y1_0
-        dy1(t) = 0
+        dy1(t)
 
         x2(t) = l + x1_0
-        dx2(t) = 0
+        dx2(t)
 
-        y2(t) = 0
-        dy2(t) = 0
+        y2(t)
+        dy2(t)
 
         x_cm(t) = l / 2 + x1_0
-        dx_cm(t) = 0
-        ddx_cm(t) = 0
+        dx_cm(t)
+        ddx_cm(t)
 
-        y_cm(t) = 0
-        dy_cm(t) = 0
-        ddy_cm(t) = 0
+        y_cm(t)
+        dy_cm(t)
+        ddy_cm(t)
     end
 
     @components begin

src/Mechanical/Translational/components.jl

@@ -66,7 +66,7 @@ Sliding mass with inertia
 
     vars = @variables begin
         v(t) = v
-        f(t) = 0
+        f(t)
     end
 
     eqs = [flange.v ~ v
@@ -123,7 +123,7 @@ end # default
     end
     vars = @variables begin
         delta_s(t) = delta_s
-        f(t) = 0
+        f(t)
     end
 
     @named flange_a = MechanicalPort(; v = flange_a__v)
@@ -148,7 +148,7 @@ const ABS = Val(:absolute)
     vars = @variables begin
         sa(t) = sa
         sb(t) = sb
-        f(t) = 0
+        f(t)
     end
 
     @named flange_a = MechanicalPort(; v = flange_a__v)

src/Mechanical/Translational/sources.jl

@@ -88,7 +88,7 @@ Linear 1D position input source.  Set `solves_force=false` to force input force
         a = RealInput()
     end
 
-    vars = @variables v(t) = 0
+    vars = @variables v(t)
 
     eqs = [v ~ flange.v
            D(v) ~ a.u]

src/Mechanical/TranslationalModelica/components.jl

@@ -48,8 +48,8 @@ Sliding mass with inertia
         m = 0.0, [description = "Mass of sliding mass [kg]"]
     end
     @variables begin
-        v(t) = 0.0, [description = "Absolute linear velocity of sliding mass [m/s]"]
-        a(t) = 0.0, [description = "Absolute linear acceleration of sliding mass [m/s^2]"]
+        v(t), [description = "Absolute linear velocity of sliding mass [m/s]"]
+        a(t), [description = "Absolute linear acceleration of sliding mass [m/s^2]"]
     end
     @extend flange_a, flange_b, s = pr = PartialRigid(; L = 0.0, s)
     @equations begin
@@ -106,7 +106,7 @@ Linear 1D translational damper
         d = 0.0, [description = "Damping constant [Ns/m]"]
     end
     @variables begin
-        lossPower(t) = 0.0, [description = "Power dissipated by the damper [W]"]
+        lossPower(t), [description = "Power dissipated by the damper [W]"]
     end
     @equations begin
         f ~ d * v_rel

src/Mechanical/TranslationalModelica/utils.jl

@@ -46,8 +46,8 @@ Partial model for the compliant connection of two translational 1-dim. flanges.
 @mtkmodel PartialCompliant begin
     @extend (flange_a, flange_b) = pt = PartialTwoFlanges()
     @variables begin
-        s_rel(t) = 0.0, [description = "Relative distance between flanges"]
-        f(t) = 0.0, [description = "Force between flanges"]
+        s_rel(t), [description = "Relative distance between flanges", guess = 0.0]
+        f(t), [description = "Force between flanges", guess = 0.0]
     end
 
     @equations begin
@@ -71,9 +71,9 @@ Partial model for the compliant connection of two translational 1-dim. flanges.
 @mtkmodel PartialCompliantWithRelativeStates begin
     @extend flange_a, flange_b = pt = PartialTwoFlanges()
     @variables begin
-        s_rel(t) = 0.0, [description = "Relative distance between flanges"]
-        v_rel(t) = 0.0, [description = "Relative linear velocity))"]
-        f(t) = 0.0, [description = "Forces between flanges"]
+        s_rel(t), [description = "Relative distance between flanges"]
+        v_rel(t), [description = "Relative linear velocity))"]
+        f(t), [description = "Forces between flanges"]
     end
 
