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MotionSolve Reference Guide
This manual provides a detailed list and usage information regarding command statements, model statements, functions and the Subroutine Interface available in MotionSolve.
The Subroutine Interface for MotionSolve
Types of User-Written Subroutines
To facilitate the creation of solver extensions, MotionSolve provides you with a well-defined interface and a well-defined methodology for creating user subroutines.
Modeling Subroutines
Modeling subroutines are user-written subroutines that allow you define the run-time behavior of a modeling element via a user subroutine.

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Overview
MotionSolve^® is an integrated solution to analyze, evaluate, and optimize the performance of multibody systems.
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MotionSolve User Guide
MotionSolve is a system level, multibody solver that is based on the principles of mechanics.
MotionSolve Reference Guide
This manual provides a detailed list and usage information regarding command statements, model statements, functions and the Subroutine Interface available in MotionSolve.
- Notation and Syntax
- Creating MotionSolve XML Files
- Writing Custom Elements for MotionSolve
- Writing Custom Functions for MotionSolve
- Supported Versions - Third Party Software
- Command Statements
- Model Statements
- Functions
- The Subroutine Interface for MotionSolve
  - User Subroutines and MotionSolve
  - System Requirements
  - Types of User-Written Subroutines
    To facilitate the creation of solver extensions, MotionSolve provides you with a well-defined interface and a well-defined methodology for creating user subroutines.
    - Driver Subroutines
      Driver subroutines are user-written subroutines that allow you to create and execute your own types of analyses. These analyses are typically composed of level analyses that are provided to you by MotionSolve.
    - Utility Subroutines
      Utility subroutines are functions that are useful when writing user-written subroutines.
    - Modeling Subroutines
      Modeling subroutines are user-written subroutines that allow you define the run-time behavior of a modeling element via a user subroutine.
      - ARYSUB
        ModelingCalculates the values for a user-defined input array element.
      - CFFSUB
        ModelingUsed to calculate friction forces for the Force_Contact element.
      - CNFSUB
        ModelingUsed to calculate normal forces for the Force_Contact element.
      - CONTACTPOST
        ModelingExtract body contact results.
      - COUSUB/COUXX/COUXX2
        ModelingUsed to specify a user coupler element.
      - CURSUB
        ModelingUsed to specify a user defined curve element and its derivatives for a reference curve element. User defined curves are typically used in conjunction with point-to-curve, curve-to-curve, and curve-to-surface constraints.
      - DIFSUB
        ModelingUsed to calculate a differential equation value for a control DIFF entity.
      - DMPSUB
        ModelingUsed to compute a custom modal damping ratio for a flexible body.
      - FIESUB
        ModelingA field subroutine is used to calculate the six component forces/torques and their derivatives for a force field entity.
      - GCOSUB
        ModelingCalculates a constraint defined using a Constraint_General element. Such constraints are typically used in conjunction with defining a broad range of holonomic and non-holonomic constraints. A typical example is the so called "curve of pursuit" constraint, where one particle is chasing another particle.
      - GFOSUB
        ModelingUsed to calculate the six component forces and torques for a general force entity.
      - GRASUB
        ModelingCalculates node positions for a user-defined graphics element.
      - GSESUB/GSEXX/GSEXU/GSEYX/GSEYU
        ModelingUsed to represent any generic system that has defined inputs, internal states, and outputs.
      - MARKER_READ
        ModelingInputs a user-defined marker element.
      - MATRIX_READ
        ModelingInputs a user-defined marker element.
      - MESSAGE_SUB
        Utility/Data Access SubroutineA subroutine called by MotionSolve to generate messages.
      - MFOSUB
        ModelingCalculate the scale factor for a modal force entity. Alternatively, you may also use MFOSUB to calculate and return the distributed load shape on the flexible body.
      - MOTSUB
        ModelingUsed to compute displacement, velocity, or acceleration for a Motion entity.
      - PINSUB
        ModelingCreates user-defined input to a control plant.
      - POST_SUB
        ModelingUsed to extract MotionSolve results.
      - POST_SUBS
        ModelingUsed to extract MotionSolve results.
      - POUTSUB
        ModelingRetrieves output from a control plant.
      - PTdSFSUB
        ModelingUsed to compute normal and friction force for a Force_PTdSF entity.
      - RELSUB
        ModelingUsed to reload user data written using SAVSUB.
      - REQSUB
        ModelingUsed to compute outputs for a user-defined request element. This is typically done when the output quantities are too complicated to be expressed as explicit functions.
      - SAVSUB
        ModelingSAVSUB saves user-data written data to be loaded using RELSUB.
      - SENSUB/SEVSUB
        ModelingUsed to compute/evaluate the value for a sensor element. SENSUB can detect an event, while SEVSUB is used to return the scalar value computed when the event defined by the sensor occurs.
      - SFOSUB
        ModelingUsed to compute the force value for a force entity.
      - SPARSESUB
        ModelingSolves the linear system of equations of each Newton iteration. The linear system is defined as $J ∆ q = - F (q, \dot{q}, \ddot{q}, t)$ , where $J$ is a sparse, unsymmetrical Jacobian matrix, $∆ q$ is the difference in states, and $- F (q, \dot{q}, \ddot{q}, t)$ is the right-hand side.
      - SPLINE_READ
        ModelingUsed to read x, y, and optionally z, data from a file for use with a Reference_Spline element.
      - STRING_READ
        ModelingInputs a user-defined string.
      - SURSUB
        ModelingUsed to specify a user-defined surface element and its derivatives for a reference surface element.
      - TUNSUB
        ModelingThe TUNSUB allows you to modify certain solver parameters during a simulation.
      - UCOSUB
        ModelingCalculates a constraint value and its derivatives for a user defined constraint element. User- defined constraints are typically used in conjunction to define a broad range of holonomic and non-holonomic constraints. A typical example is the so called "curve of pursuit" constraint, where one particle is chasing another particle.
      - VARSUB
        ModelingCalculates an algebraic value for a user defined variable element.
      - VFOSUB
        ModelingComputes the translational force components for a force vector entity.
      - VTOSUB
        ModelingComputes the rotational force components for a torque only vector entity.
      - YFOSUB
        ModelingCalculates the vector force/torque between two bodies from a general state equations.
- ADM/ACF Entities
- NLFE Statements
- msolve API Statements

Modeling Subroutines

Modeling subroutines are user-written subroutines that allow you define the run-time behavior of a modeling element via a user subroutine.

Modeling subroutines are used by various modeling entities, like forces and motions, and other elements directly defined in your multibody mechanical system.

These are listed below with a brief description of each. See each subroutine's documentation for more details on its use.