a bit of tidying

src/Mechanical/PlanarMechanics/components.jl

@@ -12,6 +12,8 @@ Frame fixed in the planar world frame at a given position and orientation
 # Connectors:
 
   - `frame: 2-dim. Coordinate system
+
+https://github.com/dzimmer/PlanarMechanics/blob/743462f58858a808202be93b708391461cbe2523/PlanarMechanics/Parts/Fixed.mo
 """
 @mtkmodel Fixed begin
     @parameters begin
@@ -58,12 +60,14 @@ Body component with mass and inertia
 # Connectors:
 
   - `frame`: 2-dim. Coordinate system
+
+https://github.com/dzimmer/PlanarMechanics/blob/743462f58858a808202be93b708391461cbe2523/PlanarMechanics/Parts/Body.mo
 """
-@component function Body(; name, m, j, rx = 0, ry = 0, gy = -9.807)
+@component function Body(; name, m, I, rx = 0, ry = 0, gy = -9.807)
     @named frame = Frame()
     pars = @parameters begin
         m = m
-        j = j
+        I = I
         gy = gy
     end
 
@@ -98,7 +102,7 @@ Body component with mass and inertia
         fy ~ frame.fy,
         ax ~ fx / m,
         ay ~ ifelse(gy !== nothing, fy / m + gy, fy / m),
-        j * α ~ frame.j,
+        I * α ~ frame.j,
     ]
 
     return compose(ODESystem(eqs, t, vars, pars; name = name),
@@ -119,6 +123,8 @@ A fixed translation between two components (rigid rod)
     
     - `frame_a` [Frame](@ref) Coordinate system fixed to the component with one cut-force and cut-torque
     - `frame_b` [Frame](@ref) Coordinate system fixed to the component with one cut-force and cut-torque
+
+https://github.com/dzimmer/PlanarMechanics/blob/743462f58858a808202be93b708391461cbe2523/PlanarMechanics/Parts/FixedTranslation.mo
 """
 @mtkmodel FixedTranslation begin
     @extend frame_a, frame_b = partial_frames = PartialTwoFrames()
@@ -148,7 +154,7 @@ A fixed translation between two components (rigid rod)
         # balancing force including lever principle
         frame_a.fx + frame_b.fx ~ 0
         frame_a.fy + frame_b.fy ~ 0
-        frame_a.j + frame_b.j + r0[1] * frame_b.fy - r0[2] * frame_b.fx ~ 0
+        frame_a.j + frame_b.j + r0' * [frame_b.fy, -frame_b.fx] ~ 0
     end
 end
 

src/Mechanical/PlanarMechanics/joints.jl

@@ -20,6 +20,7 @@ A revolute joint
   - `flange_a` [Flange](@ref) if `use_flange == true`
   - `support` [Support](@ref) if `use_flange == true`
 
+https://github.com/dzimmer/PlanarMechanics/blob/743462f58858a808202be93b708391461cbe2523/PlanarMechanics/Joints/Revolute.mo
 """
 @component function Revolute(;
         name,
@@ -96,6 +97,8 @@ A prismatic joint
   - `fixed` [Fixed](@ref) if `use_flange == false`
   - `flange_a` [Flange](@ref) if `use_flange == true`
   - `support` [Support](@ref) if `use_flange == true`
+
+https://github.com/dzimmer/PlanarMechanics/blob/743462f58858a808202be93b708391461cbe2523/PlanarMechanics/Joints/Prismatic.mo
 """
 @component function Prismatic(;
         name,

test/Mechanical/planar_mechanics.jl

@@ -1,3 +1,5 @@
+# using Revise
+# using Plots
 using ModelingToolkit, OrdinaryDiffEq, Test
 using ModelingToolkitStandardLibrary.Mechanical.PlanarMechanics
 
