add some joint assemblies

MWE

updates

src/Multibody.jl

@@ -1,5 +1,6 @@
 module Multibody
-
+# Find variables that are both array form and scalarized / collected
+# foreach(println, sort(unknowns(IRSystem(model)), by=string))
 using LinearAlgebra
 using ModelingToolkit
 using JuliaSimCompiler
@@ -172,6 +173,4 @@ include("robot/path_planning.jl")
 include("robot/robot_components.jl")
 include("robot/FullRobot.jl")
 
-
-
 end

src/components.jl

@@ -123,7 +123,7 @@ Can be thought of as a massless rod. For a massive rod, see [`BodyShape`](@ref)
 @component function FixedTranslation(; name, r, radius=0.02f0, color = purple)
  @named frame_a = Frame()
  @named frame_b = Frame()
- @parameters r[1:3]=r [
+ @parameters r[1:3]=collect(r) [
  description = "position vector from frame_a to frame_b, resolved in frame_a",
  ]
  r = collect(r)