neg_w everywhere and default

docs/src/examples/free_motion.md

@@ -48,7 +48,7 @@ If we instead model a body suspended in springs without the presence of any join
 using Multibody.Rotations: QuatRotation, RotXYZ, params
 @named begin
  body = BodyShape(m = 1, I_11 = 1, I_22 = 1, I_33 = 1, r = [0.4, 0, 0],
- r_0 = [0.2, -0.5, 0.1], isroot = true, quat=true, neg_w=true)
+ r_0 = [0.2, -0.5, 0.1], isroot = true, quat=true)
  bar2 = FixedTranslation(r = [0.8, 0, 0])
  spring1 = Multibody.Spring(c = 20, s_unstretched = 0)
  spring2 = Multibody.Spring(c = 20, s_unstretched = 0)

docs/src/examples/three_springs.md

@@ -20,7 +20,7 @@ world = Multibody.world
 
 systems = @named begin
  body1 = Body(m = 0.8, I_11 = 0.1, I_22 = 0.1, I_33 = 0.1, r_0 = [0.5, -0.3, 0],
- r_cm = [0, -0.2, 0], isroot=true, quat=true, neg_w=true)
+ r_cm = [0, -0.2, 0], isroot=true, quat=true)
  bar1 = FixedTranslation(r = [0.3, 0, 0])
  bar2 = FixedTranslation(r = [0, 0, 0.3])
  spring1 = Multibody.Spring(c = 20, m = 0, s_unstretched = 0.1, fixed_rotation_at_frame_b=true,

src/components.jl

@@ -236,7 +236,7 @@ This component has a single frame, `frame_a`. To represent bodies with more than
  isroot = false,
  state = false,
  sequence = [1,2,3],
- neg_w = false,
+ neg_w = true,
  phi0 = zeros(3),
  phid0 = zeros(3),
  r_0 = 0,
@@ -267,7 +267,7 @@ This component has a single frame, `frame_a`. To represent bodies with more than
  ]
  @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+2quat*state,
+ state_priority = state_priority-1+2quat*state,
  description = "Absolute angular velocity of frame_a resolved in frame_a",
  ]
  @variables z_a(t)[1:3] [guess = 0, 
@@ -619,7 +619,7 @@ Rigid body with cylinder shape. The mass properties of the body (mass, center of
  state = false
  quat = false
  sequence = [1,2,3]
- neg_w = false
+ neg_w = true
  end
 
  @parameters begin

src/joints.jl

@@ -179,7 +179,7 @@ Joint with 3 constraints that define that the origin of `frame_a` and the origin
  z_rel_a_fixed = false, sequence = [1, 2, 3], phi = 0,
  phid = 0,
  d = 0,
- neg_w = false,
+ neg_w = true,
  phidd = 0,
  color = [1, 1, 0, 1],
  radius = 0.1,
@@ -720,7 +720,7 @@ The relative position vector `r_rel_a` from the origin of `frame_a` to the origi
  state_priority = 4,
  phid = 0,
  phidd = 0,
- neg_w = false,
+ neg_w = true,
  w_rel_b = 0,
  r_rel_a = 0,
  v_rel_a = 0,

test/runtests.jl

@@ -68,7 +68,7 @@ t = Multibody.t
 D = Differential(t)
 @testset "spring - harmonic oscillator" begin
 
- @named body = Body(; m = 1, isroot = true, r_cm = [0, 1, 0], quat=false) # This time the body isroot since there is no joint containing state
+ @named body = Body(; m = 1, isroot = true, r_cm = [0, -1, 0], quat=true, neg_w=true) # This time the body isroot since there is no joint containing state
  @named spring = Multibody.Spring(c = 1)
 
  connections = [connect(world.frame_b, spring.frame_a)
@@ -87,10 +87,11 @@ D = Differential(t)
 
  # @test_skip begin # Yingbo: instability
  prob = ODEProblem(ssys, [
- collect(body.w_a) .=> 0.01;
+ collect(body.r_0) .=> [0, -1e-5, 0]; # To make sure the spring has non-zero extent
+ collect(body.w_a) .=> 0.00;
  collect(body.v_0) .=> 0;
  ], (0, 10))
- sol = solve(prob, Rodas5P(), u0 = prob.u0 .+ 1e-5 .* randn.())
+ sol = solve(prob, Rodas5P(), u0 = prob.u0 .+ 0*1e-5 .* randn.())
  @test SciMLBase.successful_retcode(sol)
  @test sol(2pi, idxs = body.r_0[1])≈0 atol=1e-3
  @test sol(2pi, idxs = body.r_0[2])≈0 atol=1e-3