@@ -9,8 +11,8 @@ g = -9.807
 @testset "Free body" begin
     # https://github.com/dzimmer/PlanarMechanics/blob/743462f58858a808202be93b708391461cbe2523/PlanarMechanics/Examples/FreeBody.mo
     m = 2
-    j = 1
-    @named body = Body(; m, j)
+    I = 1
+    @named body = Body(; m, I)
     @named model = ODESystem(Equation[],
         t,
         [],
@@ -34,7 +36,7 @@ end
     # https://github.com/dzimmer/PlanarMechanics/blob/743462f58858a808202be93b708391461cbe2523/PlanarMechanics/Examples/Pendulum.mo
     @named ceiling = Fixed()
     @named rod = FixedTranslation(rx = 1.0, ry = 0.0)
-    @named body = Body(m = 1, j = 0.1)
+    @named body = Body(m = 1, I = 0.1)
     @named revolute = Revolute()
 
     connections = [
@@ -50,7 +52,12 @@ end
         systems = [body, revolute, rod, ceiling])
     sys = structural_simplify(model)
 
-    @test length(states(sys)) == 7
+    @test_broken length(states(sys)) == 2
+    unset_vars = setdiff(states(sys), keys(ModelingToolkit.defaults(sys)))
+    prob = ODEProblem(sys, unset_vars .=> 0.0, tspan, []; jac = true)
+
+    sol = solve(prob, Rodas5P())
+    @test_broken SciMLBase.successful_retcode(sol)
 end
 
 @testset "Prismatic" begin
@@ -61,12 +68,12 @@ end
 @testset "AbsoluteAccCentrifugal" begin
     # https://github.com/dzimmer/PlanarMechanics/blob/443b007bcc1522bb172f13012e2d7a8ecc3f7a9b/PlanarMechanicsTest/Sensors.mo#L221-L332
     m = 1
-    j = 0.1
+    I = 0.1
     ω = 10
     resolve_in_frame = :world
 
     # components
-    @named body = Body(; m, j, gy = 0.0)
+    @named body = Body(; m, I, gy = 0.0)
     @named fixed_translation = FixedTranslation(; rx = 10.0, ry = 0.0)
     @named fixed = Fixed()
     @named revolute = Revolute(constant_ω = ω)
@@ -114,11 +121,11 @@ end
 
 @testset "Sensors (two free falling bodies)" begin
     m = 1
-    j = 1
+    I = 1
     resolve_in_frame = :world
 
-    @named body1 = Body(; m, j)
-    @named body2 = Body(; m, j)
+    @named body1 = Body(; m, I)
+    @named body2 = Body(; m, I)
     @named base = Fixed()
 
     @named abs_pos_sensor = AbsolutePosition(; resolve_in_frame)
@@ -209,10 +216,10 @@ end
 
 @testset "Measure Demo" begin
     # https://github.com/dzimmer/PlanarMechanics/blob/743462f58858a808202be93b708391461cbe2523/PlanarMechanics/Examples/MeasureDemo.mo
-    @named body = Body(; m = 1, j = 0.1)
+    @named body = Body(; m = 1, I = 0.1)
     @named fixed_translation = FixedTranslation(; rx = 1, ry = 0)
     @named fixed = Fixed()
-    @named body1 = Body(; m = 0.4, j = 0.02)
+    @named body1 = Body(; m = 0.4, I = 0.02)
     @named fixed_translation1 = FixedTranslation(; rx = 0.4, ry = 0)
     @named abs_pos_sensor = AbsolutePosition(; resolve_in_frame = :world)
     @named rel_pos_sensor = RelativePosition(; resolve_in_frame = :world)
@@ -274,7 +281,7 @@ end
         c_x = 5,
         d_x = 1,
         c_phi = 0)
-    @named body = Body(; j = 0.1, m = 0.5, rx = 1, ry = 1)
+    @named body = Body(; I = 0.1, m = 0.5, rx = 1, ry = 1)
     @named fixed = Fixed()
     @named fixed_translation = FixedTranslation(; rx = -1, ry = 0)
 
@@ -302,7 +309,7 @@ end
 
 @testset "Spring and damper demo" begin
     # https://github.com/dzimmer/PlanarMechanics/blob/743462f58858a808202be93b708391461cbe2523/PlanarMechanics/Examples/SpringDemo.mo
-    @named body = Body(; m = 0.5, j = 0.1)
+    @named body = Body(; m = 0.5, I = 0.1)
     @named fixed = Fixed()
     @named spring = Spring(; c_y = 10, s_rely0 = -0.5, c_x = 1, c_phi = 1e5)
     @named damper = Damper(d = 1)