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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.
Utility Subroutines
Utility subroutines are functions that are useful when writing user-written subroutines.
Data Access Subroutines
Data Access subroutines are built-in subroutines provided by MotionSolve that allow a user-written subroutine to access model parameter or state information.
STEP5
Utility/GeneralEvaluates a STEP function via a polynomial of the fifth order approximation.

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What's New
View new features for MotionSolve 2024.1.
Overview
MotionSolve^® is an integrated solution to analyze, evaluate, and optimize the performance of multibody systems.
Tutorials
Discover MotionSolve functionality with interactive tutorials.
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.
      - Analysis Control Subroutines
        Analysis control subroutines are built-in subroutines provided by MotionSolve that allow a user-written subroutine to perform various types of analysis, generate output and modify the model defined in the XML input file.
      - Data Access Subroutines
        Data Access subroutines are built-in subroutines provided by MotionSolve that allow a user-written subroutine to access model parameter or state information.
        ADD_MASS_PROPERTY
        Utility/Data Access SubroutineReturns aggregate mass data for a set of bodies.
        AKISPL
        Utility/Data Access SubroutineUses a spline fitting method to return the interpolated value or 1st/2nd derivative of the interpolated value for a Reference_Spline element.
        BISTOP
        Utility/GeneralEvaluates a BISTOP function (gap element).
        BODY_MASS_PROPERTY
        Utility/Data Access SubroutineReturns the mass, c.g., and inertia tensor for a body or the entire model.
        CHEBY
        Utility/GeneralEvaluates a CHEBYSHEV polynomial function.
        CUBSPL
        Utility/Data Access SubroutineUses a spline fitting method to return the interpolated value or 1st/2nd derivative of the interpolated value for a Reference_Spline element.
        CUSFNC
        Utility/Data Access SubroutineThe CUSFNC utility subroutine obtains a scalar output from a custom defined function in MotionSolve. The custom function must already be defined using the MotionSolve custom mapping file.
        ERRMES
        Utility/Data Access SubroutineOutputs error messages during MotionSolve execution.
        FITSPL
        Utility/Data Access SubroutineUses a spline fitting method to return the interpolated value or 1st/2nd derivative of the interpolated value for a Reference_Spline element.
        FMIN_SLSQP
        Utility/Data Access SubroutineSLSQP optimizer is a sequential least squares programming algorithm for nonlinear, constrained gradient-based optimization. It supports both inequality and equality constraints.
        FORCOS
        Utility/GeneralEvaluates a Fourier Cosine. A Fourier Cosine series is a collapsed version of a Fourier series, where the factors multiplying the SIN() terms are all zero.
        FORSIN
        Utility/GeneralEvaluates a Fourier Sine. A Fourier Sine series is a collapsed version of a Fourier series where the factors multiplying the COS() terms are all zero.
        GET_CONTACT_POST
        Utility/Data Access SubroutineExtract body contact results.
        GET_FULL_MATRIX_DATA
        Utility/Data Access SubroutineReturns the data from a full Reference_Matrix element. There is a separate function for the sparse Reference_Matrix element called GET_SPARSE_MATRIX_DATA.
        GET_GRAVITY
        Utility/Data Access SubroutineReturns the gravitational acceleration specified using Force_Gravity modeling element.
        GET_MATRIX_INFO
        Utility/Data Access SubroutineReturns information about a Reference_Matrix element.
        GET_NCONTACTS
        Utility/Data Access SubroutineExtract the number of body contacts during a simulation.
        GET_POST_STATES
        Utility/Data Access SubroutineThis subroutine extracts state variables in a MotionSolve model.
        GET_SPARSE_MATRIX_DATA
        Utility/Data Access SubroutineReturns the data from a sparse Reference_Matrix element.
        GET_STEP_INFO
        Utility/Data Access SubroutineThis subroutine returns information about the current simulation step in a MotionSolve simulation.
        GETCPU
