add PlanarMechanics module

originally implemented in SciML/ModelingToolkitStandardLibrary.jl#220

src/Multibody.jl

@@ -210,5 +210,7 @@ include("robot/robot_components.jl")
 include("robot/FullRobot.jl")
 
 
+export PlanarMechanics
+include("PlanarMechanics/PlanarMechanics.jl")
 
 end

src/PlanarMechanics/PlanarMechanics.jl

@@ -0,0 +1,27 @@
+"""
+Library to model planar mechanical multi-body systems inspired by https://github.com/dzimmer/PlanarMechanics
+"""
+
+module PlanarMechanics
+
+import ModelingToolkitStandardLibrary.Mechanical.Rotational
+import ModelingToolkitStandardLibrary.Mechanical.TranslationalModelica
+using ModelingToolkit: t_nounits as t, D_nounits as D
+using ModelingToolkit
+using ...Blocks: RealInput, RealOutput
+import ...@symcheck
+
+export Frame, FrameResolve, PartialTwoFrames, ZeroPosition
+include("utils.jl")
+
+export Fixed, Body, FixedTranslation, Spring, Damper, SpringDamper
+include("components.jl")
+
+export Revolute, Prismatic
+include("joints.jl")
+
+export AbsolutePosition,
+       RelativePosition, AbsoluteVelocity, RelativeVelocity, AbsoluteAcceleration,
+       RelativeAcceleration, connect_sensor
+include("sensors.jl")
+end