add Cylindrical (#115)

* add Cylindrical

* wip

* add test

* update default state priorities

Author: baggepinnen

src/Multibody.jl

@@ -155,7 +155,7 @@ export World, world, Mounting1D, Fixed, FixedTranslation, FixedRotation, Body, B
 include("components.jl")
 
 export Revolute, Prismatic, Planar, Spherical, Universal,
-GearConstraint, RollingWheelJoint, RollingWheel, FreeMotion, RevolutePlanarLoopConstraint
+GearConstraint, RollingWheelJoint, RollingWheel, FreeMotion, RevolutePlanarLoopConstraint, Cylindrical
 include("joints.jl")
 
 export SphericalSpherical, UniversalSpherical, JointUSR, JointRRR

src/components.jl

@@ -266,12 +266,11 @@ This component has a single frame, `frame_a`. To represent bodies with more than
         description = "Absolute velocity of frame_a, resolved in world frame (= D(r_0))",
     ]
     @variables a_0(t)[1:3] [guess = 0, 
-        state_priority = state_priority+isroot,
         description = "Absolute acceleration of frame_a resolved in world frame (= D(v_0))",
     ]
     @variables g_0(t)[1:3] [guess = 0, description = "gravity acceleration"]
     @variables w_a(t)[1:3]=w_a [guess = 0, 
-        state_priority = state_priority-1+2quat*state,
+        state_priority = isroot ? quat ? state_priority : -1 : 0,
         description = "Absolute angular velocity of frame_a resolved in frame_a",
     ]
     @variables z_a(t)[1:3] [guess = 0, 

src/joints.jl

@@ -24,7 +24,7 @@ If `axisflange`, flange connectors for ModelicaStandardLibrary.Mechanics.Rotatio
 """
 @component function Revolute(; name, phi0 = 0, w0 = 0, n = Float64[0, 0, 1], axisflange = false,
                   isroot = true, iscut = false, radius = 0.05, length = radius, color = [0.5019608f0,0.0f0,0.5019608f0,1.0f0], state_priority = 3.0)
-    if !(eltype(n) <: Num)
+    if !(eltype(n) <: Num) && !isa(n, Symbolics.Arr{Num, 1})
         norm(n) ≈ 1 || error("Axis of rotation must be a unit vector")
     end
     @named frame_a = Frame()
@@ -37,7 +37,7 @@ If `axisflange`, flange connectors for ModelicaStandardLibrary.Mechanics.Rotatio
     end
     @variables tau(t)=0 [
         connect = Flow,
-        state_priority = 2,
+        # state_priority = 2,
         description = "Driving torque in direction of axis of rotation",
     ]
     @variables phi(t)=phi0 [
@@ -102,8 +102,8 @@ If `axisflange`, flange connectors for ModelicaStandardLibrary.Mechanics.Transla
 The function returns an ODESystem representing the prismatic joint.
 """
 @component function Prismatic(; name, n = Float64[0, 0, 1], axisflange = false,
-                   s0 = 0, v0 = 0, radius = 0.05, color = [0,0.8,1,1], state_priority=10, iscut=false)
-    if !(eltype(n) <: Num)
+                   s0 = 0, v0 = 0, radius = 0.05, color = [0,0.8,1,1], state_priority=10, iscut=false, render=true)
+    if !(eltype(n) <: Num) && !isa(n, Symbolics.Arr{Num, 1})
         norm(n) ≈ 1 || error("Prismatic axis of motion must be a unit vector, got norm(n) = $(norm(n))")
     end
     @named frame_a = Frame()
@@ -114,6 +114,7 @@ The function returns an ODESystem representing the prismatic joint.
     pars = @parameters begin
         radius = radius, [description = "radius of the joint in animations"]
         color[1:4] = color, [description = "color of the joint in animations (RGBA)"]
+        render = render, [description = "render the joint in animations"]
     end
 