     @equations begin
@@ -149,7 +149,7 @@ end
 @mtkmodel PartialRigid begin
     @extend flange_a, flange_b = ptf = PartialTwoFlanges()
     @variables begin
-        s(t) = 0.0, [description = "Absolute position of center of component"]
+        s(t), [description = "Absolute position of center of component"]
     end
     @parameters begin
         L = 0.0, [description = "Length of component, from left flange to right flange"]

src/Thermal/utils.jl

@@ -1,6 +1,6 @@
 @connector HeatPort begin
     T(t) = 273.15 + 20.0
-    Q_flow(t) = 0.0, [connect = Flow]
+    Q_flow(t), [connect = Flow]
 end
 Base.@doc """
     HeatPort(; name, T = 273.15 + 20.0, Q_flow = 0.0)

test/Mechanical/translational_modelica.jl

@@ -1,55 +1,58 @@
 using ModelingToolkit, OrdinaryDiffEq, Test
 using ModelingToolkit: t_nounits as t, D_nounits as D
 
-using ModelingToolkitStandardLibrary.Blocks
-import ModelingToolkitStandardLibrary.Mechanical.TranslationalModelica as TP
+using ModelingToolkitStandardLibrary.Blocks: Sine
+using ModelingToolkitStandardLibrary.Mechanical.TranslationalModelica: Damper, Spring, Mass,
+                                                                       Fixed, Force
 
 @testset "spring damper mass fixed" begin
-    @named damper = TP.Damper(; d = 1)
-    @named spring = TP.Spring(; c = 1, s_rel0 = 1)
-    @named mass = TP.Mass(; m = 1, v = 1)
-    @named fixed = TP.Fixed(s0 = 1)
-
-    eqs = [connect(spring.flange_a, mass.flange_a, damper.flange_a)
-           connect(spring.flange_b, damper.flange_b, fixed.flange)]
-
-    @named model = ODESystem(eqs, t; systems = [fixed, mass, spring, damper])
-
-    sys = structural_simplify(model)
-
-    foreach(println, full_equations(sys))
+    @mtkmodel SpringDamperMassFixed begin
+        @components begin
+            damper = Damper(; d = 1)
+            spring = Spring(; c = 1, s_rel0 = 1)
+            mass = Mass(; m = 1, v = 1, s = 0)
+            fixed = Fixed(s0 = 1)
+        end
+        @equations begin
+            connect(spring.flange_a, mass.flange_a, damper.flange_a)
+            connect(spring.flange_b, damper.flange_b, fixed.flange)
+        end
+    end
+
+    @mtkbuild sys = SpringDamperMassFixed()
 
     prob = ODEProblem(sys, [], (0, 20.0), [])
     sol = solve(prob, ImplicitMidpoint(), dt = 0.01)
 
-    @test sol[mass.v][1] == 1.0
-    @test sol[mass.v][end]≈0.0 atol=1e-4
+    @test sol[sys.mass.v][1] == 1.0
+    @test sol[sys.mass.v][end]≈0.0 atol=1e-4
 end
 
 @testset "driven spring damper mass" begin
-    @named damper = TP.Damper(; d = 1)
-    @named spring = TP.Spring(; c = 1, s_rel0 = 1)
-    @named mass = TP.Mass(; m = 1, v = 1)
-    @named fixed = TP.Fixed(; s0 = 1)
-    @named force = TP.Force()
-    @named source = Sine(frequency = 3, amplitude = 2)
-
-    eqs = [connect(force.f, source.output)
-           connect(force.flange, mass.flange_a)
-           connect(spring.flange_a, mass.flange_b, damper.flange_a)
-           connect(spring.flange_b, damper.flange_b, fixed.flange)]
-
-    @named model = ODESystem(eqs, t;
-        systems = [fixed, mass, spring, damper, force, source])
-
-    sys = structural_simplify(model)
-
-    foreach(println, full_equations(sys))
+    @mtkmodel DrivenSpringDamperMass begin
+        @components begin
+            damper = Damper(; d = 1)
+            spring = Spring(; c = 1, s_rel0 = 1)
+            mass = Mass(; m = 1, v = 1, s = 0)
+            fixed = Fixed(; s0 = 1)
+            force = Force()
+            source = Sine(frequency = 3, amplitude = 2)
+        end
+
+        @equations begin
+            connect(force.f, source.output)
+            connect(force.flange, mass.flange_a)
+            connect(spring.flange_a, mass.flange_b, damper.flange_a)
+            connect(spring.flange_b, damper.flange_b, fixed.flange)
+        end
+    end
+
+    @mtkbuild sys = DrivenSpringDamperMass()
 
     prob = ODEProblem(sys, [], (0, 20.0), [])
     sol = solve(prob, Rodas4())
 
-    lb, ub = extrema(sol(15:0.05:20, idxs = mass.v).u)
+    lb, ub = extrema(sol(15:0.05:20, idxs = sys.mass.v).u)
     @test -lb≈ub atol=1e-2
     @test -0.11 < lb < -0.1
 end