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MotionSolve User Guide
MotionSolve is a system level, multibody solver that is based on the principles of mechanics.
Model Systems
Model Forces
The term force generically refers to both applied forces and applied moments.

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Overview
MotionSolve^® is an integrated solution to analyze, evaluate, and optimize the performance of multibody systems.
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Discover MotionSolve functionality with interactive tutorials.
MotionSolve User Guide
MotionSolve is a system level, multibody solver that is based on the principles of mechanics.
- Introduction to MotionSolve
- Platform Support, Recommended Hardware, and Licensing
- Run MotionSolve
- Model Systems
  - Model Mechanical Systems
    A mechanical system can be thought of as being composed of a set of basic mechanical entities that interact with each other by exchanging energy or information in well-defined ways. For example, a simple pendulum system is composed of a rigid body connected to the ground by a revolute joint. MotionSolve provides physics-based, mathematical models of such entities and ways to assemble them into realistic models of complex mechanical systems. It then lets you simulate your models to gain insight into their behavior.
  - Graphical User Interfaces - MotionView and HyperMesh
    Two graphical user interfaces (GUIs) are available in Altair HyperWorks to build MotionSolve models: MotionView and HyperMesh.
  - Model Bodies
    Bodies are the only modeling elements that explicitly capture mass and inertia effects.
  - Model Constraints
    Constraints arise when the motion of a body is restricted by connections to other bodies.
  - Model Forces
    The term force generically refers to both applied forces and applied moments.
  - Model Contacts
    MotionSolve provides a very sophisticated contact modeling capability that can handle complex contact scenarios between rigid bodies.
  - Model Sensors
    Sensors help you detect events of interest in a simulation as well as respond to the event in various ways.
  - Model Feedback Control Systems
  - Post-process Elements
- Model Simulations
- Visualize Results - Animation and Request Plots
- Couple MotionSolve with Other Software
- Customization Capabilities
- Analysis Tips
- NLFE Bodies Introduction
- User Subroutines in MotionSolve
- msolve API
- MotionSolve Verification Manual
- MotionSolve Optimization Guide
- MotionSolve Environment Variables
- References
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.

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Model Forces

The term force generically refers to both applied forces and applied moments.

Force elements are commonly used for:

Modeling compliant connections.
Contact between bodies.
Modeling the effects of the environment on the system.

Examples of compliant connections include springs, dampers, and bushings. For the purpose of vehicle handling studies, tires are modeled as compliant force models. Examples of environmental effects include gravity (which may or may not be constant), aerodynamic forces, and hydrodynamic pressure.

Force elements may be defined as arbitrary functions of any state variables in the system and time. The functional form of the force description may be an interpolated curve, an analytical expression, or a user-defined subroutine in C++, C, or Fortran. Vector forces can be specified by their components in arbitrary reference frames. Scalar forces act along the line connecting the origins of markers.

This is an extremely open and powerful capability in MotionSolve that enables you to easily model most of the forces occurring mechanically. However, when modeling a force, you must make sure that the force is, at the very minimum, continuous. It is better if the forcing functions are smooth (without kinks) and do not change dramatically with respect to the independent variables (frequency content is not very high). If the force has an undamped, high frequency content, the integrator will attempt to follow it and therefore take smaller step sizes, resulting in slow run times.