SIMPACK Multibody Dynamics (.spck, .sim, .mbs) ​

ModelScript integrates native support for SIMPACK (Dassault Systèmes), the premier high-frequency vibration, kinematic, and spatial multibody dynamics (MBD) simulation system.

Capabilities ​

• Modern & Classic Ingestion:
  • Ingests modern SIMPACK XML models (.spck) containing <body/>, <marker/>, and <joint/> tags.
  • Ingests classic ASCII keyword decks (.sim, .mbs) with $BODY, $MARKER, and $JOINT cards.
• Grübler-Kutzbach Mobility Analysis:
  • Calculates mechanism degrees of freedom ($M=6n-\sum c_i$) in 3D spatial mechanisms.
  • Automatically identifies overconstrained kinematic loops ($M<0$).
• WebAssembly Kinematics Kernel:
  • Zero-allocation AssemblyScript linear memory kernel (kinematics.wasm) evaluating 3D Euler/Cardan rotation matrices, Rodrigues rotation, and spatial joint constraint equations (revolute, spherical, prismatic, cylindrical, planar, universal).
  • High-throughput batched transformations and residual evaluations.
• Closed Kinematic Chains:
  • Evaluates cut-joint loop closure residual vectors for spatial mechanisms.
• Direct DAE Lowering:
  • Lowers 3D translational and rotational kinematic relations directly into DAEBuilder in linear WebAssembly memory.
• FMI 2.0 / 3.0 Co-Simulation FMU Export:
  • Packages complete multibody assemblies into standalone .fmu archives with modelDescription.xml, C co-simulation wrappers, and kinematic state telemetry.
• Interactive 3D Viewport:
  • WebGL/Three.js 3D visualization rendering rigid bodies, joint couplings, coordinate markers, and spring elements with orbit navigation.
• Modelica Projection:
  • Automatically translates SIMPACK mechanisms into standard Modelica.Mechanics.MultiBody components.

CLI Usage ​

# Check structural references and joints
msx simpack lint mechanism.spck

# Analyze degrees of freedom and overconstrained loops
msx simpack mobility mechanism.spck

# Direct DAE simulation in WebAssembly arena with CSV trajectory export
msx simpack simulate suspension.spck --stop-time=5.0 --step=0.005 --out=results.csv

# Export mechanism as an FMI 2.0/3.0 Co-Simulation FMU
msx simpack to-fmu suspension.spck --out=Suspension.fmu

# Export mechanism to standard Modelica MultiBody
msx simpack to-modelica suspension.sim --out=Suspension.mo

Benchmarks ​

• Automotive Double-Wishbone Suspension (languages/simpack/testsuite/DoubleWishbone.spck):
  • 5 moving bodies (lower control arm, upper control arm, wheel hub, tie rod, chassis mount), 12 markers, 5 spatial joints, and coilover spring-damper strut.
  • Mobility analysis verifies $M=9$ spatial DOFs (6 free chassis DOFs, 1 vertical jounce DOF, 1 steering DOF, 1 wheel spin DOF).

MCP Tools ​

AI agents interacting via the ModelScript MCP server have access to:

• simpack_lint: Checks marker references, parent bodies, and joint validity.
• simpack_mobility: Evaluates Grübler-Kutzbach spatial degrees of freedom and overconstraint status.

Diagnostic Rules ​