Hello, I wrote a code that worked yesterday, but today the animation part did not work any longer:
using Timers
tic()
using ModelingToolkit, OrdinaryDiffEq, Parameters
using Plots
toc()
# 🔹 Define struct for simulation settings
@with_kw mutable struct SimulationSettings @deftype Float64
g_earth::Float64 = 0 # Gravity [m/s²]
k::Float64 = 1.0 # Spring constant [N/m]
m::Float64 = 1.0 # Mass of P2 and P3 [kg]
F2::Float64 = 1 # External force on P2 [N]
F3::Float64 = 1 # External force on P3 [N]
l1::Float64 = sqrt(5) # Rest length of spring P1-P2 [m]
l2::Float64 = 2.0 # Rest length of spring P2-P3 [m]
l3::Float64 = sqrt(5) # Rest length of spring P3-P1 [m]
duration::Float64 = 10.0 # Simulation time [s]
save::Bool = false # Whether to save animation frames
end
# Now, update the instance name:
se = SimulationSettings()
# 🔹 Define symbolic parameters (Using values from `Settings3`)
@parameters t k m g F2 F3 l1 l2 l3
# 🔹 Define symbolic state variables (positions & velocities)
@variables x2(t) y2(t) x3(t) y3(t) vx2(t) vy2(t) vx3(t) vy3(t)
# 🔹 Define differential operator
D = Differential(t)
# 🔹 Define Hooke’s Law for spring force
function spring_force(xa, ya, xb, yb, l)
dx = xb - xa
dy = yb - ya
length = sqrt(dx^2 + dy^2) # Compute current length
force_mag = k * (length - l) # Hooke’s Law: F = -k (x - L0)
fx = force_mag * dx / length
fy = force_mag * dy / length
return [fx, fy]
end
# 🔹 Define fixed anchor point P1 at (0,0)
x1, y1 = 0.0, 0.0
# 🔹 Compute forces symbolically
F_s1 = spring_force(x1, y1, x2, y2, l1) # Force from P1 to P2
F_s2 = spring_force(x2, y2, x3, y3, l2) # Force from P2 to P3
F_s3 = spring_force(x3, y3, x1, y1, l3) # Force from P3 to P1
# 🔹 Net forces on P2
Fx2 = -F_s1[1] + F_s2[1]
Fy2 = -F_s1[2] + F_s2[2] + F2
# 🔹 Net forces on P3
Fx3 = -F_s2[1] + F_s3[1]
Fy3 = -F_s2[2] + F_s3[2] + F3
# 🔹 Equations of motion using Newton's second law: F = ma
eqs = [
D(x2) ~ vx2,
D(y2) ~ vy2,
D(x3) ~ vx3,
D(y3) ~ vy3,
D(vx2) ~ Fx2 / m,
D(vy2) ~ (Fy2 - m * g) / m,
D(vx3) ~ Fx3 / m,
D(vy3) ~ (Fy3 - m * g) / m
]
# 🔹 Create an ODE system
@named sys = ODESystem(eqs, t, [x2, y2, x3, y3, vx2, vy2, vx3, vy3], [m, k, g, F2, F3, l1, l2, l3])
# 🔹 Parameter values from `Settings3`
params = Dict(
m => se.m,
k => se.k,
g => se.g_earth,
F2 => se.F2,
F3 => se.F3,
l1 => se.l1,
l2 => se.l2,
l3 => se.l3
)
# 🔹 Initial conditions
u0 = Dict(
x2 => -1.0, y2 => 2.0, x3 => 1.0, y3 => 2.0,
vx2 => 0.0, vy2 => 0.0, vx3 => 0.0, vy3 => 0.0
)
# 🔹 Time span
tspan = (0.0, se.duration)
# 🔹 Convert symbolic system to an ODEProblem
prob = ODEProblem(complete(sys), u0, tspan, params)
# 🔹 Solve numerically
sol = solve(prob, Tsit5(), saveat=0.05)
# 🔹 Extract the solution
x2_sol = sol[x2, :]
y2_sol = sol[y2, :]
x3_sol = sol[x3, :]
y3_sol = sol[y3, :]
# # 🔹 Create animation
# anim = @animate for i in eachindex(x2_sol)
# plot(xlim=(-1.5, 1.5), ylim=(-0.5, 6.0), legend=false, framestyle=:box, grid=false, size=(600, 600))
# # Scatter plot for mass points
# scatter!([0, x2_sol[i], x3_sol[i]], [0, y2_sol[i], y3_sol[i]], markersize=5, label="")
# # Spring connections
# plot!([0, x2_sol[i]], [0, y2_sol[i]], linewidth=2, color=:blue, label="") # P1-P2
# plot!([x2_sol[i], x3_sol[i]], [y2_sol[i], y3_sol[i]], linewidth=2, color=:red, label="") # P2-P3
# plot!([x3_sol[i], 0], [y3_sol[i], 0], linewidth=2, color=:green, label="") # P3-P1
# end
How can this be resolved?
Kind regards Friso