        Utility/Data Access SubroutineRetrieves the CPU time during MotionSolve execution.
        GETIDLIST
        Utility/Data Access SubroutineThe GETIDLIST utility subroutine returns the IDs of model entities of a particular type.
        GETINM
        Utility/Data Access SubroutineRetrieves the mode that MotionSolve is in.
        GETINT
        Utility/Data Access SubroutineRetrieves the integrator type during a MotionSolve run.
        GETMOD
        Utility/Data Access SubroutineRetrieves the analysis mode during MotionSolve execution.
        GETNUMID
        Utility/Data Access SubroutineThe GETNUMID utility subroutine returns the total number of model entities of a particular type.
        GETSLV
        Utility/Data Access SubroutineRetrieves the active solver.
        GETSTM
        Utility/Data Access SubroutineRetrieves the current MotionSolve simulation time.
        GETVER
        Utility/Data Access SubroutineRetrieves the MotionSolve version number.
        GTARAY
        Utility/Data Access SubroutineRetrieves values stored in the IC Reference_Array entities.
        GTCMAT
        Utility/Data Access SubroutineGTCMAT calculates the compliance matrix between "N" REFERENCE_MARKERs in a MotionSolve model.
        GTCURV
        Utility/Data Access SubroutineEvaluate a B-spline or user-written curve created with the Reference_ParamCurve entity.
        GTINAM
        Utility/Data Access SubroutineReturns the base name of the MotionSolve output MRF file.
        GTONAM
        Utility/Data Access SubroutineReturns the base-name of the MotionSolve output files.
        GTSTRG
        Utility/Data Access SubroutineRetrieves values stored in a Reference_String entity.
        GTUNTS
        Utility/Data Access SubroutineRetrieves unit information from MotionSolve.
        HAVSIN
        Utility/GeneralEvaluates a Haversine function.
        IMPACT
        Utility/GeneralModels a contact force or collision phenomena.
        ISTRNG
        Utility/GeneralUsed for integer-to-character conversions and receives an integer number and returns the corresponding string.
        LINSPL
        Utility/Data Access SubroutineUses a spline fitting method to return the interpolated value or 1st/2nd derivative of the interpolated value for a Reference_Spline element.
        MODFNC
        Utility/Data Access SubroutineRetrieves the model data as specified in the XML solver input file.
        MODINF
        Utility/Data Access SubroutineRetrieves the mode numbers and the corresponding mode frequencies of a Body_Flexible element.
        MODSET
        Utility/Data Access SubroutineThe MODSET subroutine accesses and modifies the model data as specified in the MotionSolve XML input file.
        NMODES
        Utility/Data Access SubroutineRetrieves the number of modal generalized coordinates corresponding to a Body_Flexible element.
        POLY
        Utility/GeneralEvaluates a generic polynomial. A polynomial is a mathematical expression defined by the sum of the powers of a variable, multiplied by coefficients.
        PUT_MARKER
        Utility/SetupUsed to set the marker position and orientation in conjunction with MARKER_READ.
        PUT_SPLINE
        Utility/SetupUsed in conjunction with SPLINE_READ. It is used to store data read by SPLINE_READ within MotionSolve.
        QUISPL
        Utility/Data Access SubroutineUses a spline fitting method to return the interpolated value or 1st/2nd derivative of the interpolated value for a Reference_Spline element.
        RCNVRT
        Utility/GeneralConverts rotational coordinates between the various supported representations.
        RELOAD_MODEL
        Utility/Data Access SubroutineRELOAD_MODEL is used to load a model defined in a MotionSolve XML input file into memory and make it the current model. This subroutine can only be called from a user-written CONSUB.
        RELPAR
        Utility/Data Access SubroutineRetrieves the user-defined work array data.
        RSTRNG
        Utility/GeneralUsed for double precision to character conversion. It receives a double precision variable and returns the corresponding string.
        SAVE_MODEL
        Utility/Data Access SubroutineSAVE_MODEL is used to save the current model from a user-written CONSUB.
        SAVPAR
        Utility/Data Access SubroutineSaves the user-defined work array data.
        SET_ATTRIBUTE