     @variables s(t)=s0 [
@@ -125,7 +126,6 @@ The function returns an ODESystem representing the prismatic joint.
         description = "Relative velocity between frame_a and frame_b",
     ]
     @variables a(t)=0 [
-        state_priority = state_priority,
         description = "Relative acceleration between frame_a and frame_b",
     ]
     @variables f(t)=0 [
@@ -987,3 +987,54 @@ s_y=prismatic_y.s=0` and `phi=revolute.phi=0`.
         connect(revolute.frame_b, frame_b)
     end
 end
+
+@mtkmodel Cylindrical begin
+    begin
+        n_def = [1, 0, 0] # Workaround for mtkmodel bug
+        cylinder_color_def = [1, 0, 1, 1]
+    end
+
+    @structural_parameters begin
+        # _state_priority = 2 # mtkmodel bug prevents this from being any form of parameter at all :/
+        cylinder_color = [1, 0, 1, 1]#, [description = "Color of cylinder"]
+    end
+
+    @parameters begin
+        n[1:3] = n_def, [description = "Cylinder axis resolved in frame_a (= same as in frame_b)"]
+        cylinder_diameter = 0.05, [description = "Diameter of cylinder"]
+        render = true, [description = "Enable rendering of the joint in animations"]
+    end
+    begin
+        n = collect(n)
+        cylinder_color = collect(cylinder_color)
+    end
+
+    @components begin
+        frame_a = Frame()
+        frame_b = Frame()
+        prismatic = Prismatic(; n, state_priority=1, render = false)
+        revolute = Revolute(; n, state_priority=1, color = cylinder_color, radius = cylinder_diameter/2)
+    end
+
+    @variables begin
+        (s(t) = 0), [state_priority = 200, description = "Relative distance between frame_a and frame_b"]
+        (phi(t) = 0), [state_priority = 200, description = "Relative rotation angle from frame_a to frame_b"]
+        (v(t) = 0), [state_priority = 200, description = "First derivative of s (relative velocity)"]
+        (w(t) = 0), [state_priority = 200, description = "First derivative of angle phi (relative angular velocity)"]
+        (a(t) = 0), [description = "Second derivative of s (relative acceleration)"]
+        (wd(t) = 0), [description = "Second derivative of angle phi (relative angular acceleration)"]
+    end
+
+    @equations begin
+        phi ~ revolute.phi
+        w ~ D(phi)
+        wd ~ D(w)
+        s ~ prismatic.s
+        v ~ D(s)
+        a ~ D(v)
+        connect(frame_a, prismatic.frame_a)
+        connect(prismatic.frame_b, revolute.frame_a)
+        connect(revolute.frame_b, frame_b)
+    end
+
+end

test/runtests.jl

@@ -1285,4 +1285,32 @@ sol = solve(prob, Rodas4())
     include("test_fourbar.jl")
 end
 
-## =============================================================================
+## =============================================================================
+# using Plots
+# Test cylindrical joint
+@mtkmodel CylinderTest begin
+    @components begin
+        world = W()
+        cyl = Cylindrical(n = [0, 1, 0])
+        # spring = Spring(c = 1)
+        body = Body(state_priority=0)
+    end
+    @equations begin
+        # connect(world.frame_b, cyl.frame_a, spring.frame_a)
+        # connect(cyl.frame_b, spring.frame_b, body.frame_a)
+
+        connect(world.frame_b, cyl.frame_a)
+        connect(cyl.frame_b, body.frame_a)
+    end
+end
+@named model = CylinderTest()
+model = complete(model)
+ssys = structural_simplify(IRSystem(model))
+prob = ODEProblem(ssys, [
+    model.cyl.revolute.w => 1
+], (0, 1))
+sol = solve(prob, Rodas4())
+# plot(sol)
+@test sol[model.cyl.v][end] ≈ -9.81 atol=0.01
+@test sol[model.cyl.phi][end] ≈ 1 atol=0.01
+