        Utility/Data Access SubroutineThis subroutine modifies the attribute accessed by the last MODFNC or MODSET call.
        SET_DAE_ERROR
        Utility/Data Access SubroutineThe SET_DAE_ERROR utility subroutine sets the integration error tolerance for the DAE integrator DSTIFF.
        SET_DAE_HMAX
        Utility/Data Access SubroutineThe SET_DAE_HMAX utility subroutine sets the maximum step size that the DAE integrator DSTIFF is allowed to take.
        SET_DISCRETE_INTERFACE
        Utility/SetupThe SET_DISCRETE_INTERFACE subroutine tells the solver to call the user-written subroutine discretely at successful integration steps.
        SET_GSE_ALGEBRAIC_EQN
        The SET_GSE_ ALGEBRAIC_EQN subroutine is used with GSESUB to specify the implicit, algebraic equation.
        SET_GSE_NONZERO_ENTRY
        Utility/SetupThe SET_GSE_NONZERO_ENTRY subroutine is used with GSESUB to specify the nonzero entries of the Jacobian matrix indicated by mat_type.
        SHF
        Utility/GeneralEvaluates a Simple Harmonic.
        STEP
        Utility/GeneralEvaluates a STEP function via a cubic polynomial approximation.
        STEP5
        Utility/GeneralEvaluates a STEP function via a polynomial of the fifth order approximation.
        STR2DBLARY
        Utility/Data Access SubroutineConverts string data into double or double array.
        STR2INTARY
        Utility/Data Access SubroutineConverts string data into integer or integer array.
        SUBTRACT_MASS_PROPERTY
        Utility/Data Access SubroutineReturns mass data for one set of bodies minus another set of bodies.
        SYSARY
        Utility/Data Access SubroutineObtains various system states, for example, Displacement and Velocity, and makes them available to user-defined subroutines. SYSARY should be called with the appropriate input arguments (listed below) and it returns the corresponding system state.
        SYSFNC
        Utility/Data Access SubroutineThe SYSFNC utility subroutine allows you to query MotionSolve for a single system state such as displacement, velocity, and force, inside a user subroutine. SYSFNC should be called with the appropriate input argument (listed below) and it returns the corresponding system state.
        TCNVRT
        Utility/GeneralConverts translational coordinates between the various supported representations.
        TIMGET
        Utility/Data Access SubroutineRetrieves the time corresponding to the last successful simulations step.
        UCOMAR
        Utility/Data Access SubroutineUsed in conjunction with UCOSUB to define the marker states used in a user-defined constraint.
        UCOVAR
        Utility/Data Access SubroutineUsed in conjunction with UCOSUB to define the part states in a user-defined constraint.
        USRMES
        Utility/Data Access SubroutineThe USRMES utility subroutine allows you to output custom messages during MotionSolve execution.
    - Modeling Subroutines
      Modeling subroutines are user-written subroutines that allow you define the run-time behavior of a modeling element via a user subroutine.
- ADM/ACF Entities
- NLFE Statements
- msolve API Statements

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STEP5

Utility/GeneralEvaluates a STEP function via a polynomial of the fifth order approximation.

Use

This function can be called by any user-defined subroutine.

Format

Fortran Calling Syntax: CALL STEP5 (X, X0, H0, X1, H1, IORD, VALUE, ERRFLG)
C/C++ Calling Syntax: c_step5(x, x0, h0, x1, h1, iord, value, errflg)
Python Calling Syntax: [value, errflg] = py_step5(x, x0, h0, x1, h1, iord)
MATLAB Calling Syntax: [value, errflg] = m_step5(x, x0, h0, x1, h1, iord)

Attributes

X: [double precision]; The independent variable. For example, to specify time as the independent variable, specify X as TIME.
X0: [double precision]; The X value at which the STEP5 function begins.
H0: [double precision]; The value of the STEP5 function at X0
X1: [double precision]; The X value at which the STEP5 function ends.
H1: [double precision]; The value of the STEP5 function at X1.
IORD: [integer]; The order of the derivative that STEP5 has to return. Order can be 0, 1 or 2.

Output

Value: [integer]; A value that the subroutine returns.
Errflg: [logical]; A (true or false) variable that STEP5 returns to the calling subroutine. If STEP5 detects an error while calling the subroutine, it sets the error flag to true.